High speed lithography machine and method

• US 20050264777A1
• Filed: 05/28/2004
• Published: 12/01/2005
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: Onto Innovation Inc.
• Original Assignee: Azores Corporation (Onto Innovation Inc.)
• Inventors: Resor, Griffith L. III, da Silveira, Elvino M., Gardner, Steven D.
• Granted Patent: US 7,385,671 B2
• Time in Patent Office: Days
• US Class Current: 355/53
• CPC Class Codes: G03F 7/70275 Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
• CPC Class Codes: G03F 7/70733 Handling masks and workpieces, e.g. exchange of workpiece or mask, transport of workpiece or mask
• CPC Class Codes: G03F 9/7003 Alignment type or strategy, e.g. leveling, global alignment

Abstract

A machine and method for high speed production of circuit patterns on silicon wafers or similar substrates may be used for applications including printing Integrated Circuit (IC) packaging patterns onto wafers prior to separating IC chips. Projection camera(s) simultaneously project image(s) onto substrate(s) carried on an X, Y, θ stage. The projection camera(s) may include independent alignment systems, light sources, and control of focus, image placement, image size, and dose. In one embodiment, each camera inlcudes a 6-axis reticle chuck that moves a reticle to correct image-to-substrate overlay errors. In-stage metrology sensors and machine software establish and maintain the correct relationship among the machine'"'"'s coordinate systems. Thus, two or more projection cameras can print simultaneously even when substrates are slightly misplaced on the X, Y, θ stage.

Claims

1. A lithography machine, comprising:

at least two projection cameras positioned to project images from respective image sources onto a first substrate and a second substrate simultaneously, each projection camera including an independent, multi-axis, alignment system that aligns the respective image with the respective substrate; and

a stage adapted to carry the first and second substrates and to move relative to the projection cameras.

2. The lithography machine according to claim 1 further including a controller that coordinates motion of the images and stage, free from moving the first or second substrate with respect to the stage, to align and overlay the projected images on the first and second substrates from the respective projection cameras.

3. The lithography machine according to claim 2 wherein the controller causes the multi-axis alignment system to compensate for alignment differences between the first and second substrates on the stage.

4. The lithography machine according to claim 1 wherein the alignment system includes an independent, multi-axis alignment mechanism that moves the respective image independently relative to the respective substrate to correct for an alignment error between the respective image source and the respective substrate.

5. The lithography machine according to claim 1 wherein each multi-axis alignment system includes an independent focus mechanism that focuses the image projected by the respective projection camera.

6. The lithography machine according to claim 1 wherein the multi-axis alignment systems move the image sources in six axes.

7. The lithography machine according to claim 1 wherein the multi-axis alignment systems move the image sources in at least two axes to correct for at least one of the following errors:

X, Y, θ

, image size, or keystone errors.

8. The lithography machine according to claim 7 wherein each multi-axis alignment mechanism includes a position sensor subsystem in each axis of motion.

9. The lithography machine according to claim 7 wherein each multi-axis alignment system is calibrated prior to being used to project an image onto the respective substrate.

10. The lithography machine according to claim 7 wherein each multi-axis alignment system includes a travel range sufficient to move the projected image at least about +/−

1.25 mm on the respective substrate in an X- or Y-axis.

11. The lithography machine according to claim 1 wherein the multi-axis alignment systems include an alignment sensor used to determine a position of a substrate on the stage.

12. The lithography machine according to claim 11 wherein the alignment sensor is an alignment microscope.

13. The lithography machine according to claim 1 wherein the multi-axis alignment systems include at least one stage metrology package located on the stage in a position observable by the alignment systems.

14. The lithography machine according to claim 13 wherein the alignment systems are adapted to determine alignment between the respective projection cameras and the stage through observation of the at least one stage metrology package.

15. The lithography machine according to claim 13 wherein the at least one stage metrology package includes multiple patterns observable by the multi-axis alignment systems.

16. The lithography machine according to claim 13 wherein the at least one stage metrology package is shared by the multi-axis alignment systems.

