Spot grid array imaging system

• US 20040061042A1
• Filed: 08/06/2003
• Published: 04/01/2004
• Est. Priority Date: 11/07/2001
• Status: Abandoned Application

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Almogy, Gilad, Reches, Oren
• Application Number:
  US10/634,793
• Publication Number:
  US 20040061042A1
• Time in Patent Office: Days
• US Class Current: 250/208.1
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

A high data-rate spot-grid array imaging system includes a periodic array of lenses, each lens imaging a spot in an object plane, such as a semiconductor substrate to be inspected, upon an image plane to image a periodic array of spots. A sensor is provided in a conjugate image plane with a periodic array of readout elements, each collecting the signal from one of the spots. A mechanical system moves the substrate in a direction which is nearly parallel to an axis of the arrary of spots such that as the substrate is moved across the spot array in the scan direction (the y-direction) the spots traces a path which leaves no gaps in the mechanical cross-scan direction (the x-direction). A compensator, such as a servo or a movable mirror, compensates for mechanical inaccuracies in the moving stage, thereby increasing imaging accuracy.

Claims

1. An imager comprising:

a radiation source for simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

a detector array for collecting signals resulting from an interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface;

a movable stage for supporting the object and moving the object such that a predetermined portion of the surface of the object can be irradiated and imaged; and

a compensator for compensating for mechanical inaccuracies in the movable stage.

2. The imager of claim 1, wherein the radiation source comprises:

a light source; and

an array of lenses for focusing light from the light source into the array of spots on the surface of the object.

3. The imager of claim 2, wherein the lenses are micro-lenses.

4. The imager of claim 3, wherein the micro-lenses are diffractive or refractive.

5. The imager of claim 3, wherein the light source is a laser, and the imager comprises illumination optics for collimating and directing laser light from the light source through the micro-lens array to impinge on the object surface.

6. The imager of claim 5, wherein the illumination optics comprises a beam splitter to direct the collimated laser light to the micro-lens array, wherein the beam splitter is for allowing the light reflected from the spots to pass through to the detector array.

7. The imager of claim 5, wherein the illumination optics comprises a polarizing beam splitter to direct the collimated laser light to the micro-lens array, and a quarter-wave plate between the beam splitter and the micro-lens array for polarizing the laser light, wherein the beam splitter and the quarter-wave plate are for allowing the light reflected from the spots to pass through to the detector array.

8. The imager of claim 2, wherein the light reflected from the spots forms an intermediate image having a size substantially equal to the size of the lens array, the imager comprising a telescope between the lens array and the detector array for demagnifying the intermediate image.

9. The imager of claim 2, further comprising a relay optical system between the lens array and the object for demagnifying the array of spots.

10. The imager of claim 1, wherein the movable stage is for moving the object substantially linearly in a scanning direction that deviates from an axis of the spot array such that as the object is moved a distance substantially equal to a length of the spot array in the scanning direction, the spots trace a substantially continuous path on the object surface in a mechanical cross-scan direction.

11. The imager of claim 1, wherein the detector array comprises a CCD.

12. The imager of claim 2, wherein the light source is for supplying light in the extreme ultraviolet range.

13. The imager of claim 2, wherein the detector array is for detecting photo-electron emissions.

14. The imager of claim 2, wherein the lens array is two-dimensional, and the detector array is two-dimensional and corresponds to the lens array.

15. The imager of claim 2, wherein the light source is a continuous light source.

16. The imager of claim 2, wherein the light source is a pulsed light source.

17. The imager of claim 1, wherein the compensator comprises a servo for moving the spot array to compensate for the mechanical inaccuracies.

18. The imager of claim 2, wherein the compensator is selected from the group consisting of a movable mirror, an electro-optic element and an acousto-optic element for varying an angle of incidence of the light source onto the surface of the object for compensating for the mechanical inacurracies in the movable stage.

