Ex parte Malhi

Board of Patent Appeals and Interferences

Feb 7, 2000

08384816 (B.P.A.I. Feb. 7, 2000)

Application for patent filed February 6, 1995. According to1
appellant, this application is a continuation of Application 08/187,570, filed
January 26, 1994, now abandoned, which is a division of Application
07/559,756, filed July 30, 1990, now U.S. Patent No. 5,294,559.
We observe that on November 12, 1999 (paper no. 24), appellant filed a2
waiver of the oral hearing set for December 6, 1999.
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered today (1) was not
written for publication in a law journal and (2) is not binding
precedent of the Board.
Paper No. 25
UNITED STATES PATENT AND TRADEMARK OFFICE
____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________
Ex parte SATWINDER MALHI
____________
Appeal No. 1997-1624
Application No. 08/384,8161
____________
ON BRIEF2
____________
Before THOMAS, LALL, and GROSS, Administrative Patent Judges.
GROSS, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on appeal from the examiner's final
rejection of claims 19 through 25, which are all of the claims
pending in this application. In the Examiner's Answer, the
Appeal No. 1997-1624
Application No. 08/384,816
2
examiner indicated that claim 24 is now allowable.
Accordingly, only claims 19 through 23 and 25 remain before us
on appeal.
Appellant's invention relates to vertical transistors
having a noncontinuous isolation layer and first and second
insulating portions extending from the top and bottom surfaces
of the semiconductor substrate, respectively, to the
noncontinuous layer for isolating adjacent transistors. Claim
19 is illustrative of the claimed invention, and it reads as
follows:
19. A vertical transistor, comprising:
a semiconductor substrate having top and bottom surfaces;
a noncontinuous isolation layer in the semiconductor
substrate between the top surface and the bottom surface;
a source region formed in the top surface of the
semiconductor substrate above the noncontinuous isolation
layer;
a gate electrode formed above the source region;
a first insulating material extending from the top
surface of the semiconductor substrate to the noncontinuous
isolation layer;
a drain region formed in the semiconductor substrate, a
portion of the noncontinuous isolation layer extending into
the drain region; and
Appeal No. 1997-1624
Application No. 08/384,816
3
a second insulating material extending from the bottom
surface of the semiconductor substrate to the noncontinuous
isolation layer.
The prior art references of record relied upon by the
examiner in rejecting the appealed claims are:
Cogan 4,860,081 Aug. 22,
1989
Tamagawa 5,045,900 Sep. 03,
1991
(effective filing date Oct. 27, 1988)
Claims 19 through 23 and 25 stand rejected under 35
U.S.C.
§ 103 as being unpatentable over Tamagawa in view of Cogan.
Reference is made to the Examiner's Answer (Paper No. 20,
mailed October 31, 1996) for the examiner's complete reasoning
in support of the rejections, and to appellant's Brief (Paper
No. 18, filed May 6, 1996) and Reply Brief (Paper No. 21,
filed January 7, 1997) for appellant's arguments thereagainst.
OPINION
As a preliminary matter we note that appellant indicates
on page 3 of the Brief that the claims are not to stand or
fall together. Appellant, however, discusses claims 19 and 25
together, and, therefore, fails to provide arguments as to the
separate patentability of claim 25 in accordance with 37 CFR
Appeal No. 1997-1624
Application No. 08/384,816
4
§ 1.192(c)(7). Therefore, we will treat claims 19 and 25 as
standing or falling together, with claim 19 as representative,
and each of the remaining claims individually.
We have carefully considered the claims, the applied
prior art references, and the respective positions articulated
by appellant and the examiner. As a consequence of our
review, we will affirm the obviousness rejection of claims 19
through 21 and 25 and reverse the obviousness rejection of
claims 22 and 23.
Appellant contends (Brief, pages 3-4) that neither
Tamagawa nor Cogan discloses a second insulating material
extending from either the bottom surface of the substrate or
the drain region to the noncontinuous isolation layer.
Although Cogan does not explicitly disclose an insulating
material extending from "the bottom surface of the substrate"
to "the noncontinuous isolation layer," Cogan shows a silicon
dioxide material extending vertically through the entire
semiconductor and surrounding each semiconductive element.
Cogan explains (column 2, lines 35-47) that the resulting
structure has each section electrically isolated from each of
the other sections. In view of Cogan, it would have been
Appeal No. 1997-1624
Application No. 08/384,816
5
obvious to isolate the elements of Tamagawa by forming
partitions that extend completely through the semiconductor
substrate. Since Tamagawa already includes trenches for
isolation which extend to the oxide isolation film (62), it
would have been obvious to form the partitions only through
the remainder of the substrate, from oxide isolation film (62)
to the bottom surface of the substrate, which also is the
drain electrode. Accordingly, the combined teachings of
Tamagawa and Cogan include an isolation material extending
