The Role of Sputtering Targets in Vacuum Sputtering

Introduction to Vacuum Sputtering

Vacuum sputtering is a thin-film technology to deposit thin films and coatings by creating a sub-atmospheric pressure environment and an atomic or molecular condensable vapor source. The basic principle is to make argon (Ar) ions hit the surface of the sputtering target through glow discharge in a vacuum, so that the target atoms overflow and deposit on the substrate to form a thin film.

Most general metal materials use DC sputtering, while non-conductive ceramic materials use RF sputtering. The new sputtering coating equipment uses powerful magnets to accelerate the ionization of argon gas around the target material in a spiral shape, thereby increasing the probability of collision between the target material and argon ions, thereby increasing the sputtering rate.

Characteristics of Sputtering Coating Process

(1) It has a wide range of applications, and can make metal, alloy or insulator materials into thin films.

(2) Under proper setting conditions, multi-component targets can be made into thin films with the same composition.

(3) A mixture or compound of the target substance and gas molecules can be produced by adding oxygen or another reactive gas to the discharge atmosphere.

(4) The target input current and sputtering time are controllable, which is conducive to obtaining high-precision film thickness.

(5) Sputtering coating is more conducive to producing large-area uniform films than other processes.

(6) The sputtered particles are not affected by gravity, and the positions of the target and the substrate can be freely arranged.

(7) The bonding strength between the substrate and the film is more than 10 times that of the general evaporated film, and because the sputtering particles have high energy, the surface of the film is continuously diffused to obtain a hard and dense film. At the same time, high energy allows the substrate to obtain a crystalline film at a lower temperature.

(8) The nucleation density is high at the initial stage of film formation, and an extremely thin continuous film of 10 nm or less can be produced.

(9) The target has a long service life and can be continuously produced for a long time.

(10) The target can be made into various shapes, and with the special design of the machine, it can be controlled better and has the highest efficiency.

How Target Purity Affects Thin Film Quality

Many factors can affect the quality of a thin film, of which the purity of the sputtering target has the greatest impact. If the target material is not pure enough, the impurity particles in the target material will adhere to the surface of the substrate during the sputtering process, causing the film layer in some positions to be weak and peel off. Simply put, the higher the purity of the target material, the better the performance of the film.

For targets with poor thermal conductivity, such as silicon aluminum sputtering targets, the heat transfer is often hindered by impurities in the target. There is a difference between the cooling water temperature used in production and the actual water temperature of the coating line, which leads to cracking of the target during use. Generally speaking, slight cracks will not have a great impact on coating production. However, when the target has obvious cracks, the charge is easily concentrated on the edge of the crack, resulting in abnormal discharge on the surface of the target. Discharging will lead to slag falling, abnormal film formation, and increased product scrapping. Therefore, in the process of target preparation and purity control, it is also necessary to control the preparation process conditions.

Stanford Advanced Materials (SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs. Please visit https://www.sputtertargets.net/ for more information.

 

3 Minutes to Know PVD Gold Sputtering

Gold is a popular precious metal that has been used for centuries as currency, hedging and jewelry for its noble and beautiful gold color.

PVD Gold Sputtering

Gold sputtering coating is a thin film deposition process in which gold or gold alloy is bombarded with high-energy ions in a vacuum chamber, causing gold atoms or molecules to be “sputtered” into the vapor and condensed on the substrate to be coated. Sputtering is one method of the PVD (Physical Vapor Deposition) process, the other two of which are thermal evaporation deposition and electron beam vapor deposition, and gold is also applied in these two methods. In thermal evaporation deposition, gold evaporates in a low-pressure environment with resistive heating elements; and in electron beam vapor deposition, gold is heated by an electron beam, and then condensed on the substrate to be coated.

Gold Plating

Apart from PVD coating, there are other ways for gold coatings such as gold plating and gold filling. Gold plating is a method that deposits a thin layer of gold on the surface of another metal by chemical or electrochemical plating. The advantages of gold plating are inexpensive and easy. However, the coating it produces is relatively soft and less durable, and what’s worse, its chemical process would cause pollution that is far away from environmentally friendly.

Gold Filling

Gold filling is the mechanical bonding of gold to metal under high temperatures and pressure. It produces a thicker coating than PVD gold sputtering and gold plating, and thus it is usually more expensive.

