Patent US1534663A successfully refreshed from Google Patents.
US5129983A
Expired / Lapsed
US
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Method of fabrication of large area micromechanical devices
Assignee: Charles Stark Draper Laboratory Inc
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Filing: 1991-02-25
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Granted: 1992-07-14
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Expires: 2011-02-25
Abstract
Abstract A method of fabrication of micromechanical devices enables the production of large area micromechanical transducer structures which are symmetric, stress balanced structures relatively devoid of geometric distortions. Micromechanical transducer structures are fabricated implementing processes and physical characteristics which overcome the unbalanced stresses occurring in high concentration diffusion planar structures that cause problematic geometric distortions that restrict physical size. Large increases in the practical size of micromechanical devices which may be fabricated are achieved while permitting greater depths of structural features, without the resultant concentration and stress distortions. Multilevel, balanced stress structures can be created which are of varying geometries at each level to produce a "sculpted" structure.
Inventors
- 👤 Paul Greiff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 12:52
CPC Classifications
B; B81; B81B; B81B3/00; B81B3/0064; B81B3/0067; B81B3/0072; G; G01; G01P; G01P15/00; G01P15/02; G01P15/08; G01P15/0802; B81B2201/00; B81B2201/02; B81B2201/0228; B81B2201/0235; B81C; B81C2201/00; B81C2201/01; B81C2201/0101; B81C2201/0128; B81C2201/013; B81C2201/0135; B81C2201/014
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
148 words
A method of creating a balanced stress micromechanical structure having at least first, second and third sides, wherein said structure is defined by diffusing a mass of silicon with a dopant, said method comprising the steps of: etching a tub in said mass of silicon, said tub defining at least one of said at least first, second and third sides of said structure; doping said tub by applying an etch stop diffusion comprising said dopant to all exposed surfaces of said tub; filling said tub with a silicon backfill to create a filled surface defining at least another of said first, second and third sides; diffusing said filled surface with said dopant to create an envelope having a sealed relatively lightly doped interior bulk, said envelope comprising said at least first, second and third sides; and etching said balanced stress micromechanical structure free from said mass of silicon.
Claim 2
Independent Claim
148 words
A method of creating a balanced stress micromechanical structure having at least first, second and third sides, wherein said structure is defined by diffusing a mass of silicon with a dopant, said method comprising the steps of: etching a tub in said mass of silicon, said tub defining at least one of said at least first, second and third sides of said structure; doping said tub by applying an etch stop diffusion comprising said dopant to all exposed surfaces of said tub; filling said tub with a silicon backfill to create a filled surface defining at least another of said first, second and third sides; diffusing said filled surface with said dopant to create an envelope having a sealed relatively lightly doped interior bulk, said envelope comprising said at least first, second and third sides; and etching said balanced stress micromechanical structure free from said mass of silicon.
Claim 3
Dependent Claim
21 words
The method of claim 1 wherein said mass of silicon is an N type silicon mass and said dopant is boron.
Claim 4
Dependent Claim
27 words
The method of claim 1 further including the step of: lapping said filled surface to create a mirror smooth filled surface prior to diffusing said filled surface.
Claim 5
Dependent Claim
13 words
The method of claim 1 wherein said silicon backfill is single crystal silicon.
Claim 6
Dependent Claim
11 words
The method of claim 1 wherein said silicon backfill is polysilicon.
Claim 7
Dependent Claim
125 words
A balanced stress micromechanical structure having a selected shape and at least a first and a second selected dimension, comprising: a mass of silicon; means for selectively providing etch resistance to said mass of silicon to generate etch resistant silicon integral with said mass of silicon, said means for selectively providing etch resistance being disposed in at least one pattern to provide at least some patterned etch resistant silicon; wherein said mass of silicon is exposed to etching means for selectively etching said mass of silicon while retaining said at least some patterned etch resistant silicon; and means for preventing geometric distortion or said at least some patterned etch resistant silicon upon freeing said at least some patterned etch resistant silicon from said silicon mass.
Claim 8
Dependent Claim
125 words
A balanced stress micromechanical structure having a selected shape and at least a first and a second selected dimension, comprising: a mass of silicon; means for selectively providing etch resistance to said mass of silicon to generate etch resistant silicon integral with said mass of silicon, said means for selectively providing etch resistance being disposed in at least one pattern to provide at least some patterned etch resistant silicon; wherein said mass of silicon is exposed to etching means for selectively etching said mass of silicon while retaining said at least some patterned etch resistant silicon; and means for preventing geometric distortion or said at least some patterned etch resistant silicon upon freeing said at least some patterned etch resistant silicon from said silicon mass.
Claim 9
Dependent Claim
163 words
The balanced stress micromechanical structure of claim 6 wherein said means for preventing geometric distortion of said at least some patterned etch resistant silicon comprises: a first silicon surface; a first etch resistant surface disposed on said first silicon surface substantially in conformance with said at least one pattern to provide some of said at least some patterned etch resistant silicon as a lower surface; a first intermediate silicon fill disposed on said first etch resistant surface; and a second etch resistant surface disposed on said first intermediate silicon fill substantially in conformance with said at least one pattern to provide some of said at least some patterned etch resistant silicon as an upper surface wherein said at least some patterned etch resistant silicon defines said selected shape and wherein said first etch resistant surface, said intermediate silicon fill and said second etch resistant surface define at least one of said first and said second selected dimension of said balanced stess micromechanical structure.