19. The imager of claim 8, wherein the telescope is a confocal telescope.

20. The imager of claim 2, further comprising a fluid having a substantially optimized refractive index disposed in and filling a gap between the lens array and the object.

21. The imager of claim 3, further comprising a member having an array of pin-holes corresponding to the lenses of the micro-lens array, the member being disposed in a conjugate image plane between the object and the detector array such that the pinholes are concentric with the spots of the spot array.

22. The imager of claim 21, further comprising a second array of micro-lenses for generating the conjugate image plane.

23. The imager of claim 3, further comprising:

a beam splitter disposed between the micro-lens array and the detector array to split a conjugate plane of a back pupil of the micro-lens array into a plurality of conjugate pupil planes;

focusing optics associated with each conjugate pupil plane for forming a conjugate image plane for each pupil plane;

a plurality of members, each member having a pin-hole array and associated with one of the image planes, each member disposed such that it has a different lateral shift; and

a plurality of detector arrays, each detector array associated with one of the members for receiving light from the pin hole array, wherein the detector arrays are for simultaneously generating a plurality of images of the object.

24. The imager of claim 10, wherein the movable stage is for moving the object such that the spots overlap as they trace the continuous path on the object surface.

25. The imager of claim 24, wherein the movable stage is for moving the object such that the spots are interleaved as they trace the continuous path on the object surface.

26. The imager of claim 24, wherein the spot array comprises a plurality of rows and columns of spots, and the radiation source is for irradiating a predetermined number of rows of spots such that the spots of two adjacent ones of the columns overlap as they trace the continuous path on the object surface.

27. The imager of claim 1, wherein the radiation source comprises an array of lasers directed at the object surface to form the spot array.

28. The imager of claim 27, further comprising a beam splitter for directing reflected light from the object to the detector array.

29. The imager of claim 2, wherein a first portion of the light from the light source is reflected from the array of spots at a first angle to the detector array, and a second portion of the light from the light source is reflected at a second angle different from the first angle, the imager further comprising a second detector array for collecting signals corresponding to the second portion of the light.

30. The imager of claim 29, comprising a second lens array between the spot array and the second detector.

31. The imager of claim 29, wherein the lens array comprises diffractive elements to divert the second portion of the light to the second detector array.

32. The imager of claim 2, wherein the lens array comprises rows and columns of lenses corresponding to the spot array, and the movable stage is for moving the object from a first position to a second position such that the spots on the object surface irradiated by the lens array at the second position overlap the spots on the object surface irradiated at the first position.

33. The imager of claim 2, wherein each lens of the lens array comprises a plurality of lenses in series.

34. The imager of claim 23, further comprising an image processor for processing the simultaneously generated images of the object to compensate for imperfect focussing.

35. The imager of claim 3, further comprising a member having an array of masks corresponding to the centers of the lenses of the micro-lens array, the member being disposed in a conjugate image plane between the object and the detector array such that the masks are concentric with the spots of the spot array.

36. The imager of claim 1, wherein the radiation source is for irradiating a first path between the radiation source and the surface of the object, and the detector array is for collecting the signals from the surface of the object along a second path different from the first path.

37. The imager of claim 36, wherein the radiation source comprises:

a light source; and

an array of lenses for focusing light from the light source into the array of spots on the surface of the object.

80. The imager of claim 10, wherein the movable stage is for moving the object from a first position to a second position in the scanning direction such that the spots on the object surface at the second position are offset from an axis of the scanning direction and from the mechanical cross-scan direction relative to the first position.

38. An imager comprising:

an illumination source comprising a broadband lamp, for simultaneously illuminating an array of spots spaced apart from each other on a surface of an object to be imaged;

a detector array for collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the illuminated portions of the object surface, the detector array comprising a plurality of pixel arrays, each pixel array corresponding to one of the spots; and

a movable stage for supporting the object and moving the object such that a predetermined portion of the surface of the object can be illuminated and imaged;

wherein the illumination source is for illuminating the array of spots such that the signal from each spot is collected by more than one pixel of one of the pixel arrays at a time.

