Transparent oxide deposition is a key component in manufacturing modern optoelectronic devices, such as touch screens, photovoltaics, and smart windows. Thin-film transparent oxides are important building blocks in these devices for their low-temperature processing, flexibility, and exceptional electrical performance. And with the help of our HEX series, transparent oxide deposition is within your organisation’s reach. Fundamentals of Transparent Oxide Deposition Several deposition processes for transparent oxides have arisen in recent decades, but what exactly is transparent oxide deposition, and what are its uses? What Is Transparent Oxide Deposition? Transparent oxide deposition is the process of creating transparent conductive oxides (TCOs) [1] by depositing thin oxide films onto target materials. TCOs are electrically conductive materials with low light absorption, making them transparent. Precise, reliable deposition is necessary to fabricate TCOs for use within optoelectronic cells. The Role of Transparent Oxides in Technology Transparent oxides have functional uses across a wide range of technologies, namely optoelectronic devices, such as: LEDs Displays Lasers Optical fibres Societally, transparent oxides play a significant role in producing energy-efficient devices like solar cells. These cells use a renewable energy source in place of non-renewable natural gas, reducing carbon emissions. Advantages of Using PVD for Transparent Oxide Deposition While there are several thin film oxide deposition techniques, transparent oxides prepared with physical vapour deposition (PVD) techniques lead to high electron mobility and low resistivity, giving the TCOs the ideal properties for sensitive optoelectronic applications like heterojunction solar cells. Using the HEX series to conduct this advanced oxide film deposition process allows for ultimate precision and versatility for other types of PVD applications. The Science Behind Transparent Oxides Why are transparent oxides so pivotal within modern optoelectronic applications? They offer the ideal physical properties for energy-efficient electrical technologies. Properties of Transparent Oxides Transparent oxides have unique optical and electrical properties that make them indispensable within optoelectronics. They showcase efficient electrical performance, low-temperature processing, and device flexibility. Additionally, transparent oxide coating technologies reflect infrared and near-infrared wavelengths, have high optical transmission at visible wavelengths, and showcase electrical conductivity similar to that of metals. As a result, they can be used in place of conductive metals in various applications. Selecting Materials for Transparent Oxide Deposition Three main oxides stand out as appropriate candidates for oxide deposition: Zinc oxide Tin oxide Copper aluminium oxide These materials are highly conductive, transparent, and durable and respond well to various transparent coating deposition methods. Researchers are still uncovering other materials that could offer even better conductivity. For instance, researchers have recently found that the optimised Sn-doped In2O3 (ITO) has ideal properties for TCO materials because of its high transmittance, electrical conductivity, bandgap, and mobility. Some materials are also more suitable for certain applications. For example, ITO is an ideal material for transparent oxide deposition for use within silicon heterojunction solar cells. The Transparent Oxide Deposition Process With the HEX Series At Korvus Technology, we’re transforming the accessibility of thin-film deposition within manufacturing, one HEX series at a time. Our systems use physical vapour deposition to bring complex manufacturing processes like transparent oxide deposition to your lab. Overview of the Deposition Process The transparent oxide deposition process involves depositing thin films of metal oxides onto target materials, creating transparent oxides good for optoelectronics. The HEX series of thin deposition systems facilitates the creation of high-quality transparent oxides through physical vapour deposition. At a basic level, this process deposits a transparent conductive oxide onto a surface, creating a clear, electronically conductive coating. It uses low-temperature evaporation to stabilise the organic materials within the deposition process. The same HEX series technology can produce thin film transistors and other types of coatings. Korvus Technology’s HEX series offers innovative solutions for precise and targeted transparent oxide deposition, expanding the functional uses of this technology. Through the HEX series, your organisation can completely customise the oxide layer deposition for transparency control. The HEX series’ deposition process is also highly efficient, streamlining the production of transparent conductive oxides while ensuring the highest-quality results. Real-World Applications of Transparent Oxide Deposition Transparent conductive oxides have numerous modern applications. Researchers continue to develop new uses for these clear, conductive, and flexible materials. Enhancing Solar Cells First, transparent oxide deposition is crucial to the production of efficient and optimised solar cells. The coatings on thin film solar cells must be transparent like glass while being highly conductive like metal. TCOs offer the best of both worlds, with properties that allow light to enter the cell, convert that light into energy, and collect the converted energy for output. Similarly, TCOs are pivotal in the technology behind “smart windows,” which regulate the solar flux entering a car or building by transitioning from clear to frosted depending on the season and desired interior temperature. Display Technologies TCOs are widely used within modern flat-panel displays. The transparency of the coating makes for a near-invisible conductive overlay ideal for crisp, high-definition electronic displays. We will also see transparent oxide deposition play a vital role in the development of next-generation smart devices and advanced flexible optoelectronics. Many touch screens already use TCOs to create reactive yet high-resolution displays. Transparent Oxide Deposition and Future Innovations Transparent oxide deposition is the future of optoelectronic manufacturing, and Korvus Technology is paving the way with the high-quality, accessible, user-friendly HEX series. These systems use advanced technology to facilitate high-quality transparent oxide deposition through reliable PVD methods. Even better, they are usable within a range of industries, fostering important innovations in many fields. Explore our Benchtop PVD system from Korvus Technology and learn how this system can seamlessly integrate into your research and manufacturing processes. Korvus Technology is ready to support your projects and help you select the right system for your needs. References [1] Materion. Transparent conductive oxide films. https://materion.com/-/media/files/advanced-materials-group/me/technicalpapers/transparentconductiveoxidethinfilms.pdf, Accessed on 14 February 2024. [2] Ohta, Hiromichi, and Hideo Hosono. (2004). Transparent oxide optoelectronics. MaterialsToday 7, 6. https://doi.org/10.1016/S1369-7021(04)00288-3 [3] Macco, B., Wu, Y., Vanhemel, D., et al. (2014). High mobility In2O3:H transparent conductive oxides prepared by atomic layer deposition and solid phase crystallization. Rapid research Letters 8, 70. https://doi.org/10.1002/pssr.201409426 [4] Natu, Krutika, Laad, Meena, et al. (2023). Transparent and flexible zinc oxide-based thin-film diodes and thin-film transistors: A review. Journal of Applied Physics, 134, 19. https://doi.org/10.1063/5.0169308 [5] K Gesheva et al. (2016). Technologies for deposition of transition metal oxide thin films: application as functional layers in “Smart windows” and photocatalytic systems. Journal of Physics: Conference Series. doi:10.1088/1742-6596/682/1/012011 [6] Ma, CH., Chen, EL., Lai, YH. et al. (2020). Flexible transparent heteroepitaxial conducting oxide with mobility exceeding 100 cm2 V−1 s−1 at room temperature. NPG Asia Mater 12, 70. https://doi.org/10.1038/s41427-020-00251-2

A myriad of components drive the electronics industry, including a well-known, integral part called the thin film resistor. A thin film resistor can be manufactured in miniscule sizes and to extremely exacting specifications, making it a ubiquitous part in electronic devices. In this article, we’ll explain the details behind these components; from their structure, different types of resistors and the thin film deposition process behind them. Understanding Thin Film Resistors The purpose of thin film and chip resistors is to restrict electrical current that can flow through a circuit. “Thin” refers to the fact that the resistive element is deposited as a thin film on a glass or ceramic base of only a few nanometres to microns thick. These components are favoured across electronic, instrumentation, medical devices, and automotive applications, where accurate and stable resistance values and voltage control are essential performance elements. What Is a Thin Film Resistor? A thin film resistor is a component designed to provide a specific resistance to the flow of electric current in a circuit. It earned its name thanks to the thin film of resistive material that gets deposited onto an insulating substrate, which is what ultimately forms the resistor. This thin film-resistive material is typically made of nichrome or tantalum. The underlying purpose is to resist or oppose the flow of current that passes through it. The Construction Process of Thin Film Resistors Unlike some other film resistors, which are coated with a resistive paste screen on a ceramic body and the resistance values get adjusted with a rudimentary trimming cut where all the current passes through, a thin film resistor undergoes a much more complex manufacturing process utilising a uniform metallic film. The manufacturing process includes deposition of a resistive metallic layer, which is extremely stable and serves to calibrate the resistance value. Further, the laser trimming process is more precise and uniform, allowing more evenly distributed current. A deposition technique that is used in the manufacture of both thin film and thin film chip resistors is called physical vapour deposition (PVD); it is a form of vacuum deposition where material is vaporised and then transported to the substrate where it then ultimately condenses to a thin film. The Evolution of Thin Film Resistors Resistors have been around since the early days of electronics, though they were very limited in terms of precision and stability. By the 1950s, however, thin film technology had been adopted as an alternative to bulkier wire-round resistors. As the microelectronics field emerged in the 1970s, thin film deposition techniques began to evolve, and the 1970s saw the advent of higher performance materials. Some of the most transformative inventions were the use of integrated circuits and photolithography techniques. Ongoing advancements continue to be the norm thanks to continuing pressures of miniaturisation, materials innovation, and automation. The Anatomy of a Thin Film Resistor Various components contribute to the functionality and performance of a thin film resistor. Components of Resistors The following components can be found in a thin film resistor: Substrate Thin film resistive layer Conductive terminals Passivation resistive layer Bonding pads Types of Resistors There are several types of resistors, including but not limited to the following: Fixed carbon and wire-wound resistors Variable resistors Specialised film and chip resistors Network resistors Variable resistors Surface mount resistors Power resistors The most notable characteristics of the thin film resistor family are high tolerance levels, a lower temperature coefficient, and capabilities for higher-rated power. Thin films also boast lower parasitic inductance and lower capacitance. A thin film resistor has a wider array of industry applications compared to other film resistors. While thin film varieties are 0.1 microns thick, other film resistors can be thicker by a factor of 1,000. This difference between a thin and thick film resistor affects accuracy and the acceptable temperature range, so a thin film resistor is more commonly used in precision applications. The Deposition Process Behind Thin Film Resistor Production Without question, the deposition process plays an essential role in the production of a thin film resistor because it is determinant of its performance characteristics and reliability. The Deposition Process The deposition process includes a long list of detailed steps: Substrate preparation Cleaning and surface treatment Application of a masking layer Deposition of thin film through physical vapor deposition or chemical vapor deposition Heat treatment Etching Application of a passivation layer Quality control and testing Semiconductor Materials in Thin Film Resistors The choice of semiconductor materials is also important, as the selection criteria involves evaluating their specific electrical properties, stability, cost, and overall compatibility with the deposition process. Options for semiconductor materials in thin films include: Nichrome Tantalum Nitride Silicon Aluminium Platinum Gold Manufacturing Thin Film Resistors With Korvus Technology The HEX Series from Korvus Technology is a unique thin film deposition system for creating thin film resistors. If you are looking to expand your capabilities, we invite you to contact us and explore our custom solutions. We will be happy to discuss your project and help you identify which system is right for you.

