Ex Parte Guo

Patent Trial and Appeal Board

May 24, 2016

11881627 (P.T.A.B. May. 24, 2016)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE
111881,627 07/27/2007
28112 7590 05/24/2016
SAILE ACKERMAN LLC
28 DAVIS AVENUE
POUGHKEEPSIE, NY 12603
FIRST NAMED INVENTOR
YiminGuo
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www .uspto.gov
ATTORNEY DOCKET NO. CONFIRMATION NO.
HMG07-002 1503
EXAMINER
KING, DOUGLAS
ART UNIT PAPER NUMBER
2824
MAILDATE DELIVERY MODE
05/24/2016 PAPER
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte YIMIN GUO
Appeal2014-002585
Application 11/881,627
Technology Center 2800
Before BRUCE R. WINSOR, DANIEL N. FISHMAN, and
NABEEL U. KHAN, Administrative Patent Judges.
FISHMAN, Administrative Patent Judge.
DECISION ON APPEAL
1A..ppellant appeals under 35 U.S.C. § 134(a) from a rejection of claims
3 and 4. 1 Claims 1, 2, and 5-10 are cancelled. Br. 2. We have jurisdiction
over the appealed claims under 35 U.S.C. § 6(b ).
We affirm.
1 In this Opinion, we refer to the original Specification ("Spec.," filed July
27, 2007); the Final Office Action ("Final Act.," mailed Nov. 30, 2012);
Appellant's Appeal Brief ("Br.," filed Aug. 8, 2013); and the Examiner's
Answer ("Ans.," mailed Oct. 16, 2013).
Appeal2014-002585
Application 11/881,627
THE INVENTION
Appellant's invention is directed to a magnetoresistive random-access
memory ("MRAM") cell structure that uses a plurality of sub-cells
connected in an electrically series arrangement. Spec. 8-9. Each sub-cell
includes a magnetic tunneling junction ("MTJ") that uses spin-polarized
current ("spin transfer") through one of the magnetic layers in the sub-cell
for switching purposes. Id. at 2-6. The total resistance of the series of sub-
cells is compared with a reference cell to determine the state of the memory
cell. Id. at 6, 9, 11-13; see also claim 3.2
Claim 3, reproduced below, is illustrative of the claimed subject
matter.
3. A spin transfer MRAM unit cell comprising:
a local transistor for providing a critical switching current
for changing the free layer magnetization of an MTJ sub-cell
element operating in a spin transfer mode so that the resistance
of said sub-cell changes between a low and a high resistance
state;
a horizontally directed word line contacting and
activating said transistor so that said critical switching current is
produced;
a horizontally directed bit line, vertically separated from
said word line and directed transversely to said word line;
a configuration ofN horizontally adjacent MTJ sub-cells,
wherein N is an integer greater than 1, each of said N MTJ sub-
cells being at a common vertical level and said configuration of
N MTJ sub-cells including a first MTJ sub-cell and an Nth MTJ
sub-cell and said N sub-cells being electrically connected in
linear series from said first sub-cell to said Nth sub-cell,
wherein each of said N MTJ sub-cells has the same multi-layer
2 According to the patent application, measuring the total resistance helps
increase accuracy of a read process, for example, by reducing the resistance
variations in the MTJ sub-cells. Id. at 8; see also claim 4.
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Appeal2014-002585
Application 11/881,627
structure with the same geometry and each sub-cell comprises,
in a vertically stacked configuration of horizontal layers, a
bottom electrode, a pinning layer, a synthetic pinned layer, a
tunneling barrier layer, a free layer and an upper electrode and
wherein
the bottom electrode of said first sub-cell of said
configuration electrically contacts said local transistor and the
top electrode of said first sub-cell electrically contacts the
bottom electrode of said second sub-cell, and wherein said
electrical contacts between adjacent pairs of sub-cells continue
in a sequential manner until the top electrode of the N-lth sub-
cell contacts the bottom electrode of the Nth sub-cell,
whereupon
the top electrode of said Nth sub-cell of said
configuration electrically contacts said bit line, and wherein
said top electrode and said bottom electrode of each pair
of adjacent sub-cells are vertically displaced from each other
and horizontally overlap, whereby said electrodes are placed in
electrical contact by means of a conducting via formed between
them, whereby
said critical switching current can pass from said
transistor, serially through each sub-cell to said bit line; and
a reference cell for performing resistance comparisons
with the total resistance of the series connection of said N sub-
cells.
