Ex Parte Evans

Board of Patent Appeals and Interferences

Sep 30, 2005

09270606 (B.P.A.I. Sep. 30, 2005)

The opinion in support of the decision being entered today was not written for
publication and is not binding precedent of the Board.
UNITED STATES PATENT AND TRADEMARK OFFICE
____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________
Ex parte DAVID RUSSELL EVANS
____________
Appeal No. 2005-1220
Application No. 09/270,606
____________
ON BRIEF
____________
Before KIMLIN, WALTZ and KRATZ, Administrative Patent Judges.
KRATZ, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on appeal from the examiner's final
rejection of claims 1-20, which are all of the claims pending in
this application.
BACKGROUND
Appellant's invention relates to a chemical-mechanical
polishing (CMP) process. An understanding of the invention can
be derived from a reading of exemplary claims 1 and 13, which are
reproduced below.
1. An method of fabricating an integrated circuit
using CMP comprising:
providing a substrate with an overlying silicon
dioxide layer, and without any dummy structure;
forming a CMP slurry containing cerium oxide;
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Application No. 09/270,606
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adding a slurry modifier to the slurry, wherein
the slurry modifier combined with CMP slurry polishes
low structure areas at a substantially zero rate and
polishes high structure areas at a rate approximating a
blanket polishing rate without the use of a dummy
structure; and
polishing the silicon dioxide layer without
polishing any dummy structure using the modifier-
containing slurry, whereby the low structure areas are
polished at a substantially zero rate and the high
structure areas are polished at a rate approximating
the blanket polishing rate without using any dummy
structure.
13. A method of fabricating an integrated circuit
using CMP comprising:
providing a substrate with an overlying silicon
dioxide layer, and without any dummy structure such
that the silicon dioxide layer forms low structure
areas and high structure areas, without any dummy
structure;
forming a CMP slurry having a high structure
polishing rate lower than a blanket polishing rate;
adding a slurry modifier to the slurry to produce
a modified slurry that polishes high structure at a
rate approximating the blanket polishing rate; and
polishing the high structure areas of silicon
dioxide, whereby the high structure area are polished
at a rate approximating the blanket polishing rate
without using any dummy structure.
The prior art references of record relied upon by the
examiner in rejecting the appealed claims are:
Kodera et al. (Kodera) 5,445,996 Aug. 29, 1995
Grover et al. (Grover) 5,759,917 Jun. 02, 1998
Burke et al. (Burke) 5,934,978 Aug. 10, 1999
Claims 1-20 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over Kodera in view of Grover and Burke.
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Application No. 09/270,606
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We refer to the brief and reply brief and to the answer for
a complete exposition of the opposing viewpoints expressed by
appellant and the examiner concerning the issues before us on
this appeal.
OPINION
Having carefully considered each of appellant’s arguments
set forth in the brief and reply brief, appellant has not
persuaded us of reversible error on the part of the examiner.
Since we are in substantially complete agreement with the
examiner’s application of the prior art, as well as the
examiner’s disposition of the arguments and evidence raised by
appellant in the brief, we will affirm the examiner’s rejections
for substantially the reasons set forth in the answer. We add
the following for emphasis.
Appellant furnishes six separate claim groups: (i) claims 1-
3, 5, 6, 10 and 11; (ii) claims 4, 7-9, 12, 16; (iii) claims 13
and 14 and (iv) claims 17-19; (v) claim 15; and (vi) claim 20
(brief, pages 4 and 5). For the four groupings involving more
than one claim, appellant states that the claims of each such
grouping stand or fall together. Consequently, we select claims
1, 4, 13 and 17 as the respective representative claims on which
we shall decide this appeal as to appellant’s claim groups (i)-
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Application No. 09/270,606
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1Also, see the current regulation as to separate claim
arguments as set forth in 37 CFR § 41.37(c)(1)(vii) (September
13, 2004).
(iv), as identified above. Claims 15 and 20 are separately
identified as standing or falling alone. Consequently, to the
extent appellant has clearly stated that the latter claims do not
stand or fall together and have also argued each claim separately
with respect to any particular ground of rejection consistent
with 37 CFR § 1.192 (c)(7) and (8), as in effect at the time of
the filing of the briefs1, we shall treat those claims
separately.
We start with claim 1, which is representative of the Group
(i) claims.
