Physical vapor deposition

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Inside the plasma-spray physical vapor deposition (PS-PVD) chamber, ceramic powder is introduced into the plasma flame, which vaporizes it and then condenses it on the (cooler) workpiece to form the ceramic coating. Plasma Spray-Physical Vapor Deposition.jpg
Inside the plasma-spray physical vapor deposition (PS-PVD) chamber, ceramic powder is introduced into the plasma flame, which vaporizes it and then condenses it on the (cooler) workpiece to form the ceramic coating.
PVD process flow diagram PVD process.svg
PVD process flow diagram

Physical vapor deposition (PVD), sometimes called physical vapor transport (PVT), describes a variety of vacuum deposition methods which can be used to produce thin films and coatings on substrates including metals, ceramics, glass, and polymers. PVD is characterized by a process in which the material transitions from a condensed phase to a vapor phase and then back to a thin film condensed phase. The most common PVD processes are sputtering and evaporation. PVD is used in the manufacturing of items which require thin films for optical, mechanical, electrical, acoustic or chemical functions. Examples include semiconductor devices such as thin-film solar cells, [1] microelectromechanical devices such as thin film bulk acoustic resonator, aluminized PET film for food packaging and balloons, [2] and titanium nitride coated cutting tools for metalworking. Besides PVD tools for fabrication, special smaller tools used mainly for scientific purposes have been developed. [3]

Contents

The source material is unavoidably also deposited on most other surfaces interior to the vacuum chamber, including the fixturing used to hold the parts. This is called overshoot.

Examples

Metrics and testing

Various thin film characterization techniques can be used to measure the physical properties of PVD coatings, such as:

Comparison to other deposition techniques

Advantages

Disadvantages

Applications

Anisotropic glasses

This figure gives a simple illustration of the process of PVD where the desired deposited gas molecules enter the chamber after being condensed, and then are condensed once again onto a thin film, such as the anisotropic glass. Physical Vapor Deposition (PVD).jpg
This figure gives a simple illustration of the process of PVD where the desired deposited gas molecules enter the chamber after being condensed, and then are condensed once again onto a thin film, such as the anisotropic glass.

PVD can be used as an application to make anisotropic glasses of low molecular weight for organic semiconductors. [7] The parameter needed to allow the formation of this type of glass is molecular mobility and anisotropic structure at the free surface of the glass. [7] The configuration of the polymer is important where it needs to be positioned in a lower energy state before the added molecules bury the material through a deposition. This process of adding molecules to the structure starts to equilibrate and gain mass and bulk out to have more kinetic stability. [7] The packing of molecules here through PVD is face-on, meaning not at the long tail end, allows further overlap of pi orbitals as well which also increases the stability of added molecules and the bonds. The orientation of these added materials is dependent mainly on temperature for when molecules will be deposited or extracted from the molecule. [7] The equilibration of the molecules is what provides the glass with its anisotropic characteristics. The anisotropy of these glasses is valuable as it allows a higher charge carrier mobility. [7] This process of packing in glass in an anisotropic way is valuable due to its versatility and the fact that glass provides added benefits beyond crystals, such as homogeneity and flexibility of composition.

Decorative applications

By varying the composition and duration of the process, a range of colors can be produced by PVD on stainless steel. The resulting colored stainless steel product can appear as brass, bronze, and other metals or alloys. This PVD-colored stainless steel can be used as exterior cladding for buildings and structures, such as the Vessel sculpture in New York City and The Bund in Shanghai. It is also used for interior hardware, paneling, and fixtures, and is even used on some consumer electronics, like the Space Gray and Gold finishes of the iPhone and Apple Watch.[ citation needed ]

Cutting tools

PVD is used to enhance the wear resistance of steel cutting tools' surfaces and decrease the risk of adhesion and sticking between tools and a workpiece. This includes tools used in metalworking or plastic injection molding. [8] :2 The coating is typically a thin ceramic layer less than 4 μm that has very high hardness and low friction. It is necessary to have high hardness of workpieces to ensure dimensional stability of coating to avoid brittling. It is possible to combine PVD with a plasma nitriding treatment of steel to increase the load bearing capacity of the coating. [8] :2 Chromium nitride (CrN), titanium nitride (TiN), and Titanium Carbonitride (TiCN) may be used for PVD coating for plastic molding dies. [8] :5

Other applications

PVD coatings are generally used to improve hardness, increase wear resistance, and prevent oxidation. They can also be used for aesthetic purposes. Thus, such coatings are used in a wide range of applications such as:

See also

Related Research Articles

<span class="mw-page-title-main">Chemical vapor deposition</span> Method used to apply surface coatings

Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.

<span class="mw-page-title-main">MEMS</span> Very small devices that incorporate moving components

MEMS is the technology of microscopic devices incorporating both electronic and moving parts. MEMS are made up of components between 1 and 100 micrometres in size, and MEMS devices generally range in size from 20 micrometres to a millimetre, although components arranged in arrays can be more than 1000 mm2. They usually consist of a central unit that processes data and several components that interact with the surroundings.

