`
`United States Patent No. 6,538,324
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`
`
`
`
`
`
`Taiwan Semiconductor Manufacturing Company Limited
`
`Petitioner
`
`v.
`
`Godo Kaisha IP Bridge 1
`
`Patent Owner
`
`
`
`IPR2016-01264
`
`
`
`PETITION FOR INTER PARTES REVIEW
`OF UNITED STATES PATENT NO. 6,538,324
`
`
`
`
`
`
`
`
`
`
`Inter Partes Review
`United States Patent No. 6,538,324
`TABLE OF CONTENTS
`
`I.
`
`PRELIMINARY STATEMENT ................................................................... 1
`
`II. THE ’324 PATENT ........................................................................................ 6
`
`A. Overview of the ’324 Patent .................................................................. 6
`
`B.
`
`Prosecution History ............................................................................... 8
`
`III. Level of Ordinary Skill ................................................................................ 11
`
`IV. Claim Construction ..................................................................................... 11
`
`V. CLAIMS 1-3, 5-7, AND 9 OF THE ’324 PATENT ARE
`UNPATENTABLE OVER THE PRIOR ART ......................................... 12
`
`A. Overview of the Prior Art .................................................................... 12
`
`1.
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`2.
`
`3.
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`Zhang......................................................................................... 17
`
`Ding ........................................................................................... 18
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`Sun ............................................................................................. 18
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`B.
`
`The combined teachings of Zhang in view of Ding render
`claims 1-3, 5-7, and 9 obvious ............................................................ 20
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`1.
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`2.
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`3.
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`4.
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`5.
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`6.
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`7.
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`Claim 1 ...................................................................................... 20
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`Claim 2 ...................................................................................... 39
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`Claim 3 ...................................................................................... 43
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`Claim 5 ...................................................................................... 44
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`Claim 6 ...................................................................................... 46
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`Claim 7 ...................................................................................... 46
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`Claim 9 ...................................................................................... 46
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`C.
`
`The combined teachings of Zhang and Ding further in view of
`Sun render claims 1-3, 5-7, and 9 obvious .......................................... 48
`
`VI. MANDATORY NOTICES ......................................................................... 51
`
`A.
`
`B.
`
`C.
`
`D.
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`Real Party-in-Interest .......................................................................... 51
`
`Related Matters .................................................................................... 51
`
`Lead and Back-Up Counsel ................................................................. 54
`
`Service Information ............................................................................. 54
`
`VII. CERTIFICATION UNDER 37 C.F.R. § 42.24(d) .................................... 54
`
`VIII. GROUNDS FOR STANDING .................................................................... 55
`
`IX. STATEMENT OF PRECISE RELIEF REQUESTED FOR
`EACH CLAIM CHALLENGED ............................................................... 55
`
`X. CONCLUSION ............................................................................................ 55
`
`
`
`ii
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`TABLE OF AUTHORITIES
`
` Page(s)
`
`Case
`Atofina v. Great Lakes Chem. Corp.,
`441 F.3d 991 (Fed. Cir. 2006) ............................................................................ 42
`
`ClearValue, Inc. v. Pearl River Polymers, Inc.,
`668 F.3d 1340, 1345 (Fed. Cir. 2012) ................................................................ 42
`
`In re Cronyn,
`890 F.2d 1158, 1161 (Fed. Cir. 1989) .........................................................passim
`
`Cuozzo Speed Techs., LLC v. Lee,
`No. 15-446, slip op. (U.S. June 20, 2016) .......................................................... 11
`
`In re Hall,
`781 F.2d 897 (Fed. Cir. 1986) .....................................................................passim
`
`KSR Int’l Co. v. Teleflex Inc.,
`550 U.S. 398, 415-421(2007) ............................................................................. 26
`
`Titanium Metals Corp.v. Banner,
`778 F.2d 775 (Fed. Cir. 1985) ............................................................................ 43
`
`Statutes
`
`35 U.S.C. § 102 .................................................................................................passim
`
`35 U.S.C. § 103. ................................................................................................... 5, 55
`
`Other Authorities
`
`37 C.F.R. § 42.100(b) .............................................................................................. 11
`
`37 C.F.R. § 42.24 ..................................................................................................... 54
`
`M.P.E.P. (Rev. 07.2015) § 2143 .............................................................................. 26
`
`M.P.E.P. (Rev. 07.2015) § 2131.03 ......................................................................... 43
`
`P.T.A.B. Case No. CBM2012-00003, Paper No. 7 (Oct. 25, 2012) ........................ 52
`
`iii
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`Exhibit 1001:
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`Exhibit 1002:
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`Exhibit 1003:
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`Exhibit 1004:
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`Exhibit 1005:
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`Exhibit 1006:
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`Exhibit 1007:
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`Exhibit 1008:
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`Exhibit 1009:
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`Exhibit 1010:
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`Exhibit 1011:
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`Exhibit 1012:
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`Exhibit 1013:
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`Exhibit 1014:
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`LIST OF EXHIBITS
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`U.S. Patent No. 6,538,324 to Tagami et al.
