Ex parte Tsuji

Board of Patent Appeals and Interferences

Apr 19, 1999

08172051 (B.P.A.I. Apr. 19, 1999)

Application for patent filed December 23, 1993.1
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(2) is not binding precedent of the Board.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 KENJI TSUJI

_____________
Appeal No. 95-3885
Application 08/172,0511
______________
HEARD: April 5, 1999
_______________
Before BARRETT, FLEMING and HECKER, Administrative Patent
Judges.
FLEMING, Administrative Patent Judge.
Appeal No. 95-3885
Application 08/172,051
2
DECISION ON APPEAL
This is a decision on appeal from the final rejec-
tion of claims 1, 3 and 5 through 8, all of the claims pending
in the present application. Claims 2 and 4 have been can-
celed.
The invention relates to a diode suited for absorb-
ing a surge utilizing a high resistivity layer to heat the pn
junction during overcurrent so as to cause a secondary break-
down of the diode whereby a surge current is absorbed by
utilizing Zener breakdown of the pn junction.
The independent claim 1 is reproduced as follows:
1. A diode comprising:
a semiconductor substrate;
a pn junction provided in the semiconductor
substrate; and
an exothermic body for heating the pn junction
under an overcurrent, said exothermic body being provided in a
neighborhood of the pn junction wherein the exothermic body is
a semiconductor layer formed below the pn junction.
Appeal No. 95-3885
Application 08/172,051
3

