Dual stage instrument for scanning a specimen

• US 5,948,972 A
• Filed: 10/11/1996
• Issued: 09/07/1999
• Est. Priority Date: 12/22/1994
• Status: Expired due to Term

• Current Assignee: Tencor Instruments (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Wheeler, William R., Samsavar, Amin, Eaton, Steven G.
• Primary Examiner(s): LARKIN, DANIEL SEAN
• Application Number:
  US08/730,641
• Time in Patent Office: 1,061 Days
• Field of Search: 73/105, 250/306, 250/307
• US Class Current: 73/105
• CPC Class Codes: G01B 3/008 Arrangements for controlling the measuring force
• CPC Class Codes: G01B 7/34 for measuring roughness or irregularity of surfaces
• CPC Class Codes: G01Q 10/02 Coarse scanning or positioning
• CPC Class Codes: G01Q 10/04 Fine scanning or positioning
• CPC Class Codes: G01Q 30/02 Non-SPM analysing devices, e.g. SEM [Scanning Electron Microscope], spectrometer or optical microscope
• CPC Class Codes: G01Q 70/06 Probe tip arrays
• CPC Class Codes: Y10S 977/834 Optical properties of nanomaterial, e.g. specified transparency, opacity, or index of refraction
• CPC Class Codes: Y10S 977/849 with scanning probe
• CPC Class Codes: Y10S 977/852 for detection of specific nanostructure sample or nanostructure-related property
• CPC Class Codes: Y10S 977/867 Scanning thermal probe
• CPC Class Codes: Y10S 977/868 with optical means
• CPC Class Codes: Y10S 977/872 Positioner
• CPC Class Codes: Y10S 977/874 Probe tip array

Abstract

A dual stage scanning instrument includes a sensor for sensing a parameter of a sample and coarse and fine stages for causing relative motion between the sensor and the sample. The coarse stage has a resolution of about 1 micrometer and the fine stage has a resolution of 1 nanometer or better. The sensor is used to sense the parameter when both stages cause relative motion between the sensor assembly and the sample, The sensor may be used to sense height variations of the sample surface as well as thermal variations electrostatic, magnetic, light reflectivity or light transmission parameters at the same time when height variation is sensed. By performing along scan at a coarser resolution and short scans a high resolution using the same probe tip or two probe tips at fixed relative positions, data obtained from the long and short scans can be correlated accurately.

Claims

1. An instrument for sensing a sample, comprising:

a probe having a sensing tip that does not emit or transmit light for sensing a parameter of the sample;

a coarse stage causing relative motion between the sensing tip and the sample;

a fine stage causing relative motion between the sensing tip and the sample; and

at least one controller controlling the two stages so that the relative motion caused by the coarse stage causes the sensing tip to scan across the surface of the sample when the sensing tip is sensing said parameter of the sample.

2. The instrument of claim 1, said fine stage having a resolution of one nanometer or better.

3. The instrument of claim 1, said coarse stage having a resolution of one micrometer or better.

4. The instrument of claim 1, wherein the two stages are such that the instrument has a range of at least 500 micrometers in at least one direction when the sensing tip is used to sense said parameter of the sample.

5. The instrument of claim 1, wherein said sensing tip senses a height parameter that measures directly the height variation of a surface of the sample.

6. The instrument of claim 5, said probe including:

a stylus arm having a stylus tip; and

a capacitance gauge, a linear voltage differential transformer sensor, or a light intensity proximity sensor.

7. The instrument of claim 1, wherein said sensing tip senses thermal variations, electrostatic variations, magnetic variations of the sample, or the height variation of a surface of the sample.

8. The instrument of claim 1, wherein said sensing tip senses substantially simultaneously the height at one or more locations of a surface of the sample and at least another parameter of the sample at said one or more locations.

9. The instrument of claim 8, said sensing tip including a stylus tip that senses the height at one or more locations of a surface of the sample and a sensor element in the stylus tip or in the proximity of the stylus tip for sensing said at least another parameter.

10. The instrument of claim 1, wherein each of the two stages causes relative motion between the sensing tip and the sample in XYZ three dimensional space, the coarse stage comprising an XY portion for causing relative motion between the sensing tip and the sample in a direction substantially parallel to a surface of the sample and a Z portion for causing relative motion between the sensing tip and the sample in a direction substantially normal to the surface of the sample.

11. The instrument of claim 10, wherein the probe is connected to the fine stage, and the fine stage is connected to the Z portion of the coarse stage, and wherein the XY portion of the coarse stage is adapted for moving the sample.

12. The instrument of claim 11, wherein the fine stage comprises at least one piezoelectric tube, and wherein the probe is connected to the at least one piezoelectric tube.

