Multiple degree of freedom substrate manipulator

• US 20030156270A1
• Filed: 02/15/2002
• Published: 08/21/2003
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: Active Precision Incorporated
• Original Assignee: Active Precision Incorporated
• Inventors: Hunter, Bradley L.
• Granted Patent: US 6,756,751 B2
• Time in Patent Office: Days
• US Class Current: 355/72
• CPC Class Codes: G03F 7/707 Chucks, e.g. chucking or un-chucking operations or structural details
• CPC Class Codes: G03F 7/70758 Drive means, e.g. actuators, motors for long- or short-stroke modules or fine or coarse driving
• CPC Class Codes: G03F 7/70858 Environment aspects, e.g. pressure of beam-path gas, temperature pollution aspects G03F7/70916
• CPC Class Codes: Y10T 74/20341 Power elements as controlling elements
• CPC Class Codes: Y10T 74/20348 Planar surface with orthogonal movement and rotation

Abstract

A system for manipulating a planar substrate such as a semiconductor wafer is provided. The manipulator is typically used in conjunction with an XY stage to focus and planarize a wafer with respect to a tool. The manipulator employs redundant actuators of different types and a control system that uses low-bandwidth, high efficiency actuators to provide low frequency forces and high-bandwidth, but less efficient, actuators to provide all other forces. The manipulator provides support and manipulation of a substrate while minimizing errors due to thermal distortion.

Claims

1. An apparatus for manipulation of a planar substrate, comprising:

a housing movable on an X-Y stage that transports the housing in at least two orthogonal directions;

a surface handler disposed within the housing and having a substantially flat surface;

a plurality of position sensors disposed about at least one of a periphery of the surface handler and a periphery of the housing;

at least one air-bearing sleeve disposed in the housing;

at least one piston disposed within the at least one sleeve and having at least one pressure chamber formed by the piston and air-bearing sleeve;

at least one valve that may be used to modulate the flow of fluid from the pressure chamber to an exhaust pressure;

at least one voice coil motor disposed within the piston;

at least one air-bearing pad disposed at one end of the piston opposite the pressure chamber and acting against a surface of the surface handler opposite the flat surface wherein the pressure from the air-bearing pad against the surface handler is opposed by a magnetic attraction between the surface handler and the piston;

a plurality of magnetic regions located at preselected portions of the surface handler;

a plurality of radial actuators disposed on the housing and corresponding to at least a portion of the plurality of magnetic regions of the surface handler; and

a plurality of tangential actuators that correspond to at least a portion of the magnetic regions of the surface handler.

2. The apparatus of claim 1, wherein the housing moves the surface handler in at least an X direction, a Y direction, a Z direction, a yaw direction, a roll direction and a pitch direction.

3. The apparatus of claim 2, wherein the housing includes at least one actuator for each direction of motion.

4. The apparatus of claim 3 wherein the planar surface handler is completely supported and transported by the actuators.

5. The apparatus of claim 1, wherein the surface handler is a chuck.

6. The apparatus of claim 5, wherein the chuck is a vacuum chuck.

7. The apparatus of claim 6, wherein the chuck is an anodized aluminum alloy circular cylinder.

8. The apparatus of claim 6, wherein the chuck has a central region having an array of grooves embedded in the flat surface and connected to a vacuum control line.

9. The apparatus of claim 8, wherein the central region is a circle having a radius of approximately 200 mm, and the array of grooves is a plurality of concentric circular grooves having a common center at approximately a center of the chuck.

10. The apparatus of claim 8, wherein the chuck further includes a peripheral region having a second array of grooves embedded in the flat surface and connected to a second vacuum control line.

11. The apparatus of claim 10, wherein the second array of grooves is an annular region of approximately 200 to 300 mm radius.

12. The apparatus of claim 1, wherein the substantially flat surface of the surface handler includes a plurality of vacuum conduits.

13. The apparatus of claim 12 wherein the plurality of vacuum conduits includes at least two different vacuum control areas, each area having a separately controllable vacuum pressure source.

14. The apparatus of claim 12 wherein the plurality of vacuum conduits are arranged in rings.

15. The apparatus of claim 1, wherein the surface handler does not directly contact the housing.

16. The apparatus of claim 1, wherein the plurality of position sensors is three.

17. The apparatus of claim 16, wherein the plurality of position sensors provide position measurements in two dimensions.

18. The apparatus of claim 1, wherein the surface handler includes a plurality of holes through which pins, fixedly attached to the housing, are inserted perpendicular to the flat surface of the surface handler, and, in response to a signal that lowers the surface handler with respect to the housing, the pins extend above the flat surface by at least a predetermined distance.