Appellant does not dispute that Kodera is directed to a
method of fabricating an integrated circuit semiconductor device
using chemical mechanical polishing (CMP). Kodera teaches that a
substrate with an overlying silicon dioxide layer with low and
high structure areas can be polished using a CMP slurry
containing cerium oxide, wherein the silicon dioxide film that is
polished can be completely planarized. See, e.g., column 12,
lines 13-65 and column 20, line 1 through column 23, line 33 and
Figures 19 E and 19 F of Kodera. As readily apparent from a
complete reading of Kodera, the high structure areas are polished
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2 Appellant defines a dummy structure as structures that
“are used for the sole purpose of controlling the CMP rate”
(specification, page 1, lines 14-16).
at a higher rate than the low structure areas such that the
planarization described is achieved. Kodera does not describe
using a dummy structure2 in the embodiment depicted in Figures 19
E and 19 F, which is consistent with the dummy structure
exclusion of claim 1.
Moreover, Kodera teaches that other appropriate materials
may be employed in the cerium oxide polishing slurry and that the
use of a cerium oxide polishing slurry in accordance with the
method depicted in Figures 19 E and 19 F, as described in the
specification, results in solving problems earlier identified in
the specification. See column 23, lines 1-33 of Kodera. Given
that disclosure of Kodera and the teachings of Grover and Burke
with respect to using other additives including dispersion aids
in a CMP slurry employing cerium oxide, we agree with the
examiner (answer, page 8) that it would have been obvious to one
of ordinary skill in the art at the time of the invention to
employ a slurry modifier in the CMP slurry of Kodera. In this
regard, Grover teaches using additives such as other abrasives,
acids and surface active dispersing agents and Burke teaches that
adding a surfactant or suspension agent, including ethylene
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glycol, is beneficial in such a CMP slurry in improving colloidal
behavior and reducing or inhibiting the growth and/or coalescence
of particles in the slurry. See, e.g., column 3, lines 13-26,
column 4, lines 18-29 and column 6, lines 8-64 of Grover and
column 3, lines 32-39 and column 3, line 61 through column 4,
line 13 of Burke.
Furthermore, we agree with the examiner that the polishing
step of Kodera employing such a modified cerium oxide slurry
would have obviously resulted in Kodera employing high and low
area removal rates corresponding to the claimed rates upon
routine experimentation to determine the workable operating
parameters for the polishing given that substantially the same
polishing slurry is being used in a substantially similar way to
achieve substantially the same object of planarization of a
silicon dioxide layer including high and low structure areas
during a semiconductor CMP polishing step by both appellant and
Kodera. See In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433-
34 (CCPA 1977).
With further regard to this matter, we note that
representative claim 1 calls for polishing rates such that low
structure areas are polished at a substantially zero rate and
high structure areas are polished at a rate approximating the
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3 A blanket polishing rate is defined in appellant’s
specification as a removal rate that is obtained (measured) on an
unpatterned waiver. See page 2, line 23 of appellant’s
specification.
blanket polishing rate.3 Concerning those claimed polishing
rates, we note that each of those claimed rate terms employ a
term of degree (“substantially” or “approximating”), which terms
thus encompass a range of polishing (silicon dioxide layer high
and low structure area removal) rates. In this regard,
appellant’s specification furnishes graphs and descriptions
thereof that reasonably make clear those claimed rate ranges
encompass rates significantly different than either a zero
removal rate or a blanket removal rate, respectively. For
example, at page 5, line 2 through page 7, line 13, appellant’s
specification provides that (underlining supplied):
If polishing using ceria slurry is carried out for a
sufficiently long time, two important results occur:
First, when the substrate surface becomes substantially
planarized, polishing characteristics revert back to
more conventional behavior. Second, if silicon,
polysilicon, or silicon nitride underlie the polished
layer of silicon dioxide, they tend to act as a polish
stop. These results are illustrated in FIGS. 6a-6d,
which depict polishing characteristics for feature size
scales corresponding to FIGS. 3 and 5. Long term ceria
polishing characteristics are illustrated generally at
60. A high area rate 62 approximates blanket rate 20
over time, while a low area rate 64 is close to zero.
Convergence points 66 are reached in some instances,
with a converged rate 68 being shown for those
instances. Where an appropriate underlying material is
present, a polish stop rate 70 is shown.
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Further testing has demonstrated that addition of a
modifier to ceria slurry, in particular ethylene
glycol, causes the polishing characteristics
illustrated in FIGS. 4, 5 and 6 to become more
conventional, as illustrated in FIGS. 2 and 3. This
characteristic is shown generally at 80 in FIG. 7,
which illustrates the effect of addition of 10% (FIG.
