Patent US5282924A successfully refreshed from Google Patents.
US5282924A
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Micromechanical sensor fabrication process
Assignee: International Business Machines Corp
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Filing: 1993-03-22
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Granted: 1994-02-01
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Expires: 2013-03-22
Abstract
Abstract A method for producing micromechanical sensors for the AFM/STM/MFM profilometry is described in which a multiple step mask of cantilever beam and tip is transferred step by step into the wafer substrate by reactive ion etching. A particular highly anisotropic etching step is used for etching and shaping of the tip. This process step uses an Ar/C12 ambient at a pressure of about 100 6 bar and a self bias voltage of about 300 V DC. The ratio of pressure to self bias voltage determines the concave shape of the tip side-walls. This etching step is followed by a thermal oxidation step. The oxidation is carried out for a time until the oxidation fronts at the thinnest point of the tip shaft touch each other. A stripping process with buffered hydrofluoric acid gently removes the thermally grown oxide. The oxidation process allows--via oxidation time--a modification of tip height and angle in an extremely controllable manner. To prevent sticking of the tip to the structure to be profiled the ratio of tip diameter to tip height should be about 1:10. Should this ratio be exceeded the tip has to be arranged on a pedestal. The structure, comprising a cantilever beam and a tip on pedestal, can be produced with the same but slightly modified process of the invention.
Inventors
- 👤 Thomas Bayer
- 👤 Johann Greschner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 01:56
CPC Classifications
G; G01; G01Q; G01Q60/00; G01Q60/24; G01Q60/38; B; B82; B82Y; B82Y35/00; G01Q60/02; G01Q60/04; G01Q60/08; G01Q60/10; G01Q60/16; Y; Y10; Y10S; Y10S977/00; Y10S977/84; Y10S977/849; Y10S977/86; Y10S977/875; Y10S977/878
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
188 words
A process of fabricating a micromechanical sensor for AFM/STM/MFM profilometry, which sensor includes a cantilever beam and a tip at one end of the cantilever beam, the process comprising the following steps: (a) producing a cantilever-beam-pattern mask of a desired cantilever beam pattern on a first side of a wafer, and a thinning-window mask on a second side of the wafer; (b) producing a tip-pattern mask of a desired tip pattern in the area of the cantilever-beam-pattern mask on the first side of the wafer; (c) etching through the thinning-window mask on the second side of said wafer to thin down the wafer to a desired thickness; (d) transferring the cantilever beam pattern defined by the cantilever-beam-pattern mask into said wafer by etching, and removing the cantilever-beam-pattern mask; (e) transferring the tip pattern defined by the tip-pattern mask in the area of said cantilever beam pattern into said wafer by etching to form a cantilever beam/tip blank; (f) thermally oxidizing exposed surfaces of the cantilever beam/tip blank to a desired thickness; and (g) removing oxide produced in step (f) by etching, thereby exposing the desired cantilever beam/tip structure.
Claim 2
Dependent Claim
188 words
A process of fabricating a micromechanical sensor for AFM/STM/MFM profilometry, which sensor includes a cantilever beam and a tip at one end of the cantilever beam, the process comprising the following steps: (a) producing a cantilever-beam-pattern mask of a desired cantilever beam pattern on a first side of a wafer, and a thinning-window mask on a second side of the wafer; (b) producing a tip-pattern mask of a desired tip pattern in the area of the cantilever-beam-pattern mask on the first side of the wafer; (c) etching through the thinning-window mask on the second side of said wafer to thin down the wafer to a desired thickness; (d) transferring the cantilever beam pattern defined by the cantilever-beam-pattern mask into said wafer by etching, and removing the cantilever-beam-pattern mask; (e) transferring the tip pattern defined by the tip-pattern mask in the area of said cantilever beam pattern into said wafer by etching to form a cantilever beam/tip blank; (f) thermally oxidizing exposed surfaces of the cantilever beam/tip blank to a desired thickness; and (g) removing oxide produced in step (f) by etching, thereby exposing the desired cantilever beam/tip structure.
Claim 3
Dependent Claim
40 words
The process according to claim 1, wherein the wafer substrate consists of single-crystalline silicon, and the layers on the first side and on the second side of the wafer consist of thermally-grown silicon dioxide, or sputtered oxide, or (PE)CVD oxide.
Claim 4
Dependent Claim
38 words
The process according to claim 2, wherein the desired cantilever beam pattern is defined in said silicon dioxide layer on the first side of said wafer, using a first photolithographic step and a wet or dry etching step.
Claim 5
Dependent Claim
29 words
The process according to claim 3, wherein simultaneously with said first photolithographic step and said etching step rectangular thinning-window openings are made on the second side of said wafer.
