Bearing substitute for wafer polishing arm

Details Bearing substitute for wafer polishing arm Bearing substitute for wafer polishing arm

1999-10-15

2001-06-26

Banks, Derris H. (Department: 3723)

Abrading

Abrading process

Glass or stone abrading

C451S287000, C451S285000, C384S549000

Reexamination Certificate

active

06250991

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to fabrication of semiconductor devices, and in particular, to a method and apparatus for polishing semiconductor wafers.
DESCRIPTION OF THE RELATED ART
Chemical mechanical planarization (“CMP”) processes remove material from the surface of a semiconductor wafer in the production of ultra-high density integrated circuits. In a typical CMP process, a wafer is pressed against a polishing pad in the presence of a slurry under controlled chemical, pressure, velocity, and temperature conditions. The slurry solution generally contains small, abrasive particles that abrade the surface of the wafer, and chemicals that etch and/or oxidize the surface of the wafer. The polishing pad is generally a planar pad made from a relatively soft, porous material such as polyurethane. Thus, when the pad and/or the wafer moves with respect to the other, material is removed from the surface of the wafer by the abrasive particles (mechanical removal) and by the chemicals (chemical removal) in the slurry.
FIGS. 1 and 2
show a conventional polishing apparatus
10
. The apparatus
10
includes a polishing pad
20
and three polishing stations
30
,
40
,
50
for polishing semiconductor wafers
60
. Preferably, the polishing pad
20
spins counter-clockwise to accomplish the polishing of the wafers
60
, as shown by directional arrow A in FIG.
2
. Each station
30
,
40
,
50
includes a polishing arm
31
,
41
,
51
which holds the wafers
60
during the polishing process. Each polishing arm
31
,
41
,
51
includes a U-shaped member for holding vacuum chucks
32
,
42
,
52
. Each polishing arm
31
,
41
,
51
includes one such vacuum chuck
32
,
42
,
52
. The vacuum chucks
32
,
42
,
52
are coupled to U-shaped members through metal bearings
35
,
45
,
55
. The bearings
35
,
45
,
55
allow the vacuum chucks
32
,
42
,
52
to rotate with respect to the respective polishing arms
31
,
41
,
51
. The vacuum chucks
32
,
42
,
52
operate to hold the wafers
60
during the polishing process. Each of the vacuum chucks
32
,
42
,
52
includes an upper end
33
,
43
,
53
which may be coupled to a vacuum device (not shown) to provide a vacuum to the vacuum chucks. The polishing apparatus
10
also includes a slurry dispenser
70
which produces slurry which is dispensed onto a top surface
21
of the polishing pad
20
.
A problem associated with the conventional apparatus
10
discussed above is that the slurry dispensed from slurry dispenser
70
often becomes disposed in the metal bearings
35
,
45
,
55
which couple the vacuum chucks
32
,
42
,
52
to the polishing arms
31
,
41
,
51
. The slurry often causes the metal bearings
35
,
45
,
55
to “lock up”, thereby preventing the free rotation of the chucks
32
,
42
,
52
about the polishing arms
31
,
41
,
51
. The locking up of the metal bearings
35
,
45
,
55
results in uneven polishing of the wafers
60
attached to the polishing arms
31
,
41
,
51
.
Therefore, there is currently a need for an improved polishing apparatus which substantially reduces the possibility of lock up of the bearings of the polishing apparatus.
SUMMARY OF THE INVENTION
The present invention is an apparatus and method for polishing a workpiece including a polishing pad, and at least one polishing arm for holding a workpiece to be polished on the polishing pad, the polishing arm including at least one plastic bearing.
The above and other advantages and features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention which is provided in connection with the accompanying drawings.


REFERENCES:
patent: 4934107 (1990-06-01), MacKay, Jr.
patent: 4991356 (1991-02-01), Ono
patent: 5001869 (1991-03-01), Hutchins
patent: 5085012 (1992-02-01), Hutchins
patent: 5649849 (1997-07-01), Pileri et al.

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