- The name says it all: Chemical
Vapor Deposition.
CVD depends on the availability of a volatile chemical which can be
converted by some reaction into the desired solid film. We've already
discussed how the vapors, once produced, can be transported
to the substrate and heated up when they get there. Next we need to
think about what makes the vapors in the first place (that is,
volatility) and how these vapors can react in the gas phase or on the
surfaces to be converted into the film.
- We'd like to emphasize that in every CVD process,
there is of necessity some reaction path that converts the vapors to a
solid. Part of the task of designing the reactor and process is always
to force this reaction to happen only where and when it is desired
(typically on the substrate), and not everywhere else. Undesired
reactions result in particles which can fall onto the substrates,
coating of chamber walls, and clogging of exhaust openings. The
approaches to achieving this selectivity typically rely on four
levers: temperature, time, pressure, and surface specificity.
- In a brief tutorial we can't possibly hope to cover
the vast field of how atoms interact with each other. The tutorial
material is highly selective; we hope to at least provide enough
familiarity with the most relevant terminology and concepts to help
the reader negotiate the technical literature with confidence, and
perhaps remind them of material they studied in school but haven't
used since.
- We'll start by recalling some of the basic concepts
of how electrons and nuclei interact to produce atoms and bonds
between them...
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