17. The lithography machine according to claim 1 wherein the image sources include a mask.

18. The lithography machine according to claim 1 wherein the image sources include mechanisms that dynamically generate a mask.

19. The lithography machine according to claim 1 wherein each projection camera further includes a shutter controlled by a dose control system to expose the respective substrate to the projected image for a controlled amount of time.

20. The lithography machine according to claim 19 wherein the stage remains stationary until the shutters close.

21. The lithography machine according to claim 1 wherein the multi-axis alignment systems include (a) an auto-focus detector, (b) a multi-axis reticle chuck that holds a reticle that includes the image source, and (c) an alignment microscope and camera coupled to image processing software, wherein:

(i) the multi-axis alignment systems include a focus control mechanism that moves the respective projection camera in an axis to correct for a focus error as determined by the autofocus detector and (ii) the multi-axis alignment systems include mechanisms that move the multi-axis reticle chuck in multiple axes to correct for alignment errors as determined by the image processing software through comparison of current alignment images taken by the alignment microscope and previously determined calibration data associated with the multi-axis reticle chuck.

22. The lithography machine according to claim 1 wherein the multi-axis alignment systems include voice coils and flexures.

23. The lithography machine according to claim 1 wherein the multi-axis alignment systems include ceramic actuators.

24. The lithography machine according to claim 1 wherein the stage includes multiple surfaces supporting stage position measurements.

25. The lithography machine according to claim 24 wherein the multiple surfaces are mirrors that reflect optical beams.

26. The lithography machine according to claim 25 wherein the optical beams include at least one first optical beam along a first axis and at least two second optical beams along a second axis.

27. The lithography machine according to claim 26 wherein the two second optical beams are approximately spaced apart at least the same distance as the projection cameras.

28. The lithography machine according to claim 1 wherein the stage is driven by multiple motors, wherein at least two motors are driven differentially.

29. A method for printing onto substrates, the method comprising:

positioning a first substrate and a second substrate in a projection region of at least two projection cameras adapted to project respective images from image sources onto respective substrates;

moving the images independently relative to the respective substrates to correct for alignment errors between the image sources and the respective substrates;

carrying the first and second substrates on a stage; and

moving the stage relative to the projection cameras.

30. The method according to claim 29 further including causing motion of the images and stage, free from moving the first or second substrate with respect to the stages, to align and overlay the projected images on the substrates from the respective projection cameras.

31. The method according to claim 30 wherein moving the images independently includes compensating for alignment differences between the first and second substrates on the stage.

32. The method according to claim 29 wherein aligning the images with the respective substrates includes moving the images independently relative to the respective substrates to correct for alignment errors between the image sources and the respective substrates.

33. The method according to claim 29 wherein aligning the images includes independently focusing the projection cameras.

34. The method according to claim 29 wherein aligning the images includes adjusting the image sources in six axes.

35. The method according to claim 29 wherein aligning the images includes adjusting the image sources in at least two axes to correct for at least one of the following errors:

X, Y, θ

, image size, or keystone errors.

36. The method according to claim 35 wherein aligning the images includes sensing a position in each axis of motion.

37. The method according to claim 35 further including calibrating each of the projection cameras in multiple axes prior to projecting the images onto the first and second substrates.

38. The method according to claim 35 further including causing the projected images to travel in a range at least about +/−

1.25 mm in an X-axis or Y-axis on respective first and second substrates.

39. The method according to claim 29 wherein aligning the images includes sensing positions of the substrates on the stage.

40. The method according to claim 39 wherein sensing positions of the substrates on the stage includes viewing the substrates with independent alignment microscopes.

41. The method according to claim 29 wherein aligning the images includes observing at least one stage metrology package located on the stage.

42. The method according to claim 41 wherein aligning the images includes determining alignment between the respective projection cameras and the stage through observing multiple patterns on the stage metrology package.