39. The imager of claim 38, wherein a portion of the surface of the object is imaged by a corresponding portion of one of the pixel arrays by a plurality of portions of one of the spots as the stage moves the object.

40. The imager of claim 38, wherein the pixels of the pixel arrays are sized to provide a predetermined resolution, and

wherein the illumination source is for illuminating the array of spots such that each spot is larger than a predetermined diffraction limit of the imager.

41. The imager of claim 38, wherein the detector array comprises a CCD.

42. An imager comprising:

a radiation source for simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

a detector array for collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface; and

a movable stage for supporting the object and moving the object such that a predetermined portion of the surface of the object can be irradiated and imaged;

wherein the movable stage is for moving the object substantially linearly in a scanning direction that deviates from an axis of the spot array such that as the object is moved a distance substantially equal to a length of the spot array in the scanning direction, the spots trace a substantially continuous path on the object surface in a mechanical cross-scan direction; and

wherein the spot array comprises a plurality of rows and columns of spots, and the radiation source is for irradiating a predetermined number of rows of spots such that the spots of two adjacent ones of the columns overlap as they trace the substantially continuous path on the object surface.

43. The imager of claim 42, wherein the radiation source is for irradiating additional rows of spots, such that a total number of rows of spots is greater than the predetermined number of rows of spots, and the two adjacent ones of the columns overlap.

44. The imager of claim 43, wherein the radiation source is for irradiating a sufficient number of the additional rows of spots such that neighboring pixels used for an image processing algorithm are all from one of the columns.

45. The imager of claim 42, further comprising a compensator for compensating for mechanical inaccuracies in the movable stage.

46. An inspection system comprising:

a radiation source for simultaneously irradiating a first array of spots spaced apart from each other on a surface of a first object to be imaged and irradiating a second array of spots spaced apart from each other on a surface of a second object to be imaged, wherein the first and second spot arrays are substantially identical, and the surfaces of the first and second objects correspond to each other;

a first detector array for collecting signals resulting from the interaction of the spots with the surface of the first object to form an image of the irradiated portions of the first object surface;

a second detector array for collecting signals resulting from the interaction of the spots with the surface of the second object to form an image of the irradiated portions of the second object surface;

a movable stage for supporting the first and second objects and moving the objects such that substantially the entire surface of each object can be irradiated and imaged; and

a processor for comparing the images of the first and second objects.

47. The inspection system of claim 46, wherein the processor is configured to determine whether a defect exists in the surface of the second object based on the comparison of the images of the first and second objects.

48. The inspection system of claim 47, wherein the processor is configured to determine that a defect exists in the surface of the second object when a value of a parameter of the image of the second object surface differs from a value of the parameter of the image of the first object surface by more than a predetermined threshold amount.

49. The imager of claim 46, further comprising a compensator for compensating for mechanical inaccuracies in the movable stage.

50. A method comprising the steps of:

simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface;

moving the object on a movable stage while the irradiating and collecting steps are being performed, such that a predetermined portion of the surface of the object can be irradiated and imaged; and

compensating for mechanical inaccuracies in the movable stage.

51. The method of claim 50, comprising providing an array of lenses for focusing light from a light source into the array of spots on the surface of the object.

52. The method of claim 51, wherein the light reflected from the spots forms an intermediate image having a size substantially equal to the size of the lens array, further comprising demagnifying the intermediate image.

53. The method of claim 50, comprising moving the object substantially linearly in a scanning direction that deviates from an axis of the spot array such that as the object is moved a distance substantially equal to a length of the spot array in the scanning direction, the spots trace a substantially continuous path on the object surface in a mechanical cross-scan direction.

54. The method of claim 51, comprising irradiating the spot array using light in the extreme ultraviolet range.

55. The method of claim 51, comprising collecting photoelectron emissions.

56. The method of claim 51, comprising providing a fluid having a substantially optimized refractive index disposed in and filling a gap between the lens array and the object.