<span class="mw-page-title-main">Getter</span> Consumable reactive substance used to fix another one such as for oxygen removal in vacuum tubes

A getter is a deposit of reactive material that is placed inside a vacuum system to complete and maintain the vacuum. When gas molecules strike the getter material, they combine with it chemically or by absorption. Thus the getter removes small amounts of gas from the evacuated space. The getter is usually a coating applied to a surface within the evacuated chamber.

<span class="mw-page-title-main">Pulsed laser deposition</span>

Pulsed laser deposition (PLD) is a physical vapor deposition (PVD) technique where a high-power pulsed laser beam is focused inside a vacuum chamber to strike a target of the material that is to be deposited. This material is vaporized from the target which deposits it as a thin film on a substrate. This process can occur in ultra high vacuum or in the presence of a background gas, such as oxygen which is commonly used when depositing oxides to fully oxygenate the deposited films.

A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films is a fundamental step in many applications. A familiar example is the household mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors, while more recently the metal layer is deposited using techniques such as sputtering. Advances in thin film deposition techniques during the 20th century have enabled a wide range of technological breakthroughs in areas such as magnetic recording media, electronic semiconductor devices, integrated passive devices, light-emitting diodes, optical coatings, hard coatings on cutting tools, and for both energy generation and storage. It is also being applied to pharmaceuticals, via thin-film drug delivery. A stack of thin films is called a multilayer.

<span class="mw-page-title-main">Titanium nitride</span> Ceramic material

Titanium nitride is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties.

<span class="mw-page-title-main">Zirconium nitride</span> Chemical compound

Zirconium nitride is an inorganic compound used in a variety of ways due to its properties.

<span class="mw-page-title-main">Ion plating</span> Method of coating solid surfaces with ions

Ion plating (IP) is a physical vapor deposition (PVD) process that is sometimes called ion assisted deposition (IAD) or ion vapor deposition (IVD) and is a modified version of vacuum deposition. Ion plating uses concurrent or periodic bombardment of the substrate, and deposits film by atomic-sized energetic particles called ions. Bombardment prior to deposition is used to sputter clean the substrate surface. During deposition the bombardment is used to modify and control the properties of the depositing film. It is important that the bombardment be continuous between the cleaning and the deposition portions of the process to maintain an atomically clean interface. If this interface is not properly cleaned, then it can result into a weaker coating or poor adhesion.

<span class="mw-page-title-main">Nitriding</span> Nitrogen diffusion case-hardening process

Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. These processes are most commonly used on low-alloy steels. They are also used on titanium, aluminium and molybdenum.

Electron-beam physical vapor deposition, or EBPVD, is a form of physical vapor deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum. The electron beam causes atoms from the target to transform into the gaseous phase. These atoms then precipitate into solid form, coating everything in the vacuum chamber with a thin layer of the anode material.

<span class="mw-page-title-main">Tantalum nitride</span> Chemical compound

Tantalum nitride (TaN) is a chemical compound, a nitride of tantalum. There are multiple phases of compounds, stoichimetrically from Ta2N to Ta3N5, including TaN.

<span class="mw-page-title-main">Vacuum deposition</span> Method of coating solid surfaces

Vacuum deposition is a group of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes operate at pressures well below atmospheric pressure. The deposited layers can range from a thickness of one atom up to millimeters, forming freestanding structures. Multiple layers of different materials can be used, for example to form optical coatings. The process can be qualified based on the vapor source; physical vapor deposition uses a liquid or solid source and chemical vapor deposition uses a chemical vapor.

Platit AG is a Swiss company that manufactures and markets coating equipment for the manufacturing cutting tool industry.

<span class="mw-page-title-main">Plasma-enhanced chemical vapor deposition</span> Method of depositing thin films onto a substrate

Plasma-enhanced chemical vapor deposition (PECVD) is a chemical vapor deposition process used to deposit thin films from a gas state (vapor) to a solid state on a substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases. The plasma is generally created by radio frequency (RF) frequency or direct current (DC) discharge between two electrodes, the space between which is filled with the reacting gases.

<span class="mw-page-title-main">Evaporation (deposition)</span> Common method of thin-film deposition

Evaporation is a common method of thin-film deposition. The source material is evaporated in a vacuum. The vacuum allows vapor particles to travel directly to the target object (substrate), where they condense back to a solid state. Evaporation is used in microfabrication, and to make macro-scale products such as metallized plastic film.

