Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Specification
The title of the invention is not descriptive. A new title is required that is clearly indicative of the invention to which the claims are directed.
The following title is suggested: PHASE CHANGE MEMORY CELL HAVING A BI-LAYER HEATER SURROUNDING AN AIR GAP AND METHOD OF FORMING THE SAME
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
Claims 11 and 14 rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Claim 11 recites the limitation "a fourth dielectric contacting the first dielectric". There is insufficient antecedent basis for this limitation in the claim. It is unclear whether the first dielectric is the same or different from “a first dielectric material” of claim 10. The Examiner would assume this to be so for the purposes of examination, except for further uncertainty in the claim.
The Examiner has been unable to understand clearly from the Figures and Specification an element mapping satisfying all of claims 10, 11, and 14, which is required by the dependency. For example, the Examiner understands a mapping of claims 10 and 11 where element 15 of the Figures is “a first dielectric material”, element 9 is “a second dielectric material ”, element 5 is “a third dielectric material ”, and element 7 is “a fourth dielectric material ”; however, with this mapping, the fourth dielectric material does not appear to contact the first dielectric material, as required by claim 11, except as through the bi-layer heater, which would be one interpretation.
Continuing, claim 14, requires a first heater material (the Examiner has mapped this to element 12) contacting the first electrode (10), the third dielectric material (5), the fourth dielectric material (7), the phase change material (20), and a second heater material (14), in which case contact between 7 and 12 appears in Figs 9 and 10 to occur, if at all, only at an intersection of four material layers (12,7,9,5).
While understanding that the Figures may be only exemplary, the Specification does not provide additional clarity in regards to the above-mentioned contact between the fourth dielectric material and first dielectric material, or between the first heater material and the fourth dielectric material (claim 14). Because of this uncertainty, the scope of the claims is considered indefinite.
Claim 14 recites "the fourth dielectric material". There is insufficient antecedent basis for this limitation in the claim. It is unclear whether the fourth dielectric material is the same or different from “a fourth dielectric” of claim 11. The Examiner would assume this to be so for the purposes of examination, except for further uncertainty in the claim, as explained under claim 11.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1, 6, 9-10, and 12-13 are rejected under 35 U.S.C. 103 as being unpatentable over Cheng; Kangguo (US 2021/0210682; hereinafter Cheng) in view of Liu; Jun (US 2008/0121862; hereinafter Liu).
Regarding claim 1, Cheng discloses a phase change memory cell comprising:
a phase change material (260; Fig 8; ¶ [0058-67]) contacting a narrower top portion of a heater (250; Fig 8; ¶ [0058-67]);
the heater with a wider bottom portion of the heater contacting a first electrode (106; Fig 8; ¶ [0058, 0034]); and
a first dielectric material (240; Fig 8; ¶ [0058-67]) directly inside the heater and surrounding an air gap (245; Fig 8; ¶ [0062]) in a lower portion of the first dielectric material.
Cheng discloses the heater may include multiple conductive materials (¶ [0059]), but does not disclose the heater is a bi-layer heater.
In the same field of endeavor, Liu discloses a phase change memory cell comprising a heater (for example, 604; Fig 6; ¶ [0031-43]), the heater comprising a tapered shape and a plurality of layers of increasing resistivity towards a phase change material (608; Fig 6; ¶ [0031]), the tapered shape and resistivity gradient being structured to concentrate heating at the interface of the heater and the phase change material, which is directed towards optimization of switching between phases of the phase change material and correspondingly between a SET and RESET state of the cell, such optimization being a known problem/goal in the art (Liu; ¶ [0002-12]).
It would have been obvious to a person having ordinary skill in the art to combine the multi-layer heater structure of Liu with the heater structure of Cheng, essentially substituting or selecting a multi-layer structure for the multiple conductive materials disclosed for the heater of Cheng. One would have been motivated to do this in order to further optimize switching of a phase change cell, and benefit from the advantages of both disclosures. One would have had a reasonable expectation of success because of the similar structures, materials, and goals of Cheng and Liu.
Neither Cheng nor Liu specifically disclose a bi-layer heater for the multi-layer heater; however, one may have arrived at the number of layers of the multi-layer heater structure of Liu combined with Cheng as described above through routine optimization of the combined structure, and in consideration of a reduced width or thickness of the heater in the narrower upper portion surrounding a dielectric in the structure of Cheng. In this regards, a prima facie case of obviousness is considered met. See MPEP 2144.05.II.
Further, the substitution or selection of an optimized bi-layer heater structure in place of the heater structure Cheng could have been accomplished by known methods in the art by one of ordinary skill in the art, with a predicable result of the combined elements of the heater structures of Cheng and Liu performing the same as each does separately to provide a resistivity gradient and concentrate heating at the interface with the phase change material. In this regard also, a prima facie case of obviousness is considered met. See MPEP 2143.I.A.
Regarding claim 6, Cheng in view of Liu discloses the phase change memory cell of claim 1, wherein the narrower top portion of the bi-layer heater (Cheng; 250, according to claim 1; Fig 8) provides a ring of contact area with the phase change material (the top portion is shaped as a ring; ring heater; ¶ [0051-52]).
Regarding claim 9, Cheng in view of Liu discloses the phase change memory cell of claim 1, wherein the air gap (245; Fig 8) is adjacent to the wider bottom portion of the bi-layer heater (as shown in Fig 8; ¶ [0019])).
