Atty. Docket No. MIT -7581L-RX1
`
`IN THE UNITED STATES PATENT & TRADEMARK OFFICE
`
`IN RE PATENT OF:
`
`Joseph BERNSTEIN et al.
`
`PATENT NO.: 6,057,221
`
`SERIAL NO.: 08/825,808
`
`ISSUE DATE: May 2, 2000
`
`FILING DATE: April3, 1997
`
`CONTROL NO.: 90/011,607
`
`ASSIGNEES:
`
`MASSACHUSETTS INSTITUTE OF TECHNOLOGY;
`THE UNIVERSITY OF MARYLAND
`
`FOR: LASER-INDUCED CUTTING OF METAL INTERCONNECT
`
`I hereby certify that this document is being transmitted to the USPTO or deposited with the United States Postal
`Service as first class mail in an envelope addressed to Commissioner for Patents, P.O. Box 1450, Alexandria, VA
`22313-1450, on March 26, 2012.
`
`By: __________ ~/=J~u~d~y~R~v~a=n=/ ____________ _
`Judy Ryan
`
`DECLARATION
`
`Mail Stop EX PARTE REEXAM
`COMMISSIONER FOR PATENTS
`P.O. BOX 1450
`ALEXANDRIA, VA 22313-1450
`
`SIR:
`
`Now comes Joseph B. Bernstein, who declares and states that:
`
`1.
`
`I am an inventor in U.S. Pat. No. 6,057,221 (hereinafter the "'221 Patent"), which
`
`is the subject of this Ex Parte Reexamination.
`
`2.
`
`I am familiar with the subject matter disclosed and claimed in the above-identified
`
`patent, including the claims in the Preliminary Amendment filed on April14, 2011 (hereinafter
`
`IPR2015-01087 - Ex. 1016
`Micron Technology, Inc., et al., Petitioners
`1
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
`
`the "Preliminary Amendment") in this Reexamination. I am also familiar with the subject matter
`
`of the cited references (i.e., Koyou, Japan Pat. Appl. Pub. No. 8-213465, published Aug. 20,
`
`1996 [hereinafter "Koyou"], Wada, et al., Japan Pat. Appl. Pub. No. 6-244285, published Sep. 2,
`
`1994 [hereinafter "Wada"] and Lou et al., U.S. Patent No. 5,729,042 [hereinafter "Lou"]), and
`
`the evidence attached hereto as Exhibits A-N.
`
`3.
`
`I am currently a Professor in the School of Engineering, Bar Ilan University,
`
`Ramat Gan, Israel. I was awarded a Ph.D. in Electrical Engineering and Computer Science in
`
`1990 from the Massachusetts Institute of Technology, Cambridge, Massachusetts. My
`
`curriculum vitae is attached hereto as Exhibit A.
`
`I.
`
`The Rejection of Claim 3 Under 35 U.S.C. § 103(a)
`
`4.
`
`I understand that Claim 3 in the Preliminary Amendment is directed to a method
`
`for cutting a link between interconnected circuits, comprising the steps of (i) directing a laser
`
`upon an electrically-conductive cut-link pad conductively bonded between a first electrically(cid:173)
`
`conductive line and a second electrically-conductive line on a substrate, the cut-link pad having
`
`substantially less thermal resistance per unit length than each of the first and second lines,
`
`wherein the width ofthe cut-link pad is at least ten percent greater than the width of each of
`
`the first and second electrically-conductive lines, and (ii) maintaining the laser upon the cut-link
`
`pad until the laser infuses sufficient energy into the cut-link pad to break the conductive link
`
`across the cut-link pad between the pair of electrically-conductive lines, wherein the electrically(cid:173)
`
`conductive cut-link pad has an inner surface facing the substrate and an opposing outer surface
`
`facing away from the substrate, the first and second electrically-conductive lines extending from
`
`the inner surface into the substrate (emphasis added).
`
`5.
`
`I understand that Claim 3 has been rejected under 35 U.S.C. 103(a) for
`
`obviousness over Koyou in view ofWada.
`
`6.
`
`As further explained below, Claim 3 is patentable over the combination of Koyou
`
`and Wada because (1) the combination ofKoyou and Wada does not lead to the method of Claim
`
`2
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
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`3, (2) the method of Claim 3 runs contrary to conventional wisdom in the art, and (3) the method
`
`of Claim 3 provides unexpected results.
`
`1.
`
`The Combination ofKoyou and Wada Does Not Lead to the Present Invention
`
`7.
