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1. WO1999002970 - DISPOSITIF PERMETTANT D'ANALYSER DES COUCHES MINCES EMPILEES SUR DES SEMI-CONDUCTEURS

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

What is claimed is:

1. A method of analyzing a sample having a multiple layer thin film stack thereon comprising the steps of:
measuring the sample using an off-axis ellipsometer which includes a stable narrow band wavelength source and generating first output signals;
measuring the response of the sample to reflected light from a broad band wavelength source and generating a plurality of second output signals corresponding to different wavelengths; and
determining the characteristics of the individual layers on the sample based on the first and second output signals using an algorithm wherein the first output signals are used to provide an accurate measure of the overall optical thickness of the stack in order to improve the accuracy of the analysis of the individual layers.

2. A method as recited in claim 1 wherein the narrow band wavelength source is defined by a gas discharge laser.

3. A method as recited in claim 1 wherein the narrow band wavelength source is defined by a laser diode.

4. A method as recited in claim 1 wherein the narrow band wavelength source is defined by a solid state laser.

5. A method as recited in claim 1 wherein said narrow band wavelength source is linearly polarized prior to striking the sample and wherein the polarization change on reflection is monitored using a rotating compensator and analyzer.

6. A method as recited in claim 1 wherein the step of measuring with a broad band wavelength source includes the step of illuminating the sample with multiple wavelengths of light simultaneously.

7. A method as recited in claim 1 wherein the step of measuring with a broad band wavelength source includes the step of illuminating the sample with multiple wavelengths of light sequentially.

8. A method as recited in claim 1 wherein the step of measuring the sample response to a broad band wavelength source includes analyzing the change in polarization state of the light induced by reflection off the surface of the sample.

9. A method as recited in claim 1 wherein the step of measuring the sample response to a broad band wavelength source includes analyzing the change in magnitude of the light induced by reflection off the surface of the sample.

10. A method as recited in claim 1 wherein the step of measuring the sample response to a broad band wavelength source includes light spanning a wavelength range of 200nm to 800nm.

11. A method as recited in claim 1 further including the step of measuring the response of the sample to reflected light at one or more wavelengths and at a plurality of different angles of incidence and generating third output signals and using the third output signals to further characterize the individual layers on the sample.

12. A method of determining the characteristics of individual layers in a thin film stack formed on a sample comprising the steps of:
generating a first probe beam defined by quasi-monochromatic light of a known wavelength;
directing the first probe beam to reflect off the surface of the sample at a non-normal angle of incidence;
analyzing the change in polarization state of the first probe beam induced by the interaction with the sample and generating first output signals in response thereto;
generating a second probe beam from a broad band wavelength source;
directing said second probe beam to reflect off the surface of the sample;
monitoring the second probe beam after reflection from the sample and determining either a phase or magnitude thereof at a plurality of wavelengths and generating a plurality of second output signals corresponding thereto; and
determining the characteristics of the individual layers on the sample based on the first and second output signals using an algorithm wherein the first output signals are used to provide an accurate measure of the overall optical thickness of the stack in order to improve the accuracy of the analysis of the individual layers.

13. A method as recited in claim 12 wherein said second probe beam is directed to the surface of the sample in a manner such that multiple wavelengths of light strike the surface simultaneously.

14. A method as recited in claim 12 wherein said second probe beam is directed to the surface of the sample in a manner such that multiple wavelengths of light strike the surface of the sample sequentially.

15. A method as recited in claim 12 wherein said step of monitoring the second probe beam includes analyzing the change in polarization state of the beam induced by reflection off the surface of the sample.

16. A method as recited in claim 12 wherein said step of monitoring the second probe beam includes analyzing the change in magnitude of the beam induced by reflection off the surface of the sample

17. A method as recited in claim 12 wherein the first probe beam is generated by a gas discharge laser.

18. A method as recited in claim 12 wherein the first probe beam is generated by a laser diode.

19. A method as recited in claim 12 wherein the first probe beam is generated by a solid state laser.

20. A method as recited in claim 12 wherein the light in said first probe beam is linearly polarized prior to striking the sample and wherein the polarization change on reflection is monitored using a rotating compensator and analyzer.

21. A method as recited in claim 12 wherein the broad band wavelength source includes light spanning a wavelength range of 200nm to 800nm.

22. A method as recited in claim 12 further including the step of measuring the response of the sample to reflected light at one or more wavelengths and at a plurality of different angles of incidence and generating third output signals and using the third output signals to further characterize the individual layers on the sample.

23. An apparatus for characterizing thin film layers in a stack formed on a sample comprising:
an off-axis ellipsometer, said ellipsometer having a quasimonochromatic source for generating a first probe beam of a known wavelength, said ellipsometer for measuring the change in polarization state of the first probe beam after reflection from the sample and generating first output signals corresponding thereto;
a broad band light source for generating a second probe beam;
a detector system for monitoring either the phase or magnitude changes of the second probe beam after interacting with the sample and generating a plurality of second output signals corresponding to a plurality of different wavelengths; and
processor for determining the characteristics of the individual layers on the sample based on the first and second output signals, said processor using an algorithm wherein the first output signals are used to provide an accurate measure of the overall optical thickness of the stack in order to improve the accuracy of the analysis of the individual layers.

24. An apparatus as recited in claim 23 wherein said second probe beam is directed to the surface of the sample in a manner such that multiple wavelengths of light strike the surface simultaneously.

