Ex parte HIGA et al.

Board of Patent Appeals and Interferences

Feb 10, 1998

08245775 (B.P.A.I. Feb. 10, 1998)

Application for patent filed May 18, 1994.1
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law journal and (2) is not binding precedent of the Board.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. 17
UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte KELVIN T. HIGA,
ROBERT W. GEDRIDGE, JR.
RALPH KORENSTEIN,
and STUART J.C. IRVINE
_____________
Appeal No. 96-3475
Application 08/245,7751
______________
ON BRIEF
_______________
Before JOHN D. SMITH, PAK and OWENS, Administrative Patent Judges.
JOHN D. SMITH, Administrative Patent Judge.
DECISION ON APPEAL
This is an appeal pursuant to 35 U.S.C. § 134 from the final rejection of claims 1-13.
Claims 1, 6, 7, and 13 are representative and are reproduced below:
Appeal No. 96-3475
Application 08/245,775
2
1. A process for indium doping of a Group II/Group VI semiconductor material by
chemical vapor deposition wherein the indium source is triisopropylindium.
6. The process of claim 1, wherein the indium doping concentration of said doping
reaction takes place at a carrier concentration ranging from about 1 x 10 cm to about 1 x19 -3
10 cm in said Group II/Group VI semiconductor material.14 -3
7. A process for indium doping a Group II/Group VI semiconductor material by chemical
vapor deposition which comprises reacting triisopropylindium and one or more sources of a
Group II material and one or more sources of a Group VI material by chemical vapor deposition
at a temperature sufficiently high to at least partially decompose the triisopropylindium and said
Group II and said Group VI source materials, and depositing said Group II/Group VI
semiconductor materials on a semiconductor substrate such that minimal indium memory doping
occurs.
13. An indium-doped Group II/Group VI semiconductor material produced by the
process of claim 1, wherein the indium doping concentration of said doping reaction takes place at
a carrier concentration ranging from about 1 x 10 cm to about 1 x 10 cm in said Group19 -3 14 -3
II/Group VI semiconductor material.

The reference of record relied upon by the examiner is:
Chen et al. (Chen), "Triisopropylindium for OMVPE growth", Journal of Crystal Growth, Vol.
124, Nos. 1-4, (1992), pp. 88-92.
A reference cited and relied upon by the Board is:
Gedridge 5,346,852 Sept. 13, 1994
(filed Feb. 25, 1993)
Appeal No. 96-3475
Application 08/245,775
The disclosures of this document are discussed in the specification at page 2, lines 12-18. 2
The Gedridge patent which issued from this application is prior art under 35 U.S.C. § 102 (e).

