Claims
- 1. In a workpiece processing system having a processing element and a carrier element configured to hold a workpiece against said processing element, a method for detecting the presence of extraneous material on said processing element during operation of said workpiece processing system, said method comprising the steps of:
- directing an interrogation signal at an area of said processing element proximate said carrier element;
- detecting a reflected signal produced in response to said interrogation signal;
- converting said reflected signal into a control signal;
- indicating the presence of said extraneous material proximate said area when said control signal is measured within a predetermined range; and
- refraining from indicating the presence of said extraneous material proximate said area when said control signal is not measured within said predetermined range.
- 2. A method according to claim 1, wherein said interrogation signal is generated by a substantially monochromatic light source.
- 3. A method according to claim 2, wherein said light source is an infrared LED emitter.
- 4. A method according to claim 1, wherein said indicating step indicates when said workpiece is dislodged from said carrier element and wherein said extraneous material comprises said workpiece.
- 5. A method according to claim 1, wherein said processing element comprises a polishing pad having a relatively planar polishing surface and said directing step directs said interrogation signal at an angle between 10 and 20 degrees relative to said polishing surface.
- 6. A method according to claim 1, further comprising the step of adjusting an operating parameter of said workpiece processing system in response to said indicating step.
- 7. A method according to claim 1, wherein said control signal has an associated analog voltage and said method further comprises the steps of:
- establishing a first range for said analog voltage indicative of a first number of processing elements having a first reflectivity range;
- establishing said predetermined range for said analog voltage such that said predetermined range is indicative of said extraneous material; and
- establishing a second range for said analog voltage indicative of a second number of processing elements having a second reflectivity range.
- 8. A method according to claim 1, wherein said workpiece processing system comprises a chemical mechanical planarization (CMP) system configured to perform a planarization procedure, and said method further comprises the steps of:
- directing a training signal at said area of said processing element proximate said carrier element prior to said planarization procedure;
- detecting a reflected training signal produced in response to said training signal;
- converting said reflected training signal into an output test signal having an analog voltage; and
- establishing a range for said analog voltage of said output test signal, said range being indicative of the reflectivity of said processing element.
- 9. A method according to claim 1, wherein
- said control signal has an electrical characteristic associated therein,
- said step of indicating occurs when said electrical characteristic is measured within said predetermined range; and
- said step of refraining occurs when said electrical characteristic is not measured within said predetermined range.
- 10. A method according to claim 9, wherein said electrical characteristic comprises an analog voltage.
RELATED APPLICATION
This application is a Divisional of application Ser. No. 08/781,132, filed Jan. 9, 1997, now U.S. Pat. No. 5,823,853 which is a Continuation-In-Part of application Ser. No. 08/683,150, filed Jul. 18, 1996, now U.S. Pat. No. 5,733,171 entitled "Methods and Apparatus for the In-Process Detection of Workpieces in a CMP Environment."
US Referenced Citations (24)
Divisions (1)
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Number |
Date |
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Parent |
781132 |
Jan 1997 |
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Continuation in Parts (1)
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Number |
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683150 |
Jul 1996 |
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