Ex Parte Lee

Board of Patent Appeals and Interferences

Aug 23, 2006

10254326 (B.P.A.I. Aug. 23, 2006)

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The opinion in support of the decision being
entered today was not written for publication
and is not binding precedent of the Board
___________

UNITED STATES PATENT AND TRADEMARK OFFICE
___________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
___________

Ex parte THOMAS H. LEE
___________

Appeal No. 2006-1545
Application 10/254,3261
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ON BRIEF
___________

Before HAIRSTON, JERRY SMITH, and BARRETT, Administrative Patent
Judges.

BARRETT, Administrative Patent Judge.

DECISION ON APPEAL
This is a decision on appeal under 35 U.S.C. § 134(a) from
the final rejection of claims 42-56.
We reverse.

BACKGROUND
The invention relates to a steering element (a PN diode) and
a state change element (a dielectric rupture antifuse)
electrically connected between two conductors forming a
nonvolatile memory cell. The steering element is a

1 Application for patent filed September 25, 2002, entitled
"Diverse Band Gap Energy Level Semiconductor Device," which is a
division of Application 10/077,108, filed February 15, 2002.
Appeal No. 2006-1545
Application 10/254,326

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heterojunction PN diode formed from two semiconductor materials
having different band gap energy levels, which increases the
forward-to-reverse current ratio.
Claim 42 is reproduced below.
42. A semiconductor structure comprising:

a first conductor and a second conductor;

a steering element in circuit communication with the
first conductor and comprising at least first and second
semiconductor materials, the first semiconductor material
having a first band gap energy level, the second
semiconductor in electrical communication with the first
semiconductor and having a second band gap energy level,
wherein the second band gap energy level is different from
the first band gap energy level; and

a state change element in circuit communication with
the steering element and the second conductor and comprising
a selectable high impedance state and a selectable low
impedance state.

Appeal No. 2006-1545
Application 10/254,326

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THE REFERENCES

The examiner relies on the following references:

Fang et al. (Fang) 5,670,414 September 23, 1997
Zhang 5,835,396 November 10, 1998

Shimogaki et al. JP 10079521 March 24, 1998
(Shimogaki)

THE REJECTIONS
Claims 42-46, 53, and 56 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over Zhang and Shimogaki. The
examiner finds that Zhang discloses a memory device with first
and second conductors; a steering element with first and second
semiconductor layers forming a PN diode; and an antifuse. The
examiner finds that Zhang does not disclose the semiconductor
layers forming the PN diode having different band gap energy
levels, but that Shimogaki discloses that a heterojunction PN
diode shows enhanced rectification characteristics. The examiner
concludes that it would have been obvious to use the
heterojunction diode of Shimogaki in Zhang to enhance operation.
Claims 47-52, 54, and 55 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over Zhang and Fang. Since these
claims depend directly or indirectly from claim 42, we assume the
rejection is over Zhang, Shimogaki, and Fang.
We refer to the final rejection and the examiner's answer
(pages referred to as "EA__") for a statement of the examiner's
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Application 10/254,326

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rejection, and to the brief (pages referred to as "Br__") and
reply brief (pages referred to as "RBr__") for a statement of
appellant's arguments thereagainst.

DISCUSSION
The rejection and arguments based on the rejection of Zhang
and Shimogaki are almost identical to those in the previous Board
decision in Ex parte Lee, Appeal No. 2005-0723, Application
10/254,123, entered August 30, 2005. We incorporate the
reasoning of that decision by reference. We found in that
opinion that Shimogaki discloses a diamond lone particle grown in
contact with an N-type silicon substrate to form a heterojunction
diode, which teaches that the diode is formed of two single-
crystal materials. We agreed with appellant that one skilled in
the art would not have been motivated to substitute the diode
formed of single crystals in Shimogaki for the diode formed of
polycrystalline or amorphous semiconductors in Zhang because the
differences in behavior, properties, compatibility, and
manufacturing techniques argue against the successful
combination. That is, the examiner has picked a diode
implementation in Shimogaki that is not capable of being
physically combined with or substituted into Zhang, based on the
fact that it is a heterojunction diode as needed in the claims.
This evidences a lack of motivation to combine. The claims do
Appeal No. 2006-1545
Application 10/254,326

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not require that first and second semiconductor materials are
polycrystalline or amorphous (Br9 n.1), but the materials must
form a heterojunction device and must be joined to first and
second conductors and a state change element.
We look at the examiner's arguments that deal with the
physical combinability of Zhang and Shimogaki.
The examiner states (EA4-5):
First, note that the rejection shows that Zhang is modified
by Shimogaki et al. and that modified device would include a
polycrystalline heterojunction device. Note that Zhang
shows a method of forming the structure which depends on
forming the poly material in holes. However, there is an
extensive literature and a large number of patents that show
that polycrystalline silicon can be formed into essentially
single crystal structure using catalysts and laser
annealing. [T]he process involves forming an amorphous
silicon layer, depositing a catalytic element, heat treating
to crystallize and then laser annealing the structure to
form near perfect single crystal material. Thus it is well
within the state of the art to turn the Zhang devices into
single crystal devices.