3
The appealed claims stand rejected under 35 U.S.C. § 103 as unpatentable over admitted
prior art (specification, page 2, lines 7-11) in view of Chen.
We agree with the examiner’s conclusion that the claimed subject matter on appeal would
have been obvious to a person of ordinary skill in the art. However, because our analysis of the
prior art is based on a more comprehensive review of the record including, inter alia , the
disclosure of application 08/027,314 which matured into U.S. Patent No. 5,346,852 to Gedridge2
and because we rely on a rationale substantially different from that expressed by the examiner, we
denominate our affirmance of the stated rejection as involving a new rejection (37 CFR § 196(b)).
The subject matter on appeal, in general, relates to the doping of semiconductor materials,
and more particularly, to the use of triisopropylindium as a dopant precursor in the chemical
vapor deposition of Group II/Group VI semiconductor materials. By way of background in the
"related art" section of the specification (pages 1-3), appellants indicate that the II/VI
semiconductor materials such as mercury cadmium telluride have been used commercially as
infrared detectors and infrared emitters . Such applications of the II/VI semiconductor materials
have required controlled extrinsic doping of both the p-type and n-type semiconductor materials.
According to appellants, low level doping of the n-type mercury cadmium telluride in the range
of 10 atoms per cm to 10 atoms per cm has remained a problem in the art. Thus when14 3 15 3
Appeal No. 96-3475
Application 08/245,775
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trimethylindium is used as indium dopant precursor, the lowest doping achieved is in the mid 1016
atoms per cm . See the specification at page 2, line 22. This is caused by the relatively high3
vapor pressure of trimethylindium. Appellants further indicate that trimethylindium is not a
suitable precursor for doping because it suffers from transport problems. Thus as acknowledged
in the specification at page 2, lines 13-16, since trimethylindium is a solid at or below room
temperature the effective vapor pressure of trimethylindium in a conventional bubbler changes
with time due to changes in the surface area of the solid. In addition, appellants point out that
when trimethylindium is used as the precursor for doping of II/VI semiconductor materials, it has
shown a significant memory effect, i.e., the indium doping persists for a number of growth runs
following the introduction of the trimethylindium source.
Thus, while admitting that indium is the prior art "dopant of choice" which is primarily
provided by trimethylindium as the indium dopant precursor in prior art doping in both
"interdiffusion multilayer and directed alloy growth” processes, appellants indicate that
trimethylindium is the cause of the above mentioned problems when used in such processes. To
solve the problems associated with the use of solid trimethylindium as a dopant precursor,
appellants utilized a liquid indium dopant precursor, i.e., triisopropylindium, which is said to
provide a constant quantity with better control of the dopant at reasonable temperatures, thus
permitting doping at low carrier concentrations with a reduction of the memory effect. Generally
see the specification at page 3.
Appeal No. 96-3475
Application 08/245,775
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Relying on appellants’ admissions (specification, page 2, lines 7-11) and Chen’s disclosure
that triisopropylindium has a much lower decomposition temperature than trimethylindium, the
examiner contends that it would have been obvious to a person with ordinary skill in the art to
utilize the claimed source in place of the trimethylindium precursor to effectively reduce the
temperature of the doping processing. With respect to the admitted prior art doping processes
involving the interdiffused multilayer process and directed alloy growth process for the doping of
mercury cadmium telluride, however, doping temperature ranges are not disclosed. Thus there is
no objective or factual support explaining why one of ordinary skill in the art would desire to
lower the effective doping temperature or why there would be any advantage for doping II/VI
semiconductor materials at lower temperatures. Accordingly, the rationale of the examiner’s
stated rejection is not adequately factually supported. For the reasons below, however, we agree
with the examiner’s conclusion that the claimed subject matter would have been obvious.
As indicated above, the use of trimethylindium presents transport problems when used as a
low level n-type dopant in the chemical vapor deposition of II/VI semiconductor materials, such
as mercury cadmium telluride. Thus, because it is a solid at or below room temperature, its
effective vapor pressure changes with time, and thus it does not provide a constant quantity of
indium during the prior art doping processes. The Gedridge patent relates to the use of the
claimed material, triisopropylindium as an alternative precursor for the chemical vapor deposition
growth (not doping) of indium-containing semiconductor materials, i.e. III/V semiconductors.
More particularly, however, Gedridge indicates that triisopropylindium is a liquid with a low
Appeal No. 96-3475
Application 08/245,775
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freezing point and has a useful vapor pressure in chemical vapor deposition systems ( col. 2, lines
30-35). Thus liquid triisopropylindium is said to offer a "substantial advantage" (col. 4, line 62)
over the solid trimethylindium in terms of transport properties, and provides a constant and
controllable quantity of indium to a chemical vapor deposition reactor when a carrier gas is
bubbled through the liquid (col. 4, lines 53-63 and col. 2, lines 20-24). In light of the disclosures
in Gedridge, one of ordinary skill in the art, motivated by the desire to solve the prior art
"transport problem", would have been led to use triisopropylindium as a liquid dopant precursor
source with a reasonable expectation that a constant and controllable quantity of indium would be
provided for the doping of II/VI semiconductor materials.
Appellants state in their specification that just because a given compound may
demonstrate acceptable results when used as a source compound for semiconductor materials
does not lead one to the conclusion that the same compound can be used as a dopant source for
