Ex Parte Smith

Board of Patent Appeals and Interferences

Apr 28, 2004

08866456 (B.P.A.I. Apr. 28, 2004)

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not written for publication and is not binding precedent of the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. 44
UNITED STATES PATENT AND TRADEMARK OFFICE
__________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________
Ex parte GREGORY C. SMITH
__________
Appeal No. 2004-0859
Application 08/866,456
___________
ON BRIEF
___________
Before PAK, OWENS and PAWLIKOWSKI, Administrative Patent Judges.
OWENS, Administrative Patent Judge.
DECISION ON APPEAL
This appeal is from the final rejection of claims 29-47.
Claims 48-52, which are all of the other claims pending in the
application, stand withdrawn from consideration by the examiner
as being directed toward a nonelected invention.
Appeal No. 2004-0859
Application 08/866,456

2
THE INVENTION
The appellants claim a structure for electrically connecting
levels of a semiconductor device. Claim 39 is illustrative:
39. An electrical connection structure for an integrated
circuit device, comprising:
a first conductive layer;
an insulating layer overlying the first conductive layer,
the insulating layer having an upper surface and an opening
exposing a region of the first conductive layer, the opening
being defined by a side-wall of the insulating layer and having a
lower diameter adjacent the first conductive layer and a larger,
upper diameter at a top portion thereof adjacent the upper
surface of the insulating layer, the lower and upper diameter
portions having been made using the same mask and being self-
aligned with respect to each other and thus assured of having
their respective centers aligned with each other;
a thin barrier layer covering the side-wall of the
insulating layer within the opening and the first conductive
layer region exposed within the opening;
a conductive plug overlying the barrier layer and filling
the opening in the insulating layer, the plug having a lower
diameter adjacent the first conductive layer and a larger, upper
diameter adjacent the upper surface of the insulating layer, the
upper diameter of the plug being larger than the lower diameter
of the opening and the barrier layer being of a material that is
selectively etchable with respect to the plug such that the upper
portion of the plug is an etch stop that prevents etching of the
barrier layer adjacent the bottom portion of the contact opening
during any subsequent anisotropic etches; and
a second conductive layer overlying at least a portion of
the plug and being of material that is selectively etchable with
respect to the plug.
Appeal No. 2004-0859
Application 08/866,456

1 Rejections under 35 U.S.C. § 103 of claims 29-31, 33-37,
39-42 and 44-47 over Lur in view of Sato and Wolf
(U.S. 4,495,220), claim 32 over Lur in view of Sato, Wolf and
Liou, claims 38 and 43 over Lur in view of Sato, Wolf and Kim,
and claims 29-31, 33-37, 39-42 and 44-47 over Sato in view of
Wolf are withdrawn in the examiner’s answer (page 3).
3
THE REFERENCES
Liou et al. (Liou) 5,070,391 Dec. 3, 1991
Liu et al. (Liu) 5,180,689 Jan. 19, 1993
Sato 5,284,799 Feb. 8, 1994
Lur et al. (Lur) 5,364,817 Nov. 15, 1994
Kim 5,530,294 Jun. 25, 1996
THE REJECTIONS
The claims stand rejected under 35 U.S.C. § 103 as follows:
claims 29-31, 33-37, 39-42 and 44-47 over Lur in view of Sato and
Liu, claims claim 32 over Lur in view of Sato, Liu and Liou,
claims 38 and 43 over Lur in view of Sato, Liu and Kim, and
claims 29-31, 33-37, 39-42 and 44-47 over Sato in view of Liu.1
OPINION
We reverse the aforementioned rejections. We need to
address only the independent claims, i.e., claims 29, 39 and 44.
Each of the independent claims requires a conductive layer
and an insulating layer overlying the conductive layer, wherein
the insulating layer has therein an opening having a lower
portion and a larger-diameter upper portion. In claim 29 the
lower portion has generally straight side walls extending
Appeal No. 2004-0859
Application 08/866,456

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upwardly from the first conductive layer and the upper portion is
bowled upwardly and outwardly from the lower portion to the upper
surface of the insulating layer. In claim 39 the lower portion
has a diameter adjacent the conductive layer which is smaller
than the diameter of the upper portion at the surface of the
insulating layer. In claim 44 the lower portion has a steeper
side wall than the upper portion.
For the appellant’s claim requirement of an insulating layer
having an opening with a lower portion and a larger-diameter
upper portion, the examiner relies (answer, pages 5-8) upon Sato
which discloses a first conductive layer (lower wire 12) having
thereover an insulating layer (13) with an opening therethrough
(col. 4, line 67 - col. 5, line 45). The opening has a lower
portion adjacent the substrate and a larger-diameter upper
portion (figure 4D). These portions are formed by two successive
lithographic processes which are not described (col. 5, lines 2-
7). The disclosed benefit of these portions is that even if an
adhesion layer (15) which lines the opening, and a blanket
tungsten layer (16) which fills the opening, are overetched when
they are etched back, the overetching does not extend downwardly
beyond the upper, wider portion of the opening (col. 5, lines 39-
42). Hence, “[t]he metal plug 16A thus formed is highly
Appeal No. 2004-0859
Application 08/866,456

