Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1998-02-13
2001-05-01
Utech, Benjamin L. (Department: 1765)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C216S088000, C216S089000
Reexamination Certificate
active
06224712
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a polishing apparatus. More specifically, the invention relates to a polishing apparatus for planarizing roughness or unevenness on a surface of a semiconductor substrate or the like.
2. Description of the Related Art
In the recent years, in a fabrication process of a semiconductor, a polishing process has been used for planarization of roughness or unevenness of a semiconductor substrate or of step of element and wiring on the surface of the semiconductor substrate. The polishing process typically employs a system to selectively polish protruding portion for removal and whereby to achieve complete planarization.
Constructions of the conventional polishing apparatus typically employed have been disclosed in Japanese Unexamined Patent Publication No. Showa 59(1984)-187456, Japanese Unexamined Patent Publication No. Heisei 7(1995)-221053 and Japanese Unexamined Patent Publication No. Showa 58(1983)-22657. For example, as shown in FIG.
4
(
a
), the typical polishing apparatus is constructed with a polishing object holding means (hereinafter referred to as “fixing block”)
302
for holding a polishing object
101
via a buffering plate
303
, such as a semiconductor wafer or the like and rotating carrying the polishing object, and a rotary polishing table
106
. The buffering plate
303
is necessary for absorbing a load locally exerted on the polishing object
101
and whereby for improving uniformity of a polished surface. As the buffering plate, DF200 manufactured by Rodel, U.S.A. has been generally used. DF200 has a laminated structure of a polyurethane foamed layer and polyester sheet base material and has a compressibility factor (in accordance with a standard of JIS L-1096) of 33%. For instance, DF200 adapted for 6 inch wafer has an external diameter of 150 mm and a thickness of 0.6 mm. On the other hand, in order to prevent the polishing object
101
from loosing off the fixing block
302
, a retainer ring
304
having an internal diameter of 151 mm and a thickness of 7 mm is engaged on the outer periphery of the fixing block
304
.
On an upper surface of the rotary polishing table
106
having a rotary drive shaft
105
A, an abrasive cloth is bonded. The abrasive cloth is typically used with lapping over an abrasive cloth
107
(upper layer) and an abrasive cloth
108
(lower layer). As the abrasive cloth
107
, IC1000 manufactured by Rodel, is frequently used. The abrasive cloth
107
is formed by foaming and hardening urethane resin and is hard having a hardness factor of 95 in an Asker C hardness meter. On the other hand, as the abrasive cloth
108
, Suba400 manufactured by Rodel Nitta Company is frequently used, which is formed by impregnating polyurethane resin into a polyester fiber non-woven fabric and soft having a hardness factor of 61 in the Asker C hardness meter. Functions of the abrasive cloths
107
and
108
is that the abrasive cloth
107
serves for increasing flatness and the abrasive cloth
108
serves for absorbing camber or undulation of the surface of the polishing object
101
to improve uniformity of the polishing surface. On the other hand, a polishing fluid supply nozzle
109
is provided at the center portion above the abrasive cloth
107
.
Next, operation of the foregoing polishing apparatus under typical polishing condition will be discussed. When a polishing fluid
110
containing solid component, such as silicon oxide or the like is supplied in a rate of 200 cc/min on the abrasive cloth
107
rotating at a rotation speed of 30 r.p.m., the polishing fluid
110
propagates along the upper surface of the abrasive cloth
107
from the center portion to the end portion. Under this condition, the polishing object
101
held on the fixing block
302
is fitted on the abrasive cloth
107
under pressure. Then, polishing is performed with applying a 7 psi (not shown) of load on the fixing block
302
. At this time, in order to certainly maintain uniformity of in-plane polishing speed of the polishing object
101
, the fixing block
302
is also rotated on own axis at a speed of 30 r.p.m.
FIG. 4C
is a chart showing a polishing speed in a direction including a diameter extending cross the center of the polishing object
101
polished by an apparatus shown in FIG.
4
A and extending perpendicular to a polishing surface. The shown profile is the same in the profile of any diametrical direction taking the center of the polishing object
101
as an origin. Since
FIG. 4C
is a bilateral symmetric profile with respect to the origin, discussion will be given for the polishing speed of the polishing object
101
from an edge in the plus direction to the origin.
At the edge portion (a region of +73 to +75 mm) of the polishing object
101
, the polishing speed is quite high. Conversely, in a region of +60 to +73 mm, the polishing speed is low, and has a minimum point in a region of +71 to +73 mm. In a region of 0 to +60 mm, the polishing speed is uniform. A tendency of the polishing speed at the end portion of the polishing object
101
is caused due to difference of pressure exerted on the polishing object
101
from the abrasive cloth
107
. Since the abrasive cloth
107
in the upper layer is hard but the abrasive cloth
108
in the lower layer is soft, the abrasive cloths
107
and
108
mating with the edge portion of the polishing object
101
is locally deformed.
FIG. 5B
shows a result of measurement of a pressure exerted on the edge portion of the polishing object
101
by means of a pressure sensor. In the region of +73 to +75 mm, due to large deformation of the abrasive cloths
107
and
108
, an excessively high pressure is exerted locally. Conversely, in the region of +60 to +73 mm, the pressure is gradually released and lowered. Then, in the region of 0 to +60 mm, the pressure is uniformly exerted. The pressure distribution in respective of these regions correspond to distribution of the polishing speed.
In order to improve non-uniformity of the polishing speed, there is a method to use Suba800 manufactured by Rodel Nitta Company, which is formed of the same material as Suba400 but having higher hardness. Suba800 has a hardness factor of 82 in Asker C hardness meter.
FIG. 6A
is an enlarged section of the edge portion in the case where Suba800 is used as the abrasive cloth
108
in the apparatus of FIG.
4
A. While it is similar even in the case using SuBa400, since the buffer plate
303
is used, displacement is caused between the buffering plate bonding surface of the fixing block
302
and the buffering plate
303
is caused to form a gap portion
316
between the end portion of the buffering plate
303
and the retainer ring
304
. The enlarged section shown in
FIG. 6A
shows an example causing plus side displacement of the buffering plate
303
, in which the plus side edge of the polishing object
101
is located completely above the buffering plate
303
.
Discussion for the pressure distribution and the polishing speed at the plus side edge portion will be given with reference to FIG.
6
B. In this case, Suba800 as the abrasive cloth
108
of the lower layer is hard, local deformation amount of the abrasive cloths
107
and
108
at the edge portion of the polishing object
101
is small even when the polishing object
101
is depressed onto the abrasive cloths
107
and
108
. Therefore, in the region of +73 to +75 mm of
FIG. 6B
, excessive pressure may be exerted by shifting of the polishing object
101
during polishing. Thus, the pressure exerted from the abrasive cloth
107
is equivalent to the case where Suba400 is used. In the region of +60 to +73 mm, since local deformation amount is small, the pressure to be exerted on the polishing object
101
becomes uniform. Accordingly, as shown in
FIG. 7
, in a region of +60 to 73 mm, the polishing speed becomes uniform to make the uniform region wider than that in the case where Suba400 is used.
It should
Brown Charlotte A.
Foley & Lardner
NEC Corporation
Utech Benjamin L.
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