Ex Parte Brabec et al

Board of Patent Appeals and Interferences

Jul 15, 2003

09303020 (B.P.A.I. Jul. 15, 2003)

1
The opinion in support of the decision being entered today was
not written for publication and is not binding precedent of the
Board.
Paper No. 22
UNITED STATES PATENT AND TRADEMARK OFFICE
__________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________
Ex parte SCOTT J. BRABEC, KENNETH R. BRENNEN,
WILLIAM J. SCHNINDELDECKER STANTEN C. SPEAR, ROGER E. RUGLAND
and BRUCE C. JOHNSON
__________
Appeal No. 2002-0897
Application 09/303,020
___________
ON BRIEF
___________
Before OWENS, WALTZ, and LIEBERMAN, Administrative Patent Judges.
OWENS, Administrative Patent Judge.
DECISION ON APPEAL
This appeal is from the final rejection of claims 1-20,
which are all of the claims remaining in the application.
THE INVENTION
The appellants claim a method for forming a structure having
a cavity within a semiconductor wafer. Claim 1 is illustrative:
1. A method of forming a structure in and on a
semiconductor wafer, comprising the steps of:
Appeal No. 2002-0897
Application 09/303,020
1 Rejections of claims 1-10 under 35 U.S.C. § 112, first
paragraph, and claims 1-20 under 35 U.S.C. § 103 over
U.S. 5,779,520 to Hayakawa taken with Doan and Kirlin are
withdrawn in the examiner’s answer (page 2).
2
forming a layer on a top surface of the semiconductor wafer and
within a cavity formed in the wafer such that at least a portion
of the cavity remains open;
polishing a portion of the layer formed above a plane
defined approximately by a top surface of the semiconductor
wafer;
megasonically cleaning the semiconductor wafer including the
open portion of the cavity; and
brush scrubbing the semiconductor wafer to clean the open
portion of the cavity.
THE REFERENCES
Doan et al. (Doan) 5,391,511 Feb. 21, 1995
Kirlin et al. (Kirlin) 5,976,928 Nov. 2, 1999
(filed Nov. 20, 1997)
Roy et al. (Roy) 5,996,594 Dec. 7, 1999
(effective filing date Nov. 30, 1994)
THE REJECTION
Claims 1-20 stand rejected under 35 U.S.C. § 103 as being
unpatentable over Doan taken with Roy and Kirlin.1
OPINION
We affirm the aforementioned rejection.
The appellants state that the claims stand or fall together
(brief, page 3). We therefore limit our discussion to one claim,
Appeal No. 2002-0897
Application 09/303,020
3
i.e., claim 1. See In re Ochiai, 71 F.3d 1565, 1566 n.2, 37
USPQ2d 1127, 1129 n.2 (Fed. Cir. 1995); 37 CFR
§ 1.192(c)(7)(1997).
Doan discloses a method of forming a structure in and on a
semiconductor wafer, comprising forming a layer (22) on a top
surface (26) of the semiconductor wafer and within a cavity (24)
formed in the wafer such that at least a portion of the cavity
remains open (col. 3, lines 19-22; figure 5), chemical mechanical
polishing (CMP) a portion of the layer formed above a plane
defined approximately by a top surface of the semiconductor wafer
(col. 3, lines 23-35; figure 6), and megasonically cleaning the
semiconductor wafer including the open portion of the cavity
(col. 3, lines 36-59). Doan does not disclose brush scrubbing
the wafer. Doan, however, teaches that “[o]ther techniques are
also expected to be usable to remove chemical mechanical
polishing slurry residuals from the outwardly open polysilicon
cavity” (col. 4, lines 12-15).
Roy discloses a post-CMP process which includes
megasonically cleaning a wafer and then brush scrubbing the wafer
to further remove particles and ionic and metallic contaminants
(col. 3, lines 10-16; col. 4, lines 23-25; col. 5, lines 22-39).
Roy does not disclose applying the process to a surface having a
Appeal No. 2002-0897
Application 09/303,020
4
cavity therein. Roy describes the process only in conjunction
with a CMP cleanup process for interlevel dielectric films, but
states that “[i]t will be apparent to those skilled in the art
that the invention is also applicable to CMP of other films, such
as metal films including tungsten, aluminum, and copper
damascene” (col. 2, lines 53-57).
