U.S. patent application number 10/924832 was filed with the patent office on 2006-03-02 for method of improving planarization of urethane polishing pads, and urethane polishing pad produced by the same.
Invention is credited to Dwaine Halberg, Peter Renteln.
Application Number | 20060046627 10/924832 |
Document ID | / |
Family ID | 35944007 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060046627 |
Kind Code |
A1 |
Renteln; Peter ; et
al. |
March 2, 2006 |
Method of improving planarization of urethane polishing pads, and
urethane polishing pad produced by the same
Abstract
For improving planarization of urethane polishing pads, at least
one layer of the pad has a base resin and an isocyanate with a
concentration within a range of 6.5-11.0 weight percent to obtain a
high planarization property.
Inventors: |
Renteln; Peter; (San Ramon,
CA) ; Halberg; Dwaine; (Mesa, AZ) |
Correspondence
Address: |
SNELL & WILMER;ONE ARIZONA CENTER
400 EAST VAN BUREN
PHOENIX
AZ
850040001
US
|
Family ID: |
35944007 |
Appl. No.: |
10/924832 |
Filed: |
August 25, 2004 |
Current U.S.
Class: |
451/533 |
Current CPC
Class: |
B24B 37/24 20130101;
B24D 3/34 20130101 |
Class at
Publication: |
451/533 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A method of improving planarization of urethane polishing pads,
comprising the steps of producing at least one of urethane with a
base resin; introducing in the base resin isocyanate; and selecting
a concentration of the isocyanate within a range of 6.5-11.0% to
obtain a high planarization property.
2. A method as defined in claim 1, wherein selecting includes
selecting a concentration of the isocyanate within a range
6.5-8.5%.
3. A method as defined in claim 1, wherein said selecting includes
selecting a concentration of the isocyanate within a range of
8.5-11.0%.
4. A method as defined in claim 1, wherein said layer is composed
of a polyurethane selected from the group consisting of a polyether
polyurethane and polyester polyurethane.
5. A method as defined in claim 1, and further comprising
introducing in the layer abrasive particles selected from the group
consisting of silica, alumina, ceria, titania, diamond and silicon
carbide.
6. A method as defined in claim 1, wherein said producing includes
producing the at least one layer without abrasive particles.
7. A method as defined in claim 1; and further comprising
introducing a filler into the at least one layer.
8. A urethane polishing pad, comprising at least one layer having a
base resin, and isocyanate introduced in the base resin, wherein a
concentration of the isocyanate is within a range of 6.5-11.0%.
9. A urethane polishing pad as defined in claim 8, wherein the
concentration of the isocyanate is within a range of 6.5-8.5%.
10. A urethane polishing pad as defined in claim 8, wherein the
concentration of the isocyanate is within a range of 8.5-11.0%.
11. A urethane polishing pad as defined in claim 8, wherein at
least one layer is composed of polyurethane selected from the group
consisting of a polyether polyurethane and polyester
polyurethane.
12. A urethane polishing pad as defined in claim 8, wherein said at
least one layer contains abrasive particles selected from the group
consisting of silica, alumina, ceria, titania, diamond, and silicon
carbide.
13. A urethane polishing pad as defined in claim 8, wherein at
least one layer is absent of abrasive particles.
14. A urethane polishing pad as defined in claim 8, wherein said at
least one layer includes a filler.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to polishing pads, and methods
of producing the same.
[0002] The present invention generally relates to polishing pads,
in particular to chemical-mechanical polishing (CMP) pads. CMP is a
process step in the semiconductor fabrication sequence that has
generally become an integral part of the manufacture of
semiconductor wafers. The process is used in a variety of
applications in the semiconductor fabrication sequence. Different
applications are sometimes best optimized with different polishing
pad types and configurations. The present invention generally
concerns itself with a process application known as "oxide". Other
applications include copper, copper barrier and poly.
[0003] In any of these CMP processes, the silicon substrate is
forcibly placed in direct contact with a moving polishing pad. A
wafer carrier applies pressure against the backside of the
substrate, usually while simultaneously forcibly applying rotation.
