Essential Terms for Sputtering and Evaporation Processe

Terminologies of Sputtering Coating

General Term

  1. Vacuum deposition: A group of methods used to deposit layers of material under a vacuum.
  2. Substrate: The material on which the film is deposited.
  3. Coating material: The raw material used to deposit the film, including sputtering targets and evaporation pellets materials.
  4. Sputtering target: A coating material used for sputtering in vacuum sputtering.
  5. Sputtering rate: The amount of sputtering material used over a given time interval divided by the time interval.
  6. Deposition rate: The amount of material deposited on the substrate over a given time interval divided by the time interval and the surface area of ​​the substrate.

Information from SAM Sputter Target, a global coating materials supplier.

Technical Terminology

  1. Vacuum sputtering: The process by which inert gas ions bombard atoms (molecules) or radicals from the target surface in a vacuum.
  2. Reactive vacuum sputtering: Vacuum sputtering of film material of a desired chemical composition by reaction with a gas.
  3. Direct current diode sputtering: A direct current voltage between two electrodes causes the gas to self-sustain and discharge the target as a cathode.
  4. High-frequency diode sputtering: A high-frequency discharge is obtained by a high-frequency voltage between two electrodes to cause sputtering of a negative potential at a target.
  5. Ion beam sputtering: An ion beam obtained by a special ion source causes the sputtering of a target.
  6. Magnetron sputtering: The secondary electrons are bound to specific areas of the target surface using an orthogonal electromagnetic field formed on the surface of the target to enhance ionization efficiency and increase ion density and energy. Therefore, a very high sputtering rate can be obtained at a low voltage and a large current.

Special Parts

  1. Sputtering device: The components of a vacuum sputtering apparatus including a target and an auxiliary device necessary for sputtering (for example, a power supply device, a gas introduction device, etc.).
  2. Sputtering Target: The surface is bombarded with particles. The meaning of the target in this standard is the electrode composed of the sputtering material in the sputtering apparatus.
  3. Shutter: A device used to limit the coating in time and/or space and thereby achieve a certain film thickness distribution. The baffle can be either fixed or movable.
  4. Mask: A device used to cover part of the substrate and to limit the coating in space.
  5. Substrate heating device: A device that can heat a substrate or substrates to the desired temperature by heating in a vacuum coating device.
  6. Substrate cooling device: In a vacuum coating device, a device achieves the desired temperature by cooling a substrate or substrates.

Terminologies of Vacuum Evaporation

General Term

  1. Vacuum coating: A method of making a film on a substrate under vacuum.
  2. Substrate: The surface on which the film is deposited.
  3. Testing substrate: A substrate used for measurement and/or testing at the beginning of coating, during the coating process, and after coating.
  4. Coating material: The raw material used to make the film, mainly including sputtering targets and evaporation pellets materials.
  5. Evaporation material: A coating material used for evaporation in vacuum evaporation.
  6. Film material: the material constituting the film layer.
  7. Evaporation rate: the amount of material evaporated during a given time interval divided by
  8. Deposition rate: The amount of material deposited on a substrate over a given time interval divided by the time interval and the surface area of ​​the substrate.
  9. Coating angle: The angle between the direction of the particles incident on the substrate and the normal to the surface being plated.

Information from SAM Sputter Target, a global coating materials supplier.

Technical Terminology

  1. Vacuum evaporation coating: A vacuum coating process for evaporating a coating material.
  2. Simultaneous evaporation: Vacuum evaporation of various evaporation materials simultaneously onto the substrate by several evaporators.
  3. Evaporation field evaporation: Evaporation of a material evaporated from the evaporation field onto a substrate for evaporation (this process is applied to large-area evaporation to obtain a desired film thickness distribution).
  4. Reactive vacuum evaporation: Vacuum evaporation of film material of a desired chemical composition by reaction with a gas.
  5. Reactive vacuum evaporation in evaporator: Reacts with various evaporation materials in the evaporator to obtain vacuum evaporation of the desired chemical composition film material.
  6. Direct heating evaporation: The heat necessary to evaporate the evaporation of the material is the same as the heat of the evaporation material (in the crucible or not).
  7. Induction heating evaporation: The evaporation material is heated by induction eddy current.
  8. Electron beam evaporation: evaporation of heated material by electron bombardment.
  9. Laser beam evaporation: evaporation of the material by laser beam heating.
  10. Indirect heating evaporation: In a heating device (for example, a boat-shaped evaporator, a crucible, a filament, a heating plate, a heating rod, a spiral coil, etc.), the evaporation material is subjected to the heat necessary for evaporation, and is transferred to the evaporation material by heat conduction or heat radiation.
  11. Flash evaporation: intermittently evaporate a very small amount of evaporating material.

