Appeal No. 95-3557
Application No. 07/833,417
Appellants’ claimed invention is directed to a method of micromachining silicon to form a buried
boss diaphragm structure having relatively thick boss sections and relatively thin flexure sections and the
product made thereby. The method comprises (1) providing a substrate of a first type (p-type) doped
silicon, which can be attacked by a selected etchant material, (2) deeply diffusing a second type (n-
type) dopant only into selected areas on a surface of the first type doped silicon where the boss
sections are to be formed (thus defining areas of the first type doped silicon which cannot be attacked
by the selected etchant material) and only to a depth (x-y) less than the desired thickness (x) of the
boss diaphragm structure, (3) growing an epitaxial layer of second type (n-type) doped silicon (which
also cannot be attacked by the selected etchant material) to a desired flexure section thickness (y) over
the same surface of the substrate that has been diffusion doped, and then (4) etching away the first-type
(p-type) doped silicon so to leave the relatively thick boss sections joined by the relatively thin flexure
sections, thus forming a boss diaphragm structure of desired thickness (x).
The examiner relies upon the following references as evidence of obviousness:
Wise et al. (Wise) 5,059,543 Oct. 22, 1991
Mauger 5,110,373 May 05, 1992
Huster et al. (Huster), Sensors and Actuators, “Vertically Structured Silicon Membranes by
Electrochemical Etching,” A21-A23, 1990, pages 899-903.
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