7a) and 20% (FIG. 7b) ethylene glycol, and a down
pressure of 6 psi.. A high area rate 82 is
approximately the same as blanket rate 20, while a low
area rate 84 remains close to zero. Characteristics
82a, 84a, represent a feature size scale of 2x2 :m;
characteristics 82b, 84b, represent a feature size
scale of 4x4 :m; characteristics 82c, 84c, represent a
feature size scale of 8x8 :m; and characteristics 82d,
84d, represent a feature size scale of 16x16 :m. A
convergence point 86 is depicted, but not really
achieved in the depicted results. Longer polishing
times result in the desired convergence and
planarization.
A 10%, by volume, addition of ethylene glycol results
in the polishing rate of high areas and the blanket
polishing rate to be nearly equal. In comparison, for
addition of 20% ethylene glycol by volume, the removal
rate has fallen below the blanket polish rate. This is
similar to conventional behavior. As expected, control
wafers polished in slurry with no ethylene glycol
modifier show the usual behavior. Ethylene glycol
concentrations up to 50% may be used.
The effect of the modifier can be offset by increasing
down force. The effect of a 50% increase in down force,
to 9 psi, for a 20% by volume addition of ethylene
glycol to ceria slurry is shown in FIG. 8, at 90. A
high area rate 92, low area rate 94 and convergence
point 96 are depicted, with the characteristics being
as described in connection with FIG. 7. The preferred
modifier is ethylene glycol, however, other modifiers
may work as well provided that they alter physical
properties of the slurry in the desired way. The
modifier may either be pre-mixed in the slurry
feedstock or introduced directly to the polishing table
to be mixed with slurry during processing. Ideally, the
modifier does not participate in the slurry chemistry,
but, only affects slurry physical characteristics,
i.e., viscosity, surface tension, etc. or
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Application No. 09/270,606
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concomitantly, effective slurry layer thickness during
the polishing process.
The ideal polishing characteristic of FIG. 1 implies
that all pattern dependence may be eliminated because,
regardless of size or density, high structure areas
polish at the same rate as a flat blanket wafer.
Therefore, as the invention is implemented in
conjunction with a judicious choice of polishing
parameters such as down force, etc., the polishing
characteristics of FIG. 1 may be closely approximated.
When practicing the preferred embodiment of the
invention, a down force of five to ten psi is applied.
A table rotation rate of about 20 to 100 rpm is
established, as is a spindle rotation rate of about 20
to 100 rpm. A slurry flow rate of 0.50 to 500 ml/min.
is maintained.
In a more universal sense, the method of the invention
may be used for general global planarization. Use of
this method will increase process margin and reduce or
eliminate the need to include dummy structures in
circuit layouts.
Although a preferred embodiment of the method of the
invention has been disclosed herein, it will be
appreciated that further variations and modification
may be made thereto without departing from the scope of
the invention as defined in the appended claims.

Looking at appellant’s Figures 7(A) and 7(B) (copy attached
to the brief), for example, the low area rate 84 (a-d) is
described by appellant as being close to zero not withstanding
that the graph depicts that 1,000 angstroms of the low areas of
the oxide surface polished is removed prior to a convergence
point being reached during the polishing operation (see, e.g.,
label 84d in Figure 7A). Likewise in appellant’s Figure 8, label
94d suggests that nearly 2,000 angstroms of the low areas of the
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Application No. 09/270,606
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4 After all, it is well settled that claim terms are given
their broadest reasonable meaning consistent with the
specification during examination proceedings before the U.S.
Patent and Trademark Office. In this regard, appellant’s claims
clearly are not limited to high and low area polish removal rates
as depicted in the idealized graph of appellant’s drawing figure
1.
