Case No. IPR2015-01087
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`________________________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`________________________
`
`MICRON TECHNOLOGY, INC., AND MICRON MEMORY JAPAN, INC.,
`Petitioners
`
`v.
`
`MASSACHUSETTS INSTITUTE OF TECHNOLOGY,
`Patent Owner
`________________________
`
`Case IPR2015-01087
`U.S. Patent No. 6,057,221
`________________________
`
`Patent Owner’s Preliminary Response to Petition for Inter Partes Review of
`U.S. Patent No. 6,057,221
`
`
`
`
`
`

`
`TABLE OF CONTENTS
`
`INTRODUCTION ..................................................................................................... 1
`BACKGROUND ....................................................................................................... 5
`I.
`Technology Background .................................................................................. 5
`Overview Of Laser Fuse Technology ....................................................... 5
`A.
`Thermal Resistance And Thermal Conductivity ....................................... 7
`B.
`Overview Of The ’221 Patent .......................................................................... 8
`II.
`CLAIM CONSTRUCTION ..................................................................................... 17
`REASONS FOR DENYING THE PETITION ....................................................... 17
`I.
`The Petition Is Time-Barred Under § 315(b) Because MIT Served
`Infringement Complaints On The Patent Over Two Years Ago ................... 18
`The Petition Should Be Declined Under § 325(d) Because It Is Duplicative
`Of The Reexamination Review Already Made By The Office ..................... 22
`III. The Petition Should Be Declined Under § 314(a) Because It Is Unlikely To
`Prevail With Respect To Any Challenged Claim .......................................... 24
`Claims 3-4, 6-8, 23, 25-26, And 28 Are Not Anticipated By Koyou ..... 24
`Principles of anticipation ................................................................... 24
`Overview of Koyou ............................................................................ 26
`Koyou fails to disclose “the width of the cut-link pad is at least ten
`percent greater than the width of each of the first and second
`electrically-conductive lines” (Claims 3-4, 6-8, 23, 25) .................... 28
`Koyou fails to disclose “the cut-link pad has substantially less
`thermal resistance per unit length than each of the first and second
`electrically conductive lines” (Claims 3-4, 6-8, 23, 25-26, 28) ......... 33
`Koyou does not anticipate any dependent claims of the ’221 Patent
`(Claims 6, 7, 8, 23, 25) ....................................................................... 41
`Koyou does not anticipate claims 26 and 28 ..................................... 43
`Claims 14, 15, And 29 Are Not Obvious Over Wada In View Of Lou
`(Ground 2) Or Billig (Ground 3) ............................................................. 43
`The petition should be denied for the same reasons that the CRU
`correctly allowed claims 14, 15, and 29 ............................................ 44
`There is no reason to combine Lou or Billig with either Wada or
`Koyou ................................................................................................. 47
`
`A.
`1.
`2.
`3.
`
`II.
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`4.
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`5.
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`6.
`B.
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`1.
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`2.
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`Case No. IPR2015-01087
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`3.
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`C.
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`Wada and the asserted combinations do not render obvious claims
`14, 15, or 29 because they do not disclose or render obvious “the cut-
`link pad is covered with a passivative layer that is harder than the
`substrate” ............................................................................................ 49
`Claims 3-4, 6-8, 23, 25-26, And 28 Are Not Obvious Over Koyou In
`View Of Wada (Ground 4) ...................................................................... 51
`The Bernstein declaration correctly supports the PTO’s determination
`that no challenged claim is unpatentable ........................................... 51
`A skilled artisan would not find it obvious to combine Koyou and
`Wada .................................................................................................. 54
`Claims 13, 17-18, 21-22, 24, 27, And 30 Are Not Obvious Over Koyou
`In View Of Lou (Ground 5), In View Of Billig (Ground 6), Or In View
`Of Wada In Further View Of Lou (Ground 7) Or Billig (Ground 8) ..... 59
`CONCLUSION ........................................................................................................ 60
`
`
`
`D.
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`1.
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`2.
