Physical vapor deposition (
PVD) is a variety of
vacuum depositionVacuum deposition is a family of processes used to deposit layers atom-by-atom or molecule-by-molecule at sub-atmospheric pressure on a solid surface. The layers may be as thin as one atom to millimeters thick . There may be multiple layers of different materials...
and is a general term used to describe any of a variety of methods to deposit
thin filmA thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
s by the condensation of a vaporized form of the desired film material onto various workpiece surfaces (e.g., onto
semiconductorA semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
waferA wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...
s). The coating method involves purely physical processes such as high temperature vacuum
evaporationEvaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
with subsequent condensation, or plasma sputter bombardment rather than involving a chemical reaction at the surface to be coated as in
chemical vapor depositionChemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
. The term physical vapor deposition appears originally in the 1966 book
Vapor Deposition by CF Powell, JH Oxley and JM Blocher Jr, but
Michael FaradayMichael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
was using PVD to deposit coatings as far back as 1838.
Variants of PVD include, in order of increasing novelty:
- Cathodic Arc Deposition
Cathodic arc deposition or Arc-PVD is a physical vapor deposition technique in which an electric arc is used to vaporize material from a cathode target. The vaporized material then condenses on a substrate, forming a thin film...
: In which a high power electric arc discharged at the target (source) material blasts away some into highly ionized vapor to be deposited onto the workpiece.
- Electron beam physical vapor deposition
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...
: In which the material to be deposited is heated to a high vapor pressure by electron bombardment in "high" vacuum and is transported by diffusion to be deposited by condensation on the (cooler) workpiece.
- Evaporative 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 , where they condense back to a solid state...
: In which the material to be deposited is heated to a high vapor pressure by electrically resistive heating in "low" vacuum.
- Pulsed laser deposition
Pulsed laser deposition is a thin film deposition 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...
: In which a high power laser ablates material from the target into a vapor.
- Sputter deposition
Sputter deposition is a physical vapor deposition method of depositing thin films by sputtering, that is ejecting, material from a "target," that is source, which then deposits onto a "substrate," such as a silicon wafer...
: In which a glow plasma discharge (usually localized around the "target" by a magnet) bombards the material sputtering some away as a vapor for subsequent deposition. Here is an animation of a generic PVD sputter tool: PVD Animation
PVD is used in the manufacture of items including semiconductor devices,
aluminizedAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
PET filmBoPET is a polyester film made from stretched polyethylene terephthalate and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.A variety of companies manufacture boPET and other...
for balloons and snack bags, and coated cutting tools for metalworking. Besides PVD tools for fabrication special smaller tools mainly for scientific purposes have been developed. They mainly serve the purpose of extreme thin films like atomic layers and are used mostly for small substrates. A good example are mini e-beam evaporators which can deposit monolayers of virtually all materials with melting points up to 3500°C.
The source material is unavoidably also deposited on most other surfaces interior to the vacuum chamber, including the workholders.
Some of the techniques used to measure the physical properties of PVD coatings are:
- Calo tester
Coatings with thicknesses typically between 0.1 to 50 micrometres such as PVD coatings or CVD coatings are used in many industries to improve the surface properties of tools and components. The Calo tester is a quick, simple and inexpensive piece of equipment used to measure the thickness of these...
: coating thickness test
- Nanoindentation
Nanoindentation is a variety of indentation hardness tests applied to small volumes. Indentation is perhaps the most commonly applied means of testing the mechanical properties of materials...
: hardness test for thin-film coatings
- Pin on disc tester: wear and friction coefficient test
- Scratch tester: coating adhesion test
See thin-film deposition for a more general discussion of this class of manufacturing technique.
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