Special Parts

  1. Coating chamber: A part of a vacuum coating equipment that performs the actual coating process.
  2. Evaporator device: A vacuum coating device that includes an evaporator and all components necessary for its operation (such as power supply, supply, cooling devices, etc.).
  3. Evaporator: A device that evaporates directly within it, such as a boat-shaped evaporator, crucible, filament, heating plate, heating rod, spiral coil, etc., and if necessary, the evaporation material itself.
  4. Evaporator by direct heat: An evaporator in which the evaporation material itself is heated.
  5. Evaporator by indirect heat: An evaporator in which an evaporation material is heated by heat conduction or heat radiation.
  6. Evaporation field: A field formed by heating the same vaporized material by several arrays of evaporators.

The Benefits of Using Chromium Pellets for Thermal Evaporation in Manufacturing

Manufacturing processes have always been evolving, and with the advancements in technology, companies are constantly looking for ways to improve efficiency and reduce costs. One such method that has gained popularity in recent years is the use of chromium pellets for thermal evaporation. These pellets, made of high-purity chromium metal, are used in vacuum deposition processes to create thin films on various substrates. The benefits of using chromium pellets for thermal evaporation are numerous, including improved film quality, reduced manufacturing costs, and increased production rates.

In this article, we will explore the advantages of using chromium pellets in manufacturing and why it has become the preferred method for many industries. So, let’s dive in and discover the world of thermal evaporation and the benefits of using chromium pellets.

What are Chromium Pellets for Thermal Evaporation?

Chromium pellets are small, cylindrical-shaped pieces of high-purity chromium metal that are used in thermal evaporation. Thermal evaporation is a vacuum deposition process, where a material is heated to its evaporation point, and the vaporized material is condensed onto a substrate to form a thin film. Chromium pellets are one of the most popular evaporation materials used in the manufacturing industry, as they offer several advantages over other materials commonly used for thermal evaporation.

Advantages of Using Chromium Pellets

There are several advantages of using chromium pellets for thermal evaporation. The first advantage is improved film quality. Chromium pellets produce high-quality films with excellent adhesion, uniformity, and smoothness. The films produced using chromium pellets are also very stable and have good chemical and mechanical properties, making them ideal for a wide range of applications.

The second advantage of using chromium pellets is reduced manufacturing costs. Chromium pellets have a high evaporation rate, which means that less material is needed to produce the same amount of film. This results in reduced material costs, as well as reduced energy costs, as less energy is required to evaporate the material.

The third advantage is increased production rates. Due to its high evaporation rate, more chromium pellets can be evaporated in a shorter amount of time. This results in increased production rates, which can help companies meet their manufacturing goals faster and more efficiently.

Properties of Chromium Pellets

Chromium pellets are made of high-purity chromium metal, which means that they have excellent physical and chemical properties. Chromium is a hard, lustrous metal that has a high melting point and is resistant to corrosion. Chromium pellets are also very stable and have good mechanical and chemical properties, making them ideal for a wide range of applications.

Comparison of Chromium Pellets with Other Evaporation Materials

Chromium pellets are one of the most popular evaporation materials used in the manufacturing industry, but there are several other materials that are also commonly used. These include aluminum, gold, silver, and copper, among others. While each of these materials has its own advantages and disadvantages, chromium pellets are often preferred due to their excellent film quality, reduced manufacturing costs, and increased production rates.

Applications of Chromium Pellets in Manufacturing

Chromium pellets are used in a wide range of manufacturing applications. Some of the most common applications include the production of thin films for electronics, optics, and solar cells. Chromium pellets are also used in the production of decorative coatings, as well as in the production of hard coatings for cutting tools, molds, and dies.

How to Use Chromium Pellets for Thermal Evaporation

Using chromium pellets for thermal evaporation is a relatively simple process. The first step is to load the pellets into a crucible, which is then placed into the evaporation system. The system is then evacuated to a high vacuum, and the pellets are heated to their evaporation point using an electron beam or resistive heating. The vaporized material is then condensed onto a substrate to form a thin film.

Maintenance and Storage of Chromium Pellets

To ensure the longevity and optimal performance of chromium pellets, proper maintenance, and storage are essential. Chromium pellets should be stored in a dry, cool place, away from moisture and other contaminants. When not in use, the pellets should be stored in an airtight container to prevent oxidation. Before use, the pellets should be cleaned using a mild solvent to remove any surface contaminants.

Where to Buy Chromium Pellets for Thermal Evaporation

Chromium pellets for thermal evaporation can be purchased from a wide range of suppliers. It is important to choose a reputable supplier that offers high-purity chromium pellets that are free from contaminants. One of the most popular suppliers of chromium pellets is Stanford Advanced Material (SAM).


In conclusion, using chromium pellets for thermal evaporation is a highly effective method for producing high-quality films in a wide range of manufacturing applications. The benefits of using chromium pellets include improved film quality, reduced manufacturing costs, and increased production rates. With proper maintenance and storage, chromium pellets can provide optimal performance and longevity, making them an excellent investment for any manufacturing company.

Understanding the Mechanisms of Vacuum Evaporation Coating

Vacuum evaporation coating is a common method used to deposit thin films onto a substrate. This technique is widely used in a variety of industries, such as electronics, optics, and aerospace, due to its ability to create precise and uniform coatings with a high level of purity. There are several mechanisms used to achieve vacuum evaporation coating, each with its own advantages and limitations.


One common method is resistance evaporation, which uses a resistance evaporation source made of tungsten, molybdenum, or tantalum to evaporate low melting point materials such as gold, silver, zinc sulfide, magnesium fluoride, chromium oxide, and others. However, this method may not meet the needs of vapor deposition of certain metals and non-metals.


Electron beam evaporation is another technique used for vacuum evaporation coating. It involves heating the evaporating material with an electron beam, which can provide a much larger energy density than the resistance heat source. This allows for the heating of refractory metals and non-metallic materials such as tungsten, molybdenum, niobium, SiO2, AI2O3, and others. Additionally, the material to be vapor-deposited is placed in a water-cooled crucible, which helps to avoid evaporation of the container material and reaction between the container material and the membrane material, thus improving the purity of the membrane.

Various Types of Evaporation Pellets Materials


High-frequency induction heating evaporation is another method used for vacuum evaporation coating. The metal is heated to the evaporation temperature using the principle of induction heating. The crucible containing the evaporation material is placed in the center of the spiral coil, and a high-frequency current is passed through the coil to heat the metal evaporation material until evaporation. This method has a large evaporation rate, uniform and stable evaporation source temperature, easy temperature control, and requires less purity of the evaporation materials.


Arc heating evaporation uses the arc discharge heating method, which is similar to the electron beam heating method. This method is particularly suitable for evaporation of refractory metals and graphite that have a high melting point and a certain conductivity. It also has the advantage of being relatively inexpensive compared to the electron beam heating apparatus.


In conclusion, vacuum evaporation coating is a versatile and widely used technique for depositing thin films onto a substrate. There are several methods used to achieve this, each with its own advantages and limitations. By understanding the different mechanisms of vacuum evaporation coating, researchers and industry professionals can choose the appropriate method to achieve the desired coating properties for their specific applications.

If you want to learn more about sputtering targets, such as metals, alloys, oxides, and ceramic materials, you can visit the website of Stanford Advanced Materials (SAM) Corporation at SAM is a global supplier of various sputtering targets and regularly updates their knowledge and interesting stories related to sputtering targets on their website.

Application and Recycling of Tungsten Metals

Tungsten, a relatively rare and exotic metal, has been widely used in many products in our daily life. Tungsten has the advantages of high melting point, high hardness, excellent corrosion resistance, and good electrical and thermal conductivity. Most of its applications are based on these properties. Tungsten is not cheap because of its scarcity, but the price of tungsten is quite reasonable compared with the prices of other rare and exotic metals.

What are the Applications of Tungsten?

Tungsten is an important alloying element for the aerospace industry and the industrial gas turbine industry, because it can significantly improve the strength, hardness, and wear resistance of steel.

Tungsten filament is used in incandescent bulbs to replace tantalum, which was used many years ago, as an integral part of copper and silver electrical contacts for improved wear resistance.  Tungsten wire can also be used to manufacture direct heating cathodes and grids of electronic oscillation tubes and cathode heaters in various electronic instruments.

Tungsten sputtering target & Ta evaporation pellets can be used as wear-resistant coatings for mechanical parts, as evaporating filaments for physical vapor deposition (PVD) of aluminum and silver, and as key barrier electrons for barrier coatings in critical electronic devices.