`
`File History of U.S. Patent No. 6,538,324.
`
`Expert Declaration of Dr. Sanjay Kumar Banerjee.
`
`U.S. Patent No. 5,893,752 to Zhang et al.
`
`U.S. Patent No. 6,887,353 to Ding et al.
`
`Holloway et al., “Tantalum as a diffusion barrier between
`copper and silicon: Failure mechanism and effect of
`nitrogen additions,” Journal of Applied Physics, 71(11),
`5433-5444 (1992).
`
`Sun et al., “Properties of reactively sputter-deposited Ta-
`N thin films,” Thin Solid Films, 236 (1993) 347-351.
`
`U.S. Patent No. 5,858,873 to Vitkavage et al.
`
`U.S. Patent No. 5,668,411 to Hong et al.
`
`Excerpt of El-Kareh, “Fundamentals of Semiconductor
`Processing Technologies,” Kluwer Academic Publishers
`(1995).
`
`Declaration of Dr. Li Jiang.
`
`Library of Congress Catalog Record of Holloway et al.,
`“Tantalum as a diffusion barrier between copper and
`silicon: Failure mechanism and effect of nitrogen
`additions,” Journal of Applied Physics, 71(11), 5433-
`5444 (1992).
`
`Library of Congress Catalog Record of Sun et al.,
`“Properties of reactively sputter-deposited Ta-N thin
`films,” Thin Solid Films, 236 (1993) 347-351.
`
`Library of Congress Catalog Record of El-Kareh,
`“Fundamentals of Semiconductor Processing
`Technologies,” Kluwer Academic Publishers (1995).
`
`iv
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`
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`Exhibit 1015:
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`Exhibit 1016:
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`Exhibit 1017:
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`Exhibit 1018:
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`Exhibit 1019:
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`Exhibit 1020:
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`Exhibit 1021:
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`Exhibit 1022:
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`Stavrev et al., “Crystallographic and morphological
`characterization of reactively sputtered Ta, Ta-N and Ta-
`N-O thin films,” Thin Solid Films, 307 (1997) 79-88.
`
`Library of Congress Catalog Record of Stavrev et al.,
`“Crystallographic and morphological characterization of
`reactively sputtered Ta, Ta-N and Ta-N-O thin films,”
`Thin Solid Films, 307 (1997) 79-88.
`
`Duan et al., “Magnetic Property and Microstructure
`Dependence of CoCrTa/Cr Media on Substrate
`Temperature and Bias,” IEEE Transactions on
`Magnetics, Vol. 28, No. 5 (September 1992).
`
`Library of Congress Catalog Record of Duan et al.,
`“Magnetic Property and Microstructure Dependence of
`CoCrTa/Cr Media on Substrate Temperature and Bias,”
`IEEE Transactions on Magnetics, Vol. 28, No. 5
`(September 1992).