Suppose you’d like to vaporise a substance, such as metal or glass, and apply that substance as a coating to another surface. Decades ago, such a feat would have been impossible. Today, you can accomplish this task using a technique called ionised physical vapour deposition, or ionised PVD. How Ionised PVD Redefines Material Manufacturing Ionised PVD enables material manufacturers to create advanced materials with superior properties. For example, a manufacturer wants to create stronger food packaging that can protect contents for a longer period. Using ionised PVD, the manufacturer can vaporise aluminium and apply a very thin coat of the metal to the inside of the packaging. This is just one example of the many applications of ionised PVD. Overview of the Mechanisms Driving High-Density Material Formation Materials manufacturers can accomplish PVD using a variety of ionised coating techniques. One of the most common thin-film deposition methods is called sputtering. During this PVD coating process, the target material is bombarded by high-energy ions that emit (sputter) ions, which are then deposited onto the material’s surface to produce a coating. Manufacturers can use either a DC (direct current) or RF (radiofrequency) power source to accomplish this PVD surface treatment. DC is preferred because it’s relatively inexpensive and quite fast. However, it only works for conductive materials, such as metals. Manufacturers of non-conductive materials, like ceramics and glass, must use RF. Ionised PVD’s Role in Advancing Next-Generation Technologies A brief tour of your home will likely reveal many items made with ionised PVD. Your television, computer, phone, and even that crisps bag in your kitchen were all likely made using PVD processes. Materials manufacturers have only scratched the surface of what’s possible with PVD. In the automotive industry, manufacturers use PVD to reduce oxidation and wear and tear on vehicle parts. Electronics manufacturers can use PVD to create lightweight anisotropic glasses for organic semiconductors. The medical equipment industry uses PVD to boost the wear resistance of surgical cutting tools. Advantages of Ionised PVD Over Conventional Deposition Methods Ionised PVD boasts several advantages over conventional deposition methods. It offers a low level of impurity and good uniformity, perfect if you wish to create materials with very little variance. It also offers excellent density, a high deposition rate, and the highest level of scalability. Thus, ionised PVD is a good choice if you’d like to automate PVD processes. Ionised PVD is best for ultra-thin films that require superior adhesive properties. It’s also ideal if you need to create insulating or metal coatings with specific electrical or optical properties. Redefining Material Manufacturing With Ionised PVD Imagine windows that change colours when touched by the sun’s rays or wearable devices that can fall 50+ feet in water and come out unscathed. Today’s materials manufacturers can accomplish these feats and much more with ionised PVD. Using ionised PVD, manufacturers create materials with surprising new properties. They produce magnetic walls and glass, nearly unbreakable parts, and metals that never rust. Such properties are highly valued in the aerospace, automotive, and medical industries. Ionised PVD’s Influence on the Frontier of High-Density Material Research High-density materials, such as osmium, platinum, and iridium, can be challenging to work with. Platinum has various applications, including dental equipment, computer hard drives, and turbine blades. Iridium and osmium are used for compass bearings, electrical contacts, and pen tips. By taking advantage of ionised PVD, materials manufacturers can apply these and other high-density materials in new and exciting ways. For example, they can create solid-state thin-film batteries that never leak and last for many years. The Science Behind Ionised PVD How exactly does ionised PVD work? Suppose you have a target material from which you wish to extract particles. To “convince” the particles to leave the material’s surface, you must hit them with a high-pressure stream of ions. By doing this, the particles will leave the surface and jump randomly in the chamber, eventually settling on the substrate as desired. Ionised PVD’s Eco-Friendly Contribution Materials manufacturers can use ionised PVD to reduce waste and lower their carbon footprint. That’s because PVD is a highly efficient process. During PVD, virtually no unwanted particles get into the soil, water, or air. PVD also has several green applications. For example, it’s used to make EV batteries for electric vehicles. Leveraging Ionised PVD for Advanced Material Production To conclude, ionised PVD is an excellent choice if you wish to create materials with exciting and revolutionary properties. It offers superb uniformity, very low impurity, and extremely high-quality film. Additionally, the process emits very little waste, which is certainly appealing if you care about efficiency. If you want to learn more about ionised PVD technology or our HEX Series modular film deposition systems, contact us at Korvus Technology today. References [1] U. Helmersson, M. Lattemann, J. Bohlmark, A. Ehiasarian (2006). PVD or CVD, Thin Solid Films, 513 (1-2): 1-24, DOI: 10.1016/j.tsf.2006.03.033 [2] A. Wendt (2000): High-Density Plasma Sources, Thin Films, 9-35, DOI: 10.1016/S1079-4050(00)80004-6 [3] J.T. Gudmundsson, A. Anders, A. Keudell (2022). Foundations of Physical Vapor Deposition With Plasma Assistance, Plasma Sources Science and Technology, 31:8, DOI: 10.1088/1361-6595/ac7f53 [4] N. Song, S.Deng (2022). Thin Film Deposition Technologies and Application in Photovoltaics, Thin Films: Deposition Methods and Applications, DOI: 10.5772/intechopen.108026

PVD, or physical vapour deposition, is a technique for applying very thin coatings to materials such as glass, metals, plastics, computer chips, and even food packaging. During the PVD process, you may wish to apply a bias to a substrate. Substrate biasing in PVD is a technique that creates a localised plasma on the surface of the substrate. Substrate biasing does require some extra preparation time; however, if you require a perfectly clean substrate, it is well worth the effort. Below, you will learn everything you need to know about substrate biasing in PVD processes. Importance of Substrate Preparation Substrate biasing has many benefits. The technique allows you to clean, oxidise, or etch a substrate in preparation for a film. Biasing provides gentle ion bombardment before or during deposition to improve adhesion, film density, and material adhesion. Next, we will discuss the importance of substrate preparation in more detail. Criticality of Substrate Preparation If you have ever experienced poor results during the deposition process, an inadequately prepared substrate may be to blame. Without proper preparation, materials may not adhere to the surface of the substrate as efficient as you might like. Should this happen, you must restart the thin-film deposition process, potentially wasting valuable time and materials. To help with this substrate biasing can improve the strength of the substrate and the overall properties of the film. Bias is measured using voltage. The larger the bias voltage, the higher endurance and film strength are. A stronger substrate is capable of withstanding even the most demanding PVD processes, such as plasma-enhanced PVD. Additionally, biasing can help to ensure that devices last for their expected lifespans. Poor films can increase the stress on a device, leading to reduced performance and degradation over time. This could have a negative effect on the manner in which consumers view your company’s products. Thus, substrate preparation is critical to avoid damage to your company’s reputation. Effect of Surface Cleanliness No matter how careful you are, substrates will naturally accumulate contaminants that can affect their performance. Contaminants may include: Grease from touching the substrate with non-gloved hands Wax from cutting oils Airborne bacteria Plasticisers that come from the container in which the substrate is shipped Cleanliness affects the nucleation and growth of thin films. If your substrates are not perfectly clean, you may experience problems with adhesion and thin film growth. Proper cleaning ensures that materials adhere to the substrate properly. Substrate Cleaning Techniques There are several options for substrate cleaning: chemical cleaning, physical cleaning, and mechanical cleaning. Each option has advantages and disadvantages. We provide an overview of each technique for substrate biasing in PVD below. Chemical Cleaning Chemical cleaning, as the name implies, is a process that relies on various chemicals to clean the surface of a substrate. One advantage of chemical cleaning is gentleness. You do not risk damaging the substrate as you would with physical or mechanical cleaning. However, not all chemicals can remove all contaminants. You must take care to choose the proper chemical formulation. Reactive ion etching (RIE) is a popular cleaning technique because it is the simplest process for providing directional etching. It uses a combination of physical and chemical processes to remove material from substrates. Acid etching is another option. It involves the selective removal of material from a substrate using a chemical solution. Solvent cleaning is a preferred method because it is relatively simple. Commonly used solvents include acetone, xylene, and toluene. Physical Cleaning Physical cleaning options include plasma cleaning and ion bombardment. These processes are highly regarded for their ability to remove surface oxides and activate the substrate surface. However, they require advanced knowledge of chemistry and specialised equipment that not everyone can access. Mechanical Cleaning Mechanical cleaning is ideal for removing particulate matter and roughening surfaces to improve adhesion. Mechanical cleaning may not be ideal for very delicate substrates. Brushing and sandblasting are two mechanical cleaning techniques commonly used for substrates. Ultrasonic cleaning is another. It involves running substrates through an ultrasonic cleaning line and then rinsing them with deionised (DI) water. Substrate Oxidation Oxidation is a process that allows you to grow an oxide on certain substrates, an example of this would be the growth of a silicon oxide film on the surface of a silicon substrate. This technique allows precise control over the thickness of the oxide while producing highly adherent, dense, and uniform oxide with very good electrical properties. There are two options for oxidation: thermal oxidation and plasma oxidation. Learn the differences between these techniques below. Thermal Oxidation Thermal oxidation forces an oxidising agent to diffuse into the wafer and react with it. Most commonly, thermal oxidation is used to produce a layer of silicon dioxide on silicon substrates, but you may use this technique on other types of materials as well. Thermal oxidation involves exposing silicon to extremely high temperatures (typically 800 to 1200 °C). Plasma Oxidation Plasma oxidation involves exposing substrate surfaces to reactive plasma species to induce surface oxidation and activation. You may also see this technique referred to as micro-arc oxidation (MAO). This technique is ideal for producing ceramic layers on the surface of metals. These coatings have two to four times the hardness of steel or hard anodising. The basic plasma oxidation process uses an electrolyte bath of a dilute aqueous solution, with reagents added based on desired surface coating properties. A high voltage is then passed through the electrolyte, generating plasma on the substrate’s surface. Role of Biasing in PVD During physical vapour deposition, you can apply a bias voltage to the surface of a substrate to adjust its ion energies, tailor the coating structure, and alter its mechanical properties. In some cases, PVD substrate biasing can be self-generating. This occurs when insulating substrates are immersed in RF (radiofrequency) plasma. As the bias is increased, the bombardment of the substrate increases, improving the film’s dentification and adhesion. Substrate biasing in PVD can help you to control the deposition rate and adjust film properties. Thus, it is a very useful technique for fine-tuning the surface of your substrate. Effect on Deposition Rate Deposition refers to the controlled growth, transfer, or synthesis of materials as thin films on substrates. These materials can be either crystalline, polycrystalline, or amorphous. In PVD, biasing affects the deposition rate by influencing ion bombardment energy and flux onto the substrate surface. Substrate biasing