Ex parte MOSLEHI

Board of Patent Appeals and Interferences

Jun 16, 1998

08024883 (B.P.A.I. Jun. 16, 1998)

Application for patent filed March 1, 1993. According to1
appellant, this application is a continuation of Application
07/721,739, filed June 26, 1991, now abandoned.
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(2) is not binding precedent of the Board.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. 27
UNITED STATES PATENT AND TRADEMARK OFFICE
__________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________
Ex parte MEHRDAD M. MOSLEHI
__________
Appeal No. 95-2503
Application 08/024,8831
__________
ON BRIEF
__________
Before HAIRSTON, KRASS, and BARRETT, Administrative Patent
Judges.
KRASS, Administrative Patent Judge.
DECISION ON APPEAL
Appeal No. 95-2503
Application No. 08/024,883
2
This is a decision on appeal from the final rejection of
claims 1 through 8 and 30 through 43, all the claims pending
in the application.
The invention pertains to an insulated gate field effect
transistor (IGFET) structure. More particularly, the junction
depth and doping concentrations of non-overlapped (lightly
doped portions of source and drain not beneath the transistor
gate) and overlapped (lightly doped portions of source and
drain beneath the transistor gate) portions of the source and
drain junctions may be controlled independently which is said
to result in optimal transistor performance and reliability
characteristics tailored to the desired use.
Independent claim 1 is reproduced as follows:
1. An insulated-gate field-effect transistor comprising:
a semiconductor substrate;
a drain region formed in said semiconductor substrate,
said drain region comprising a heavily doped region, a first
lightly doped region with a first selected doping
concentration and junction depth and a second lightly doped
region with a second selected doping concentration and
junction depth, wherein said first selected doping
concentration and junction depth is independent of said second
selected doping concentration and junction depth and wherein
said second selected doping concentration and junction depth
Appeal No. 95-2503
Application No. 08/024,883
Our understanding of the Furuhata reference is derived2
from an English translation thereof prepared by the United
States Patent and Trademark Office. A copy of that
translation is attached hereto.
3
is independent of said first selected doping concentration and
junction depth;
a source region formed in said semiconductor substrate;
a channel region separating said source and drain
regions;
an insulating layer formed over said channel region and
over said second lightly doped drain region; and
a conductive gate formed over said insulating layer.
The examiner relies on the following references:
Lehrer et al. 4,442,449 Apr. 10, 1984
(Lehrer)
Nishizawa et al. 4,660,062 Apr. 21, 1987
(Nishizawa)
Liou et al. 4,771,014 Sep. 13, 1988
(Liou)
Toyoshima 4,935,379 Jun. 19, 1990
Mori 4,943,836 Jul. 24, 1990
Jain 4,949,136 Aug. 14, 1990
Furuhata (JP) 62-155682 Jan. 5, 19892
Claims 1 through 8 and 30 through 43 stand rejected under
the first and second paragraphs of 35 U.S.C. § 112 as,
respectively, relying on an interpretation of the term
Appeal No. 95-2503
Application No. 08/024,883
It appears that the examiner does not employ the3
teachings of all these references for each of the claims. For
example, it appears that only Mori is employed, together with
Jain and Toyoshima, to reject claim 5 but the examiner has
improperly lumped all seven references together in order to
reject claim 5. When reciting a statement of rejection, the
examiner should include only those references necessary for
the rejection. In accordance with the examiner’s reasoning in
support of the rejections, it would appear that each, or some,
of claims 5, 7, 8 and 36 through 41 are, in fact, rejected
under grounds of rejection that differ from claim to claim.
4
“independent” which is not supported by the specification as
originally filed and failing to particularly point out and
distinctly claim the subject matter applicant regards as the
invention.
Claims 1 through 8 and 30 through 43 stand further
rejected under 35 U.S.C. § 103. As evidence of obviousness,
the examiner cites Jain and Toyoshima with regard to claims 1
through 4, 6, 30 through 35, 42 and 43, adding Mori, Furuhata,
Lehrer, Nishizawa and Liou to this combination with regard to
claims 5, 7, 8 and 36 through 41.3
Reference is made to the briefs and answers for the
respective positions of appellant and the examiner.
OPINION
Turning first to the rejections under 35 U.S.C. § 112,
first and second paragraphs, while we sympathize with the
Appeal No. 95-2503
Application No. 08/024,883
5
examiner regarding the meaning of “independent” in claim 1 and
support for the “insulating region” in claim 5, we will,
nevertheless, not sustain these rejections.
With regard to claim 1, the examiner questions the
meaning of “independent,” indicating that the specification
suggests that “independent” refers to a process of formation.
