Patent EP0502222A1 successfully refreshed from Google Patents.
EP0502222A1
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EP
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Accelerometer and method for making it
Assignee: Honeywell Inc
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Filing: 1991-03-04
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Granted: —
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Expires: 2011-03-04
Abstract
Abstract A solid state accelerometer (10) having an all silicon sensor for measuring accelerational and gravitational forces consists of a first silicon wafer (12), a silicon frame (20) having a plurality of flexures (18), a silicon pendulum (14) attached to said flexures (18) and a second silicon wafer (16) with said wafers and frame being bonded together.
Inventors
- 👤 John F. Stokes
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 06:49
CPC Classifications
G; G01; G01P; G01P15/00; G01P15/02; G01P15/08; G01P15/0802; G01P15/125; G01P15/13; G01P15/131; G01P2015/0805; G01P2015/0822; G01P2015/0825; G01P2015/0828; Y; Y10; Y10S; Y10S148/00; Y10S148/012; Y10S438/00; Y10S438/914; Y10S438/924
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
66 words
A solid state accelerometer, characterized by : a first silicon wafer (12); a silicon frame (20,24), having a plurality of flexures (18), bonded to said first silicon wafer; a silicon pendulum (14) attached to said plurality of flexures; and a second silicon wafer (16) bonded to said silicon frame, thereby containing said pendulum within a volume enclosed by said first and second wafers and said frame.
Claim 2
Dependent Claim
67 words
Accelerometer according to claim 1, characterized in that the silicon of said first wafer (12), said frame (20), the flexures (18), said pendulum (14) and said second wafer (16), is electrically conductive; and an electrically insulating coating (22) is at the bond between said first wafer and said frame and between said second wafer and said frame, thereby conductively insulating said frame, the flexures and said pendulum.
Claim 3
Dependent Claim
146 words
Accelerometer according to claim 2, characterized in that said pendulum (14) is parallel to and normally positioned equidistant from said first and second wafers (12,16), thereby forming first and second capacitances between said pendulum and said first and second wafers, respectively; and an accelerational or gravitation force causes said pendulum to swing, in proportion to the force, about the flexures attached to one side of said frame and one side of said pendulum, and causes the distance of the pendulum to vary relative to said first and second wafers and the corresponding first and second capacitances to vary in response to the force; and the force is counteracted with an electrostatic force due to a voltage applied across said pendulum and the first and second wafers, respectively, thereby causing said pendulum to return to a normal or null position equidistant from said first and second wafers.
Claim 4
Dependent Claim
115 words
Accelerometer according to claim 3, characterized in that said first and second wafers (12,16) are composed of p+ doped conductive silicon; said frame (20) is composed of two layers of p- doped conductive silicon having an epitaxial p+ doped conductive silicon layer between the two layers of p- doped silicon of said frame; said pendulum (14) is composed of two layers of p- doped conductive silicon having an epitaxial p+ doped conductive silicon layer between the two layers of p- doped silicon of said pendulum; and said flexures (18) are composed of a layer of epitaxial p+ conductive silicon which is connected to and continuous with the epitaxial silicon layers of said frame and pendulum.
Claim 5
Dependent Claim
26 words
Accellerometer accordingh to claim 4, characterized in that the insulating coating is SiO₂ and SiN₃ and is about 2 micrometers thick; the bonding is fusion bonding.
Claim 6
Independent Claim
183 words
A method for making a solid state accelerometer, characterized by : depositing a p+ doped layer of epitaxial silicon on a double-sided polished first p- doped silicon wafer; dry etching a first pattern on the epitaxial silicon to define flexures and a proof mass; fusion bonding a second p- doped silicon wafer to the p+ doped layer of epitaxial silicon; thermally oxidizing the exposed surfaces of said first and second p- doped silicon wafers to grow dielectric interlayers to set widths of gaps for the proof mass; applying an etch resistant material of the second pattern the dielectric interlayers; anisotropically etching the first and second p- doped wafers to make individual flexures and the proof mass; removing inner portions of the dielectric inter layers to make the gaps; and fusion bonding first and second p+ doped silicon stop wafers to the dielectric inter layers of the first and second p- doped silicon wafers, thereby constituting the gaps between the proof mass and the first and second p+ doped silicon stop wafers, and sealing the proof mass from volume external to the proof mass.
Claim 7
Dependent Claim
90 words
Method according to claim 6, further characterized by connecting associated electronics to the first and second p+ wafers and to the epitaxial layer, for measuring accelerational or gravitational forces via capacitances of the gaps which are varied by the accelerational or gravitational forces affecting the proof mass, for applying voltages across the proof mass and the first and second p+ doped silicon wafers to counteract with electrostatic forces the accelerational or gravitational forces affecting the proof mass, and for providing indications of the magnitudes of the accelerational or gravitational forces.
Claim 8
Dependent Claim
15 words
Method according to claim 7, characterized in that the dielectric interlayers are Sio₂ and SiN₃.
Claim 9
Dependent Claim
14 words
Method according to claim 8, characterized in that the proof mass is a diaphragm.
Claim 10
Dependent Claim
14 words
Method according to claim 8, characterized in that the proof mass is a pendulum.
References Cited (Backward Citations)
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