Some of the other applications of Tungsten include the component of chemicals and catalysts, cutting blades, paints, pigments, inks, lubricants, etc.

How to Recycle Tungsten?

Tungsten’s unique properties of heavy weight, high hardness, and high melting point make tungsten waste ideal for recycling. The fact that it is chemically resistant is a key factor in tungsten recycling. Therefore, recycling tungsten-bearing scrap is more popular. The methods of tungsten recycling can be roughly divided into the direct method and the indirect method.

Direct Tungsten Recycling

The direct method means that the tungsten waste is converted into a powder of the same composition by chemical or physical treatment or a combination of both. A typical example of a direct method is a zinc treatment method. This method has many advantages, such as limited energy consumption and chemical waste, as well as low production costs. A disadvantage of this method is the limitation on recycled materials.

Indirect Tungsten Recycling

Indirect methods, such as wet chemical processing, are commonly used in refining processes. This type of recycling has no restrictions on materials, but requires a lot of chemicals and energy.

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History of Thermal Evaporation for Thin Film Coating

Thermal evaporation, or vacuum evaporation, refers to the vaporization of evaporation materials. By heating evaporation materials to a certain temperature, the vapor pressure becomes appreciable, and the surface or molecules are lost from the surface in the vacuum. Vaporization can come from the surface of a liquid or from the surface of a solid. The equilibrium vapor pressure (EVP) is 10-2 Torr. Some evaporation materials have a vapor pressure so that they can sublime or evaporate (e.g., titanium) at temperatures near their melting points. Some composites sublime and some evaporate.

Thermal Evaporation Materials. (Gold, Silver, Titanium, Silicon Dioxide, Tungsten, Copper)
Thermal Evaporation Materials. (Gold, Silver, Titanium, Silicon Dioxide, Tungsten, Copper)

From late 1800s to early 1900s

Studies about thermal evaporation in vacuum began in the late 19th century. In the 1880s, H. Hertz and S. Stefan determined the equilibrium vapor pressure, but they did not consider using of vapor to form thin films.
In 1884, Thomas Edison applied for a patent covering the vacuum evaporation of “heating to incandescence” and film deposition. However, his patent makes no mention of the evaporation of molten materials, and many materials do not evaporate at an appreciable rate until they reach or exceed their melting point. Edison did not use the process in any application, presumably because radiant heating from the source was detrimental to the vacuum materials available at the time.


In 1887, Nahrwold reported the formation of platinum thin films by subliming platinum evaporation materials in a vacuum. Therefore, some believe that he was the first to use thermal evaporation to form thin films in a vacuum.

In 1907, Soddy proposed that it would be possible to evaporate solid calcium onto the surface to reduce the residual pressure in the sealed tube. This is believed to be the first “reactive deposition” process in history.

In 1909, Knudsen proposed the “Knudsen Cosine Distribution Law” for vapor from a point source. After 6 years, he refined the free surface evaporation rate as a function of equilibrium vapor pressure and ambient pressure. The resulting equation is called the Hertz-Knudsen surface equation for free-surface vaporization. Honig summarized the equilibrium vapor pressure data for 1957.

Various Types of Evaporation Pellets
Various Types of Evaporation Pellets

From the early 1900s to the mid-1900s

In 1912, von Pohl and Pringsheim reported the formation of thin films by evaporating solid materials in a vacuum using a magnesia crucible as a container. Their experiments are sometimes considered the first thin-film deposition by thermal evaporation in a vacuum.

In 1931, Ritschl reported thermal evaporation of silver from a tungsten wire basket to form half-silvered mirrors. And he is often credited with being the first to use evaporation from a filament to form a film in a vacuum.

Evaporating Aluminum Thin-Film

Cartwright and Strong reported on the evaporation of metals from tungsten wire baskets in the same year. However, their attempts to vaporize aluminum failed, because molten aluminum would wet with the tungsten filament to form an alloy, which causes it to “burn out” when there is a relatively large volume of molten aluminum.

Aluminum thin films were not successfully produced by vacuum evaporation until 1933, when John Strong used large gauge tungsten filaments wetted by molten aluminum. John has done extensive development work for astronomical mirror coatings using the aluminothermic evaporation of multiple tungsten wires. Strong, with the help of designer Bruce Rule, used multiple filaments and a 19-foot diameter vacuum chamber to aluminize the 200-inch Palomar telescope mirror in 1947.

