Vacuum-grooved membrane abrasive polishing wafer workholder

• US 9,233,452 B2
• Filed: 08/31/2014
• Issued: 01/12/2016
• Est. Priority Date: 10/29/2012
• Status: Active Grant

• Current Assignee: Cameron M. Duescher, Wayne O. Duescher
• Original Assignee: Cameron M. Duescher, Wayne O. Duescher
• Inventors: Duescher, Wayne O., Duescher, Cameron M.
• Primary Examiner(s): NGUYEN, GEORGE BINH MINH
• Application Number:
  US14/474,157
• Publication Number:
  US 20140370787A1
• Time in Patent Office: 499 Days
• Field of Search: 451/41, 451285-290, 451/388
• US Class Current: 1/1
• CPC Class Codes: B24B 37/042 operating processes therefor
• CPC Class Codes: B24B 37/30 for single side lapping of plane surfaces
• CPC Class Codes: H01L 21/304 Mechanical treatment, e.g. grinding, polishing, cutting H01L21/30625 takes precedence

Abstract

Hard-material, flat-surfaced workpieces such as semiconductor wafers or sapphire disks are attached with vacuum to the flexible elastomeric membrane of a wafer carrier that allows one surface of the workpiece to be in conformal abrading contact with a moving flat-surfaced abrasive. The elastomeric membrane external wafer attachment surface has a pattern of recessed vacuum grooves and vacuum is supplied to the grooves to firmly attach the rigid-material silicon wafer in flat-surfaced contact with the membrane. The attached wafer seals the vacuum grooves and also provides lateral stiffness to the center portion of the membrane. An outer annular extension of the flexible elastomer membrane maintains the wafer at its original membrane-centered location when abrading forces are applied to the rotating wafer. The rotating wafer peripheral edge does not contact a rigid retaining ring during a wafer polishing procedure. Fixed-abrasive disks or raised-island abrasive disks are attached to a rotatable flat-surfaced platen.

Claims

1. An abrasive polishing wafer carrier apparatus comprising:

a) a movable carrier housing attached to a rotatable shaft having a rotatable shaft axis of rotation;

b) a flexible membrane having a top surface, a nominally-flat bottom surface attached to the movable carrier housing and flexible membrane thickness, wherein the flexible membrane nominally-flat bottom surface has recessed vacuum grooves;

c) a vacuum source fluid-coupled to the flexible membrane recessed vacuum grooves; and

d) a pressure source fluid-coupled to a sealed pressure chamber formed by the flexible membrane and the movable carrier housing.

2. The apparatus of claim 1 wherein the flexible membrane has an outer annular portion that is flexible in a direction that is nominally-perpendicular to the flexible membrane nominally-flat bottom surface and is nominally-stiff in directions parallel to the flexible membrane nominally-flat bottom surface.

3. The apparatus of claim 1 wherein a circular wafer having opposed nominally-flat top and bottom surfaces is positioned such that the circular wafer nominally-flat top surface is in flat-surfaced conformal contact with the flexible membrane nominally-flat bottom surface, wherein the flexible membrane recessed vacuum grooves are sealed by the wafer and wherein vacuum present in the flexible membrane recessed vacuum grooves attaches the circular wafer to the flexible membrane nominally-flat bottom surface.

4. The apparatus of claim 2 wherein the flexible membrane outer annular portion is reinforced with reinforcing materials comprising:

fibers, filaments, strings, wires, cables, woven mats, non-woven fabric, polymers, and laminated materials wherein the reinforced flexible membrane outer annular portion is flexible in a direction that is nominally-perpendicular to the flexible membrane nominally-flat bottom surface and is nominally-stiff in directions parallel to the flexible membrane nominally-flat bottom surface.

5. The apparatus of claim 2 wherein the flexible membrane outer annular portion is an integral part of the flexible membrane.

6. The apparatus of claim 2 wherein the flexible membrane outer annular portion is attached to the flexible membrane.

7. The apparatus of claim 1 wherein the flexible membrane comprises flexible materials selected from the group consisting of:

elastomers, silicone rubber, room temperature vulcanizing silicone rubber, natural rubber, synthetic rubber, thermoset polyurethane, thermoplastic polyurethane, flexible polymers, composite materials, polymer-impregnated woven cloths, sealed fiber materials, impervious flexible materials, and flexible metals.