<span class="mw-page-title-main">Sputter deposition</span> Method of thin film application

Sputter deposition is a physical vapor deposition (PVD) method of thin film deposition by the phenomenon of sputtering. This involves ejecting material from a "target" that is a source onto a "substrate" such as a silicon wafer. Resputtering is re-emission of the deposited material during the deposition process by ion or atom bombardment. Sputtered atoms ejected from the target have a wide energy distribution, typically up to tens of eV. The sputtered ions can ballistically fly from the target in straight lines and impact energetically on the substrates or vacuum chamber. Alternatively, at higher gas pressures, the ions collide with the gas atoms that act as a moderator and move diffusively, reaching the substrates or vacuum chamber wall and condensing after undergoing a random walk. The entire range from high-energy ballistic impact to low-energy thermalized motion is accessible by changing the background gas pressure. The sputtering gas is often an inert gas such as argon. For efficient momentum transfer, the atomic weight of the sputtering gas should be close to the atomic weight of the target, so for sputtering light elements neon is preferable, while for heavy elements krypton or xenon are used. Reactive gases can also be used to sputter compounds. The compound can be formed on the target surface, in-flight or on the substrate depending on the process parameters. The availability of many parameters that control sputter deposition make it a complex process, but also allow experts a large degree of control over the growth and microstructure of the film.

Substrate is a term used in materials science and engineering to describe the base material on which processing is conducted. Surfaces have different uses, including producing new film or layers of material and being a base to which another substance is bonded.

High-power impulse magnetron sputtering is a method for physical vapor deposition of thin films which is based on magnetron sputter deposition. HIPIMS utilises extremely high power densities of the order of kW⋅cm−2 in short pulses (impulses) of tens of microseconds at low duty cycle of < 10%. Distinguishing features of HIPIMS are a high degree of ionisation of the sputtered metal and a high rate of molecular gas dissociation which result in high density of deposited films. The ionization and dissociation degree increase according to the peak cathode power. The limit is determined by the transition of the discharge from glow to arc phase. The peak power and the duty cycle are selected so as to maintain an average cathode power similar to conventional sputtering (1–10 W⋅cm−2).

<span class="mw-page-title-main">Precision glass moulding</span> Production of optical glass without grinding and polishing

Precision glass moulding is a replicative process that allows the production of high precision optical components from glass without grinding and polishing. The process is also known as ultra-precision glass pressing. It is used to manufacture precision glass lenses for consumer products such as digital cameras, and high-end products like medical systems. The main advantage over mechanical lens production is that complex lens geometries such as aspheres can be produced cost-efficiently.

<span class="mw-page-title-main">Titanium aluminium nitride</span> Group of metastable hard coatings

Titanium aluminium nitride (TiAlN) or aluminium titanium nitride is a group of metastable hard coatings consisting of nitrogen and the metallic elements aluminium and titanium. This compound as well as similar compounds(such as TiN and TiCN) are most notably used for coating machine tools such and endmills and drills to change their properties, such as increased thermal stability and/or wear resistance. Four important compositions are deposited in industrial scale by physical vapor deposition methods:

References

  1. Selvakumar, N.; Barshilia, Harish C. (1 March 2012). "Review of physical vapor deposited (PVD) spectrally selective coatings for mid- and high-temperature solar thermal applications" (PDF). Solar Energy Materials and Solar Cells. 98: 1–23. doi:10.1016/j.solmat.2011.10.028.
  2. Hanlon, Joseph F.; Kelsey, Robert J.; Forcinio, Hallie (23 April 1998). "Chapter 4 Coatings and Laminations". Handbook of Package Engineering 3rd Edition. CRC Press. ISBN   978-1566763066.
  3. Fortunato, E.; Barquinha, P.; Martins, R. (12 June 2012). "Oxide Semiconductor Thin-Film Transistors: A Review of Recent Advances". Advanced Materials. 24 (22): 2945–2986. doi: 10.1002/adma.201103228 . ISSN   1521-4095. PMID   22573414. S2CID   205242464.
  4. He, Zhenping; Kretzschmar, Ilona (6 December 2013). "Template-Assisted GLAD: Approach to Single and Multipatch Patchy Particles with Controlled Patch Shape". Langmuir. 29 (51): 15755–15761. doi:10.1021/la404592z. PMID   24313824.
  5. He, Zhenping; Kretzschmar, Ilona (18 June 2012). "Template-Assisted Fabrication of Patchy Particles with Uniform Patches". Langmuir. 28 (26): 9915–9919. doi:10.1021/la3017563. PMID   22708736.
  6. Dunaev A.A., Egorova I.L. (2015). "Properties and optical application of polycrystalline zinc selenide obtained by physical vapor deposition". Scientific and Technical Journal of Information Technologies, Mechanics and Optics. 15 (3): 449–456. doi: 10.17586/2226-1494-2015-15-3-449-456 .
  7. 1 2 3 4 5 Gujral, Ankit; Yu, Lian; Ediger, M.D. (1 April 2018). "Anisotropic organic glasses". Current Opinion in Solid State and Materials Science. 22 (2): 49–57. Bibcode:2018COSSM..22...49G. doi: 10.1016/j.cossms.2017.11.001 . ISSN   1359-0286. S2CID   102671908.
  8. 1 2 3 "UDDEHOLM TOOL STEEL FOR PVD COATINGS" (PDF). 2020.

Further reading