AR Coating

In 1933 A.H. Pfund vacuum-deposited the first single-layer (AR) coating (ZnS) while reporting on making beamsplitters and Bauer mentioned AR coatings in his work on the properties of alkali halides.

The Germans deposited CaF2 a nd MgF2 AR coatings during WWII. Plasma cleaning of glass surfaces is reported to have been used by Bauer at the Zeiss Company in 1934. The Schott Company (Germany) was also reported to have deposited three-layer AR coatings by flame-pyrolysis CVD during WWII.

In 1935, based on Bauer’s observation, A. Smakula of the Zeiss Company developed and patented AR coatings on camera lenses. The patent was immediately classified as a military secret and was not revealed until 1940.

In1936, Strong reported depositing AR coatings on glass.

In 1939, Cartwright and Turner deposited the first two-layer AR coatings.

One of the first major uses of coated lenses was on the projection lenses for the movie Gone With the Wind, which opened in December 1939. The AR-coated lenses gained importance in WWII for their light-gathering ability in such instruments as rangefinders and the Norden Bombsight.

The AR coated lenses gained importance in WWII for their light-gathering ability in such instruments as rangefinders and the Norden Bombsight. During WWII, baking of MgF2 films to increase their durability was developed by D.A. Lyon of the U.S. Naval Gun Factory. The baking step required that the lens makers coat the lens elements prior to assembly into compound lenses.

In 1943, the U.S. Army sponsored a conference on “Application of Metallic Fluoride Reflection Reducing Films to Optical Elements.” The proceedings of this conference are probably the first extensive publication on coating optical elements.

In 1958, the U.S. military formally approved the use of “vacuum cadmium plating” (VacCad) for application as corrosion protecmium. In recent years Physical Vapor Deposition (PVD) methods have been used to replace electroplating in a number of applications to avoid the water pollution associated with electroplating.

From the mid-1900s to the late 1900s

E-beam Evaporation Development

In 1949, Pierce described the “long-focus” electron beam gun for melting and evaporation in a vacuum. The long focus gun suffers from shorting due to the deposition of evaporated material on the filament insulators that are in the line of sight of the evaporating material. Deposition rates as high as 50 µm/s have been reported using e-beam evaporation. To avoid exposure of the filament to the vapor flux, bent-beam electron evaporators were developed.

In 1951, L. Holland patented the use of accelerated electrons to melt and evaporate the tip of a wire (“pendant drop”), which involved no filament or crucible.

In 1968, Hanks filed a patent on a 270° bent beam electron beam evaporation source that has become the most widely used design. Mastering the electron beam allows the energy of the electron beam to be distributed over the surface.

In 1970, Kurz was using an electron-beam system to evaporate gold for web coating. In electron beam evaporation a high negative “self-bias” can be generated on the surface of an insulating material or on an electrically isolated fixture. This bias can result in high-energy ion bombardment of the self-biased surface.

In 1971, Chambers and Carmichael avoided that problem by having the beam pass through a small hole in a thin sheet in a section of a plate that separated the deposition chamber from the chamber where the filament was located. This allowed a plasma to be formed in the deposition chamber while the filament chamber was kept under a good vacuum. The plasma in the deposition chamber allowed ion bombardment of the depositing film material as well as “activation” of reactive gas.

In 1972, the use of a hollow cathode electron emitter for e-beam evaporation was reported by J.R. Morley and H. Smith.

In 1978 H.R. Smith described a unique horizontally emitting electron beam (EB) vapor source. The source used a rotating crucible to retain the molten material, and its function was to coat large vertical glass plates. A number of thermoelectron-emitter e-beam source designs followed, including rod-fed sources and “multi-pocket” sources. The high voltage on the filament prevented the source from being used in a plasma where ions accelerated to the cathodic filament; this caused rapid sputter-erosion of the filament.

Crucible material Development

In 1951 Picard and Joy described the use of evaporation of materials from an RF-heated crucible. In 1966 Ames, Kaplan, and Roland reported the development of an electrically conductive TiB/BN composite ceramic (Union Carbide Co., UCAR™) crucible material that was compatible with molten aluminum.

Directed Deposition Development

The directed deposition is confining the vapor flux to one axis by eliminating off-axis components of the flux. Directed deposition can be attained by the collimation of the vaporized material. This was done in evaporation by Hibi (1952), who positioned a tube between the source and the substrate. Collimation was also attained by H. Fuchs and H. Gleiter in their studies of the effects of atom velocity on film formation using a rotating, spiral-groove, velocity selector.

