Patent US4781853A successfully refreshed from Google Patents.
US4781853A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of enhancing silicon etching capability of alkali hydroxide through the addition of positive valence impurity ions
Assignee: Intersil Corp
•
Filing: 1986-12-01
•
Granted: 1988-11-01
•
Expires: 2006-12-01
Abstract
Abstract The ability of alkali hydroxide to etch silicon is enhanced by the controlled addition of metallic salts which readily dissociate in a strong base (pH>/=10) solution. When introduced into the alkali hydroxide (e.g. potassium hydroxide) solution, the controlled concentrations of additive metallic ions increase the electronegativity of the solution and thereby enhance its ability to attract electrons away from the silicon atoms within the crystal lattice being etched. By adding controlled levels of properly chosen electropositive ions, the rate at which the electrons are removed from the silicon atoms in the surface planes of the crystal lattice that are exposed to the etching solution can be controllably increased. As a result of removal of the electrons from the silicon atoms, the silicon atoms dissolve out of the crystal planes at rates modified by the degree of impurity addition, resulting in improved etching charcteristics and geometries over that of conventionally employed alkali hydroxide solution.
Inventors
- 👤 Robert K. Lowry
- 👤 Edward U. Adams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 20:56
CPC Classifications
C; C09; C09K; C09K13/00; C09K13/02
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
92 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide.
Claim 2
Dependent Claim
92 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide.
Claim 3
Dependent Claim
21 words
An etchant according to claim 1, wherein said alcoholic potassium hydroxide solution contains a concentration of 45% w/w of potassium hydroxide.
Claim 4
Dependent Claim
112 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein said metallic salt is one containing a cation selected from the group consisting of barium, lanthanum, and tin.
Claim 5
Dependent Claim
112 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein said metallic salt is one containing a cation selected from the group consisting of barium, lanthanum, and tin.
Claim 6
Dependent Claim
103 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein said metallic salt has a solubility in aqueous basic
Claim 7
Dependent Claim
103 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein said metallic salt has a solubility in aqueous basic
Claim 8
Dependent Claim
110 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein said dissolved salt is one containing a cation species whose ionization potential is grater than five.
Claim 9
Dependent Claim
110 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt the cation of which has a positive valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein said dissolved salt is one containing a cation species whose ionization potential is grater than five.
Claim 10
Dependent Claim
119 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positve valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein the concentration of said positive valence ion in said alcoholic solution of potassium hydroxide solution lies in a range of 50 ppm to 5,000 ppm.
Claim 11
Dependent Claim
119 words
An etchant for silicon comprising an alkali hydroxide solution containing a dissolved metallic salt, the cation of which has a positve valence of at least +2, that readily dissociates in a strong base solution and thereby supplies an added quantity of positive valence ions therein, which dissolved salt effectively increases the electronegativity of the alkali hydroxide solution such that the ability of the solution to attract electrons from the atoms of the silicon being etched and dissolved is enhanced, and wherein said alkali hydroxide solution comprises an alcoholic solution of potassium hydroxide, and wherein the concentration of said positive valence ion in said alcoholic solution of potassium hydroxide solution lies in a range of 50 ppm to 5,000 ppm.
References Cited (Backward Citations)
US2902419A
Cited
FR2376222A1
Cited
US4579591A
Cited
US4601784A
Cited
US4601783A
Cited
JPH1015975A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-11-01 | 1992-05-02 | 1992-11-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-11-01 | 1996-05-02 | 1996-11-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-11-01 | 2000-05-02 | 2000-11-01 | $7700.00 | Window Closed / Lapsed |