Abrading – Machine – Reciprocating tool
Reexamination Certificate
2000-12-14
2003-09-02
Rose, Robert A. (Department: 3723)
Abrading
Machine
Reciprocating tool
C451S520000
Reexamination Certificate
active
06612914
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
1. Field of Invention
The embodiments of the present invention generally relate to a method and apparatus for supporting a web of polishing material in a polishing system.
2. Background of Invention
In semiconductor wafer processing, the use of chemical mechanical planarization, or CMP, has gained favor due to the enhanced ability to increase device density on a semiconductor workpiece, or substrate, such as a wafer. Chemical mechanical planarization systems generally utilize a polishing head to retain and press a substrate against a polishing material while providing motion therebetween. Some planarization systems utilize a polishing head that is moved over a stationary platen that supports the polishing material. Other systems utilize other motions, for example, providing a rotating platen. A polishing fluid is typically disposed between the substrate and the polishing material during polishing to provide chemical activity that assists in the removal of material from the substrate. Some polishing fluids also contain abrasives.
One type of polishing material that may be utilized for chemical mechanical polishing is known as fixed abrasive polishing material. Fixed abrasive polishing material generally comprises a plurality of abrasive particles suspended in a resin binder that is disposed in discrete elements on a backing sheet. As the abrasive particles are contained in the polishing material itself, systems utilizing fixed abrasive polishing materials generally utilize polishing fluids that do not contain abrasives.
FIG. 1
generally depicts a schematic of a conventional chemical mechanical polishing system
100
that utilizes a web
102
of polishing material to process a substrate
116
. The polishing system
100
generally includes a polisher
104
having at least one polishing station
106
. The polishing station
106
includes a platen
108
and a polishing head
110
. The web
102
of polishing material is supported by the platen
108
below the polishing head
110
. Generally, the platen
108
(or polishing table) has a top surface
112
that supports a polishing area
114
of the web
102
where processing occurs. The substrate
106
retained by the polishing head
110
is pressed against the polishing area
114
and moved relative thereto during processing.
The polishing area
114
of the web
102
is held against the platen
108
during processing typically by tensioning the web
102
between a supply roll
118
and a take-up roll
120
that are disposed on opposite sides of the platen
108
. The top surface
112
of the platen
108
may additionally contain a groove
122
that circumscribes the polishing area
114
. The groove
122
is coupled to a vacuum source
124
so that air and other fluids that may be present between the web
102
and the platen
108
are evacuated through the groove
122
, thus pulling the web
102
flush against the top surface
112
of the platen
108
.
A problem that is periodically encountered when using webs of polishing material is maintaining the web flush against the polishing surface. For example, the tension applied to the web between the supply roll and the take-up roll may cause the web to wrinkle along the direction of the web. As some polishing systems may tension the web in excess of 300 pounds, the disparity in the longitudinal and lateral stresses in the web creates a tendency of the web to wrinkle. Additionally, the web may creep across the platen during polishing due to the sheer forces experienced as the substrate is moved in relation to the web during polishing. As the web creeps, wrinkles are created. The wrinkles that are not be completely removed (i.e., flattened out) by the vacuum applied under the web create a non-planar surface that may disrupt polishing uniformity. Moreover, wrinkles extending across the vacuum sealing area at the edge of the platen may cause seal failure, thus allowing the web to separate from the platen.
Therefore, there is a need for a method and apparatus that improves the retention of polishing material in a polishing station.
SUMMARY OF INVENTION
In one aspect of the invention, an apparatus for retaining a web of polishing material is provided. In one embodiment, an apparatus for retaining a web of polishing material includes a platen that has a first clamp and a second clamp disposed on opposite sides of the platen. A top surface of the platen is adapted to support the web of polishing material in an orientation having the web's edges disposed approximate the first and second sides of the platen. The first and second clamps are actuated to laterally tension the web therebetween.
In another aspect of the invention, a method for retaining a web of polishing material to a platen is provided. In one embodiment, the method includes the steps of disposing a web of polishing material on a platen and laterally tensioning the web.
REFERENCES:
patent: 1353967 (1920-09-01), Lorenz
patent: 2399924 (1946-05-01), Hayward
patent: 5335453 (1994-08-01), Baldy et al.
patent: 5704827 (1998-01-01), Nishi et al.
patent: 6068542 (2000-05-01), Hosokai
patent: 2637343 (1978-02-01), None
patent: 0117656 (1918-07-01), None
Somer et al. “Polishing Media Stabilizer” U.S. patent application Ser. No. 09/258,036, filed Feb. 25, 1999.
Birang et al. “Apparatus and Methods for Chemical Mechanical Polishing with an Advanceable Polishing Sheet” U.S. patent application Ser. No. : 09/244456, filed Feb. 4, 1999.
Gurusamy Jayakumar
Hoey Gee Sun
Applied Materials Inc.
Moser Patterson & Sheridan
Rose Robert A.
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