THE REJECTION
Claims 3 and 4 were rejected under 35 U.S.C. § 103(a) over the
combined teachings of Durlam (US 2004/0125649 Al, filed Oct. 2, 2003),
Applicant's Admitted Prior Art ("APA" (Spec. 5---6)), and Nguyen (US
2004/0130936 Al, filed Jan. 7, 2003). Final Act. 2---6.
ANALYSIS
Only those arguments actually made by Appellant have been
considered in this Opinion. Arguments that Appellant did not make in the
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Application 11/881,627
Briefs have not been considered and are deemed to be waived. See
37 C.F.R. § 41.37(c)(l)(iv).
We have reviewed the Examiner's rejections in light of Appellant's
arguments that the Examiner erred. Br. 7-12. We are not persuaded by
Appellant's contentions. We adopt as our own and agree with the
Examiner's findings and reasons set forth in the action from which this
appeal is taken (Final Act. 2-7) and the Examiner's Answer (Ans. 3-9) in
response to Appellant's Appeal Brief. We highlight specific arguments and
findings for emphasis as follows.
As to claim 3, Appellant argues Dur lam teaches neither the recited
spin transfer technology nor the claimed reference cell. Br. 8. Appellant
also argues APA and Nguyen do not teach a series connection of sub-cells.
Id. at 11.
We are not persuaded by Appellant's argument, at least, because
Appellant's argument is not commensurate with the Examiner's rejection.
In rejecting claim 3, the Examiner finds Durlam (not APA or Nguyen)
teaches a series of connected sub-cells and finds APA and Nguyen (not
Durlam) teach the use of a reference cell to compare with the resistance of
an MTJ spin transfer cell. See Final Act. 2-5. Furthermore, one cannot
show non-obviousness by attacking references individually where the
rejection is based on a combination of references. See In re Merck & Co.,
Inc., 800 F.2d 1091, 1097 (Fed. Cir. 1986).
Appellant further argues there is no motivation to combine the cited
references because "Durlam is strongly teaching against external
comparisons with a reference cell having found a method for making the
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Application 11/881,627
comparisons internally, using only manipulations ('wiggles') of the
operating cell structure." Br. 8 (citing Durlam i-f 84).
We remain unpersuaded of Examiner error. Initially, we observe that
no portion of claim 3 distinguishes between "internal" versus "external"
comparisons using a reference cell. Claim 3 simply recites "a reference cell
for performing resistance comparison." Limitations not explicit or inherent
in the language of a claim cannot be imported from the specification. E-
P ass Techs., Inc. v. 3Com Corp., 343 F.3d 1364, 1369 (Fed. Cir. 2003).
Thus, the scope of claim 3 is not limited to an external reference cell as
suggested by Appellant.
Further, we agree with the Examiner that Durlam's teaching in
paragraph 84 does not, by itself, constitute a teaching away, unless it can be
shown that Durlam discourages a person of ordinary skill from using the
comparison method disclosed in the AP A and Nguyen. Ans. 5 (citing In re
Gurley, 27 F.3d 551, 553 (Fed. Cir. 1994)); see also In re Fulton, 391 F.3d
1195, 1201 (Fed. Cir. 2004) ("The prior art's mere disclosure of more than
one alternative does not constitute a teaching away from any of these
alternatives because such disclosure does not criticize, discredit, or
otherwise discourage the solution claimed .... "). Paragraph 84 of Durlam
suggests an alternative resistance comparison method but does not provide
sufficient persuasive evidence to show discouragement or criticism of an
alternative approach such as that suggested by the combination of Durlam
with AP A and Nguy en. Therefore, we are unpersuaded that Durlam teaches
away from the proposed combination. 3
3 We also reviewed related portions of Durlam that further elaborate on the
teachings in paragraph 84. Although we do not rely on these portions for
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Application 11/881,627
Appellant further argues that a motivation to combine or modify does
not exist because Durlam, due to certain structural features, neither benefits
from such modification, nor is capable of such modification. Br. 9-10. For
example, Appellant argues "Durlam's sequence of toggling operations
would probably not easily conform to a spin torque transfer technology ...
Examiner goes so far as to suggest that Durlam's circuit be entirely modified
to be a spin transfer MRAM." Id. at 10 (emphasis added). As support for
the above contention, Appellant refers to certain properties associated with
the use of spin transfer technology and certain naturally occurring
advantages associated with connecting sub-cells in series. Id. at 9-10.