Advantages of PVD gold sputtering

The constant contact of skin or clothing may abrade the coatings, especially in the watch and jewelry industry. Thus, PVD gold sputtering is preferred in these two industries because the coatings it produces are harder and more durable than that of electrolytic gold plating or gold filling.

Compared to other types of gold coatings, the main advantages of PVD gold sputtering coating are their durability, retention of gloss, corrosion resistance, and abrasion resistance in contact with the skin, thus extending the life of the jewelry. PVD gold sputtering not only provides the exact color and brightness which evokes the general feeling of love and attraction with jewelry, but also has the advantage of being more environmentally friendly and durable than gold plating or gold filling for producing a gold coating.

Stanford Advanced Materials(SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs.

Selection of Common Coating Types of PVD Coating

Physical Vapor Deposition (PVD) is a thin film preparation technique that physically vaporizes the surface of a material source (solid or liquid) into gaseous atoms, molecules, or partially ionized into ions under vacuum conditions. [1]

Achieving a cost-effective application of the coating depends on a number of factors, and for each particular processing application, there is typically only one or several possible coating options. The choice of coating and its characteristics correctly determines the difference between a significant increase in processability and little improvement. Therefore, it is necessary to select a suitable coating according to detailed parameters such as the processing speed, the cooling method, the material to be processed, and the processing method. The following is our recommended coating selection:

TiN

TiN is a versatile coating that increases tool hardness and has a higher oxidation temperature.

Uses: high-speed steel cutting tools, slow processing tools (such as low-speed turning tools), wear parts, injection molds.

TiCN

The TiCN coating is based on the addition of carbon to the TiN to increase the hardness and low coefficient of friction of the coating.

Uses: high-speed steel tools, stamping dies, forming dies

TiAlN, AlTiN

The alumina coating formed by the TiAlN/AlTiN coating during processing can effectively improve the high-temperature processing life of the processing tool. The high-temperature oxidation resistance of the AlTiN coating is about 100 degrees higher than that of TiAlN.

Uses: Carbide tools (TiAlN is recommended when the hardness of the processed material is lower than HRC45 and AlTiN is recommended when the hardness of the processed material is higher than HRC45), thin-walled stamping die (TiAlN), die-casting die (AlTiN)

CrN

CrN coating has good adhesion, corrosion resistance, and wear-resistance.

Uses: processing aluminum alloy, red copper cutter, injection mold, parts (especially with lubricating oil soaking)

CBC(DLC)

The PLATIT CBC coating is composed of a TIN+TICN+DLC structure. It has the advantages of low friction coefficient, wear-resistance, and low stress of the film layer.

Uses: Lubricating coatings, forming dies, aluminum alloys, and other bonding materials stamping dies.

Apart from features and uses, different coating materials also show different colors. If you require the specific color of your coating, you can refer to the sheet below to choose your desirable coating materials.

PVD Coating Colors

Stanford Advanced Materials(SAM) supplies high-quality and consistent products to meet our customers’ R&D and production needs. All the types we talked about above can be found in SAM. Please visit https://www.sputtertargets.net/ for more information.

Reference:

[1] What is Physical Vapor Deposition (PVD)?

PVD Coating: Give Your Watch a Durable Coat

For most people who could not afford a pure gold watch, a gold coating may be a good choice for them. However, since it is a thin film coating, it is inevitable that the gold color would fade out. So the primary consideration in choosing the coating material/method is durability. If you want to give your watch a durable coat, you really should think about PVD coating.

What is PVD coating?

PVD coating, or Physical Vapor Deposition, refers to a variety of vacuum deposition techniques where solid metal is vaporized to produce thin films and coating. The main methods of physical vapor deposition include vacuum evaporationsputtering depositionarc plasma platingion plating, etc. PVD film has fast deposition speed as well as strong adhesion, good diffraction, and a wide application range.

Maybe you will find it not easy to understand it since PVD is a physical terminology. But actually, as a watch lover, you should just know that PVD coating can provide a metal coat to your watch, making it more beautiful and durable.

Why should you choose PVD coating?

PVD coating has high hardness, high wear resistance, low friction coefficient, good corrosion resistance, and chemical stability. So PVD coating would definitely have a longer lifetime than other traditional coatings. Apart from durability, PVD coating provides multiple kinds of metallic colors, such as gold(TiN), rose gold(TiAlN), silver(Cr2N), brass(ZrN), light grey(TiC), and so on. You will always find the one you like.

