Abrading – Machine – Rotary tool
Reexamination Certificate
2002-01-15
2004-07-13
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S460000, C451S411000
Reexamination Certificate
active
06761624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a chemical mechanical polishing (CMP) apparatus. In particular, the present invention relates to a pusher for the CMP apparatus.
2. Description of the Related Art
A process commonly used in fabrication of integrated circuits to create a planar topography is chemical mechanical polishing (CMP). This process involves chemically removing a surface while also mechanically grinding or polishing it. The combined action of surface chemical reaction and mechanical polishing allows for a controlled, layer by layer removal of a desired material from the wafer surface, resulting in a preferential removal of protruding surface topography and a planarized wafer surface.
FIG. 1
schematically illustrates a conventional CMP apparatus
100
with a platen
110
, a pusher
120
, and a wafer carrier
150
.
The pusher
120
, as shown in
FIG. 3
, comprises a base disk
134
supported by a support
138
, a plurality of guiding structures
122
at the rim of the base disk
134
, and a plurality of brackets between the guiding structures
122
. The support
138
can lower or raise the pusher
120
. Each guiding structure
122
has a shell
124
with an opening
126
(as shown in
FIG. 4
a
), a pin
128
moving through the opening
126
, and an elastic device (not shown), such as a spring, for raising and lowering the pin
128
. Each pin
128
is a metal bar. The upper part of the pin
128
(as shown in
FIG. 4
b
) is tapered so that the wafer can slide down and be guided to deposit on the brackets
136
.
One end of the shell
124
is the opening
126
, and the other end is closed. Two fins
130
are disposed at the shell
124
and near the other end of the shell
124
. A hole
132
is positioned in each fin
130
so as to connect the guiding structure
122
and the base disk
134
.
As shown in
FIG. 4
c
, each pin
128
is put inside the corresponding shell
124
and protrudes from the opening
126
. The pin
128
can be lowered and raised by the elastic device. When the pin
128
is pushed, it can be lowered in the shell
124
. The opening
126
is rectangular with keyholed corners, as shown in
FIG. 4
d.
FIG.
2
(
a
) and (
b
) show the top view and the side view of the CMP apparatus
100
respectively. The wafer carrier
150
includes a guide ring
152
, a top ring
154
and a backing ring
156
. The top ring
154
is supported by the backing ring
156
, and the guide ring
152
is positioned on the outer periphery of the top ring
154
.
A wafer
102
is deposited on the pusher
120
as following. The wafer
102
is deposited on the top of the brackets
136
guided by pins
128
of the guiding structure
122
. The pusher
120
is pushed by the support
138
to the wafer carrier
150
and contacts the guide ring
152
of the wafer carrier
150
. The pins
128
are lowered into shells
124
so that the wafer
102
can be drawn by vacuum into the space constituted by the guide ring
152
and the backing ring
156
. The wafer
102
held by the wafer carrier
150
is transferred to the platen
110
.
A polyester polishing pad
112
is positioned on the platen
110
, and a slurry from a nozzle
160
is positioned on the polishing pad
112
.
The wafer
102
held by the wafer carrier
150
faces downward against the polishing pad
102
, and then the platen
110
and the wafer carrier
150
move relative to one another, whereby the surface of the wafer
102
is polished. After polishing, the wafer carrier
150
carries the wafer
102
out of the platen
110
and onto the pusher
120
. The pusher
120
is then raised, and the pins
128
of the guiding structures
122
contact the guide ring
152
of the wafer carrier
150
. The pins
128
are lowered into shells
124
so that the wafer
102
can be deposited on the top of the brackets
136
. The pusher
120
is then lowered.
After polishing, the wafer
102
is washed. However, some slurry may remain on the wafer
102
. When the wafer
102
is positioned on the brackets
136
guided by the pins
128
, the remaining slurry may flow along the pins
128
into the gap between the pins
128
and the shells
124
. If the slurry is dry, some particles are formed at the gap obstructing the movement of the pins
128
. The pins
128
cannot guide the wafer
102
normally, and may stick inside the shells
124
. In this situation, the wafer
102
cannot be positioned exactly on the top of brackets
136
and parts of the wafer
102
may slide out of the pusher
120
. For this reason, when transferring the wafer
102
to the wafer carrier
150
, although the wafer
102
can be carried by the wafer carrier
150
, the wafer
102
cannot be positioned exactly on the space constituted by the guiding ring
152
, and the backing ring
156
, as shown in
FIG. 5. A
part of the wafer
102
is outside the wafer carrier
150
. Moreover, the wafer
102
may become deformed due to a vacuum force. When the wafer
102
is polished, a force is applied in the downward vertical direction against wafer
102
and presses the wafer
102
against the polishing pad
112
. However, in this situation, the wafer
102
may be broken, and the fragments damage the polishing pad
112
and the backing ring
156
. It wastes time and money to shut down the CMP apparatus
100
to clean it.
SUMMARY OF THE INVENTION
The present invention provides a chemical mechanical polishing (CMP) apparatus, comprising: a platen with a polishing pad thereon, a wafer carrier, and a pusher. The wafer carrier holds a wafer on the polishing pad, and can move on to and off of the polishing pad. The pusher has a base disk and at least two guiding structures at the rim of the base disk. Each guiding structure has a shell with an opening, an elastic device and a pin moving through the opening, wherein the opening is non-linear.
For the CMP apparatus, a plurality of brackets are disposed between the guiding structures. The opening is composed of two pairs of sides, and at least one pair of sides is concave or convex.
REFERENCES:
patent: 5329732 (1994-07-01), Karlsrud et al.
patent: 5934984 (1999-08-01), Togawa et al.
patent: 6358126 (2002-03-01), Jackson et al.
Tsai Hsin-Chuan
Wang Shan-Chang
Ladas & Parry
Nanya Technology Corporation
Rose Robert A.
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