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`Case No. IPR2015-01087
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`TABLE OF EXHIBITS
`
`
`Description
`Submission of Reorganization Claim to Tokyo District Court
`(October 31, 2012)
`Reorganization Claim Certificate of Receipt from Tokyo District
`Court (August 10, 2015)
`English Translation of Reorganization Claim Certification of Receipt
`Request (August 10, 2015)
`Petition to Tokyo District Court for Claim Assessment (December
`22, 2012)
`Trustee/MMJ Acknowledgement of Formal Service of the Petition
`for Claim Assessment (December 26, 2012) (and translations)
`Tokyo District Court Certificate of Receipt of Petition for Claim
`Assessment (August 10, 2015)
`English Translation of Certificate of Receipt of Petition for Claim
`Assessment Request (August 10, 2015)
`Ex Parte Reexamination Application No. 90/011,607
`Elpida News Release: Notice on Petition for Commencement of
`Corporate Reorganization Proceedings and Uncollectibility of Debts
`of Our Subsidiary (February 27, 2012)
`Opinion Staying Litigation in the United States, In re Elpida
`Memory, Inc., Case No. 12-10947 (Bankr. D. Del.)(November 20,
`2012)
`Tokyo District Court Notice of Result of Investigation (November
`14, 2012)
`Tokyo District Court Decision Regarding Corporate Reorganization
`(October 20, 2014)
`Micron Memory Japan, Inc’s Answer to Amended Complaint, MIT v.
`Micron, Case No. 1:15cv10374 FDS (U.S.D.M) (May 14, 2015)
`R.G. Sterne et al., “Reexamination Practice with Concurrent District
`Court Litigation or Section 337 USITC Investigations,” 2011
`Definition of “Plan View”, available at http://www.merriam-
`
`Exhibit #
`2001
`
`2002
`
`2003
`
`2004
`
`2005
`
`2006
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`2007
`
`2008
`2009
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`2010
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`2011
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`2012
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`2013
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`2014
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`2015
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`iii
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`2016
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`2017
`2018
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`2019
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`2020
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`2021
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`2022
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`2023
`2024
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`Case No. IPR2015-01087
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`webster.com
`S. Wolf et al., “Silicon Processing for the VLSI Era, Volume 1:
`Process Technology,” Second Edition, Lattice Press (2000)
`United States Patent No. 6,218,733
`Conductive Materials or Metal Conductivity, available at
`http://www.tibtech.com/conductivity.php
`K. Kawabata and T. Muto, “Electrical Properties of Titanium Nitride
`Thin Films Deposited by Reactive Sputtering,” Electrocomponent
`Science and Technology, 1981, Vol. 8, p. 249
`V. Mortet et al., “Titanium Nitride Grown by Sputtering for Contacts
`on Boron-Doped Diamond,” Plasma Process. Polym. 2007, 4, S139-
`S143
`Titanium nitride, available at
`http://en.wikipedia.org/wiki/Titanium_nitride
`Titanium – Comparison of Properties with Other Metals, available at
`http://www.amazon.com/article.aspx?ArticleID=1298
`S. Wolf, “Microchip Manufacturing,” Lattice Press (2004)
`Resistivity, Conductivity and Temperature Coefficients for some
`Common Materials, available at
`http://www.engineeringtoolbox.com/resistivity-conductivity-
`d_418.html
`
`
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`Case No. IPR2015-01087
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`INTRODUCTION
`
`Petitioners Micron Technology, Inc. (“Micron”) and Micron Memory Japan
`
`Inc. (“MMJ”)1 have filed a tardy petition seeking review of a patent that recently
`
`survived a full reexamination—based on the same core references that petitioners
`
`invoke here. The ’221 patent reflects groundbreaking technology in the
`
`semiconductor field; it introduced important advancements over the prior art, as
`
`the PTO reaffirmed in the reexamination. Petitioners had every opportunity to
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`seek review at the appropriate time, and they offer no legitimate basis to burden the
`
`Board or the parties with another request to rehash the same material. The petition
`
`should be denied.
`
`The Board should deny institution for at least three independent reasons.
`
`First, the petition is time-barred under 35 U.S.C. § 315(b):
`
`An inter partes review may not be instituted if the petition requesting
`the proceeding is filed more than 1 year after the date on which the
`petitioner, real party in interest, or privy of the petitioner is served
`with a complaint alleging infringement of the patent.
`
`MIT filed complaints for infringement of the ’221 Patent against petitioner MMJ
`
`and its bankruptcy Trustees—the “real party in interest”—in Japan on October 31,
`
`2012, and December 22, 2012. Exs. 2001 (Submission of Reorganization Claim)
`
`1
`MMJ was known formerly as Elpida Memory, Inc. Micron changed the
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`name to “Micron Memory Japan” when it acquired Elpida Inc. on July 31, 2013.