The examiner refers to page 14, lines 8-11 of the
specification for the statement:
It is important to notice that the overlapped
lightly
doped source 18 and drain 26 regions have been
formed
independently of non-overlapped portions 16 and 24
with
respect to doping concentration and junction depth.
The examiner further cites page 4, lines 14-15 of the
specification, wherein it is stated that “the overlapped and
the non-overlapped portions of the source and drain junctions
are formed independently from each other...”
Thus, the specification would appear to indicate that the
term “independent,” when used in conjunction with the first
and second selected doping concentration and junction depth
being “independent” of each other, does indeed, refer to the
Appeal No. 95-2503
Application No. 08/024,883
6
process of forming the first and second lightly doped regions.
Yet, appellant argues that the instant claims, e.g.,
independent claim 1, are not product-by-process claims. This,
of course, is very confusing to the examiner as well as to us.
Appellant notes, on the bottom of page 10 of the
principal brief, that “the claims do not require independent
formation, only that the concentrations and depths of the
regions are ‘independent’.” Again, this is confusing because
as described in the specification and shown in Figures 9 to
10, overlapping portions 18 and 26 appear to have been formed
independently of non-overlapping portions 16 and 24 and it is
this “formation” which makes the selected doping
concentrations and junction depths “independent.” Therefore,
the independence of the first selected concentration and
junction depth from the second concentration and junction
depth and vice-versa is clearly dependent on the formation of
the overlapping and non-overlapping portions.
Accordingly, we find that the term “independent” in
independent claim 1 clearly refers to a process limitation
within a product-by-process claim. There is clear support for
such a finding within the original specification and there is
Appeal No. 95-2503
Application No. 08/024,883
7
nothing indefinite about the term “independent” when viewed as
such. Therefore, while we understand the examiner’s confusion
and frustration with the term “independent” in view of
appellant’s arguments and refusal to admit that the term
referred to a process limitation, our finding that this term
does, indeed, refer to a process limitation obviates the
rejections under the first and second paragraphs of 35 U.S.C.
§ 112.
With regard to claim 5, again, we understand the
examiner’s frustration but will, nonetheless, not sustain the
rejection of this claim under 35 U.S.C. § 112, first and
second paragraphs. While the “insulating region” called for
by claim 5 does not appear to be shown in the finished product
in Figure 1, insulating region 48 is clearly within conductive
gate 42 as shown, for example, in Figures 8, 10 and 11.
Appellant also refers us to page 10, line 14 and page 13, line
10, as well as Figure 12, for support for the insulating
region. Reference to the cited pages in the specification
discloses only “thin oxide 48” at page 10 and nothing about
element 48 on line 10 of page 13. Also, while appellant
refers us to Figure 12, there is no element therein labeled
Appeal No. 95-2503
Application No. 08/024,883
8
“48.” The elements referred to by appellant are in Figure 12;
they just are not labeled. Appellant should have indicated
that the thin oxide 48 is what was meant by the claimed
“insulating region” rather than have us resort to making a
finding that this, in fact, was what was intended. In any
event, we do find that “thin oxide 48” is sufficient support
for the now claimed “insulating region” in claim 5. Moreover,
since the “insulating region” was also part of original claim
5, there was clear support for such a recitation.
We now turn to the prior art rejections. We will sustain
the rejection of claims 1 through 4, 6, 30 through 35, 42 and
43 under 35 U.S.C. § 103 over Jain and Toyoshima as well as
the rejection of claims 5, 7, 8, 36 and 38 through 41 under 35
U.S.C.
§ 103 over Jain, Toyoshima, Mori, Furuhata, Lehrer, Nishizawa
and Liou. We will, however, not sustain the rejection of
claim 37 under 35 U.S.C. § 103.
Appellant argues that the dopant concentration and depth
of regions 20 and 21 in Jain are not “independent” from one
another. Appellant also argues that Toyoshima appears to use
a double diffused drain that has disadvantages which the
Appeal No. 95-2503
Application No. 08/024,883
9
instant invention was designed to avoid and that Toyoshima
does not show overlapped and non-overlapped portions of the
source and drain junctions “formed independently.”