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reliable, and does not adversely affect the step coverage of the
subsequently formed upper wire 17, with resultant good multilayer
wires” (col. 5, lines 42-45; figure 4D).
The appellant’s independent claims also require that the
lower and upper opening portions are self aligned with each
other. The examiner points out that this is a product-by-process
limitation (answer, pages 17-20). The examiner, however, does
not provide evidence or reasoning which shows that Sato’s two
successive lithographic processes produce a product which is
identical or substantially identical to one having lower and
upper opening portions which are self aligned. See In re
Fitzgerald, 619 F.2d 67, 70, 205 USPQ 594, 596 (CCPA 1980); In re
Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433-34 (CCPA 1977); In
re Fessmann, 489 F.2d 742, 745, 180 USPQ 324, 326 (CCPA 1974).
Instead, the examiner relies upon Liu for a suggestion to make
Sato’s lower and upper opening portions self aligned (answer,
pages 6 and 8). Liu discloses a method for making a tapered
opening through an insulating layer (20) to an underlying
source/drain region (12) (col. 4, lines 42-55). Liu sequentially
1) anisotropically etches the insulating layer through an opening
in a resist mask to form an opening in the insulating layer,
2) using the same mask, isotropically etches the insulating layer
Appeal No. 2004-0859
Application 08/866,456

6
to substantially uniformly enlarge and taper the opening in the
insulating layer, and 3) anisotropically etches the opening in
the insulating layer through to the source/drain regions (col. 2,
line 61 - col. 3, line 4; col. 4, line 66 - col. 5, line 27).
Liu states that this method forms a tapered opening with a metal
step coverage improvement over the state of the art of about 20-
60%, where metal step coverage is “the ratio of thickness of the
thinnest metal in the contact hole to the metal thickness on the
horizontal area” (col. 3, lines 5-9). This step coverage is
shown in Liu’s figures 4-6 wherein metal layer 36 fills the lower
portion of the opening and covers metal layer 34 which lines the
opening, but does not fill the opening’s upper portion.
The examiner argues that it would have been obvious to one
of ordinary skill in the art to use Liu’s method to form the
lower and upper portions of Sato’s opening to improve step
coverage of a metal wiring layer at the opening (answer, pages 6,
8, 13 and 15-16). Unlike Liu, however, Sato completely fills the
opening with metal and then etches back the metal to the
insulating layer upper surface (col. 5, lines 10-17). The
examiner has not established that one of ordinary skill in the
art would have been led by the applied references to use Liu’s
technique, which only partially fills the opening with metal, to
Appeal No. 2004-0859
Application 08/866,456

2 The examiner does not rely upon Lur, Liou or Kim for any
disclosure that remedies the above-discussed deficiency in Sato
and Liu as to the independent claims.
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obtain the complete filling of the opening with metal desired by
Sato.2 The record indicates that the motivation for doing so
relied upon by the examiner comes from the appellant’s disclosure
rather than coming from the applied prior art and that,
therefore, the examiner used impermissible hindsight when
rejecting the claims. See W.L. Gore & Associates v. Garlock,
Inc., 721 F.2d 1540, 1553, 220 USPQ 303, 312-13 (Fed. Cir. 1983),
cert. denied, 469 U.S. 851 (1984); In re Rothermel, 276 F.2d 393,
396, 125 USPQ 328, 331 (CCPA 1960). Accordingly, we reverse the
examiner’s rejections.
Appeal No. 2004-0859
Application 08/866,456

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DECISION
The rejections under 35 U.S.C. § 103 of claims 29-31, 33-37,
39-42 and 44-47 over Lur in view of Sato and Liu, claims claim 32
over Lur in view of Sato, Liu and Liou, claims 38 and 43 over Lur
in view of Sato, Liu and Kim, and claims 29-31, 33-37, 39-42
and 44-47 over Sato in view of Liu, are reversed.

)
CHUNG K. PAK )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
TERRY J. OWENS )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
BEVERLY A. PAWLIKOWSKI )
Administrative Patent Judge )
TJO/ki
Appeal No. 2004-0859
Application 08/866,456

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