Claim 6
Dependent Claim
38 words
The process according to claim 3, wherein the desired tip pattern is defined in the area of the cantilever beam pattern in said silicon dioxide layer using a second photolithographic step and a wet or dry etching step.
Claim 7
Dependent Claim
47 words
The process according to claim 2, wherein prior to the mask structure transfer into the silicon wafer substrate of said substrate is thinned down by anisotropic etching from the second side of the wafer with aqueous KOH solution approxmitely 37.5 weight percent at about 80 degrees C.
Claim 8
Dependent Claim
66 words
The process according to claim 2, wherein the cantilever beam pattern is anisotropically etched into the silicon wafer substrate using a silicon dioxide mask and Ar/Cl 2 or He/Cl 2 as etch gas at a pressure of about 2 to 20 μbar; and wherein silicon dioxide mask is removed by etching with CF 4 as etch gas at a pressure of about 1 to 10 μbar.
Claim 9
Dependent Claim
67 words
The process according to claim 2, wherein the tip is anisotropically etched in the area of cantilever beam into the substrate and concurrently shaped, using silicon dioxide mask, and Ar/Cl 2 or He/Cl 2 as etch gas, and wherein silicon dioxide tip mask is removed by etching with CF 4 as etch gas at a pressure in the range of from about 1 to about 10 μbar.
Claim 10
Dependent Claim
38 words
The process according to claim 8, wherein the anisotropic etching step is performed at a pressure of about 100 μbar a self bias voltage of the reactor of about 300 V DC, to obtain a concave tip shape.
Claim 11
Dependent Claim
25 words
The process according to claim 9, wherein concurrently with the etching and shaping of the tip the cantilever beam is released from the silicon body.
Claim 12
Dependent Claim
56 words
The process according to claim 8, wherein the silicon structure resulting from the anisotropic dry etching steps is thermally oxidized at a temperature of at least about 1000° C. in water vapor, and wherein the thermally grown silicon dioxide is removed by wet etching in buffered hydrofluoric acid, thereby exposing the tip on the cantilever beam.
Claim 13
Dependent Claim
228 words
A process of fabricating a micromechanical sensor for AFM/STM/MFM profilometry, which sensor includes a cantilever beam and a tip projecting from a pedestal at one end of the cantilever beam, the process comprising the following steps: (a) producing a cantilever-beam-pattern mask of a desired cantilever beam pattern on a first side of a wafer, and a thinning-window mask on a second side of the wafer; (b) producing a tip-pattern mask of a desired tip pattern in the area of said first mask on the first side of the wafer; (c) etching through the thinning-window mask on the second side of said wafer to thin down the wafer to a desired thickness; (d) transferring the cantilever beam pattern defined by the cantilever-beam-pattern mask into said wafer by etching, and removing the cantilever-beam-pattern mask; (e) transferring the tip pattern defined by the tip-pattern mask in the area of said cantilever beam pattern into said wafer by etching to form a cantilever beam/tip blank; (f) thermally oxidizing exposed surfaces of the cantilever beam/tip blank to a desired thickness; and (g) removing oxide produced in step (f) from the horizontal surfaces of said cantilever beam pattern by etching, etching the pedestal into said substrate, and finally removing said oxide from the vertical surfaces of cantilever beam/tip structure, and the tip-pattern mask thereby exposing said tip on the pedestal on the cantilever beam.
Claim 14
Dependent Claim
228 words
A process of fabricating a micromechanical sensor for AFM/STM/MFM profilometry, which sensor includes a cantilever beam and a tip projecting from a pedestal at one end of the cantilever beam, the process comprising the following steps: (a) producing a cantilever-beam-pattern mask of a desired cantilever beam pattern on a first side of a wafer, and a thinning-window mask on a second side of the wafer; (b) producing a tip-pattern mask of a desired tip pattern in the area of said first mask on the first side of the wafer; (c) etching through the thinning-window mask on the second side of said wafer to thin down the wafer to a desired thickness; (d) transferring the cantilever beam pattern defined by the cantilever-beam-pattern mask into said wafer by etching, and removing the cantilever-beam-pattern mask; (e) transferring the tip pattern defined by the tip-pattern mask in the area of said cantilever beam pattern into said wafer by etching to form a cantilever beam/tip blank; (f) thermally oxidizing exposed surfaces of the cantilever beam/tip blank to a desired thickness; and (g) removing oxide produced in step (f) from the horizontal surfaces of said cantilever beam pattern by etching, etching the pedestal into said substrate, and finally removing said oxide from the vertical surfaces of cantilever beam/tip structure, and the tip-pattern mask thereby exposing said tip on the pedestal on the cantilever beam.