Regarding claim 10, Cheng discloses a phase change memory cell comprising:
a first dielectric material (240; Fig 8; ¶ [0058-67]) inside a heater (250; Fig 8; ¶ [0058-67]), wherein the first dielectric material surrounds an air gap (245; Fig 8; ¶ [0062]) adjacent to a wider bottom portion of the heater;
a first surface (upper surface) of a phase change material (260; Fig 8; ¶ [0058-67]) contacting a top electrode (270; Fig 8; ¶ [0064]); and
a second surface (lower surface) of the phase change material contacting the first dielectric material, the heater, and a second dielectric material (216; Fig 8; ¶ [0055]).
Cheng discloses the heater may include multiple conductive materials (¶ [0059]), but does not disclose the heater is a bi-layer heater.
In the same field of endeavor, Liu discloses a phase change memory cell comprising a heater (for example, 604; Fig 6; ¶ [0031-43]), the heater comprising a tapered shape and a plurality of layers of increasing resistivity towards a phase change material (608; Fig 6; ¶ [0031]), the tapered shape and resistivity gradient being structured to concentrate heating at the interface of the heater and the phase change material, which is directed towards optimization of switching between phases of the phase change material and correspondingly between a SET and RESET state of the cell, such optimization being a known problem/goal in the art (Liu; ¶ [0002-12]).
It would have been obvious to a person having ordinary skill in the art to combine the multi-layer heater structure of Liu with the heater structure of Cheng, essentially substituting or selecting a multi-layer structure for the multiple conductive materials disclosed for the heater of Cheng. One would have been motivated to do this in order to further optimize switching of a phase change cell, and benefit from the advantages of both disclosures. One would have had a reasonable expectation of success because of the similar structures, materials, and goals of Cheng and Liu.
Neither Cheng nor Liu specifically disclose a bi-layer heater for the multi-layer heater; however, one may have arrived at the number of layers of the multi-layer heater structure of Liu combined with Cheng as described above through routine optimization of the combined structure, and in consideration of a reduced width or thickness of the heater in the narrower upper portion surrounding a dielectric in the structure of Cheng. In this regards, a prima facie case of obviousness is considered met. See MPEP 2144.05.II.
Further, the substitution or selection of an optimized bi-layer heater structure in place of the heater structure Cheng could have been accomplished by known methods in the art by one of ordinary skill in the art, with a predicable result of the combined elements of the heater structures of Cheng and Liu performing the same as each does separately to provide a resistivity gradient and concentrate heating at the interface with the phase change material. In this regard also, a prima facie case of obviousness is considered met. See MPEP 2143.I.A.
Regarding claim 12, Cheng in view of Liu discloses the phase change memory cell of claim 10, wherein the bi-layer heater (Cheng; 250, according to claim 10; Fig 8) includes a narrower top portion and the wider bottom portion.
Regarding claim 13, Cheng in view of Liu discloses the phase change memory cell of claim 12, wherein the narrower top portion of the bi-layer heater is surrounded by the second dielectric material (Cheng; 216; as shown in Fig 8).
Allowable Subject Matter
Claims 15-20 allowed.
The following is a statement of reasons for the indication of allowable subject matter:
Regarding claim 15, the prior art of record, either singularly or in combination, does not disclose or suggest the combination of limitations including, primarily, “selectively depositing a layer of a third dielectric material on exposed surfaces of the second dielectric material; conformally depositing a first heater material on exposed surfaces of the bottom electrode, the first dielectric material, and the third dielectric material”, in combination with the additional limitations of the method claim. While methods of selective deposition are known in the art, the Examiner does not find the specific combination of limitations of the claim in the prior art and does not find that it would be obvious to a person having ordinary skill in the art to arrive at the combination of limitations of the claim.
Claims 2-5 and 7-8 objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
The following is a statement of reasons for the indication of allowable subject matter:
Regarding claim 2, the prior art of record, either singularly or in combination, does not disclose or suggest the combination of limitations including “a third dielectric on the second dielectric material directly contacts a sidewall of a fourth dielectric material”, in combination with the additional limitations of the claim and the base claim. The prior art Leobandung; Effendi (US 2020/0328347) discloses a related phase change memory cell wherein a dielectric 125 (Fig 11) directly contacts a sidewall of a dielectric 140. However, the structure of Leobandung comprises fewer dielectric layers, and the Examiner does not find it would be obvious to a person having ordinary skill in the art combine Leobandung or other prior art reviewed with Cheng or others to arrive at the limitations of claim 2.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure:
Min; Chung-Chiang (US 2009/0001050; the prior art discloses a method of forming a bottle-shaped trench comprising a selective deposition at an upper end of the trench);
Oh; Gyu-Hwan et al. (US 2008/0116437; the prior art discloses a phase change memory device comprising a multi-layer resistive heating element which may focus heat towards a phase change material);
Sato; Natsuki (US 2008/0210923; the prior art discloses a laminated heater which produces a successively increased specific resistivity towards a phase change material layer).
Wu; Chao-I (US 12029143; the prior art discloses a phase change memory device have a multi-layer heater wherein the layers have increasing resistivities).
Any inquiry concerning this communication or earlier communications from the examiner should be directed to BRAD KNUDSON whose telephone number is (703)756-4582. The examiner can normally be reached Telework 9:30 -18:30 ET; M-F.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Eliseo Ramos Feliciano can be reached at 571-272-7925. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/B.A.K./Examiner, Art Unit 2817
/ELISEO RAMOS FELICIANO/Supervisory Patent Examiner, Art Unit 2817
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