In 1983, Ney described a source that emitted a gold atom beam with a 2° divergence. Recently, “directed deposition” has been obtained using a flux of thermal evaporated material projected into a directed gas flow.

Thermally Evaporating Development

When thermally evaporating alloys, the material is vaporized with a composition in accordance with Raoult’s Law (1887). This means that the deposited film will have a continuously varying composition unless very strict conditions are met as to the volume of the molten pool using a replenishing source. One way of avoiding the problem is by “flash evaporation” of small volumes of material.

In 1948, L. Harris and B.M. Siegel reported flash evaporation by dropping small amounts of material on a very hot surface so that all of the material was vaporized before the next material arrived on the hot surface.

In 1964, Smith and Hunt described a method for depositing continuous strips of alloy foils by evaporation. Other free-standing thin-film structures are also deposited, such as beryllium Xray windows and nuclear targets.

To learn more about the history of thermal evaporation, please follow our website. We will update articles about evaporation pellets every week, so stay tuned. If you want to buy high-quality evaporating pellets, please visit our official website for coating materials at

Evaporation Coating Experiment: Principle, Purpose & Results


In recent years, the rapid economic development and the continuous improvement of people’s living standards have led to the continuous emergence of high-tech thin-film products, especially in the field of electronic materials and components. Vacuum coating technology has also gained significant application in this field.

At present, the common film-forming methods include vapor-phase film-forming method, oxidation method, ion implantation method, diffusion method, electroplating method, coating method, liquid-phase growth method, etc. The vapor generation method can be further subdivided into physical vapor deposition, chemical vapor deposition, and discharge polymerization.


The experiments listed in this article are related to physical vapor deposition coatings. This method is basically carried out under vacuum, so it is called vacuum coating technology.

Vacuum evaporation, sputter coating, and ion plating are commonly referred to as basic physical vapor deposition thin film preparation techniques. The vacuum evaporation coating method is a method in which the evaporation material of a film to be formed in a vaporization chamber is heated in a vacuum chamber, and atoms or molecules are vaporized from the surface to form a vapor stream, which is incident on the surface of the substrate and condensed to form a solid film.

Evaporation Coating


  1. To familiarize yourself with the operating procedures and methods obtained by vacuum;
  2. In order to understand the principle and method of evaporation coating;
  3. To learn how to use evaporation coating technology.


(1) Vacuum conditions during evaporation

When the average free path of the vapor molecules in the vacuum vessel is greater than the distance between the evaporation source and the substrate (called the steaming distance), sufficient vacuum conditions are obtained. For this reason, it is necessary to increase the mean free path of the residual gas to reduce the collision probability of the vapor molecules with the residual gas molecules, and to evacuate the vacuum chamber to a high vacuum.

(2) How to choose evaporation source selection

1 It should have good thermal stability, chemical inactivity; the vapor pressure of the heater itself is sufficient to reach the evaporation temperature.

2 Its melting point should be higher than the evaporation temperature of the evaporated material. The heater should have a large enough heat capacity.

3 The mutual melting of the evaporated material and the evaporation source material must be very low, and it is difficult to form an alloy.

4 The material used for the coil-shaped evaporation source is required to have a good wetting with the evaporation material and a large surface tension.

5 For a case where it is difficult to form a filament, or when the surface tension of the evaporation material and the filament evaporation source is small, a boat-shaped evaporation source can be used.

(3) Main physical processes of thermal evaporation coating

1 Using various forms of thermal energy conversion to vaporize or sublimate the coating material into gaseous particles (atoms, molecules or atomic groups) with certain energy (0.1~0.3eV);

2 Gaseous particles are transported to the substrate by a substantially collision-free linear motion;

3 Particles are deposited on the surface of the substrate and agglomerated into a film.

(4) Factors affecting the quality and thickness of vacuum coating

There are many factors affecting the quality and thickness of the vacuum coating, including the degree of vacuum, the shape of the evaporation source, the position of the substrate, and the temperature of the evaporation source. The solid matter has very low evaporation at normal temperature and normal pressure. The higher the degree of vacuum, the easier it is for the molecules of the evaporation source material to scatter away from the surface of the material. The fewer molecules in the vacuum chamber, the lower the probability that the evaporating molecules will collide with the gas molecules, so that the surface of the substrate can be reached unobstructed straight.