`
`Moussavi et al., “Comparison of Barrier Materials and
`Deposition Processes for Copper Integration,”
`Proceedings of the IEEE 1998 International Interconnect
`Technology Conference, pp. 295-97 (1998).
`
`Library of Congress Catalog Record of Moussavi et al.,
`“Comparison of Barrier Materials and Deposition
`Processes for Copper Integration,” Proceedings of the
`IEEE 1998 International Interconnect Technology
`Conference, pp. 295-97 (1998).
`
`Wijekoon et al., “Development of a Production Worthy
`Copper CMP Process,” 1998 IEEE/SEMI Advanced
`Semiconductor Manufacturing Conference, pp. 354-63
`(1998).
`
`Library of Congress Catalog Record of Wijekoon et al.,
`“Development of a Production Worthy Copper CMP
`Process,” 1998 IEEE/SEMI Advanced Semiconductor
`Manufacturing Conference, pp. 354-63 (1998).
`
`v
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`Exhibit 1023:
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`Exhibit 1024:
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`Wang et al., “Barrier Properties of Very Thin Ta and
`TaN layers Against Copper Diffusion,” J. Electrochem.
`Soc., Vol. 145, No. 7, pp. 2538-45.
`
`Library of Congress Catalog Record of Wang et al.,
`“Barrier Properties of Very Thin Ta and TaN layers
`Against Copper Diffusion,” J. Electrochem. Soc., Vol.
`145, No. 7, pp. 2538-45.
`
`vi
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`I.
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`PRELIMINARY STATEMENT
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`Inter Partes Review
`United States Patent No. 6,538,324
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`U.S. Patent No. 6,538,324 (Ex. 1001) “relates to a semiconductor integrated
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`circuit including a copper wiring layer.” Ex. 1001, 1:8-9. Semiconductor devices,
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`such as transistors, are typically formed using layers of material deposited on a
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`semiconductor substrate, such as silicon. Once formed, the semiconductor devices
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`comprise electrical terminals that are interconnected by one or more metal wiring
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`layers to form specific integrated circuitry, for example, in a processor. A metal
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`wiring layer is often deposited over an interlayer insulating layer, such as silicon
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`dioxide, which separates the metal wiring layer from underlying layers of the
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`semiconductor devices (such as MOSFET transistors). See, e.g., Ex. 1003, ¶ 39.
`
`At the time the application leading to the ’324 patent was filed, it was
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`understood that copper was a desirable metal for the wiring layer as devices
`
`became smaller because copper provides lower electrical resistivity than aluminum.
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`Ex. 1001, 1:13-19; see also Ex. 1003, ¶ 40. But it was also known that “it is
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`absolutely necessary for a semiconductor device having a copper wiring layer to
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`have a diffusion-barrier film for preventing diffusion of copper into an interlayer
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`insulating film formed between copper wiring layers.” Ex. 1001, 1:26-30.
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`Diffusion occurs when atoms or molecules migrate from an area of higher
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`concentration into an area of lower concentration. Ex. 1003, ¶ 40. At the time of
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`the ’324 patent, there was a recognized need in the art for a diffusion barrier that
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`would block the movement of copper from a wiring layer with a high concentration
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`of copper into an underlying insulating layer and semiconductor devices. See, e.g.,
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`id.; Ex. 1001, 1:22-25 (explaining that copper has a high diffusion rate in silicon
`
`and silicon dioxide, and if copper were to diffuse into a MOSFET formed on a
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`silicon substrate, it would induce a reduction in carrier lifetime in such a device).
`
`The ’324 patent specification admits it was known that the diffusion barrier
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`not only must prevent copper from diffusing out of the wiring layer into underlying
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`layers and devices, but also must provide good adhesion to the copper wiring layer.
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`Id., 2:13-15 (“As will be obvious to those skilled in the art, the diffusion-barrier
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`film is required to have high coverage as well as capability of preventing copper
`
`diffusion and adhesion to copper.”); see also id., 1:30-33.