Appellant's arguments emphasize Appellant's recognition of naturally
occurring advantages when a memory cell is formed from a plurality of sub-
cells connected in series. Br. 9 ("The series connection is provided precisely
because of its decreased sensitivity to statistical fluctuations.").
We remain unpersuaded of Examiner error. The Examiner relies on
Durlam for teaching a memory cell that is comprised of a plurality of sub-
cells connected in series and relies on APA and Nguyen, in combination
with Durlam, for teaching MTJ spin transfer cells are known structures
where comparing resistance of the MT J cell to a reference cell determines
the state of the cell. Final Act. 2-5. We agree with the Examiner.
The test for obviousness is not whether the features of a
secondary reference may be bodily incorporated into the
structure of the primary reference; nor is it that the claimed
this Decision, we note Durlam teaches a method for measuring the total
effective resistance of multiple sub-cells (MT J s ), which form a ganged cell
(memory cell), prior to a wiggle operation and comparing the effective
resistance with a reference resistance after the wiggle operation. See, e.g.,
Durlam i-fi-1 34, 69, 77.
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Appeal2014-002585
Application 11/881,627
invention must be expressly suggested in any one or all of the
references. Rather, the test is what the combined teachings of the
references would have suggested to those of ordinary skill in the
art.
In re Keller, 642 F.2d 413, 425 (CCPA 1981) (citations omitted).
Furthermore, Appellant does not provide sufficient persuasive evidence that
the structure of Durlam cannot be modified or will not be operational if the
Examiner's proposed modifications are implemented. Neither does
Appellant present persuasive evidence that the resulting arrangement was
"uniquely challenging or difficult for one of ordinary skill in the art" or
"represented an unobvious step over the prior art." See Leapfrog Enters.,
Inc. v. Fisher-Price, Inc., 485 F.3d 1157, 1162 (Fed. Cir. 2007).
We further note Appellant admits when "the option for a toggling
mechanism [as disclosed in Durlam] does not naturally exist[,] ... the use of
a comparison with a single reference cell is a sensible, practical and efficient
alternative." Br. 9. This admission supports the Examiner's articulated
reasoning that a person of ordinary skill would have been motivated to
modify Durlam in view of AP A and Nguy en to take advantage of faster
speeds and reduced power consumption as a result of incorporation of a
reference cell and spin transfer technology. Final Act. 5.
Accordingly, we find the Examiner has articulated sufficient
reasoning based rational underpinnings to support the legal conclusion of
obviousness. 4 Appellant has not persuaded us of error in the Examiner
reasoning for the proposed combination. Therefore, we are unpersuaded the
Examiner erred in rejecting claim 3 and we sustain the rejection thereof.
4 See In re Kahn, 441 F.3d 977, 988 (Fed. Cir. 2006).
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As to claim 4, Appellant argues:
[W] e agree that it is straightforward mathematics to show that
statistical variability of a series connection ofN sub-cells is
reduced by a factor ofN-112 . This simple, yet remarkable fact,
was a strong motivation and justification for the present
disclosure. However, in order to make efficient use of this
statistical "gift," the circuit in question should naturally involve
such series connections. In the present example of a spin
torque transfer MRAM, the situation presented itself for the
application of this statistical benefit and it was applied. In the
case of Durlam, the same situation did not naturally occur, so
Durlam found another method to achieve his goals.
Br. 12. Thus, Appellant admits reduction of the statistical variability of a
series connection ofN sub-cells by a factor ofN-112 is a naturally occurring
phenomenon and can be mathematically calculated. We find, because the
claimed naturally occurring properties are already present in the series
interconnected structure of Durlam' s sub-cells, the combination of the cited
references reads on claim 4. 5
Therefore, we sustain the rejection of dependent claim 4.
5 It is noteworthy that claim 4 is dependent on claim 1, a previously
cancelled claim, we presume it should be dependent on claim 3. Further,
because the recited properties in claim 4 are naturally occurring, claim 4
does not further limit the scope of the claim from which it depends.
Moreover, the term "it" as recited in claim 4 renders the claim indefinite
because it is unclear to which limitation "it" refers. Should there be further
prosecution of this application (including any review for allowance), the
Examiner may wish to review the claims for compliance under 35 U.S.C.
§ 112, first, second and fourth paragraphs.
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Appeal2014-002585
Application 11/881,627
DECISION
For the above reasons, the Examiner's decision rejecting claims 3 and
4 is affirmed.
No time period for taking any subsequent action in connection with this
appeal may be extended under 37 C.F.R. § 1.136(a)(l)(iv).
AFFIRMED
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