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`2002 (Certificate of Service from Tokyo District Court) 2003 (Translation of
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`certification of service); Ex. 2004 (Petition for Claim Assessment). The
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`complaints were served on these parties by December 26, 2012, making December
`
`26, 2013, the deadline for seeking an IPR; that deadline expired more than a full
`
`year before this petition was filed. Exs. 2005-2007 (Trustee/MMJ acknowledging
`
`formal service of the Petition for Claim Assessment). That statutorily disqualifies
`
`this petition from review.2
`
`Second, the Board should exercise its discretion to refuse review under 35
`
`U.S.C. § 325(d). Congress explicitly authorized the Board to take into account that
`
`“the same or substantially the same prior art or arguments previously were
`
`presented to the Office,” and to “reject the petition or request” on that basis. Id.
`
`That describes this situation exactly. The PTO has already verified the validity of
`
`the same claims over the same art during reexamination. And this was no ordinary
`
`review. Unlike routine pre-issuance examinations—which often involve long lists
`
`of prior art and disclosure statements—this reexamination subjected the ’221
`
`2 In direct contravention of the Board’s clear rules, petitioners failed to disclose
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`this earlier civil action in their petition. See 37 C.F.R. § 42.8(b)(2) (petitioners
`
`must disclose “any other judicial or administrative matter that would affect, or be
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`affected by, a decision in the proceeding”). Petitioners have no excuse for this
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`omission.
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`Patent to close scrutiny by three senior examiners focusing exclusively on the same
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`art and arguments raised in the petition. Nothing was conceivably lost or
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`overlooked. At the end of an exhaustive 18-month investigation, the PTO rejected
`
`petitioners’ alleged grounds for invalidity.
`
`The PTO has already devoted months of effort to studying the same prior art
`
`and deciding the same issues presented again in this petition. The Board should
`
`not devote its scarce resources to duplicating that effort. Congress sensibly
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`included Section 325(d) as a safe harbor to avoid unnecessary, burdensome,
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`repetitive proceedings. Tellingly, Section 325(d) even permits the Board to deny
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`review where the same art was previously considered merely as one part of a
`
`routine PTO examination. This art, by contrast, was deeply scrutinized as the
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`singular target of reexamination and multiple rounds of office actions. This case
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`falls directly in the heartland of Section 325(d).
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`Third, the petition substantively fails under 35 U.S.C. § 314(a). The cited
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`references fail to teach any of the challenged independent claims. The independent
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`claims specify in various combinations, limitations of relative width, relative
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`thermal resistance per unit length, a novel vertical structure, and relationships
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`between the substrate and passivation layers that the cited references fail to teach.
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`The relative greater width and lower thermal resistance per unit length of the cut-
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`link pad provide greater tendency to ablate, contrary to conventional wisdom that a
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`narrow pad would more readily ablate. Moreover, the vertical arrangement
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`facilitates manufacture of this novel design and protects desired circuity from
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`damage by overheating. And, a relatively harder passivity layer unexpectedly
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`facilitates beneficial upward fracturing, as opposed to undesired downward
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`cracking.
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`These breakthroughs were achieved by the MIT inventors through a level of
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`study never attempted in the art. Inter alia, the inventors performed detailed
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`investigation, careful analysis, and mathematical modeling of the initial moments
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`of the microscopic-fracturing process. This inventive work revealed that
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`prevailing wisdom, while intuitive, was wrong and produced sub-optimal laser-
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`fuse designs. This novel thinking was captured in the ’221 patent, easily
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`distinguishing the invention from the few references advanced in the petition.
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`The fact is that Micron and MMJ were unable to locate any new art, and that
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`alone is unusual and powerful evidence of novelty. As a combined entity, Micron
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`and MMJ are reportedly the second largest DRAM manufacturer in the world.
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`They have been involved in international litigation over the ’221 Patent for more
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`than 2.5 years. During months of preparing the petition, years of litigation, and
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`more years still discussing possible licensing, petitioners undoubtedly searched
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`exhaustively for new references to undercut the patent’s novelty. They found
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`nothing. Petitioners are left presenting the same failed art, reflecting the same
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`conventional thinking expressly raised and refuted in the ’221 Patent. The stark
`
`absence of new prior art highlights the petition’s defects. It cannot support any
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`ground of unpatentability, and it should be denied.