PVD Coating Colors

More tips

If you are going to give your watch a PVD coating after reading this blog, I’d like to help you save time in choosing the coating materials. Please consider Stanford Advanced Materials (SAM), which is a global supplier of various technical-grade coating materials as well as high-purity chemicals (up to 99.99999%). All of the coating materials we talked about above can be found on SAM’s website. We ensure that you can get your watch the most durable coat here.

What is Reactive Sputtering Coating Technology?

At present, reactive sputtering deposition is a well-established sputter coating technology and is widely used for industrial coating deposition to produce thin layers for high-added value products, such as flat panel displays, solar cells, optical components, and decorative finishes.

Definition

In the process of reactive sputtering, a target material is sputtered in the presence of a gas or a mixture of gasses that will react with the target material to prepare a compound film of a predetermined chemical ratio. Reactive sputtering is most often practiced using one or more magnetron sputtering cathodes. Therefore, it is also called reactive magnetron sputtering.

Sputtering Target

Sputtering targets can be divided into metal targets, alloy targets, ceramic targets, etc. Metal sputtering targets can be used to produce compound materials. For example, a titanium sputtering target can be used to produce coatings such as TiO2, TiN, and Ti-O-N. Apart from it, titanium targets can also be used to produce any of the aforementioned different compositions as well as boride and carbide films. Compared with the compound target, the metal target has the advantage of longer service life.

Reactive gases

In most cases, Argon is the main gas used in reactive sputtering as well as other sputter coating methods. It has to be mentioned that the amount of a reactive gas introduced into a process chamber should be strictly controlled in order to either achieve a certain amount of doping or to produce a fully reacted compound. Here is a list of other gasses used in reactive sputtering).

Gasses Uses
Oxygen (O2) deposition of oxide films (e.g. Al2O3, SiO2, TiO2, HfO2, ZrO2, Nb2O5, AZO, ITO)
Nitrogen (N2) deposition of nitride films (e.g. TiN, ZrN, CrN, AlN, Si3N4, AlCrN, TiAlN)
Carbon dioxide (CO2) deposition of oxide coatings
Acetylene (C2H2) deposition of metal-DLC, hydrogenated carbide, carbo-nitride films
Methane (CH4) similar applications as for C2H2

Several reactive gasses can be mixed in order to deposit a multi-component functional thin film. Additional reactive gas is sometimes used to enhance a certain deposition process (e.g. addition of N2 in the SiO2 reactive sputtering process).

Application

Coatings and films produced by Reactive Magnetron Sputtering can be used in a large variety of products such as OLED devices, optical antireflective coatings, and decorative coatings.

 Please visit https://www.sputtertargets.net/ for information.

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.

For more information, please visit https://www.sputtertargets.net/.

Magnetrons & Magnets Used in Magnetron Sputtering

The planar magnetron is an exemplary “diode” mode sputtering cathode with the key expansion of a permanent magnet cluster behind the cathode. This magnet exhibit is organized so that the attractive field on the substance of the target is ordinary to the electric field in a shut way and structures a limit “burrow” which traps electrons close to the surface of the target. This enhances the effectiveness of gas ionization and compels the release plasma, permitting higher presence at the lower gas weight and attaining a higher sputter affidavit rate for Physical Vapor Deposition (PVD) coatings.

Although some distinctive magnetron cathode/target shapes have been utilized in magnetron sputtering processes, the most widely recognized target types are circular and rectangular. Circular magnetrons are all the more regularly found in littler scale “confocal” cluster frameworks or single wafer stations in group instruments. Rectangular Magnetrons are frequently found in bigger scale “in line” frameworks where substrates examine straightly past the focus on some type of carpet lift or transporter.

Color-online-Upper-Illustrations-of-circular-and-rectangular-planar-magnetron
Color-online-Upper-Illustrations-of-circular-and-rectangular-planar-magnetron. Greene, J.. (2017). Review Article: Tracing the recorded history of thin-film sputter deposition: From the 1800s to 2017. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. 35. 05C204. 10.1116/1.4998940.

Most cathodes – including practically all circular and rectangular ones – have a straightforward concentric magnet design with the middle being one shaft and the edge the inverse. For the circular magnetron, this would be a generally little adjusted magnet in the middle, and an annular ring magnet of the inverse extremity around the outside with a hole in the middle. For the rectangular magnetron, the core one is typically a bar down the long hub (however short of the full length) with a rectangular “wall” of the inverse extremity and the distance around it with a hole in the middle. The crevice is the place the plasma will be, a roundabout ring in the circular magnetron or a lengthened “race track” in the rectangular.