during deposition is commonly used in both sputtering and thermal deposition. Sputtering relies on vacuum deposition biasing to dislodge atoms from the target with a high-energy source. The atoms can then be deposited onto the target surface, typically using a plasma arc. Learn more about sputtering systems from Korvus Technology. Thermal deposition involves using vacuum pressure and very high temperatures to vaporise the target material. You may also use substrate biasing in chemical vapour deposition (CVD). This process involves using volatile precursors to deposit gaseous source materials onto the surface of substrates. Impact on Film Properties Substrate bias control can influence film properties, such as crystallinity and thickness uniformity. Thus, substrate surface modification is useful when producing films that require specific uniformity or crystallinity, such as computer microchips and medical implant devices. Enhancing PVD With Substrate Biasing Techniques Proper substrate preparation is necessary to achieve uniform results with your substrates. Thorough cleaning, oxidation, and biasing will help to ensure that you achieve the desired outcome for your project. If you would like to learn more about substrate biasing in PVD or our HEX Series PVD systems, contact Korvus Technology today. References [1] H.L. Brown, S.A. Thornley, S.J. Wakeham, M.J. Thwaites, R.J. Curry & M.A. Baker (2015). The Impact of Substrate Bias on a Remote Plasma Sputter Coating Process for Conformal Coverage of Trenches and 3D Structures, Journal of Physics D: Applied Physics 48:33, DOI 10.1088/0022-3727/48/33/335303 [2] L. Bardos, H. Barankova & L.E. Gustavsson (2006). Effect of Substrate Material and Bias of TiN Films Deposited in the Hybrid Plasma Reactor, Journal of Vacuum Science & Technology A 1655-1659, DOI: 10.1116/1.2167082 [3] H.B. Profijt, M.C.M. van de Sanden & W.M.M. Kessels (2013). Substrate-Biasing During Plasma-Assisted Atomic Layer Deposition To Tailor Metal-Oxide Thin Film Growth, Journal of Vacuum Science & Technology A 31, 01A106-1/10, DOI: 10.1116/1.4756906 [4] W. Zheng, L. Yi, K. Tao, Y. Ma, P. Chang & J. Wu (2006). The Influence of Substrate Bias in I-PVD Process on the Properties of Ti and Alloy Films, Journal of Materials Science: Materials in Electronics 931-935, DOI: 10.1007/s10854-006-0046-8

If you’re unfamiliar with physical vapour deposition (PVD), here is a brief explanation. PVD is a process that vaporises a material within a vacuum chamber, which you may then deposit onto materials that can be both electrically conductive and insulating as a thin-film of alloyed material or as a pure metal coating. To ensure good results with this process, you must understand how substrate heating affects PVD. Below, we explain everything you need to know about substrate heating in PVD for film uniformity. You will learn about the role of temperature control, various substrate heating methods, and factors influencing film uniformity. Understanding Substrate Heating Have you ever wondered why paying attention to PVD substrate heating is important? The main reason is that it can affect the outcome of the deposition process. Without proper heating, your substrate may be too thin and have inadequate PVD film uniformity. It may also end up with poor adhesive properties. These are common problems for those who are unfamiliar with substrate heating. You may have even experienced such issues with your own substrates. For instance, perhaps you wished to apply a thin silicon oxide layer to your substrates but ended up with less-than-ideal results. Poor temperature control may be to blame. To achieve uniform film deposition, you must understand the basics of substrate heating. We will discuss these basics next. Principles of Substrate Heating in PVD Substrate heating in PVD may seem complex, but it boils down to two simple factors. High temperatures favour the rapid formation of defect-free crystals, while low temperatures result in amorphous structures. High temperatures are ideal for creating strong substrates with good adhesive properties, such as computer chips. Low temperatures are better for substances that must remain flexible, such as a contact lens or a sheet of plexiglass. Heating the substrate is also effective during the cleaning process. Doing so removes water and dust from the surface of the substrate, allowing for better adhesion of the film. Role of Temperature Control in Film Uniformity Uniformity is key when producing thin-film coatings. It wouldn’t do to have a film that has a thickness that varies widely across a substrate. A lack of uniformity can cause films to perform poorly or in ways you didn’t intend. Proper heating allows you to create the proper crystal structure for your films. Cooling is important for the deposition sources, too, as it protects your films from process radiation emanating from the vaporisation process. Substrate Heating Methods There are several substrate heating methods to choose from, although no method is necessarily better than the others. The best method depends on your budget, space constraints, and desired temperature range. You can choose from resistive heating, inductive heating, or radiative heating methods. All of these methods are RHEED (reflection high-energy electron diffraction) compatible and capable of heating substrates to a minimum of 950 °C (depending on your equipment). Resistive Heating Methods Filament heating is the main method of resistive heating. This process requires a filament to have a current passed through it, in doing so, the filament will begin to heat up due to the electron flow. This can generate high temperatures but is limited by the need for it to be in contact with anything it needs to heat. This is a very common process due to its simplicity and is used in lots of vacuum systems. Inductive Heating Methods Inductive (or induction) heating uses an extrusion-based metal wire additive as an energy source. It is highly regarded for its ability to produce high deposition rates while reducing manufacturing times. It is also very efficient and boasts a longer life than resistance heating methods. It is not very applicable to substrate heating however due to larger radiative losses. The main downside of using it as a deposition technique is that films can become detached from the substrate because of the formation of an oxide layer. Radiative Heating Methods Radiative heating is the only process that does not require direct contact between the heating source and the sample. This process is the transfer of heat through the radiation produced. Heat produced from a process such as resistive heating can radiate across the vacuum chamber and heat a sample. This process cannot produce as high temperatures as the others due to large losses of heat into the chamber. The radiation intensity will decrease by an inverse square law with relation to the distance between heat source and sample – therefore, as shorter distance is best. Factors Influencing Film Uniformity When producing thin films, paying strict attention to uniformity is essential. Imagine what would happen if a chip in a patient’s medical device was too thick or too thin. The device might malfunction and lead to serious injury. Several factors can affect film uniformity: substrate properties, deposition parameters, and process conditions. Substrate Material and Properties Substrates come in many different materials, including glass, metal, and concrete. Wood and paper products can also serve as substrates. These substrates are challenging to work with because they are anisotropic, which means that their surface properties differ depending on the direction of the substrate. The substrate’s surface condition can strongly impact the bond of subsequent layers and, in turn, their uniformity. For instance, it can be difficult to achieve uniformity with substrates that contain steps or trenches. If you wish to achieve the most uniform film possible, pay close attention to the molecular properties of your substrate and choose your heating method accordingly. Deposition parameters and process conditions can play a big role in film uniformity as well. Factors influencing film uniformity include: Distance between the substrate and the target Relative motion between the substrate and the target Target geometry The magnetron scattering source Thermal Management Strategies If you are having difficulties managing substrate heating in PVD for film uniformity, try these substrate heating techniques and thin film uniformity methods: Employ a system with independently heated filaments. Such a system counters the effects of the edges of substrate holders. Use tantalum shielding to cover electrical and mechanical parts to prevent overheating. Choose substrates with high thermal conductivity to keep temperatures low. This technique is necessary if producing boards for vehicles, industrial electronics, smartphones, and computers. Keep a close eye on your thermocouple attachments. For thermocouples to provide accurate readings, the wires must remain separate and only joined at the bead. If your profile graph shows an erratic reading, this indicates a loose attachment. Optimising Substrate Heating for Uniform Film Deposition During substrate heating, uneven temperatures are a recipe for poor deposition results. As the temperature has such a large impact on both the uniformity and the adhesion of the film – a varying temperature will create a film with varying properties. For suitable results, you must maintain even temperatures throughout the heating process. Learn how to accomplish this below. Temperature Profiling and Control Temperature profiling, or thermal profiling, allows you to determine whether a thermal profile is outside of specifications or a set tolerance limit. In thermal profiling, the centre of a process window is zero, while the edges of the window are 99%. If the Process Window Index (PWI) is equal to or greater than 100%, it is outside of process limitations. Two thermal profiling methods are ramp-soak-spike (RSS) and ramp to spike (RTS). RSS allows for a process limit of about 4 °C/second, while RTS permits approximately 1-2 °C/second. Thermal Uniformity Across the Substrate Surface As mentioned above, one way to maintain PVD film uniformity across a substrate surface is to use a system with independently heated filaments. This allows you to control temperatures across the entire substrate surface so you don’t get any hot or cold zones. Using the Rotating Wafer Thermal Imaging (RWTI) technique is another option. This technique employs multi-zone heating systems that produce temperature uniformity of less than 2 °C in the range of 600 °C to 1,100 °C. Yet another method involves placing the substrate into a thermal processing chamber, rotating the substrate during heating, and measuring the temperature at a plurality of radial locations during rotation. To Summarise Substrate Heating in PVD If you wish to achieve good results, you must pay careful attention to substrate heating in PVD for film uniformity. Resistive, inductive, and radiative heating methods can help you maintain stable temperatures and reliable uniformity. You can also take advantage of thermal profiling to ensure that your temperature profiles are within a set tolerance limit for PVD or CVD. Want to learn more about substrate heating or our HEX Series modular PVD systems? Reach out to Korvus Technology today. References [1] M. Ohring (2002). Film Uniformity, Materials Science of Thin Films 95-144, DOI: 10.1016/B978-012524975/50006-9 [2] R.K. Choubey, G.K Sharma & P.K. Jain (2023). On Identifying the Suitable Substrate Medium for Induction Heating-Based Metal Wire Additive Manufacturing, Recent Advances in Manufacturing and Thermal Engineering 249-259, DOI: 10.1007/978-981-19-8517-1_18 [3] B. Zhang (2016). Amorphous and Nano Alloys Ectroless Depositions, Technology, Composition, Structure, and Theory 323-381, DOI: 10.1016/B978-0-12-802685-4-00006-6 [4] C. Guo, M. Kong, C. Liu & B. Li (2013). Optimization of Thickness Uniformity of Optical Coatings on a Conical Substrate in a Planetary Rotation System, Applied Optics 52:4, B26-32, DOI: 10.1364/AO.52.000B26