13. The instrument of claim 11, wherein the fine stage comprises two piezoelectric tubes, said instrument further comprising a flexure hinge connecting the tubes to the sensor.

14. The instrument of claim 10, wherein the probe is connected to the Z portion of the coarse stage, and the fine stage is connected to the XY portion of the coarse stage, said fine stage being adapted for supporting and moving the sample.

15. The instrument of claim 14, wherein the fine stage comprises three piezoelectric tubes.

16. The instrument of claim 14, wherein the Z and XY portions of the coarse stage support and move the sensor and/or the sample relative to a fixed reference base.

17. The instrument of claim 10, wherein the fine stage comprises three piezoelectric tubes.

18. The instrument of claim 10, wherein the fine stage comprises piezoelectric stacks.

19. The instrument of claim 18, said fine stage further comprising a support frame, a moving frame and flexure hinges connecting the two frames, said piezoelectric stacks causing relative motion between the two frames.

20. The instrument of claim 1, wherein said probe comprises a stylus arm having a stylus tip for sensing a surface parameter of the sample, and a thermocouple embedded in the stylus tip for sensing thermal variations.

21. The instrument of claim 1, wherein said probe comprises:

an electrically conductive core;

a conductive shield surrounding the core for sensing electrostatic charge variations; and

an insulating layer separating the shield from the core.

22. The instrument of claim 21, wherein the sensing tip senses a surface parameter of the sample, said tip being part of the insulating layer or shield.

23. The instrument of claim 1, wherein said probe comprises a stylus arm having a stylus sensing tip for sensing a surface parameter of the sample.

24. The instrument of claim 23, said probe further comprising a flexure hinge connected to the arm, a force coil and means for passing current into the coil and a magnet, the force coil, or the magnet being connected to the arm, wherein electromagnetic interactions between the current in the coil and the magnet move the arm towards or away from the sample.

25. The instrument of claim 24, further comprising a first member supporting the flexure hinge, and a second member connected to the arm for supporting the force coil, wherein the two members, the flexure hinge, and the arm are formed from a single sheet of material to form a planar body.

26. The instrument of claim 25, said force coil comprising a layer of electrically conductive material on the planar body, said magnet being attached to the first member.

27. The instrument of claim 25, said tip being integral with or attached to said planar body at an end of the arm, said tip being substantially perpendicular to a plane of the planar body.

28. The instrument of claim 24, further comprising a capacitance gauge, a linear voltage differential transformer sensor, or a light intensity proximity sensor for measuring motion of the arm.

29. The instrument of claim 1, wherein said at least one controller controls the two stages so that both of the two stages substantially simultaneously cause relative motion between the sensor and the sample when the sensor is sensing said parameter of the sample.

30. The instrument of claim 1, wherein said probe comprise:

a stylus arm having a stylus tip for sensing a surface parameter of the sample;

a hinge supporting the stylus tip so that the stylus arm is rotatable about the hinge; and

means for applying a force to the stylus arm.

31. The instrument of claim 30, said force applying means comprising a force coil and means for passing current into the coil and a magnet, the force coil or the magnet being connected to the arm, wherein electromagnetic interactions between the current in the coil and the magnet cause the stylus arm to rotate about the hinge towards or away from the sample.

32. The instrument of claim 30, said force applying means comprising a capacitance means and means for applying a voltage to the capacitance means.

33. The instrument of claim 30, said stylus arm having a dynamic range of at least about 500 micrometers when rotated about the hinge.

34. The instrument of claim 30, said probe further comprising:

stylus displacement measuring means providing a position signal to indicate the position of the stylus tip; and

feedback means controlling the force applied by the force applying means in response to the position signal to cause the stylus tip to apply a desired force on the sample, said feedback operating independently of the two stages.

35. The instrument of claim 34, said feedback means causing the stylus tip to apply a constant force on the sample.

36. The instrument of claim 1, wherein said at least one controller controls the two stages so that the fine stage causes the sensing tip to scan in a direction substantially parallel to a surface of the sample when the sensing tip is sensing said parameter of the sample.

37. The instrument of claim 1, wherein said at least one controller controls the two stages so that the coarse stage causes the sensing tip to scan in a direction substantially parallel to a surface of the sample when the sensing tip is sensing said parameter of the sample.

38. The instrument of claim 1, said probe including a control circuit, said control circuit being distinct from and not part of the at least one controller.

39. The instrument of claim 38, said control circuit generating a feedback signal for controlling the sensing tip, wherein said feedback signal is not used for controlling the fine and coarse stages.