During this process a slurry is made available, and is generally
carried between the wafer and the pad by the motion of the pad. The
composition of the slurry is dictated by the specific
application.
[0004] The CMP polishing pad is required to perform a plurality of
engineering functions. It is required to polish, planarize short
(<100 micrometer) distances, planarize long (>100 micrometer)
distances up to a certain Planarization Length (see below)
determined by the quality of the silicon substrate, not planarize
beyond that length, transport slurry, maintain the same friction
with the wafer for wafers polished--sequentially and with
interruptions--for hundreds of wafers, clean the wafer surface, not
scratch the wafer surface, be replaceable in minimal time, and
others. This invention addresses the planarization capability of
the pad.
[0005] This invention comtemplates both short and long range
planarization. Generally, long range planarization is controlled by
the bulk properties of the pad and short range planarization is
controlled by the surface properties of the pad. A concept useful
in describing long range planarization is the Planarization Length
(L), defined as a lateral dimension characteristic of the pad's
ability to planarize. Intrinsic to this concept is Preston's
equation, which maintains that when polishing, the removal rate is
proportional to force. There are significant deviations to this
relationship, but it holds generally, and for our purpose, it is
sufficient. With Preston in mind, one can consider a feature to be
planarized consisting of an upraised element. (FIG. 1) A polishing
pad will try to planarize the feature, and will succeed in doing so
when the pressure exerted by the pad at the top of the feature
exceeds the pressure exerted adjacent to the feature. Ala Preston,
the removal rate at the top of the feature will exceed the removal
rate adjacent to the feature and over time the feature will
decrease in height. One definition of planarization length is the
distance from the feature that the pressure has increased to 1/e of
the pressure infinitely far from the feature (e is ln(10)).
[0006] Short range planarization has no analog to L. Since the
short range planarization is affected by the surface properties, it
can vary dramatically using the same polishing pad by varying the
amount of diamond conditioning received by the pad, an action that
affects the pad's surface roughness. However, generally the pad
surface is conditioned for the purpose of maintaining the removal
rate. Therefore with regard to short range planarization, the
engineering constraint is placed on the pad rather
results-oriented. If written, it would read something like, " . . .
when consistently using a standard conditioning process the pad
should exhibit adequate removal rate as well as high short range
planarization . . . ". Because of this, the short range
planarization requirement generally comes from empirical results.
For the copper application, these results would typically be
expressed in dishing, the amount of material removed from a narrow
copper line. For oxide applications, the results would typically be
expressed by the planarization performance of a test structure
designed to measure short range planarization.
[0007] An improvement to polishing pads designed improve
planarization is contemplated in James (U.S. Pat. No. 6,454,634),
and in follow-on patents by James, U.S. Pat. No. 6,582,283, No.
6,736,709 and No. 6,749,485. While James offers an example of an
additive that achieves the desired high KEL value, the teachings
and data support the desired property only for what has been
described above as short range planarization, namely planarization
which occurs over a distance of less than 100 micrometers. The
present invention considers formulations which affect both short
and long range planarization.
[0008] The measurement of planarization is made using planarization
test structures. These are topographical structures which contain
regular periodic arrays arranged in regions of different pitch and
width. Due to practical limitations related to metrology the
smallest of these to yield an accurate measurement had a 100
micrometer pitch at 50% density (i.e. alternating high and low
structures of equal width) and the largest had a 500 micrometer
pitch at 50% density. Planarization capability is measured by a
repeating sequential polish/measure action in which the remaining
amplitude and the average amount of oxide removed is recorded for
each step. The sequence is complete when the structure is
planarized below the noise level. This sequence yields a curve
which can be further reduced to single FIGURE of merit of
planarization called the Planarization Efficiency. In order to
capture both short and long range planarization together, we have
developed a parameter we call the General Planarization Efficiency
(GPE) which consists of the average of the short and long range
efficiencies. The GPE ranges from 0% to 100%, in which 0%
represents no planarization at all (i.e. perfect etching), while
100% represents perfect planarization (material removed only from
high areas, none whatsoever from low areas). This invention
addresses formulations which lead to an improved GPE.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is an object of the present invention to
provide a method of improving planarization of urethane polishing
pads which is a further improvement of the existing methods, and
also to provide a polishing pad which is characterized by better
planarization properties.
