Abrading – Work holder – Vacuum
Reexamination Certificate
2000-06-20
2002-09-03
Eley, Timothy V. (Department: 3723)
Abrading
Work holder
Vacuum
C451S288000, C451S289000
Reexamination Certificate
active
06443826
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 a polishing head, and to the retainer ring of a polishing head of such a chemical mechanical polishing apparatus.
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 apparatus will now be described in with reference to FIG.
1
. The conventional CMP apparatus includes a base
100
, polishing pads
2120
a,
210
b
and
210
c
installed on the base
100
, a load-cup
300
for loading/unloading wafers, and a head rotation unit
400
having a plurality of polishing heads
410
a,
410
b,
and
410
d
for holding the wafers and fixedly rotating the same on the polishing pads
210
a,
210
b
and
210
c.
In general, the CMP apparatus is provided with three polishing pads
210
a,
210
b
and
210
c
so that a plurality of wafers can be processed in a short time. Each of the polishing pads
210
a,
210
b
and
210
c
is closely fixed on a rotatable carousel (not shown). Pad conditioners
211
a,
211
b
and
211
c
for controlling the surface states of the polishing pads
210
a,
210
b
and
210
c
and slurry supplying arms
212
a,
212
b
and
212
c
for supplying slurry to the surfaces of the polishing pads
210
a,
210
b
and
210
c
are provided in the vicinity of the polishing pads
210
a,
210
b
and
210
c.
Also, the load-cup
300
includes a circular pedestal
310
on which the wafers are placed. The bottom surfaces of the polishing heads
410
a,
410
b,
410
c
and
410
d
and the top surface of the pedestal
310
are washed at the load-cup
300
, as will be described later in more detail.
The head rotation unit
400
includes four polishing heads
410
a,
410
b,
410
c
and
410
d
and four rotation shafts
420
a,
420
b,
420
c
and
420
d.
The polishing heads
410
a,
410
b,
410
c
and
410
d
hold wafers and apply a predetermined amount of pressure to the top surfaces of the polishing pads
210
a,
210
b,
210
c
and
210
d.
The rotation shafts
420
a,
420
b,
420
c
and
420
d
for rotating the polishing heads
410
a,
410
b,
410
c
and
410
d,
respectively, are mounted on a frame
401
of the head rotation unit
400
. A driving mechanism for rotating the rotation shafts
420
a,
420
b,
420
c
and
420
d
is provided within the frame
401
of the head rotation unit
400
. The head rotation unit
400
is supported by a rotary bearing
402
so as to be rotatable about the longitudinal axis of the rotary bearing
402
.
The process performed by the CMP apparatus having the above-described configuration will now be described with reference to
FIGS. 1 and 2
. First, a wafer
10
transferred to the load-cup
300
by a wafer transfer apparatus (not shown) is placed on the surface of the pedestal
310
of the load-cup
300
. Here, the wafer
10
is adhered by suction to the surface of the pedestal
310
so as not to move. Then, the wafer
10
is lifted by the pedestal
310
onto a polishing head
410
positioned above the pedestal
310
. The wafer
10
is adhered by suction to the polishing head
410
. The head rotation unit
400
is rotated to transfer the wafer
10
in such a state above the polishing pad
210
a
adjacent to the load-cup
300
. Then, the polishing head
410
is lowered to tightly press the wafer
10
onto the polishing pad
210
a.
At this time, the polishing pad
210
a and the wafer
10
are rotated in the same direction while slurry is supplied therebetween, whereby the wafer
10
is polished. The wafer
10
is then transferred sequentially to the other polishing pads
210
b
and
210
c
and then to the load-cup
300
where it is placed on the pedestal
310
. Thereafter, the wafer transfer apparatus transfers the wafer
10
placed on the pedestal
310
to a location outside the CMP apparatus.
Once the wafer
10
has been unloaded, the polishing head
410
descends towards the load-cup
300
. In such a state, deionized water is sprayed to wash the bottom surface of the polishing head
410
and the top surface of the pedestal
310
. When washing is completed, the polishing head
410
and the pedestal
310
are lifted again and a new wafer is transferred by the wafer transfer apparatus onto the pedestal
310
.
Referring to
FIGS. 3 and 4
, in order to wash the bottom surface of the polishing head
410
and the top surface of the pedestal
310
, the load cup
300
is provided with washing means comprising a first nozzle
331
and a second nozzle
332
for spraying deionized water within a washing basin
320
of the load-cup
300
. The first nozzle
331
is oriented so as to spray deionized water toward the top surface of the pedestal
310
and the second nozzle
332
is oriented so as to spray deionized water toward a membrane
411
installed on the bottom surface of the polishing head
410
. The membrane
411
allows a vacuum to act on the wafers and secure them to the polishing head
410
. Three sets each of the first and second nozzles
331
and
332
are installed at equal angular intervals around the circumference of the pedestal
310
. Three wafer aligners
340
for guiding wafers are installed within the washing basin
320
of the load-cup
300
at equal angular intervals around the circumference of the pedestal
310
to guide the wafers placed on the pedestal
310
into position.
The washing basin
320
is supported by a cylindrical support housing
350
, and a flexible hose
336
for supplying deionized water to the first and second nozzles
331
and
332
is installed within the support housing
350
. A washing fluid channel
337
for connecting the flexible hose
336
to the first and second nozzles
331
and
332
is provided within the washing basin
320
.
A plurality of spray orifices
311
for spraying deionized water upwards are provided in the pedestal
310
for the purpose of washing the membrane
411
. A lateral passageway
312
connected to the spray orifices
311
is provided in the pedestal
310
. The lateral passageway
312
is connected to a vertical passageway
313
formed inside a tubular pedestal column
315
supporting the pedestal
310
.
As described above, the load-cup
300
is responsible for washing the bottom surface of the polishing head
410
and the top surface of the pedestal
310
as well as for supporting wafers while they are loaded and unloaded onto and from the CMP apparatus. The washing step is very important in the CMP process. Contaminants such as slurry debris or polished silicon particles are unavoidably produced during the CMP process, and some of the contaminants may remain on the surface of the membrane
411
and/or the pedestal
310
. The contaminants remaining on the surface of the membrane
411
and/or the pedestal
310
can generate micro-scratches on the surface of a wafer if the contaminants are transferred thereto when the wafer is loaded in the course of polishing. The micro-scratches may cause def
Cha Hun
Kim Kyung-dae
Kim Min-gyu
Yang Yun-Sik
Eley Timothy V.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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