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Advantages of Sputtering Deposition and Vacuum Evaporation

For all devices, there is a need to go from semiconductor to metal. Thus we need a means to deposit metals, also called film coating. There are currently several methods for depositing metal thin film layers, and many of these techniques for metal deposition can also be used to deposit other materials.

1.) Physical Vapor Deposition (PVD)

2.) Electrochemical techniques

3.) Chemical Vapor Deposition (CVD)

This passage will talk about the advantages of two PVD methods: Sputtering and evaporation.

Sputtering Deposition

Magnetron Sputtering System

The plasma under high pressure is used to “sputter” metal atoms out of the “target”. These high-energy atoms are deposited on a wafer near the sputtering target material. Higher pressures result in better step coverage due to more random angular delivery. The excess energy of the ions also helps increase surface mobility (the movement of atoms on the surface).

Advantages: Better step coverage, less radiation damage than E-beam evaporation, easier to deposit alloys.

Disadvantages: Some plasma damage including implanted argon. Good for ohmics, not Schottky diodes.

Vacuum Evaporation

Evaporation (PVD)
Evaporation (PVD)

Evaporation is based on the concept that there exists a finite “vapor pressure” above any material. The material either sublimes (direct solid to vapor transition) or evaporates (liquid to vapor transition).

Advantages: Highest purity (Good for Schottky contacts) due to low pressures.

Disadvantages: Poor step coverage, forming alloys can be difficult, lower throughput due to low vacuum.

PVD Film Morphology

The three zone model of film deposition as proposed by Movchan and Demchishin
The three zone model of film deposition as proposed by Movchan and Demchishin

1.) Porous and/or Amorphous —> Results from poor surface mobility =low temperature, low ion energy (low RF power/DC bias or higher pressures=less acceleration between collisions).

2.) “T-zone”: Small grain polycrystalline, dense, smooth and high reflectance (the sweet spot for most metal processes) Results from higher surface mobility =higher temperature or ion energy

3.) Further increases in surface mobility result in columnar grains that have rough surfaces. These rough surfaces lead to poor coverage in later steps.

4.) Still further increases in surface mobility result in large (non-columnar) grains. These grains can be good for diffusion barriers (less grain boundary diffusion due to fewer grains) but pose problems for lithography due to light scatter off of large grains, and tend to be more rigid leading to more failures in electrical lines.

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Introduction to the Process and Steps of Evaporation Coating

The basic process flow for evaporation coating is:

Preparation before coating→ vacuum→ ion bombardment→ baking→ premelting→ evaporation→ removing parts→ film surface treatment→ finished product

1. Preparation before coating

The process includes vacuum chamber coating part cleaning, evaporation source making and cleaning, installation of evaporation source and evaporation materials.

The amount of bonding between the film layer and the surface of substrate is an important indicator of product quality. It is determined by many factors, and the surface treatment before coating is one of the most basic factors. If there is grease on the surface of the coating part, adsorbing water, dust, etc., it will reduce the bonding force of the film layer and affect the surface roughness. Cleaning is generally done by several methods: chemical degreasing, electrostatic dedusting and primer application.

According to the requirements of the product and the material of the coating parts, selecting the appropriate evaporation material is the basic condition for obtaining a high-quality film layer. For different evaporation materials, the corresponding evaporation source and the evaporation method should be selected.

The basic principle of selecting metal evaporation materials is: good thermal stability and chemical stability, high mechanical strength, low internal stress, and certain toughness, good bonding with primer, high reflectivity, and small gas release in vacuum; the material source is wide, the price is low, and it has a corresponding evaporation source.

2. Vacuum step

Open the cooling water valve, adjust to the required water pressure, turn on the main power supply, close the atmospheric valve leading to the vacuum chamber, close the pipeline valve, start the mechanical pump power supply, and open the pre-vacuum valve; At this time, the vacuum chamber is evacuated using a diffusion pump or a mechanical pump, and baking, pre-melting, and evaporation are performed when the degree of vacuum reaches a certain value.

3. Ion bombardment

In the glow discharge, the ion bombardment electrons obtain a high speed, and the negative charge is rapidly generated around the substrate due to the large mobility of the electron. Under the action of the negative charge attraction, the positive ion bombards the surface of the coating part, and the substrate. There is energy exchange on the surface, and a chemical reaction occurs between the adsorption layer of the coating member and the active gas to achieve the effect of cleaning the surface.
The conditions of ion bombardment are that the residual gas pressure is stable at 0.13~13Pa, the voltage is 1.5~10kV, and the time is 5~60min.