43. The method according to claim 29 further including masking the image sources.

44. The method according to claim 29 further including dynamically generating a mask associated with the image sources.

45. The method according to claim 29 further including controlling an amount of time the first and second substrates are exposed to the respective images.

46. The method according to claim 45 wherein positioning the first and second substrates beneath the at least two projection cameras includes maintaining the position of the first and second substrates until exposure to the respective images is completed.

47. The method according to claim 29 wherein moving the images includes correcting focus error at each of the projection cameras independently and correcting for alignment errors based on a comparison of current alignment images compared to previously determined calibration data.

48. The method according to claim 29 wherein moving the images includes controlling the position of the image sources in a frictionless manner.

49. The method according to claim 29 further including:

measuring the position of the stage supporting the substrates; and

aligning the images to the substrates as a function of the measurements.

50. The method according to claim 49 wherein the measuring includes optically measuring the position of multiple surfaces of the stage.

51. The method according to claim 50 wherein optically measuring the position of multiple surfaces of the stage includes measuring phase characteristics of at least one first optical beam along a first axis and phase characteristics of at least two second optical beams along a second axis.

52. The method according to claim 51 wherein the two second optical beams are approximately spaced apart at least the same distance as the substrates.

53. The method according to claim 29 further including differentially driving multiple motors in the stage.

54. A lithography machine, comprising:

means for projecting images onto at least two substrates simultaneously;

means for correcting alignment errors between each projection means and respective ones of the at least two substrates in a manner substantially free from moving the at least two substrates.

means for carrying the at least two substrates; and

means for moving the at least two substrates relative to the projection means.

55. A lithography machine, comprising:

a projection camera including a reticle chuck adapted to hold a reticle having a pattern to be projected as an image onto a substrate;

a multi-axis alignment system that moves the image in multiple directions;

a stage adapted to carry the substrate and move the substrate relative to the projection camera;

an alignment sensor system adapted to measure a position of the substrate relative to the stage for use in projecting the image onto the substrate; and

an alignment controller coupled to the stage, alignment sensor system, and multi-axis alignment system that causes the stage to position the substrate in a projection region of the camera for gross alignment and causes the multi-axis alignment system to align the image relative to the substrate for fine alignment each time the stage moves in the projection region.

56. The lithography machine according to claim 55 wherein the alignment sensor system is adapted to measure a position of the stage relative to the projection camera.

57. The lithography machine according to claim 55 wherein the alignment sensor system measures the position of the substrate in a projection region of the projection camera.

58. The lithography machine according to claim 55 wherein the alignment controller causes the multi-axis alignment system to align the image relative to the substrate in an open-loop manner.

59. The lithography system according to claim 55 wherein the alignment controller causes the multi-axis alignment system to align the image relative to the substrate in a closed-loop manner.

60. The lithography machine according to claim 55 wherein the alignment sensor system captures images of patterns on the substrate for processing by the alignment controller.

61. The lithography machine according to claim 55 wherein the multi-axis alignment system causes the reticle chuck to move the reticle in at least two axes of motion.

62. The lithography machine according to claim 55 wherein the projection camera is coupled to a focus control system that moves the projection camera in a manner that focuses the projected image on the substrate.

63. The lithography machine according to claim 55 wherein the projection camera includes a shutter coupled to a dose control system that controls exposure time of the substrate to the projected image.

64. The lithography machine according to claim 55 further including (i) another projection camera with a respective reticle chuck supporting a respective reticle that projects an image onto another substrate simultaneously with the other projection camera projecting a respective image onto its respective substrate, (ii) another alignment sensor system that senses a position of the respective substrate, and (iii) another alignment controller that aligns the respective reticle with the respective substrate independently.

65. A method for printing on a substrate, the method comprising:

providing a reticle having a pattern to be projected as an image onto a substrate in optical exposure relation with a projection camera;

moving the substrate into gross alignment with the reticle as imaged in a projection region of the projection camera;

determining a position of the substrate relative to the stage for use in projecting the image onto the substrate; and

moving the image in multiple axes to align the image in fine alignment with the substrate each time the substrate is moved in the projection region; and

projecting the pattern onto the substrate.