These arguments are unpersuasive since we have found the
“independent” limitation to be a process limitation within a
product-by-process claim. Determination of patentability in
such a claim is based on the product itself, even though the
claim is limited and defined by a process, e.g., that certain
portions are formed independently, and, therefore, the product
in such a claim is unpatentable if it is the same as, or
obvious from, a product of the prior art, even if the prior
art product was made by a different process. In re Thorpe,
777 F.2d 695, 697; 227 USPQ 964, 966 (Fed. Cir, 1985).
Taking Toyoshima, for example, and applying it to instant
claim 1, this reference shows, in Figure 9, a transistor
comprising a substrate and a drain region 31 formed in the
substrate. The drain region has a heavily doped region 29, a
first lightly doped region 27 and a second lightly doped
region 25. Clearly, these first and second lightly doped
regions have some selected doping concentration and junction
depth values. The fact that the claim requires these doping
Appeal No. 95-2503
Application No. 08/024,883
10
concentration and junction depth values to be “independent” is
irrelevant to this product-by-process claim because no
difference can be discerned from the structure shown in Figure
9 of Toyoshima and the structure (Figure 1 of the instant
application) obtained by the instant claimed invention, the
“independence” relating to the way the first and second
lightly doped regions are formed.
At page 13 of the principal brief, appellant contends
that:
Certainly, the depth of a junction represents a
structure. Similarly, the concentration of dopants
in a region is a structure. Therefore, the claimed
relationship of the doping concentrations and
junction depths is a structural limitation.
We simply do not understand how appellant can contend
that a selected doping concentration and a selected junction
depth represent structural limitations. The claim does not
require a specific physical junction depth; only that a
junction depth exists. Clearly, any lightly doped region,
such as the ones shown by Toyoshima, has some junction depth,
as claimed. With regard to the claimed “doping
concentration,” one cannot ascertain, by a physical
observation of regions, what the doping concentration is for
Appeal No. 95-2503
Application No. 08/024,883
11
those regions. Clearly, there is no physically observable
difference between structures with differing doping
concentrations. Accordingly, contrary to appellant’s
contention, the concentration of dopants in a region is not a
structure. Therefore, we do not understand how a claimed
relationship of the doping concentrations and junction depths
is a structural limitation.
Although appellant argues that “the resultant structure
is what is important in the structure claim, not the method of
forming that structure” (page 13 of the principal brief), and
we agree, the burden is upon appellant to come forward with
evidence establishing an unobvious difference between the
claimed structure and the prior art structure. See In re
Marosi, 710 F.2d 799, 803, 218 USPQ 289, 293 (Fed. Cir. 1983).
Thus, the “independent” limitations of claim 1 do not
distinguish the instant claimed invention from the structure
shown by the applied references. We continue in our analysis.
Toyoshima clearly shows a source region 30 formed in the
substrate and a channel region separates the source and drain
regions. An insulating layer, gate oxide film 23, is formed
over the channel region and over the second lightly doped
Appeal No. 95-2503
Application No. 08/024,883
12
region 25. Further, a conductive gate (aluminum wire 36) is
formed over the insulating layer 23. Accordingly, the subject
matter of claim 1 is met by Toyoshima, alone. Therefore, we
will sustain the rejection of claim 1 under 35 U.S.C. § 103 as
unpatentable over Jain and Toyoshima.
While we have shown how Toyoshima, alone, would make the
subject matter of instant claim 1 unpatentable, this is not a
new ground of rejection as Jain is merely cumulative to the
teachings of Toyoshima and anticipation is merely the epitome
of obviousness. In re Fracalossi, 681 F.2d 792, 794, 215 USPQ
569, 571 (CCPA 1982).
With regard to claim 5, appellant argues (page 20-
principal brief) that the claim calls for a gate including “an
insulating region formed therein” and that the examiner has
cited Mori for an EPROM device which includes an insulator to
isolate the floating gate from the control gate. Appellant
then states, “[a]ppellant agrees that claim 5 is broad enough
to encompass EPROM and EEPROM devices.” Thus, appellant
appears to admit that the examiner’s rejection of claim 5 is
proper. To the extent, appellant is merely saying that while
Mori does, indeed, disclose the limitations added by claim 5,
Appeal No. 95-2503
Application No. 08/024,883
13
claim 5 actually also includes the limitations of independent
claim 1 which are unobvious for previously argued reasons, we
have shown, supra, how the limitations of claim 1 are met by
the prior art. Since appellant is not arguing that the
teachings of Mori are not combinable with the other
references’ teachings, we will sustain the rejection of claim
5 under 35 U.S.C. § 103.