40. The instrument of claim 1, wherein said probe does not include any piezoelectric element.

41. A method for sensing a sample employing a sensing tip that does not transmit or emit light for sensing the sample, comprising the steps of:

causing relative motion between the sensing tip and the sample by means of a coarse stage to scan the sensing tip across a first surface of the sample;

causing relative motion between the sensing tip and the sample by means of a fine stage to scan the sensing tip across a second surface of the sample;

sensing a parameter of the sample when the sensing tip is moved by each of the two stages.

42. The method of claim 41, wherein said sensing step senses the parameter at a sensing rate that is independent of the speed of motion of the sensing tip by the two stages.

43. The method of claim 42, wherein the two stages cause relative motion between the sensing tip and the sample in steps at one or more frequencies, and wherein the sensing rate is independent of the one or more frequencies.

44. The method of claim 43, wherein the sensing rate is asynchronous with respect to the one or more frequencies.

45. The method of claim 41, wherein the two stages cause relative motion between the sensing tip and the sample sequentially.

46. The method of claim 41, wherein the two stages cause relative motion between the sensing tip and the sample substantially simultaneously.

47. The method of claim 46, wherein said sensing step senses the parameter when the coarse stage causes relative motion between the sensing tip and the sample in a direction and the fine stage does not cause relative motion between the sensing tip and the sample in said direction.

48. The method of claim 46, wherein said sensing step senses the parameter when the fine stage causes relative motion between the sensing tip and the sample in a first direction and the coarse stage does not cause relative motion between the sensing tip and the sample in said direction.

49. The method of claim 48, wherein the coarse stage causes relative motion between the sensing tip and the sample along a second direction substantially orthogonal to the first direction, so that resolution of the fine stage is retained in the first direction.

50. The method of claim 46, wherein the moving steps cause relative motion between the sensing tip and the sample in two orthogonal directions in steps at different rates.

51. The method of claim 46, said moving step by means of the fine stage causes relative motion between the sensing tip and the sample along a zigzag path so that the sensing tip oscillates relative to the sample about a line and at a frequency higher than that of the moving step by means of the coarse stage.

52. The method of claim 51, said moving step by means of the fine stage causes the sensing tip to oscillate about the line at a substantially constant amplitude, so that the zigzag path covers a substantially rectangular area.

53. The method of claim 46, wherein the sensing step senses the parameter when the coarse stage causes relative motion between the sensing tip and the sample in a first direction, and when the fine stage causes relative motion between the sensing tip and the sample in a second direction orthogonal to the first direction, so that resolution of the fine stage is retained in a direction orthogonal to the first direction.

54. The method of claim 41, wherein one of or both the moving steps cause relative motion between the sensing tip and the sample until the sensing tip is in a predetermined position relative to a surface of the sample, wherein said predetermined position is an initial imaging position, and then the moving steps cause relative motion between the sensing tip and the sample when the sensing tip is sensing said parameter in an initial direction substantially parallel to the surface of the sample to scan the surface.

55. The method of claim 54, wherein one of or both the moving steps cause relative motion between the sensing tip and the sample until the sensing tip is in contact with the surface of the sample, so that the predetermined position is one in contact with the surface of the sample.

56. The method of claim 54, wherein one of or both the moving steps cause the sensing tip to move in a plane containing the initial imaging position of the sensing tip and substantially parallel to the surface of the sample in a constant height mode.

57. The method of claim 54, wherein the sensing step senses a parameter of the sample, said parameter being a thermal variation, an electrostatic or magnetic parameter, or height variation of a surface of the sample.

58. The method of claim 54, said sensor including a stylus tip for contacting a surface of the sample, wherein said sensing step provides an output signal, said method further comprising applying a force on the stylus in response to said output signal so that the stylus tip exerts a substantially constant force on the surface of the sample in a constant force mode when the surface is scanned.

59. The method of claim 54, said sensor including a stylus tip, wherein one of or both the moving steps cause the stylus tip and the sample to move towards each other after the stylus tip and the sample are in contact, said sensing step measuring changes in position of the stylus tip to measure the compliance of the surface.

60. The method of claim 41, wherein the sensing step senses substantially simultaneously the height at one or more locations of a surface of the sample and another parameter of the sample at said one or more locations.

61. The method of claim 41, said sensing step being performed independently from the causing of relative motion by the coarse and fine stages.

62. The method of claim 41, said sensing step including providing a feedback signal to control the tip, wherein said feedback signal is not used for causing relative motion by the coarse and fine stages between the sensing tip and the sample.

63. An instrument for sensing a sample, comprising:

a probe having a sensing tip for sensing a first parameter of the sample;

a coarse stage causing relative motion between the sensing tip and the sample;

a fine stage causing relative motion between the sensing tip and the sample;

a sensor spaced apart from the tip for sensing a second optical parameter of the sample; and

at least one controller controlling the two stages and the sensor so that each of the coarse and fine stages causes the sensing tip to scan across the sample when the sensing tip is sensing said first parameter at a location of the sample and the sensor is sensing said second optical parameter of the sample substantially at said location.

