Ex Parte HO et al

Board of Patent Appeals and Interferences

Oct 31, 2002

09048208 (B.P.A.I. Oct. 31, 2002)

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written for publication and is not binding precedent of the Board.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 PAUL KWOK KEUNG HO, THOMAS SCHULUE, RAYMOND JOY,
WAI LOK LEE, RAMASAMY CHOCKALINGAM, BA TUAN PHAM
and PREMACHANDRAN VAYALAKKARA
____________
Appeal No. 2001-1662
Application No. 09/048,208
____________
ON BRIEF
____________
Before WILLIAM SMITH, WALTZ, and POTEATE, Administrative Patent
Judges.
POTEATE, Administrative Patent Judge.
DECISION ON APPEAL
This is an appeal under 35 U.S.C. § 134 from the final
rejection of claims 1-20, which are all of the claims pending in
the application.
Claim 1 is representative of the subject matter on appeal
and is reproduced below:
1. A method of forming metal lines without microloading in the
fabrication of an integrated circuit comprising:
Appeal No. 2001-1662
Application No. 09/048,208
2
providing semiconductor device structures in and on a
semiconductor substrate;
covering said semiconductor device structures with an
insulating layer;
depositing a barrier metal layer overlaying said insulating
layer;
depositing a metal layer overlaying said barrier metal
layer;
covering said metal layer with a layer of photoresist;
exposing said photoresist layer to actinic light and
developing and patterning said photoresist layer to form the
desired photoresist mask wherein there are both wide spaces and
narrow spaces between portions of said photoresist mask;
etching away said metal layer not covered by said
photoresist mask wherein said barrier metal layer is reached
within said wide spaces while some of said metal layer remains
within said narrow spaces;
selectively etching away all of said metal layer remaining
within said narrow spaces;
thereafter etching away said barrier metal layer not covered
by said photoresist mask wherein said insulating layer is reached
within said wide spaces while some of said barrier metal layer
remains within said narrow spaces;
selectively etching away all of said barrier metal layer
remaining within said narrow spaces; and
thereafter overetching said insulating layer not covered by
said photoresist mask to complete said metal lines without
microloading in said fabrication of said integrated circuit.
The reference relied upon by the examiner is:
Abraham et al. 5,883,007 Mar. 16, 1999
Appeal No. 2001-1662
Application No. 09/048,208
3
Ground of Rejection
Claims 1-20 stand rejected under 35 U.S.C. § 103(a) as
unpatentable over Abraham.
We Reverse
Background
In the manufacture of integrated circuits using a metal
etching method, metal lines are formed by depositing a barrier
layer over an oxide layer, followed by deposition of a metal
layer. Specification, page 1. The middle layer is then etched
away in those areas where it is not covered by a mask. Id.
Thereafter, the barrier layer is etched followed by an oxide
etcher over etched. Id.
A common problem which occurs in this conventional method is
that of microloading. Id. Microloading refers to the situation
where an etch rate is slower in areas where there is a high
density of line spacings as compared with the etch rate in less
dense areas. Abraham, column 2, lines 24-28. Microloading may
result in one or more of severe resist loss, poor wafer
planarization and metal shorts at narrow gap regions.
Specification, page 1.
According to the inventors, they have developed a multi-step
etch process having a particular sequence of etching steps which
Appeal No. 2001-1662
Application No. 09/048,208
4
unexpectedly provide improved etching uniformity and reduced
microloading. Appeal brief, Paper No. 20, received November 20,
2000, pages 2-3, paragraph 5. In particular, the inventors have
found that these unexpected results are achieved by completely
removing the metal layer before beginning the barrier layer etch,
and then completely removing the barrier layer before starting
the over etch. id.
Discussion
In deciding patentability issues under 35 U.S.C. § 103,
"[a]nalysis begins with a key legal question -- what is the
invention claimed?" Panduit Corp. v. Dennison Mfg. Co., 810 F.2d
1561, 1567-68, 1 USPQ2d 1593, 1597 (Fed. Cir.), cert denied,
481 U.S. 1052 (1987). According to appellants,
It is a key feature of Appellants' invention to
completely remove all of the metal layer before
beginning the barrier layer etch using an etch that is
selective to the metal layer with respect to the
barrier layer (see Claim 1, lines 25-28 and page 6 of
the Specification, third paragraph) and to completely
remove all of the barrier layer before beginning the
overetch with an etch that is selective to the barrier
layer with respect to the insulating layer (see Claim
1, lines 34-37 and page 7 of the Specification, second
full paragraph).
Appeal brief, page 7, lines 3-12. Thus, appellants maintain
that the invention as claimed distinguishes over Abraham which
does not teach complete removal of the metal layer before
Appeal No. 2001-1662
Application No. 09/048,208
1 The examiner concedes that Abraham does not "expressly
disclose providing a semiconductor structure on or within the
semiconductor substrate and a semiconductor structure include
[sic, including] gate electrodes and source and drain regions" as
required by claim 1. id., page 5. However, appellants do not
dispute the examiner's position that it would have been obvious
to one of ordinary skill in the art at the time of the invention
to have modified Abraham to include these structures. See id.