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`The specification acknowledges the existence of several prior-art barrier
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`films for preventing diffusion of copper at the time of the alleged invention. Id.,
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`2:21-54, 7:52-57, FIGS. 1-3. In FIG. 1, the ’324 patent recognizes that two-layer
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`diffusion barrier structures were known in the art. Id., 7:51-52. With reference to
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`FIG. 2, the patent explains it was also known in the prior art that a diffusion barrier
`
`containing a crystalline film could provide good adhesion to a copper wiring layer,
`
`although it exhibited a “low barrier characteristic of preventing copper diffusion.”
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`Id., 3:1-4, 3:14-19. FIG. 3 of the ’324 patent shows it was known in the prior art
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`2
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`United States Patent No. 6,538,324
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`that amorphous (non-crystalline) films provide a good barrier to copper diffusion,
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`but they do not adhere well to copper. Id., 3:21-33; FIG. 3.
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`Because of this knowledge in the art, many in the field had already made
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`two-layer diffusion barriers that combined the advantages of a crystalline layer for
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`its known characteristics of providing good adhesion to copper and an amorphous
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`layer for its known property of preventing copper diffusion into underlying layers
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`and semiconductor devices, e.g., incorporating the prior-art films in FIGS. 2 and 3
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`into the barrier structure in FIG. 1. And more particularly, others had already made
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`two-layer diffusion barriers using a crystalline layer for providing good adhesion to
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`copper and an amorphous layer for preventing copper diffusion. Exactly like the
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`claims of the ’324 patent, the prior art included such two-layer diffusion barriers
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`with tantalum nitride (TaNx) as the amorphous layer and a tantalum (Ta) metal
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`containing nitrogen as the crystalline layer.
`
` U.S. Patent No. 5,893,752 (“Zhang,” Ex. 1004) discloses a two-layer
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`diffusion barrier having a bottom TaNx layer for preventing copper
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`diffusion and a top “tantalum-rich nitride film [that] is substantially
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`pure tantalum” for providing good adherence to a copper wiring layer.
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`3
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`United States Patent No. 6,538,324
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`Ex. 1004, Abstract, 2:29-40, 3:22-67, 5:49-59, FIG. 8 (multi-layer
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`diffusion barrier 22 and 32, copper wiring layer 54 and 64)1, FIG. 4.
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` U.S. Patent No. 6,887,353 (“Ding,” Ex. 1005), directed to the same
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`problem as the ’324 patent and Zhang, teaches that the TaNx layer in
`
`Zhang would be an amorphous layer and the adjacent layer of the
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`tantalum-rich tantalum nitride film would be crystalline. Ex. 1005,
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`Abstract, 3:33-38, 7:66-8:4.
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` Other prior art also discusses properties of Ta-based diffusion barriers
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`at different nitrogen contents for preventing copper diffusion. Sun et
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`al., “Properties of reactively sputter-deposited Ta-N thin films,” Thin
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`Solid Films, vol. 236, nos. 1-2, pages 347-351 (1993) (“Sun,” Ex.
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`1007) discloses that “In substantial atomic concentrations, nitrogen
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`can also promote the formation of amorphous metallic alloys with
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`most early transition metals,” such as Ta, and the resulting amorphous
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`films exhibit an “absence of fast diffusion paths” as compared with
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`polycrystalline films. Ex. 1007 at 9.
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`1 Zhang teaches the copper seed film 54 and copper wiring film 64 may be
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`replaced with a single copper film. Ex. 1004, 5:35-38.
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`4
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`The purported invention in the ’324 patent is a two-layer diffusion barrier to
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`prevent copper diffusion and provide good adhesion to a copper wiring layer.2 The
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`bottom layer in the barrier is an amorphous metal nitride to prevent copper
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`diffusion. See, e.g., id., Abstract, 9:50-52, 18:22-24. The top layer is a crystalline
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`metal that contains nitrogen to provide good adhesion to a copper wiring layer.
