US4491499A
Expired / Lapsed
US
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Optical emission end point detector
Assignee: AT&T Inc
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Filing: 1984-03-29
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Granted: 1985-01-01
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Expires: 2004-03-29
Abstract
Abstract A method for determining the optimum time at which a plasma etching operation should be terminated. The optical emission intensity (S 1 ) of the plasma in a narrow band centered about a predetermined spectral line, indicative of the gas phase concentration of a plasma etch product or reactant species. The optical emission intensity (S 2 ) of the plasma in a wide band centered about the predetermined spectral line, indicative of a background emission signal is also monitored. The intensity (S 1L ) of the spectral line is then determined in accordance with the equation S 1L =S 1 -k (αS 2 -S 1 ). The etching process is terminated when the monitored signal intensity (S 1L ) or its time derivative reaches a predetermined value.
Inventors
- 👤 Leslie G. Jerde
- 👤 Earl R. Lory
- 👤 Kevin A. Muething
- 👤 Len Y. Tsou
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:20
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/32; H01J37/32917; H01J37/32935; C; C23; C23F; C23F4/00; G; G01; G01N; G01N21/00; G01N21/62
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
141 words
A method for determining the time at which a plasma etching operation should be terminated, comprising the steps of: monitoring the optical emission intensity (S 1 ) of the plasma, in a narrow band centered about a predetermined spectral line, indicative of the gas phase concentration of a plasma etch product or reactant species; monitoring the optical emission intensity (S 2 ) of the plasma, in a wide band centered about the predetermined spectral line, indicative of an optical background emission signal; determining the intensity (S 1L ) of the spectral line in accordance with the equation: S.sub.1L =S.sub.1 -k (αS.sub.2 -S.sub.1) where: k=a constant set to a value to give optimum results; and α=a constant determined by optical and electrical responses of the two signal amplification channels; and terminating the etching process when (S 1L ) achieves a predetermined value.
Claim 2
Independent Claim
141 words
A method for determining the time at which a plasma etching operation should be terminated, comprising the steps of: monitoring the optical emission intensity (S 1 ) of the plasma, in a narrow band centered about a predetermined spectral line, indicative of the gas phase concentration of a plasma etch product or reactant species; monitoring the optical emission intensity (S 2 ) of the plasma, in a wide band centered about the predetermined spectral line, indicative of an optical background emission signal; determining the intensity (S 1L ) of the spectral line in accordance with the equation: S.sub.1L =S.sub.1 -k (αS.sub.2 -S.sub.1) where: k=a constant set to a value to give optimum results; and α=a constant determined by optical and electrical responses of the two signal amplification channels; and terminating the etching process when (S 1L ) achieves a predetermined value.
Claim 3
Dependent Claim
15 words
The method as set forth in claim 1, wherein: the material being etched is aluminum.
Claim 4
Dependent Claim
21 words
The method as set forth in claim 1, wherein: the wide band is approximately three times wider than the narrow band.
Claim 5
Dependent Claim
27 words
The method as set forth in claim 1, wherein: the plasma etching process is terminated when the time derivative of (S 1L ) achieves a predetermined value.
Claim 6
Dependent Claim
30 words
The method as set forth in claim 2, wherein: the narrow band is 1 nm and the wide band is 3 nm; and both bands are centered at 396.1 nm.
Claim 7
Dependent Claim
28 words
The method as set forth in claim 1, comprising the step of: determining the value of the constant k when S 1L =0 using the following formula: ##EQU5##
Claim 8
Independent Claim
146 words
An apparatus for determining the time at which a plasma etching operation should be terminated, comprising: means for monitoring the optical emission intensity (S 1 ) of the plasma, in a narrow band centered about a predetermined spectral line, indicative of the gas phase concentration of a plasma etch product or reactant species; means for monitoring the optical emission intensity (S 2 ) of the plasma, in a wide band centered about the predetermined spectral line, indicative of an optical background emission signal; means for determining the intensity (S 1L ) of the spectral line in accordance with the equation: S.sub.1L =S.sub.1 -k (αS.sub.2 -S.sub.1) where: k=a constant set to a value to give optimum results; and α=a constant determined by optical and electrical responses of the two signal amplification channels; and means for terminating the etching process when (S 1L ) achieves a predetermined value.
Claim 9
Independent Claim
146 words
An apparatus for determining the time at which a plasma etching operation should be terminated, comprising: means for monitoring the optical emission intensity (S 1 ) of the plasma, in a narrow band centered about a predetermined spectral line, indicative of the gas phase concentration of a plasma etch product or reactant species; means for monitoring the optical emission intensity (S 2 ) of the plasma, in a wide band centered about the predetermined spectral line, indicative of an optical background emission signal; means for determining the intensity (S 1L ) of the spectral line in accordance with the equation: S.sub.1L =S.sub.1 -k (αS.sub.2 -S.sub.1) where: k=a constant set to a value to give optimum results; and α=a constant determined by optical and electrical responses of the two signal amplification channels; and means for terminating the etching process when (S 1L ) achieves a predetermined value.
Claim 10
Dependent Claim
15 words
The apparatus as set forth in claim 7, wherein: the material being etched is aluminum.
Claim 11
Dependent Claim
21 words
The apparatus as set forth in claim 7, wherein: the wide band is approximately three times wider than the narrow band.
Claim 12
Dependent Claim
27 words
The apparatus as set forth in claim 7, wherein: the plasma etching process is terminated when the time derivative of (S 1L ) achieves a predetermined value.
Claim 13
Dependent Claim
30 words
The apparatus as set forth in claim 8, wherein: the narrow band is 1 nm and the wide band is 3 nm; and both bands are centered at 396.1 nm.
Claim 14
Dependent Claim
27 words
The apparatus as set forth in claim 7, comprising: means for determining the value of the constant k when S 1L =0 using the following formula: ##EQU6##
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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) | 1988-01-01 | 1988-07-02 | 1989-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-01-01 | 1992-07-02 | 1993-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-01-01 | 1996-07-02 | 1997-01-01 | $7700.00 | Window Closed / Lapsed |