Polishing process monitoring method and apparatus, its endpoint detection method, and polishing machine using same

• US 6,425,801 B1
• Filed: 06/01/1999
• Issued: 07/30/2002
• Est. Priority Date: 06/03/1998
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Ohkawa, Katsuhisa, Hayashi, Yoshihiro, Mitsuhashi, Hideo, Onodera, Takahiro, Takeishi, Akira
• Primary Examiner(s): Hail, III, Joseph J.
• Assistant Examiner(s): MCDONALD, SHANTESE L
• Application Number:
  US09/324,080
• Time in Patent Office: 1,155 Days
• Field of Search: 451/5, 451/6, 451/8, 451/41, 451/285, 451/287, 451/288, 364/474.06
• US Class Current: 451/5
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/042 operating processes therefor
• CPC Class Codes: B24B 49/04 involving measurement of the workpiece at the place of grinding during grinding operation
• CPC Class Codes: B24B 49/12 involving optical means

Abstract

A polishing process monitoring apparatus of a semiconductor wafer is provided, which is capable of monitoring correctly the process independent of various factors affecting optical measurement, such as the configuration, material, and size of a layered structure on the wafer, and the geometric shapes of patterns and their arrangement for respective semiconductor chips. This apparatus is comprised of (a) a light irradiating means for irradiating a detection light beam to a semiconductor wafer, (b) a first light receiving means for receiving a specular-reflected light beam generated by reflection of the detection light beam at the wafer and for outputting a first signal according to an amount of the specular-reflected light beam, (c) a second light receiving means for receiving a scattered/diffracted light beam generated by scattering or diffraction of the detection light beam at the wafer and for outputting a second signal according to an amount of the scattered/diffracted light beam, and (d) a monitoring means for monitoring a polishing process of the wafer by using the first and second signals.

Claims

1. A polishing process monitoring apparatus comprising:

(a) a light irradiating means for irradiating a detection light beam to a semiconductor wafer;

(b) a first light receiving means for receiving a specular-reflected light beam generated by reflection of said detection light beam at said wafer and for outputting a first signal according to an amount of said specular-reflected light beam;

(c) a second light receiving means for receiving a scattered/diffracted light beam generated by scattering or diffraction of said detection light beam at said wafer and for outputting a second signal according to an amount of said scattered/diffracted light beam; and

(d) a monitoring means for monitoring a polishing process of said wafer by using said first and second signals.

2. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of comparing a mean value of said first signal for said specular-reflected light beam in a specific time period with a first threshold value, generating a first comparison result;

a step of comparing a mean value of said second signal for said scattered/diffracted light beam in said specific time period with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

3. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of calculating mean values of said first signal for said specular-reflected light beam during a specific time period after start of said polishing process;

a step of selecting one of said mean values of said first signal to define a first reference value;

a step of setting a difference or ratio between a mean value of said first signal and said first reference value in a subsequent specific time period as a first variation value;

a step of calculating mean values of said second signal for said scattered/diffracted light beam during said specific time periods after start of said polishing process;

a step of selecting one of said mean values of said second signal to define a second reference value;

a step of setting a difference or ratio between a mean value of said second signal and said second reference value in said subsequent specific time period as a second variation value;

a step of comparing said first variation value with said first threshold value, generating a first comparison result;

a step of comparing said second variation value with said second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

4. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of comparing a change of a mean value of said first signal for said specular-reflected light beam in a specific time period with a first threshold value, generating a first comparison result;

a step of comparing a change of a mean value of said second signal for said scattered/diffracted light beam in said specific time period with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

5. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of comparing a time-derivative of a mean value of said first signal for said specular-reflected light beam in a specific time period with a first threshold value, generating a first comparison result;

a step of comparing a time-derivative of a mean value of said second signal for said scattered/diffracted light beam in said specific time period with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

6. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of deriving maximum of said first signal for said specular-reflected light beam in a specific time period;

a step of deriving a maximum of said second signal for said scattered/diffracted light beam in said specific time period;

a step of comparing said maximum of said mean value of said first signal with a first threshold value, generating a first comparison result;

a step of comparing said maximum of said mean value of said second signal with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

7. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of deriving an amplitude of said first signal for said specular-reflected light beam in a specific time period;

a step of deriving an amplitude of said second signal for said scattered/diffracted light beam in said specific time period;

a step of comparing said amplitude of said first signal with a first threshold value, generating a first comparison result;

a step of comparing said amplitude of said second signal with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

8. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of deriving a dispersion of said first signal for said specular-reflected light beam in a specific time period;

a step of deriving a dispersion of said second signal for said structured/diffracted light beam in said specific time period;

a step of comparing said dispersion of said first signal with a first threshold value, generating a first comparison result;

a step of comparing said dispersion of said second signal with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

9. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of deriving a difference or ratio between maximum and mean values of said first signal for said specular-reflected light beam in a specific time period;

a step of deriving a difference or ratio between maximum and mean values of said second signal for said scattered/diffracted light beam in said specific time period;

a step of comparing said difference or ratio of said first signal with a first threshold value, generating a first comparison result;

a step of comparing said difference or ratio of said second signal with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

10. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of calculating mean values of said first signal for said specular-reflected light beam during specific time periods after start of said polishing process;

a step of calculating a difference between maximum and minimum values of said mean values of said first signal;

a step of calculating mean values of said second signal for said scattered/diffracted light beam during said specific time periods after start of said polishing process;

a step of calculating a difference between maximum and minimum values of said mean values of said second signal;

a step of comparing said difference of said first signal with a first threshold value, generating a first comparison result;

a step of comparing said difference of said second signal with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer.

11. The apparatus as claimed in claim 1, wherein said monitoring means performs

a step of comparing a mean value of said first signal for said specular-reflected light beam in a specific time period with a first threshold value, generating a first comparison result;

a step of comparing a mean value of said second signal for said scattered/diffracted light beam in said specific time period with a second threshold value, generating a second comparison result; and

a step of determining a polished state of said wafer based on said first and second comparison results, thereby monitoring said polishing process of said wafer;

wherein said step of determining said polished state of said wafer is carried out using a first number of times when said mean value of said first signal exceeds said first threshold value and a second number of times when said mean value of said second signal exceeds said second threshold value.

12. The apparatus as claimed in claim 1, further comprising a reflector for reflecting said specular-reflected light beam to form a reflected beam of said specular-reflected light beam;

said reflector being located on an optical axis of said specular-reflected light beam;

wherein said first light receiving means receives said reflected beam of said specular-reflected light beam.

13. The apparatus as claimed in claim 1, further comprising an optical condenser for condensing said detection light beam to have a smaller spot size on said wafer than that of a specific pattern on said wafer.

14. The apparatus as claimed in claim 1, further comprising at least one of an optical reflector for reflecting said scattered/diffracted light beam and an optical condenser for condensing said scattered/diffracted light beam;

wherein each of said optical reflector and said optical condenser is located on an optical axis of said specular-reflected light beam at a downstream position with respect to said first light receiving means or a reflector for reflecting said specular-reflected light beam to said first light receiving means.

15. The apparatus as claimed in claim 1, further comprising a slurry removing means for approximately removing a polishing slurry from an irradiated position on said wafer;

wherein said slurry removing means emits a stream of fluid toward said irradiated position or a position apart from said irradiated position along a specific direction by a specific distance.

28. A polishing machine for a semiconductor wafer, comprising:

a polishing process monitoring apparatus as claimed in one of claims 1 to 27; and

a polishing means for polishing said wafer.

16. A polishing process monitoring apparatus comprising:

(a) a light irradiating means for irradiating at least one detection light beam having different wavelengths from one another to a semiconductor wafer;

(b) a first light receiving means for receiving at least one specular-reflected light beam generated by reflection of said at least one detection light beams at said wafer and for outputting signals according to an amount of said at least one specular-reflected light beam; and

(c) a monitoring means for monitoring a polishing process of said wafer by using said signal.

17. The apparatus as claimed in claim 16, wherein said monitoring means performs

a step of comparing mean values of said signals for said specular-reflected light beams in a specific time period with a first threshold value, generating a comparison result; and

a step of determining a polished state of said wafer based on said comparison result, thereby monitoring said polishing process of said wafer.

18. The apparatus as claimed in claim 16, wherein said monitoring means performs

a step of calculating mean values of said signals for said specular-reflected light beams during a specific time period after start of said polishing process;

a step of defining said mean values of said signals as reference values;

a step of setting a difference or ratio between a mean value of each of said signals and a corresponding one of said reference values in a subsequent specific time period as a variation value;

a step of comparing said variation values of said signals with said corresponding threshold values, generating a comparison result; and

a step of determining a polished state of said wafer based on said comparison result, thereby monitoring said polishing process of said wafer.

19. The apparatus as claimed in claim 16, wherein said light irradiating means includes light irradiating elements for irradiating light beams having different wavelengths from one another as said detection light beams, said light irradiating elements being located on different optical axes;

and wherein said light receiving means includes light receiving elements for receiving respectively said specular-reflected light beams to output said signals, said light receiving elements being located on different optical axes.

20. A polishing process monitoring apparatus comprising:

(a) a light irradiating means for irradiating at least two detection light beams having different wavelengths from one another to semiconductor wafer;

(b) a first light receiving means for receiving at least two specular-reflected light beams generated by reflection of said at least two detection light beams at said wafer and for outputting a first signal according to an amount of said at least two specular-reflected light beams;

(c) a second light receiving means for receiving at least two scattered/diffracted light beams generated by scattering or diffraction of said at least two detection light beams at said wafer and for outputting a second signal according to amounts of said at least two scattered/diffracted light beams; and

(d) a monitoring means for monitoring a polishing process of said wafer by using said first and second signals.