from the drain or the bottom surface of the substrate to the
noncontinuous isolation film.
Appellant further argues (Brief, page 4, and Reply Brief,
page 4) that Cogan does not disclose a portion of the
noncontinuous layer extending into the drain region. However,
Cogan need not include a noncontinuous layer extending into
the drain region, since the examiner relies on Tamagawa's film
62 for such a layer. Tamagawa discloses layer 63 as being the
drain region, with 14 being the drain electrode. Since the
drain region and drain electrode must be electrically
connected, the portion of layer 61 between layers 63 and 14
must electrically connect the two and, therefore, also be
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Application No. 08/384,816
6
considered the drain region. Further, since oxide isolation
film (62) extends into the portion of layer 61 between layer
63 and element 14, the isolation film extends into the drain
region, notwithstanding appellant's unsupported statement to
the contrary (Brief, page 5).
The examiner stated at the end of the rejection (Answer,
page 4) that the transistors of Cogan can be replaced by the
power MOSFET of Tamagawa because they are all vertical power
transistors, with no explanation as to the motivation for
making such a substitution. Appellant argues at length
(Brief, pages 5-6) that replacing Tamagawa's MOSFET with
Cogan's devices requires some motivation to do so. We agree.
However, viewing the examiner's response to appellant's
argument (Answer, paragraph bridging pages 5 and 6), we
believe that the examiner was not suggesting a substitution of
one transistor for the other. Rather the examiner was
attempting to demonstrate that the transistors have similar
structures and, therefore, that the teachings of Cogan (for
the isolation structure) can be combined with Tamagawa. As
Cogan suggests the need for isolation between vertical
transistors, Cogan provides motivation for modifying Tamagawa
Appeal No. 1997-1624
Application No. 08/384,816
7
to include an isolation structure that extends through the
entire substrate. Since appellant provides no further
arguments with respect to claims 19 and 25, we will affirm the
rejection thereof.
Appellant further argues (Reply Brief, page 4) that
Tamagawa's noncontinuous layer 62 is not an oxide film because
it does not meet all of the claimed structural requirements
for the layer. This is a non sequitur. The material and the
structure are independent limitations. Tamagawa discloses
that layer 62 is an oxide film regardless of whether the layer
meets other claimed limitations. The structural limitations
allegedly lacking apparently are that Tamagawa does not have
an insulating layer extending from the top surface of the
semiconductor substrate to the noncontinuous isolation layer
where the latter extends into the drain. However, we have
found above that layer 62 does extend into the drain.
Further, insulating element 64 extends form the top surface of
the semiconductor substrate to the noncontinuous layer 62.
Therefore, layer 62 meets the structural limitations and is an
oxide. Accordingly, we will affirm the rejection of claim 20.
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Application No. 08/384,816
8
With respect to claim 21, appellant again argues (Reply
Brief, page 4) that Tamagawa does not disclose the material
since the structure is not met. As explained above, the
structure is met by Tamagawa's element 64. Therefore, we are
unconvinced by appellant's argument, and we will affirm the
rejection of claim 21.
As to claim 22, the examiner asserts (Answer, page 6)
that it would have been obvious to use polymide for the second
isolation material "because it is one of many electrical
isolation materials for electrical isolation in
semiconductor." Appellant contends (Reply Brief, page 4) that
the examiner has not provided motivation for selecting
polymide as the second isolation material. We agree with
appellant that the examiner has failed to provide sufficient
motivation for using polymide instead of the silicon dioxide
disclosed by Cogan. "There must be some reason, suggestion,
or motivation found in the prior art whereby a person of
ordinary skill in the field of the invention would make the
combination." In re Oetiker, 977 F.2d 1443, 1447, 24 USPQ2d
1443, 1446 (Fed. Cir. 1992). Accordingly, we cannot sustain
the rejection of claim 22 and its dependent, claim 23.
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Application No. 08/384,816
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CONCLUSION
The decision of the examiner rejecting claims 19 through
23 and 25 under 35 U.S.C. § 103 is affirmed as to claims 19
through 21 and 25 and reversed as to claims 22 and 23.
Accordingly, the decision of the examiner is affirmed-in-part.
No time period for taking any subsequent action in
connection with this appeal may be extended under 37 CFR
§ 1.136(a).
AFFIRMED-IN-PART
JAMES D. THOMAS )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
PARSHOTAM S. LALL ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
)
)
)
ANITA PELLMAN GROSS )
Administrative Patent Judge )
Appeal No. 1997-1624
Application No. 08/384,816
10
ROBBY T HOLLAND
TEXAS INSTRUMENTS INCORPORATED
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