Ex Parte Kopta

Patent Trial and Appeal Board

Jan 9, 2015

12417774 (P.T.A.B. Jan. 9, 2015)

UNITED STATES PATENT AND TRADEMARK OFFICE
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BEFORE THE PATENT TRIAL AND APPEAL BOARD
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Ex parte ARNOST KOPTA
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Appeal 2012-008987
Application 12/417,774
Technology Center 2800
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Before ADRIENE LEPIANE HANLON, CATHERINE Q. TIMM, and
JAMES C. HOUSEL, Administrative Patent Judges.

TIMM, Administrative Patent Judge.

DECISION ON APPEAL

STATEMENT OF CASE
Appellant seeks review of the Examiner’s decision to reject claims 1–
3, 6–14, and 20 under 35 U.S.C. § 102(b) as anticipated by Kitagawa.1 We
have jurisdiction under 35 U.S.C. §§ 6(b) and 134(a).
We AFFIRM.

1 Kitagawa et al., US 5,162,876, patented Nov. 10, 1992.
Appeal 2012-008987
Application 12/417,774
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The claims are directed to a power semiconductor device. Appellant
does not argue any claim apart from the others. Appeal Br. 4–8. We select
claim 1 as representative. Claim 1, with reference numerals from Figures 2–
5 inserted to illustrate the structures encompassed by the claim and with the
primary limitations at issue italicized, is reproduced below:
1. A power semiconductor device with
a first layer [2] of a first conductivity type [n-], which has
a first main side [21] and a second main side [22] opposite the
first main side,
a second layer [3] of a second conductivity type [p+],
which is arranged in a central region of the first main side [21],
a fourth electrically conductive layer [4], which is
arranged on the second layer [3] on the side opposite the first
layer [2],
a third layer [5], which is arranged on the second main
side [22] and which comprises a first zone [51] of the first
conductivity type [n+] with a higher doping than the first layer
[2], and
a fifth electrically conductive layer [6], which is arranged
on the third layer [5] on the side opposite the first layer [2], the
area between the second layer [3] and the first zone [51]
defining an active area [9],
wherein the third layer [5] comprises a second zone [52]
of the second conductivity type [p+], which is arranged in the
same plane as the first zone [51] and which second zone [52]
completely surrounds the first zone [51],
wherein a sixth layer [10] of the first conductivity type
[n] with a doping, which is lower than that of the first zone [51]
and higher than that of the first layer [2], is arranged between
the second zone [52] and the first layer [2],
Appeal 2012-008987
Application 12/417,774
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wherein the fifth electrically conductive layer [6]
completely covers that side of the third layer [5] , which lies
opposite the first layer [2] and
wherein the second zone [52] completely covers the fifth
electrically conductive layer [6] on its side towards the first
layer [2] around the active area [9] and the sixth layer [10].
Claims Appendix of the Appeal Br. 1 (formatting added.)

OPINION

The basic underlying dispute between the Examiner and Appellant, as
recognized by Appellant in the Reply Brief, has to do with the meaning of
“active area” in claim 1. Reply Br. 1. The Examiner finds that Kitagawa
has an active area that results in a second zone that completely covers a fifth
electrically conductive layer as required by claim 1. Ans. 6. The Examiner
bases this finding on an interpretation of “active area” informed by
Appellant’s Figure 5. Ans. 17-18. In Appellant’s Figure 5, region 9ʺ is
designated the “active area.” Figure 5 is reproduced below:
Appeal 2012-008987
Application 12/417,774
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Claim 1 recites that “the area between the second layer [3] and the
first zone [51] defin[es] an active area.” As shown in Figure 5, a second
zone 52 “completely covers the fifth electrically conductive layer [6] on its
side towards the first layer [2] around the active area 9ʺ.” Claim 1. In other
words, zone 52 extends without interruption across the portions of layer 6
outside the active zone 9ʺ.
Kitagawa does not expressly describe an active region. According to
the Examiner, Kitagawa’s active region extends between the broken lines as
shown below:

Appeal 2012-008987
Application 12/417,774
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Kitagawa’s Figure 15, which is a cross-sectional view of a power
semiconductor, with broken lines showing the extent of the active area as
found by the Examiner

As a first matter, we agree with Appellant that the outer-most P++
layers, while unlabeled, are carrier injection blocking layers like the other
P++ layers labeled 10 in Kitagawa’s Figure 15. Appeal Br. 6; Kitagawa,
col. 9, ll. 2-4. Under the Examiner’s interpretation, the second zone (outer-
most P++ layers) would completely cover the fifth electrically conductive
layer (layer 5) “around the active area” as claimed.
Under Appellant’s interpretation, the active region of Kitagawa only
extends to the inner-most P++ carrier injection blocking layers 10. Reply
Br. 2. We reproduce another annotated figure to illustrate:
Appeal 2012-008987
Application 12/417,774
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Kitagawa’s Figure 15 with broken lines

If the active region has the extent argued by Appellant, Kitagawa’s
outer-most P++ carrier injection blocking layers will not define a second
zone that “completely covers the fifth electrically conductive layer
[Kitagawa’s layer 5] on its side towards the first layer [Kitagawa’s layer 1]
around the active area.” Claim 1 (emphasis added.) Because of the gaps
between the P++ carrier injection blocking layers, layer 5 would not be
entirely covered by the P++ layer.
Appellant contends that “active area” is defined in the Specification as
the area in which “current flows, when the diode is forward biased,” Reply
Br. 2, citing Spec. ¶ 16 at 7:5–7, but Appellant’s quote leaves out important
language. The full sentence states that “[t]he area between the second layer
and the first zone defines an active area, in which area the current flows,
when the diode is forward biased.” Claim 1 includes the “area between the
second layer and the first zone defines an active area” language but not the
language regarding the current. Appellant’s Figures 2–5 depict the active
Appeal 2012-008987
Application 12/417,774
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area as extending between second layer 3 and first zone 51. As shown in
Figure 5, first zone 51 can contain p+ zones 55. Zones 55 can be
manufactured in the same step as the p+ doped second zone 52 with the
same mask and the same implant. Spec. ¶ 26. It is the extent of the zone 51
that defines the extent of the active region. Zone 51 can contain p+ zones.
Like Appellant’s first zone 51 shown in Figure 5, Kitagawa’s first
zone 3b not only occupies the center between inner-most inner carrier
injection blocking layers 10, but also extends between the inner carrier
injection blocking layers 10 to the edge of the outer-most carrier injection
blocking layers (unlabeled). The current blocking layers reduce the area in
which carriers can be injected, but there is no convincing evidence that the
areas of the first zone 3b between the carrier injection blocking layers would
not inject carriers and form a part of the active region.
A preponderance of the evidence supports the Examiner’s
interpretation of “active region” in claim 1 and the anticipation of claim 1 by
Kitagawa.
With regard to Appellant’s contention that Kitagawa’s layer 3a, which
the Examiner finds is the sixth layer of claim 1, does not have a doping
lower than that of the first zone (Kitagawa’s layer 3b), Appeal Br. 5, we
agree with the Examiner that Figure 29 supports the finding that Kitagawa
teaches a layer 3a having a lower doping than layer 3b. Ans. 13–14.

CONCLUSION
We sustain the Examiner’s rejection.

DECISION
The Examiner’s decision is affirmed.
Appeal 2012-008987
Application 12/417,774
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TIME PERIOD FOR RESPONSE
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1).

AFFIRMED

cdc