US4171242A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Neutral pH silicon etchant for etching silicon in the presence of phosphosilicate glass
Assignee: International Business Machines Corp
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Filing: 1978-03-08
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Granted: 1979-10-16
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Expires: 1998-03-08
Abstract
Abstract A silicon etchant is disclosed composed of an aqueous solution of a fluoride ion and oxygen maintained at a substantially neutral pH. The etchant eliminates the problems of stripping organic photoresists, maintaining silicon/phosphosilicate glass selectively, silicon surface pitting, oxide residues, and insoluble reaction products.
Inventors
- 👤 Cheng-Yih Liu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 06:04
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/60; H10P50/64; H10P50/642; C; C09; C09K; C09K13/00; C09K13/04; C09K13/08; H10P14/00; H10P14/60; H10P14/63; H10P14/6302; H10P14/6304; H10P14/6306; H10P50/20; H10P50/28; H10P50/282; H10P50/283
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
60 words
A method for preferentially etching a silicon workpiece in the presence of a phosphosilicate glass structure, comprising the steps of: applying to the surface of said silicon workpiece in the presence of said phosphosilicate glass structure, an aqueous solution of fluoride ions and oxygen atoms produced by an oxygen atom donor, maintained at a pH of between 6 and 8.2.
Claim 2
Independent Claim
60 words
A method for preferentially etching a silicon workpiece in the presence of a phosphosilicate glass structure, comprising the steps of: applying to the surface of said silicon workpiece in the presence of said phosphosilicate glass structure, an aqueous solution of fluoride ions and oxygen atoms produced by an oxygen atom donor, maintained at a pH of between 6 and 8.2.
Claim 3
Dependent Claim
45 words
The method of claim 1, wherein fluoride ions are in the form of a quaternary ammonium hydrofluoride compound having the generalized formula R 4 NH y F y-1 where y equals 0 or 1 and R can be an organic radical or a hydrogen radical.
Claim 4
Dependent Claim
33 words
The method of claim 1, wherein said fluoride ion compound comprises: a quaternary ammonium fluoride of the general description R 4 NF where R can be an organic radical or a hydrogen radical.
Claim 5
Dependent Claim
14 words
The method of claim 1, wherein said fluoride ion containing compound is hydrofluoric acid.
Claim 6
Dependent Claim
34 words
The method of claim 1, wherein said fluoride ion containing compound is a fluorine salt of the general description A p F q where p and q are integers and A is a cation.
Claim 7
Dependent Claim
14 words
The method of claim 1, wherein said oxygen atoms are produced by hydrogen peroxide.
Claim 8
Dependent Claim
16 words
The method of claim 1, wherein said oxygen atoms are derived from gaseous oxygen or ozone.
Claim 9
Dependent Claim
141 words
The method of claim 1, wherein said oxygen atoms are derived from oxygen containing compounds selected from the group consisting of: H 2 bo 3 - , ch 3 coo - , h 2 aso 4 - , hasO 4 2- , AsO 4 3- , NO 2 - , SO 3 2- , H 2 PO 4 - , HPO 4 2- , PO 4 3- , SO 4 2- , CO 3 2- , HCO 3 - , HCOO - , ClO 4 - , OCl - , C 6 H 5 COO - , MnO 4 - , Cr 2 O 7 - , IO 3 - , BrO 3 - , H 2 -citrate - , H-citrate 2- , citrate 3- , oxalate 2- , tartrate 2- , malonate 2- , succinate 2- , phthalate 2- .
Claim 10
Dependent Claim
29 words
The method of claim 1, wherein a buffering agent is added to said solution to control the pH of the etching solution between a value of 6 and 8.2.
Claim 11
Dependent Claim
13 words
The method of claim 9, wherein said buffering agent is ammonium hydrogen phosphate.
Claim 12
Dependent Claim
44 words
The method of claim 1, wherein the relative proportion of the constituents are substantially one part by volume of 40 percent by weight concentrated ammonium fluoride, one part by volume of 30 percent by weight hydrogen peroxide, and one part by volume of water.
Claim 13
Dependent Claim
27 words
The method of claim 11, wherein monobasic ammonium phosphate is added to the solution to reduce the small pH value and enhance the etching rate of silicon.
Claim 14
Dependent Claim
76 words
The method of claim 12, wherein the relative proportion of the constituents is one part by volume of 40 percent by weight concentrated ammonium fluoride, one part by volume of 30 percent by weight hydrogen peroxide, and one half part by volume of a solution consisting of X percent by volume of an aqueous solution of 23 grams of monobasic ammonium phosphate per 100 ml of water and Y percent by volume of water, where X+Y-100.
Claim 15
Dependent Claim
19 words
The method of claim 9, wherein said buffering agent is a solution of ammonium hydrogen phosphate and ammonium hydroxide.
References Cited (Backward Citations)
US2847287A
Cited
US3041258A
Cited
US3194703A
Cited
US3434896A
Cited
US3497407A
Cited
US3930870A
Cited
US4052253A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-10-15 | 1983-04-16 | 1983-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-10-15 | 1987-04-16 | 1987-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-10-15 | 1991-04-16 | 1991-10-16 | $7700.00 | Window Closed / Lapsed |