The magnetron works with either an attractive arrangement – the middle could be north and the border might be south, or the other way around. Notwithstanding, in most sputter frameworks, there are various cathodes in reasonably close vicinity to one another, and you don’t need stray north/ south fields structured in the middle of the targets.

Those N/S fields ought to just be on the targets’ confronts, structuring the coveted attractive shafts there. Hence, it is completely attractive to verify all the cathodes in one framework are adjusted the same way, either all north on their borders or all south on their edges. What’s more, for offices with numerous sputter frameworks, it is similarly alluring to make all of them the same so cathodes can securely be traded between the frameworks without agonizing over magnet arrangement.

There are extra contemplations and choices in regard to the magnets. Most target materials are nonmagnetic and in this manner don’t meddle with the obliged attractive field quality. However, in the event that you are sputtering attractive materials, for example, iron or nickel, you will require either higher quality magnets, more slender targets, or both with a specific end goal to abstain from having the surface attractive field adequately shorted out by the attractive target material.

Past that, the magnet’s subtle elements, for example, attractive quality and crevice measurements, might be intended to enhance target material usage or to enhance consistency along the vital pivot of a rectangular target. It is even conceivable to utilize electromagnets rather than perpetual magnets, which can manage the cost of some level of programmable control of the attractive field, yet does, obviously, build many-sided quality and expense.

For more information, please visit https://www.sputtertargets.net/.

How to Judge the Uniformity of PVD film?

PVD, Physical Vapor Deposition, is a general term for a series of coating methods. It includes two main categories: evaporation deposition coating and sputtering deposition coating. To specifictly classify it, there are vacuum ion evaporation, magnetron sputtering, MBE molecular beam epitaxy, sol gel method, etc.

For PVD vacuum coating with different principles, the concept of uniformity will have different meanings with the coating scale and film composition, and the factors affecting uniformity are also different. In general, film uniformity can be understood from the following three aspects.

Uniformity in thickness (roughness)

From the scale of optical films (that is, 1/10 wavelength as a unit, about 100A), vacuum coating can easily control the roughness within 1/10 of the wavelength of visible light, and the uniformity is quite good.

But if it refers to the uniformity on the atomic layer scale (that is to say, to achieve 10A or even 1A surface flatness), the roughness of the film can be good or bad, which is also the main technical content and technical bottleneck in the current vacuum coating.

The thickness uniformity is mainly determined by the following points: 1) the degree of lattice matching between the substrate material and the target material; 2) the surface temperature of the substrate; 3) evaporation power, speed; 4) vacuum degree; 5) coating time, thickness.

Thin film thickness

Uniformity in chemical composition

In thin films, the atomic composition of compounds can easily produce non-uniform properties due to their small size. For example, in the process of preparing SiTiO3 thin films, if the material ratio and environment are not strictly controlled, the components of the prepared surface may not be SiTiO3, but Sr, Ti, and O may exist in other proportions.

The uniformity of the components of the evaporation coating is not easy to guarantee, and the specific factors that can be adjusted are the same as the above, but due to the limitation of the principle, for the non-single component coating, the uniformity of the components of the evaporation coating is not good.

Uniformity of lattice order

This determines whether the film is single crystal, polycrystalline, or amorphous. It is also a hot issue in vacuum coating technology.

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3 Factors of Target Quality Influence Large-area Coating

Most modern buildings have begun to use large areas of glass for lighting, and its biggest advantage is that it can bring us brighter light and a wider view. However, since the heat energy transmitted through the glass is much higher than the surrounding walls, the energy consumption of the entire building increases significantly. In order to solve this problem, people have begun to study and apply large-area Low-E glass.

Low-E glass is commonly used in building construction because of its ability to save energy, control light, and for aesthetics. The sputtering target material is one of the essential components for making low-e glass, so this article will introduce 3 factors of target quality that influence large-area coating of low-E glass.

