epitaxial growth is the process of depositing a thin layer (0.5 to 20
material over a single crystal substrate,
usually through chemical vapor deposition (CVD). In
semiconductors, the deposited film is often the same material as the
substrate, and the process is known as
homoepitaxy, or simply,
An example of this is silicon deposition over a silicon substrate.
epitaxy is done to improve the
growing a lightly doped epi layer over a heavily-doped silicon
substrate, a higher breakdown voltage across the collector-substrate
junction is achieved while maintaining low collector resistance.
Lower collector resistance allows a higher operating speed with
the same current.
also recently been used in CMOS VLSI circuits. By fabricating
the CMOS device on a very thin (3-7 microns) lightly doped epi
layer grown over a heavily-doped substrate,
improving the performance of devices, epitaxy also allows better
doping concentrations of the devices. The layer can also be
made oxygen- and carbon-free. The disadvantages of epitaxy include
higher cost of wafer fabrication, additional process complexities, and
problems associated with defects in the epi layer.
vapor deposition of silicon epitaxy is usually achieved using an
(Fig. 1) that consists of a quartz reaction chamber into which a
is placed. The susceptor provides two things: 1) mechanical
for the wafers and 2) an environment with uniform
distribution. Epitaxial deposition takes place at a
temperature as the required
flow into the chamber.
1. Example of an
Epitaxial Deposition Process; Silicon on
Manufacturing; Wafer Fab Equipment
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