8. The apparatus of claim 3 wherein the flexible membrane outer annular portion transmits rotational torque from the movable carrier housing to the flexible membrane and wherein the flexible membrane transmits the rotational torque to the wafer that is vacuum-attached to the flexible membrane.

9. The apparatus of claim 3 wherein the flexible membrane outer annular portion has sufficient radial stiffness to maintain the center of the circular wafer that is vacuum-attached to the flexible membrane at a position nominally at the rotation axis of the rotatable shaft when the rotating abraded wafer is subjected to abrading forces.

10. The apparatus of claim 3 wherein the abrasive polishing wafer carrier apparatus movable carrier housing is tiltable through a selected tilt angle measured between the rotatable shaft axis of rotation and a perpendicular to the rotatable platen flat abrading surface.

11. The apparatus of claim 3 wherein the movable carrier housing is moveable to enable movement of the wafer attached to the flexible membrane a selected distance from a rotatable platen abrading surface.

12. A process for using the apparatus of claim 3 to polish the wafer or a workpiece comprising attaching the wafer or the workpiece with vacuum to the flexible membrane, moving the movable carrier housing so that the wafer or a workpiece nominally-flat bottom surface is positioned in flat-surfaced abrading contact with a rotatable abrading platen flat abrasive coating and supplying

fluid pressure to the sealed pressure chamber formed by the flexible membrane and the movable carrier housing so that the fluid pressure is transmitted through the flexible membrane thickness to apply a controlled abrading pressure uniformly across the full abraded bottom surface of the wafer and both the rotatable abrading platen having the flat abrading surface and the flexible membrane having the attached wafer are rotated to polish the wafer or the workpiece.

13. A process for using the apparatus of claim 3 wherein fluid pressure is applied to the flexible membrane bottom surface recessed vacuum grooves upon completion of a wafer abrading procedure to separate the wafer from the flexible membrane bottom surface.

14. A process for using the apparatus of claim 10 wherein the abrasive polishing wafer carrier apparatus movable carrier housing is tilted a selected tilt angle measured between the rotatable shaft axis of rotation and a perpendicular to the rotatable platen flat abrading surface and both the rotatable abrading platen having the flat abrading surface and the flexible membrane having the attached wafer are rotated to polish a wafer or workpiece.

15. A process according to claim 12 wherein the abrasive on the rotatable platen flat abrading surface is provided by a liquid slurry comprising:

abrasive particles and abrasive-process enhancing chemicals.

16. A process according to claim 12 wherein the abrasive on the rotatable platen flat abrading surface is provided by a flexible fixed-abrasive disk that is conformably attached to the platen flat abrading surface.

17. A process according to claim 12 wherein the abrasive on the rotatable platen flat abrading surface is provided by a flexible flat-surfaced abrasive disk that is conformably attached to the platen flat abrading surface and the flexible abrasive disk has an annular band of fixed-abrasive coated raised islands and coolant water or coolant water containing abrasive-process enhancing chemicals is applied to cool the wafer during the abrading process.

18. The apparatus of claim 1 wherein the abrasive polishing wafer carrier apparatus has multiple sealed pressure chambers formed by portions of the flexible membrane and the movable carrier housing.

19. The apparatus of claim 1 wherein the abrasive polishing wafer carrier apparatus has a sealed flexible-diaphragm pressure chamber formed by a rotatable flexible annular diaphragm and the movable carrier housing wherein fluid pressure supplied to the flexible-diaphragm pressure chamber will move the movable carrier housing downward relative to a vertical rotatable shaft and vacuum supplied to the flexible-diaphragm pressure chamber will move the movable carrier housing upward relative to the vertical rotatable shaft.

20. A process for using the apparatus of claim 19 wherein vacuum applied to the sealed flexible-diaphragm pressure chamber moves the movable carrier housing upward relative to the vertical rotatable shaft and wherein fluid pressure applied to the sealed flexible-diaphragm pressure chamber moves the movable carrier housing downward relative to the vertical rotatable shaft.