PROCESS FOR POLISHING THIN ELEMENTS

• US 3,841,031 A
• Filed: 10/30/1972
• Issued: 10/15/1974
• Est. Priority Date: 10/21/1970
• Status: Expired due to Term

• Current Assignee: MEMC Electronic Materials, Inc. (SunEdison, Inc.)
• Original Assignee: Robert J. Walsh
• Inventors: Walsh, Robert J.
• Primary Examiner(s): Whitehead, Harold D.
• Application Number:
  US05/301,940
• Time in Patent Office: 715 Days
• Field of Search: 51/131,216,283 156/17
• US Class Current: 451/41
• CPC Class Codes: B24B 37/04 designed for working plane surfaces
• CPC Class Codes: B24B 37/107 in a rotary movement only, about an axis being stationary during lapping

Abstract

A process for the waxless polishing of thin fragile wafers which includes positioning a wafer on a mounting pad having a coefficient of static friction with respect to the wafer such that the wafer may be moved into frictional engagement with a polishing surface without becoming disengaged from the mounting pad. The wafer and mounting pad are continuously rotated during polishing about a central axis normal to the plane of the wafer and such continuous rotation produces improved edge-rounding of the polished wafer.

Claims

1. A process for free polishing of wafers, said process comprising:

a. positioning a wafer to be polished under pressure between a frictional retention surface and an area of a polishing surface, said frictional retention surface initially having a higher coefficient of static friction with respect to said wafer than the coefficient of static friction said area of the polishing surface with respect to said wafer;

b. initiating relative circular motion between said frictional retention surface and said area of the polishing surface with said wafer being retained and remaining stationary with respect to said frictional retention surface solely by virtue of static frictional force between said wafer and said frictional retention surface in sliding frictional engagement with said area of the polishing surface, as a result of said higher coefficient of friction of said frictional retention surface with respect to said wafer;

c. continuing said relative circular motion until said wafer is polished as a result of said sliding frictional engagement with the polishing surface, said wafer when polished having an increased coefficient of friction with respect to the polishing surface;

d. terminating said relative circular motion; and

e. removing said wafer from beneath said frictional retention surface, as said relative circular motion is terminated by increasing the friction of said polishing surface with respect to said wafer causing said wafer to cease said sliding engagement with the polishing surface and to overcome said static frictional force retaining the wafer so as to initiate sliding engagement with said frictional retention surface as a result of said increased coefficient of friction of the polished wafer with respect to the polishing surface, whereby said wafer is disengaged and freed from said frictional retention surface without requiring said frictional retention surface to be lifted from said polishing surface.

2. A process as set forth in claim 1 further comprising dynamically transferring said sliding frictional engagement of the wafer with said area of the polishing surface to sliding frictional engagement with a further area of the polished surface while continuing without interruption said relative circular motion to cause finish polishing of said wafer.

3. A process as set forth in claim 2 wherein said further area of the polishing surface has a higher coefficient of friction with respect to the first-said area of the polishing surface.

4. A process as set forth in claim 1 wherein said fractional retention surface and said polishing surface are each constituted by poromeric materials.

5. A process as set forth in claim 4 wherein said poromeric materials comprise fiber reinforced polyurethane.

6. A process for free polishing of wafers, said process comprising:

a. positioning a wafer to be polished under pressure between a frictional retention surface and an area of a polishing surface, said frictional retention surface initially having a higher coefficient of friction with respect to said wafer than said area of the polishing surface;

b. initiating relative circular motion between said frictional retention surface and said area of the polishing surface with said wafer being retained and remaining stationary with respect to said frictional retention surface solely by virtue of static force between said wafer and said frictional retention surface, while said wafer moves in sliding frictional engagement with said area of the polishing surface, as a result of said higher coefficient of friction of said frictional retention surface with respect to said wafer as compared with the coefficient of friction said area of the polishing surface;

c. continuing said relative circular motion until said wafer is polished as a result of said sliding frictional engagement with the polishing surface, said wafer when polished having an increased coefficient of friction with respect to the polishing surface;

d. terminating said relative circular motion; and

e. removing said wafer from beneath said frictional retention surface by increasing the friction of said polishing surface with respect to said wafer and by producing an additional relative motion between said frictional retention surface and said polishing surface with the relative differences in forces of static friction simultaneously exerted on said wafer by said retention and polishing surfaces being sufficient to disengage and free said wafer from frictional retention with said frictional retention surface without requiring said frictional surface to be lifted from said polishing surface and whereby said wafer is thereafter easily removed from said polishing surface when at rest.