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US5725729A
Expired / Lapsed
US
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Process for micromechanical fabrication
Assignee: Charles Stark Draper Laboratory Inc
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Filing: 1996-08-15
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Granted: 1998-03-10
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Expires: 2016-08-15
Abstract
Abstract An improved process for fabricating micromechanical devices having movable members, such as gyros and accelerometers. A starting wafer includes an oxidized silicon wafer which has been wafer bonded to a second silicon wafer which has a thin N layer on a P substrate. The wafer is patterned, doped and etched in a series of process steps which include the deposition of epitaxial layers to configure critical device dimensions and geometry. Metallizations are deposited for electrical/electronic interconnections. The process includes an ability to integrate on-chip electronics on the silicon substrate. Alignment difficulties and thermal mismatch associated with prior art processes are minimized.
Inventors
- 👤 Paul Greiff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:57
CPC Classifications
B; B81; B81C; B81C1/00; B81C1/00015; B81C1/00134; B81C1/0019; G; G01; G01P; G01P15/00; G01P15/02; G01P15/08; G01P15/0802; B81B; B81B2207/00; B81B2207/01; B81B2207/015; B81C2201/00; B81C2201/01; B81C2201/0174; B81C2201/019; G01P2015/0805; G01P2015/0822; G01P2015/0825; G01P2015/0828; G01P2015/0831
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
180 words
A process for fabricating a micromachined structure, said process comprising the steps of: selecting a starting wafer having a first single crystal silicon substrate with at least one dielectric surface and a second single crystal silicon substrate bonded to said at least one dielectric surface of said first silicon substrate; masking, patterning and diffusing said second single crystal silicon substrate with a first impurity in selected regions forming at least one of an electrode region and an anchor region; depositing a first sacrificial layer of single crystal silicon over said at least one of said electrode region and said anchor region, forming a gap spacer; depositing a first device layer of single crystal silicon over said gap spacer, said first device layer being doped in selected areas with an impurity to impart etch resistance to form a first device layer that has etch resistant areas; masking and patterning said first device layer forming a suitable geometry for said micromachined structure; and etching away said first sacrificial layer of single crystal silicon leaving said micromachined structure while preserving said dielectric surface.
Claim 2
Dependent Claim
180 words
A process for fabricating a micromachined structure, said process comprising the steps of: selecting a starting wafer having a first single crystal silicon substrate with at least one dielectric surface and a second single crystal silicon substrate bonded to said at least one dielectric surface of said first silicon substrate; masking, patterning and diffusing said second single crystal silicon substrate with a first impurity in selected regions forming at least one of an electrode region and an anchor region; depositing a first sacrificial layer of single crystal silicon over said at least one of said electrode region and said anchor region, forming a gap spacer; depositing a first device layer of single crystal silicon over said gap spacer, said first device layer being doped in selected areas with an impurity to impart etch resistance to form a first device layer that has etch resistant areas; masking and patterning said first device layer forming a suitable geometry for said micromachined structure; and etching away said first sacrificial layer of single crystal silicon leaving said micromachined structure while preserving said dielectric surface.
Claim 3
Dependent Claim
24 words
The process of claim 1 further including the step of adding metallizations for bonding pads and interconnects for electrical interconnection with said electrode region.
Claim 4
Dependent Claim
17 words
The process of claim 1 wherein said at least one dielectric surface is a silicon nitride surface.
Claim 5
Dependent Claim
16 words
The process of claim 1 wherein said at least one dielectric surface is an oxide surface.
Claim 6
Dependent Claim
11 words
The process of claim 1 wherein said first impurity is boron.
Claim 7
Dependent Claim
25 words
The process of claim 1 further including a step of removing selected portions of said first sacrificial layer to form vias therein as anchor locations.
Claim 8
Dependent Claim
16 words
The process of claim 1 wherein said first device layer is a P+boron doped epitaxial layer.
Claim 9
Dependent Claim
18 words
The process of claim 1 wherein said etch resistant impurity includes at least one of Germanium and Boron.
Claim 10
Dependent Claim
24 words
The process of claim 1 wherein said micromachined structure patterned in said first device layer includes a membrane for use as a pressure sensor.
Claim 11
Dependent Claim
65 words
The process of claim 1 further including the steps of depositing a second sacrificial layer of single crystal silicon over said first device layer and depositing a second device layer of single crystal silicon over said second sacrificial layer, and wherein said first device layer comprises a bottom of a hollow beam and said second device layer comprises a top and sides of said beam.
Claim 12
Dependent Claim
24 words
The process of claim 1 wherein said micromachined structure patterned in said first device layer includes a see-saw accelerometer and a plurality of linkages.
Claim 13
Dependent Claim
24 words
The process of claim 1 further including the step of etching away selected portions of said second silicon substrate and said first device layer.
Claim 14
Dependent Claim
29 words
The process of claim 1 wherein said etch resistant impurity is at least one of arsenic and phosphorous and said first sacrificial layer is etched away by electrochemical etching.
Claim 15
Dependent Claim
24 words
The process of claim 12 wherein selected portions of said second silicon substrate and said first device layer are etched away by electrochemical etching.
Claim 16
Dependent Claim
27 words
The process of claim 1 wherein said micromachined structure patterned in said first device layer includes at least portions of a gyroscope and a plurality of linkages.
Claim 17
Dependent Claim
29 words
The process of claim 1 further including the steps of doping said first silicon substrate to form electrodes and aligning said first silicon substrate with said second silicon substrate.
Claim 18
Dependent Claim
32 words
The process of claim 16 wherein said first silicon substrate is doped to form a silicon z bar and said micromachined structure fabricated according to said process is a double gimbal gyroscope.
Claim 19
Dependent Claim
19 words
The process of claim 1 wherein said electrode regions are anchored to said dielectric surface by said diffusing step.
Claim 20
Dependent Claim
15 words
The process of claim 1 wherein said step of etching is performed using EDP etching.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-03-09 | 2001-09-08 | 2002-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-03-09 | 2005-09-08 | 2006-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-03-09 | 2009-09-08 | 2010-03-10 | $7700.00 | Window Closed / Lapsed |