Abrading – Machine – Rotary tool
Reexamination Certificate
1999-04-12
2001-08-21
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S285000, C451S288000, C451S397000
Reexamination Certificate
active
06277008
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polishing apparatus used in, e.g., chemical-mechanical polishing (CMP).
A technique for planarizing a substrate surface by polishing has been employed in many fields including the semiconductor substrate fabrication process. In recent years, CMP for planarizing the unevenness of a surface, e.g., the unevenness of the surface of an interlevel insulating film, formed during the fabrication by polishing is used in a process of fabricating devices on a semiconductor substrate.
In CMP, hard polishing cloth made of a material such as foamed polyurethane, different from relatively soft polishing cloth comprised of unwoven fabric used for polishing the surface of the semiconductor substrate, is used to planarize the insulating film. To obtain the polishing uniformity within the substrate surface, an elastic cushion layer is generally formed under a hard pad.
FIGS. 4A and 4B
show the arrangement of a conventional polishing apparatus.
As shown in
FIG. 4A
, the conventional polishing apparatus is constituted by a substrate holder
409
for holding a polishing target, a polishing table
410
to which a polishing pad
402
is adhered, an abrasive supply member
411
, and a conditioning mechanism
413
on which a diamond pellet
412
is mounted. Mechanisms provided to the substrate holder
409
and conditioning mechanism
413
to rotate, swing, and press them, and a rotational mechanism provided to the polishing table
410
are not illustrated.
As shown in
FIG. 4B
, a retainer ring
401
is set on a surface of the substrate holder
409
which opposes a substrate
405
, to correspond to the circumference of the substrate
405
. The retainer ring
401
holds the substrate
405
and prevents lateral shift of the substrate
405
. As the material of the retainer ring
401
, a hard plastic such as polyethylene terephthalate is used. An air cushion
407
applies a downward load to the retainer ring
401
. An elastic layer called an insert pad
403
is formed on the surface of the substrate holder
409
inside the retainer ring
401
.
By using the polishing arrangement having the above arrangement, for example, the surface of an interlevel insulating layer in the multilevel interconnection structure of an LSI is planarized.
During polishing, the retainer ring
401
prevents not only lateral shift of the substrate
405
but also abnormal polishing of the outer peripheral portion of the substrate
405
. More specifically, during polishing, the substrate
405
is urged against the polishing table
410
by the polishing pad
402
consisting of an upper hard layer and a lower soft layer. The contact pressure is the maximum at the outer peripheral portion of the substrate
405
.
At this time, as shown in
FIG. 5A
, the polishing pad
402
is deformed by the pressing force of the substrate
405
for several mm from the outer peripheral portion of the substrate
405
, and the pressure acting on the outer peripheral portion of the substrate
405
decreases. As a result, the polishing amount on the outer peripheral portion of the substrate
405
decreases. In particular, depending on the modulus of elasticity of the insert pad
403
and other polishing conditions, a deformation region
501
of the polishing pad
402
sometimes extends for several cm from the outer peripheral portion of the substrate
405
.
In the conventional polishing apparatus, abnormal polishing is suppressed in the following manner. First, the surfaces of the retainer ring
401
and substrate
405
that are to come into contact with the polishing pad
402
are set to be flush. The width of the retainer ring
401
with which the retainer ring
401
is to come into contact with the polishing pad
402
is set to be equal to or more than the deformation region described above of the polishing pad
402
. This suppresses a deformation region
502
from extending over the outer peripheral portion of the substrate
405
, as shown in FIG.
5
B.
A load is applied to the retainer ring
401
by the air cushion
407
independently of applying a load to the substrate
405
. This makes the pressure that presses the retainer ring
401
against the polishing pad
402
independent and constant. For example, the retainer ring
401
is brought into contact with the polishing pad
402
with a load of about 500 g/cm
2
(≈7 psi).
For this reason, during polishing, the retainer ring
401
is also polished by the polishing pad
402
, and the material of the retainer ring
401
generated by grinding spreads over the polishing pad
402
as impurities. In this case, if an alloy material such as stainless steel is used to form the retainer ring
401
, the metal component generated by grinding spreads over the polishing pad
402
to adversely affect the characteristics of devices formed on the substrate
405
. Also, the cutting chips of the alloy material damage the polishing surface of the polishing pad
402
. To solve these problems, a plastic is used as the material of the conventional retainer ring
401
.
As the process amount increases, the plastic retainer ring
401
deforms, and the specified performance is not maintained.
In this case, even if a hard plastic is used to suppress deformation, its mechanical strength is limited and inferior to that of a metal alloy material such as stainless steel. Even a conventional retainer ring using a hard plastic deforms when the number of polishing processes increases, and the capability of the retainer to press the polishing pad degrades. As a result, in the conventional polishing apparatus, when the number of polishing processes increases, an abnormality in polishing amount occurs on the outer peripheral portion of the substrate as a polishing target.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polishing apparatus in which, even if the number of polishing processes increases, occurrence of an abnormality in polishing amount on the outer peripheral portion of the substrate as a polishing target is suppressed.
In order to achieve the above object, according to the present invention, there is provided a polishing apparatus comprising a polishing pad adhered to a polishing table, a substrate holder for urging, while holding a substrate as a polishing target, a polishing target surface of the substrate against the polishing pad, and a retainer ring formed on a holding surface of the substrate holder to correspond to a circumference of the substrate, the retainer ring having a resin portion formed on a surface thereof which is to come into contact with the polishing pad, and an annular resin holding portion for holding the resin portion and made of a material having a higher mechanical strength than the resin portion.
REFERENCES:
patent: 5645474 (1997-07-01), Kubo et al.
patent: 5795215 (1998-08-01), Guthrie et al.
patent: 5997384 (1999-12-01), Blalock
patent: 6019670 (2000-02-01), Cheng et al.
patent: 1352932 (1974-05-01), None
patent: 7-227757 (1995-08-01), None
patent: 9-139366 (1997-05-01), None
patent: 9-155730 (1997-06-01), None
patent: 10-0267597 (2000-07-01), None
Masuta Youko
Uto Mitsuyoshi
Hail III Joseph J.
Hutchins, Wheeler & Dittmar
NEC Corporation
Nguyen G
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