Pulsed direct current (DC) magnetron sputtering is a physical vapour deposition technique for depositing metallic coatings with precise mechanical, electrical, and optical properties. This technique is especially beneficial for depositing dielectric materials, which are coatings made from non-conducting textiles. Pulsed DC sputtering offers one main advantage over traditional DC sputtering: arc suppression. This process significantly reduces or even eliminates the occurrence of undesired arcs, which could otherwise damage the thin film quality. This article explains the pulsed DC sputtering process, the equipment necessary to achieve this effect, and both the advantages and disadvantages of pulsed DC sputtering to keep in mind. The Pulsed DC Sputtering Process Pulsed DC sputtering was a novel physical vapour deposition technique in the early 2000s that today is commonly used to deposit smooth, ultra-dense metallic coatings. Pulsed DC sputtering involves placing a target material in a vacuum chamber, removing H2O, air, and H2, and then backfilling it with a high-purity inert process gas to create kinetic energy. Then, a pulsed DC electrical current is applied to the target coating material while a positive charge accumulation is applied to the coating material. Both unipolar pulsed sputtering (with one pulse) and bipolar pulsed sputtering (with two pulses) are common. Applying a strong negative pulse to the target initiates sputtering, this generates a plasma within the inert gas, the positively charged ions are then attracted to the cathode and begin to bombard the target. Then, a low-voltage short-duration cycle reversal occurs, scrubbing the target surface to prepare it for the next pulse sputtering process. What Is the Frequency of Pulsed DC Sputtering? The pulsed DC sputtering process is usually carried out through a negative bias with pulsing frequencies between 10 and 350 kHz. This variable frequency range suppresses the arc formation at the target. However, researchers are also learning the benefits of applying mid-frequency (100 to 350 kHz) pulses. This technique could allow for better control over the ion current. Equipment Used in Pulsed DC Sputtering Using the right equipment can prevent arc formation during the pulsed DC sputtering process and ensure a strong bond between the coating and the target material. The equipment must deliver the correct variable pulses and power supplies to maintain stability and precision. The Fission DC and RF Sputtering Source is the premier choice for numerous technical applications globally. This system allows for a quick transition between standard DC and RF (radio frequency) sputtering along with being compatible with pulsed-DC and HiPIMS power supplies. You can also initiate a reactive sputtering process by introducing reactive gas directly into the vacuum chamber or through a separate gas feed allowing for a wider range of thin-films to be produced — whichever makes the most sense for your manufacturing process. Industry Applications Pulsed DC sputtering is widely used in the optical and industrial coating industries. Its primary use is within the sputtering process of metals and dielectric coatings. Dielectric coatings consist of thin layers of transparent dielectric materials. Their purpose is to alter the reflective properties of the target surface, often to make the surface more reflective. This technique is useful in applications like: Highly reflecting laser mirrors Dichroic mirrors Optical filters Beam splitters Heat reflectors Solar cell covers Thin-film polarisers In these applications, the coating substrate is often a type of glass. Pulsed DC sputtering also has practical applications like: Tool coatings, especially titanium nitride coatings that provide long-lasting durability through harsh applications Photovoltaic cells such as solar cells that need to be highly reflective and last for decades through strong weather conditions Decorative coatings, as they can easily create colour uniformity in a large area What Are the Advantages of Pulsed DC Sputtering? When choosing between evaporation and sputtering, pulsed DC sputtering poses several advantages, such as: Adhesion of coatings: DC sputtering processes create a strong adhesion of coatings to target materials, essential for applications ranging from metal tools to photovoltaic cells Arc suppression: Pulsed DC sputtering creates a deposition without arcing by using high-negative pulses rather than small-positive pulses High deposition rates: By reducing the challenges associated with charge buildups and arcs, manufacturers can achieve higher deposition rates of the dielectric materials. Deposition of dielectrics: A big advantage of pulsed DC is that is allows for the deposition of dielectrics by scrubbing the surface of the target of a sheath of positive ions that form on the surface of a non-conductive target. What Are the Disadvantages of Pulsed DC Sputtering? Pulsed DC sputtering eliminates many of the most frequent issues within the sputtering process, such as low deposition rates and ionisation. However, it does present a few disadvantages. While pulsed DC sputtering can significantly reduce arc discharge damage compared to traditional DC sputtering, this benefit is not foolproof. Arcs can still form, and they can lead to a serious quality control breakdown that requires researchers to restart the entire sputtering process. Reactive sputtering in general sometimes experiences hysteresis phenomena, which presents as a dynamic lag between the input and output in magnetisation processes. Final Thoughts Pulsed DC sputtering proves a reliable thin film deposition method that minimises arc formation and produces high-adhesion coatings. If you’re looking to incorporate pulsed DC sputtering into your manufacturing processes, Korvus Technology can provide you with the user-friendly, efficient technology you need. Explore our HEX Series with sputtering functionality to learn about our physical vapour deposition equipment, then get in touch with us today. References [1] Alami, J. et al. (2009). “High power pulsed magnetron sputtering: Fundamentals and applications.” Journal of Alloys and Compounds, 483:1-2. [2] A Belkind et al. (2003). “Characterization of pulsed DC magnetron sputtering plasmas.” New Journal of Physics, 7:90. [3] Arnell, R.D. et al. (2004). “Recent developments in pulsed magnetron sputtering.” Surface and Coatings Technology, 188-189. [4] Jonsson, L.B. et al. (2000). “Frequency response in pulsed DC reactive sputtering processes.” Thin Film Solids, 365:1.

Physical vapour deposition (PVD) has become an integral technique in the manufacture of numerous goods, ranging from semiconductors to PET films and cutting tools to reflective films. This process can also produce highly conductive surfaces ideal for electrical applications — such as electrical contacts. In a nutshell, producing a PVD coating for electrical contacts involves depositing thin films of metals onto target materials using a vacuum chamber. PVD for electrical contacts creates the ideal purity, uniformity, and conductivity, proving highly valuable within the development of circuit breakers, electromechanical power switches, and other applications. This article summarises the methods and applications of PVD for electrical contacts. Why PVD Is Being Used for Electrical Contacts Electrical contacts are an essential part of many electrically controlled switches that either complete or interrupt an electrical circuit, facilitating an electrical current. They consist of electrically conductive materials, like silver alloys, gold, and platinum-group metals. Recently, electrical contact manufacturers have begun using PVD to develop thin metal coatings for contacts. Compared to alternative processes, PVD promotes a higher purity of the deposit layers, low thermal impact, excellent adhesion, and virtually limitless coating materials. The benefits of PVD in electrical components, like contacts, include: Enhanced Conductivity and Performance Electrical contacts must have a high level of electrical conductivity to carry the electrical current. Manufacturers have begun using PVD for electrical contacts because it creates an electrically conductive surface on a wide range of target materials. The properties of PVD are ideal for enhancing electrical contact performance, ensuring a potential for strong conductivity. Increased Durability One of the primary benefits of PVD coating technologies for any application, including electrical contacts, is exceptional durability. Certain PVD coatings are extremely scratch-resistant and durable. This makes them reliable solutions within breaker boxes and other electrical circuits that depend on electrical contacts to stimulate the flow of electricity. With PVD, you don’t need to worry about the coating wearing off over time. Corrosion Resistance PVD coatings also boast extreme corrosion resistance , which is a beneficial characteristic for metallic materials. Traditional electrical contacts may corrode over time due to oxidation. But PVD coatings withstand environmental conditions well, contributing to their durability. Understanding PVD Technology PVD is a revolutionary technology that has become integral in applications ranging from home hardware to jewellery and windows to drill bits. At its core, PVD is the process of depositing a thin film coating onto a substrate like metal, glass, or ceramics. The process transitions a material into a vapour phase and then into a thin film condensed phase, which can be deposited on the target material in a thin layer. When comparing PVD vs. CVD and other coating technologies, PVD for electrical contacts offers advantages like uniformity, high deposition rates, precision control, and excellent adhesion. Types of PVD Processes Several types of thin film deposition processes can facilitate physical vapour deposition, including sputtering, thermal evaporation, and organic evaporation. Sputtering involves ejecting material from a target onto a substrate using ion or atom bombardment. Thermal evaporation, one of the simplest forms of PVD, uses a resistive heat source to evaporate the material in a vacuum environment. In contrast, organic evaporation uses low-temperature evaporation to form thin films of organic materials. Advantages of Using PVD Physical vapour deposition is a cost-effective, reliable, environmentally friendly method of creating thin coatings and finishes. It doesn’t release any harmful gases or substances and produces no waste. It allows for exceptional precision and control over the exact thickness and composition of the thin film. PVD in Electrical Contact Applications PVD coatings have proven highly effective in a range of electrical contact applications. Using PVD for electrical contact surface finishing improves the electrical and mechanical performance of the contacts and provides long-lasting durability. Material Selection for PVD Metals like gold, silver, and palladium alloys are common choices for PVD within electrical contact applications. Other metals, like titanium, chromium, tungsten, and aluminium, are also used. Chosen metals must have the correct properties to form carbonitride and nitride coatings when combined with reactive hydrocarbon-based gases. However, the versatility of thin film deposition for contacts allows many substrate materials to adhere well to the vapourised metal coatings. Application Examples PVD coatings are ideal for many contact applications within electrical engineering, optoelectronics, optics, and medical technology. This technology can effectively metalise nonconductive materials, allowing manufacturers to create electrical contacts on a wide range of substrates and potentially save money during manufacturing. Final Thoughts Physical vapour deposition boasts numerous benefits for electrical contact applications, including enhanced conductivity, durability, precision, environmental friendliness, and more. Moving forward, researchers expect more and more electrical manufacturers to begin using PVD within their applications. Are you looking for a thin film deposition system that can facilitate PVD for electrical contacts or other applications? Get in touch with Korvus Technology today at 01280 852096. We will discuss our HEX series systems and help you find the right system for your organisation. References [1] Grechanyuk, N. I., et al. “Properties of Cu-Mo Materials Produced by Physical Vapor Deposition for Electrical Contacts.” Powder Metallurgy and Metal Ceramics, vol. 60, no. 3-4, July 2021, pp. 183+. Gale Academic OneFile, link.gale.com/apps/doc/A679120795/AONEu=anon~b06deda1&sid=googleScholar&xid=f6ead6c5. Accessed 11 Mar. 2024. [2] “Physical Vapor Deposition (PVD).” PCB Design & Analysis, Cadence PCB Solutions. https://resources.pcb.cadence.com/blog/2023-physical-vapor-deposition-pvd. Accessed on 11 Mar. 2024. [3] Rajan, Vincent Femila, et al. “Chapter 12 – Nano based technologies for antibacterial, antifungal, and antiviral coatings.” Antiviral and Antimicrobial Smart Coatings, 2023, pp. 357-412. https://www.sciencedirect.com/science/article/abs/pii/B9780323992916000013. Accessed on 11 Mar. 2024. [4] “Surface Coating Technologies.” Electrical Contacts Wiki. https://www.electrical-contacts-wiki.com/index.php/Surface_Coating_Technologies. Accessed on 11 Mar. 2024cer