Claim 15
Dependent Claim
39 words
The process of claim 12, wherein the wafer substrate consists of single-crystalline silicon, and the layers on the first side and on the second side of the wafer consist of thermally-grown silicon dioxide, or sputtered oxide, or (PE)CVD oxide.
Claim 16
Dependent Claim
38 words
The process according to claim 13, wherein the desired cantilever beam pattern is defined in said silicon dioxide layer on the first side of said wafer, using a first photolithographic step and a wet or dry etching step.
Claim 17
Dependent Claim
28 words
The process according to claim 14, wherein simultaneously with said first photolithographic step and said etching step rectangular openings are made on the second side of said wafer.
Claim 18
Dependent Claim
38 words
The process according to claim 14, wherein the desired tip pattern is defined in the area of the cantilever beam pattern in said silicon dioxide layer using a second photolithographic step and a wet or dry etching step.
Claim 19
Dependent Claim
47 words
The process according to claim 13, wherein prior to the mask structure transfer into the silicon wafer wafer substrate of said substrate is thinned down by anisotropic etching from the second side of the wafer with aqueous KOH solution approximately 37.5 wt percent at about 80° C.
Claim 20
Dependent Claim
66 words
The process according to claim 13, wherein the cantilever beam pattern is anisotropically etched into the silicon wafer substrate using a silicon dioxide mask and Ar/Cl 2 or He/Cl 2 an etch gas at a pressure of about 2 to 20 μbar; and wherein silicon dioxide mask is removed by etching with CF 4 as etch gas at a pressure of about 1 to 10 μbar.
Claim 21
Dependent Claim
66 words
The process according to claim 13, wherein the tip is anisotropically etched in the area of cantilever beam into the substrate and concurrently shaped, using silicon dioxide mask, and Ar/Cl 2 or He/Cl 2 as etch gas, and wherein silicon dioxide tip mask is removed by etching with CF 4 as etch gas at a pressure in the range from about 1 to about 10 μbar.
Claim 22
Dependent Claim
38 words
A process according to claim 19, wherein the anisotropic etching step is performed at a pressure of about 100 μbar a self bias voltage of the reactor of about 300 V DC, thereby obtaining a concave tip shape.
Claim 23
Dependent Claim
25 words
The process according to claim 20, wherein concurrently with the etching and shaping of the tip the cantilever beam is released from the silicon body.
Claim 24
Dependent Claim
56 words
The process according to claim 19, wherein the silicon structure resulting from the anisotropic dry etching steps is thermally oxidized at a temperature of at least about 1000° C. in water vapor, and wherein the thermally grown silicon dioxide is removed by wet etching in buffered hydrofluoric acid, thereby exposing the tip on the cantilever beam.
Claim 25
Dependent Claim
51 words
The process according to claim 18, wherein following the transfer of the cantilever beam pattern into the silicon wafer substrate by reactive ion etching, the tip is anisotropically etched in the area of cantilever beam into the substrate, using silicon dioxide mask and Ar/Cl 2 or He/Cl 2 as etch gas.
Claim 26
Dependent Claim
32 words
The process according to claim 23, wherein in order to obtain a tip shaft with straight sidewalls the etching is carried out in Ar/Cl 2 at a pressure of about 10 μbar.
Claim 27
Dependent Claim
32 words
The process according to claim 23, wherein in order to obtain a tip shaft with concave sidewalls the etching is carried out in Ar/Cl 2 at a pressure of about 10 μbar.
Claim 28
Dependent Claim
62 words
The process according to claim 25, wherein the silicon structure is thermally oxidized at a temperature of at least about 1000° C. in water vapor, and wherein the thermally grown silicon dioxide is removed from the horizontal surfaces of cantilever beam and silicon substrate by anisotropic etching with CF 4 as etch gas at a pressure of about 1 to 10 μbar.
Claim 29
Dependent Claim
53 words
The process according to claim 26, wherein pedestal is etched to the desired depth into the cantilever beam substrate, using the silicon dioxide layers on the vertical surfaces of cantilever beam/tip structure and tip mask as masks, and Ar/Cl 2 or He/Cl 2 as etch gas at a pressure of about 10 μbar.
Claim 30
Dependent Claim
24 words
The process according to claim 27, wherein concurrently with the etching of pedestal (29) the cantilever beam is released from the wafer body (21).
Claim 31
Dependent Claim
20 words
The process according to claim 28, wherein the remaining silicon dioxide masks are removed by etching with buffered hydrofluoric acid.
Claim 32
Dependent Claim
18 words
The process according to claim 29, wherein the tip is pointed in a maskless argon ion etching process.
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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) | 1997-01-31 | 1997-08-02 | 1998-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-01-31 | 2001-08-02 | 2002-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-01-31 | 2005-08-02 | 2006-02-01 | $7700.00 | Window Closed / Lapsed |