System for MEMS inspection and characterization

• US 6,753,528 B1
• Filed: 04/18/2002
• Issued: 06/22/2004
• Est. Priority Date: 04/18/2002
• Status: Expired due to Term

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Zhao, Guoheng, Nikoonahad, Mehrdad
• Primary Examiner(s): GAGLIARDI, ALBERT J
• Application Number:
  US10/125,820
• Time in Patent Office: 796 Days
• Field of Search: 250/341.1, 250/339.11, 250/341.4, 250/341.8
• US Class Current: 250/341.1
• CPC Class Codes: B81C 99/005 Test apparatus

Abstract

A surface of the component in MEMS is illuminated by an illumination beam and the reflected beam is collected and detected by a position sensitive detector or photo detector array. As the surface is tilted about a pivot or about X and Y axes, the change in position of the collected beam is detected for characterizing the mechanical and optical properties of MEMS.

Claims

1. An apparatus for detecting characteristics of a MEMS system component having a surface, comprising:

a source providing an illumination beam of radiation to illuminate a spot on the surface;

an instrument causing relative rotation by an angle between said beam and the surface about a pivot, or about at least one axis;

an optical collector collecting a beam of radiation from the beam caused by reflection from the surface of the illumination beam; and

a detector detecting a position of the collected radiation that results from the grotation to determine said characteristics, wherein the position of the collected radiation detected by the detector indicates the angle of the relative rotation between said beam and the surface.

2. The apparatus of claim 1, wherein said collector comprises an objective, said spot or said detector located at a focal point of said objective.

3. The apparatus of claim 2, wherein said objective comprises a lens.

4. The apparatus of claim 1, further comprising an objective that collimates or focuses the beam to illuminate the spot on the surface.

5. The apparatus of claim 1, wherein said collector comprises an objective that collimates or focuses radiation from the source to form the illumination beam and collects the reflected beam from the surface.

6. The apparatus of claim 1, further comprising a circuit processing an output of the detector to determine optical characteristics of the component.

7. The apparatus of claim 6, said instrument causing the surface to move in response to a signal, wherein said circuit processes an output of the detector according to a characteristic of the signal.

8. The apparatus of claim 7, wherein said instrument causes the surface to oscillate at at least one frequency, said circuit comprising a filter filtering the output of the detector to provide a filtered DC signal.

9. The apparatus of claim 8, wherein said instrument causes the surface to oscillate at a frequency that changes over time.

10. The apparatus of claim 8, wherein the circuit derives frequency response of the component along each of two axes transverse to each other.

11. The apparatus of claim 1, wherein said detector provides two pairs of outputs, each pair corresponding to the position of the collected beam along one of two axes transverse to each other.

12. The apparatus of claim 11, wherein said circuit derives sum and difference of each pair of signals.

13. The apparatus of claim 12, wherein said circuit derives sum of the two pairs of signals to obtain a measure of the reflectivity of said surface.

14. The apparatus of claim 13, further comprising a second detector detecting an intensity related to the intensity of the illumination beam, wherein said circuit normalizes sum of the two pairs of signals using the detected intensity from the second detector.

15. The apparatus of claim 12, wherein said circuit derives a normalized difference between the signals in each pair from said sums and differences.

16. The apparatus of claim 1, wherein said detector comprises a position sensitive detector along two axes that are transverse to each other.

17. The apparatus of claim 1, wherein the MEMS system is used in an optical device, and the radiation of said illumination beam comprises at least one wavelength component used in the device.

18. The apparatus of claim 17, wherein the at least one wavelength component has a wavelength of about 1.55 or 1.31 micron.

19. The apparatus of claim 1, further comprising a device detecting an anomaly of or on the surface.

20. The apparatus of claim 19, said device comprising a microscope.

21. The apparatus of claim 1, said illumination beam being a focused beam focused to a spot on the surface, said apparatus further comprising a stage that causes relative translational motion between the illumination beam and the surface so that the spot is scanned over the surface, wherein outputs of the detector indicate a deformation characteristic of the surface.

22. The apparatus of claim 1, said instrument causing rotational motion of the surface about a pivot, or about one or more axes.

23. An method for detecting characteristics of a MEMS system component having a surface, comprising:

providing an illumination beam of radiation to illuminate a spot on the surface;

causing relative rotation by an angle between said beam and the surface about a pivot, or about at least one axis;

collecting a beam of radiation caused by reflection of the illumination beam by the surface; and

detecting a position of the collected beam in response to the rotation and determining the angle of the relative rotation between said beam and the surface and said characteristics.

24. The method of claim 23, wherein said providing and collecting employ a common objective.

25. The method of claim 24, wherein said providing comprises collimating or focusing radiation from a source to form the illumination beam.

26. The method of claim 23, wherein said collecting comprises collimating or focusing radiation from the spot to a detector that detects position of the collected beam in response to the rotation.

