Chemical mechanical polishing retaining ring

Abstract

A chemical mechanical head includes a retaining ring to maintain a substrate beneath the mounting surface during polishing. The retaining ring has a lower portion with a bottom surface for contacting a polishing pad during polishing and made of a first material, such as plastic, and an upper portion made of a second, different material, such as metal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 09/892,143, filed Jun. 25, 2001 assembly 146 includes a the retaining ring 162 which is attached to the a backing ring 148. A series of compression springs 172 (i.e., first set of elastic members) support the backing ring 148 on the lip 110 of the descending wall 104. An expandable retaining ring extending bladder 170 can be pressurized through gas supply passage 171 (i.e., a second set of elastic members). When bladder 170 is pressurized, the retaining ring assembly 146 is extended to a location adjacent the wafer 142 as shown by the dashed lines 146a in FIG. 2.

A second configuration of the polishing head of the present invention is shown in FIG. 3, wherein the seal 130 is a downwardly extending lip seal 136 received on the outer perimeter of the backing member 124, and secured thereon by a backing ring 138 extending about the outer circumference of the lip seal 36. The lip seal 136 is preferably a thin, elastic, member having a rectangular cross section. A portion of the lip seal 136 extends from the underside, or wafer engaging side, of the backing member 124, to engage the upper surface of the wafer 142 immediately inwardly of the perimeter of the wafer 142. As with the O-ring 134, the engagement of the lip seal 136 with the wafer forms a pocket (including wafer recess 126 and a shoulder area inside lip seal) which may be evacuated or pressurized. The lip seal 136 and the O-ring 134 provide sufficient contact between the surface of the substrate and the surface of the seal to create a rotational force due to friction between the two to keep them in contact so that the substrate turns with the polishing head.

The Retaining Ring

Referring again to FIG. 1, the polishing head 100 also includes a retaining ring assembly 146 to ensure that the wafer 142 does not slip out from beneath the head during polishing operations. The retaining ring 162 has through holes 164 and counterbores 166 therein (FIG. 3). Retaining ring screws 168 are placed therethrough and threaded into a series of backing-ring bottom-surface threaded holes 160 to hold the retaining ring 162 to a backing ring 148. The retaining ring 162 is preferable made of Delrin or similar plastic material. The backing ring 148 is preferably made of aluminum as are all of the other metal pieces except for the bellows which is stainless steel. The backing ring 148 has a bottom surface 158 facing the retaining ring 162. The backing ring 148 includes an outside flange 152 having a top face 154 facing the bladder 170 and a bottom face 156 facing the series of compression springs 172. The backing ring 148 has an inside flange 150 having a lower face 151 which extends inwardly over the diameter of the retaining member 124a such that when the backing member 124a is raised beyond a certain point the backing retaining ring assembly 146 also rises.

FIGS. 2 and 3 show details of the retaining ring assembly 146. The backing ring 148 is urged upwardly away from the lip 110 of the descending wall 104 by a plurality of (for example 6-12) compression springs 172. When the bladder 170 is pressurized to extend the retaining ring assembly 146 to its operating position as shown by the dashed lines 146a in FIG. 2, the retaining ring 162 surrounds the edge of the wafer being polished. This prevents the wafer from sliding out under the wafer backing member 124, or 124a. Inflation of the bladder 170 through the gas passage 171 provides a downward force to oppose the compression springs 172 and forces the retaining ring 162 toward and possibly against the polishing pad 182. A continuous continuously pressurized bladder could be employed to replace the series of springs 172 to provide uniformly distributed retracting forces.

The lower surface 151 of the backing ring inside flange 150 is configured so that as the plastic Delrin material of the wafer perimeter retaining ring 162 wears away, the travel of retaining ring is limited by the interference between the lower surface 151 of the upper flange 150 and the top of the wafer backing member 124a so that the head of the retaining ring retaining screws 168 cannot touch the polishing pad. This prevents the heads of retaining screws 168 from coming in contact with the polishing pad and introducing undesirable contaminants. The perimeter retaining ring can also be mounted without screws, such as by use of key slots requiring insertion and partial rotation to retain the key and opposing grooves having O-rings sized to engage and span the space between grooves.

