US5213655A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device and method for detecting an end point in polishing operation
Assignee: International Business Machines Corp
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Filing: 1992-03-02
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Granted: 1993-05-25
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Expires: 2012-03-02
Abstract
Abstract The present invention relates to a method and apparatus for remotely detecting impedance. It is specifically adapted for use on a polishing machine wherein the end point of polishing for removing a surface layer during the processing of semiconductor substrates is detected. A first, or stationary coil having a high permeability core is wound having an air gap and an AC voltage is applied to the stationary coil to provide a magnetic flux in the air gap. A second coil is mounted for rotation on the polishing table, in a position to periodically pass through the air gap of the stationary coil as the table rotates. The second coil is connected at its opposite ends to contacts which are embedded in the surface of the polishing wheel. The contacts are positioned to engage the surface of the substrate which is being polished and provide a load on the second or rotating coil. The rotating coil, when it is in the air gap of the stationary coil, will perturb the flux field therein as a function of the resistance of the load caused by the contacts contacting either a conducting surface or a non-conducting surface. This perturbance of the flux field is measured as a change in the induced voltage in the stationary coil which in turn is converted to a signal which is processed to indicate the end point of polishing, the end point being when a metallic layer has been removed to expose a dielectric layer therebeneath or, conversely, when a dielectric layer has been removed to expose a metallic layer therebeneath.
Inventors
- 👤 Michael A. Leach
- 👤 Brian J. Machesney
- 👤 Edward J. Nowak
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:09
CPC Classifications
B; B24; B24B; B24B37/00; B24B37/005; B24B37/013; G; G01; G01B; G01B7/00; G01B7/02; G01B7/06; G01B7/10; G01B7/105
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
253 words
A method of determining the end point of a process for polishing a surface film on a substrate, wherein the surface film is progressively removed to reveal at least a portion of the substrate, comprising the steps of: providing a first circuit including a first core having ends which oppose each other and which are separated by an air gap, a first coil wound around said first core, and a current source connected electrically in parallel across said first coil to energize said first coil and induce a magnetic flux density within said air gap; providing a rotatable platform having a polishing device thereon, said polishing device being disposed to contact the surface of the material being polished, said rotatable platform carrying a second circuit including (i) a second core, (ii) a second coil wound around said second core, and (iii) a pair of electrical contacts connected electrically in parallel across said second coil and positioned so as to contact the surface of the material to be polished; contacting said material to be polished with said polishing device; rotating said platform to polish the material so as to selectively and periodically dispose said second coil within and outside of said air gap, thereby gradually removing the material until said substrate contacts said electrical contacts; sensing the resulting change in said magnetic flux density within said air gap when said substrate contacts said electrical contacts and providing an electrical signal in response thereto; and terminating the polishing process in response to said electrical signal.
Claim 2
Independent Claim
253 words
A method of determining the end point of a process for polishing a surface film on a substrate, wherein the surface film is progressively removed to reveal at least a portion of the substrate, comprising the steps of: providing a first circuit including a first core having ends which oppose each other and which are separated by an air gap, a first coil wound around said first core, and a current source connected electrically in parallel across said first coil to energize said first coil and induce a magnetic flux density within said air gap; providing a rotatable platform having a polishing device thereon, said polishing device being disposed to contact the surface of the material being polished, said rotatable platform carrying a second circuit including (i) a second core, (ii) a second coil wound around said second core, and (iii) a pair of electrical contacts connected electrically in parallel across said second coil and positioned so as to contact the surface of the material to be polished; contacting said material to be polished with said polishing device; rotating said platform to polish the material so as to selectively and periodically dispose said second coil within and outside of said air gap, thereby gradually removing the material until said substrate contacts said electrical contacts; sensing the resulting change in said magnetic flux density within said air gap when said substrate contacts said electrical contacts and providing an electrical signal in response thereto; and terminating the polishing process in response to said electrical signal.
Claim 3
Dependent Claim
33 words
The method of claim 1, wherein said current source is an alternating current source, and said change in magnetic field flux density is sensed as a change in voltage across said first coil.
Claim 4
Dependent Claim
108 words
The method of claim 1, wherein said first circuit includes (i) a plurality of first cores each having ends which oppose each other and which are separated by an air gap, (ii) a corresponding number of first coils wound around said first cores, said pluralities of coils and cores being arranged as an impedance bridge, and (iii) a current source connected electrically in parallel across said impedance bridge to energize said first coils and induce substantially similar magnetic flux densities within said air gaps, and wherein said change in said magnetic flux density is sensed as a function of an imbalance in the impedance of said impedance bridge.
Claim 5
Dependent Claim
37 words
The method of claim 1, further comprising the step of processing said electrical signal provided in response to said sensed change in magnetic flux density to determine the surface area of surface film remaining on said substrate.
Claim 6
Dependent Claim
20 words
The method of claim 4, wherein said step of processing said electrical signal includes the step of integrating said signal.
Claim 7
Dependent Claim
74 words
The method of claim 1, wherein said step of contacting said material to be polished with said polishing device comprises positioning a material to be abraded on said rotatable platform surface adjacent to said electrical contacts, said material comprising an electrically nonconductive substrate and an electrically conductive layer deposited thereon, and wherein said step of rotating said platform comprises progressively abrading said electrically conductive layer until said electrically nonconductive substrate contacts said electrical contacts.
Claim 8
Dependent Claim
78 words
The method of claim 6, further comprising the steps of outputting as an electrical signal the result obtained by sensing said voltage drop across said impedance bridge, integrating said electrical signal to determine the relative time periods during which said electrical contacts are open and closed, comparing said integrated electrical signal with a reference signal to determine when said progressive abrading of said electrically conductive layer is complete, and outputting a control signal in response to said comparison.
Claim 9
Dependent Claim
17 words
The method of claim 7, wherein said electrical signal is rectified and filtered prior to being integrated.
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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) | 1996-05-24 | 1996-11-23 | 1997-05-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-05-24 | 2000-11-23 | 2001-05-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-05-24 | 2004-11-23 | 2005-05-25 | $7700.00 | Window Closed / Lapsed |