Abrading – Machine – Rotary tool
Reexamination Certificate
1999-02-17
2001-05-22
Larson, Lowell A. (Department: 3725)
Abrading
Machine
Rotary tool
C451S056000
Reexamination Certificate
active
06234884
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer polishing device and, more particularly, to a wafer polishing device for removing a surface unevenness of a semiconductor substrate.
2. Description of the Related Art
FIG. 4
shows a conventional wafer polishing device. The polishing device includes a rotatable polishing table
1
, a polishing pad
4
provided on the polishing table
1
and a carrier head
8
for supporting a semiconductor substrate
2
, that is, a wafer
2
, to be polished. The polishing apparatus further includes a pressing mechanism
9
for pressing the wafer
2
together with the carrier head
8
to the polishing pad
4
and a spindle
10
for rotating the wafer
2
with the carrier head
8
on the polishing pad
4
. A polishing slurry
5
is supplied onto a surface of the polishing pad
4
by means of a pump, etc from a polishing slurry nozzle
11
.
The wafer
2
is pressed by the pressing mechanism
9
to the rotating polishing pad
4
through the spindle
10
and the carrier head
8
so that the wafer
2
is polished by the polishing pad
4
. For example, the wafer contains a plurality of semiconductor layers, which are polished by CMP (chemical mechanical polishing) method to flatten a surface of the wafer including them.
The wafer polishing device further includes a retainer ring
3
for holding the wafer on the polishing pad
4
. The retainer ring
3
may take in the form of non-contact type retainer shown in
FIG. 5
or in the form of contact type retainer
3
shown in FIG.
6
. The retainer ring
3
shown in
FIG. 5
is used only for retaining the wafer
2
in a predetermined position on the polishing pad
4
without contacting with a surface of the polishing pad
4
so that the slurry
5
can be easily supplied into between the polishing pad
4
and the wafer
2
. However, when such retainer ring is used, load is concentrated between an edge portion of the wafer
2
and the polishing pad
4
. Therefore, the edge portion of the wafer
2
is polished at higher speed than the surface except the edge portion of the wafer
2
so that the peripheral portion of the wafer
2
is abnormally polished as shown in FIG.
7
. Therefore, the flatness of the outer peripheral portion of the wafer
2
is degraded as shown in
FIG. 9
, resulting in the yield of wafer being reduced.
In order to solve the problem caused by the non-contact type retainer ring shown in
FIG. 5
, the retainer ring
3
shown in
FIG. 6
is used. This retainer ring
3
is always in contact with the surface of the polishing pad
4
. According to the retainer ring
3
shown in
FIG. 6
, the load to be applied concentrically between the polishing pad
4
and the wafer
2
is dispersed and the load point is moved outward of the retainer ring
3
. Therefore, the polishing speed profile at the edge portion of the wafer is improved as shown in FIG.
8
.
However, there is a problem when the retainer ring
3
shown in
FIG. 6
is used. That is, in the wafer polishing device using the retainer ring
3
of the contact type, the supply of slurry into between the wafer
2
and the polishing pad
4
becomes short since the polishing pad
4
is in contact with the retainer ring
3
. Further, since the slurry
5
already supplied tends to stay within the retainer ring
3
, the supply of new slurry into the retainer ring
3
is blocked, causing the polishing speed for the surface of the wafer
2
to be varied. Therefore, the polishing profile in the edge portion of the wafer is varied.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor substrate polishing device capable of realizing a good surface flatness of semiconductor substrate and improving the yield of semiconductor substrate to thereby improve the productivity of semiconductor substrate.
As a result of investigations conducted by the inventor of this invention in order to achieve the above objects, it has been found that the abnormal polishing of the edge portion of the wafer is caused mainly by a deformation of a surface of the polishing pad at an upstream side in a rotating direction of the polishing table and that such abnormal polishing can be improved enough even without providing the contact type retainer ring in a downstream side of the wafer. The term “upstream side” means a region in which the polishing table at a cross point of a rotation line indicative of the rotating direction of the polishing table and the peripheral edge of the wafer moves inward of the wafer. The term “downstream side” means a region in which the polishing table at a cross point of the rotation line and the peripheral edge of the wafer moves outward of the wafer.
The wafer polishing device according to the present invention comprises: a rotatable polishing table; a polishing pad provided on the polishing table for polishing a wafer; a polishing slurry supply unit for supplying a polishing slurry onto a surface of the polishing pad; and a polishing pad surface mending unit for regulating a surface condition of the polishing pad while being in slide contact with the polishing pad, the polishing pad surface mending unit positioned on an upstream side of the wafer in a rotating direction of the polishing table.
In the wafer polishing device according to the present invention, the polishing pad surface mending unit is arranged in the region of the upstream side of the wafer and there is no contact ring provided in the region of the downstream side of the wafer. Therefore, the flow of slurry is improved and the uniformity of polishing speed of the wafer can be improved.
That is, the polishing pad surface mending unit functions to shift a rebound deformation of the polishing pad from the wafer edge side of the mending unit toward the edge side of the mending unit opposite to the wafer edge side of the mending unit. Further, since the polishing pad surface mending unit is positioned at the upstream side, the wafer is entirely not covered by the polishing pad surface mending unit, so that the flow of polishing slurry is not blocked by the polishing pad surface mending unit.
In the wafer polishing device of the present invention, it is preferable that the polishing pad surface mending unit surrounds almost all of the peripheral area of the wafer on the upstream side.
Further, in the wafer polishing device of the present invention, it is preferable that a peripheral area of the wafer surrounded by the polishing pad surface mending unit is about 30% to 50% of a whole periphery of the wafer.
When the peripheral area of the wafer surrounded by the polishing pad surface mending unit is smaller than about 30% of the whole periphery of the wafer, the function of the polishing pad surface mending unit to dispersing the local load which applied to the periphery of the wafer becomes insufficient, so that the surface condition at the peripheral portion of the wafer is deformed.
When the peripheral area of the wafer surrounded by the polishing pad surface mending unit exceeds about 50% of the whole periphery of the wafer, the wafer is covered by the polishing pad surface mending unit even in the downstream side of the wafer in the rotating direction of the polishing table, so that the flow of slurry is blocked.
Further, in the wafer polishing device of the present invention, it is preferable that the polishing slurry supply unit is set at a peripheral region of the wafer which is not surrounded by the polishing pad surface mending unit. The supply of polishing slurry is not disturbed by the polishing pad surface mending unit.
In this case, it is enough that the polishing slurry supply unit supplies the polishing slurry to an area which is in the vicinity of a border portion between the peripheral area of the wafer surrounded by the polishing pad surface mending unit and the other peripheral area of the wafer and where the wafer moves from the other peripheral area toward the peripheral area of the wafer surrounded by the polishing pad surface mending unit. In such case, a flow of slurry is formed by the mo
Foley & Lardner
Larson Lowell A.
NEC Corporation
LandOfFree
Semiconductor wafer polishing device for removing a surface... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor wafer polishing device for removing a surface..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor wafer polishing device for removing a surface... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2545130