Claim 10
Dependent Claim
68 words
The balanced stress micromechanical structure of claim 7 wherein said means for preventing geometric distortion of said at least some patterned etch resistant silicon further comprises: at least a second intermediate silicon fill disposed on an etch resistant surface; and at least a third etch resistant surface substantially in conformance with said at least one pattern to provide some of said at least some patterned etch resistant silicon.
Claim 11
Dependent Claim
18 words
The balanced stress micromechanical structure of claim 7 wherein said first silicon surface comprises a plurality of grooves.
Claim 12
Dependent Claim
22 words
The balanced stress micromechanical structure of claim 9 wherein said plurality of grooves have a substantially u-shaped cross-section formed by plasma etching.
Claim 13
Dependent Claim
22 words
The balanced stress micromechanical structure of claim 9 wherein said plurality of grooves have a substantially v-shaped cross-section formed by anisotropic etching.
Claim 14
Dependent Claim
20 words
The balanced stress micromechanical structure of claim 7 wherein said first intermediate silicon fill comprises epitaxially grown single crystal silicon.
Claim 15
Dependent Claim
17 words
The low net strain micromechanical structure of claim 7 wherein said first intermediate silicon fill comprises polysilicon.
Claim 16
Independent Claim
108 words
A method of creating a planar balanced stress micromechanical structure in a mass of silicon, said method comprising the steps of: etching a plurality of grooves in said mass of silicon; doping said plurality of grooves by applying an etch stop diffusion to all exposed surfaces of said grooves to create an etch resistant corrugated lower surface; filling said plurality of grooves with a silicon to create a filled surface of said planar balanced stress micromechanical structure; diffusing said filled surface with an etch stop diffusion to create an etch resistant upper planar surface; and etching said planar balanced stress micromechanical structure substantially free from said silicon mass.
Claim 17
Independent Claim
108 words
A method of creating a planar balanced stress micromechanical structure in a mass of silicon, said method comprising the steps of: etching a plurality of grooves in said mass of silicon; doping said plurality of grooves by applying an etch stop diffusion to all exposed surfaces of said grooves to create an etch resistant corrugated lower surface; filling said plurality of grooves with a silicon to create a filled surface of said planar balanced stress micromechanical structure; diffusing said filled surface with an etch stop diffusion to create an etch resistant upper planar surface; and etching said planar balanced stress micromechanical structure substantially free from said silicon mass.
Claim 18
Dependent Claim
31 words
The method of claim 14 wherein said step of etching said plurality of grooves in said mass of silicon includes performing anisotropic etching whereby said grooves have a substantially v-shaped cross-section.
Claim 19
Dependent Claim
32 words
The method of claim 14 wherein said step of etching said plurality of grooves in said mass of silicon includes performing plasma etching whereby said grooves have a substantially u-shaped cross section.
Claim 20
Dependent Claim
20 words
The method of claim 14 wherein applying said etch stop diffusion includes doping said plurality of grooves with boron dopant.
Claim 21
Dependent Claim
20 words
The method of claim 14 wherein said silicon used to create said filled surface is epitaxially grown single crystal silicon.
Claim 22
Dependent Claim
16 words
The method of claim 14 wherein said silicon used to create said filled surface is polysilicon.
Claim 23
Dependent Claim
25 words
The method of claim 14 wherein said step of etching said low net strain micromechanical structure substantially free from said silicon mass includes anisotropic etching.
Claim 24
Independent Claim
88 words
A method of fabricating a balanced stress micromechanical structure in a mass of silicon, said method comprising the steps of: applying a etch stop dopant in a pattern on a first surface of said mass of silicon; growing an intermediate layer of silicon over said etch stop dopant patterned on said first surface of said mass of silicon; applying a second etch stop dopant in a second pattern on said intermediated layer of silicon; and etching said balanced stress micromechanical structure substantially free from said mass of silicon.
Claim 25
Independent Claim
88 words
A method of fabricating a balanced stress micromechanical structure in a mass of silicon, said method comprising the steps of: applying a etch stop dopant in a pattern on a first surface of said mass of silicon; growing an intermediate layer of silicon over said etch stop dopant patterned on said first surface of said mass of silicon; applying a second etch stop dopant in a second pattern on said intermediated layer of silicon; and etching said balanced stress micromechanical structure substantially free from said mass of silicon.
Claim 26
Dependent Claim
12 words
The method of claim 21 wherein said etch stop dopant is boron.
Claim 27
Dependent Claim
17 words
The method of claim 21 wherein said intermediate layer of silicon is epitaxially grown single crystal silicon.
Claim 28
Dependent Claim
13 words
The method of claim 21 wherein said intermediate layer of silicon is polysilicon.
Claim 29
Dependent Claim
42 words
The method of claim 21 wherein said step of etching said balanced stress micromechanical structure substantially free from said mass of silicon includes anisotropically etching said mass of silicon to undercut said etch stop dopant in said pattern on said first surface.
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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) | 1995-07-14 | 1996-01-13 | 1996-07-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-07-14 | 2000-01-13 | 2000-07-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-07-14 | 2004-01-13 | 2004-07-14 | $7700.00 | Window Closed / Lapsed |