With regard to claim 3, appellant specifically argues
that the claim recites “an elevated semiconductor source
region formed above said heavily doped portion of said
source.” Appellant argues (page 21-principal brief) that the
silicide regions 24 and 26 of Jain are not “semiconductor”
regions and therefore do not meet this claim limitation. The
examiner counters that silicide “has a band gap, and would
thus appear to be a semiconductor” (bottom of page 12 of the
principal answer). Thus, while we have no evidence one way or
the other, the examiner contends that the silicide regions of
Jain are semiconductors while appellant contends that they are
not. A semiconductor is an electronic conductor with
resistivity in the range between metals and insulators. The
silicide regions of Jain clearly conduct somewhat and,
Appeal No. 95-2503
Application No. 08/024,883
14
therefore, are not insulators. At the same time, the silicide
regions of Jain are not metal. Therefore, we find that these
regions must be semiconductors and appellant has not shown us
any evidence establishing that they are not semiconductors.
Further, it would have been obvious to use the silicide
contacts of Jain as caps over the source and drain regions of
Toyoshima rather than the aluminum elements 34 and 35 in
Toyoshima since they are all conductive contacts to the source
and drain regions. Accordingly, we will sustain the rejection
of claim 3 under 35 U.S.C. § 103.
With regard to claims 40 and 41, appellant argues that
the elevated source and drain regions comprise “germanium” and
a “silicon/germanium alloy,” respectively. The examiner cites
Lehrer for a teaching of a binary germanium-silicon
interconnect and electrode structure. The examiner relies on
Furuhata for the teaching of elevated source and drain regions
to provide for interconnects to other devices. Therefore,
concludes the examiner, it would have been obvious to use
germanium-silicon for interconnects, as taught by Lehrer,
“interconnecting source and drain regions as taught by
Appeal No. 95-2503
Application No. 08/024,883
15
Furuhata, to connect to other devices as taught by Furuhata”
(page 12 of the principal answer).
While the examiner appears to have made a prima facie of
obviousness, appellant argues only (principal brief-page 22)
that Lehrer “does not teach or suggest elevated source/drain
regions.” This argument is unpersuasive since it is not
Lehrer, but, rather Furuhata which the examiner relies on for
the teaching of elevated source/drain regions. Accordingly,
we will sustain the rejection of claims 40 and 41 under 35
U.S.C. § 103. We also will sustain the rejections of claims
2, 4, 6 through 8, 30 through 36, 38 and 39 under 35 U.S.C. §
103 since, not being separately argued as to their merits,
these claims fall with the claims from which they depend.
We will, however, not sustain the rejection of claim 37
under 35 U.S.C. § 103. This claim requires that the elevated
source/drain regions “comprise a single crystal
semiconductor.” The examiner contends that Nishizawa teaches
that source and drain regions 14 and 15 comprise a “single
crystal semiconductor” and that it would have been obvious to
use a heavily doped single crystal semiconductor to elevate
source and drain regions instead of the silicide of Jain “in
Appeal No. 95-2503
Application No. 08/024,883
16
order to allow the elevated source and drain to be formed by
etching the substrate material, as taught by Nishizawa” (pages
11-12 of the principal answer).
We disagree. First, it is not clear to us that Nishizawa
even discloses a “single crystal semiconductor.” We do not
find such recitation in the disclosure of Nishizawa and, yet,
appellant never specifically denies that Nishizawa discloses a
single crystal semiconductor. Appellant simply says, at page
21 of the principal brief, that Nishizawa “simply does not
teach or suggest a single crystal semiconductor elevated
source or drain region formed over a heavily doped source or
drain region.” But, even assuming, arguendo, that a single
crystal semiconductor is taught, we find no convincing
rationale by the examiner as to why the skilled artisan would
have sought to replace the silicide of Jain with a single
crystal semiconductor. What advantage is to be gained? We
find no suggestion of this in the applied references and the
examiner has not convinced us otherwise.
We have not sustained the rejection of claims 1 through 8
and 30 through 43 under either the first or second paragraph
of 35 U.S.C. § 112 nor have we sustained the rejection of
Appeal No. 95-2503
Application No. 08/024,883
17
claim 37 under 35 U.S.C. § 103. We have, however, sustained
the rejection of claims 1 through 8, 30 through 36 and 38
through 43 under
35 U.S.C. § 103.
Accordingly, the examiner’s decision is affirmed-in-part.
No time period for taking any subsequent action in
connection with this appeal may be extended under
37 CFR § 1.136(a).
AFFIRMED-IN-PART
Appeal No. 95-2503
Application No. 08/024,883
18
Kenneth W. Hairston )
Administrative Patent Judge )
)
)
)
Errol A. Krass ) BOARD OF
PATENT
Administrative Patent Judge ) APPEALS AND
) INTERFERENCES
)
)
Lee E. Barrett )
Administrative Patent Judge )
Appeal No. 95-2503
Application No. 08/024,883
19
Ira S. Matsil
Texas Instruments Inc.
Patent Department, M/S 219
P.O. Box 655474
Dallas, TX 75265