64. The instrument of claim 63, wherein said second optical parameter is light reflectivity or light transmittance.

65. An instrument for sensing a sample, comprising:

a probe having a stylus arm with a sensing tip for sensing a parameter of the sample and a member supporting the stylus arm so that the stylus arm is rotatable about the member;

a coarse stage causing relative motion between the sensing tip and the sample;

a fine stage causing relative motion between the sensing tip and the sample; and

at least one controller controlling the two stages so that the coarse stage causes the sensing tip to scan across the surface of the sample when the sensing tip is sensing said parameter of the sample.

66. A method for sensing a sample employing a stylus arm with a sensing tip for sensing the samples comprising the steps of:

causing relative motion between the sensing tip and the sample by means of a coarse stage to scan the sensing tip across a first surface of the sample;

causing relative motion between the sensing tip and the sample by means of a fine stage to scan the sensing tip across a second surface of the sample, wherein the sensing tip is caused to rotate about a hinge during the relative motions;

sensing a parameter of the sample when the sensing tip is moved by each of the two stages.

67. An instrument for sensing a sample, comprising:

a probe having a sensing tip that does not emit or transmit light for sensing a parameter of the sample, said sensing tip having a dynamic range in a direction normal to a surface of the sample greater than that of a scanning probe microscope;

a coarse stage causing relative motion between the sensing tip and the sample;

a fine stage causing relative motion between the sensing tip and the sample; and

at least one controller controlling the two stages so that the coarse stage causes the sensing tip to scan across the surface of the sample when the sensing tip is sensing said parameter of the sample.

68. A method for sensing a sample employing a sensing tip for sensing the sample, comprising the steps of:

causing relative motion between the sensing tip and the sample by means of a coarse stage to scan the sensing tip across a surface of the sample;

causing relative motion between the sensing tip and the sample by means of a fine stage to scan the sensing tip across the surface of the sample;

sensing a parameter of the sample when the sensing tip is moved by each of the two stages, said sensing step having a dynamic range in a direction normal to the surface of the sample greater than that of a scanning probe microscope.

69. An instrument for sensing a sample, comprising:

a probe having a stylus arm which has a sensing tip for sensing a parameter of the sample;

a coarse stage causing relative motion between the sensing tip and the sample,

a fine stage causing relative motion between the sensing tip and the sample; and

at least one controller controlling the two stages so that the relative motion caused by either one or both of the two stages causes relative motion between the sensing tip and the sample when the sensing tip is sensing said parameter of the sample;

said probe further comprising a flexure hinge connected to the arm, a force coil and means for passing current into the coil and a magnet, the force coil, or the magnet being connected to the arm, wherein electromagnetic interactions between the current in the coil and the magnet move the arm towards or away from the sample;

said instrument further comprising a first member supporting the flexure hinge, and a second member connected to the arm for supporting the force coil, wherein the two members, the flexure hinge, and the arm are formed from a single sheet of material to form a planar body.

70. The instrument of claim 69, said force coil comprising a layer of electrically conductive material on the planar body, said magnet being attached to the first member.

71. The instrument of claim 69, said tip being integral with or attached to said planar body at an end of the arm, said tip being substantially perpendicular to a plane of the planar body.

72. A method for sensing a sample employing a sensing tip for sensing the sample, comprising the steps of:

causing relative motion between the sensing tip and the sample by means of a coarse stage to scan the sensing tip across a first surface of the sample;

causing relative motion between the sensing tip and the sample by means of a fine stage to scan the sensing tip across a second surface of the sample;

sensing a parameter of the sample when the sensing tip is moved by each of the two stages, wherein said sensing step senses the parameter at a sensing rate that is independent of the speed of motion of the sensing tip by the two stages.

73. The method of claim 72, wherein the two stages cause relative motion between the sensing tip and the sample in steps at one or more frequencies, and wherein the sensing rate is independent of the one or more frequencies.

74. The method of claim 73, wherein the sensing rate is asynchronous with respect to the one or more frequencies.

75. An instrument for sensing a sample employing a sensing tip for sensing the sample, comprising:

a coarse stage causing relative motion between the sensing tip and the sample to scan the sensing tip across a first surface of the sample;

a fine stage causing relative motion between the sensing tip and the sample to scan the sensing tip across a second surface of the sample;

at least one controller controlling the two stages so that when the sensing tip is moved by each of the two stages, said sensing tip senses the parameter at a sensing rate that is independent of the speed of motion of the sensing tip by the two stages.