57. The method of claim 53, comprising moving the object such that the spots overlap as the trace the continuous path on the object surface.

58. The method of claim 57, comprising moving the object such that the spots are interleaved as they trace the continuous path on the object surface.

59. The method of claim 57, wherein the spot array comprises a plurality of rows and columns of spots, comprising irradiating a predetermined number of rows of spots such that the spots of two adjacent ones of the columns overlap as they trace the continuous path on the object surface.

60. The method of claim 51, further comprising:

reflecting a first portion of the light from the light source from the array of spots at a first angle to a first detector array for collecting signals corresponding to the first portion of the light; and

reflecting a second portion of the light from the light source at a second angle different from the first angle to a second detector array for collecting signals corresponding to the second portion of the light.

61. A method comprising the steps of:

simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface;

focusing light from a light source into the array of spots on the surface of the object using an array of lenses;

placing a member having an array of pin-holes corresponding to the lenses of the array in a conjugate image plane between the object and the detector array such that the pinholes are concentric with the spots of the spot array; and

moving the object on a movable stage such that a predetermined portion of the surface of the object can be irradiated and imaged.

62. The method of claim 61, comprising providing a second array of lenses for generating the conjugate image plane.

63. A method comprising the steps of:

simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

focusing light from a light source into the array of spots on the surface of the object using an array of lenses;

collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface at a detector array;

splitting a conjugate plane of a back pupil of the lens array into a plurality of conjugate pupil planes;

forming a conjugate image plane for each pupil plane;

placing a plurality of members, each member having a pin-hole array and associated with one of the image planes, such that each member has a different lateral shift;

collecting signals resulting from the interaction of the spots with the surface of the object to simultaneously generate a plurality of images of the irradiated portions of the object, each image associated with one of the members for receiving light from the pin hole array;

moving the object on a movable stage such that a predetermined portion of the surface of the object can be irradiated and imaged; and

compensating for mechanical inaccuracies in the moving stage.

64. A method comprising the steps of:

simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface;

focusing light from a light source into the array of spots on the surface of the object using an array of lenses;

placing a member having an array of masks corresponding to the centers of the lenses of the array in a conjugate image plane between the object and the detector array such that the masks are concentric with the spots of the spot array; and

moving the object on a movable stage such that a predetermined portion of the surface of the object can be irradiated and imaged.

65. A method comprising:

simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface; and

supporting the object and moving the object substantially linearly in a scanning direction that deviates from an axis of the spot array such that as the object is moved a distance substantially equal to a length of the spot array in the scanning direction, the spots trace a substantially continuous path on the object surface in a mechanical cross-scan direction, and a predetermined portion of the surface of the object is irradiated and imaged;

wherein the spot array comprises a plurality of rows and columns of spots, and the irradiating step comprises irradiating a predetermined number of rows of spots such that the spots of two adjacent ones of the columns overlap as they trace the continuous path on the object surface.

66. The method of claim 65, wherein the plurality of rows and columns of spots corresponds to an area of a portion of the surface of the object, the method comprising irradiating additional rows of spots, such that a total number of rows of spots is greater than the predetermined number of rows of spots, and the two adjacent ones of the columns overlap.

67. A method comprising:

simultaneously irradiating a first array of spots spaced apart from each other on a surface of a first object to be imaged and irradiating a second array of spots spaced apart from each other on a surface of a second object to be imaged, wherein the first and second spot arrays are substantially identical, and the surfaces of the first and second objects correspond to each other;

collecting signals resulting from the interaction of the spots with the surface of the first object to form an image of the irradiated portions of the first object surface;

collecting signals resulting from the interaction of the spots with the surface of the second object to form an image of the irradiated portions of the second object surface;

moving the first and second objects on a movable stage such that a predetermined portion of the surface of each object can be irradiated and imaged; and

comparing the images of the first and second objects.