The appellants argue that “Roy et al. teaches ‘a CMP cleanup
process for interlevel dielectric films’ (col. 2, lines 52-55)
and specifically relate[s] to overcoming the problem of
‘agglomeration (gelling) of silica particles after polishing’
caused by drying of the silica particles and resulting bonding of
the particles to the surface of the wafer (see col. 1, lines 40-
52; col. 2, lines 52-54). Thus, Roy et al. does not relate to
cleaning an open portion of a cavity, as claimed” (brief,
page 14). The appellants also argue that “there is no cognizable
motivation within Roy et al. or Doan et al. to substitute or
complement the cleaning methods of Doan et al. with the cleaning
methods in Roy et al., as Roy et al. relates specifically to a
problem of silica bonding on interlevel dielectric films caused
by the drying of wafers following CMP” (brief, pages 14-15).
Appeal No. 2002-0897
Application 09/303,020
5
Contrary to the appellants’ argument, Roy does not limit his
process to interlevel dielectric films but, rather, indicates
that the process is applicable to CMP of other films (col. 2,
lines 54-57). Hence, the appellants’ argument that Roy
“relate[s] particularly to planarization of interlevel dielectric
films” (reply brief, page 2) is not well taken.
As for the appellants’ argument that Roy’s process is
specifically directed toward preventing the CMP silica particles
from drying and thereby gelling and bonding to the surface of the
wafer, Roy teaches that the wafer surface is preferably kept wet
throughout the cleanup process to prevent such gelling and
bonding, but does not indicate that the disclosure is limited to
a process for preventing that gelling and bonding (col. 4,
lines 32-40).
The appellants argue that “there is no reasonable
expectation of success provided in the prior art (i.e., absent
the benefit of Appellant’s disclosure) that the addition of brush
scrubbing of Roy et al. to the process of Doan et al. would clean
an open portion of a cavity. Moreover, the teachings of both
Roy et al. and Doan et al. fail to support the Examiner’s
Appeal No. 2002-0897
Application 09/303,020
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conclusion that the brush scrubbing of Roy et al. would
necessarily clean an open portion of a cavity provided by
Doan et al.” (reply brief, pages 2-3).
The reasonable expectation of success in using Roy’s brush
scrubbing to clean particles out of Doan’s open cavity would have
been provided to one of ordinary skill in the art by Roy’s
teaching that his post-CMP cleanup process is applicable to CMP
of films other than interfacial dielectric films (col. 2,
lines 53-56). This teaching would have indicated to one of
ordinary skill in the art that Roy’s brush scrubbing is
applicable to CMP of films generally, including both smooth and
cavity-containing films.
Regarding the appellants’ argument that the references do
not indicate that Roy’s brush scrubbing necessarily would clean
particles out of Doan’s open cavity, we note that both the
appellants (specification, page 8, lines 12-13) and Roy (col. 5,
lines 29-30; col. 6, lines 15-18) appear to use conventional
wafer layer cleaning brushes. Due to this apparent similarity of
the brushes, it reasonable appears that the brushes provide the
same or substantially the same effect. See In re Spada, 911 F.2d
705, 708, 15 USPQ2d 1655, 1657-58 (Fed. Cir. 1990).
Appeal No. 2002-0897
Application 09/303,020
2 Hence, we are not persuaded by the appellants’ argument
that one of ordinary skill in the art would have been led by Doan
and Roy to use only variants of the HF process and not brushing
to remove particles from an open portion of a cavity in a
semiconductor wafer (reply brief, page 3).
7
The appellants argue (reply brief, page 3):
Roy et al. teach “[t]he HF spray after scrubbing
removes metal contaminants to below detection limits”
(Roy et al., col. 6, lines 30-32)(emphasis added). If
anything, Roy et al. suggest[s] on its face that the
brush scrubbing and megasonic cleaning (col. 5,
lines 22-36) fail to accomplish the task of cleaning
the surface of the wafer and require a HF spray to
remove the residuals (col. 6, lines 30-32). Appellants
respectfully submit that one skilled in the art would
conclude from Roy et al. that since brush scrubbing is
not able to remove all residuals from a flat surface
(col. 6, lines 30-32), it would not effectively clean
an open cavity in a semiconductor wafer.
