US5126812A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Monolithic micromechanical accelerometer
Assignee: Charles Stark Draper Laboratory Inc
•
Filing: 1990-05-23
•
Granted: 1992-06-30
•
Expires: 2010-05-23
Abstract
Abstract A micromechanical accelerometer is disclosed comprising a mass of monocrystalline silicon in which a substantially symmetrical plate attached to a silicon frame by flexible linkages is produced by selective etching. The plate has a plurality of apertures patterned and etched therethrough to speed further etching and freeing of the plate and flexible linkages, suspending them above a void etched beneath. The plate has a weight disposed thereon near an end remote from the flexible linkages. The plate is capable of limited motion about an axis created by the flexible linkages. Stop means limit motion of the plate about the axis. Strain relief tension beams are provided to relieve stress induced by boron diffusion necessary to provide etch stopping and the tension beams are trimmable in a manner which permits tuning of the resonant frequency of the plate. Grooves or depressions are provided in the flexible linkages to resist bending or buckling without increasing torsional stiffness. The plate and flexible linkages are electrically isolated from the silicon mass and frame by dielectric or P-N junction isolation. Integral P-N junction electrodes and surface bridging electrodes may be used to provide top to bottom symmetry in torquing and sensing of the plate while maintaining isolation and monlithic construction. Bias and readout circuitry used to sense and torque the plate may be provided integrally with the plate and formed during plate processing.
Inventors
- 👤 Paul Greiff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 06:42
CPC Classifications
G; G01; G01C; G01C19/00; G01C19/56; G01C19/5719; G01P; G01P15/00; G01P15/02; G01P15/08; G01P15/0802; G01P15/0888
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
135 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 2
Dependent Claim
135 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 3
Dependent Claim
167 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; at least one groove disposed in each of said plurality of flexible linkages said at least one groove substantially precluding bending and buckling of respective ones of said plurality of flexible linkages; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 4
Dependent Claim
167 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; at least one groove disposed in each of said plurality of flexible linkages said at least one groove substantially precluding bending and buckling of respective ones of said plurality of flexible linkages; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 5
Dependent Claim
161 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; relief means, disposed on said plate proximate to said plurality of flexible linkages for relieving stresses on said plate created by doping of said transducer element; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 6
Dependent Claim
161 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; relief means, disposed on said plate proximate to said plurality of flexible linkages for relieving stresses on said plate created by doping of said transducer element; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 7
Dependent Claim
193 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; at least one groove disposed in each of said plurality of flexible linkages said at least one groove substantially precluding bending and buckling of respective ones of said plurality of flexible linkages; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; relief means, disposed on said plate proximate to said plurality of flexible linkages for relieving stresses on said plate created by doping of said transducer element; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 8
Dependent Claim
193 words
A monolithic micromechanical accelerometer that includes a semiconductor transducer element, comprising: a mass of semiconductor material having a void on a top surface extending downwards, said mass of semiconductor material comprising a silicon frame; a plurality of flexible linkages integral with said frame for coupling said transducer element to said frame at opposite sides, said plurality of flexible linkages having first and second ends, said first ends being connected to said silicon frame; at least one groove disposed in each of said plurality of flexible linkages said at least one groove substantially precluding bending and buckling of respective ones of said plurality of flexible linkages; a plurality of electrodes disposed proximate to said void; a plate connected integrally to and substantially symmetrical with respect to said second ends of said plurality of flexible linkages, said plate having a plurality of apertures therethrough and having a portion facing said plurality of electrodes; relief means, disposed on said plate proximate to said plurality of flexible linkages for relieving stresses on said plate created by doping of said transducer element; and a weight disposed asymmetrically on said plate and proximate to an end of said plate.
Claim 9
Dependent Claim
34 words
The micromechanical accelerometer of claim 1, 2, 3 or 4 wherein at least one of said plurality of electrodes is integral to said mass of silicon and facing a bottom side of said plate.
Claim 10
Dependent Claim
31 words
The micromechanical accelerometer of claim 5 wherein said at least one of said plurality of electrodes is formed integrally as a highly doped P-type region patterned on an N-type silicon sub-surface.
Claim 11
Dependent Claim
28 words
The micromechanical accelerometer of claim 1, 2, 3 or 4 wherein at least one of said plurality of electrodes is a surface bridging electrode traversing said transducer element.
Claim 12
Dependent Claim
22 words
The micromechanical accelerometer of claim 7 wherein said surface bridging electrodes are supported above said frame on a region of doped material.
Claim 13
Dependent Claim
84 words
The micromechanical accelerometer of claim 8 wherein said doped region of material further comprises an isolating wall and an isolating floor doped with one of a P-type and an N-type dopant and an isolating intermediate area doped with the other of said P-type and N-type dopant and wherein each of said plurality of bridging electrodes is electrically isolated by biasing said doped region relative to said mass to effect a driven shield comprising said isolating wall, said isolating floor and said isolating intermediate area.
