Appeal No. 96-1207
Application No. 08/064,203
and the resultant defect density of the thermal oxide
layer is directly dependent on the underlying defect
density of the material on which the oxide layer is
formed. For example, pinholes are often created in a
thermal oxide layer as a result of small metallic
impurities in the underlying silicon or polysilicon
layer. The TEOS deposited layer coats all surfaces and
thus will fill in such pinholes (so long as the defects
are smaller than the thickness of the TEOS layer).
The propagation of defects in the polysilicon layer into the
thermally grown tunneling oxide layer leads to stress and
defects
in the conventional tunneling oxide layer as discussed at page
4,
lines 16 through 22 of the specification.
The issue of stress is also addressed in paragraph 10 of
the Exhibit C declaration as follows:
With regard to the issue of stress, it is well
known that stress is induced in a wafer when a thermal
oxide layer is grown. The induced stress can be large
enough to cause warping of the wafer. . . . It is well
known that [a] TEOS deposited layer can be defined to
induce either compressive or tensile stress, and be of
a much lower magnitude than for thermally grown oxide.
Consequently, stress can be minimized when using a TEOS
deposited tunneling oxide layer. This provides the
advantage of a device having a much greater useful
life.
Declarant summarizes his position in paragraph 12 of this
same declaration by stating that:
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