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`BACKGROUND
`
`I.
`
`Technology Background
`
`A. Overview Of Laser Fuse Technology
`
`Semiconductor manufacturers are in a constant race to reduce processing
`
`dimensions. Smaller dimensions accommodate more circuitry on a chip, lower
`
`costs, and increase processing speeds. But smaller dimensions also decrease the
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`margin for error. Ex. 1003 at 1:12-39. An imperfection that is acceptable in one
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`generation of products could render the next generation unusable. Id. In addition,
`
`an (exponential) increase in circuits means an (exponential) increase in potential
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`points of failure. Ex. 1003 (’221 Patent) at 1:12-39; Ex. 1006 (Koyou) at ¶1; Ex.
`
`1025 at 1:15-49; Ex. 1007 (Wada) at ¶1 (“[i]n general, the manufacturing yields for
`
`semiconductor circuit devices decrease as integration becomes higher”). High
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`error rates can produce a situation where most chips would fail if they had to rely
`
`on a unique set of circuits. See, e.g., Ex. 1025 at 1:15-49.
`
`For this reason, manufacturers build in redundant circuits: if one set fails,
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`others can be used in its place. Ex. 1003 at 1:33-47. This technique is highly
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`effective, but it requires disabling unused circuits. If not properly disabled, an
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`unused circuit itself can lead to failure.
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`Lasers can be used to sever redundant or defective circuits. Ex. 1003 at
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`1:10-25. This process is highly sensitive and complex. A laser beam is directed
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`onto a circuit’s fuse, supplying sufficient heat to ablate the part of the fuse and
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`sever the circuit. A single DRAM wafer, for example, may contain 10 million or
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`more fuses. Ex. 2008 (Ex Parte Reexamination Application No. 90/011,607
`
`(Submitted Article: A. Hooper, “Advances
`
`in Laser Technologies
`
`for
`
`Semiconductor Memory Yield and Repair Applications”)) at 149(pdf); see also
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`Petitioners’ Ex. 1025 at 1:56-57 (Prall - 1997 patent noting that a 256M DRAM—
`
`one chip—was expected to have more than 10,000 laser fuses). In a typical laser-
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`repair process, more than 2 million fuses (exceeding 20%) may be severed. Ex.
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`2008 (Submitted Article: P. Madsen The Laser User, Issue 57; Winter, 2009) at
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`157(pdf). In addition, the laser beam’s energy distribution is Gaussian,3 so there is
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`no clear delineation of the laser spot’s edge. This process—involving millions of
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`laser operations per wafer—thus requires exacting control of the laser beam and
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`3 “Gaussian” energy distribution means that, rather than being a defined, uniform
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`area of contact, the energy distribution of a laser “spot” is more realistically
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`represented by a “bell curve” function. In other words, most laser energy is
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`concentrated at the center of the laser spot; the energy then tapers off toward the
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`edges of the spot where, beyond a certain point, it becomes effectively
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`insignificant.
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`parameters to ensure the complete, clean severance of the fuse. Ex. 1003 (’221
`
`Patent) at 4:61-67. Even minimal changes to the structure of the circuit’s fuse have
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`substantial effects on yield and can mean the difference between profit and loss.
`
`Given the powerful motivation to optimize these connections, manufacturers
`
`generally do not overlook any potential modification that might improve yield.
`
`Thus, few improvements in this area are obvious or the product of routine analysis.
`
`B.
`
`Thermal Resistance And Thermal Conductivity
`
`Thermal resistance and thermal conductivity are key concepts in this field,
`
`and the former is partly defined by the latter. Thermal conductivity is an intrinsic
`
`property that defines how well a given material conducts heat. For instance, wood
`
`and plastics generally have low thermal conductivity, while metals generally have
`
`high thermal conductivity. Thermal resistivity is the inverse of thermal
`
`conductivity. It is an intrinsic property that defines how well a given material
`
`impedes heat flow. See, e.g., Ex. 1003 (’221 Patent) at 5:12-25.
