Physical Vapor Deposition: Sputter Coating & Evaporation

Physical vapor deposition processes use vacuum technology to create a sub-atmospheric pressure environment and an atomic or molecular condensable vapor source (from a solid or liquid surface) to deposit thin films and coatings. Sputtering deposition and vacuum evaporation are among the more well known.

physical vapor deposition sputtering evaporation

Sputtering deposition

The sputtering deposition is an etching process that alters the physical properties of a surface. In this process, a gas plasma discharge is set up between two electrodes: a cathode plating material (the sputter coater targets) and an anode material (the substrate). The film made by sputter coating are thin, ranging from 0.00005 – 0.01 mm. Chromium, titanium, aluminum, copper, molybdenum, tungsten, gold, and silver are typical sputter coating targets.

Sputter coated films are used routinely in decorative applications such as watchbands, eyeglasses, and jewelry. Also, the electronics industry relies on heavily sputtered coatings and films, such as thin film wiring on chips and recording heads as well as magnetic and magneto-optic recording media. Companies also use sputter deposition to produce reflective films for large pieces of architectural glass used in the automotive industry. Compared to other deposition processes, sputter deposition is relatively inexpensive.

vacuum coating

Vacuum Evaporation

The vacuum evaporation is a process of reducing the wastewater volume through a method that consists of concentrating a solution by eliminating the solvent by boiling. In this case, it is performed at a pressure lower than atmospheric pressure. Thus, the boiling temperature is much lower than that at atmospheric pressure, thereby resulting in notable energy savings. The basic components of this process consist of: evaporation pellets,  heat-exchanger, vacuum, vapor separator, and condenser.

Vacuum evaporation is used in the semiconductor, microelectronics, and optical industries and in this context is a process of depositing thin films of material onto surfaces. High-purity films can be obtained from a source evaporation material with high purity. The source of the material that is going to be vaporized onto the substrate can be a solid in any shape or form (usually pellets). The versatility of this method trumps other deposition processes. Also, when the deposition is not desired, masks are utilized to define the areas on the substrate for control purposes.

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Evaporation Pellets for Thin Film Coating

Gold (Au) Evaporation Materials

Evaporation pellets are evaporation materials for vacuum evaporation coating.

Evaporation is a form of physical vapor deposition (PVD) where the evaporation material is heated to a high vapor pressure, often in a molten state. The vapors are then condensed on the substrate to form a thin film.

The most common heating method for vacuum evaporation is the resistance heating method. The advantages of resistance heating method include simple structure, low cost and convenient operation. The disadvantage is that it is not suitable for refractory metals and high temperature resistant dielectric materials. Electron beam heating and laser heating can overcome the shortcomings of resistance heating. Electron beam heating uses a focused electron beam to directly heat the bombarded material, and the kinetic energy of the electron beam becomes thermal energy, causing the material to evaporate. Laser heating uses a high-power laser as a heating source, but due to the high cost of high-power lasers, it can only be used in a few research laboratories. You can refer to Five evaporation sources for heating for detailed information of the heating methods. As for a thin film precious metal coating, the heating is typically accomplished via resistive heating or by E-beam (electron beam).

Evaporation pellets or slugs are manufactured with specific form factors intended to vaporize at known rates. Often during evaporation processes, “spitting” results in liquid droplet material splattering on to the substrate. Engineered pellets are made with specified metal purities and processes intended to minimize incorporated gases and impurities to mitigate “spitting” in process.

Silver (Ag) Evaporation Materials

Optimal evaporative performance for thin film deposition is highly dependent on the use of high purity materials specifically customized for PVD processes. It requires evaporation materials that feature low organic and inorganic impurities, as well as minimal surface contamination. This level of purity results in highly reproducible performance with low spit rates and defects. SAM offers high-quality evaporation materials in precious metals for your PVD coating.

The following chart shows some common thin film deposition of precious metals. SAM can customize any precious metal alloy you need that is not listed.

 Gold Copper Gold Nickel Gold Nickel Indium
Gold Palladium Gold Gold Silicon
Gold Silver Platinum Gold Tin Gold Zinc
Palladium Rhenium Palladium Lithium Palladium Manganese
Palladium Nickel Platinum Palladium Platinum Iridium
Platinum rhodium Silver Gold Silver Titanium

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