Written by Korvus Technology Published on November 3, 2022 The many applications of vacuum deposition processes span industries. Manufacturers use vapour deposition in solar cells, medical implants, LED displays, and other products. Manufacturers and researchers use one of two types of thin film deposition: physical vapour deposition (PVD) and chemical vapour deposition (CVD). Between PVD and CVD, your ideal system will depend on your substrates and application needs, including performance at a high temperature. Below, we explore PVD vs CVD by explaining both techniques and presenting the advantages of each to help you choose your ideal system. What Is Physical Vapour Deposition? Physical vapour deposition takes a solid precursor material and turns it into a gas in a reacting chamber, where the atoms deposit a thin film onto a substrate through condensation. Most PVD coating applications use the following techniques: Evaporation Thermal evaporation vaporises a coating material, turning it into a gas. The released atoms enter a reaction chamber and coat the surface of a substrate material in a very thin layer. Sputtering The sputtering process uses plasma ions moving at high speeds to release atoms from the source material. The atoms in the reaction chamber stick to the target substrate. Korvus Technology’s HEX Series thin film deposition system supports several techniques, including sputtering. What is Chemical Vapour Deposition? Chemical vapour deposition is similar to PVD, but the difference is that CVD uses volatile precursors to deposit a gaseous source material onto the substrate’s surface. Chemical reactions initiated through heat or pressure cause the coating material to form a thin film on the substrate in the reacting chamber. What Is the Difference Between PVD and CVD? While both processes create thin films over substrate materials, PVD and CVD coating techniques differ in several ways: Process The coating process is the main difference between PVD and CVD. Physical vapour deposition uses physical reactions to change a liquid source material to a gas. The material then returns to its solid state as a thin layer on the surface of the substrate. Chemical vapour deposition creates thin films using chemical reactions. The polymerisation and coating phases occur at the same time, which creates copolymers of different monomers for a broad range of applications [1]. PVD and CVD coating processes also differ in how well they coat the substrate. PVD does not perform as well on the sides and back of the coating substrate, whereas CVD techniques produce a uniform thin coat on uneven surfaces. Temperature PVD deposition occurs at a relatively low temperature, up to 450 degrees Celsius. CVD deposition requires higher temperatures above 900 degrees Celsius [2]. Due to the high temperatures, the CVD process often includes heat treatment of the coated surface. Application PVD can improve a substrate’s tolerance to high temperatures and ablation, ideal for glass and decorative coatings, diffusion barriers, and aerospace technology. The high-temperature CVD process creates thin films with superior purity and uniformity. Applications include protective layers, semiconductors, and more [1]. What Are the Advantages of CVD Over PVD? Chemical vapour deposition provides a versatile process for coating the surface of a substrate. When considering PVD vs CVD, keep in mind these advantages of the CVD method: High purity: Many manufacturers prefer CVD for coating materials that require specialised thin films at an exact desired thickness. CVD uses gas coating materials, avoiding the impurities of liquid coating processes. Uniform coating: CVD is a conformal deposition process, which means it uniformly coats a substrate regardless of the shape to produce an even coating. This method builds the desired layer from the substrate up, a significant advantage in creating conductive films [1]. Application variety: Manufacturers use CVD to create thin layers on many materials regardless of rigidity, flexibility, or density [1]. You’ll find CVD systems across industries, from electronics manufacturing to producing crisp bags. CVD can produce large graphene sheets, carbon nanotube arrays, and other essential coated manufacturing materials [3]. Cost: CVD systems cost less than PVD systems. The possibilities of the CVD method continue to expand into new applications. What Are the Advantages of PVD Over CVD? Physical vapour deposition is an often-used method for coating inorganic materials, such as metal and some organic materials. It offers many advantages, including the following: Temperature resistance: PVD films can withstand temperatures over 400 degrees Celcius, making them ideal in the manufacturing of high-performance solar power technology and other applications that require resistance to intense heating [4]. Abrasion and impact resistance: PVD techniques can create a very thin layer of only 2.5 micrometres that provides superior resistance to abrasions. Environmental friendliness: Unlike CVD, PVD does not produce hazardous byproducts and does not use hazardous gases in its processes. Instead of using a reactive gas, PVD uses high-power electricity or lasers to gasify the coating material. Wear-resistant coating: Manufacturers use PVD for many coating applications, including improving wear resistance and reducing the friction of cutting tools, and creating anisotropic glasses for semiconductors. You’ll see examples of PVD use across industries, including architecture, automotive, jewellery, and more. When comparing PVD and CVD costs, PVD tends to cost more than CVD, but many manufacturers consider PVD best for their applications. Conclusion – PVD vs CVD Coating To summarise, PVD and CVD both function as methods of binding the desired layer to a substrate material. The primary difference is that PVD uses a liquid source material to create a thin film, while CVD uses a gaseous source material. PVD and CVD suit different applications, depending on purity, speed, and cost requirements. You may choose a CVD system to form graphene sheets for electronics, or you may select a PVD system for metal coating with plasma ions for solar panels. If you’re looking for a compact, high-performance PVD system, Korvus’ HEX series modular PVD system supports sputtering, thermal evaporation, sample preparation, pulsed laser deposition, and organic PVD thin film deposition. Every vapour deposition application comes with different requirements, and we can provide a custom solution that meets your needs. The versatile HEX series provides the perfect system to teach thin film methodology, research new coatings, or deposit thin films through benchtop production. References [1] Asatekin, A., Barr, M. C., Baxamusa, S. H., Lau, K. K. S., Tenhaeff, W., Xu, J., & Gleason, K. K. (2010). Designing polymer surfaces via vapor deposition. Materials Today, 13:5, 26–33. https://doi.org/10.1016/s1369-7021(10)70081-x [2] Musbah, A., & Eljaafari, W., Fessatwi, E., & Elsahli, Y. (2022). Comparison Between Chemical Vapor Deposition CVD and Physical Vapor Deposition PVD Coating Techniques: A Review Paper. February 2022. [3] David L. Chandler. Explained: Chemical vapor deposition. MIT News | Massachusetts Institute of Technology. https://news.mit.edu/2015/explained-chemical-vapor-deposition-0619. Accessed 02 November 2022. [4] Selvakumar, N., & Barshilia, H. C. (2012). Review of physical vapor deposited (PVD) spectrally selective coatings for mid- and high-temperature solar thermal applications. Solar Energy Materials and Solar Cells, 98, 1–23. https://doi.org/10.1016/j.solmat.2011.10.028

Written by Matt Clancy Published on March 30, 2022 The deposition of a thin-film is a critical manufacturing step involving creating and applying a coating onto a substrate material. The coating can be a compound, metal, or oxide. Each coating has a unique set of characteristics to enhance the substrate and ensure that it is suitable for its application. For example, a coating can protect the substrate against extreme temperatures, scratches, or infrared radiation. A coating can also be transparent or change the conductivity of the substrate. Various methods exist to apply thin films to substrates, and the suitable method depends on the source material, substrate, and application. This guide looks at electron beam evaporation applications, one of the most effective forms of physical vapour deposition, and what this thin-film deposition method entails. To learn more about the equipment necessary for e-beam evaporation, sputtering, and thermal evaporation, read more about the HEX Series from Korvus Technology. Physical Vapor Deposition: What Is E-Beam Evaporation? Various industries use high-vacuum chamber systems for the thin-film deposition of materials, such as insulators or metals, to substrates. The processes for producing these films include physical vapour deposition (PVD) and chemical vapour deposition (CVD). Physical vapour deposition processes are ideal for creating a rigid thin film resistant to extreme temperatures and corrosion. The three primary physical vapour deposition (PVD) methods for thin films include: Sputtering Thermal evaporation Electron-beam evaporation (e-beam evaporation) Sputtering involves plasma generation under high voltage between the source material and the substrate. These methods include ion beam-assisted deposition, reactive sputtering, and magnetron sputtering. Electron-beam and thermal evaporation use an evaporation coating process. An electric current heats the target material during the thermal evaporation process, melting it and evaporating it to a gaseous phase. The vapour cloud travels upwards in the deposition chamber and precipitates against the substrate that requires the coating, forming a thin film. The e-beam evaporation process is similar to thermal evaporation in that it uses evaporation deposition. However, an e-beam evaporation system doesn’t heat the evaporation material using electric resistance. Instead, a charged tungsten filament aims a beam of high-energy electrons at the source material or a crucible containing the target material. The high kinetic energy of the focused electron beam transfers to the target material, which evaporates and deposits onto the substrate. The e-beam has a high electricity density, allowing for the efficient evaporation of high-melting-point materials that don’t sublimate during thermal evaporation. These materials include deposit metals and materials that transition to a vapour phase at high temperatures, including gold, platinum, and silicon dioxide. Electron-Beam Deposition: An Overview of the Thin-Film Deposition Process An electron beam system has two components – the electron gun, containing a filament, and the crucibles, containing the evaporation materials for coating the substrate. The substrate is above the crucible in the vacuum chamber. Heating the tungsten filament [1] is necessary to generate the electron beam. Sending a current of up to 10 kV through the electron gun heats the filament and generates an electron beam via thermionic emission. E-beam generation can also occur via the field-electron emission or anodic-arc method. Depending on the electron-beam configuration, a set of magnets direct the electron beam towards the evaporation materials in the crucibles. When the electron beam hits this source material, the high energy of the electrons converts into heat, evaporating the material. The evaporated material is a vapour stream that traverses the vacuum environment without colliding or reacting with other atoms. When the vapour hits the substrate, it clings to the surface as a thin film. Electron-Beam Evaporation Configurations Three electron-beam evaporation configurations exist: Electromagnetic focusing Electromagnetic alignment Pendant drop configuration E-beam evaporation systems with electromagnetic focusing and alignment configurations bend and guide electron beams towards the source material using a magnetic field. With magnetic field e-beam guidance, direct heat transfer occurs instead of indirect heating via the container. [2] In e-beam evaporation systems with a pendant drop configuration, the evaporation material is in the form of a wire or a rod in the centre of a cathode loop. As the rod’s tip melts, the material evaporates to coat the substrate. Reactive Evaporation vs Co-Evaporation A reactive gas, such as oxygen or acetylene, reacts with the target material vapours near the substrate to form the thin film during reactive electron-beam evaporation. The co-evaporation process involves simultaneously heating a metal and carbon ingot to form a metal carbide film on the substrate. Electron Beam Evaporation Applications in Modern Times The Advantages of E-Beam Evaporation Electron-beam evaporation is a thin-film deposition method with a wide application range. The direct heat transfer between the e-beam and the target material