Abrading – Work holder – Work rotating
Reexamination Certificate
2000-04-21
2002-03-12
Hail, III, Joseph J. (Department: 3723)
Abrading
Work holder
Work rotating
C451S011000, C451S288000, C451S041000
Reexamination Certificate
active
06354928
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to a polishing apparatus and, more specifically, to a magnetic polishing head and retaining ring for polishing semiconductor wafers.
BACKGROUND OF THE INVENTION
In the manufacture of microcircuit dies, chemical/mechanical polishing (CMP) is used to provide smooth topographies of the semiconductor wafers for subsequent lithography and material deposition. Briefly, the CMP process involves holding and rotating a thin, reasonably flat, semiconductor wafer while pressing the wafer against a rotating polishing surface or platen. The semiconductor wafer is held in a carrier that has a carrier ring about its periphery to restrain the wafer to a position under the carrier. The polishing surface is wetted by a chemical slurry, under controlled chemical, pressure, and temperature conditions. The chemical slurry contains selected chemicals which etch or oxidize specific surfaces of the wafer during processing. Additionally, the slurry contains a polishing agent, such as alumina or silica, which is used to abrade the etched/oxidized surfaces. The combination of mechanical and chemical removal of material results in superior planarization of the polished surface.
A polishing pad that rests on the surface of the polishing platen receives and holds the chemical slurry during polishing. Because of the extremely small tolerances necessary in semiconductor manufacture, it is important to maintain the planarity of the wafer.
Referring initially to
FIG. 1
, illustrated is a simplified, enlarged sectional view of a conventional carrier head and conventional polishing platen during polishing. As shown, a conventional carrier head
100
comprises a carrier body
110
, a retaining ring
120
, and a pneumatic interface
130
. A conventional polishing surface
140
comprises a polishing platen
150
, and a polishing pad
160
. A semiconductor wafer
170
has a surface
172
being polished. One who is skilled in the art is familiar with the ripple
162
effect on the polishing pad
160
as the carrier head
100
, semiconductor wafer
170
, polishing platen
150
, and polishing pad
160
rotate during polishing. In the illustrated embodiment, the free edge
121
contacted is on the retaining ring
120
that is being forced against the polishing pad
160
by a force
180
generated by the pneumatic interface
130
. In addition to retaining the wafer
170
under the carrier head
100
, the retaining ring
120
prevents the ripple
162
from contacting an outer edge
173
of the semiconductor wafer
170
and causing nonuniform polishing of the edge of the wafer
170
. This nonuniform polishing at the edge
173
is known as the edge effect. As the pad
160
retains polishing slurry
190
, any contact of the pad
160
with the wafer
170
will result in material removal from the wafer
170
. In order to avoid the edge effect through contact with the ripple
162
, the carrier ring
120
is extended toward the polishing pad
160
, typically with pneumatic pressure, to cause the ripple
162
to form outward toward the circumference of the carrier ring
120
and away from the wafer
170
. That is, a pneumatic interface
130
forces the retaining ring
120
against the pad
160
to form the ripple
162
. The pneumatic interface
130
may be a relatively complicated system requiring pneumatic lines, seals and actuators (not shown) to assure the retaining ring
120
remains in contact with the polishing pad
160
.
Accordingly, what is needed in the art is a simpler apparatus that eliminates the need to power an electromagnet in the polishing platen while still applying the necessary carrier ring force during chemical/mechanical polishing of semiconductor wafers.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides a polishing apparatus comprising a carrier head having a periphery, a first region, a carrier ring, and a second region. The carrier ring is coupled to the periphery. The carrier ring and carrier head are configured to cooperatively receive an object to be polished. The first region is associated with the carrier head and is capable of manifesting a polarity proximate the carrier ring. The second region is associated with the carrier ring and is capable of manifesting the same polarity proximate the first region. Therefore, the first and second regions have like polarities that create a repelling force between the carrier head and the carrier ring. The repelling force may be created by like magnetic fields or like electrostatic fields.
Thus, in one aspect, the present invention provides a polishing apparatus that has a polishing mechanism operable on the principles of magnetic or electrostatic forces that can be used to maintain a desired downward polishing force on a wafer.
In another embodiment, the first region is formed in the carrier head and the second region is formed in the carrier ring. The polishing apparatus, in an alternative embodiment, further comprises ring retainers interposed between the carrier head and the carrier ring. The ring retainers are configured to slidably couple the carrier head to the carrier ring.
In other embodiments, at least one of the first or second regions is a permanent magnetic region, a soft magnetic region, or an electromagnetic region. In a further aspect of this embodiment, the repelling force is adjustable by controlling a current in the electromagnetic region.
The polishing apparatus, in another embodiment, further comprises a drive motor coupled to the carrier head and configured to rotate the carrier head and the object, such as a semiconductor wafer. In one aspect of this embodiment, the polishing apparatus further comprises a polishing platen juxtaposed the carrier head and coupled to the drive motor configured to rotate the polishing platen. In an additional aspect, the polishing apparatus further comprises a polishing pad that is coupled to the polishing platen and that is configured to retain a polishing slurry. The polishing apparatus, in an another embodiment, further comprises a slurry delivery system in fluid communication with the polishing platen. The slurry delivery system is configured to deliver the polishing slurry to the polishing pad.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
REFERENCES:
patent: 5624299 (1997-04-01), Shendon
patent: 5679065 (1997-10-01), Henderson
patent: 5738574 (1998-04-01), Tolles et al.
patent: 5803799 (1998-09-01), Volodarsky et al.
patent: 5842912 (1998-12-01), Holzapfel et al.
patent: 6059638 (2000-05-01), Crevasse et al.
patent: 6231428 (2001-05-01), Maloney et al.
patent: 6234868 (2001-05-01), Easter et al.
Crevasse Annette M.
Easter William G.
Maze John A.
Miceli Frank
Agere Systems Guardian Corp.
Hail III Joseph J.
Thomas David B.
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