semiconductor materials with equally good results. See the specification at page 3, lines 3-6.
However, in light of the disclosures in the Gedridge patent, why such equally good results would
not have been expected for the liquid compound, triisopropylindium, has not been adequately
explained by appellants. Moreover, we observe that trimethylindium, the prior art solid source
material, has provided acceptable results both as a source compound for semiconductor materials
and as dopant source for II/VI semiconductor materials such as mercury cadmium telluride at
least at dopant concentrations in the mid 10 cm range. Again see the specification at page 2,16 -3
lines 20-22. Further, as the examiner has accurately pointed out in the answer, appellants have
Appeal No. 96-3475
Application 08/245,775
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presented no claim on appeal which is directed to the low level doping of II/VI materials
providing a dopant concentration in the range of 10 atoms per cm . In this regard, appealed14 3
claims 6, 12, and 13 all recite concentration ranges from “about 1 x 10 cm to about 1 x 1019 -3 14
cm “ in the Group II/Group VI semiconductor material. -3
Further, although a person of ordinary skill in the art might understand that
triisopropylindium is more sterically demanding than trimethylindium in a doping process as
claimed (Brief, page 8), appellants have not explained why one of ordinary skill in the art would
not have expected at least acceptable doping within the broad dopant concentration range
claimed.
Appellants have asked for separate consideration of appealed process claims 7-11. See
the brief at page 5. These claims define the process more specifically and indicate that “minimal
indium memory doping occurs”. Judging from the evidence before us, appellants may have been
the first to recognize that the use of triisopropylindium in a doping process as claimed provides a
benefit in that the memory effect is reduced. However, it is a well settled principle of law that the
motivation in the prior art to combine the teachings of the prior art does not have to be identical
to that of an applicant to establish a prima facie case of obviousness. In re Dillon, 919 F.2d 688,
693, 16 USPQ2d 1897, 1901 (Fed. Cir. 1990) (in banc) cert. denied, 500 U.S. 409 (1991). To
the extent that the attainment of “minimal indium memory doping” is said to establish results
which would not have been expected by person of ordinary skill in the art, we point out that there
Appeal No. 96-3475
Application 08/245,775
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is no side by side comparison or other data in the record establishing the extent to which the
claimed process “minimizes” the memory doping.
Although appellants have grouped product-by-process claim 13 with independent process
claim 1, we observe that the examiner correctly separately treated the subject matter of this claim
in the answer at pages 4 and 5. Since this claim also provides for a broad range of carrier
concentration ranging “from about 1 x 10 cm to about 1 x 10 cm in the Group II/Group VI19 -3 14 -3
semiconductor material”, the claim covers prior art indium-doped Group II/Group VI
semiconductor material having a carrier concentration in the range of 10 cm . Thus, it is16 -3
apparent that this claim does not define patentable subject matter.
In summary, we agree with the examiner’s conclusion that the claimed subject matter on
appeal would have been obvious to a person of ordinary skill in the art within the meaning of 35
U.S.C. § 103. However, since we have relied on the Gedridge patent and a more comprehensive
view of the prior art admissions and have provided a different rationale than that of the examiner,
we denominate our affirmance of the rejection as involving a new ground of rejection. 37 CFR §
1.196(b).
In addition to affirming the examiner’s rejection of one or more claims, this decision
contains a new ground of rejection pursuant to 37 CFR § 1.196(b)(amended effective Dec. 1,
1997, by final rule notice, 62 Fed. Reg. 53,131, 53,197 (Oct. 10, 1997), 1203 Off. Gaz. Pat. &
Trademark Office 63, 122 (Oct. 21, 1997)). 37 CFR § 1.196(b) provides, “A new ground of
rejection shall not be considered final for purposes of judicial review.”
Appeal No. 96-3475
Application 08/245,775
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Regarding any affirmed rejection, 37 CFR § 1.197(b) provides:
(b) Appellant may file a single request for rehearing within two months from the
date of the original decision . . . .
37 CFR § 1.196(b) also provides that the appellant, WITHIN TWO MONTHS FROM
THE DATE OF THE DECISION, must exercise one of the following two options with respect to
the new ground of rejection to avoid termination of proceedings (37 CFR § 1.197(c)) as to the
rejected claims:
(1) Submit an appropriate amendment of the claims so rejected or a
showing of facts relating to the claims so rejected, or both, and have the matter
reconsidered by the examiner, in which event the application will be remanded to
the examiner. . . .
(2) Request that the application be reheard under § 1.197(b) by the Board
of Patent Appeals and Interferences upon the same record. . . .
Should the appellant elect to prosecute further before the Primary Examiner pursuant to
37 CFR § 1.196(b)(1), in order to preserve the right to seek review under 35 U.S.C. §§ 141 or
145 with respect to the affirmed rejection, the effective date of the affirmance is deferred until
conclusion of the prosecution before the examiner unless, as a mere incident to the limited
prosecution, the affirmed rejection is overcome.
If the appellant elects prosecution before the examiner and this does not result in
allowance of the application, abandonment or a second appeal, this case should be returned to the
Board of Patent Appeals and Interferences for final action on the affirmed rejection, including any
timely request for rehearing thereof.
Appeal No. 96-3475
Application 08/245,775
10
No time period for taking any subsequent action in connection with this appeal may be
extended under 37 CFR
§ 1.136(a).
AFFIRMED; 37 CFR § 1.196(b)
)
JOHN D. SMITH )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
CHUNG K. PAK )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
TERRY J. OWENS )
Administrative Patent Judge )
Appeal No. 96-3475
Application 08/245,775
11
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