19. The apparatus of claim 18, wherein the predetermined distance is greater than approximately 6 mm.

20. The apparatus of claim 19, wherein the plurality of holes is three.

21. The apparatus of claim 18, wherein the plurality of pins are hollow.

22. The apparatus of claim 21, wherein the hollow pins are connected to a vacuum line.

23. The apparatus of claim 1, wherein the surface handler has an approximately circular top surface.

24. The apparatus of claim 1, wherein the magnet of the voice coil motor disposed within the piston provides the source of magnetic flux that preloads the surface handler against an air bearing pad.

25. The apparatus of claim 24, wherein the magnet attracts the ferromagnetic region of the surface handler against the air bearing with a force sufficient to establish a desired stiffness and corresponding flying-height between the surface handler and the air-bearing pad disposed on top of the piston.

26. The apparatus of claim 1, wherein the piston includes an air-bearing pad disposed above the surface of the piston and allowed to pivot with respect to a vertical axis of the piston.

27. The apparatus of claim 26, wherein the pivot is a ball pivot.

28. The apparatus of claim 1, wherein the fluid in the sleeve is air.

29. The apparatus of claim 28, further comprising:

a controller that modulates the valve to regulate the pressure in the pressure chamber and modulates the force in the voice coil motor in order to adjust the height of the surface handler with respect to the housing

30. The apparatus of claim 28, wherein the piston has no sealing surface with respect to the sleeve to prevent the compressed air from leaking out at a controlled rate.

31. The apparatus of claim 30, wherein the controlled rate is determined by relative diameters of the piston and the sleeve.

32. The apparatus of claim 31, further comprising:

a single valve connected to each pressure chamber and normally operated in a partially open state to regulate the flow of fluid from the pressure chamber to an external source of pressure that is maintained at a pressure substantially below the nominal chamber pressure.

33. The apparatus of claim 32, wherein the valve is opened or closed in proportion to a signal from the controller in order to regulate the net mass flow of fluid between the fluid entering the chamber from the air-bearing sleeve and the mass flow of fluid leaving the chamber through the valve.

34. The apparatus of claim 1, wherein the plurality of pistons is three.

35. The apparatus of claim 34, wherein the pistons are driven differentially to generate motion around the X and Y axes.

36. The apparatus of claim 34, wherein the controller operates the valve and corresponding voice coil motor so as to minimize the power dissipated in each voice coil motor.

37. The apparatus of claim 1, wherein the plurality of magnetic regions of the surface handler is three.

38. The apparatus of claim 37, wherein the plurality of tangential actuators is three.

39. The apparatus of claim 38, wherein the coils of the tangential actuators are disposed in a portion of the housing and the low-reluctance components of the actuators are fixed in the surface handler.

40. The apparatus of claim 1, wherein the surface handler has a plurality of ferromagnetic surfaces disposed around a peripheral portion of the surface handler that interact with a plurality of radially-acting electromagnetic actuators disposed in the housing.

41. The apparatus of claim 40, wherein the plurality of actuators is three.

42. The apparatus of claim 1, wherein the surface handler further includes a plurality of projections disposed in a symmetric pattern on the surface opposite the flat surface and wherein the housing includes a plurality of depressions disposed in a corresponding pattern.

43. The apparatus of claim 42, wherein the plurality of projections equals three.

44. The apparatus of claim 42, wherein the plurality of projections further includes balls and the plurality of depressions include vee-grooves.

45. The apparatus of claim 1, further comprising:

a control system that controls the plurality of radial actuators in a differential mode wherein the total amount of power provided to all of the radial actuators is maintained at a substantially constant value while generating net forces between the housing and surface handler in the X and Y plane.

46. The apparatus of claim 1, wherein the housing further includes a recessed bottom portion disposed to fit into a recess in a corresponding X-Y stage.

47. An apparatus for manipulation of a substrate, comprising:

a handler having a flat surface that holds a substrate;

a housing that holds the handler;

a plurality of tangential actuators that cause rotation of the handler about an axis perpendicular to the surface of the handler; and

a plurality of radial actuators, each actuator moving the handler with respect to the housing in a selected radial direction independent of rotation caused by the tangential actuators, wherein an increase in the force level of one of the plurality of radial actuators is counterbalanced by a reduction in the force level of at least one other of the radial actuators so that the power consumed by all of the radial actuators together is substantially constant.

48. An apparatus for manipulation of a substrate, comprising:

a handler that holds a substrate;

a housing having a bottom surface that holds the handler; and

a plurality of vertical actuators disposed in the housing to move the handler toward and away from the bottom surface of the housing, wherein an increase in distance from the bottom surface to the handler provided by one of the vertical actuators is counterbalanced by a decrease in distance from the handler to the bottom surface by another one of the vertical actuators to provide a rotation about an axis of rotation perpendicular to a direction of motion provided by the vertical actuators, wherein the axis of rotation is disposed at a location corresponding to a location in a substrate provided on the handler.

