Stacked polish pad

Details Stacked polish pad Stacked polish pad

2000-05-04

2001-07-31

Eley, Timothy V. (Department: 3723)

Abrading

Flexible-member tool, per se

Laminate

C451S287000

Reexamination Certificate

active

06267659

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to chemical-mechanical polishing of semiconductor wafers and, more particularly, to a stacked wafer polishing pad having variable hardness.
BACKGROUND OF THE INVENTION
Chemical-mechanical polishing (CMP) is performed in the processing of semiconductor wafers and/or chips on commercially available polishers. The standard CMP polisher has a polishing table carrying a circular polishing pad and a rotating carrier for holding the wafer. A slurry is used on the polishing pad.
Ideally, a CMP polisher delivers a global uniform, as well as locally planarized wafer. However, global uniformity on a wafer-to-wafer basis is difficult to achieve. Current pad designs include stacked pads in which an upper hard pad is stacked on a soft sub-pad which is disposed on a polishing platen associated with the polishing table. The hard pad may be, for example, an IC 1000 pad while the soft pad may be, for example, a Suba 4 pad. These stacked pads have functioned to improve polish uniformity. However, the stacked pads require the disposal of both pads after a certain number of wafers have been polished on the upper pad or if a sub-pad of differing compressibility is desired. It is known to replace the soft pad with a semi-permanent silicon pad of the same or similar compressibility as the Suba 4 soft pad. However, it is desirable to use a sub-pad of a material whose rigidity and pliability could be varied ex situ or in situ to achieve variable polish pad hardness.
SUMMARY OF THE INVENTION
In accordance with the invention the above desires are satisfied with a sub-pad whose rigidity and pliability is variable to achieve variable polish pad hardness.
Broadly, there is disclosed herein a polishing pad assembly for use in a chemical-mechanical polishing apparatus having a polishing platen. The polishing pad assembly includes a first pad disposed on the platen. The first pad is variably adaptable to vary hardness. Control means are operatively associated with the first pad for varying hardness of the first pad. A second pad is disposed on the first pad.
It is a feature of the invention that the first pad comprises a sealable enclosure with a flexible outer skin and partially filled with a porous material.
It is another feature of the invention that the control means comprises means for injecting a fluid into and for removing the fluid from the enclosure. The first pad has a hardness which is variable according to an amount of fluid in the enclosure.
It is still another feature of the invention that the injecting means comprises the platen being perforated and being operatively connected to a fluid delivery supply.
It is still another feature of the invention that the fluid delivery is radially variable across the first pad to radially vary hardness of the first pad.
In accordance with an alternative embodiment of the invention it is a feature of the invention that the first pad comprises a two-part laminated polymer cured to form a hard pad.
It is another feature of the invention that the control means comprises means for heating the platen to form a pliable first pad outer surface.
It is still another feature of the invention that the heating is radially variable across the first pad to radially vary hardness of the first pad.
Further features and advantages of the invention will be readily apparent from the specification and from the drawings.


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