The shape of the target materials

For large-area coating, commonly used targets include planar targets and rotatory targets according to their shapes. The shape of the target affects the stability and film properties of the magnetron sputtering coating, as well as the utilization rate of the target. Therefore, the coating quality and production efficiency can be improved by changing the shape design of the target, and the cost can be saved.

planar targets and rotatory targets
Planar targets and rotatory targets

Relative density & porosity of the target

The relative density of the target is the ratio of the actual density to the theoretical density. The theoretical density of a single-component target is the crystal density, and the theoretical density of an alloy or compound target is calculated from the theoretical density of each component and its proportion in the alloy or mixture.

If the target material is loose and porous, it will absorb more impurities and moisture, which are the main pollution sources in the coating process. These impurities will hinder the rapid acquisition of high vacuum, easily lead to electrical discharge during the sputtering process, and even burn out the target. Find high-quality target material here: https://www.sputtertargets.net/

Target grain size and crystallographic direction

For targets of the same composition, the one with the smaller grain size has a faster deposition rate. This is mainly due to the fact that grain boundaries are more vulnerable to attack during the sputtering process, and the more grain boundaries, the faster the film formation.

In addition, the grain size also affects the quality of the film formation. For example, in the production process of Low-E glass, NiCr thin-film is used as the protective layer of the infrared reflection layer Ag, and its quality has a great influence on the coating products. Since the extinction coefficient of the NiCr film is relatively large, it is generally plated very thinly (about 3nm). If the grain size is too large and the sputtering time is short, the compactness of the film will be poor, the protective effect of the Ag layer will be reduced, and the coating product will be oxidized and removed.

Conclusion

The shape of the target mainly affects the utilization rate of the target material, and a reasonable size design can improve the utilization rate of the target material and save costs. The smaller the grain size, the faster the coating rate and the better the uniformity. The higher the purity and density, the lower the porosity, the better the quality of the film formation, and the lower the probability of slag removal by discharge.

Electron Beam Deposition for Film Coating

Introduction

Electron beam deposition is a form of physical vapor deposition (PVD) in which the target anode material is bombarded with a stream of electrons generated by a tungsten filament. Electron beam thin film deposition techniques are widely used in R&D as well as in mass production applications.

Electron beam deposition is performed in a vacuum, typically starting the process at levels below 10-5 Torr. Once a suitable vacuum is reached, a tungsten filament in the electron beam source emits a stream of electrons. This electron beam can be generated in various ways, including thermionic emission, field electron emission, or ion arc source, depending on the design of the source and associated power supply.

In all cases, the negatively charged electrons are attracted to the positively charged anode material. The generated electron beam is accelerated to high kinetic energy and directed towards the material to be deposited on the substrate. This energy is converted into heat by interacting with the atoms of the evaporated material.

The purpose of generating a stream of electrons in an electron beam source is to heat the deposited material to a temperature above a vapor pressure threshold at a given background pressure. The vapor stream is then condensed onto the surface of the substrate.

Schematic representation of electron beam evaporation system depicting various parts.
Schematic representation of electron beam evaporation system depicting various parts.. Mohanty, P. & Kabiraj, Debdulal & Mandal, R.K. & Kulriya, Pawan Kumar & Sinha, Ask & Rath, Chandana. (2014). Evidence of room temperature ferromagnetism in argon/oxygen annealed TiO2 thin films deposited by electron beam evaporation technique. Journal of Magnetism and Magnetic Materials. 355. 240–245. 10.1016/j.jmmm.2013.12.025.

Deposition Rate

As with all thermal evaporation systems, the electron beam deposition rate depends on the temperature of the material being deposited and the vapor pressure (physical constant) of that material. For elemental materials, there is a fixed vapor pressure for any particular background pressure (vacuum) and material temperature. However, for alloys or composites, there may be different partial pressures associated with each component.

Compared with Sputter Coating

Unlike sputter deposition, where individual atoms arrive at the substrate surface with very high velocity and momentum, the thermally generated vapor stream arrives at the substrate surface at a considerably lower velocity, but a much greater velocity. In other words, e-beam deposition rates can be orders of magnitude greater than sputter deposition rates, making e-beam coatings very beneficial for high volume production or thick film requirements. One disadvantage, however, is that the material tends to condense directly on the substrate surface due to the different kinetic energy of the arriving species during electron beam evaporation than that of the sputtered species. In contrast, atoms of sputtered materials tend to penetrate several atomic layers (or more) to the substrate surface before losing momentum and then establishing cohesive bonds in nucleation structures and film growth. Thus sputtered films tend to provide better adhesion properties than thermally evaporated materials.

For more information, please visit https://www.sputtertargets.net/.