Abrading – Work holder
Reexamination Certificate
1999-12-21
2002-06-25
Hail, III, Joseph J. (Department: 3723)
Abrading
Work holder
C451S285000, C451S287000, C451S385000, C451S398000
Reexamination Certificate
active
06409585
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polishing apparatus and, more particularly, to an apparatus for holding an article to be polished, for example, a semiconductor wafer. With recent rapid progress in technology for fabricating high-integration semiconductor devices, circuit wiring patterns and interconnections have been becoming increasingly fine, with spaces between wiring patterns decreasing. As wiring spacing decreases to less than 0.5 microns, the depth of focus in circuit pattern formation in photolithography or the like becomes shallower. Accordingly, surfaces of semiconductor wafers on which circuit pattern images are to be formed by a stepper require a higher degree of surface flatness.
FIG. 1
shows a conventional polishing apparatus for making the surface of a semiconductor wafer flat. The apparatus includes a polishing table
4
provided with a polishing cloth
2
, for example, bonded thereto to form a polishing surface. The apparatus further includes a substrate holding apparatus
6
for holding a substrate W to be polished, for example a semiconductor wafer. An abrasive liquid Q is supplied between the polishing surface and a surface of the substrate W to be polished from an abrasive liquid supply pipe
8
, and the substrate W is pressed against the polishing surface under a predetermined pressure by the substrate holding apparatus
6
, while the polishing surface and the substrate W are caused to slide relative to each other to thereby effect polishing.
A typical substrate holding apparatus includes, as shown in
FIG. 2
, a substrate holder
10
and a drive shaft
12
connected to the substrate holder
10
at the lower end thereof through a universal joint
14
. The drive shaft
12
is adapted to transmit a rotational torque and a pressing force to the substrate holder
10
through the universal joint. The substrate holder
10
is also allowed to pivot about the universal joint
14
. The substrate holder
10
includes a substrate holding member
16
and a cover member
18
placed on and fastened to the substrate holding member
16
with a clearance or gap S being formed therebetween. The substrate holding member
16
is adapted to hold a substrate W against its lower surface under the influence of a vacuum generated in the substrate holder
10
and against the substrate. Over the substrate holding member
16
and the cover member
18
there is provided an annular pressure member
20
to impose a downward pressure thereon. The substrate holding member
16
is provided along its outer periphery with a guide ring
22
to cooperate with the substrate holding member to define a recess for receiving the wafer W.
The upper surface of the substrate holding member
16
has a center recess
24
and an annular step surface
26
surrounding the recess
24
. The cover member
18
has on its lower surface a centrally projecting portion
28
for engagement with the center recess
24
of the substrate holding member
16
and has along its outer periphery an annular flange
30
to be fastened to the step surface
26
of the substrate holding member
16
using bolts. The cover member
18
also has on its upper surface an annular projection
34
positioned in coaxial relation therewith, and a recess
32
surrounded by the annular projection
34
. A rubber sheet
37
is provided between a step surface
36
of the cover member
18
and the flange
30
to seal the gap S.
The gap S is fluidly connected to a fluid connection path
40
formed in the pressure member
20
, a fluid connection structure (not shown), and to the lower surface of the substrate holding member
16
through a plurality of holes
38
vertically extending through the substrate holding member
16
. The fluid connection path
40
is adapted to be selectively connected to a vacuum source and a pressurized fluid source (not shown) so that a vacuum and pressurized fluid are selectively applied to the lower surface of the substrate holding member
16
.
The drive shaft
12
has a drive member
68
with a flange portion
66
extending radially outwardly therefrom. The universal joint
14
is provided between the drive member
68
and the cover member
18
, and about which the substrate holder
10
tilts while a force is transmitted to the substrate holder
10
. The universal joint
14
includes a spherical bearing
70
and a rotation transmission device
72
for transmitting a rotational drive force to the substrate holder
10
from the drive shaft
12
.
The spherical bearing
70
includes a ball bearing
78
and hemispherical recesses
80
,
82
formed respectively at the center of a projected portion
76
formed on the lower surface of the drive member
68
and at the center of the recess
32
formed in the upper surface of the cover member
18
, with the hemispherical recesses slidably receiving the ball bearing
78
. The lowest point of the ball bearing
78
received in the hemispherical recess
82
is positioned below the step surface
26
of the cover member
18
. Due to the provision of the recess
24
in the substrate holding member
16
and the projected portion
28
of the cover member
18
, the thickness of the substrate holder
10
is able to be made smaller. Further, the positioning of the universal joint
14
in the recess
32
of the cover member
18
makes it possible to position the spherical bearing
70
close to the turntable
4
.
However, it is desired to provide the spherical bearing
70
at a position much more closer to the turntable
4
in order to decrease the amount of rotational moment around the spherical bearing
70
generated by a friction force acting between the substrate W and the turntable
4
and imposed on the substrate holder
10
during a polishing operation, to enable a stable polishing operation.
Since a magnitude of the rotational moment is proportional to a distance between the spherical bearing
70
and the substrate W, it may be possible to decrease the magnitude by increasing the depth of the recess
32
. However, this leads to a decrease in rigidity of the substrate holding member
16
with the result that the substrate holding member
16
becomes susceptible to deformation under the influence of a pressing force transmitted through the spherical bearing
70
and, as a result, it becomes difficult for a substrate to be appropriately flattened.
In particular, with an increase in size of wafers there is a concomitant increase in the amount of heat generated during a polishing operation, with the heat being transferred from the wafer to the wafer holder. Due to the large-size of the substrate holder, the mass thereof is greatly increased, however, a surface thereof from which heat is discharged is not greatly increased. As a result, the heat accumulated in the substrate holder has an adverse influence on the polishing operation.
The amount of heat generated at the center area of a substrate W is greater than that generated at the periphery of the same, and consequently a temperature gradient exists with respect to the substrate along its radial direction with the result that the heat transmitted to the substrate holding member
16
increases with a corresponding gradient. It is therefore necessary for the substrate holding member
16
to be resistant to and capable of readily discharging heat. One of the easiest ways of meeting this requirement is to decrease the mass of the substrate holding member
16
.
Further, it is necessary for the substrate holding member
16
to be periodically disassembled from the substrate holder
10
in order to renew a substrate holding pad provided on the lower surface of the substrate holding member and/or to clean the substrate holding member. It is desirable from an operator's point of view to provide a substrate holding member which is not too heavy. As substrates have have become larger in recent years, the weight of holders has become a significant problem.
This invention is made in the light of the above-stated circumstances.
SUMMARY OF THE INVENTION
An object of this invention is to provide a substrate holding
Berry Jr. Willie
Ebara Corporation
Hail III Joseph J.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Polishing apparatus and holder for holding an article to be... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polishing apparatus and holder for holding an article to be..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polishing apparatus and holder for holding an article to be... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2961036