Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-01-31
2002-03-26
Vo, Peter (Department: 3729)
Abrading
Abrading process
With tool treating or forming
C451S066000, C451S285000, C451S287000, C451S443000, C451S005000, C451S009000
Reexamination Certificate
active
06361411
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a system for conditioning a polishing surface, such as the surface of a web-shaped polishing pad. The invention also relates to rollers and other devices for applying different conditioning treatments to different portions of a polishing surface. The term “polishing” is used broadly herein to include planarizing and other mechanical and chemical-mechanical procedures for producing smooth surfaces.
2. Discussion of the Related Art
Systems for polishing semiconductor wafers and the like are well known. In a conventional process, a surface of a semiconductor wafer is mechanically scoured by a conformable polishing pad. A chemical slurry may be used in conjunction with the polishing pad to provide a high material removal rate and/or improved surface planarization.
In a typical chemical-mechanical planarization (“CMP”) process, relative movement between a semiconductor substrate and a wetted pad causes material to be chemically and physically polished from the substrate surface. Chemical-mechanical planarization is used to prepare wafers for integrated circuits, and to planarize substrates on which one or more layers have been deposited and etched.
Referring now to
FIG. 1
, it has been suggested to provide a polishing apparatus
20
with a continuous web-shaped polishing pad
22
. The pad
22
may be formed of a non-abrasive polymeric material, such as woven polyurethane, or other suitable materials. The pad
22
is movably supported on a workstation table
24
. Guide rollers
26
,
28
stretch the pad
22
over the table
24
in the illustrated position.
In operation, a carrier
30
presses a work piece, such as a semiconductor substrate
32
, against the pad surface
34
. The carrier
30
also rotates the substrate
32
around first and second parallel axes. Abrasive particles and/or chemicals in a planarizing slurry (not illustrated) assist in the removal of material from the surface of the substrate
32
. The slurry may be dispensed through suitable nozzles (not illustrated).
Over time, the surface
34
of the web-shaped pad
22
becomes “glazed.” The glazed condition may be caused by spent slurry accumulating in the porous pad surface
34
. In addition, the pressure applied by the carrier
30
tends to compress the pad
22
. As the pad
22
becomes glazed, its coefficient of friction is reduced and becomes non-uniform, resulting in a lower material removal rate and/or poor quality control. Glazing of the pad surface
34
may increase the time required to polish each substrate
32
. In addition, such glazing may make it difficult to obtain the desired substrate planarity.
For these and other reasons, the pad
22
may be provided on a supply roller
52
. The supply roller
52
carries an unused or pre-operative portion of the pad
12
. A motor (not shown in
FIG. 1
) advances the pad
22
intermittently in the direction of arrows
54
,
56
. Thus, clean pre-operative pad sections may be quickly substituted for used, glazed sections to provide a consistent pad surface (with a uniform coefficient of friction). In addition, the used, glazed sections may be conditioned at a point downstream from the work piece carrier
30
. The conditioned portion may be returned to the work piece carrier
30
. A downstream roller (not shown in
FIG. 1
) draws the glazed post-operative portion of the pad
22
away from the work piece carrier
30
.
Although the polishing system
20
is an improvement over the prior art, there is still a need for an improved system for conditioning the pad
22
to increase its useful life and improve its performance. Moreover, there is a need in the art for an improved conditioning device for applying different conditioning treatments to different portions of a polishing pad. The need for an improved conditioning device is applicable to web-shaped and circular polishing pads.
Systems for conditioning polishing pads are described in U.S. Pat. No. 5,830,043 (Aaron et al.), U.S. Pat. No. 5,785,585 (Manfredi et al.), U.S. Pat. No. 5,779,526 (Gill), U.S. Pat. No. 5,775,983 (Shendon et al.), U.S. Pat. No. 5,655,951 (Meikle et al.), U.S. Pat. No. 5,611,943 (Cadien et al.), U.S. Pat. No. 5,664,987 (Renteln), U.S. Pat. No. 5,527,424 (Mullins), and U.S. Pat. No. 5,486,131 (Cesna et al.) and European Published Patent Application No. 770,455 (Ko et al.).
SUMMARY OF THE INVENTION
The disadvantages of the prior art are overcome to a great extent by providing a web-format polishing apparatus with a device for conditioning a web-shaped polishing pad. Thus, according to one aspect of the invention, a polishing machine is provided with a system for moving a web-shaped polishing pad to and fro in the longitudinal direction, and a downstream device for conditioning a used glazed portion of the pad. According to this aspect of the invention, after the glazed portion is conditioned, it can be returned to its polishing position to polish more substrates.
In an alternative embodiment of the invention, the polishing pad may remain stationary and the conditioning device may be moved over and/or on the pad to the desired position for conditioning.
The polishing apparatus may be, for example, a chemical-mechanical planarizing machine for processing semiconductor wafers.
The conditioning device is preferably arranged to apply different conditioning treatments to different portions of the glazed polishing pad. Thus, the conditioning device may have roller segments that rotate at different speeds. Alternatively, the conditioning device may have non-cylindrical rollers that provide different rotational speeds at the pad surface, or means for applying different pressures to different portions of the pad.
According to another aspect of the invention, a conditioning device may be moved laterally to provide uniform or blended conditioning despite non-uniformities (such as spaces between rollers) in the conditioning device. In an alternative embodiment of the invention, a conditioning device is located at an angle with respect to the pad to provide uniform or blended conditioning without lateral movement.
The conditioning device may also be moved longitudinally, if desired, to ensure the desired conditioning over the entire length of the glazed portion.
According to another aspect of the invention, the surface characteristics of a polished work piece are measured, and the conditioning device is then controlled or adjusted in accordance with the measured characteristics. Thus, the invention may be used to reduce the occurrence of so-called within-wafer-non-uniformities (“WIWNUs”).
Conditioning devices constructed in accordance with the present invention may be used with web-shaped polishing pads and with rigid circular platen pads.
These and other features and advantages of the invention will become apparent from the following detailed description of preferred embodiments of the invention.
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Chopra Dinesh
Moore Scott E.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Trinh Minh
Vo Peter
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