is the most significant advantage of e-beam evaporation over thermal evaporation. Electron-beam evaporation allows for very high deposition rates and high melting temperatures, including: Refractory metals, such as tantalum, tungsten, and graphite Metals with high melting temperatures, such as silicon dioxide and gold With a deposition rate ranging from 0.1 to 100 nanometers (nm) per minute at low substrate temperatures, e-beam evaporation is ideal for achieving a high-density thin film and optimal substrate adhesion. The ability to control the coatings’ reflection of specific wavelength bands is valuable in producing laser optics and architectural glass products. The crucible holding the target material typically has a copper or tungsten construction. [3] Crucibles holding high-temperature materials can also be ceramic. The focused electron beam only heats a small area of the target material, which means there is enough room for multiple crucibles in the high-vacuum chamber. An e-beam evaporation configuration with a four-pocket hearth can contain up to four source materials. This configuration allows for the sequential deposition of four material layers without needing to break the vacuum. During some e-beam evaporation techniques, water cooling the crucible prevents it from heating through thermal energy. Directly heating the source materials also eliminates the risk of heat damage to the substrate. The electron beam only heats the target materials and not the crucible. Keeping the crucible cool throughout e-beam evaporation prevents target material contamination and maximizes material use efficiency, reducing costs. In others, the crucible is the part targeted by the electrons and so is the part of the source being heated, this is turn, indirectly heats and vaporises the material within the crucible. Electron-Beam Evaporation Applications The automotive and aerospace industries typically use e-beam evaporation when constructing components that should have high wear resistance. This process creates rigid chemical barriers resistant to extreme temperatures and corrosive environments, making it ideal for manufacturing cutting tools, machinery components, and marine fittings. Optical Thin Films Multi-layer electron-beam evaporation allows for the production of optical films with unique reflective and transmissive properties. It is possible to achieve specific film properties by layering multiple optical coatings—for example, cold filters that block infrared radiation on a glass substrate. Optical and oxide thin films have multiple uses. Applications requiring optical coatings include the production of architectural glass, laser optics, solar panels, semiconductors, and eyeglasses. Metallic Films With the e-beam evaporation of low-resistance metals, manufacturers can produce various metallic films, including wiring films, decorative films, electromagnetic shielding films, and reflective films. The products requiring metallic film e-beam evaporation during production include: Power packs Organic and inorganic electroluminescent (EL) diode displays Surface acoustic wave (SAW) filters Some components of watches and lithium-ion batteries also have metallic films. Electron-Beam Evaporation Limitations Like thermal evaporation, e-beam evaporation is a line-of-sight deposition method and is unsuitable for coating the inner surfaces of complex geometries. Secondary electron emission and X-ray production can cause incident electron energy loss. During e-beam evaporation, filament degradation can also cause an inconsistent evaporation rate by the e-beam. E-Beam Evaporation System: How Does It Work? Electron beam evaporation involves the acceleration of electrons as a targeted beam to a source material within a crucible. Quartz crystal monitors [4] regulate the thickness of the developing film during deposition. The HEX Series by Korvus Technology includes compact thin-film deposition systems. These high-end systems are suitable for a wide range of research and development applications with sufficient energy for several deposition methods, including: Sputtering Thermal evaporation Electron-beam evaporation Organic physical vapour deposition (PVD) Pulsed laser The Korvus’ thin film deposition systems feature a modular design with a six-sided vacuum chamber that is lightweight but rigid. The systems offer six modular panels that include: A blank panel A viewport panel A deposition source panel A QCM panel for evaporation speed monitoring A pulsed laser deposition (PLD) instrument panel for controlling mass flow and film thickness The HEX deposition systems are highly versatile with standard fittings, including Hamlet gas and water connections. The base HEX system features a multi-sample hearth and supports electron microscopy (EM) sample preparation, new film research, magnetron sputtering deposition optimization, and other methodologies. Final Words E-beam evaporation is among the most effective methods for the deposition of dielectrics and metals with high melting points. Generally speaking, this process offers a higher deposition rate than resistive thermal evaporation or sputtering. Electron beam evaporation also offers exceptional directionality, allowing multiple crucibles and optimal target material heating. The high uniformity and purity levels translate to a high material use efficiency and low costs. These systems are also compatible with ion-assist sources. To learn more about the benefits of other deposition methods, read these articles on thermal evaporation, sputtering, and PVD coating. References [1] Bishop, Charles. (2007) “Electron Beam (E-Beam) Evaporation,” Chapter 15 in Vacuum Deposition onto Webs, Films, and Foils, 239-250. Elsevier Press. DOI:10.1016/B978-081551535-7.50013-6 [2] Wang, Zhongping, and Zengming Zhang. (2016) “Electron Beam Evaporation Deposition.” In Advanced Nano Deposition Methods, 33–58. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. http://dx.doi.org/10.1002/9783527696406.ch2. [3] Madou, M. J., Fundamentals of Microfabrication: The Science of Miniaturization, 2nd Edition. CRC Press (2002), 135–136. [4] Varineau, Pierre T., and Buttry, Daniel. (1987) “Applications of the Quartz Crystal Microbalance to Electrochemistry.” J. Phys. Chem. 1987, 91, 6, 1292–1295. https://doi.org/10.1021/j100290a003

Written by Korvus Technology Published on August 8, 2023 What Is Low-Temperature Thermal Evaporation of Organic Materials? Low-temperature evaporation offers a unique alternative that minimises the energy requirements and high-temperature risk involved in evaporating organic materials. Low-temperature evaporation uses a vacuum chamber to vaporise materials, through thermal deposition techniques. This low temperature in the source allows for temperature-sensitive materials to be deposited effectively and safely. How Low-Temperature Evaporation Works for Thin Film Deposition Many organic materials already have low boiling points, and exposing them to high temperatures during evaporation is unnecessary. By vaporising organics in a low-temperature evaporation system, these materials can avoid being exposed to unsafe levels of heat that could impact their deposition rate and form ineffective films on the target substrate. Because organic materials are extremely sensitive to temperatures, even a small temperature increase during thin-film deposition could cause the organic material to eject from the source. Low-temperature evaporation techniques allow for greater control over the deposition rate and vacuum temperatures of organic materials within physical vapour deposition. By regulating the temperature in the vacuum system, certain qualities of the organic material can be preserved that would otherwise fail within high temperatures, such as concentration and thickness measurements. If the liquid falls below the necessary boiling temperature, a heat exchanger can recover heat from other sources to increase the temperature within the source. Low-Temperature Evaporation Systems for Controlled Deposition Several low-temperature evaporation techniques offer fine control over material heating power, including: Two-stage systems, which provide intermediate gas cooling between two compressor steps Intercooler systems, which use an intermediate evaporation step to cool the discharge gas Cascade systems, which utilise two refrigeration circuits connected by an intermediate cascade heat exchanger Low-temperature vapour systems typically operate in a feedback loop based on thickness measurements, which allows for a highly specialised layer deposition rate. Most systems maintain normal levels of condensing pressure with low evaporation temperatures. Evaporating the material over multiple stages prevents high local pressures from increasing the discharge temperature of the material. However, some materials with high vapour pressures may exhibit isotropic qualities through vacuum evaporation due to the high local pressures in the deposition plume. Meet the ORCA: Our Solution for Organic Material Deposition The ORCA Organic Evaporation Source from Korvus Technology is a vacuum evaporation system that uses low evaporation temperatures and high thermal conductivity to maximise stability and fine control. This user-friendly system makes low-temperature vacuum evaporation accessible to businesses across the UK, especially those in organic electronics manufacturing. The ORCA supports vapour temperatures ranging between 50 and 600 degrees Celsius and uses a K-Type thermocouple that produces highly accurate temperature readings. You’ll enjoy a simplified solution to low-temperature evaporation that perfectly complements the Korvus Technology modular PVD systems. The ORCA low-temperature evaporation source employs active cooling of the crucible to ensure that the heating process is balanced by a strong opposing cooling process which results in excellent temperature stability and control. The crucible is constructed from high thermal-conductivity material, ensuring no hot-spots arise which could distort the evaporation rate. Optionally, alumina or graphite liners may be employed. The crucible (complete with liner if fitted) is easily removed/swapped without the need for any tools, although this is often not necessary since access to the source in order to refill the crucible is rapid and simple. The K-type thermocouple is inserted into the body of the crucible, giving much more accurate readings than typical touch-contact arrangements. The ORCA is supplied with a power unit coupled with a PID controller tuned for low-temperature operation, ensuring precise temperature control. The source may be used in conjunction with sputter sources, e-beam sources, thermal sources, and others. Thermal crosstalk is minimised through the cooled shielding cap. The ORCA is also perfectly paired with our temperature gradient sample stage, allowing precise temperature control of the substrate. The ORCA system is designed specifically for the evaporation of materials at low temperatures (50-600°C). Conventional evaporation sources typically operate at over 1,000°C, which can lead to temperature control issues. The ORCA’s specialised design for low temperatures prevents such issues, making it an ideal solution for organic evaporation processes. Our low-temperature evaporation and modular PVD systems are reliable, cost-effective solutions for forming thin films across numerous industrial applications. To learn how the ORCA can benefit your company, discover more about the Hex PVD system, or better understand PVD coating, contact Korvus Technology today. Low-Temperature Evaporation vs. Standard Thermal Evaporation Low-temperature evaporation stands in contrast to thermal evaporation, exhibiting these unique qualities. Temperature The primary difference between these two evaporation techniques is the temperature required within the chamber and source. Thermal evaporation methods typically heat the source’s materials to temperatures of 1,000 degrees Celsius or higher, though some standard thermal evaporation systems allow for evaporation temperatures of up to 1,500 degrees [1]. Meanwhile, low-temperature evaporation supports temperatures of 600 degrees Celsius and below. These systems are ideal for organic materials that are extremely sensitive to a small temperature increase and need to maintain highly specific properties for their applications. Design These two evaporation systems also utilise different designs. In a low-temperature vacuum evaporation system, the heating element is separate from the material support. This design allows for more control over the material heating power. In contrast, standard thermal evaporation uses emissions at the heated source that immediately condense onto a cold substrate. There is no separation of the heating element from the substrate