`
`Thermal resistance, by contrast, is an extrinsic property of an object, a
`
`function of its thermal resistivity and dimensions. For example, by definition, a
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`three-foot-thick stone wall has the same thermal conductivity/resistivity as a three-
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`inch-thick stone wall. But the thermal resistance of the first wall would be twelve
`
`times greater than that of the second (measured with respect to heat flowing
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`perpendicular to the wall). While greater length in the direction of heat flow
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`results in greater thermal resistance, in real-world examples, thermal resistance is
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`also affected by an object’s cross-sectional area in the direction of heat flow. A
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`larger cross-sectional area of an object in the direction of heat flow functions as a
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`larger conduit for transferring heat and reduces the object’s thermal resistance;
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`similarly, a smaller cross sectional area in the direction of heat flow acts as a
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`smaller conduit and increases thermal resistance.
`
`II. Overview Of The ’221 Patent
`The ’221 Patent reflects the innovative work of Professor Joseph Bernstein
`
`and his then-graduate student, Zhihui Duan. It describes methods and structures
`
`for implementing a cut-link pad that defies conventional wisdom: it teaches
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`different dimensions and properties of the cut-link pad and lines, deals effectively
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`with the challenge of overlying passivation layers, and discloses embodiments
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`reconfigured into a novel vertical structure. These concepts and others are
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`reflected in the claims in various combinations
`
`The ’221 Patent was filed on April 3, 1997. At that time, the basic method
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`of circuit repair by laser ablation was to accumulate heat in the irradiated region
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`while minimizing the duration of laser exposure. Ex. 1003 at 1:51-56. If sufficient
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`heat is accumulated, the fuse will ablate. Id. Otherwise, if sufficient heat escapes
`
`before ablation, the fuse stays intact and the process likely fails. Ex. 1003 at 5:12-
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`20. Because a fuse is mostly surrounded by thermal insulators, heat primarily
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`escapes via adjoining electrically-conductive lines that lead to additional circuits.
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`Escaped heat can damage those lines and the interconnected circuitry, as can
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`extended laser exposure. Id.
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`Prevailing wisdom at the time dictated that fuses should be the same size or
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`narrower than abutting electrically-conductive lines. Ex. 1003 at 1:64-2:12. This
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`was supported by simple intuition. As noted above, a laser beam’s energy is not
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`uniformly distributed. Ex. 1003 at 4:61-67. According to conventional thinking,
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`minimizing the fuse’s volume would (i) require less laser energy for ablation; (ii)
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`promote clean and complete ablation, as there would be less material to remove;
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`(iii) reduce false connections or “shorts,” by limiting the amount of metal resettling
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`on the surface post-ablation; and (iv) ease efforts to encompass the fuse within a
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`given laser spot. Ex. 1003 at 1:49-2:34, 3:1-3:37, 5:59-6:12; see also, e.g., Ex.
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`1006 (Koyou) at ¶¶7, 17. This approach was also consistent with the general
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`directive to minimize circuit size. See e.g., Ex. 1025 at 2:7-11.
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`The conventional structure was also motivated by concerns that larger fuses,
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`particularly at the point of contact with the lines, would permit the laser’s heat to
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`travel easily from the laser’s central point of contact outward toward the lines (i.e.,
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`a wider fuse acts as a larger conduit for transferring heat). Ex. 1003 at 1:64-2:49.
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`This concern was especially relevant for horizontal fuse structures, which were
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`common at that time. Id. If the heat escaped, it could result in failed ablations and
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`damage interconnected circuitry. Id.
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`At the time of the invention, the inventors were researching how
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`microscopic laser fuses fracture upon impact, a precise analysis not performed in
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`any of the asserted prior art references. Dr. Bernstein and Mr. Duan discovered
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`that, when heat was allowed to flow freely from a cut-link pad to the adjoining
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`electrically conductive lines, and where the lines jumped to a higher thermal
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`resistance per-unit-length at contact points between the cut-link pad and the lines,
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`microscopic stress points form at the interface between the cut-link pad and the
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`lines. Ex. 1003 (’221 Patent) at 5:17-50, 6:57-7:50. They found that these stress
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`points created a cleaner point of severance than in the prior art discussed in the
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`background of the ’221 patent. Id. They also discovered that, in the microseconds
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`following initiation of laser ablation, a sharp temperature differential formed
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`between the pad and the lines. Id. This, in turn, creates a “boundary” within
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`which fracturing can occur that protects the lines, rather than allowing heat to flow
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`into them, as the prevailing wisdom wrongly suggested:
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`Increasing the width of the cut-link also improves the fracture
`mechanics during ablation. The fracture initiates and grows as a result
`of thermal stress at the interface of the cut-link and the surrounding
`material. The thermal stress, in turn, is a function of the energy
`density at the surface of the pad. The lines of maximum stress, from
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`which fractures typically propagate, are along the edge 36 of the pad
`20 forming the perimeter of the surface 38 facing the passivation layer
`30. The energy density along the maximum stress lines 36 is governed
`by the ratio of the energy absorbed to the length of the perimeter.