5 Those claimed rate terms involve some ambiguity as a
result of appellant’s use of terms of degree in claiming the
oxide surface that is polished is removed prior to a convergence
point being reached. Yet, appellant recognizes that graph as
depicting a low area removal rate consistent with the disclosed
invention (involving a substantially zero rate of removal of the
low area structure). Consequently, we interpret the claimed
“substantially zero” rate of removal of the low structure areas
of the oxide layer to include rates of removal that are
significant but low relative to the rate of removal of the high
structure area removal rate such that a convergence point
(planarization) is reasonably achieved.4 In like fashion, our
review of appellant’s drawing figures lead us to the conclusion
that the claim term “approximating the blanket polishing rate” is
inclusive of polishing rates that deviate significantly from a
blanket polishing rate so long as those rates are relatively high
as compared to the rate at which the low structures of the oxide
layer is removed during polishing such that planarization is
obtained without using a so-called “dummy structure”.5
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polishing rates without appellant having particularly defined or
having specified a particular way of assessing the meets and
boundaries of those terms of degree in the specification, as
filed. Nevertheless, for reasons stated above, we determine that
the merits of the examiner’s obviousness rejection can be
assessed by giving those claim terms a reasonable conditional
claim interpretation based on their broadest reasonable meaning
in light of appellant’s drawing figure representations, as
discussed above. However, in the event of further prosecution of
this subject matter before the examiner, the examiner should
determine whether or not the claims are compliant with the second
paragraph of § 112 in light of those terms of degree as employed
in the claims. After all, a principal purpose of the second
paragraph of § 112 is to provide those who would endeavor, in
future enterprises, to approach the area circumscribed by the
claims of a patent, with adequate notice demanded by due process
of law, so that they may more readily and accurately determine
the boundaries of protection involved and evaluate the
possibility of infringement and dominance. See In re Hammack,
427 F.2d 1378, 1382, 166 USPQ 204, 208 (CCPA 1970).
Consequently, we are in full agreement with the examiner’s
obviousness determination of the subject matter of representative
claim 1 over the combined teachings of the applied prior art.
In light of the above discussion, appellant’s arguments
concerning a lack of suggestion of the claimed subject matter in
the applied references is not persuasive. Concerning the
examiner’s combination of Grover and Burke with Kodera, we note
that the applied prior art need not disclose the same function
for the modified slurry composition that is employed as that
disclosed by appellant for the prior art to render the use of a
slurry composition, as claimed, obvious within the meaning of
§ 103(a). See, e.g., In re Kemps, 97 F.3d 1427, 1430, 40 USPQ2d
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1309, 1311 (Fed. Cir. 1996). In this regard, we again note that
Kodera teaches that other appropriate materials may be employed
in the cerium oxide polishing slurry and that the use of a cerium
oxide polishing slurry in accordance with the method depicted in
Figures 19 E and 19 F, as described in the specification, results
in solving problems earlier identified in the specification. See
column 23, lines 1-33 of Kodera.
One of those earlier noted problems is a problem with
conducting a polishing operation such that the rate of removal of
the raised portions of the silicon dioxide layer is significantly
greater than the rate of removal of the lower portions of the
silicon dioxide layer during polishing such that planarization is
achieved without using inordinately thick silicon dioxide layers.
Another problem discussed in Kodera relates to a so-called
dishing phenomena. See, e.g., column 3, lines 4-24 and column 3,
line 42 through column 4, line 6 of Kodera. Those problems,
which are discussed with respect to prior art polishing methods,
are addressed by the inventive methods discussed in Kodera. See,
e.g., column 12, lines 13-65 and the above-noted portion of
column 23 of Kodera. Accordingly, we do not find appellant’s
arguments related to dishing problems as presented in the reply
brief, and the asserted lack of a suggestion of the claimed
relatively high removal rate for the raised portion of the
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Application No. 09/270,606
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silicon dioxide layer relative to lower portions of that layer to
be persuasive.
With regard to representative claim 4 and appellant’s second
claim grouping, appellant also maintains that the ethylene glycol
component of the polishing slurry, as required by that claim is
not suggested by the combined teachings of the references.
However, for reasons set forth above and in the answer, we
disagree. The use of slurry modifiers including a dispersing or
suspension agent, such as ethylene glycol is clearly suggested by
the teachings of those combined references so as to aid in the
dispersion of the cerium oxide and any other abrasive particles
in the polishing slurry. One of ordinary skill in the art would
have readily determined the workable and optimum amounts of such
a result effective suspension agent to be used in the polishing
slurry upon routine experimentation. Consequently, those
additional arguments do not overcome the examiner’s obviousness
rejection of the second group of claims.
