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 Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

(i.e.,

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...

). 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 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 polym ...

uses a liquid or solid source and chemical vapor deposition uses a chemical vapor.

Description

The vacuum environment may serve one or more purposes: * reducing the particle density so that the

mean free path In physics, mean free path is the average distance over which a moving particle (such as an atom, a molecule, or a photon) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as a ...

for collision is long * reducing the particle density of undesirable atoms and molecules (contaminants) * providing a low pressure plasma environment * providing a means for controlling gas and vapor composition * providing a means for mass flow control into the processing chamber. Condensing particles can be generated in various ways: * thermal evaporation *

sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and ca ...

* cathodic arc vaporization * laser ablation * decomposition of a chemical vapor precursor, chemical vapor deposition In reactive deposition, the depositing material reacts either with a component of the gaseous environment (Ti + N → TiN) or with a co-depositing species (Ti + C → TiC). A plasma environment aids in activating gaseous species (N₂ → 2N) and in decomposition of chemical vapor precursors (SiH₄ → Si + 4H). The plasma may also be used to provide ions for vaporization by sputtering or for bombardment of the substrate for sputter cleaning and for bombardment of the depositing material to densify the structure and tailor properties ( ion plating).

Types

When the vapor source is a liquid or solid the process is called

(PVD). When the source is a chemical vapor precursor, the process is called chemical vapor deposition (CVD). The latter has several variants: ''low-pressure chemical vapor deposition'' (LPCVD),

plasma-enhanced chemical vapor deposition 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 creati ...

(PECVD), and ''plasma-assisted CVD'' (PACVD). Often a combination of PVD and CVD processes are used in the same or connected processing chambers.

Applications

Electrical conduction Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...

: metallic films, resistors, transparent conductive oxides (TCOs), superconducting films & coatings *

Semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

devices: semiconductor films, electrically insulating films *

Solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

s * Optical films: anti-reflective coatings, optical filters * Reflective coatings:

mirror A mirror or looking glass is an object that reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the im ...

hot mirror A hot mirror is a specialized dielectric mirror, a dichroic filter, often employed to protect optical systems by reflecting infrared light back into a light source, while allowing visible light to pass. Hot mirrors can be designed to be inserted ...

s *

Tribological Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. Tribology is highly interdisciplinary, drawing on many academic field ...

coating: hard coatings, erosion resistant coatings, solid film lubricants * Energy conservation & generation:

low emissivity Low emissivity (low ''e'' or low thermal emissivity) refers to a surface condition that emits low levels of radiant thermal (heat) energy. All materials absorb, reflect, and emit radiant energy according to Planck's law but here, the primary con ...

glass coatings, solar absorbing coatings, mirrors, solar

thin film 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 (a process referred to as deposition) is a fundamental step in many ...

photovoltaic cells A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

, ''smart'' films *

Magnetic film Magnetic field viewing film is used to show stationary or (less often) slowly changing magnetic fields; it shows their location and direction. It is a translucent thin flexible sheet, coated with micro-capsules containing nickel flakes suspended ...

magnetic recording Magnetic storage or magnetic recording is the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetisation in a magnetizable material to store data and is a form of non-volatile memory. The information is ac ...

* Diffusion barrier: gas permeation barriers, vapor permeation barriers, solid state diffusion barriers *

Corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

protection: * Automotive applications: lamp reflectors and trim applications * Vinyl record pressing, manufacture of gold and

platinum records Music recording certification is a system of certifying that a music recording has shipped, sold, or streamed a certain number of units. The threshold quantity varies by type (such as album, single, music video) and by nation or territory (see ...

A thickness of less than one

micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

is generally called a

, while a thickness greater than one micrometre is called a coating.

References

Bibliography

* SVC, "51st Annual Technical Conference Proceedings" (2008) SVC Publications (previous proceeding available on CD) * Anders, Andre (editor) "Handbook of Plasma Immersion Ion Implantation and Deposition" (2000) Wiley-Interscience * Bach, Hans and Dieter Krause (editors) "Thin Films on Glass" (2003) Springer-Verlag * Bunshah, Roitan F (editor). "Handbook of Deposition Technologies for Films and Coatings", second edition (1994) * Glaser, Hans Joachim "Large Area Glass Coating" (2000) Von Ardenne Anlagentechnik GmbH * Glocker and I. Shah (editors), "Handbook of Thin Film Process Technology", Vol.1&2 (2002) Institute of Physics (2 vol. set) * Mahan, John E. "Physical Vapor Deposition of Thin Films" (2000) John Wiley & Sons * Mattox, Donald M. "Handbook of Physical Vapor Deposition (PVD) Processing" 2nd edition (2010) Elsevier * Mattox, Donald M. "The Foundations of Vacuum Coating Technology" (2003) Noyes Publications * Mattox, Donald M. and Vivivenne Harwood Mattox (editors) "50 Years of Vacuum Coating Technology and the Growth of the Society of Vacuum Coaters" (2007), Society of Vacuum Coaters * Westwood, William D. "Sputter Deposition", AVS Education Committee Book Series, Vol. 2 (2003) AVS * Willey, Ronald R. "Practical Monitoring and Control of Optical Thin Films (2007)" Willey Optical, Consultants * Willey, Ronald R. "Practical Equipment, Materials, and Processes for Optical Thin Films" (2007) Willey Optical, Consultants {{ref end Thin film deposition Vacuum Industrial processes

Description

Types

Applications

See also

References

Bibliography