5
beginning the barrier layer etch or complete removal of the
barrier layer before commencing the overetch. id., page 6.
According to the examiner, this argument is unpersuasive since
these features are not claimed. Examiner's answer, Paper No. 21,
mailed January 19, 2001, page 6.1
In determining the patentability of claims, the PTO gives
claim language its "broadest reasonable interpretation"
consistent with the specification and claims. In re Morris,
127 F.3d 1048, 1054, 44 USPQ2d 1023, 1027 (Fed. Cir. 1997)
(citations omitted). The terms of a claim are generally given
their ordinary meaning unless it appears from the specification
or file history that the inventor intended a special definition.
Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582,
39 USPQ2d 1573, 1576 (Fed. Cir. 1996).
Claim 1 recites a method of forming metal lines without
microloading in the fabrication of an integrated circuit and sets
forth a sequence of steps which are clearly intended to occur in
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Application No. 09/048,208
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chronological order. In other words, it is apparent that each
step is intended to be completed prior to commencement of a
subsequent step. For example, it is clear that the step of
depositing a metal layer overlying said barrier metal layer can
not occur until after the barrier metal layer has been deposited
as recited in the prior step. Similarly, the step of
"selectively etching away all of said metal layer remaining
within said narrow spaces" can not occur until the step of
etching away the metal layer, such that some of the metal layer
remains in the narrow spaces, as recited in the prior step.
We do not find, nor has the examiner identified any teaching
or suggestion in Abraham of a two step etching procedure for
removal of the metal layer wherein, the first etching steps it
leaves a portion of the metal layer within narrow spaces and the
second step "selectively etches" away "all of said metal layer
remaining within said narrow spaces." See claim 1. Abraham
teaches an etching step which proceeds until the metalization
layer has been "substantially etched away." See e.g., column 7,
lines 22-24, column 8, lines 65-9, line 2. Abraham further
teaches that the step of etching the metalization layer may be
continued to ensure complete removal of the metalization layer.
See column 9, lines 8-13. However, the examiner has not
Appeal No. 2001-1662
Application No. 09/048,208
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demonstrated how continuation of the step of etching the
metalization layer in any way discloses or suggest the claimed
two step process wherein the portion of the metal layer remaining
in the narrow spaces from the first etching step is removed in a
subsequent selective etching step.
Similarly, the examiner has not identified any teaching or
suggestion in Abraham which requires the two step etch and
selective etch for removal or the barrier metal layer.
We further note that claim 1 requires that the step of
etching the barrier metal layer does not commence until after all
of the metal layer has been removed from the narrow spaces as
required in the prior step. In particular, we note that the use
of the word "thereafter" clearly signals a subsequent step.
Similarly, the claims require that over etching the insulating
layer does not commence until after the step of selectively
etching away all of the barrier metal layer remaining in the
narrow spaces, as again indicated by use of the word
"thereafter." In fact, Abraham specifically states that
"[a]lthough the second chemistry may [sic, be] extended to etch
through the barrier layer, the third chemistry employed in step
405 may be better suited to etch through the remaining
metalization layer and into an underlying layer." Column 9,
Appeal No. 2001-1662
Application No. 09/048,208
2 Having concluded that a prima facie case of obviousness
does not exist, we need not consider appellants' evidence of
unexpected results, i.e., the declaration of Paul Ho under 37 CFR
§ 1.132.
8
lines 23-27. We note that our interpretation of claims is
consistent with the specification. In particular, the figures
and description thereof, indicate that the recited etching away
of the metal layer to reach the barrier metal layer within the
wide spaces and etching away of the barrier metal layer to reach
the insulating layer are intended to refer to a complete removal
of these materials within the wide spaces. See Figures 2 and 4;
Specification, page 6 ("it can be seen that the metal etch end
point is reached in the wide spaces 33 while in the narrow spaces
32, some of the metal layer still remains.") Page 7 ("the
barrier layer is etched completely through in the wider areas 33
while some of the barrier layer remains within the narrow spaces
32.").
Accordingly, we find that the examiner has failed to
establish a prima facie case of obviousness.2 The rejection is
reversed.

Appeal No. 2001-1662
Application No. 09/048,208
9
REVERSED
WILLIAM F. SMITH )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
THOMAS A. WALTZ ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
)
)
)
LINDA R. POTEATE )
Administrative Patent Judge )
LRP/lbg
Appeal No. 2001-1662
Application No. 09/048,208
10
GEORGE O SAILE
20 MCINTOSH DRIVE
POUGHKEEPSIE, NY 12603
Lesley
Appeal No. 2001-1662
Application No. 09/048,208
APJ POTEATE
APJ WILLIAM SMITH
APJ WALTZ
DECISION: REVERSED

Prepared: September 12, 2003
Draft Final
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