25. An apparatus as recited in claim 23 wherein said second probe is directed to the surface of the sample in a manner such that multiple wavelengths of light strike the surface of the sample sequentially

26. An apparatus as recited in claim 23 wherein the detector system analyzes the change in polarization state of the second probe beam induced by reflection off the surface of the sample.

27. An apparatus as recited in claim 23 wherein the detector system analyzes the change in magnitude of the second probe beam induced by reflection off the surface of the sample.

28. An apparatus as recited in claim 23 wherein the detector system analyzes both the change in polarization state of the second probe beam induced by reflection off the surface of the sample and the change in magnitude of the second probe beam induced by reflection off the surface of the sample and wherein the processor uses the output signals generated by both measurements to further characterize the sample.

29. An apparatus as recited in claim 23 wherein the quasimonochromatic source is defined by a gas discharge laser.

30. An apparatus as recited in claim 23 wherein the quasimonochromatic source is defined by a helium-neon laser.

31. An apparatus as recited in claim 23 wherein the quasimonochromatic source is defined by a solid state laser.

32. An apparatus as recited in claim 23 wherein the quasimonochromatic source is defined by a laser diode.

33. An apparatus as recited in claim 23 wherein the light in said first probe beam is linearly polarized prior to striking the sample and wherein the polarization change on reflection is monitored using a rotating compensator and analyzer.

34. An apparatus as recited in claim 23 wherein the broad band wavelength source includes light spanning a wavelength range of 200nm to 800nm.

35. An apparatus as recited in claim 23 wherein the detector system further includes the step of measuring the response of the sample to reflected light at one or more wavelengths and at a plurality of different angles of incidence and generating third output signals and using the third output signals to further characterize the individual layers on the sample.

36. An apparatus as recited in claim 35 wherein said light which is measured at a plurality of different angles of incidence is generated by a laser.

37. The reference ellipsometer of claim 23, wherein the quasimonochromatic source produces light having a stable known wavelength to within 1 percent.

38. An optical apparatus for evaluating characteristics of a semiconductor test sample comprising:
a spectroscopic measurement module including a broadband light source for creating a probe beam directed to reflect off the test sample and including a detector for monitoring changes in either the polarization or magnitude of the reflected probe beam at multiple wavelengths;
a processor for evaluating the test sample based on the measured changes of the probe beam; and
a calibration module including a reference sample and an off-axxs ellipsometer having a wavelength stable, narrowband light source for measuring the reference sample and wherein said apparatus is arranged so that the reference sample is also measured by the spectroscopic module and wherein the processor utilizes the measurements of the reference sample by both the off-axis ellipsometer and the spectroscopic module to calibrate the spectroscopic module for subsequent
measurements of test samples.

39. An apparatus as recited in claim 38 wherein said spectroscopic module is a spectrophotometer wherein the changes in magnitude of the reflected probe beam are measured at a plurality of wavelengths.

40. An apparatus as recited in claim 38 wherein said spectroscopic module is a spectroscopic ellipsometer wherein changes in the polarization state of the probe beam are analyzed at a plurality of wavelengths.

41. An apparatus as recited in claim 38 wherein the narrowband light source is defined by a gas discharge laser.

42. An apparatus as recited in claim 41 wherein said gas discharge laser is a helium-neon laser.

43. An apparatus as recited in claim 38 wherein said narrowband light source is defined by a laser diode.

44. An apparatus as recited in claim 38 wherein the narrowband wavelength source produces light have a stable known wavelength to within one percent.

45. An apparatus as recited in claim 38 wherein the reference sample is defined by a substrate having an oxide layer thereon wherein the composition of the oxide is known prior to measurement while the thickness of the oxide layer is unknown prior to measurement.

46. A method of operating a spectroscopic apparatus to analyze the characteristics of a semiconductor test sample, wherein the spectroscopic apparatus includes a broadband light source for creating a probe beam directed to reflect off the test sample and including a detector to monitor changes in either the polarization or magnitude of the reflected probe beam at a plurality of wavelengths, said spectroscopic apparatus further including a calibration module incorporating an off-axis ellipsometer having a stable wavelength narrowband light source, said calibration module further including a reference sample, said method comprising the steps of:
measuring the reference sample with the narrowband light source of the off-axis ellipsometer;
measuring the reference sample with the broadband light source of the spectroscopic apparatus;
analyzing the characteristics of the reference sample using the measurements obtained from both the off -axis ellipsometer and spectroscopic apparatus;
comparing the analyses of the characteristics of the reference sample derived from measurements obtained from the off-axis ellipsometer and the spectroscopic apparatus;
calibrating the spectroscopic apparatus based on the comparison of the analyses of the characteristics of the reference sample; and
measuring and analyzing a test sample with the calibrated spectroscopic apparatus.

47. A method as recited in claim 46 wherein the spectroscopic apparatus operates to measure changes in the magnitude of the reflected probe beam at a plurality of wavelengths.

48. A method as recited in claim 46 wherein the spectroscopic apparatus operates to measure changes in the polarization state of the probe beam at a plurality of wavelengths.

49. A method as recited in claim 46 wherein the reference sample is defined by a substrate having an oxide layer thereon.

50. A method as recited in claim 49 wherein during said step of analyzing the reference sample, the thickness of the oxide layer of the reference sample determined based on the measurements made with the spectroscopic apparatus is compared with the thickness of the oxide layer determined based on the measurements made with the off-axis ellipsometer in order to calibrate the spectroscopic apparatus.