The Examiner relies on the following references:
Shockley 3,286,138 Nov. 15, 1966
Richard S. Muller and Theodore I. Kamins, Device Electronics
for Integrated Circuits, 257 (2nd ed., New York, John Wiley &
Sons, 1986).
John Gosch, "Temperature Range of Silicon Sensors Tops 350EC
Mark," Electronics, 73-74 (May 5, 1982).
Claims 1, 3 and 5 through 8 stand rejected under
35 U.S.C. § 103 as being unpatentable over Muller, Shockley
and
Gosch.
Rather than reiterate the arguments of Appellant and
the Examiner, reference is made to the brief and answer for
the respective details thereof.
OPINION
We will not sustain the rejection of claims 1, 3 and
5 through 8 under 35 U.S.C. § 103.
Appeal No. 95-3885
Application 08/172,051
4
The Examiner has failed to set forth a prima facie
case. It is the burden of the Examiner to establish why one
having ordinary skill in the art would have been led to the
claimed invention by the express teachings or suggestions
found
in the prior art, or by implications contained in such teach-
ings or suggestions. In re Sernaker, 702 F.2d 989, 995, 217
USPQ 1, 6 (Fed. Cir. 1983). "Additionally, when determining
obviousness, the claimed invention should be considered as a
whole; there is no legally recognizable 'heart' of the inven-
tion." Para-Ordnance Mfg. v. SGS Importers Int’l, Inc., 73
F.3d 1085, 1087, 37 USPQ2d 1237, 1239 (Fed. Cir. 1995), cert.
denied, 117 S.Ct. 80 (1996)
citing W. L. Gore & Assocs., Inc. v. Garlock, Inc., 721 F.2d
1540, 1548, 220 USPQ 303, 309 (Fed. Cir. 1983), cert. denied,
469 U.S. 851 (1984).
On pages 12 through 20 of the brief, Appellant
argues that Muller, Shockley and Gosch fail to teach Appel-
lant's claimed limitations. In particular, Appellant argues
Appeal No. 95-3885
Application 08/172,051
5
that Muller, Shockley and Gosch fail to teach forming an
exothermic body below a pn junction for heating the pn junc-
tion under an overcurrent as claimed in Appellant's claim 1.
Appellant further argues that Muller, Shockley and Gosch fail
to teach forming a first epitaxial layer of a first conductiv-
ity type with a high resistivity between a semiconductor
substrate and a second epitaxial layer as claimed in Appel-
lant's claim 5. Finally, Appellant argues that Muller,
Shockley and Gosch fail to teach providing an exothermic body
below a pn junction and between a semiconductor layer and a
substrate as claimed in claim 8.
In the answer, the Examiner argues pages 3 and 4 as
well as on pages 6 and 7 that the prior art teaches the
claimed structure and that the combination of Muller, Shockley
and Gosch is proper. In particular, the Examiner points out
on page 3 that Muller teaches "an ordinary diffused diode of a
p-type region into an n-type layer." The Examiner does not
rely on Muller for
Appeal No. 95-3885
Application 08/172,051
6
the teaching of an exothermic body as recited in Appellant's
claims 1 and 8 or for the teaching of a first conductivity
type with a high resistivity between a semiconductor substrate
and a second epitaxial layer as recited in Appellant's claim
5. The Examiner argues that Shockley and Gosch teach a
semiconductor thermal resistor. However, the Examiner states
on page 3 of the answer that Shockley and Gosch fail to
teach placing the semiconductor thermal resistor below a pn
junction of the diode. The Examiner argues that Shockley and
Gosch suggest to one of ordinary skill in the art to modify
the Muller diode to place the semiconductor thermal resister
below a pn junction of the Muller diode in order to achieve
stabilizing results as taught in Shockley.
As pointed out by our reviewing court, we must first
determine the scope of the claim. "[T]he name of the game is
the claim.” In re Hiniker Co., 150 F.3d 1362, 1369, 47 USPQ2d
1523, 1529 (Fed. Cir. 1998).
Turning first to Appellant's claim 1, we note that
the claim recites a "diode comprising: a semiconductor
substrate; a pn junction . . .; and an exothermic body for
Appeal No. 95-3885
Application 08/172,051
7
heating the pn junction under an overcurrent, said exothermic
body being provided in a neighborhood of the pn junction
wherein the
exothermic body is a semiconductor layer formed below the pn
junction." Emphasis added. Thus, Appellant's claim 1
requires a diode having an exothermic body for heating the pn
junction under an overcurrent.
Upon a careful review of Muller, Shockley and Gosch,
we fail to find that these references teach or suggest an
exothermic body for heating the pn junction under an
overcurrent wherein the exothermic body is a semiconductor
layer formed below the pn junction. We agree with the
Examiner that Muller is a general teaching of a pn-junction
diode and that Muller fails to teach any additional layers.
We agree with the Examiner that Gosch and Shockley teach a
resistive layer, but we fail to find that either reference
teaches an exothermic body placed below the pn junction for
heating the pn junction during an overcurrent condition as
recited in Appellant's claim 1.
Appeal No. 95-3885
Application 08/172,051
8
Shockley teaches in column 4, line 70, through
column 5, line 7, that Figure 5 shows a resistive layer 35 and
a pn junction. However, Shockley shows in Figure 5 that the
resistive layer 35 is not below the pn junction but placed on
the exposed surface of the device. Also, see column 14, lines
53-54, and lines 74-75. Shockley teaches in column 1, lines
12-26, that a serious limitation exists in the power handling
capacity
of many semiconductor devices due to thermal instability.
Shockley further teaches that the thermal instability results
in an unstable mode in which the current density increases in
one localized region which results in localized heat buildup
in this region of the device while the total external current
remains substantially constant. Shockley states that these
hot spots result in damage or destruction of the device.