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`See, e.g., id., Abstract, 9:49-50, 18:24-26. The claims require the crystalline layer
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`of the diffusion barrier to contain less nitrogen than the amorphous layer. Id., 19:2-
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`3. The claimed two-layer diffusion barrier, combining known crystalline and
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`amorphous barrier layers, was not new and non-obvious at the time of the alleged
`
`invention. Several prior art references, such as Zhang and Ding, taught the same
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`two-layer barrier structure.
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`Because the combination of Zhang and Ding, or in the alternative the
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`combination of Zhang, Ding, and Sun, renders obvious each of claims 1-3, 5-7, and
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`9 in the ’324 patent under 35 U.S.C. § 103, Petitioner respectfully requests
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`cancellation of these claims.
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`2 The ’324 patent’s specification and claims refer to a barrier “film” (i.e., thin film)
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`having a multi-layered structure of first and second films. In this context, the words
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`“layer” and “film” are used interchangeably. Ex. 1003, ¶ 42.
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`5
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`United States Patent No. 6,538,324
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`II. THE ’324 PATENT
`A. Overview of the ’324 Patent
`The face of the ’324 patent indicates it was filed on June 19, 2000, issued on
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`March 25, 2003, and claims foreign priority to Japanese application 11-214110
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`filed on June 24, 1999. The patent contains claims 1-10, of which claims 1 and 5
`
`are independent. Claim 1 and its dependent claims 2-4 recite a barrier film
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`preventing diffusion of copper from a copper wiring layer formed on a
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`semiconductor substrate. Claim 5 and its dependent claims 6-10 recite a multi-
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`layered wiring structure comprising the barrier film in claim 1. Although the
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`specification describes specific steps for manufacturing the claimed multi-layered
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`wiring structure and barrier film, the claims are directed only to the structure and
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`barrier film, not to any manufacturing method.
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`Claim 1 reads as follows:
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`[1.0] A barrier film preventing diffusion of copper from a copper wiring
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`layer formed on a semiconductor substrate, comprising a multi-layered structure of
`
`first and second films:
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`[1.1] said first film being composed of crystalline metal containing nitrogen
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`therein,
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`[1.2] said second film being composed of amorphous metal nitride,
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`[1.3] said barrier film being constituted of common metal atomic species,
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`United States Patent No. 6,538,324
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`[1.4] said first film being formed on said second film,
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`[1.5] said first film in direct contact with said second film,
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`[1.6] said first film containing nitrogen in a smaller content than that of said
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`second film.
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`Claim 5 is substantially similar to claim 1. It reads:
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`[5.0] A multi-layered wiring structure comprising a barrier film which
`
`prevents diffusion of copper from a copper wiring layer formed on a
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`semiconductor substrate,
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`[5.1] said barrier film having a multi-layered structure of first and second
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`films,
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`[5.2] said first film being composed of crystalline metal containing nitrogen
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`therein,
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`[5.3] said second film being composed of amorphous metal nitride,
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`[5.4] said barrier film being constituted of common metal atomic species,
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`[5.5] said first film being formed on said second film,
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`[5.6] said first film in direct contact with said second film,
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`[5.7] said first film containing nitrogen in a smaller content than that of said
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`second film.
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`Claim elements [5.2]-[5.7] of claim 5 are identical to the claim elements
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`[1.1]-[1.6] of claim 1.
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`7
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`During prosecution, the PTO correctly explained that a device covered by
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`claim 1 “could be made by processes materially different from those” of the
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`specific method described in the specification. Ex. 1002 (’324 patent file history)
`
`at 202; Ex. 1003, ¶ 56 (Dr. Banerjee agreeing with PTO). The Applicant did not
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`disagree.
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`Prosecution History
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`B.
`The original application for the ’324 patent included claims 1-36. Claims
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`1-10 were directed to either a diffusion barrier film or a structure comprising the
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`diffusion barrier film, and claims 11-36 were directed to methods of forming either
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`the diffusion barrier film or a structure comprising the diffusion barrier film.
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`In an initial Office Action, the PTO restricted the claims into two distinct
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`groups and required election of one of the groups for examination. Group I
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`contained claims 1-10 “drawn to a semiconductor device,” and Group II contained
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`claims 11-36 “drawn to a method of making a semiconductor device.” Ex. 1002 at
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`202. The Applicant chose to prosecute Group I, claims 1-10, and withdrew all of
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`the method claims (claims 11-36) from consideration. Id. at 207.
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`The PTO issued a non-final rejection of claims 1-10 as anticipated or
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`rendered obvious by U.S. Patent No. 5,858,873 (“Vitkavage,” Ex. 1008). Id. at
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`210-12. In response, the Applicant amended the independent claims to recite “said
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`first film being formed on said second film” ([1.4] and [5.5]) and “said first film
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`United States Patent No. 6,538,324
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`containing nitrogen in a smaller content than that of said second film” ([1.6] and
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`[5.7]), seeking to distinguish the claims over Vitkavage because of these added
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`limitations. Id. at 219-23. The Applicant also added two new claims, corresponding
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`to claims 4 and 10 in the ’324 patent.
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`The PTO issued a final rejection finding the amended claims anticipated by
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`U.S. Patent No. 5,668,411 (“Hong,” Ex. 1009). The Applicant tried (Ex. 1002 at
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`231-36), but failed (id. at 237-39), to distinguish the claims over Hong, and
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`eventually filed a Request for Continued Examination. Id. at 240-41.
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`Along with the RCE, the Applicant further amended the independent claims
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`to recite “said first film in direct contact with said second film” ([1.5] and [5.6]).
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`Id. at 247-49. With the amendment, the Applicant distinguished Hong because it
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`lacked a top layer (“first film”) in direct contact with a bottom layer (“second
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`film”), whereas Hong disclosed “a seed layer 46 of the diffusion barrier film
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`positioned between the top layer 48 and the bottom layer 44.” Id. at 245. The PTO
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`allowed the claims in the next Office Action. Id. at 252-61.
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`During prosecution, the Examiner did not consider prior art that disclosed
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`the same claim elements he believed were missing from the art of record. For
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`example, the Applicant distinguished Vitkavage by arguing that Vitkavage does not
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`disclose “said first film being formed on said second film” ([1.4] and [5.5]) and
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`“said first film containing nitrogen in a smaller content than that of said second
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`United States Patent No. 6,538,324
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`film” ([1.6] and [5.7]). These elements are disclosed in Zhang, as shown in the
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`annotated FIG. 8 of Zhang below, which teaches a two-layer diffusion barrier
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`including a top, first film 32 (in blue) formed on a bottom, second film 22 (in red).
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`Annotated FIG. 8 of Zhang (Ex. 1004)
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`
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`In Zhang, the “deposition [i.e., depositing] of the two films 22 and 32 is
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`typically performed as one sequence during a single evacuation cycle,” where
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`nitrogen is applied during sputter deposition of the bottom, second film 22 and
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`then the nitrogen gas is turned off during the deposition of the top, first film 32 of
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`the diffusion barrier. Ex. 1004, 3:37-38. As a result, the first film 32 contains a
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`smaller nitrogen content than the second film 22. Compare Ex. 1004, 3:39-41 (film
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`22 contains TaN close to its stoichiometric composition, i.e., one-to-one atomic Ta
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`to atomic nitrogen, which is 50 atomic percent nitrogen) with id., 3:53-54 (film 32
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`contains 0-30 atomic percent nitrogen); see also id., FIG. 4.
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`10
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`United States Patent No. 6,538,324
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`Further, the claims were allowed after Applicant argued that Hong does not
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`disclose “said first film in direct contact with said second film” ([1.5] and [5.6]),
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`but the prior art discloses this claim element as well, such as in Zhang, which was
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`not before the Examiner during prosecution. See, e.g., Ex. 1004, FIG. 8 (annotated
`
`above, showing first film 32 in direct contact with second film 22).
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`III. Level of Ordinary Skill
`A person of ordinary skill in the art (“POSITA”) at the time the application
`
`leading to the ’324 patent was filed would have an equivalent of a Master of
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`Science degree from an accredited institution in electrical engineering, materials
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`science, or physics, or the equivalent, a working knowledge of semiconductor
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`processing technologies for integrated circuits, and at least two years of experience
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`in semiconductor processing analysis, design, and development. Ex. 1003, ¶ 64.
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`Additional graduate education could substitute for professional experience, and
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`significant work experience could substitute for formal education. Id.
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`IV. Claim Construction
`A claim in an unexpired patent subject to inter partes review receives the
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`“broadest reasonable construction in light of the specification of the patent in
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`which it appears.” 37 C.F.R. § 42.100(b); see also Cuozzo Speed Techs., LLC v.
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`Lee, No. 15-446, slip op. (U.S. June 20, 2016). The broadest reasonable
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`construction should be applied to all claim terms in the ’324 patent.
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`V. CLAIMS 1-3, 5-7, AND 9 OF THE ’324 PATENT ARE
`UNPATENTABLE OVER THE PRIOR ART
`A. Overview of the Prior Art
`The ’324 patent admits the inventors were not the first to recognize
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`problems associated with single-layer diffusion barriers for preventing diffusion of
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`copper and suggest a multi-layer solution. The specification recognized a desire for
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`a diffusion barrier “having a high barrier characteristic of preventing copper
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`diffusion and high adhesion to copper.” Ex. 1001, 3:47-49; see also 2:12-15. The
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`specification also acknowledges that a barrier layer formed only of a crystalline
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`metal film, such as a crystalline -Ta (002) film, was known to provide “good
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`adhesion” and “rich crystal orientation” (e.g., allowing a copper film to grow with
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`good adhesion), but would serve as a poor barrier to copper diffusion. Id., 3:14-20;
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`see also, Ex. 1003, ¶ 67. On the other hand, a diffusion barrier formed only of an
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`amorphous metal nitride would provide a better barrier to copper diffusion since it
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`“does not have the [grain-boundary] paths through which copper is diffused,” but
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`would suffer from poor adhesion because “copper crystallinity and adhesion to
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`copper are degraded” using an amorphous layer. Ex. 1001, 3:21-33; see also, Ex.
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`1003, ¶ 67.
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`The ’324 patent claims a two-layer diffusion barrier comprising adjacent
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`crystalline and amorphous films having different nitrogen contents. See, e.g., Ex.
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`1001, claims 1 and 5. In this multi-layer structure, the bottom film of the barrier
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`(substrate side) may be a prior-art amorphous metal nitride film, such as tantalum
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`nitride, and the top film (copper side) may be a prior-art crystalline metal film
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`containing less nitrogen than the bottom film. As discussed below, both the
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`problems with known diffusion barriers and the solution described in the ’324
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`patent were already known in the art.
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`Zhang discloses a “first conductive film” that serves as a multi-layer
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`diffusion barrier relative to a “second conductive film” that includes mostly
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`copper. Ex. 1004, Abstract. The first conductive film in Zhang is a two-layer
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`diffusion barrier film having top and bottom portions 32 and 22, with the bottom
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`film 22 lying closer to the substrate than the top film 32.3 Id. According to Zhang,
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`a “combination of portions (22 and 32) within the first conductive film provides a
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`good diffusion barrier (first portion) and has good adhesion (second portion) with
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`the second conductive film (54 and 64).” Id.
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`In Zhang, the top (32) and bottom (22) films are tantalum-based films with
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`different nitrogen contents. Id., 3:22-23. The “nitrogen percentage for the second
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`portion (32) is lower than the nitrogen atomic percentage for the first portion (22).”
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`Id., Abstract. Zhang thus recognized the same problems and the same two-layer
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`3 Zhang refers to the same thin films 22 and 32 as either “portions” or “films.” See,
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`e.g., Ex. 1004, Abstract (“portions (22 and 32)”), 3:37 (“films 22 and 32”).
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`solution as the ’324 patent. Indeed, Zhang meets every claim element of the ’324
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`patent, except it does not expressly mention the crystalline or amorphous nature of
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`the films 22 and 32 in the diffusion barrier.
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`Ding, however, does address the crystalline/amorphous nature of a two-film
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`diffusion barrier, and is directed to the same problems and solution as the ’324
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`patent and Zhang. Specifically, Ding discloses a two-layer “TaNx/Ta barrier
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`structure” that “provides both a barrier to the diffusion of a copper layer deposited
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`thereover, and enables the formation of a copper layer having a high <111>
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`crystallographic content so that the electromigration resistance of the copper is
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`increased.” Ex. 1005, Abstract.4 The diffusion barrier in Ding may consist of an
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`4 <111> are indices representing a set of equivalent directions in a crystalline
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`material. Ex. 1003, ¶ 51; see also Ex. 1010 at 11-12, which is a technical
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`publication that was catalogued and available to the public in the Library of
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`Congress in 1994. Ex. 1010 at 2 (showing Library of Congress stamp dated
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`December 21, 1994); Ex. 1014 (catalogue entry); Ex. 1011 at ¶ 5 (linking Ex. 1010
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`to Ex. 1014). Papers catalogued and available to the public in libraries, including
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`the Library of Congress, are sufficiently “publicly accessible” to serve as prior art.
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`See, e.g., In re Hall, 781 F.2d 897 (Fed. Cir. 1986); In re Cronyn, 890 F.2d 1158,
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`amorphous tantalum nitride bottom film for preventing copper diffusion (Ex. 1005,
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`Abstract), and a crystalline tantalum top film for “easy wetting of the tantalum
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`surface by the copper,” i.e., providing good adhesion to the copper layer, and
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`“depositing of a copper layer having a high <111> crystal orientation,” (Ex. 1005,
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`8:1-4). See also Ex. 1003, ¶ 72.
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`The bottom film of the two-layer diffusion barriers in both Zhang and Ding
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`consists of a tantalum nitride (TaNx) film, which Ding teaches may be an
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`amorphous thin film. Ex. 1005, Abstract. The TaNx film in Zhang is “close to the
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`stoichiometric composition (TaN),” such that x equals one using the TaNx
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`nomenclature. Ex. 1004, 3:39-41; see also id., 3:10-12 (“The tantalum nitride film
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`22 typically includes 33 to 50 atomic percent nitrogen with the balance essentially
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`being tantalum”). Ding discloses a “TaNx layer, where x ranges from about 0.1 to
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`about 1.5, is sufficiently amorphous to prevent the diffusion of copper into the
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`underlying substrate, which is typically silicon or a dielectric such as silicon
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`dioxide.” Ex. 1005, Abstract. Other prior-art references, such as Holloway et al.,
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`“Tantalum as a diffusion barrier between copper and silicon: Failure mechanism
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`and effect of nitrogen additions,” Journal of Applied Physics, vol. 71, no. 11, pages
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`1161 (Fed. Cir. 1989). Accordingly, Exhibit 1010 qualified as prior art at least one
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`year before the earliest priority date of the ’324 patent.
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`Inter Partes Review
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`United States Patent No. 6,538,324
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`5433-5444 (1992) (“Holloway,” Ex. 1006),5 and Sun, also describe properties of
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`various Ta-based diffusion barrier layers at different nitrogen contents. See, e.g.,
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`Ex. 1006, Abstract; Ex. 1007, Abstract.
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`Zhang discloses an embodiment in which the top film of the two-layer
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`diffusion barrier is a “tantalum-rich tantalum nitride film” that has an upper surface
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`which is “substantially pure tantalum.” Ex. 1004, 3:54-57, FIG. 4.6 The top film of
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`the barrier in Ding is also a tantalum layer, which Ding teaches is a crystalline film
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`with a <002> crystalline orientation. Ex. 1005, 8:1-4.
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`5 Exhibit 1006 was catalogued and available to the public in the Library of
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`Congress in 1992. Ex. 1006 at 3-4 (showing Library of Congress stamp dated June
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`17, 1992); Ex. 1012 (catalogue entry); Ex. 1011, ¶ 3 (linking Ex.