Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2000-03-13
2001-06-05
Powell, William (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C156S345420, C438S008000, C438S014000, C438S745000
Reexamination Certificate
active
06242353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer holding head to be used in an apparatus for polishing the surface of a semiconductor wafer in the process for manufacturing semiconductors and a wafer polishing apparatus, and a method for manufacturing wafers.
The specification of the present invention is based on the Japanese Patent Applications (Japanese Unexamined Patent Application Nos. 11-67583, 11-78688, 11-135017, 11-175950 and 11-251429), and the content of these Japanese applications are incorporated herein by references.
2. Description of the Related Art
Fine patterning of semiconductors have been developed in recent years as a result of development of highly integrated semiconductor devices. Since fine patterning of multilayer structures have been made easy and secure, it is particularly important to planarize the surface of semiconductor wafers to the best in the manufacturing process.
Finer planarization of the surface of the semiconductor wafers allows patterning precision to be improved besides making focusing of the exposed light easy when a photolithographic process is used for patterning. In addition, production of the semiconductor wafers can enjoy a low cost because the work efficiency is improved without providing complicated equipments for manufacturing the semiconductor wafers.
A chemical-mechanical polishing method (a CMP method) has been highlighted for this purpose since the method can polish the surface film with a high degree of planarity.
The surface of wafers are mechanically and chemically polished and planarized using a slurry of an abrasive such as an alkaline slurry containing SiO
2
, a neutral slurry containing SeO
2
, and an acidic slurry containing Al
2
O
3
(these are simply referred as a slurry hereinafter) in the CMP method. An example of the wafer polishing apparatus used for this method is shown in FIG.
31
.
In
FIG. 31
, the wafer polishing apparatus
200
is provided with a wafer holding head
201
holding a wafer to be polished, and a polishing pad
202
affixed on the entire surface of a disk shaped platen
203
. A plurality of the wafer holding heads
201
are attached at the lower portion of a carousel
204
as a head driving mechanism, which is rotatably held on a spindle
211
and rotates with a planetary motion on the polishing pad
202
. The center of the platen
203
may be provided eccentric to the center of the revolution of the wafer holding heads
201
.
The platen
203
is horizontally placed at the center of a base
205
, and is allowed to rotate around its axis line with a platen driving mechanism
206
provided in the base
205
. Guide posts
207
are provided at the side portions of the base
205
, while an upper mounting plate (a bridge)
209
for supporting a carousel driving mechanism
210
is disposed between the guide posts
207
. The carousel driving mechanism
210
serves for allowing the carousel
204
provided below the driving mechanism to rotate around the axis line.
Bridge supports
212
are disposed so as to protrude from the base
205
, and gap adjustable gap
213
are provided at the tips of the bridge supports
212
. Support plates
214
are disposed in opposed relation to the bridge supports
212
. These support plates
214
are fixed to the upper mounting plate
209
and protrude downward from the upper mounting plate
209
. The distance from the wafer holding head
201
to the polishing pad
202
are properly adjusted by allowing the bridge supports
212
to contact the support plates
214
. Wafers W are polished by allowing the wafers W held by the wafer holding head
201
to contact the surface of the polishing pad
202
, followed by allowing the carousel
204
and the platen
203
to rotate.
U.S. Pat. No. 5,205,082 discloses an improved polishing apparatus having a wafer holding head as shown in FIG.
32
. The wafer holding apparatus comprises a hollow head body
221
, a diaphragm
222
horizontally expanding in the head body
221
, and a carrier
224
fixed at the lower face of the diaphragm
222
. A retainer ring
232
is disposed at the outer circumference of the carrier
224
in a concentric relation with a slight gap between them, and the retainer ring
232
is also fixed to the diaphragm
222
. Further, stoppers
223
of the main head
221
are disposed at the outer circumference of the retainer ring
232
in a concentric relation with a slight gap. The carrier
224
and the retainer ring
232
are supported to the head body
221
in a floating manner as described above. An air chamber
226
is formed at upward of the diaphragm
222
by taking advantage of the head body
221
and the diaphragm
222
, wherein a compressed air is supplied to the air chamber from a compressed air source
230
through inside of a shaft
228
.
Polishing works are carried out by allowing a wafer W, fixed by being affixed to the carrier
224
via an insert S, to contact a polishing pad
202
. The contact pressure is made to be adjustable by changing the pressure of the air supplied to the air chamber
226
. The conventional wafer polishing apparatus as described above can even the contact pressure of the wafer W as described above with an advantage for improving uniformity of the polished face of the wafer. The diaphragm
222
to be used herein is usually made of an elastic material such as rubber and an extremely thin plate of a metal, which has a surface rigidity to an extent not to inhibit the movement of the carrier
224
along the axis line direction.
Meanwhile, a frictional force always generates between the wafer W and the polishing pad
202
. Consequently, a horizontal force and torque applied to the carrier
224
and the retainer ring
223
are received by the retainer ring
232
, the stopper
223
of the head body
221
, and the diaphragm
222
in the conventional wafer polishing apparatus as described above. The carrier
224
and the retainer ring
232
, and the retainer ring
232
and the stopper
223
, each being a circular contour, are fitted with each other with a slight gap as described above. Accordingly, although the horizontal force applied to the carrier
224
and the retainer ring
232
may be received by allowing the side wall face of the former to contact the side wall face of the latter, the torque around the axis line is received only by the diaphragm
222
.
The torque applied to the diaphragm
222
during the polishing work is unstable since it is caused by the frictional force, sometimes exceeding the strength limit of the diaphragm
222
to damage the diaphragm
222
made of a thin material. Since the frictional force caused by polishing, and the torque applied to the diaphragm
222
increase in response to the increase of the force for pressing the wafer W to the polishing pad
202
and increase of polishing rate, the pressing force and polishing rate is limited for preventing the diaphragm
222
from being damaged. Therefore, the polishing efficiency (polishing turns per unit time), precision of the polished face, and uniformity limit are determined by the limitations of the polishing conditions as described above.
Although increasing the strength of the diaphragm
222
by using a thicker material may be contemplated as a countermeasure for the foregoing problems, surface rigidity of the diaphragm will be inevitably increased to deteriorate trailing property of the carrier
224
along the axis line direction, thereby adversely affecting planarity and uniformity of the polished face.
When the wafer is polished using the wafer polishing apparatus
200
as hitherto described, whether the polished face of the wafer W has attained a desired conditions (detection of the end point of polishing, or end of the process) or not has been judged by observing, for example, fluctuations of the rotational power of the platen driving mechanism
206
. That is, when polishing of the wafer W is insufficient, the frictional force acting between the polishing pad
202
and the wafer W is not stabilized to cause fluctuation, while the frictional force is stabi
Kobayashi Tatsunori
Rikita Naoki
Tanaka Hiroshi
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Powell William
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