In column 2, line 58, through column 4, line 39,
Shockley explains in detail the problem by referring to
schematic circuits shown in Figures 1 and 2 and the
theoretical curves for the current voltage characteristics of
Appeal No. 95-3885
Application 08/172,051
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a transistor for a set of constant base voltages as shown in
Figure 6. Shockley explains that Figure 6 shows that if the
current is increased, the voltage first rises toward a maximum
value and then drops producing a negative resistance.
Shockley then refers to Figure 1 which shows two
transistors 11 and 12 connected in parallel to show how these
transistors operate as described in Figure 6. Shockley shows
that an instability can occur if one of the transistors is in
a negative resistance condition. The instability will cause
one transistor to carry predominantly all the current while
the other carries practically no current.
Shockley then refers to Figure 3 to show his
invention which solves the instability by interposing a
distributed resistor, a layer of resistive material 27, in
series with the emitter current path. The resistive layer 27
is disposed over the surface of the transistor and over the
emitter region of the transistor. In column 4, line 68,
through column 5, line 25, Shockley discloses another
embodiment as shown in Figure 5 where the resistive layer is
provided by n- resistive layer 35 and n+ layer 36. Shockley
Appeal No. 95-3885
Application 08/172,051
10
teaches in column 3, line 68, through column 4, line 39,
that the advantage of the resistive layer is to spread out the
current as well as to prevent heat buildup in localized hot
spots.
Reading Shockley as a whole, we find that Shockley
teaches that the resistive layer is placed on the surface of
the semiconductor device to avoid heat buildup within the
device. Furthermore, Shockley teaches that heat buildup
within the semiconductor device is to be avoided and thereby
does not teach using the resistive layer for heating the pn
junction under an overcurrent condition as claimed in
Appellant's claim 1.
Gosch discloses a positive-temperature-coefficient
sensor that can operate at much higher temperatures using
spreading resistance principles similar to those taught by
Shockley. In the figure found on page 73, Gosch discloses a
structure for spreading the resistance which shows a similar
resistive layer as taught by Shockley. However, we fail to
find that Gosch teaches using the resistive layer for heating
Appeal No. 95-3885
Application 08/172,051
11
the pn junction under an overcurrent condition as claimed in
Appellant's claim 1.
Turning to Appellant's claims 5 and 8, we find that
these claims require that the resistive layer is to be placed
in between the substrate and the pn junction. In particular,
Appellant's claim 5 recites a "diode comprising: a
semiconductor substrate . . .; a first epitaxial layer . . .
with a high resistivity being formed on the semiconductor
substrate; a second epitaxial layer . . . formed on the first
epitaxial layer; a semiconductor region . . . which is formed
in the second epitaxial layer; and a pn junction defined
between the semiconductor region and the second epitaxial
layer." Also, Appellant's claim 8 recites a "diode
comprising: . . . an exothermic body provided below the pn
junction and between the semiconductor layer and the
substrate." Thus, Appellant's claims 5 and 8 both require
that the resistive layer or the exothermic body be positioned
within the diode under the pn junction and between the
substrate.
Appeal No. 95-3885
Application 08/172,051
12
Upon reviewing Muller, Shockley and Gosch, we fail
to find a teaching or a suggestion of placing the resistive
layer within the semiconductor device which is below the pn
junction and between the substrate and the pn junction. As
pointed out above, Shockley's teaching would lead those
skilled in the art to place the resistive layer on the surface
of the device so as to avoid further heating.
The Federal Circuit states that "[t]he mere fact
that the prior art may be modified in the manner suggested by
the Examiner does not make the modification obvious unless the
prior art suggested the desirability of the modification." In
re Fritch, 972 F.2d 1260, 1266 n.14, 23 USPQ2d 1780, 1783-84
n.14 (Fed. Cir. 1992), citing In re Gordon, 733 F.2d 900, 902,
221 USPQ 1125, 1127 (Fed. Cir. 1984). "Obviousness may not be
established using hindsight or in view of the teachings or
suggestions of the inventor." Para-Ordnance, 73 F.3d at 1087,
37 USPQ2d at 1239, citing W. L. Gore & Assocs., 721 F.2d at
1551, 1553, 220 USPQ at 311, 312-13.
Appeal No. 95-3885
Application 08/172,051
13
Upon a review of the references relied upon by the
Examiner, we fail to find any suggestion or reason to place
the
Shockley or Gosch resistive layer within the Muller diode
below
the pn junction. To the contrary, we find that the Shockley
teaching would have led those skilled in the art to place the
resistive layer on top of the Muller diode. Furthermore, none
of the references suggest that the resistive layer is to be
used to heat the pn junction, but in fact suggest that such
heating is not desirable. Therefore, we will not sustain the
rejection of claims 1, 3 and 5 through 8 under 35 U.S.C. § 103
as being unpatentable over Muller, Shockley and Gosch.
We have not sustained the rejection of claims 1, 3
and 5 through 8 under 35 U.S.C. § 103. Accordingly, the
Examiner's decision is reversed.
REVERSED
Appeal No. 95-3885
Application 08/172,051
14
LEE E. BARRETT )
Administrative Patent Judge )
)
)
) BOARD OF
PATENT
MICHAEL R. FLEMING ) APPEALS AND
Administrative Patent Judge )
INTERFERENCES
)
)
)
STUART HECKER )
Administrative Patent Judge )
psb
Appeal No. 95-3885
Application 08/172,051
15
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