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`Ex. 1003 (’221 Patent) at 6:57-67. The inventors posited that energy density along
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`the perimeter (P) of the cut-link surface could be expressed by the function Ep =
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`k*S/P, where k is a constant, S is the surface area, and P is the perimeter. Id. at
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`7:1-21. Stress increases with energy, and the cracks grow. S, as an area (length x
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`width), grows at a quadratic rate, while P (perimeter) grows linearly. Id. As the
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`pad’s width increases, the ratio grows, and relative energy density increases at the
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`pad’s edges. Id. This allows fractures in a wider cut-link pad—particularly one
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`that has less thermal resistance per unit length than the surrounding electrically
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`conductive lines—to propagate with greater energy than fractures in a smaller or
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`narrower fuse, and allows the pad to retain more heat despite its relatively high
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`thermal conductance. Ex. 1003 at 7:10-21.
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`Thus, the ’221 patent discloses a cut-link pad that is at least ten percent
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`wider than the electrically conductive lines. In addition, as indicated, the
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`protective heat boundary and fracturing described above is optimized by imposing
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`a substantial increase in thermal resistance per unit length between the cut-link
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`pad and the electrically conductive lines. In addition to directing heat using
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`relative thermal resistance, the “per unit length” teaching allows for, inter alia, the
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`transition that builds the aforementioned beneficial concentration of energy at the
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`perimeter of the cut-link pad. Thus, for example, if a higher thermal resistance is
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`implemented by increasing length of the lines and not increasing thermal resistance
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`per unit of that length, precious laser energy could flow more readily into the lines
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`and the full benefits of this aspect of the patent would not be achieved.
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`The primary reference in the petition, Koyou, helps to illustrate the
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`conventions and drawbacks of the prior art with respect to width and thermal
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`resistance per unit length. Rather than widening the irradiated part of the fuse and
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`decreasing its thermal resistance relative to the lines, Koyou, in Fig. 1 (the so-
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`called “fundamental” invention illustration according to the petition), increases the
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`thermal resistance of the portion of the fuse situated in the area of the laser spot by
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`narrowing it at its contact points, thereby attempting to cause a heat bottleneck at
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`the point of laser impact (i.e., the opposite from the area of the laser beam’s impact
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`in the ’221 Patent’s teachings). Ex. 1006 (Koyou) at ¶17. The same concept is
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`reflected in Koyou’s Fig. 2: “Note that these portions 10a, 10b are formed from the
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`same material as the fuse member 10 in the present embodiment but other
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`materials may be used so long as they are electrically conductive materials. In this
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`case, electrically conductive materials are preferably selected that have thermal
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`resistances that are as great as possible.” Ex. 1006 (Koyou) at ¶17 (emphasis
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`added). Again, the general idea is to maximize “thermal resistance” on “portions”
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`10a and 10b of Koyou’s “fuse” to stifle heat flow to the wiring layers. The ’221
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`Patent, by contrast, showed this was neither necessary nor desirable.
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`In addition, Koyou specifically emphasizes making the fuse volume even
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`smaller than that shown in the then “conventional” art, thus further demonstrating
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`how the conventional fuse technology teaches away from the claimed invention:
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`“even with technology such as described above, wherein the insulating layer was
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`provided with a protruding portion in the portion directly under the fuse breaking
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`part, the volume of the fuse member itself was still large, and thus still had a large
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`thermal capacity.” Ex. 1006 (Koyou) at ¶7 (emphasis added). Koyou thus
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`demonstrates the conventional thinking before the ’221 Patent—that the fuses’
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`volume should be minimized to reduce thermal capacity—as the belief was that
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`greater volume led to increased capacity to absorb heat and thus increased the heat
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`needed for effective ablation. Koyou itself focuses on reducing thermal capacity
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`by shortening the length of the fuse. Id. The ’221 Patent upended these concepts
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`by increasing the thermal resistance per unit length of the lines relative to that of
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`the inventive cut-link pad, and increasing the width of the cut-link pad (thereby
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`increasing volume), which takes into consideration the 3-dimensional structure of
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`the pad and the lines and contributes to our understanding of fuse design and
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`physics significantly over the prior art.
