Vacuum deposition

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Vacuum deposition is a family of processes used to deposit layers atom-by-atom or molecule-by-molecule at sub-atmospheric pressure (vacuum) on a solid surface. The layers may be as thin as one atom to millimeters thick (freestanding structures). There may be multiple layers of different materials (e.g. optical coatings). A thickness of less than one micrometre is generally called a thin film while a thickness greater than one micrometre is called a coating. The vacuum environment may serve one or more purposes including:

• reducing the particle density so that the mean free path 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 may come from a variety of sources including:

• thermal evaporation, Evaporation (deposition)
• sputtering
• cathodic arc vaporization
• laser ablation
• decomposition of a chemical vapor precursor, chemical vapor deposition

When the vapor source is from a liquid or solid material the process is called physical vapor deposition (PVD). When the source is from a chemical vapor precursor the process is called low pressure chemical vapor deposition (LPCVD) or, if in a plasma, plasma enhanced CVD (PECVD) or "plasma assisted CVD" (PACVD). Often a combination of PVD and CVD processes are used in the same or connected processing chambers.

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).

Applications

• Electrical conduction: metallic films, transparent conductive oxides (TCO), superconducting films & coatings
• Semiconductor devices: semiconductor films, electrically insulating films
• Solar cells.
• Optical films: antireflective coatings, optical filters
• Reflective coatings: mirrors, heat mirrors
• Tribological coating: hard coatings, erosion resistant coatings, solid film lubricants
• Energy conservation & generation: low-E glass coatings, solar absorbing coatings, mirrors, solar thin film photovoltaic cells, smart films
• Magnetic films: magnetic recording
• Diffusion barrier: gas permeation barriers, vapor permeation barriers, solid state diffusion barriers
• Corrosion protection:

See also

• Ion plating
• Sputter deposition
• Cathodic arc deposition
• Thermal evaporation
• Spin coating

References

Bibliography

• SVC, "51st Annual Technical Conference Proceedings" (2008) SVC Publications ISSN 0737-5921 (previous proceeding available on CD)
• Anders, Andre (editor) "Handbook of Plasma Immersion Ion Implantation and Deposition" (2000) Wiley-Interscience ISBN 0-4712-4698-0
• Bach, Hans and Dieter Krause (editors) "Thin Films on Glass" (2003) Springer-Verlag ISBN 3-540-58597-4
• 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 ISBN 3-00-004953-3
• Glocker,and I. Shah (editors), "Handbook of Thin Film Process Technology", Vol.1&2 (2002) Institute of Physics ISBN 0 7503 0833 8 (2 vol. set)
• Mahan, John E. "Physical Vapor Deposition of Thin Films" (2000) John Wiley & Sons ISBN 0-471-33001-9
• Mattox, Donald M. "Handbook of Physical Vapor Deposition (PVD) Processing" (1998) Noyes Publications ISBN 0-8155-1422-0
• Mattox, Donald M. "The Foundations of Vacuum Coating Technology" (2003) Noyes Publications ISBN 0-8155-1495-6
• 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 ISBN 978-1-878068-27-9
• Westwood, William D. "Sputter Deposition", AVS Education Committee Book Series, Vol. 2 (2003) AVS ISBN 0-7354-0105-5
• Willey, Ronald R. "Practical Monitoring and Control of Optical Thin Films (2007)" Willey Optical, Consultants ISBN 978-6151-3760-5
• Willey, Ronald R. "Practical Equipment, Materials, and Processes for Optical Thin Films" (2007) Willey Optical, Consultants ISBN 978-6151-4397-2