Claims
- 1. A method of monitoring a thickness of a conductive layer in a substrate during a polishing operation, comprising:
positioning a substrate on a first side of a polishing surface; generating an alternating magnetic field from an inductor positioned on a second side of the polishing surface opposite the substrate, the magnetic field extending through the polishing surface to induce eddy currents in the conductive layer; and detecting a change in the alternating magnetic field caused by a change in the thickness of the conductive layer.
- 2. The method of claim 1, wherein generating the alternating magnetic field from an inductor includes driving a first coil with an oscillator at a first frequency.
- 3. The method of claim 2, wherein the first frequency is a resonant frequency when the substrate is not in proximity to the magnetic field.
- 4. The method of claim 2, wherein detecting a change in the alternating magnetic field includes sensing the alternating magnetic field with a second coil.
- 5. The method of claim 4, wherein the second coil is connected in parallel with a capacitor.
- 6. The method of claim 4, wherein the first coil is wound around a first portion of a core and the second coil is wound around a second portion of the core.
- 7. The method of claim 1, wherein generating the alternating magnetic field includes directing the magnetic field through a core positioned at least partially in a recess in a polishing pad.
- 8. The method of claim 1, further comprising determining when the inductor is adjacent the substrate.
- 9. The method of claim 8, wherein determining when the inductor is adjacent the substrate includes using an optical interrupter.
- 10. The method of claim 8, wherein determining when the inductor is adjacent the substrate includes using an encoder.
- 11. The method of claim 1, wherein generating an alternating magnetic field from an inductor includes driving the inductor with a first signal, and detecting a change in the alternating magnetic field includes generating a second signal from the alternating magnetic field.
- 12. The method of claim 11, further comprising determining a change in amplitude in the second signal.
- 13. The method of claim 11, further comprising determining a change in a phase difference between the first signal and the second signal.
- 14. A method of chemical mechanical polishing, comprising:
positioning a substrate having a conductive layer on a first side of a polishing surface; generating an alternating magnetic field from an inductor positioned on a second side of the polishing surface opposite the substrate, the magnetic field extending through the polishing surface to induce eddy currents in the conductive layer; creating relative motion between the substrate and the polishing surface to polish the conductive layer; sensing the eddy currents in the substrate; and halting polishing when the sensed eddy currents exhibit an endpoint criteria.
- 15. The method of claim 14, wherein the endpoint criteria comprises the eddy current signal passing a threshold strength.
- 16. The method of claim 14, wherein the endpoint criteria comprises a slope of the eddy current signal leveling off.
- 17. The method of claim 14, wherein the endpoint criteria comprises a change in slope of the eddy current signal.
- 18. The method of claim 14, wherein the endpoint criteria comprises a local minima or local maxima of the eddy current signal.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of and claims priority under 35 USC 120 to U.S. application Ser. No. 09/574,008, filed on May 19, 2000, the entire disclosure of which is incorporated herein by reference.
Divisions (1)
|
Number |
Date |
Country |
Parent |
09574008 |
May 2000 |
US |
Child |
10446367 |
May 2003 |
US |