[0010] In keeping with these objects and with others which will
become apparent hereinafter, one feature of the present invention
resides, briefly stated, in a method of improving the planarization
property of a polishing pad, in accordance with which isocyanate is
introduced in a base polyol resin of the urethane polishing pad
within a concentration range of 6.5% to 11.0%.
[0011] When isocyanate is introduced into the basic resin of a
urethane pad with the concentration selected in accordance with the
present invention, a GPE within the range of 75%-95% is obtained,
which can be characterized as a very good planarization
property.
[0012] The novel features which are considered as characteristic
for the present invention are set forth in particular in the
appended claims. The invention itself, however, both as to its
construction and its method of operation, together with additional
objects and advantages thereof, will be best understood from the
following description of specific embodiments when read in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates a planarization of urethane polishing
pads as a function of NCO concentration produced in accordance with
the present invention
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] In accordance with the present invention, urethane polishing
pads are produced in a conventional manner by providing a basic
polyol resin with a corresponding composition, and isocyanate is
introduced into the basic resin. It is to be understood that the
whole pad can be produced in this way or only its working layer, in
the event when the pad is a multi-layer pad. In a new and special
way, the isocyanate is introduced with a concentration of between
6.5% and 11.0% into the basic resin.
[0015] Tests have been conducted to determine the planarization of
the pad produced in accordance with the present invention. Four
polishing pads have been tested, in particular a polishing pad
L-100 with isocyanate concentration of 4.0%, a polishing pad L-200
with isocyanate concentration of 7.5% and L-325 with isocyanate
concentration 9.5% from the Adiprene series, and resin 2505 with
isocyanate concentration 11.6% from the Royalcast series, all from
Crompton Uniroyal Chemical. As shown in FIG. 1, when the urethane
polishing pads with isocyanate concentration in accordance with the
present invention were tested, they achieved the planarization
within the range of 72-95%.
[0016] A breakdown of the data into groups normally expected to
affect planarization does not alter the result. For example,
grooving is known to generally negatively affect the GPE of the pad
by structurally weakening the surface. However, the aforementioned
planarization range was found to hold both for pads with and
without grooving. It is also known that the use of a soft subpad
can negatively affect the GPE (by virtue of its effect on the long
range planarization). Again in this case the results were
unaffected when considering solo pads and pad stacks separately. It
is therefore understood that the NCO concentration controls
physical properties of the pad which affect both the short and the
long range planarization capability.
[0017] In accordance with an advantageous feature of the present
invention, the concentration of the isocyanate can be within a
range of 6.5-8.5%. In this case the urethane pad or its working
layer is softer and suitable for barrier buff.
[0018] In accordance with another preferable feature of the present
invention, the concentration of the isocyanate can be within a
range of 8.5-11.0%. In this case the urethane pad or its working
layer is harder and is suitable for interlayer dielectric.
[0019] The urethane pad or its layer can be composed of polyester
polyurethane or a polyether polyurethane.
[0020] The urethane pad or its working layer can contain abrasive
particles which can be composed of silica, alumina, ceria, titania,
diamond, or silicon carbide.
[0021] On the other hand, the urethane pad or its working layer can
be absent of abrasive particles.
[0022] The urethane pad or its working layer in accordance with the
present invention can also include a filler.
[0023] The above presented ranges of planarization are highly
efficient for the urethane polishing pads. As can be seen if this
isocyanate concentration is less than 6.5% and more than 11.0%, the
planarization property of the urethane polishing pads worsens.
[0024] It will be understood that each of the elements described
above, or two or more together, may also find a useful application
in other types of methods and constructions differing from the
types described above.
[0025] While the invention has been illustrated and described as
embodied in a method of improving planarization of urethane
polishing pads, and urethane polishing pad produced by the same, it
is not intended to be limited to the details shown, since various
modifications and structural changes may be made without departing
in any way from the spirit of the present invention.
[0026] Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior art,
fairly constitute essential characteristics of the generic or
specific aspects of this invention.
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