Wafer polishing apparatus and process

Details Wafer polishing apparatus and process Wafer polishing apparatus and process

1999-10-15

2002-01-22

Banks, Derris H. (Department: 3723)

Abrading

Accessory

Tool cleaner

C451S287000

Reexamination Certificate

active

06340327

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 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. As can be clearly seen in
FIG. 1
, in the conventional polishing apparatus
10
, the polishing stations
30
,
40
each hold wafers
60
, while the polishing station
50
is left empty (i.e. no wafer
60
is polished there). 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 gathers in clumps on the top surface
21
of the polishing pad
20
. Since the slurry is dispensed from the slurry dispenser
70
in droplet form, when the droplets hit the rotating polishing pad
20
they stay in droplet form and do not spread out. This clumping of the slurry results in uneven polishing of the wafers
60
. In particular, when a droplet of slurry contacts a wafer
60
, the initial area of the wafer that the slurry contacts is polished down further than the other areas of the wafer.
Therefore, there is currently a need for an improved polishing apparatus which provides an even distribution of slurry.
SUMMARY OF THE INVENTION
The present invention is an apparatus and method for polishing a workpiece including, a polishing pad; at least one polishing arm for holding a workpiece to be polished on the polishing pad; at least one conditioning arm for conditioning the polishing pad; and, a slurry-producing device, the slurry-producing device being disposed between the at least one polishing arm and the at least one conditioning arm so that slurry dispensed by the slurry-producing device contacts the at least one conditioning pad before it contacts the at least one polishing pad.
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: 5645682 (1997-07-01), Skrovan
patent: 5651725 (1997-07-01), Kikuta et al.
patent: 5707274 (1998-01-01), Kim et al.
patent: 5785585 (1998-07-01), Manfredi et al.
patent: 6039635 (2000-03-01), Mitsuhashi et al.
patent: 6135868 (2000-10-01), Brown et al.
patent: 6149508 (2000-11-01), Vanell et al.
2 sample pages from Logitech Ltd. catalog, date unknown.

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