21. The apparatus as claimed in claim 20, further comprising reflectors for reflecting said specular-reflected light beams to form reflected beams of said specular-reflected light beams;

said reflectors being located on optical axes of said specular-reflected light beams;

wherein said first light receiving means receives said reflected beams of said specular-reflected light beams.

22. The apparatus as claimed in claim 20, further comprising an optical condenser for condensing said detection light beams to have smaller spot sizes on said wafer than that of a specific pattern on said wafer.

23. The apparatus as claimed in claim 20, further comprising at least one of an optical reflector for reflecting said scattered/diffracted light beams and an optical condenser for condensing said scattered/diffracted light beams;

wherein each of said optical reflector and said optical condenser is located at a downstream position with respect to said first light receiving means or a reflector for reflecting said specular-reflected light beams to said first light receiving means.

24. The apparatus as claimed in claim 20, further comprising an irradiating means for irradiating said detection light beams along a same optical axis to said wafer;

and

a spectrum analyzer for receiving said specular-reflected beams to spectrum-analyze said specular-reflected beams.

25. The apparatus as claimed in claim 20, further comprising a slurry removing means for approximately removing a polishing slurry from an irradiated position on said wafer;

wherein said slurry removing means emits a stream of fluid toward said irradiated position or a position apart from said irradiated position along a specific direction by a specific distance.

26. A polishing process monitoring apparatus comprising:

(a) a light irradiating means for irradiating a detection light beam;

(b) a light condensing means for condensing said detection light beam to form a condensed light beam having a spot size smaller than a specific pattern size on said wafer, said light condensing means being located on an optical axis of said detection light beam;

(c) a light receiving means for receiving a specular-reflected light beam generated by reflection of said condensed light beam at said wafer and for outputting a signal according to an amount of said specular-reflected light beam; and

(d) a monitoring means for monitoring a polishing process of said wafer by using the signal.

27. The apparatus as claimed in claim 26, wherein said monitoring means performs

a step of deriving a difference or ratio between maximum and mean values of said signal for said specular-reflected light beam in a specific time period;

a step of comparing said difference or ratio of said first signal with a first value, generating a comparison result; and

a step of determining a polished state of said wafer based on said comparison result, thereby monitoring said polishing process of said wafer.

29. A polishing process monitoring method comprising the steps of:

(a) irradiating a detection light beam to a semiconductor wafer;

(b) receiving a specular-reflected light beam generated by reflection of said detection light beam at said wafer to output a first signal according to an amount of said specular-reflected light beam;

(c) receiving a scattered/diffracted light beam generated by scattering or diffraction of said detection light beam at said wafer to output a second signal according to an amount of said scattered/diffracted light beam; and

(d) processing said first and second signals to produce a resultant signal required for monitoring a polishing process of said wafer.

30. The method as claimed in claim 29, wherein said first signal is outputted according to an amount change of said specular-reflected light beam in said step (b) and said second signal is outputted according to an amount change of said scattered/diffracted light beam in said step (c).

31. A polishing process monitoring method comprising the steps of:

(a) irradiating at least two detection light beams having different wavelengths from one another to a semiconductor wafer;

(b) receiving at least two specular-reflected light beams generated by reflection of said at least two detection light beams at said wafer and for outputting signals according to amounts of said at least two specular-reflected light beams; and

(c) processing said signal to produce resultant signals required for monitoring a polishing process of said wafer.

32. A polishing process monitoring method comprising the steps of:

(a) irradiating at least two detection light beams having different wavelengths from one another to a semiconductor wafer;

(b) receiving at least two specular-reflected light beams generated by reflection of said at least two detection light beams at said wafer and for outputting first signals according to amounts of said at least two scattered/diffracted light beams;

(c) receiving at least two scattered/diffracted light beams generated by scattering or diffraction of said at least two detection light beams at said wafer and for outputting second signals according to an amount of said at least two scattered/diffracted light beams; and

(d) processing said first and second signals to produce resultant signals required for monitoring a polishing process of said wafer.

33. A polishing process monitoring method comprising the steps of:

(a) irradiating a detection light beam;

(b) condensing said detection light beam to form a condensed light beam having a spot size smaller than a specific pattern size on said wafer;

said light condensing means being located on an optical axis of said detection light beams;

(c) receiving a specular-reflected light beam generated by reflection of said condensed light beam at said wafer and for outputting a first signal according to an amount of said specular-reflected light beam; and

(d) processing said first signal to produce a resultant signal required for monitoring a polishing process of said wafer.

34. The method as claimed in claim 33, wherein further comprising a step of

(e) receiving a scattered/diffracted light beam generated by scattering or diffraction of said detection light beam at said wafer and for outputting a second signal according to an amount of said scattered/diffracted light beam;

wherein said first and second signals are processed in said step (d) to produce said resultant signal required for monitoring said polishing process of said wafer.