Micro-mechanical semiconductor accelerometer
First Claim
1. A semiconductor accelerometer of the differential capacitor type comprising, in combination:
- a) top and bottom cover wafer elements, each cover wafer element comprising an associated oxide layer having opposed interior and exterior semiconductor layers integral therewith;
b) a first dielectric layer of predetermined thickness adjacent each said interior semiconductor layer;
c) an aperture within each of said interior semiconductor and first dielectric layers defining an electrode and a peripheral guard ring;
d) a semiconductor proofmass wafer element having opposed sides, said proofmass wafer element having an aperture therethrough defining a central proofmass, a peripheral frame and at least one flexible hinge adjoining said proofmass to said frame, said central proofmass and said peripheral frame being of like thickness; and
e) a second dielectric layer of predetermined thickness overlying said frame on each of said sides of said proofmass wafer element whereby the thicknesses of each of said second dielectric layers define gaps between facing surfaces of said central proofmass and said interior semiconductor layers.
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Accused Products
Abstract
A precision, micro-mechanical semiconductor accelerometer of the differential-capacitor type comprises a pair of etched opposing cover layers fusion bonded to opposite sides of an etched proofmass layer to form a hermetically sealed assembly. The cover layers are formed from commercially available, Silicon-On-Insulator ("SOI") wafers to significantly reduce cost and complexity of fabrication and assembly. The functional semiconductor parts of the accelerometer are dry-etched using the BOSCH method of reactive ion etching ("RIE"), thereby significantly reducing contamination inherent in prior art wet-etching processes, and resulting in features advantageously bounded by substantially vertical sidewalls.
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Citations
24 Claims
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1. A semiconductor accelerometer of the differential capacitor type comprising, in combination:
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a) top and bottom cover wafer elements, each cover wafer element comprising an associated oxide layer having opposed interior and exterior semiconductor layers integral therewith; b) a first dielectric layer of predetermined thickness adjacent each said interior semiconductor layer; c) an aperture within each of said interior semiconductor and first dielectric layers defining an electrode and a peripheral guard ring; d) a semiconductor proofmass wafer element having opposed sides, said proofmass wafer element having an aperture therethrough defining a central proofmass, a peripheral frame and at least one flexible hinge adjoining said proofmass to said frame, said central proofmass and said peripheral frame being of like thickness; and e) a second dielectric layer of predetermined thickness overlying said frame on each of said sides of said proofmass wafer element whereby the thicknesses of each of said second dielectric layers define gaps between facing surfaces of said central proofmass and said interior semiconductor layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A semiconductor accelerometer of the differential capacitor type comprising, in combination:
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a) top and bottom cover wafer elements, each cover wafer element comprising an associated oxide layer having opposed interior and exterior semiconductor layers; b) a first dielectric layer of predetermined thickness adjacent each said interior semiconductor layers; c) an aperture having vertical sidewalls within each of said interior and first dielectric layers defining an electrode and a peripheral guard ring; and d) a semiconductor proofmass wafer element having opposed sides, said proofmass wafer element having an aperture therethrough defining a central proofmass having vertical sidewalls, a peripheral frame and at least one flexible hinge adjoining said proofmass to said frame, said central proofmass and said peripheral frame being of like thickness; and e) a second dielectric layer of predetermined thickness overlying said frame on each of said sides of said proofmass wafer element whereby the thicknesses of each of said second dielectric layers define gaps between facing surfaces of said central proofmass and said interior dielectric layers. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification