System for real-time control of semiconductor wafer polishing including optical montoring

• US 5,730,642 A
• Filed: 01/30/1997
• Issued: 03/24/1998
• Est. Priority Date: 08/25/1993
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Sandhu, Gurtej S., Doan, Trung Tri
• Primary Examiner(s): Rose, Robert A.
• Assistant Examiner(s): NGUYEN, GEORGE BINH MINH
• Application Number:
  US08/791,312
• Time in Patent Office: 418 Days
• Field of Search: 451/2, 451/6, 451/41, 451/285-289
• US Class Current: 451/6
• CPC Class Codes: B23Q 15/013 Control or regulation of feed movement B23Q15/12 takes precedence
• CPC Class Codes: B23Q 15/12 Adaptive control, i.e. adjusting itself to have a performance which is optimum according to a preassigned criterion
• CPC Class Codes: B24B 13/015 of television picture tube viewing panels, headlight reflectors or the like
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/015 Temperature control
• CPC Class Codes: B24B 37/107 in a rotary movement only, about an axis being stationary during lapping
• CPC Class Codes: B24B 37/12 Lapping plates for working plane surfaces
• CPC Class Codes: B24B 37/205 provided with a window for inspecting the surface of the work being lapped
• CPC Class Codes: B24B 49/003 involving acoustic means
• CPC Class Codes: B24B 49/02 according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent B24B49/12 takes precedence
• CPC Class Codes: B24B 49/04 involving measurement of the workpiece at the place of grinding during grinding operation
• CPC Class Codes: B24B 49/10 involving electrical means B24B49/02, B24B49/08 take precedence
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: B24B 57/02 for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/34403 RTI real time, kernel, processing
• CPC Class Codes: G05B 2219/37398 Thickness
• CPC Class Codes: G05B 2219/37602 Material removal rate
• CPC Class Codes: G05B 2219/45026 Circuit board, pcb
• CPC Class Codes: G05B 2219/45199 Polish
• CPC Class Codes: G05B 2219/45232 : CMP chemical mechanical polishing of wafer
• CPC Class Codes: G05B 2219/49052 : Accessory, coolant
• CPC Class Codes: G05B 2219/49057 : Controlling temperature of workpiece, tool, probe holder

Abstract

A system for polishing a semiconductor wafer, the system comprising a wafer polishing assembly for polishing a face of a semiconductor wafer at a polishing rate and a polishing uniformity, the wafer polishing assembly including a platen subassembly defining a polishing area, a slurry supply system delivering a slurry to the polishing area, and a polishing head selectively supporting a semiconductor wafer and holding a face of the semiconductor wafer in contact with the platen subassembly; and an optical measurement system measuring film thickness at multiple different locations on the wafer face while the wafer is under a liquid, wherein drying of the wafer is avoided while the measurements are taken.

Claims

1. A system for polishing a semiconductor wafer, the system comprising:

a wafer polishing assembly for polishing a face of a semiconductor wafer at a polishing rate and a polishing uniformity, the wafer polishing assembly including a platen subassembly defining a polishing area, a slurry supply system configured to deliver a slurry to the polishing area, and a polishing head selectively supporting a semiconductor wafer and configured to hold a face of the semiconductor wafer in contact with the platen subassembly;

an optical measurement system including a liquid filled, wafer receiving area which selectively receives the wafer, the wafer receiving area being spaced apart from the platen in a direction perpendicular to the axis of rotation of the platen, the optical measurement system measuring film thickness at multiple different locations on the wafer face; and

a robot selectively moving the wafer between the platen and the wafer receiving area.

2. A system in accordance with claim 1 wherein the optical measurement system comprises movable optics which scan the wafer face while the wafer face remains stationary.

3. A system in accordance with claim 1 wherein the optical measurement system includes pattern recognition system.

4. A system in accordance with claim 2 wherein the optical measurement system comprises an optical window, wherein the wafer receiving area is located on one side of the window, and wherein the optics are located on the other side of the window.

5. A system in accordance with claim 3 and further comprising end point detection means for determining if polishing of the wafer is complete, the end point detection means comprising means for causing the pattern recognition system to compare the thickness of a film on the wafer at various locations of the wafer with desired thicknesses.

6. A system in accordance with claim 1 wherein the polishing head supports the semiconductor wafer and holds the face of the semiconductor wafer in contact with the platen subassembly under an adjustable polishing force to polish the wafer face, and further comprising a controller selectively adjusting the polishing force during polishing of the wafer.

7. A system in accordance with claim 1 wherein the platen subassembly is rotatable about an axis and rotates at a variable platen velocity, and further comprising a controller selectively adjusting the velocity of the platen during polishing of the wafer.

8. A system in accordance with claim 1 wherein the polishing head is rotatable about an axis and rotates at a variable wafer velocity, and further comprising a controller selectively adjusting the velocity of the polishing head during polishing of the wafer.

9. A system in accordance with claim 1 wherein the polishing head is movable across the platen subassembly along an adjustable polishing path, and further comprising a controller selectively adjusting the path of the polishing head during polishing of the wafer.

10. A system in accordance with claim 1 wherein the polishing head is movable across the platen subassembly at an adjustable wafer movement rate, and further comprising a controller selectively adjusting the rate of movement of the polishing head across the platen subassembly, during polishing of the wafer.