While the invention has been described with regard to specific embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A carrier head for a chemical mechanical polishing apparatus, comprising:

a substrate backing member;

a first chamber to provide a first downward pressure on the substrate backing member;

a retaining ring assembly to maintain a substrate beneath the substrate backing member during polishing, the retaining ring assembly vertically movable relative to the substrate backing member, the retaining ring assembly including a lower portion retaining ring having a bottom surface for contacting a polishing pad during polishing and made of a first material, and an upper portion a backing ring made of a second, different material; and

a second chamber for containing a pressurized gas to provide a second independently controllable downward pressure on the retaining ring assembly that depends on gas pressure in the second chamber, wherein the second chamber is pressurizable independently of the first chamber and inflation of the second chamber urges the retaining ring downwardly.

2. The carrier head of claim 1, wherein the lower portion retaining ring is thicker than a the substrate to be polished.

3. The carrier head of claim 1, wherein the upper and lower portions retaining ring and backing ring are substantially annular in shape.

4. The carrier head of claim 1, wherein the first material is a plastic.

5. The carrier head of claim 1 4, wherein the first material is Delrin® plastic.

6. The carrier head of claim 1, wherein the second material is a metal.

7. The carrier head of claim 6, wherein the second material is aluminum.

8. The carrier head of claim 1, wherein the lower portion retaining ring is secured to the upper portion backing ring by screws.

9. The carrier head of claim 8, wherein the lower portion is secured to the upper portion by a key and key slot arrangement.

10. The carrier head of claim 1, wherein the upper portion backing ring is thicker than the lower portion retaining ring.

11. The carrier head of claim 1, further comprising a housing, and wherein the substrate backing member is movable relative to the housing.

12. The carrier head of claim 11, wherein the retaining ring assembly is movable relative to the housing.

13. A chemical mechanical polishing system, comprising:

a rotatable polishing pad;

a slurry supply to dispense a slurry onto the polishing pad; and

a carrier head having a substrate backing member with a mounting surface, a first chamber to provide a first downward pressure on the substrate backing member, a retaining ring assembly to maintain a substrate beneath the mounting surface during polishing, the retaining ring assembly vertically movable relative to the substrate backing member, the retaining ring assembly including a lower portion retaining ring having a bottom surface for contacting a polishing pad during polishing and made of a first material, and an upper portion backing ring made of a second, different material, and a second chamber for containing a pressurized gas to provide a second independently controllable downward pressure on the retaining ring assembly that depends on gas pressure in the second chamber, wherein the second chamber is pressurizable independently of the first chamber and inflation of the second chamber urges the retaining ring downwardly.

14. The carrier head of claim 1, wherein the retaining ring has a top surface and through-holes formed from the top surface to the bottom surface.

15. The carrier head of claim 14, wherein the backing ring has a bottom surface with holes formed therein.

16. The carrier head of claim 1, wherein the backing ring includes an outwardly extending flange.

17. The carrier head of claim 1, wherein the backing ring includes an inwardly extending flange.

18. The system of claim 13, wherein the first material is a plastic.

19. The system of claim 18, wherein the first material is Delrin® plastic.

20. The system of claim 13, wherein the second material is a metal.

21. The system of claim 20, wherein the second material is aluminum.

22. The system head of claim 13, wherein the retaining ring is secured to the backing ring by screws.

23. The carrier head of claim 1, wherein the second chamber is in an inflatable bladder.

24. The system of claim 13, wherein the second chamber is in an inflatable bladder.

25. The carrier head of claim 1, further comprising a support plate and a gas supply passage through the support plate to supply the pressurized gas to the second chamber.

26. The system of claim 13, wherein the carrier head has a support plate and a gas supply passage through the support plate to supply the pressurized gas to the second chamber.