Ex parte YANG

Board of Patent Appeals and Interferences

Oct 29, 1998

08174723 (B.P.A.I. Oct. 29, 1998)

Application for patent filed December 29, 1993. 1
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not binding precedent of the Board.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. 20
UNITED STATES PATENT AND TRADEMARK OFFICE
____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________
Ex parte CHIA-HUNG YANG
____________
Appeal No. 95-4873
Application No. 08/174,7231
____________
HEARD: October 13, 1998
____________
Before URYNOWICZ, JERRY SMITH and BARRETT, Administrative
Patent Judges.
URYNOWICZ, Administrative Patent Judge.
DECISION ON APPEAL
This appeal is from the final rejection of claims 7-14.
The invention pertains to a resonant-tunneling
transistor. Claim 7 is illustrative and reads as follows:
7. A unipolar, three terminal, resonant-tunneling
transistor, comprising:
a) a first terminal;
b) an insulating barrier on said first terminal;
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c) a first quantum well on said insulating barrier;
d) a first tunneling barrier on said first quantum well;
e) a second quantum well on said first tunneling
barrier;
f) a second tunneling barrier on said second quantum
well;
g) a second terminal on said second tunneling barrier;
and
h) a third terminal on said second tunneling barrier,
where said third terminal is electrically isolated from said
second terminal.
The reference relied upon by the examiner is:
Yang et al. (Yang), “New field-effect resonant tunneling
transistor: Observation of oscillatory transconductance”, Appl.
Phys. Lett. 55(26), Dec. 25, 1989.
The appealed claims stand rejected under 35 U.S.C. §
102(b) as anticipated by or, in the alternative, under 35 U.S.C. §
103 as obvious over Yang.
The respective positions of the examiner and the
appellant with regard to the propriety of these rejections are set
forth in the final rejection (Paper No. 10) and the examiner's
answer (Paper No. 12) and the appellant's brief (Paper No. 11) and
reply brief (Paper No. 13).
Appellant's Invention
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Appellant discloses a resonant-tunneling transistor
wherein a source terminal 7 is electrically connected to a quantum
well 4 when majority carriers from the area of terminal 7 tunnel
through the double-barrier resonant-tunneling barrier 5 to the
quantum well 4. Transistor action is observed when the majority
carriers propagate across the well and tunnel through the
tunneling barrier 5 to the drain terminal 6 in a manner that
results in a DC current gain. The transistor operation is
controlled by a gate terminal 2.
The Prior Art
The reference to Yang discloses a field-effect resonant-
tunneling transistor having a gate terminal (Back Gate), an n+
GaAs substrate, a 2.8Fm undoped AlGaAs and GaAs insulating barrier
on the substrate, a 200Å n+ GaAs quantum well on the insulating
barrier, a three layer, double-barrier, tunneling barrier on the
quantum well, the tunneling barrier consisting of two 30Å undoped
Al Ga As barriers sandwiching a 70Å GaAs layer, a 1500Å n+ GaAs0.37 0.63
layer on the tunneling barrier and a capping layer on the 1500Å
layer. A source terminal is located on the top of the structure.
A drain terminal extends from the top of the structure through
several layers of the transistor into the quantum well.
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The Rejections
We note that appellant has not specifically argued the
patentability of any specific dependent claim, indicating how it
defines appellant’s invention over the prior art. Accordingly,
appellant’s dependent claims 8-10 stand or fall with independent
claim 7 and dependent claims 12-14 stand or fall with independent
claim 11. In re Nielson, 816 F.2d 1567, 2 USPQ2d 1525 (Fed. Cir.
1987).
With respect to claims 7-14, appellant argues, among
other things, that the third terminal of the reference, the drain,
is not disclosed as being on the second tunneling barrier and that
the reference has only one tunneling structure, that under the
source, because the region beneath the drain (Ti/Pt/Au) is doped
and is part of the drain.
Appellant’s reply to the examiner’s answer includes an
affidavit of the inventor to the effect that the reference has
only one tunneling barrier.
The examiner answers broadly that the claims do not
recite tunnel structures but rather tunnel barriers, and that the
claimed structure reads on the prior art regardless of the doping
beneath the drain.
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Application No. 08/174,723
It is not clear from appellant’s specification that the 100Å2
layer of undoped GaAs located between the two 30Å layers of
undoped Al Ga As, which three layers form the undoped double-0.4 0.6
barrier resonant tunneling barrier 5, is a quantum well. However,
we have concluded that this is the case from the construction of
independent claims 7 and 11, and the fact that dependent claims 8
an 12 indicate that the second quantum well, like the first, is
comprised of GaAs.
5
We will not sustain the rejections of claims 7-14 over
the reference to Yang .2
With respect to Fig. 1(a) of the reference, we agree
with appellant that there is no tunneling barrier in the area of
the drain of the reference which might be considered the second
tunneling barrier of the claims. This is because of the n+ Si
implant utilized to form the drain region, which region extends
down into the 200Å n+ GaAs quantum well. The Yang publication
discloses that the silicon implant is used to make shallow ohmic
contacts to define the drain region. The only reference to
tunneling is under the source terminal; tunneling is indicated by
the hollow arrow under the source terminal of Fig. 1(a).
However, irrespective of the above analysis of the
reference's disclosure, the first and second tunneling barriers of
the claims read on those portions of the two 30Å layers of the
double-barrier tunneling barrier under the source. The lower 30Å
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layer of the reference is a first tunneling barrier on the first
quantum well, identified as 200Å n+ GaAs QW. The upper 30Å layer
is a second tunneling barrier on the second quantum well, which is
the 70Å layer of GaAs sandwiched between the two 30Å layers.
Nevertheless, although the source terminal of the publication is a
second terminal on the second tunneling barrier, the drain
terminal of the reference cannot be the third terminal of the
claims because the drain terminal is not on the second tunneling
barrier. As indicated above, the n+ Si implant eliminates the
possibility of a second tunneling barrier under the drain. In the
area of the drain, the layer forming the second tunneling barrier
under the source becomes part of the drain terminal itself. For
the reasons given above, the rejection under 35 U.S.C. § 102
cannot be sustained.
Because the examiner has provided no motivation why one
of ordinary skill in the art would have modified the prior art by
eliminating the implant so that the drain terminal would be on the
upper 30Å layer, the rejection under 35 U.S.C. § 103 cannot be
sustained.
REVERSED
Appeal No. 95-4873
Application No. 08/174,723
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STANLEY M. URYNOWICZ, JR. )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
JERRY SMITH ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
)
)
)
LEE E. BARRETT )
Administrative Patent Judge )
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DIRNSA
ATTN: BOB MORELLI, GC R/E
FT. MEADE, MD 20755-6000