11. A system for polishing a semiconductor wafer comprising:

a wafer polishing assembly for polishing a face of a semiconductor wafer at a polishing rate and a polishing uniformity, the wafer polishing assembly including a platen, a polishing head which supports the semiconductor wafer, and a polishing head displacement mechanism which moves the polishing head and wafer across the platen along an adjustable polishing path, the wafer polishing assembly having a plurality of controllable operational parameters that upon variation change the polishing rate and polishing uniformity;

a controller operably coupled to the wafer polishing assembly for monitoring and managing in situ at least one of the operational parameters of the wafer polishing assembly;

a processor operably coupled to the controller for determining a set of desired operational parameters based on the monitored operational parameters and outputting control information indicative of the desired operational parameters to the controller, the controller adjusting in situ at least one of the operational parameters of the wafer polishing assembly, including the polishing path, in response to the control information from the processor to effectuate a new polishing rate and a new polishing uniformity as the wafer polishing assembly continues to polish the face of the semiconductor wafer; and

an optical measurement system selectively measuring film thickness at multiple different locations on the wafer face, the optical measurement system including a liquid filled wafer receiving area keeping the wafer face wet while the film thickness measurements are taken.

12. A system in accordance with claim 11 wherein the optical measurement system comprises movable optics which scan the wafer face while the wafer face remains stationary.

13. A system in accordance with claim 11 wherein the optical measurement system includes a pattern recognition system.

14. A system in accordance with claim 12 wherein the optical measurement system comprises an optical window, wherein the wafer receiving area is located on one side of the window, and wherein the optics are located on the other side of the window.

15. A system in accordance with claim 14 wherein the optical window is spaced apart from the platen, and further comprising a robot selectively moving the wafer between the platen and the wafer receiving area.

16. A system in accordance with claim 13 and further comprising an end point detector which determines if polishing of the wafer is complete, the end point detector comprising means for causing the pattern recognition system to compare the thickness of a film on the wafer at various locations of the wafer with desired thicknesses.

17. A system in accordance with claim 11 wherein the polishing head supports the semiconductor wafer and holds the face of the semiconductor wafer in contact with the platen subassembly under an adjustable polishing force to polish the wafer face, and wherein the controller selectively adjusts the polishing force during polishing of the wafer.

18. A system in accordance with claim 11 wherein the platen subassembly is rotatable about an axis and rotates at a variable platen velocity, and wherein the controller selectively adjusts the velocity of the platen during polishing of the wafer.

19. A system in accordance with claim 11 wherein the polishing head is rotatable about an axis and rotates at a variable wafer velocity, and wherein the controller selectively adjusts the velocity of the polishing head during polishing of the wafer.

20. A system in accordance with claim 11 wherein the polishing head is movable across the platen subassembly along an adjustable polishing path, and wherein the controller selectively adjusts the path of the polishing head during polishing of the wafer.

21. A system in accordance with claim 11 wherein the polishing head is movable across the platen subassembly at an adjustable wafer movement rate, and wherein the controller selectively adjusts the rate of movement of the polishing head during polishing of the wafer.

22. A system for polishing a semiconductor wafer comprising:

a wafer polishing assembly for polishing a face of a semiconductor wafer at a polishing rate and a polishing uniformity, the wafer polishing assembly including a platen, a polishing head which supports the semiconductor wafer, and a polishing head displacement mechanism which moves the polishing head and wafer across the platen, the wafer polishing assembly having a plurality of controllable operational parameters that upon variation change the polishing rate and polishing uniformity;

a controller operably coupled to the wafer polishing assembly for monitoring and managing in situ at least one of the operational parameters of the wafer polishing assembly;

a processor operably coupled to the controller for determining a set of desired operational parameters based on the monitored operational parameters and outputting control information indicative of the desired operational parameters to the controller, the controller adjusting in situ at least one of the operational parameters of the wafer polishing assembly in response to the control information from the processor to effectuate a new polishing rate and a new polishing uniformity as the wafer polishing assembly continues to polish the face of the semiconductor wafer;

a detector operating on the wafer and communicating with the processor to determine whether polishing of the wafer is complete, the detector including an optical measurement system measuring film thickness at multiple different locations on the wafer face while the wafer is under a liquid, the optical measurement system including an optical window spaced apart from the platen, a liquid containing wafer receiving area above the window movable optics below the window which scan the wafer face while the wafer face remains stationary, and a pattern recognition system; and

a robot selectively moving the wafer between the platen and the wafer receiving area above the window.

23. A system for polishing a semiconductor wafer, the system comprising:

a wafer polishing assembly for polishing a face of a semiconductor wafer, the wafer polishing assembly including a platen, and a polishing head selectively supporting a semiconductor wafer and configured to hold a face of the semiconductor wafer in contact with the platen;

a detector operating on the wafer to determine whether polishing of the wafer is complete, the detector including an optical measurement system including a wafer receiving area which selectively receives the wafer, the wafer receiving area being spaced apart from the platen in a direction perpendicular to the axis of rotation of the platen, the optical measurement system measuring film thickness at multiple different locations on the wafer face; and

a robot selectively moving the wafer between the platen and the wafer receiving area.

24. A system for polishing a semiconductor wafer, the system comprising:

a wafer polishing assembly for polishing a face of a semiconductor wafer, the wafer polishing assembly including a platen, and a wafer receiving polishing head facing the platen and configured to support a semiconductor wafer and hold a face of the semiconductor wafer in contact with the platen;

a detector operating on the wafer to determine whether polishing of the wafer is complete, the detector including an optical measurement system which selectively receives the wafer, the wafer receiving area being spaced apart from the platen in a direction perpendicular to the axis of rotation of the platen, the optical measurement system measuring film thickness at multiple different locations on the wafer face; and

a robot configured to periodically move the wafer between the platen and the wafer receiving area.