68. The method of claim 67, comprising determining whether a defect exists in the surface of the second object based on the comparison of the images of the first and second objects.

69. The method of claim 68, comprising determining that a defect exists in the surface of the second object when a value of a parameter of the image of the second object surface differs from a value of the parameter of the image of the first object surface by more than a predetermined threshold amount.

70. The method of claim 67, wherein the first and second objects are subject to substantially identical mechanical vibrations during the moving step.

71. The method of claim 67, comprising compensating for mechanical inaccuracies in the moving stage.

72. The method of claim 67, wherein the irradiating step comprises focusing light from a light source to form the first and second spot arrays.

73. The method of claim 67, wherein the irradiating step comprises directing laser light to impinge on the first and second surfaces to form the first and second spot arrays.

74. A method comprising the steps of:

simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

collecting signals resulting from the interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface; and

moving the object on a movable stage substantially linearly in a scanning direction that deviates from an axis of the spot array such that as the object is moved a distance substantially equal to a length of the spot array in the scanning direction, the spots trace a substantially continuous path on the object surface in a mechanical cross-scan direction while the irradiating and collecting steps are being performed, such that a predetermined portion of the surface of the object can be irradiated and imaged;

wherein the spot array comprises a plurality of rows and columns of spots, and the irradiating step comprises irradiating a predetermined number of rows of spots such that the spots of two adjacent ones of the columns overlap as they trace the continuous path on the object surface.

75. A method comprising the steps of:

simultaneously focusing light from a light source into an array of spots spaced apart from each other on a surface of an object to be imaged;

reflecting a first portion of the light from the light source from the array of spots at a first angle to a first detector array for collecting signals resulting from the interaction of the spots with the surface of the object to form a first image of the irradiated portions of the object surface; and

reflecting a second portion of the light from the light source at a second angle different from the first angle to a second detector array for collecting signals resulting from the interaction of the spots with the surface of the object to form a second image of the irradiated portions of the object surface; and

moving the object on a movable stage while the irradiating and collecting steps are being performed, such that a predetermined portion of the surface of the object can be irradiated and imaged.

76. An imager comprising:

a radiation source for simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

a detector array for collecting signals resulting from an interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface;

a movable stage for supporting the object and moving the object such that a predetermined portion of the surface of the object can be irradiated and imaged;

a first member having an array of pin-holes corresponding to the centers of the spots of the array, the first member being disposed between the object and the detector array such that the pinholes are concentric with the spots; and

a second member having an array of masks corresponding to the centers of the spots of the array, the second member being disposed between the radiation source and the surface of the object such that the masks are concentric with the spots of the spot array.

77. An imager comprising:

a radiation source for simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

a detector array for collecting signals resulting from an interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface;

a movable stage for supporting the object and moving the object such that a predetermined portion of the surface of the object can be irradiated and imaged; and

a first member having an array of masks corresponding to the centers of the spots of the array, the first member being disposed between the object and the detector array such that the pinholes are concentric with the spots.

78. The imager of claim 77, further comprising a second member having an array of pin-holes corresponding to the centers of the spots of the array, the second member being disposed between the radiation source and the surface of the object such that the masks are concentric with the spots of the spot array.

79. An imager comprising:

a light source for simultaneously irradiating an array of spots spaced apart from each other on a surface of an object to be imaged;

an array of lenses for focusing light from the light source into the array of spots;

a first detector array for collecting signals resulting from an interaction of the spots with the surface of the object to form an image of the irradiated portions of the object surface, wherein a first portion of the light from the light source is reflected from the array of spots at a first angle to the first detector array, and a second portion of the light from the light source is reflected at a second angle different from the first angle

a second detector array for collecting signals corresponding to the second portion of the light; and

a movable stage for supporting the object and moving the object such that a predetermined portion of the surface of the object can be irradiated and imaged.