Appeal No. 95-2454
Application No. 07/396,733
Brief, p. 36. However, this problem had already been solved in the art, for example, by Frouin’s technique
which appears to solve the same problem. Frouin expressly teaches that
it is possible considerably to reduce the peripheral zone referred to as the “dead
region,” which is usually formed around each integrated circuit unit and above
which the contacts for external connections are present.
Frouin, col. 2, lines 46-50.
Claims 25 and 49
Independent claims 25 and 49 require that the epitaxial layer and the substrate be of the same
conductivity type and require the additional step of forming a region of opposite conductivity type in the
substrate prior to the growth of the epitaxial layer. The examiner relies on Makimoto in addition to Frouin,
Murphy and Doo in rejecting these claims.
Makimoto discloses forming regions in the substrate having a conductivity type which is opposite
to that of the substrate and covering the substrate and the regions with an epitaxial layer having the same
conductivity type as the substrate. Makimoto, col. 3, lines 49-55. Electrical isolation is achieved by
forming isolation channels having the same conductivity type as the regions formed in the substrate. Thus,
the insulation technique used in the Makimoto reference is the same technique disclosed in applicant’s
Figure 1. In our opinion one having ordinary skill in the art would have recognized that Frouin’s isolation
technique is an alternative to the technique taught by Makimoto. It would have been obvious, therefore,
to substitute Frouin’s isolatin technique for Makimoto’s technique. The motivations to use Frouin’s
technique comes from Frouin’s teaching of the benefits of the oxide channel technique over the utilization
of a material having the same conductivity type. Frouin, col. 2, lines 31-51. It would similarly be obvious
for the reason already stated above to use a the single mask technique taught by Murphy to etch and
oxidize the insolation channels and to substitute oxide alone for the combination of oxide and polycrystalline
silicon as suggested from Doo’s disclosure. The subject matter of claims 25 and 49 would have been prima
facie obvious.
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