49. The apparatus of claim 48, wherein the vertical actuators include a magnet that attracts a magnetic plate disposed on the bottom surface of the handler and an air bearing that pushes against the plate.

50. The apparatus of claim 48, wherein the handler can rotate in a plane that is substantially perpendicular to the direction of motion provided by the vertical actuators.

51. An apparatus for manipulation of a substrate, comprising:

a handler that holds the substrate;

a housing that holds the handler;

a plurality of patterned surfaces disposed on one of;

the housing and the handler, wherein the patterned surfaces include one of the following combinations;

at least six linear arrays, at least four linear arrays and at least one grid array, at least two linear arrays and at least two grid arrays, or at least three grid arrays; and

a plurality of readers that read the combination to determine a location of the substrate in six degrees of freedom.

52. An apparatus, according to claim 51, wherein the readers are optical encoders.

53. An apparatus for manipulation of a substrate, comprising:

a handler that holds the substrate;

a housing that holds the handler; and

a plurality of actuators that move the handler in response to at least one control signal, wherein the plurality of actuators further includes at least one high frequency actuator and at least one low frequency actuator that provide motion in a single direction and wherein the at least one control signal includes a high frequency portion that is provided to the at least one high frequency actuator and a low frequency portion that is provided to the at least one low frequency actuator.

54. The apparatus of claim 53, wherein the at least one low frequency actuator reduces static forces on the at least one high frequency actuator.

55. The apparatus of claim 53, wherein the at least one low frequency actuators includes at least one radial electromagnet.

56. The apparatus of claim 53, wherein the at least one high frequency actuator includes at least one tangential electromagnet.

57. The apparatus of claim 53, wherein the at least one low frequency actuator is a pneumatic actuator.

58. The apparatus of claim 57, wherein the pneumatic actuator actuates the handler in a vertical direction.

59. The apparatus of claim 53, wherein the at least one high frequency actuator includes an electromagnetic actuator that provides a force in a vertical direction on the handler.

60. An apparatus for manipulation of a substrate, comprising:

a handler that holds the substrate;

a housing that holds the handler; and

a plurality of vertical actuators disposed in the housing to move the handler toward and away from the bottom surface of the housing, wherein the vertical actuators are driven differentially to counteract and compensate for any vertical off axis forces applied to the substrate.

61. The apparatus of claim 60, wherein the vertical actuators include a magnet that attracts a magnetic plate disposed on a bottom surface of the handler and an air bearing that pushes against the plate.

62. The apparatus of claim 60, further comprising:

a ball disposed in each vertical actuator and a corresponding vee-groove disposed in the handler to allow roll and pitch motion of the handler.

63. The apparatus of claim 60, wherein compensation for vertical off axis forces is provided primarily by a pneumatic actuator.

64. An actuator comprising:

a piston movably guided by a fluid-bearing;

a fluid chamber formed at one end of the piston having a chamber pressure controlled by balancing a fluid flowing into the fluid chamber with fluid exiting the chamber through a controllable orifice; and

a voice coil motor disposed to move the piston located within the confines of the piston.

65. The apparatus of claim 64, further comprising:

a control system that supplies large low-frequency forces by modulating the chamber pressure, and supplies low amplitude high-frequency forces via the voice coil motor.

66. An actuator that manipulates an object, comprising:

at least three tangentially acting voice coil motors disposed to move the object relative to the housing in a yaw direction;

at least three radially acting electromagnet actuators maintaining a substantially constant gap between the object and a housing independent of motion in the yaw direction; and

a control system that supplies the object with large low-frequency forces in a plane of the object using the radially acting electromagnet actuators, and supplies low amplitude high-frequency forces in the plane of the object and provides forces for motion in the yaw direction using the tangential voice coil motors.

67. A substrate manipulator providing six degrees of controllable motion for an object, comprising:

a housing;

a substrate handler that holds the object and does not contact the housing;

at least three actuators that move the object in Z, Roll and Pitch directions, and at least three actuators that move the object in X, Y and Yaw directions.

68. A substrate manipulator providing control of movements of an object in the Z, roll and pitch directions, comprising:

a housing;

a substrate handler that holds the object disposed in the housing; and

at least three actuators that move the object in a Z direction.

69. A substrate manipulator providing control of movements in the Z, roll, pitch and yaw directions, comprising:

a housing;

a surface handler disposed in the housing;

at least one hub, disposed concentric to a center point of the housing and free to rotate about the Z axis using at least three magnetically preloaded air bearing regions located between the housing and the hub;

a pair of magnetically preloaded bearings that constrain the hub to rotate substantially about the axis of the housing;

at least three tangential voice coil motors that provide a yaw moment without creating any substantial XY force on the hub relative to the housing; and

at least three Z actuators to move the surface handler with respect to the hub.