66. The method according to claim 65 wherein determining an alignment error between the reticle and the substrate includes measuring a position of a stage carrying the substrate relative to the projection camera.

67. The method according to claim 65 wherein determining an alignment error between the reticle and the substrate includes measuring the position of the substrate in a projection region of the projection camera.

68. The method according to claim 65 wherein moving the image is done in an open-loop manner.

69. The method according to claim 65 wherein moving the image is done in a closed-loop manner.

70. The method according to claim 65 further including capturing images of patterns on a stage moving the substrate and processing the images to determine an alignment error between the reticle and the substrate.

71. The method according to claim 65 wherein aligning the image relative to the substrate includes moving the reticle in at least two axes of motion.

72. The method according to claim 65 further including focusing the projected image.

73. The method according to claim 65 further including controlling an exposure time of the substrate to the projected image.

74. The method according to claim 65 further including independently and simultaneously aligning multiple images, produced by multiple reticles, with multiple substrates to expose the multiple substrates to respective images simultaneously.

75. A lithography machine, comprising:

means for moving a substrate into gross alignment with a reticle as imaged in a projection region of the projection camera, the reticle including a pattern to be projected as an image onto the substrate;

means for sensing a position of the substrate relative to the stage for use in projecting the image onto the substrate; and

means for fine aligning the image with the substrate each time the substrate is moved in the projection region; and

means for projecting the pattern onto the substrate.

76. A lithography machine, comprising:

first and second projection cameras that project images onto first and second substrates, respectively, the projection cameras including respective alignment systems;

first and second alignment microscopes that detect alignment patterns associated with the respective substrates; and

at least one alignment compensation controller coupled to outputs of the first and second alignment microscopes that cause the alignment systems to move the images relative to the substrates based on the detected alignment patterns received from the alignment microscopes.

77. The lithography machine according to claim 76 wherein the alignment systems determine a location of a stage carrying the substrates relative to the projection cameras through a lens of the respective projection cameras.

78. The lithography machine according to claim 76 wherein the alignment systems determine a location of a stage carrying the substrates off-axis from the projection cameras and observe a metrology package associated with the stage to determine the location of the stage relative to the projection cameras.

79. The lithography machine according to claim 76 wherein the first and second alignment microscopes operate independently.

80. The lithography machine according to claim 76 further including first and second auto-focus sensors mechanically coupled to respective alignment microscopes that provide signals to the at least one alignment compensation controller to cause the respective alignment microscope to remove focus error associated with the alignment patterns.

81. The lithography machine according to claim 76 wherein the first and second alignment microscopes provide images to the at least one alignment compensation controller causing respective projection cameras to remove respective focus errors associated with the images on the substrates.

82. A method for printing onto substrates, the method comprising:

projecting first and second images onto first and second substrates, respectively;

detecting first and second alignment patterns associated with the respective first and second substrates; and

causing the first and second images to move relative to the first and second substrates based on the detected alignment patterns.

83. The method according to claim 82 wherein projecting the first and second images onto the first and second substrates includes determining a location of a stage carrying the substrates through a lens of projection cameras projecting the images.

84. The method according to claim 82 wherein projecting the first and second images onto the first and second substrates includes determining locations of a stage carrying the substrates off-axis from projection cameras projecting the images and observing a metrology package associated with the stage to determine the position of the stage relative to the projection cameras.

85. The method according to claim 82 wherein detecting first and second alignment patterns occur independently.

86. The method according to claim 82 further including, based on the detected alignment patterns, independently removing focus errors associated with detecting the first and second alignment patterns.

87. The method according to claim 82 further including, based on the detected first and second alignment patterns, removing respective focus errors associated with the first and second images on the first and second substrates.

88. A lithography machine, comprising:

means for aligning and projecting images onto at least two substrates simultaneously;

means for detecting alignment patterns associated with each of the at least two substrates; and

means for moving the projected images relative to the substrates based on the detected alignment patterns.