US5332441A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for gettering of particles during plasma processing
Assignee: International Business Machines Corp
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Filing: 1991-10-31
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Granted: 1994-07-26
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Expires: 2011-10-31
Abstract
Abstract Apparatus for plasma processing involving the gettering of particles having a high charge to mass ratio away from a semiconductor wafer are disclosed. In one aspect of the invention, magnets are used to produce a magnetic field which is transverse to an electric field to draw the negative particles away from the wafer to prevent the formation of a sheath which can trap the particles. In a second aspect of the invention, a power source is connected to the wafer electrode to maintain a negative charge on the wafer, thereby preventing negative particles from being drawn to the wafer surface when the plasma is turned off. In other embodiments of the invention, a low density plasma source is used to produce a large plasma sheath which permits particles to cross a chamber to be gettered. A low density plasma discharge followed by a pulse to a higher density is used to overcome the negative effect of an insulating layer between the wafer and the wafer electrode.
Inventors
- 👤 Michael S. Barnes
- 👤 Dennis K. Coultas
- 👤 John C. Forster
- 👤 John H. Keller
- 👤 James A. O'Neill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 05:10
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/32; H01J37/32431; H01J2237/00; H01J2237/02; H01J2237/022; H01J2237/028
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
141 words
In a plasma processing system used in the manufacture of semiconductor circuits wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: at least one positive electrode adjacent said negative electrode on which the semiconductor wafer is mounted, said positive and negative electrodes generating an electric field; means for generating a magnetic field transverse to the electric field, negatively charged particles and ions being drawn to said positive electrode and thereby gettered from the plasma and the semiconductor wafer, said negatively charged particle being negatively charged by said plasma; and means for turning said plasma discharge off at periods which are short to the process time for a period which is long to the plasma decay time.
Claim 2
Dependent Claim
141 words
In a plasma processing system used in the manufacture of semiconductor circuits wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: at least one positive electrode adjacent said negative electrode on which the semiconductor wafer is mounted, said positive and negative electrodes generating an electric field; means for generating a magnetic field transverse to the electric field, negatively charged particles and ions being drawn to said positive electrode and thereby gettered from the plasma and the semiconductor wafer, said negatively charged particle being negatively charged by said plasma; and means for turning said plasma discharge off at periods which are short to the process time for a period which is long to the plasma decay time.
Claim 3
Dependent Claim
23 words
The gettering apparatus recited in claim 1 wherein said means for generating a magnetic field comprises magnets adjacent said at least one electrode.
Claim 4
Dependent Claim
140 words
In a plasma processing system used in the manufacture of semiconductor circuits wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: at least one positive electrode adjacent said negative electrode on which the semiconductor wafer is mounted, said positive and negative electrodes generating an electric field; and means for generating a magnetic field transverse to the electric field, negatively charged particles and ions being drawn to said positive electrode and thereby gettered from the plasma and the semiconductor wafer, said negatively charged particles being negatively charged by said plasma, wherein said plasma processing system comprises an ECR system and said means for generating a magnetic field comprises magnetic coils forming part of said ECR system.
Claim 5
Dependent Claim
140 words
In a plasma processing system used in the manufacture of semiconductor circuits wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: at least one positive electrode adjacent said negative electrode on which the semiconductor wafer is mounted, said positive and negative electrodes generating an electric field; and means for generating a magnetic field transverse to the electric field, negatively charged particles and ions being drawn to said positive electrode and thereby gettered from the plasma and the semiconductor wafer, said negatively charged particles being negatively charged by said plasma, wherein said plasma processing system comprises an ECR system and said means for generating a magnetic field comprises magnetic coils forming part of said ECR system.
Claim 6
Dependent Claim
24 words
The gettering apparatus recited in claim 1 further comprising means for pulsing said negative electrode more negative when said plasma discharge is turned off.
Claim 7
Dependent Claim
104 words
In a plasma processing system used in the manufacture of semiconductor circuits wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: an electrode connected to said negative electrode; means for turning off said radio frequency generated plasma discharge; and means for biasing negative said electrode connected to said negative electrode, said means for biasing maintaining a negative potential on said negative electrode when said plasma discharge is turned off, said negatively charged particles being negatively charged by said plasma.
Claim 8
Dependent Claim
104 words
In a plasma processing system used in the manufacture of semiconductor circuits wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: an electrode connected to said negative electrode; means for turning off said radio frequency generated plasma discharge; and means for biasing negative said electrode connected to said negative electrode, said means for biasing maintaining a negative potential on said negative electrode when said plasma discharge is turned off, said negatively charged particles being negatively charged by said plasma.
Claim 9
Dependent Claim
24 words
The apparatus recited in claim 5 wherein said means for biasing comprises a capacitor connected to said negative electrode through a radio frequency chose,
Claim 10
Dependent Claim
18 words
The apparatus recited in claim 5 wherein said means for biasing comprises a DC power supplied and diode.
Claim 11
Dependent Claim
123 words
In a plasma processing system used in the manufacture of semiconductor circuits, said plasma processing system including a chamber and wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: means for generating a low frequency, low power radio frequency signal for a time before or after termination of said plasma discharge; and means responsive to said means for generating a low frequency, low power radio frequency signal for generating a density secondary plasma discharge having a large sheath for allowing particles to cross the chamber to be gettered, said negatively charged particles being negatively charged by said plasma.
Claim 12
Dependent Claim
123 words
In a plasma processing system used in the manufacture of semiconductor circuits, said plasma processing system including a chamber and wherein a semiconductor wafer is mounted on a negative electrode and exposed to a radio frequency generated plasma discharge, an apparatus for gettering negatively charged particles and ions trapped in a plasma sheath comprising: means for generating a low frequency, low power radio frequency signal for a time before or after termination of said plasma discharge; and means responsive to said means for generating a low frequency, low power radio frequency signal for generating a density secondary plasma discharge having a large sheath for allowing particles to cross the chamber to be gettered, said negatively charged particles being negatively charged by said plasma.
Claim 13
Dependent Claim
34 words
The gettering apparatus recited in claim 8 further comprising at least one positive electrode adjacent said negative electrode on which the semiconductor wafer is mounted, said positive and negative electrodes generating an electric field.
Claim 14
Dependent Claim
45 words
The gettering apparatus recited in claim 8, further comprising means for maintaining said plasma discharge at a first power level and providing a pulse of a second power level, said first power level having a power level less than that of said second power level.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-07-25 | 1998-01-24 | 1998-07-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-07-25 | 2002-01-24 | 2002-07-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-07-25 | 2006-01-24 | 2006-07-26 | $7700.00 | Window Closed / Lapsed |