US5476819A
Expired / Lapsed
US
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Substrate anchor for undercut silicon on insulator microstructures
Assignee: Northrop Grumman Guidance and Electronics Co Inc
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Filing: 1994-06-01
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Granted: 1995-12-19
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Expires: 2014-06-01
Abstract
Abstract An accelerometer is fabricated by forming a proofmass and at least one associated hinge in a silicon substrate through a variety of a etching and bonding processes is disclosed. The processes entail ion implantation and formation of an oxide support layer below the proofmass, integrally bonding two complementary proofmass and substrate structures together, and then removing the oxide support layer to leave the proofmass supported by the hinge within the body of silicon material. The proofmass may be electrically connected to a lead extending through an etched recess in one of the substrates, and the proofmass may be electrically isolated or separated from the substrates by an oxide layer and by a change in conductivity type of the semiconductor material wherein the hinge is structurally mounted to the substrates. In a bond and etch back process, the wafer is processed, sawed in half, and then bonded together again wherein the complementary halves are joined to obtain the finished accelerometer. As part of the bond and etch-back process, an anchor for bridging the silicon substrate to an oxide support substrate includes using a selective epitaxy or non-selective epitaxy process to grow the polysilicon anchors.
Inventors
- 👤 Keith O. Warren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 10:53
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
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
245 words
A method of fabricating a solid state instrument comprising the steps of: providing a first semiconductor substrate having a buried oxide layer, a front covered with an oxide layer, and a semiconductor handle on a back; forming a shallow well through the front oxide and the semiconductor substrate; removing the front oxide layer; depositing a silicon nitride layer on the front; depositing a silicon nitride cap and an oxide cap in the shallow well; removing the silicon nitride cap and the front silicon nitride layer except for a silicon nitride patch underlying the oxide cap; providing a second semiconductor substrate having a front covered in an oxide layer, wherein the front oxide layer includes a slot covered with silicon nitride; bonding the first semiconductor substrate front to the second semiconductor substrate front, wherein the shallow well substantially aligns with the slot; removing the semiconductor handle of the first semiconductor substrate; forming a deep slot through the back of the first semiconductor substrate substantially overlying the silicon nitride patch and oxide cap; removing the oxide cap and partially removing the silicon nitride patch so that the deep slot is in communication with the shallow well and forms a cavity with a ledge, wherein a remaining silicon nitride patch covers the ledge; removing the silicon nitride within the slot and the remaining silicon nitride patch; depositing silicon inside the cavity; cutting the bonded first and second semiconductor substrates into two complementary structures; and joining the complementary structures.
Claim 2
Independent Claim
245 words
A method of fabricating a solid state instrument comprising the steps of: providing a first semiconductor substrate having a buried oxide layer, a front covered with an oxide layer, and a semiconductor handle on a back; forming a shallow well through the front oxide and the semiconductor substrate; removing the front oxide layer; depositing a silicon nitride layer on the front; depositing a silicon nitride cap and an oxide cap in the shallow well; removing the silicon nitride cap and the front silicon nitride layer except for a silicon nitride patch underlying the oxide cap; providing a second semiconductor substrate having a front covered in an oxide layer, wherein the front oxide layer includes a slot covered with silicon nitride; bonding the first semiconductor substrate front to the second semiconductor substrate front, wherein the shallow well substantially aligns with the slot; removing the semiconductor handle of the first semiconductor substrate; forming a deep slot through the back of the first semiconductor substrate substantially overlying the silicon nitride patch and oxide cap; removing the oxide cap and partially removing the silicon nitride patch so that the deep slot is in communication with the shallow well and forms a cavity with a ledge, wherein a remaining silicon nitride patch covers the ledge; removing the silicon nitride within the slot and the remaining silicon nitride patch; depositing silicon inside the cavity; cutting the bonded first and second semiconductor substrates into two complementary structures; and joining the complementary structures.
Claim 3
Dependent Claim
15 words
The method of claim 1, wherein the first semiconductor substrate further comprises an epitaxial silicon.
Claim 4
Dependent Claim
24 words
The method of claim 1, wherein the step of depositing the silicon nitride layer on the front further comprises low pressure chemical vapor deposition.
Claim 5
Dependent Claim
20 words
The method of claim 1, wherein the step of depositing a silicon nitride cap further comprises a lift off process.
Claim 6
Dependent Claim
19 words
The method of claim 1, wherein the step of removing the semiconductor handle further comprises grinding the semiconductor handle.
Claim 7
Dependent Claim
22 words
The method of claim 1, wherein the step of depositing silicon inside the cavity further comprises the step of selective epitaxy growth.
Claim 8
Dependent Claim
22 words
The method of claim 1, wherein the step of depositing silicon inside the cavity further comprises the step of non-selective epitaxy growth.
Claim 9
Dependent Claim
22 words
The method of claim 7, wherein the step of depositing the silicon further comprises the step of mechanical abrasion of the silicon.
Claim 10
Dependent Claim
21 words
The method of claim 1, wherein the step of forming a deep slot further comprises the step of reactive ion etching.
Claim 11
Dependent Claim
31 words
The method of claim 1, wherein the method further comprises the steps of etching the joined complementary structures with an etchant, and centrifuging the joined complementary structures to remove the etchant.
