US4253907A
Expired / Lapsed
US
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Anisotropic plasma etching
Assignee: AT&T Inc
•
Filing: 1979-03-28
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Granted: 1981-03-03
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Expires: 1999-03-28
Abstract
Abstract Method of anisotropically etching a semiconductor substrate (32). The substrate (32) is placed in an evacuated reaction chamber (50) and exposed to a gas plasma (63) which has been excited with an AC source having a frequency greater than 0 Hz but less than 300 KHz. The pressure in the chamber, and chamber geometry, are such that the volume power density of the plasma is less than 0.01 W/cm3.
Inventors
- 👤 Peter D. Parry
- 👤 Leslie G. Jerde
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:20
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/20; H10P50/28; H10P50/282; H10P50/283; C; C23; C23F; C23F4/00; H10P50/24; H10P50/242; H10P50/26; H10P50/264; H10P50/266; H10P50/267; H10P50/268
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
116 words
A method of anisotropically etching a workpiece, said workpiece being positioned within an evacuated reaction chamber, the method comprising the steps of: creating a partial vacuum in said reaction chamber such that the pressure in said chamber is less than one torr; flowing a stream comprising at least one etchant gas through said chamber; exciting said stream, by the application of an alternating electric field thereto, to form a gaseous plasma having a volume power density less than 0.01 W/cm 3 , said alternating electric field having a frequency which is greater than 0 Hz but less than 100 KHz; and exposing said workpiece to said plasma for a predetermined time interval to etch said workpiece.
Claim 2
Independent Claim
116 words
A method of anisotropically etching a workpiece, said workpiece being positioned within an evacuated reaction chamber, the method comprising the steps of: creating a partial vacuum in said reaction chamber such that the pressure in said chamber is less than one torr; flowing a stream comprising at least one etchant gas through said chamber; exciting said stream, by the application of an alternating electric field thereto, to form a gaseous plasma having a volume power density less than 0.01 W/cm 3 , said alternating electric field having a frequency which is greater than 0 Hz but less than 100 KHz; and exposing said workpiece to said plasma for a predetermined time interval to etch said workpiece.
Claim 3
Dependent Claim
25 words
The method according to claim 1 wherein said alternating electric field has a frequency which is greater than 1000 Hz but less than 100 KHz.
Claim 4
Dependent Claim
19 words
The method according to claim 1 including the further step of: continuously cooling said workpiece during said etching process.
Claim 5
Dependent Claim
20 words
The method according to claim 1 wherein said etchant gas comprises a mixture of CF 4 and O 2 .
Claim 6
Dependent Claim
28 words
The method according to claim 4 wherein said mixture of CF 4 and O 2 is in the ratio of 85-95% CF 4 and 5-15% O 2 .
Claim 7
Dependent Claim
14 words
The method according to claim 1 wherein said etchant gas comprises CF 4 .
Claim 8
Dependent Claim
14 words
The method according to claim 1 wherein said etchant gas comprises CClF 3 .
Claim 9
Dependent Claim
42 words
The method according to claim 1 wherein said workpiece comprises a multilayer workpiece, at least the upper layer thereof being comprised of a semiconductor material selected from the group consisting of silicon, polysilicon, SiO 2 , and Si 3 N 4 .
Claim 10
Dependent Claim
11 words
The method according to claim 1 wherein said workpiece comprises aluminum.
Claim 11
Dependent Claim
26 words
The method according to claim 1 wherein said workpiece is a multilayered workpiece comprising at least a layer of a metal and a layer of silicon.
Claim 12
Dependent Claim
19 words
The method according to claim 10 wherein said metal is selected from the group consisting of tantalum and aluminum.
Claim 13
Dependent Claim
17 words
The method according to claim 1 wherein the pressure in said chamber is less than 200 millitorr.
Claim 14
Independent Claim
109 words
A method of anisotropically etching a workpiece, said workpiece being positioned within an evacuated reaction chamber, the method comprising the steps of: creating a gaseous plasma in said reaction chamber by the excitation of at least one etchant gas, said plasma having a volume power density less than 0.01 W/cm 3 and said excitation being effected by the application of an alternating electric field to said etchant gas, said alternating field having a frequency which is greater than 0 Hz but less than 300 KHz; and then exposing said workpiece to said gaseous plasma for a predetermined time interval at a reaction chamber pressure of less than one torr.
