Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-03-17
2002-04-23
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C279S128000, C451S063000, C451S288000, C451S290000, C451S398000
Reexamination Certificate
active
06375549
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for fabricating semiconductor wafers and, more particularly, to a polishing head used for chemical-mechanical polishing (CMP).
BACKGROUND OF THE INVENTION
Chemical-mechanical polishing (“CMP”, “polishing” sometimes “planarization”) processes remove material from the surface of a wafer in the production of ultra-high density integrated circuits. In a typical CMP process, a wafer is exposed to an abrasive medium under controlled chemical, pressure, velocity, and temperature conditions. Conventional abrasive media include slurry solutions and polishing pads. The slurry solutions generally contain small, abrasive particles that abrade the surface of the wafer, and chemicals that etch and/or oxidize the surface of the wafer. The polishing pads are generally planar pads made from a relatively porous material such as blown polyurethane, and the polishing pads may also contain abrasive particles to abrade the wafer. Thus, when the pad and/or the wafer moves with respect to the other, material is removed from the surface of the wafer mechanically by the abrasive particles in the pad and/or slurry, and chemically by the chemicals in the slurry.
For the application of CMP and for prior art designs, the following references are useful: U.S. Pat. No. 5,879,226 to Robinson (“Reference 1”); U.S. Pat. No. 5,868,896 also to Robinson (“Reference 2”) and U.S. Pat. No. 5,643,061 to Jackson (“Reference 3”).
FIG. 1
illustrates a simplified diagram of a conventional CMP machine
101
with platen
120
(or “table”), wafer carrier
100
(or “polishing head”), polishing pad
140
, and slurry
144
on polishing pad
140
. Usually, drive assembly
191
rotates platen
120
as indicated by arrow A, or reciprocates platen
120
back and forth as indicated by arrow B. The motion of platen
120
is imparted to pad
140
. For convenience of explanation,
FIG. 1
introduces rectangular coordinate system XYZ with the X-axis going right, the Y-axis going into the page, and the Z-axis going up.
Wafer carrier
130
has lower surface
132
to which wafer
150
may be attached, or wafer
150
may be attached to resilient member
134
(e.g., a film) positioned between wafer
150
and lower surface
132
. Member
134
prevents that head
100
directly touches backside
152
of wafer
150
. Wafer carrier
100
may be a weighted, free-floating wafer carrier, or actuator assembly
192
may be attached to wafer carrier
100
to impart axial and rotational motion, as indicated by arrows C (Z-axis) and D, respectively.
In the operation of CMP machine
101
, wafer
150
is positioned face-downward with frontside
151
against polishing pad
140
. As frontside
151
of wafer
150
moves across planarizing surface
142
, polishing pad
140
and slurry
144
remove material from wafer
150
.
In the competitive semiconductor industry, it is desirable to maximize the throughput of the finished wafers and to minimize the number of defective or impaired devices on each wafer. The throughput of CMP processes is a function of several factors, one of which is the rate at which the thickness of the wafer decreases as it is being planarized (the “polishing rate”).
CMP processes must consistently and accurately produce a uniform, planar surface on frontside
151
of wafer
150
because it is important to accurately focus the image of circuit patterns on frontside
151
in further fabrication steps. As the density of integrated circuits increases, it is often necessary to accurately focus the critical dimensions of the circuit pattern to better than a tolerance of approximately 0.01 micro meter. Focusing the circuit patterns to such small tolerances, however, is very difficult when the distance between the lithography equipment and the surface of the wafer varies because the surface of the wafer is not uniformly planar. In fact, several devices may be defective on a wafer with a non-uniformly planar surface. Thus, CMP processes must create a highly uniform, planar surface. In terms of the coordinate system, polishing provides a substantially constant elevation Z across the whole frontside
151
(Z independent from X and Y).
For achieving an accurate polishing result, polishing head
100
can be considered as the most critical part. Irregularities, especially on backside
152
of wafer
150
or member
134
may cause that head
100
presses wafer
150
to pad
140
non-uniformly, thus leading to unwanted non-uniform polishing.
The present invention seeks to provide an improved polishing head and a method which mitigate or avoid these and other disadvantages and limitations of the prior art.
REFERENCES:
patent: 4692836 (1987-09-01), Suzuki
patent: 4811522 (1989-03-01), Gill, Jr.
patent: 5571044 (1996-11-01), Bolandi et al.
patent: 5584751 (1996-12-01), Kobayashi et al.
patent: 5643061 (1997-07-01), Jackson et al.
patent: 5700180 (1997-12-01), Sandhu et al.
patent: 5748434 (1998-05-01), Rossman et al.
patent: 5803799 (1998-09-01), Volodarsky et al.
patent: 5807165 (1998-09-01), Uzoh et al.
patent: 5857899 (1999-01-01), Volodarsky et al.
patent: 5868896 (1999-02-01), Robinson et al.
patent: 5879226 (1999-03-01), Robinson
patent: 5904611 (1999-05-01), Takahashi et al.
patent: 5911619 (1999-06-01), Uzoh et al.
patent: 0 706 854 (1996-04-01), None
Ebner Katrin
Glashauser Walter
Haggart David
Teichgräber Lutz
Eley Timothy V.
Motorola Inc.
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