Actually, what Roy discloses is that “[t]he HF spray after
scrubbing removes most of the metal contaminants to below
detection limits” (col. 6, lines 30-32). Thus, Roy indicates
that some residuals remain even after the HF spray. Roy teaches
that each of the steps contributes to the removal of unwanted
particles from the wafer surface (col. 6, lines 35-37). One of
ordinary skill in the art, therefore, would not have been
discouraged by Roy from using brush scrubbing to remove particles
from a cavity-containing surface.2
Appeal No. 2002-0897
Application 09/303,020
8
The appellants argue that each of Doan’s claims requires an
HF dip (reply brief, page 3). This argument is not well taken
because Doan’s disclosure is not limited to the claims. Instead,
all of Doan’s disclosures must be evaluated for what they would
have fairly suggested to one of ordinary skill in the art. See
In re Boe, 355 F.2d 961, 965, 148 USPQ 507, 510 (CCPA 1966).
The appellants argue that one of ordinary skill in the art
would not have used Roy’s brush scrubbing in Doan’s method
because the benefits of brush scrubbing do not clearly outweigh
the disadvantages of adding a new and different process step
(reply brief, page 4). This argument is unpersuasive because it
is not supported by evidence. Arguments of counsel cannot take
the place of evidence. See In re De Blauwe, 736 F.2d 699, 705,
222 USPQ 191, 196 (Fed. Cir. 1984); In re Payne, 606 F.2d 303,
315, 203 USPQ 245, 256 (CCPA 1979); In re Greenfield, 571 F.2d
1185, 1189, 197 USPQ 227, 230 (CCPA 1978); In re Pearson, 494
F.2d 1399, 1405, 181 USPQ 641, 646 (CCPA 1974). Moreover, the
appellants have not established that benefits of a process step
must clearly outweigh its disadvantages for a prima facie case of
obviousness of a method including that step to be established.
Appeal No. 2002-0897
Application 09/303,020
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The appellants argue that Roy uses a low concentration HF
spray containing 0.25-1.0 wt% HF, whereas Doan’s required HF dip
uses a higher HF concentration of 5-100 parts by volume of a
49% HF solution per volume of water, and that Roy’s brush
scrubbing does not lend itself to Doan’s method which requires
much more intense HF processing (reply brief, pages 4-5).
Actually, both Roy (col. 5, lines 36-38) and Doan (col. 3,
lines 60-62) indicate that the HF treatment is optional.
Regardless, Roy’s teaching that brush scrubbing is effective for
removing particles and ionic and metallic contaminants (col. 5,
lines 38-39) would have fairly suggested, to one of ordinary
skill in the art, use of brush scrubbing with Doan’s megasonic
cleaning and optional HF treatment to further clean the layer
surface.
The appellants argue that a comparison of split conditions
“B” and “D” in Roy’s figure 13 indicates that Roy’s HF spray,
when used in combination with brush scrubbing, appears relatively
ineffective for reducing total defect counts (reply brief,
page 5). Roy teaches that figure 13 indicates that the HF spray
after scrubbing removes most of the metal contaminants to below
detection limits (col. 6, lines 30-32), and figure 13 shows that
the average total defect count when brush scrubbing is used alone
Appeal No. 2002-0897
Application 09/303,020
3 A discussion of Kirlin, which is relied upon by the
examiner for a disclosure of the barrier layer required by the
appellants’ dependent claim 17 (answer, page 3), is not necessary
to our decision.
10
is comparable to that obtained when brush scrubbing and HF are
used in combination (i.e., about 58 counts versus about
50 counts). Consequently, this figure would have indicated to
one of ordinary skill in the art that brush scrubbing, whether
used alone or in combination with HF, is effective for reducing
the total defect count to at or near the below-detection level.
For the above reasons we are not convinced of reversible
error in the examiner’s conclusion that it would have been prima
facie obvious to one of ordinary skill in the art to use Roy’s
brush scrubbing in Doan’s post-CMP cleanup method. For this
reason and because the appellants have not provided evidence of
secondary considerations for overcoming the prima facie case of
obviousness, we affirm the examiner’s rejection.3
Appeal No. 2002-0897
Application 09/303,020
11
DECISION
The rejection of claims 1-20 under 35 U.S.C. § 103 over Doan
taken with Roy and Kirlin is affirmed.
No time period for taking any subsequent action in
connection with this appeal may be extended under 37 CFR
§ 1.136(a).
AFFIRMED
TERRY J. OWENS )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
THOMAS A. WALTZ )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
PAUL LIEBERMAN )
Administrative Patent Judge )
TJO:pgg
Appeal No. 2002-0897
Application 09/303,020
12
Girma Wolfe-Michael
Medtronic Inc.
7000 Central Avenue NE
Minneapolis, MN 55432