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`Case No. IPR2015-01087
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`Indeed, other unexpected advantages of the width and thermal resistance
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`’221 Patent teachings follow. For example, the inventive, wider cut-link pad was
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`found to leave a larger void after irradiation, making it harder for stray metal to
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`reconnect lines after impact. Ex. 1003 at 5:59-6:12. In addition, by showing that a
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`direct transition to the lines with the claimed properties was advantageous, the ’221
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`patent obviated the perceived need for long fuse structures and complex or intricate
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`heat barriers found in the prior art, which add points of potential failure both in
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`manufacturing laser fuses pads and upon laser exposure.
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`None of petitioner’s art reflects these realizations or considers these effects.
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`At most, Koyou and Wada purport to consider basic heat accumulation-per-
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`volume, but devote scant attention to the specifics of how energy builds in an
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`irradiated region of a fuse or how fracturing occurs due to that accumulation.
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`Koyou’s asserted invention, for example, was decreasing fuse volume by
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`shortening it. Ex. 1006 (Koyou) at Figs. 1a, 6a, ¶¶3, 11, 13. Following
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`convention, the fuse’s contact part in its contact holes (2a and 2b) is described as
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`narrower than the wiring layers (3a and 3b). Ex. 1006 (Koyou) at Figs. 1a, 6a; see
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`also Part III.A.2, infra.
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`In addition, the inventors also taught how the patent’s advantages could be
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`realized in a vertical “via” structure. Ex. 1003 at 2:22-35; 8:20-48; Figs. 10, 11.
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`This reflected a major shift, especially in this conservative field. The patent’s cut-
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`link pads could be formed into a via structure where the lines extend into the
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`substrate. This design would further protect the lines from damage. Ex. 1003 at
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`Case No. IPR2015-01087
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`8:20-48.
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`Moreover, the inventors found that complete ablation was sometimes
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`unsuccessful because tiny cracks would form beneath the cut-link pad, permitting
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`melted metal to seep inside. Ex. 1003 at 6:19-44; 8:20-48; Fig. 5. This created an
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`electrical connection through the crack to the electrically-conductive line, which
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`could cause “shorts” (i.e., an unintentionally completed circuit). Id. The new
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`vertical design was susceptible to this problem because the lines were closely
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`spaced under the pad. Id. Because the inventors understood these additional
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`aspects of fracture formation, they realized the benefits of including a wide cut-link
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`pad particularly in a vertical structure; by increasing the distance between the
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`corners and the lines. While the prior art had sought to lower pad volumes to
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`thwart the re-settling of pad metal, the ’221 patent found that in this new vertical
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`design, positive and unexpected results could be enjoyed using even more material
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`than before. Id.
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`The ’221 Patent also contains claims related to a “passivative layer” or
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`“passivation layer.” Passivation layers protect exposed circuitry from oxidation.
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`Ex. 1003 (’221 Patent) at 6:19-44. The patents’ cut-link pads present a particular
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`challenge because the passivation layer applies a force or pressure on the pad, one
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`Case No. IPR2015-01087
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`which may be greater than that of the substrate under the pad. In addition, the
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`passivation layer must open as widely as possible so unablated material does not
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`re-harden on the coating’s remnants and short circuit after laser ablation. Id. The
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`inventors observed that expansion of the underlying cut-link pad and fractures
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`from its perimeter cause the passivation layer to open. Id. Similarly, the inventors
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`disclosed that using a widened cut-link pad offered a better way to separate the
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`passivation layer so fractures could form from the corners of the pad. Id.; see also
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`Id., Fig. 5.
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`The fracturing process also informed claims to the passivative layer. In the
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`alleged prior art, such as Lou and Billing, passivative layers were seen as a
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`constraint that should be minimized wherever possible. Ex. 1010 3:55-4:17. The
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`inventors, by contrast, examined ways to use the passivative layer to their
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`advantage, ultimately teaching how to make it from a harder material than the
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`substrate. This applies pressure to promote upward fracturing and inhibits cracks
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`down into the substrate. Ex. 1003 at 9:7-41. Based on their findings, the inventors
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`disclosed that a hard passivation layer (relative to the substrate) ca