Abrading – Machine – Combined
Reexamination Certificate
2000-06-15
2002-06-11
Rose, Robert A. (Department: 3723)
Abrading
Machine
Combined
C451S288000, C451S041000
Reexamination Certificate
active
06402598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemical mechanical polishing apparatus used in manufacturing a semiconductor device. More particularly, the present invention relates to the polishing head of a chemical mechanical polishing apparatus, and to a method of washing contaminants off of the polishing head.
2. Description of the Related Art
Increasing the integration of semiconductor devices has required sequentially depositing multiple layers on a wafer. Accordingly, the semiconductor manufacturing process must include steps for planarizing each layer formed on the semiconductor wafer. Chemical mechanical polishing (CMP) is a typical process used for this purpose. In fact, CMP is well-suited for use in connection with large-diameter wafers because CMP produces excellent uniformity in planarizing wide areas in addition to narrow ones.
The CMP process makes use of mechanical friction and a chemical agent for finely polishing a wafer surface, such as that comprising tungsten or an oxide. In the mechanical aspect of such polishing, a wafer is placed on a rotating polishing pad and is rotated while a predetermined is load applied thereto, whereby the wafer surface is polished by the friction created between the polishing pad and the wafer surface. In the chemical aspect of such polishing, the wafer surface is polished by a chemical polishing agent, referred to as slurry, supplied between the polishing pad and the wafer.
A conventional CMP system will now be described with reference to
FIGS. 1-7
.
As shown in
FIG. 1
, the conventional CMP system includes a CMP apparatus
100
and a wafer transfer apparatus
170
adjacent to the CMP apparatus
100
.
The CMP apparatus
100
includes a base
110
, several polishing pads
120
installed on the base
110
, a load-cup
130
for loading/unloading wafers
10
, and a head rotation unit
140
having a plurality of polishing heads for holding the wafers
10
tight and rotating the same on the polishing pads
120
. A protective cover
150
is installed on the upper portion of the base
110
. The protective cover
150
surrounds and thereby protects the polishing pads
120
, the load-cup
130
and the head rotation unit
140
. The protective cover
150
is also made of a transparent material which allows the polishing pad
120
s
, the load-cup
130
and the head rotation unit
140
to be viewed from outside the cover. An outlet
151
through which dust or other contaminants present inside the protective cover
150
are exhausted is provided on the protective cover
150
and is connected to an exhaust pump (not shown) through an exhaust pipe
152
.
The wafer transfer apparatus
170
loads the wafers
10
into the CMP apparatus
100
and transfers the polished wafers
10
from one processing station to the next. The wafer transfer apparatus
170
includes a case
171
in which the wafers
10
are situated, a holder
174
for grabbing the wafers
10
from the case
171
and loading the same on the load-cup
130
of the CMP apparatus
100
, an elevating arm for elevating the holder
174
and rotating the same, and a track
172
for supporting the elevating arm
173
and reciprocating the same in a predetermined direction.
The protective cover
150
also forms a wafer entrance
153
in one side thereof. The wafers
10
are loaded onto and are unloaded from the load-cup
130
by the wafer transfer apparatus
170
via the wafer entrance
153
in the cover
150
.
Referring now to
FIG. 2
, a plurality of polishing pads, generally three polishing pads
120
a
,
120
b
and
120
c
, are installed on the base
110
so that a plurality of wafers can be processed at a time. The polishing pads
120
a
,
120
b
and
120
c
are fixed to a rotatable carousel (not shown). Pad conditioners
121
a
,
121
b
and
121
c
for adjusting the surface states of the polishing pads
120
a
,
120
b
and
120
c
, and slurry supplying arms
122
a
,
122
b
and
122
c
for supplying slurry to the surfaces of the polishing pads
120
a
,
120
b
and
120
c
, are disposed adjacent the polishing pads
120
a
,
120
b
and
120
c.
The head rotation unit
140
includes four polishing heads
141
a
,
141
b,
141
c
and
141
d
and four rotation shafts
142
a
,
142
b
,
142
c
and
142
d
. The polishing heads
141
a
,
141
b
,
141
c
and
141
d
hold wafers against the polishing pads so that a predetermined pressure is exerted thereon while the wafers are being polished. The rotation shafts
142
a
,
142
b
,
142
c
and
142
d
for rotating the polishing heads
141
a
,
141
b
,
141
c
and
141
d
, respectively, are mounted on a frame
143
of the head rotation unit
140
. A driving mechanism for rotating the rotation shafts
142
a
,
142
b
,
142
c
and
142
d
is provided within the frame
143
of the head rotation unit
140
. The head rotation unit
140
is supported by a rotary bearing
144
so as to be rotatable about the longitudinal axis of the bearing
144
.
Furthermore, the load-cup
130
includes a circular pedestal
131
which supports the wafers. As will be described later, the polishing heads
141
a
,
141
b
,
141
c
and
141
d
are washed at and by the load-cup
130
.
The operation of the CMP apparatus having the structure described above will now be described with reference to
FIGS. 2 and 3
. First, the wafer
10
transferred to the load-cup
130
by the wafer transfer apparatus
170
is placed on the surface of the pedestal
131
of the load-cup
130
. There, the wafer
10
is vacuum-chucked on the surface of the pedestal
131
so as to be fixed in place. Then, the wafer
10
is lifted using the pedestal
131
and is thereby transferred to a polishing head
141
positioned above the pedestal
131
. The wafer is then vacuum-chucked to the polishing head
141
, and the head rotation unit
140
is rotated to transfer the wafer to a position above the polishing pad
120
a
adjacent to the load-cup
130
. Then, the polishing head
141
is lowered so that the wafer
10
is pressed tightly against the polishing pad
120
a
. The wafer is polished in this state while slurry is supplied between the wafer and the polishing pad
120
a
. In this case, the polishing pad
120
a
and the wafer
10
rotate in the same direction, typically counter-clockwise. Each wafer
10
is transferred sequentially among the three polishing pads
120
a
,
120
b
and
120
c
and then to the load-cup
130
where the wafer is placed on the pedestal
131
. Thereafter, the wafer transfer apparatus
170
transfers the wafer
10
placed on the pedestal
131
to the outside of the CMP apparatus
100
.
Once the wafer
10
has been unloaded, the polishing head
141
is lowered towards the load-cup
130
. In such a state, deionized water is sprayed to wash the bottom of the polishing head
141
and the pedestal
131
. When the washing is completed, the polishing head
141
and the pedestal
131
are raised and a new wafer is transferred by the wafer transfer apparatus
170
to the pedestal
131
.
Next, as shown in
FIGS. 4 and 5
, a first nozzle
135
and a second nozzle
136
for spraying deionized water are provided in a washing basin
132
of the load-cup
130
. The first nozzle
135
is oriented so as to spray deionized water toward the top surface of the pedestal
131
, and the second nozzle
136
is oriented so as to spray deionized water toward a membrane
1411
installed at the bottom of the polishing head
141
. The membrane
1411
allows a vacuum to be exerted on the wafer held by the polishing head. Three sets of the first and second nozzles
135
and
136
are spaced from each other at equal angular intervals about the pedestal
131
. Three wafer aligners
133
for guiding a wafer into position are installed within the washing basin
132
of the load-cup
130
. The wafer aligners
133
are also spaced form one another at equal angular intervals abut the circumference of the pedestal
131
.
The washing basin
132
is supported by a cylindrical support housing
134
. A flexible hose
1352
for supplying deionized water to the first and second
Ahn Yo-han
Choi Jae-won
Kim Tae-ho
Lee Byung moo
Rose Robert A.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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