Appeal No. 2006-1176
Application No. 09/926,202
all the elements of the claimed invention, except for the claimed
epitaxial layer deposition temperature and oxygen concentration
in units of atoms/cm3. Indeed, Wijaranakula teaches at column 3,
lines 4-21, that:
In accordance with the invention, a semiconductor
silicon crystal ingot containing sufficient dissolved
oxygen, typically between 10 ppma and 50 ppma, is grown,
preferably by using a Czochralski process. The ingot is
then sliced into wafers, which are processed using known
methods to produce a semiconductor silicon substrate having
a polished surface. An epitaxial layer of a predetermined
thickness is deposited onto the semiconductor silicon
substrate to produce an epitaxial silicon wafer. The
epitaxial silicon wafer then undergoes a first, or
nucleation, annealing step, in which it is maintained for a
first period of time within a first temperature range to
form oxide microdefects in the silicon wafer substrate. The
epitaxial layer, however, contains no nucleation sites or
nuclei to form microdefects.
The epitaxial silicon wafer then undergoes a second, or
growth, annealing step, in which it is maintained at a
second temperature for a second, typically extended period
of time to grow or enlarge the microdefects.
Wijaranakula teaches that the deposition of an epitaxial layer is
preferably carried out by chemical vapor deposition, see column
5, lines 6-9, and the first annealing step is preferably carried
out at a temperature between 650o C and 750o C, see column 5,
lines 33-48. According to Wijranakula (column 5, lines 41-44):
The optimum temperature and duration within the above-
described ranges are interrelated, depend upon the
dissolved oxygen content of substrate 12, and can be
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