Claim 14
Dependent Claim
24 words
The micromechanical accelerometer of claim 1, 2, 3 or 4 further comprising isolation means for electrically isolating said transducer element from said silicon frame.
Claim 15
Dependent Claim
16 words
The micromechanical accelerometer of claim 10 wherein said isolation means is provided by a dielectric layer.
Claim 16
Dependent Claim
17 words
The micromechanical accelerometer of claim 11 wherein said isolation means is provided by a layer of oxide.
Claim 17
Dependent Claim
18 words
The micromechanical accelerometer of claim 11 wherein said isolation means is provided by a layer of silicon nitride.
Claim 18
Dependent Claim
20 words
The micromechanical accelerometer of claim 10 wherein said isolation means is provided by a combination of oxide and silicon nitride.
Claim 19
Dependent Claim
36 words
The micromechanical accelerometer of claim 10 wherein said isolation means is provided by doping said flexible linkages P-type and maintaining said silicon frame N-type effecting a P-N junction where said flexible linkages and said frame meet.
Claim 20
Dependent Claim
37 words
The micromechanical accelerometer of claim 1, 2, 3 or 4 further comprising stop means for limiting the extend of rotation of said plate about an axis formed by said first and second ends of said flexible linkages.
Claim 21
Dependent Claim
46 words
The micromechanical accelerometer of claim 16 wherein said stop means has a stem extending through an aperture in said plate and a cap disposed above said plate whereby said plate is free to move about said stem and is limited it its movement by said cap.
Claim 22
Dependent Claim
23 words
The micromechanical accelerometer of claim 16 wherein said stop means is a cantilever beam extending outward from said frame above said transducer element.
Claim 23
Dependent Claim
24 words
The micromechanical accelerometer of claim 16 wherein said stop means is a protuberant member extending beneath said plate in proximity to an end thereof.
Claim 24
Dependent Claim
19 words
The micromechanical accelerometer of claim 16 wherein a surface opposite said stop means comprises a material resistant to sticking.
Claim 25
Dependent Claim
33 words
The micromechanical accelerometer of claim 2 or 4 wherein said at least one groove has a substantially V-shaped cross-section which is formed in each of said plurality of flexible linkages by anisotropic etching.
Claim 26
Dependent Claim
33 words
The micromechanical accelerometer of claim 2 or 4 wherein said at least one groove has a substantially U-shaped cross-section which is formed in each of said plurality of flexible linkages by plasma etching.
Claim 27
Dependent Claim
36 words
The micromechanical accelerometer of claim 3 or 4 wherein said relief means comprises a beam formed by a slot disposed in said plate in proximity to second ends of each of said plurality of flexible linkages.
Claim 28
Dependent Claim
22 words
The micromechanical accelerometer of claim 23 wherein said beam is trimmable in a manner which affects the dynamic response of said plate.
References Cited (Backward Citations)
US3053095A
Cited
US3251231A
Cited
US3370458A
Cited
US3913035A
Cited
US4044305A
Cited
US4468584A
Cited
US4234666A
Cited
US4342227A
Cited
US4499778A
Cited
US4381672A
Cited
US4502042A
Cited
US4406992A
Cited
US4483194A
Cited
US4495499A
Cited
US4654663A
Cited
US4411741A
Cited
US4665605A
Cited
US4592242A
Cited
US4478076A
Cited
US4651564A
Cited
US4478077A
Cited
US4621925A
Cited
US4596158A
Cited
JPS59158566A
Cited
US4522072A
Cited
US4490772A
Cited
US4619001A
Cited
US4585083A
Cited
US4628283A
Cited
US4783237A
Cited
US4600934A
Cited
US4653326A
Cited
US4538461A
Cited
US4899587A
Cited
US4524619A
Cited
US4598585A
Cited
US4699006A
Cited
US4671112A
Cited
US4629957A
Cited
US4674180A
Cited
US4680606A
Cited
US4706374A
Cited
JPS61144576A
Cited
US4674319A
Cited
US4705659A
Cited
US4764244A
Cited
US4639690A
Cited
US4679434A
Cited
US4744249A
Cited
US4744248A
Cited
JPS6271256A
Cited
US4644753A
Cited
US4750364A
Cited
US4792676A
Cited
GB2183040A
Cited
US4736629A
Cited
US4747312A
Cited
US4712439A
Cited
JPS62221164A
Cited
US4670092A
Cited
US4869107A
Cited
US4776924A
Cited
JPS63169078A
Cited
US4743789A
Cited
US4884446A
Cited
US4805456A
Cited
US4851080A
Cited
US4789803A
Cited
US4916520A
Cited
US4808948A
Cited
US5016072A
Cited
US4890812A
Cited
US4882933A
Cited
US4855544A
Cited
US4893509A
Cited
US4901586A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-06-30 | 1995-12-30 | 1996-06-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-06-30 | 1999-12-30 | 2000-06-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-06-30 | 2003-12-30 | 2004-06-30 | $7700.00 | Window Closed / Lapsed |