27. The method of claim 23, wherein said method further comprises processing information concerning position and/or intensity of the collected beam to determine optical and/or mechanical characteristics of the component.

28. The method of claim 27, wherein said causing causes the surface to move in response to a signal, wherein said processing processes said information according to a characteristic of the signal.

29. The method of claim 28, wherein said causing causes the surface to oscillate at at least one frequency, and wherein said processing comprises filtering the information to provide a DC filtered signal.

30. The method of claim 29, wherein said causing causes the surface to oscillate at a frequency that changes over time.

31. The method of claim 29, further comprising deriving frequency responses of the component along two axes transverse to each other.

32. The method of claim 23, wherein said detecting provides two pairs of outputs, each pair corresponding to position of the collected beam along one of two axes transverse to each other.

33. The method of claim 32, further comprising deriving sum and difference of each pair of signals.

34. The method of claim 33, wherein said deriving derives sum of two pairs of signals to obtain a measure of the reflectivity of said surface.

35. The method of claim 34, further comprising detecting an intensity related to the intensity of the illumination beam, and normalizing the sum of two pairs of signals using the detected intensity.

36. The method of claim 33, wherein said deriving derives a normalized difference between the signals in each pair from said sums and differences.

37. The method of claim 23, wherein said providing provides radiation comprising at least one wavelength component that is used in the MEMS system.

38. The method of claim 37, wherein the at least one wavelength component has a wavelength of about 1.55 or 1.31 micron.

39. The method of claim 23, further comprising detecting an anomaly of or on the surface.

40. The method of claim 39, wherein said anomaly detection employs a microscope.

41. The method of claim 23, wherein said causing causes rotational motion of the surface about a pivot, or about one or more axes.

42. The method of claim 23, said illumination beam being a focused beam focused to a spot on the surface, wherein said method further comprises causing relative translational motion between the illumination beam and the surface so that the spot is scanned over the surface, and wherein said detecting provides signals that indicate a deformation characteristic of the surface.

43. An apparatus for detecting characteristics of a MEMS system component having a surface, wherein a spot on the surface is illuminated by an illumination beam of radiation, and relative rotation by an angle is caused between said beam and the surface about a pivot, or about at least one axis, said apparatus comprising:

an optical collector collecting a beam of radiation from the beam caused by reflection from the surface of the illumination beam; and

a detector detecting a position of the collected radiation that results from the rotation to determine said characteristics, wherein the position of the collected radiation detected by the detector indicates the angle of the relative rotation between said beam and the surfac.

44. A method for detecting characteristics of a MEMS system component having a surface, wherein a spot on the surface is illuminated by an illumination beam of radiation, and relative rotation by an angle is caused between said beam and the surface about a pivot, or about at least one axis, said method comprising:

collecting a beam of radiation from the beam caused by reflection from the surface of the illumination beam; and

detecting a position of the collected radiation that results from the rotation and determining the angle of the relative rotation between said beam and the surface and said characteristics.

45. An apparatus for detecting deflection angle of a MEMS system component having a surface, comprising:

a source providing an illumination beam of radiation to illuminate a spot on the surface, wherein a reflection of the beam from the surface is caused by a stimulus to be deflected by an angle;

an optical collector collecting a beam of radiation from the beam caused by reflection from the surface of the illumination beam; and

a detector detecting a position of the collected radiation that results from the rotation, wherein the position of the collected radiation detected by the detector indicates precision of the deflection angle of said beam from the surface.

46. The apparatus of claim 45, wherein said detector also detects reflectivity of the surface.

47. The apparatus of claim 45, wherein the MEMS system is used in an optical device, and the radiation of said illumination beam comprises at least one wavelength component used in the device.

48. The apparatus of claim 47, wherein the at least one wavelength component has a wavelength of about 1.55 or 1.31 micron.

49. The apparatus of claim 45, wherein said detector also detects frequency response of the rotation.

50. A method for detecting deflection angle of a MEMS system component having a surface, comprising:

providing an illumination beam of radiation to illuminate a spot on the surface, wherein a reflection of the beam from the surface is caused by a stimulus to be deflected by an angle;

collecting a beam of radiation from the beam caused by reflection from the surface of the illumination beam; and

detecting a position of the collected radiation that results from the rotation, wherein the position of the collected radiation detected by the detector indicates precision of the deflection angle of said beam from the surface.

51. The method of claim 50, wherein the detecting also detects reflectivity of the surface.

52. The method of claim 50, wherein the MEMS system is used in an optical device, and the radiation of said illumination beam comprises at least one wavelength component used in the device.

53. The method of claim 52, wherein the at least one wavelength component has a wavelength of about 1.55 or 1.31 micron.

54. The method of claim 50, wherein said detecting also detects frequency response of the rotation.