Claim 15
Independent Claim
109 words
A method of anisotropically etching a workpiece, said workpiece being positioned within an evacuated reaction chamber, the method comprising the steps of: creating a gaseous plasma in said reaction chamber by the excitation of at least one etchant gas, said plasma having a volume power density less than 0.01 W/cm 3 and said excitation being effected by the application of an alternating electric field to said etchant gas, said alternating field having a frequency which is greater than 0 Hz but less than 300 KHz; and then exposing said workpiece to said gaseous plasma for a predetermined time interval at a reaction chamber pressure of less than one torr.
Claim 16
Dependent Claim
25 words
The method according to claim 1 wherein said alternating electric field has a frequency which is greater than 1000 Hz but less than 300 KHz.
Claim 17
Dependent Claim
16 words
The method according to claim 13 wherein said workpiece is continuously cooled during the etching process.
Claim 18
Dependent Claim
17 words
The method according to claim 13 wherein said at least one etchant gas comprises CF 4 .
Claim 19
Dependent Claim
23 words
The method according to claim 13 wherein said at least one etchant gas comprises a mixture of CF 4 and O 2 .
Claim 20
Dependent Claim
24 words
The method according to claim 17 wherein said gases are in the ratio of from 85-95% CF 4 and from 5-15% O 2 .
Claim 21
Dependent Claim
17 words
The method according to claim 13 wherein said at least one etchant gas comprises CClF 3 .
Claim 22
Dependent Claim
42 words
The method according to claim 13 wherein said workpiece comprises a multilayer workpiece, at least the upper layer thereof being comprised of a semiconductor material selected from the group consisting of silicon, polysilicon, SiO 2 , and Si 3 N 4 .
Claim 23
Dependent Claim
11 words
The method according to claim 13 wherein said workpiece comprises aluminum.
Claim 24
Dependent Claim
26 words
The method according to claim 13 wherein said workpiece is a multilayered workpiece comprising at least a layer of a metal and a layer of silicon.
Claim 25
Dependent Claim
19 words
The method according to claim 22 wherein said metal is selected from the group consisting of aluminum and tantalum.
Claim 26
Dependent Claim
17 words
The method according to claim 13 wherein the pressure in said chamber is less than 200 millitorr.
Claim 27
Independent Claim
78 words
A method of anisotropically etching a workpiece, the method comprising the steps of: creating a gaseous plasma in an evacuated reaction chamber by exciting at least one etchant gas by the application of an alternating electric field thereto; and then adjusting the pressure in said reaction chamber such that the mean free path of neutral gas molecules in the reactor is greater than the thickness of the sheath which is naturally formed between the plasma and the workpiece.
Claim 28
Independent Claim
78 words
A method of anisotropically etching a workpiece, the method comprising the steps of: creating a gaseous plasma in an evacuated reaction chamber by exciting at least one etchant gas by the application of an alternating electric field thereto; and then adjusting the pressure in said reaction chamber such that the mean free path of neutral gas molecules in the reactor is greater than the thickness of the sheath which is naturally formed between the plasma and the workpiece.
Claim 29
Dependent Claim
17 words
The method according to claim 25 wherein said at least one etchant gas comprises CF 4 .
Claim 30
Dependent Claim
23 words
The method according to claim 25 wherein said at least one etchant gas comprises a mixture of CF 4 and O 2 .
Claim 31
Dependent Claim
17 words
The method according to claim 25 wherein said at least one etchant gas comprises CClF 3 .
Claim 32
Dependent Claim
42 words
The method according to claim 25 wherein said workpiece comprises a multilayer workpiece, at least the upper layer thereof being comprised of a semiconductor material selected from the group consisting of silicon, polysilicon, SiO 2 , and Si 3 N 4 .
Claim 33
Dependent Claim
11 words
The method according to claim 25 wherein said workpiece comprises aluminum.
Claim 34
Dependent Claim
26 words
The method according to claim 25 wherein said workpiece is a multilayered workpiece comprising at least a layer of a metal and a layer of silicon.
Claim 35
Dependent Claim
19 words
The method according to claim 31 wherein said metal is selected from the group consisting of aluminum and tantalum.
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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) | 1984-03-02 | 1984-09-01 | 1985-03-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-02 | 1988-09-01 | 1989-03-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-02 | 1992-09-01 | 1993-03-03 | $7700.00 | Window Closed / Lapsed |