materials. Properties A material’s evaporation method impacts its properties, requiring developers to choose the right method when forming thin films. For example, TiN coatings produced using a low evaporation temperature of approximately 200 degrees Celsius showed an increase in hardness and residual compressive stress when compared to the same coating produced with a standard temperature method [2]. In the same study, CrN coatings deposited with low-temperature evaporation demonstrated different small-molecule compounds and chemistry than their standard evaporation counterparts. Radiative Loss Evaporation using lower temperatures significantly reduces radiative loss compared to conventional evaporation sources. This method is more suitable for materials that benefit from slow temperature change during organic evaporation. Applications of Low-Temperature Evaporation for Thin Films The industrial applications of low-temperature evaporation are numerous, spanning industries ranging from pharmaceutical to wastewater treatment. Pharmaceuticals Pharmacists have begun developing a bubble column low-temperature evaporation process for dissolving pharmaceutical APIs improving the production efficiency of pharmaceutical compounds [3]. This method can achieve an evaporation rate of up to 6.4 grams per minute within a single stage. Nanotechnology Researchers have successfully used a low-temperature, catalyst-free evaporation route to evaporate ZnO nanoneedles and nanosaws [4], which can be applied in the development of solar cells. Food Science The food science industry is always looking for new methods of drying and concentrating food products to prevent spoilage. Low-temperature evaporation presents a unique, efficient and energy-saving solution to removing liquid from foods. Traditional drying methods are energy-intensive, but low-temperature evaporation methods can reduce water content before sending foods to the dryer, improving the efficiency of the process. Wastewater Treatment Reducing the volume of wastewater through drying or evaporation can minimise storage needs and disposal costs. By using vacuum evaporation, the liquid in the chamber will evaporate at lower temperatures, reducing the amount of energy necessary for evaporation. Oil Field Vacuum evaporation also plays a valuable role in separating water and other small-molecule compounds from oil. Oil companies can reduce operating costs by using energy-efficient evaporator systems to separate oil instead of traditional thermal evaporators. Battery Science Researchers have even begun using low-temperature evaporator systems within the mass spectrometry titration protocol for quantifying inactive lithium in batteries [5]. References [1] Koskinen, J. (2014). Films and Coatings: Technology and Recent Development. Comprehensive Materials Processing, Accessed on 29 June 2023. [2] Gahlin, Rickard, Bromark, Michael, Hedenqvist, Per, Hogmark, Sture, & Greger Hakansson. (1995). Properties of TiN and CrN coatings deposited at low temperature using reactive arc-evaporation. Surface and Coatings Technology, 76-77:1, 174-180. [3] Roche, Phillip, Glennon, Brian, Jones, Roderick C., & Philip Donnellan. (2021). Low-temperature evaporation of continuous pharmaceutical process streams in a bubble column. Chemical Engineering Research and Design, 166, 74-85. [4] Fan, H.J., Scholaz, R., Dadgar, A., Krost, A., & M. Zacharias. (2005). A low-temperature evaporation route for ZnO nanoneedles and nanosaws. Applied Physics A,, 80, 457-460. [5] Tao, Mingming, Xiang, Yuxuan, Zhao, Danhui, Shan, Peizhao, & Yong Yang. (2022). Protocol for quantifying inactive lithium in anode-free lithium batteries by mass spectrometry titration. Communications Materials, Accessed on 29 June 2023.

Written by Bryan Stuart Published on March 29, 2024 An Introduction to Electron Beam Evaporation and E-Beam Evaporators Electronic beam evaporation, also known as e-beam evaporation, is one of the four main forms of physical vapour deposition (PVD). It uses an intense beam of high-energy electrons to evaporate the source material [1], reducing limitations on maximum evaporation temperatures. E-beam evaporation works in a different way to sputtering, which collides energetic ions with a target to sputter or eject the target material. Electron beam evaporation expands upon the applications of thin film deposition common to more traditional vaporisation processes. But which method is better? Is electron beam evaporation what you need from your thin film deposition system? Read ahead to learn the ins and outs of electron beam evaporation, along with its advantages over sputtering, from our Korvus Technology team. The TAU E-Beam Evaporator The TAU e-beam evaporator stands out with its compact framework, uniquely opting out of the use of beam-bending magnets that are common in bulkier counterparts. Instead, it leverages a positive charge to direct a focused electron beam towards a target crucible, with a DC voltage applied to a tungsten filament to initiate indirect heating and evaporation of the material. Central to the discussion on the e-beam evaporator process is the heat management during material vaporisation. The electron beam is accelerated under controlled conditions to minimize excessive thermal build-up. The TAU incorporates an ingeniously designed enclosed head, significantly reducing the thermal footprint within the vacuum chamber. This meticulous design allows for deposition at lower substrate temperatures, making the TAU an invaluable asset for lift-off techniques and the coating of heat-sensitive substrates, ensuring precision and integrity in the final application. The Electron Beam Evaporation Process Electron beam evaporation is a form of physical vapour deposition that uses a focused electron beam within a vacuum environment to heat evaporation material. The e-beam evaporation process is based on the emission of electrons from a tungsten filament when exposed to a current. The electron gun system sends an electric current of sufficient energy, between five and ten kV, through the tungsten filament, which is located outside the deposition area. This high-voltage current heats the tungsten to high temperatures, allowing the thermionic emission of electrons to occur. The e-beam evaporator then uses permanent magnets or electromagnetic focusing to direct the high-energy electrons toward the target material, which is placed in a water-cooled crucible. As the crucible is bombarded with an electron beam, the kinetic energy is converted into thermal energy. This causes the material inside to evaporate, rise through the vacuum chamber and deposit onto the substrate as a thin layer. This focused, high kinetic energy can evaporate high melting point materials not capable of evaporation through traditional deposition methods. It can yield very high deposition rates at low substrate temperatures. This method of thermal evaporation is useful for deposit metals, refractory metals, optical thin films, and a range of other electron beam evaporation applications. The Main Advantages of Electron Beam Evaporation Electron beam evaporation offers excellent precision and versatility. It enables the vaporisation of materials with high melting points, such as tungsten and niobium, and provides exceptional control over the coating process. High-Temperature Thin Film Deposition One significant advantage of electron beam heating is the ability to work with higher deposition temperatures than traditional thermal evaporation. This method of evaporation can vaporise coating material metals with high melting temperatures, such as Tungsten Niobium Silicon dioxide Ruthenium Coating Control Electron beam evaporation allows for high material utilisation and is applicable across a broad range of evaporation materials. Using the electron beam allows for precise control over the deposition rate and monitoring of the growing film on the substrate. Using an electron beam evaporator enables you to create a coating that matches your desired properties, down to a fraction of a nanometre. Substrate Protection Processes like sputtering can cause damage to the substrate because the high-energy particles involved in the sputtering process can physically dislodge atoms from the substrate, leading to erosion or the implantation of unwanted materials. This action can also introduce thermal stresses due to the high kinetic energy of the particles impacting the substrate, potentially altering its physical and chemical properties. Electron beam evaporation, on the other hand, minimises damage to the substrate as it utilises an electron beam to heat and evaporate the source material in a vacuum. This method allows for more precise control over the deposition rate and substrate temperature, reducing the risk of thermal damage. Additionally, since the process is less aggressive compared to sputtering, there’s a lower likelihood of substrate alteration or damage from high-energy particle impacts. Applications Electron beam evaporation applications vary between ceramic coating deposition [2], the growth of zinc oxide thin films [3], creating coatings to protect surfaces in corrosive environments, and more. One of the most promising uses of electron beam evaporation is within laser optics. The thin films produced by this thermal deposition process are ideal for optical coatings, such as those on solar panels, eyeglasses, architectural glass, and more. Electron beam evaporation is also applicable in the aerospace and automotive industries. These industries often have high temperature requirements and strict guidelines for the wear resistance of their materials. Comparing Electron Beam With Other Thin-Film Deposition Processes A common question is, “How do I know if I should use e-beam over deposition methods?” The thin films deposited with different PVD techniques vary, as well as different procedures being suited to different coating materials. Take a look below to see common comparisons. E-Beam Evaporation vs Thermal Evaporation E-beam evaporation is used over thermal evaporation when high energy and precise control over the evaporation rate and substrate temperature are required. This method is particularly beneficial for materials that have very high melting points or those that are sensitive to thermal decomposition. With that being said, thermal evaporation is a great choice if you are working with materials that evaporate at lower temperatures and require a simpler, more cost-effective setup. Thermal evaporation can offer a uniform and high-quality coating for a wide range of materials, making it suitable for applications where material properties allow for its use. E-Beam Evaporation vs Sputtering Electron beam evaporation and sputtering both have a range of applications. However, electron beam physical vapour deposition allows for the vaporisation of high-melting-point materials with a relatively low deposition time [4]. E-beam evaporation is more suitable for high-volume batch production and thin-film optical coatings. While sputtering is applicable to some optical processes, its applications are more limited. As such, sputtering is more commonly used within applications requiring high levels of automation. FAQs About E-Beam Evaporation How Is Sputtering Different from Electron Beam Evaporation? While sputtering and e-beam evaporation are both forms of physical vapour deposition, their deposition processes differ significantly. Electron beam evaporation is a form of thermal evaporation. The thermal evaporation process focuses an electron beam on a source material to produce very high temperatures, allowing it to vaporise high-temperature materials. Meanwhile, magnetron sputtering collides positively charged energetic ions with a negatively charged target material, ejecting atoms from the target material and depositing them onto a substrate. Sputtering occurs within a closed magnetic field, while electron beam evaporation occurs within a vacuum or deposition chamber. Both sputtering and e-beam evaporation have a low level of impurity, but e-beam PVD has a higher deposition rate. However, sputtering has the highest rate of scalability, as it can be automated in many applications. In some cases, using ion-beam-assisted deposition, such as that involved in sputtering, can expand the functionality of thermal evaporation. Understanding the right evaporation system, or the right combination of systems is essential to optimising precision, functionality, and efficiency in your desired application. What Are the Disadvantages of E-Beam Evaporation? While electron beam PVD has some industrial applications, it is not suitable for coating the inner surface of complex geometries. Additionally, the filament degradation used within this vaporisation process can produce a non-uniform evaporating rate, producing less precise results than other methods. Evaporation deposition also has limited scalability with a lower utilisation and deposition rate. Further, this system is relatively complex, leading to a higher cost compared to other deposition methods, like pulsed laser deposition or chemical vapor deposition. Weighing up the advantages and disadvantages of this thermal evaporation technique can help you determine whether it is suitable for your application. References [1] Bashir, Almas, Iqbal Awan, TAhir, Tehseen, Aqsa, Bilal Tahir, Muhammad, Ijaz, Mosin. (2020, May 27). Interfaces and surfaces. Chemistry of Nanomaterials. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/pii/B9780128189085000032 [2] Shamala, K. S., Metzner, C., Maiti, N., Zhigarev, A. A., Evans, ?., Kanareykin, A. D., Ganz, S. N., Avdeeva, D. K., Garshin, A. P., Balkevich, V. L., Kunevich, A. V., … Hocking, M. G. (2017, June 19). Ceramic coating deposition by electron beam evaporation. Surface and Coatings Technology. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S025789721730645X [3] Caglar, M., Fang, G. J., Karuppasamy, A., Asmar, R. A., Zhu, B. L., Daniel, G. P., Fang, Z. B., Zhang, D. H., Chu, S. Y., Zhaoyang, W., Li, X. H., & Kim, D. C. (2011, March 29). Effect of heat treatment on characteristics of nanocrystalline ZnO films by electron beam evaporation. Vacuum. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S0042207X11001205[4] Maiti, N., Karmakar, P., Barve, U. D., & Bapat, A. V. (2008). An evaporation system for film deposition using electron beam sources. IOPScience. Retrieved December 28, 2022, from https://iopscience.iop.org/article/10.1088/1742-6596/114/1/012049

