Process for fabricating integrated circuits uniformly deposits silicon epitaxially on prediffused substrates without affecting the sublayer diffusion pattern. Two silicon deposits from different sources, and deposited at different temperatures, protect the sublayer pattern from the silicon tetrachloride reaction

Clarke, M. G.

Halsor, J. L.

Word, J. C.

English

NASA Technical Reports Server

October 1968	 Brief 68-10390 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Improved Process for Epitaxial Deposition

of Silicon on Prediffused Substrates 
It is frequently desirable to fabricate integrated 
circuits in a silicon layer epitaxially deposited on a 
silicon wafer in which a heavily doped sublayer pat-
tern has been diffused. Either of two methods has 
been used for the epitaxial deposition of silicon. In 
one method the silicon source is silane (SiH 4 ); in the 
other method, silicon tetrachloride (SiC1 4 ) is the sili-
con source. The silane reaction, nonreversible decom-
position at 10000 C, produces a silicon layer with 
a sharp junction. This junction is desirable, as out 
diffusion is minimized and the original sublayer pat-
tern is undisturbed. However, depletion of the re-
action gases results in a silicon layer of varying thick-
ness and resistivity. The silicon chloride reaction, re-
duction with hydrogen at 1150° C, produces a silicon 
layer that is uniform in both thickness and resistivity. 
This reaction is reversible, however, releasing and re-
depositing a sufficient amount of the diffused sublayer 
doping to obliterate the pattern. 
A new process which has been developed will uni-
formly deposit silicon expitaxially on prediffused sub-
strates without affecting the sublayer pattern. In this 
process, approximately 2 microns of silicon are first
deposited at 1000° C from a silane source. The tem-
perature of the substrate is then raised to 1150° C 
and the rest of the required silicon layer is deposited 
from a silicon tetrachloride source. In this manner, 
the sublayer diffusion pattern is protected from the 
silicon tetrachloride reaction. 
Note: 
Details may be obtained from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B68-10396 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: J. L. Halsor, 
M. G. Clarke, and J. C. Word

of Westinghouse Electric Corporation

under contract to

Marshall Space Flight Center

(MFS-14910) 
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Improved process for epitaxial deposition of silicon on prediffused substrates

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