Concerning representative claim 13 of appellant’s third
claim grouping, we recognize that a substantially zero polishing
rate for low structures is not required therein albeit an
approximately blanket rate of polishing the high structure areas
is required. For reasons stated above and in the answer, we find
that high structure polishing rate as called for in
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representative claim 13 obvious to one of ordinary skill in the
art at the time of the invention. As for the additional claim
requirement that the high structure polishing removal rate of the
slurry would be less than the blanket rate prior to adding a
slurry modifier, such as ethylene glycol, we note that it is
reasonable to expect that the cerium oxide slurry of Kodera would
have a substantially similar rate prior to adding ethylene glycol
as a dispersing agent given the commonalities thereof to the CMP
slurry of appellant. It is well settled that in a case such as
this where appellant is asserting a functional property for a
slurry that is alleged to be not possessed by a prior art slurry
that appears to comparable to that of appellant, it is
appropriate that the burden is shifted to appellant to show that
the prior art slurry would not, in fact, possess the property in
question. Here, appellant has not undertaken, much less
discharged, that burden. It follows that we will also sustain
the examiner’s obviousness rejection of the third claim grouping.
Regarding the fourth multiple claim grouping (Issue No. 5)
and representative claim 17, appellant acknowledges that Kodera
seemingly discloses a low density high structure polishing rate
that is essentially the same as a high density high structure
polishing rate, as required by claim 17, albeit in so doing
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Application No. 09/270,606
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Kodera employs a dummy structure (stopper layer), which is
excluded by the representative claim, as argued by appellant.
As explained at the bottom of page 6 of appellant’s
specification, approaching the ideal polishing characteristics as
depicted in Figure 1 (blanket polishing rate of high structure
areas) results in such a pattern independent polishing rate, that
is, a rate that is the same for high and low density high
structure areas. Because we have found that the applied prior
art would have reasonably suggested using a CMP slurry having the
property of allowing for polishing rates for the high structure
areas that approximate the blanket polishing rate for reasons
discussed above, we also find that the argued characteristic of
the CMP slurry of claim 17 would also reasonably have been
expected to result from employing a modified slurry as suggested
by the applied references for the Figure 19 embodiment of Kodera.
Moreover, as far as the polysilicon layer 203 and the amorphous
silicon film 233A of Kodera in other embodiments thereof as
referred to at page 13 of appellant’s brief are concerned, we do
not consider those layers to be a dummy structure as excluded by
representative claim 17. In this regard and as we reported in
footnote 2 above, appellant defines a dummy structure as a
structure that is used for the sole purpose of controlling the
CMP rate. Kodera, however, employs the polysilicon layer 203 for
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the electrical conductivity thereof and only selectively removes
same; that is, removes portions thereof. See column 27, lines 5-
11 of Kodera. Also, Kodera employs the amorphous silicon film
233A to form another insulating layer therefrom. See column 30,
lines 15-19 of Kodera. Consequently, Kodera also reasonably
appears to suggest the process of representative claim 17 in
those other embodiments, as seemingly acknowledged by appellant
but for the dummy structure argument, which we do not find
persuasive.
Concerning claim 15, appellant maintains that the combined
references’ teachings would not suggest using ethylene glycol for
the purposes identified by appellant. However, for reasons
discussed above, the collective teachings of the references do
suggest using ethylene glycol in the polishing slurry of Kodera
as a dispersing agent and appellant has not persuasively rebutted
that position of the examiner. As noted above, the rationale
provided by the collective teachings of the applied references
for making a particular modification of a reference need not be
the same as that disclosed by appellant for the modification to
be obvious within the meaning of § 103.
Finally, with regard to claim 20, appellant presents a
similar argument regarding the obviousness of adding ethylene
glycol to the slurry of Kodera. For the reasons advanced above,
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Application No. 09/270,606
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we again reiterate that the direction to the claimed invention
suggested by the prior art need not be by way of the same
motivating force as appellant may disclose for their invention.
Rather, the applied references, as is the case here, can make out
a sustainable case of obviousness premised on one of ordinary
skill in the art being led to subject matter corresponding to the
claimed subject matter for reasons distinctly different than
reasons that appellant may have developed.
It follows that, on this record, we will sustain the
examiner’s obviousness rejection of the appealed claims.
CONCLUSION
The decision of the examiner to reject claims 1-20 under
35 U.S.C. § 103(a) as being unpatentable over Kodera in view of
Grover and Burke is affirmed.
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No time period for taking any subsequent action in
connection with this appeal may be extended under 37 CFR
§ 1.136(a).
AFFIRMED
EDWARD C. KIMLIN )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
THOMAS A. WALTZ ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
)
)
)
PETER F. KRATZ )
Administrative Patent Judge )
PFK/sld
Appeal No. 2005-1220
Application No. 09/270,606
Page 19
MATTHEW D. RABDAU
SHARP LABORATORIES OF AMERICA, INC.
5750 N.W. PACIFIC RM BLVD
CAMAS, WA 98607