Claim 12
Independent Claim
208 words
A method of anchoring a semiconductor substrate to another semiconductor substrate during fabrication of a solid state instrument comprising the steps of: providing a first semiconductor substrate having a buried oxide layer, a front covered with an oxide layer, and a semiconductor handle on a back; removing the front oxide layer; depositing a silicon nitride layer on the front; depositing a silicon nitride cap and an oxide cap on the front; removing the silicon nitride cap and the front silicon nitride layer except for a silicon nitride patch underlying the oxide cap; providing a second semiconductor substrate having a front covered in an oxide layer, wherein the front oxide layer includes a slot covered with silicon nitride; bonding the first semiconductor substrate front to the second semiconductor substrate front, wherein the shallow well substantially aligns with the slot; removing the semiconductor handle of the first semiconductor substrate; forming a deep slot through the back of the first semiconductor substrate substantially overlying the silicon nitride patch and oxide cap; removing the oxide cap and partially removing the silicon nitride patch and forming a cavity with a ledge, wherein a remaining silicon nitride patch covers the ledge; removing the silicon nitride within the slot; and depositing silicon inside the cavity.
Claim 13
Independent Claim
208 words
A method of anchoring a semiconductor substrate to another semiconductor substrate during fabrication of a solid state instrument comprising the steps of: providing a first semiconductor substrate having a buried oxide layer, a front covered with an oxide layer, and a semiconductor handle on a back; removing the front oxide layer; depositing a silicon nitride layer on the front; depositing a silicon nitride cap and an oxide cap on the front; removing the silicon nitride cap and the front silicon nitride layer except for a silicon nitride patch underlying the oxide cap; providing a second semiconductor substrate having a front covered in an oxide layer, wherein the front oxide layer includes a slot covered with silicon nitride; bonding the first semiconductor substrate front to the second semiconductor substrate front, wherein the shallow well substantially aligns with the slot; removing the semiconductor handle of the first semiconductor substrate; forming a deep slot through the back of the first semiconductor substrate substantially overlying the silicon nitride patch and oxide cap; removing the oxide cap and partially removing the silicon nitride patch and forming a cavity with a ledge, wherein a remaining silicon nitride patch covers the ledge; removing the silicon nitride within the slot; and depositing silicon inside the cavity.
Claim 14
Dependent Claim
36 words
The method of claim 11, wherein the method further comprises the step of removing the remaining silicon nitride patch; and the step of depositing silicon inside the cavity further comprises the step of selective epitaxy growth.
Claim 15
Dependent Claim
22 words
The method of claim 11, wherein the step of depositing silicon inside the cavity further comprises the step of non-selective epitaxy growth.
Claim 16
Dependent Claim
22 words
The method of claim 13, wherein the step of non-selective epitaxy growth fills the cavity and substantially covers the buried oxide layer.
Claim 17
Dependent Claim
35 words
The method of claim 14, wherein the step of depositing silicon inside the cavity further comprises the step of exposing the cavity to a chemical selected from the group consisting of silane, trichlorosilane, or dichlorosilane.
Claim 18
Dependent Claim
30 words
The method of claim 15, wherein the step of depositing silicon inside the cavity further comprises the step of mechanical grinding of the deposited silicon covering the buried oxide layer.
Claim 19
Dependent Claim
23 words
The method of claim 16, wherein the step of depositing silicon inside the cavity further comprises the step of etching the deposited silicon.
Claim 20
Dependent Claim
60 words
The method of claim 11, wherein the method further comprises the steps of forming a shallow well through the front oxide and the semiconductor substrate; and wherein the step of depositing a silicon nitride cap and an oxide cap on the front further comprises the step of depositing the silicon nitride cap and the oxide cap in the shallow well.
Claim 21
Independent Claim
103 words
A method of anchoring two semiconductor substrates comprising the steps of: providing a first semiconductor substrate having a buried oxide layer and a front oxide layer covering a front of the first substrate; forming a deep slot through the buried oxide layer and into the first substrate; removing the front oxide layer; covering a portion of the deep slot with a silicon nitride layer; covering another portion of the deep slot with an oxide layer; removing the silicon nitride layer; and filling the deep trench with a semiconductor material so that said semiconductor material is anchored on a portion of a second substrate.
Claim 22
Independent Claim
103 words
A method of anchoring two semiconductor substrates comprising the steps of: providing a first semiconductor substrate having a buried oxide layer and a front oxide layer covering a front of the first substrate; forming a deep slot through the buried oxide layer and into the first substrate; removing the front oxide layer; covering a portion of the deep slot with a silicon nitride layer; covering another portion of the deep slot with an oxide layer; removing the silicon nitride layer; and filling the deep trench with a semiconductor material so that said semiconductor material is anchored on a portion of a second substrate.
Claim 23
Dependent Claim
26 words
The method of claim 19, wherein the method further comprises the step of patterning and reactive ion etching an outline of a proofmass in the substrate.
Claim 24
Dependent Claim
23 words
The method of claim 20, wherein the method further comprises the step of removing the front oxide layer and the buried oxide layer.
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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) | 1998-12-18 | 1999-06-19 | 1999-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-12-18 | 2003-06-19 | 2003-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-12-18 | 2007-06-19 | 2007-12-19 | $7700.00 | Window Closed / Lapsed |