4. Baking

It can accelerate the rapid escape of the gas adsorbed by the coating parts or the clamp, which is beneficial to improve the vacuum degree and the film bonding force. When baking, it should be noted that the non-metal baking temperature is lower than the hot deformation temperature of the coating part by 20~30 °C, and the metal baking is generally not more than 200 °C.

5. Pre-melting

This step can remove the low melting point impurities in the evaporation material and the gas adsorbed in the evaporation source and the evaporation material, which is favorable for the smooth progress of evaporation. The pre-melted vacuum is generally 6.6 x 10-3 Pa. For materials with high hygroscopicity, it should be pre-melted repeatedly. The overall requirement is that the vacuum does not drop as the evaporating material warms to the evaporating temperature.

6. Evaporation

Evaporation technology has a great impact on film quality. There are different requirements for general metals, special metals and compound evaporating pellets. For example, some metal particles need to be evaporated quickly, while others are not suitable. The heating method and the shape of the evaporation source should also be different depending on the evaporation material.

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Image Gallery of SAM Evaporation Materials

High purity evaporation materials play a huge role in deposition processes to ensure high quality deposited film. Stanford Advanced Materials provides various evaporation materials for both thermal and e-beam evaporation, including metal and ceramic boats, filaments, crucibles and heaters, and e-beam crucible liners.

Introduction to Two Important Vacuum Coating Methods

In today’s electronics industry, many electronic components are manufactured using a vacuum coating process. Vacuum coating has become an indispensable technology for the manufacture of electronic components. The current vacuum coating technology is to evaporate and sputter a metal or alloy in a vacuum to deposit it on a substrate. Vacuum evaporation and magnetron sputtering coating are two main vacuum coating technologies.

Vacuum evaporation


In 1857, Michael Faraday first proposed the basic principle of vacuum evaporation. Later, in the 1930s, the oil diffusion vacuum pump was put into practical use, and it was mainly used to make the lens anti-reflection film. During the Second World War, the demand for materials from other optical machines increased, and vacuum evaporation also developed rapidly.


In a vacuum state, the evaporation pellets in the evaporation vessel is heated to cause atoms or molecules to escape and deposit on the surface of the evaporation material to form a solid film. Depending on the type of vapor deposition material or substrate, it can be classified into heating methods such as resistance heating, electron beam, high-cycle induction, and laser. The vapor deposition materials include metal evaporation materials such as aluminum, lead, gold, silver, platinum, and nickel, and materials capable of producing optical properties, and oxides and fluorides such as SiO2, TiO2, ZrO2, and MgF2 are mainly used. In addition to metal, vapor deposition can be used for resin and glass, and in recent years, continuous paper has also become vapor-depositable.


The device is simple and easy to operate; the film formation rate is fast and the efficiency is high.


The thickness uniformity of the film is not easy to control, the evaporation container has hidden dangers, the process repeatability is not good, and the adhesion is not high.

Magnetron sputtering coating


As a very effective thin film deposition method, magnetron sputtering technology has been widely and successfully applied in many fields, especially in the fields of microelectronics, optical films and material surface treatment, for thin film deposition and surface coating preparation. In 1852, Grove first described the physical phenomenon of sputtering. In the 1940s, sputtering technology began to be applied and developed as a deposition coating method. With the rapid rise of the semiconductor industry in the 1960s, this technology was widely used and widely used in the integrated circuit production process for depositing metal electrode layers of transistors in integrated circuits. The emergence and development of magnetron sputtering technology, and the use of reflective layers for CD production in the 1980s, the field of application of magnetron sputtering technology has been greatly expanded, and gradually become a common means of manufacturing many products, and in the last ten years, a series of new sputtering techniques were developed.


Electrons accelerate to the substrate under the action of an electric field. In this process, electrons collide with argon atoms to ionize a large amount of argon ions and electrons. Under the action of an electric field, argon ions accelerate the bombardment of the sputtering target, and sputter a large number of target atoms, and the target atoms are deposited on the surface of the substrate to form a film.


The process repeatability is good, the film has high purity, uniform film thickness and good adhesion.


The structure of the device is complicated, and once the sputtering target penetrates, the entire target is scrapped, so the utilization rate of the target is low. Using rotatory sputtering target can increase the utilization of the target.

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