Written by Korvus Technology Published on November 10, 2022 Sputtering: What is it and how does sputter deposition work? Most people are familiar with the three states of matter: solid, liquid, and gas. However, gaseous plasma exists as a state apart. This unique dynamic condition creates a flux of neutral gas atoms coexisting with electrons, photons, and accelerated ions in the same space. Since plasma consists of unstable high-energy particles (i.e., ions and electrons), it needs an external energy source like powerful voltages or high temperatures. Gas plasma has many uses across different industries, one of which is a surface modification by sputter deposition. Physical sputtering[1] is a thin film creation method that directs accelerated ions from the source material onto a target surface to create a coating. This technique has applications in the semiconductor industry and solar panels, disk drives, optical devices, and other major industries. This overview covers the basics of the sputter deposition method and its advantages compared to other deposition methods. What Does Sputtering Mean? The word “sputtering” originates from the Latin “Sputare,” which means “to spit out noisily.” You may picture a spray fountain made up of tiny moist particle flux. While crude, this image depicts the gaseous plasma-based sputter remarkably well. People who deal with car mechanics may also associate “sputter” with the series of explosive noises an engine makes when it overheats and is about to give out. In industrial physics, however, the meaning of “sputtering” has an entirely different context. This process is one of many forms of Physical Vapour Deposition (commonly refer as PVD). One of its most widely used alternatives is the thermal deposition method. Sputtering is a process that enables the creation of film coating made of sputtered atoms. Without this method, it would be nearly impossible to attain the high-quality coating films necessary for LED displays, optical filters, precision optics, and more. Plasma sputter began in 1970 [2] when Peter J. Clarke presented the first sputtering device that used electron and ion collisions to deposit an atom scale coating on a target surface. Today, more than five decades later, thin film applications form an inseparable part of aerospace, solar energy, microelectronics, automotive, and other industries. The Sputtering Process The sputtering process starts with placing the substrate (the surface that requires a coating) in a vacuum chamber filled with inert gas atoms. The source material, which will transfer onto the substrate, then receives a negative charge and becomes a cathode. This causes free electrons to flow from the charged source materials. These electrons collide with the outer electrons surrounding the gas atom, which has the same negative charge, driving the gas electrons off. Once it loses electrons, a neutral atom turns into a high-energy ion. When the cathode target is bombarded, electrons get knocked out due to the collisions, and the gas atoms turn into positively charged ions. The negatively charged source material attracts these positive ions, which fly at it with such high velocity that atomic-sized particles “sputter off,” or detach. Finally, the sputtered particles cross the vacuum chamber and start landing on the substrate surface as a growing film made of ejected target ions. How Does Sputtering Work? Sputter systems come in different sizes, depending on the industry application. The process happens in a vacuum chamber. Glass (e.g., architectural glass, solar cells, and so on) is the most common substrate for the film coating. Korvus Technology manufactures the HEX Series, a sputtering system capable of several thin film deposition techniques. The sputter coating is one of the most common applications of this incredibly versatile and efficient system. What Is a Sputtering Target? The film material source is a rotary target made of metal, ceramic, or even plastic. As an example, let’s take a molybdenum target. Molybdenum often functions in producing conductive thin films in displays or solar cells. Throughout the process, pumps keep removing air to create a vacuum environment. The base pressure in the chamber is around 10 to -6 millibar or about a billionth part of the normal atmospheric pressure. Inert gas atoms flow continuously into the deposition chamber, creating a low gas pressure atmosphere. In physical vapour deposition,[3] a magnet array may sit inside the cylindrical target, releasing a magnetic field. Cooling water inside the target cylinder dissipates the heat generated in the process. How does a sputter coater work? Under high voltage, the molybdenum target creates a gaseous plasma, which concentrates along with the magnetic fields. The plasma consists of gas atoms, free electrons, and positively charged argon ions. Continuous electron collisions with the argon atoms keep producing positively charged ions. Since the target surface, or the cathode, is negatively charged, its binding energy attracts the energetic ions. As the target gets bombarded, ions displace atoms. You could think of it as a billiard ball that collides with another ball and sends it rolling. The sputtered atoms gradually settle on the glass substrate, or the anode, which sits opposite the target. Layer by layer, these ejected atoms form a thin film. This process’ deposition rate calculation depends on various factors, such as the target material’s physical properties, the current, and beam energy. Target Surface Quality Ions that hit the target surface don’t distinguish between the desired target atoms (e.g., molybdenum) and any impurities with the same charge. Any atoms that get ejected may consist of both. If the target surface contains impurities, they may end up on the substrate as sputtered atoms and compromise the thin film properties, such as its electrical conductivity. To ensure high-quality thin film, the process must use a highly pure target by a trustworthy manufacturer as well as high-performing equipment. The Role of Argon Argon works well in sputter systems because it is an inert gas with high-mass ions. However, the reactive method may also use a non-inert gas, such as oxygen or nitrogen. In reactive setups, gas ions recombine with the target material to produce the deposited film. Ion Beam Sputtering Ion beam sputtering is a thin film deposition method in which an ion source sputters a target metal or dielectric material onto a substrate. The monoenergetic and highly collimated properties of the ion beam enable precise control of film growth. The result is a highly dense, superior quality film. DC vs RF Sputtering DC sputtering uses a DC (Direct Current) power source. This method is widely used, effective, and economical. It allows the processing of large substrate quantities. The RF sputtering method uses a high voltage AC (Alternating Current) power source and works for both conductive and non-conductive sputtered material. The RF stands for radiofrequency. This technique is more expensive and has a lower sputter yield, making it more suitable for lower substrate sizes. Magnetron Sputtering Magnetron sputtering[4] relies on magnetic fields to control the velocity and direction of charged ion particles from the magnetron sputtering source. Although diode sputtering can yield atomic-scale thin films, it is a slow process that works best with a limited-size substrate. Moreover, particle bombardment can cause overheating and damage the substrate. In magnetron sputtering, magnets placed behind the cathode will trap electrons and prevent them from bombarding the substrate, creating faster deposition. Benefits of Magnetron Sputter Deposition Unlike other technologies, magnetron sputtering does not call for the source materials’ melting and evaporation. This process works for nearly all materials, regardless of melting temperature. The magnetic field technique allows the use of compounds and alloys as magnetron sputtering sources while maintaining their composition as similar as possible. The Advantages and Applications of Sputtering Deposition Sputter deposition can only occur when the bombarding particles have extremely high kinetic energy, which allows the creation of gas plasma. This method enables a pure and accurate atomic-level film deposition, infinitely superior to any conventional thermal energy techniques. The energy transfer of the bombarding particles,[5] the target atom and ion relative masses, and the target atoms’ surface binding energy all control the sputter yield, which is the average number of atoms that fly off from the source material. The process yield’s outstanding precision and constant rate allow the exact programming of the sputtering coating thickness. Compared to other deposition methods such as thermal evaporation, sputtering works well with a broader range of materials, including diverse mixtures and alloys. Its higher energy transfer produces better surface adhesion, more uniform films, and higher packing densities, even at low temperatures. Many industries rely on high-quality thin films produced by the aforementioned deposition methods. Here are just a few examples: The optoelectronics industry, such as optical filters and precision optics Medical devices and implants Consumer electronics and LED displays Fibre lasers and semiconductor lasers Microscopy and microanalysis sample slides Sputtering film deposition is a diverse field with many methods and techniques. It includes RF and DC magnetron sputtering, ion beam sputtering, reactive sputtering, and more. Final Words The sputtering deposition has brought innovation and superior performance to a wide array of industries. The method comprises many sub-techniques, all of which use high-energy collisions to create a thin, precise coating of material. Magnetron sputter deposition further expanded the range of applications and substrates. The final film quality depends on several factors, including target material properties, process methodologies, and sputtering system performance. Are you interested in learning more about sputtering? We invite you to read other blog articles from Korvus Technology, manufacturer of the innovative HEX Series of modular thin film deposition systems that use physical vapor deposition methods. References [1] Berg, S., et al. Fundamental understanding and modeling of reactive sputtering processes. Thin Solid Films Volume 476, Issue 2, 8 April 2005, Pages 215-230. [2] Greene, J. E. Review Article: Tracing the recorded history of thin-film sputter deposition: From the 1800s to 2017. Journal of Vacuum Science & Technology, Volume 35, Issue 5, 10 May 2017. [3] Rossangel, S. M. Thin film deposition with physical vapor deposition and related technologies. Journal of Vacuum Science & Technology, Volume 21, Issue 5, 17 June 2003. [4] Safi, I. Recent aspects concerning DC reactive magnetron sputtering of thin films: A review. Surface and Coatings Technology, Vol 127, Issues 2-3, 22 May 2000, Pages 203-218. [5] Mattox, D. M. Particle bombardment effects on thin‐film deposition: A review. Journal of Vacuum Science & Technology, Volume 7, Issue 3, 04 June 1998.