US4692223A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for polishing silicon wafers
Assignee: Siltronic AG
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Filing: 1986-05-05
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Granted: 1987-09-08
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Expires: 2006-05-05
Abstract
Abstract A process for polishing silicon wafers includes the step of carrying out last polishing step in the polishing operation in such a way that a protective film of silicon dioxide is produced on the surface of the polished wafer. The film does not interfere with e.g., the subsequent oxidation processes. The protective film protects the wafer surface from the many effects arising in subsequent processes which may unfavorably influence the quality of the surface.
Inventors
- 👤 Ingolf Lampert
- 👤 Herbert Jacob
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 05:36
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/02; C30B29/06; C25; C25D; C25D11/00; C25D11/02; C25D11/32; C30B33/00
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
73 words
In a process for polishing silicon wafer surfaces, the improvement comprising the steps of: initially polishing the wafer surface in a conventional manner under alkaline conditions until a high quality of said polished surface is achieved; and thereafter, without interruption of the polishing, continuing and completing the polishing operation under oxidizing conditions by adding an oxidizing agent or anodic oxidation, thereby producing a film of silicon dioxide on the polished silicon wafer surface.
Claim 2
Dependent Claim
73 words
In a process for polishing silicon wafer surfaces, the improvement comprising the steps of: initially polishing the wafer surface in a conventional manner under alkaline conditions until a high quality of said polished surface is achieved; and thereafter, without interruption of the polishing, continuing and completing the polishing operation under oxidizing conditions by adding an oxidizing agent or anodic oxidation, thereby producing a film of silicon dioxide on the polished silicon wafer surface.
Claim 3
Dependent Claim
21 words
The process according to claim 1, wherein the silicon dioxide film is produced with a thickness of at least 10 Å.
Claim 4
Dependent Claim
30 words
The process according to claim 1, wherein the silicon dioxide film is produced by anodic oxidation by means of a voltage source in a circuit with anodically poled silicon wafers.
Claim 5
Dependent Claim
34 words
The process according to claim 1, wherein the silicon dioxide film is produced with an oxidizer having a potential in alkaline solution in excess of approximately 0.52 volts measured against a standard hydrogen electrode.
Claim 6
Dependent Claim
28 words
The process according to claim 4, wherein the oxidizer is a member selected from the group consisting of permanganates, peroxodisulfates, hypobromites, hypochlorites, hydrogen peroxide, and a combination thereof.
Claim 7
Dependent Claim
29 words
The process according to claim 4, wherein the oxidizer is a member selected from the group consisting of sodium salts, potassium salts, stable ammonium salts, and a combination thereof.
Claim 8
Dependent Claim
17 words
The process according to claim 4, wherein the oxidizer is in the form of an aqueous solution.
Claim 9
Dependent Claim
35 words
The process according to claim 4, wherein the oxidizer is added to a polishing agent in an amount such that the oxidizer makes up from approximately 0.1 to 2.0% by volume of the polishing agent.
Claim 10
Dependent Claim
28 words
The process according to claim 8, wherein after the oxidizer is added to the polishing agent, polishing of the wafer continues for from approximately 0.5 to 5.0 minutes.
Claim 11
Dependent Claim
31 words
The process according to claim 3, wherein a polishing disk serves as a cathode and a closed circuit is formed by a polishing cloth impregnated with an ionically conductive polishing agent.
Claim 12
Dependent Claim
28 words
The process according to claim 10, wherein a voltage of from approximately -1 to +2 volts measured against a Calomel electrode is established between the anode and cathode.
Claim 13
Dependent Claim
25 words
The process according to claim 10, wherein a current density of from approximately 0.1 to 5 mA/cm 2 is established between the anode and cathode.
Claim 14
Dependent Claim
18 words
The process according to claim 1, wherein the silicon wafers have a diameter of at least 125 mm.
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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) | 1990-09-07 | 1991-03-09 | 1991-09-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-09-07 | 1995-03-09 | 1995-09-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-09-07 | 1999-03-09 | 1999-09-08 | $7700.00 | Window Closed / Lapsed |