That is, the examiner says that the proposed modification of
Zhang by Shimogaki includes a polycrystalline heterojunction
device even though Shimogaki is not a polycrystalline device.
The examiner then states that it was known how to turn the Zhang
polycrystalline devices into single crystal devices, evidently to
be compatible with Shimogaki.
Appellant argues that the examiner has not cited any art
teaching the techniques, the techniques are not cited in either
reference, and no one could be certain of their success (RBr3).
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It is argued that the formation of such a device is not obvious
from the cited references because nothing in Zhang teaches or
suggests the utility or desirability of the use of catalytic or
laser annealing techniques, or the need to increase the grain
size in the polycrystalline diode of Zhang by any means (RBr3).
It is argued that these techniques are not taught in Shimogaki,
which uses epitaxial growth that is impossible in Zhang (RBr4).
"Appellants respectfully maintain that the mere existence of
techniques does not render obvious their use in an unrelated
context." (RBr4).
We agree with appellant that there is no suggestion in the
references to modify Zhang as proposed by the examiner. The
possibility that Zhang could be modified to provide a single
crystal device using techniques that are not taught or suggested
in either of the references is mere speculation, which is
insufficient to support an obviousness conclusion. We cannot
uphold an obviousness determination based on evidence that is not
of record and not applied in the rejection.
The examiner states that it was well known in the art that
the Zhang process could be easily modified to provide a
monocrystalline device (EA6, three places). Again, there is no
evidence cited for this finding and nothing in Zhang suggests
that it should be done.
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Application 10/254,326

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The examiner states that "it is not necessary that a
monocrystalline device be formed since the benefits shown by
Shimogaki et al. only require the relative bandgaps" (EA6) and
there is no reason why heterojunction devices cannot be
polycrystalline (EA6, two places).
Appellant replies "that the Examiner is here suggesting that
it would have been obvious to take a single aspect of Shimogaki
et al. (that of using different semiconductor materials having
different band gap energies) in isolation from, and even in
contradiction of, all of the other teachings of Shimogaki et al.,
then apply such teaching to the array of Zhang" (RBr5). It is
argued that the teachings of the heterojunction art cited by
appellant attest to the importance of the use of monocrystalline
materials and lattice matching in conventional heterojunction
diodes and appellant has not been able to find any teaching that
the heterojunction diodes of Shimogaki could as easily be
polycrystalline as monocrystalline (RBr5-6).
Basically, the examiner has not produced any evidence of a
heterojunction PN device made from polycrystalline material that
could be substituted for the PN device in Zhang. Merely saying
that it would be obvious to substitute a heterojunction PN device
for the PN device in Zhang for the increased efficiency does not
show how such a device would be made. Since appellant does not
disclose how a heterojunction diode would be made using
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polycrystalline or amorphous material, it is assumed that the
technique is within the level of ordinary skill in the art.
However, where, as here, appellant is arguing that conventional
heterojunction devices are lattice matched single crystals, and
"[t]he polycrystalline heterojunction diode the Examiner imagines
is not taught in either reference, or in any reference of record,
and is not conventional" (Br9), some evidence is required. The
examiner also has not provided any evidence that the claimed
combination with the heterojunction diode could be made using
single crystals, and there is no suggestion in Zhang that it
would have been desirable to use single crystals. We conclude
that the examiner has failed to establish a prima facie case of
obviousness. The rejection of claims 42-46, 53, and 56 is
reversed. Fang does not cure the deficiencies of Zhang and
Shimogaki and, therefore, the rejection of claims 47-52, 54, and
55 is also reversed.
Appeal No. 2006-1545
Application 10/254,326

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REVERSED

KENNETH W. HAIRSTON )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
JERRY SMITH ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
)
)
)
LEE E. BARRETT )
Administrative Patent Judge )
Appeal No. 2006-1545
Application 10/254,326

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