`
`Two of the most significant features of Claim 3 of the '221 Patent are (i) "the cut-
`
`link pad having substantially less thermal resistance per unit length than each of the first and
`
`second lines," and (ii) "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." Having both of these features in a
`
`cut-link pad in a vertical [use is particularly advantageous.
`
`8.
`
`The combination of Koyou and Wada does not lead to the present invention
`
`because (1) Koyou discloses a vertical fuse, but does not affirmatively disclose a cut-link pad
`
`having a width that is at least ten percent greater than the width of each of the first and second
`
`electrically-conductive lines, (2) Koyou does not disclose or suggest a cut-link pad having
`
`substantially less thermal resistance per unit length than each of the first and second lines, (3)
`
`W ada discloses a horizontal fuse, and therefore, does not cure the deficiencies of Koyou with
`
`regard to a cut-link pad having a width at least ten percent greater than the width of the
`
`electrically-conductive lines and a cut-link pad having substantially less thermal resistance per
`
`unit length in a vertical [use, and ( 4) one of ordinary skill in the art would not combine features
`
`from the horizontal fuse of Wada with the vertical fuse of Koyou.
`
`A.
`
`Koyou Does Not Affirmatively Disclose or Suggest a Cut-link Pad Having a
`Width That is at Least Ten Percent Greater Than the Width of the
`Conductive Lines
`
`9.
`
`Koyou discloses three embodiments of vertical fuses as shown in FIGS. 1-3. The
`
`three embodiments are discussed below. Claim 3 of the '221 Patent is distinguished over each of
`
`these three embodiments.
`
`10.
`
`Koyou discloses a fuse member (of length L) that can be disconnected by a laser
`
`beam, and interconnection layers 3a and 3b that are connected to the fuse member through
`
`contact holes 2a and 2b (see para. [0009], and FIG. 1(a) and 1(b) of Koyou; shown below).
`
`3
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
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`Koyou also discloses that the length L of fuse member 1 is less than or equal to the illumination
`
`spot diameter D of the laser beam 5 (see para. 0010 of Koyou), and that the fuse member 1 is
`
`structured to be, at the largest, about the same size as the illumination spot diameter of laser
`
`beam 5 so as to minimize the thermal capacity by minimizing the volume of fuse member 1 (see
`
`para. 0012 ofKoyou).
`
`(Q)
`
`11.
`
`FIG. 1(a) demonstrates that the width of the interconnection layers 3a and 3b is
`
`greater than the width of the material in the contact holes 2a and 2b. However, FIG. 1 also
`
`clearly shows that the material in the contact holes 2a and 2b is part of the [use member 1
`
`because the length L of the fuse member 1 includes the material in contact holes 2a and 2b, the
`
`material in the contact holes 2a and 2b is the same material as the material of the fuse (see the
`
`hatching in FIG. 1 (b)), the material in the fuse member 1 has a uniform thickness throughout its
`
`structure, and the laser directly irradiates material in the contact holes 2a and 2b (note the v(cid:173)
`
`shaped depression in the uppermost surface of fuse member 1 in the regions of contact holes 2a
`
`and 2b ). These facts clearly indicate that the same process (or series of process steps) forms fuse
`
`pad 1 and the material in the contact holes 2a-2b at the same time. Therefore, since the material
`
`4
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
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`Control No.: 90/011,607
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`in contact holes 2a and 2b is part of the fuse, this material cannot be the "electrically-conductive
`
`lines" conductively bonded to the fuse, as recited in Claim 3.
`
`12.
`
`Consequently, in the embodiment of FIG. 1, the only structure that can be the
`
`"electrically-conductive lines" are interconnection layers 3a and 3b. Koyou does not
`
`affirmatively disclose that the width of the fuse member 1 is at least ten percent greater than the
`
`width of interconnection layers 3a and 3b. In fact, the width of interconnection layers 3a and 3b
`
`is greater than the width of the contact holes 2a and 2b. Therefore, the interconnection layers 3a
`
`and 3b do not necessarily constrain the flow of heat/thermal energy from the fuse member 1.
`
`13.
`
`Similarly, as shown in the embodiment of FIG. 2 (see below), Koyou discloses a
`
`fuse member 10 having portions 1 Oa and 1 Ob, and underlying interconnection layers 11 a and 11 b
`
`below the fuse member 10 (see para. [0015] and FIG. 2 of Koyou). Koyou discloses that "the
`
`laser beam for disconnecting the fuse is selected to be approximately 5 J.lm, where the length L
`
`of the fuse member 10 must be formed to be at most 5 J.lm" (see para. [0016] and FIG. 2 of
`
`Koyou). Koyou further discloses that "as illustrated in FIG. 2, the cross-sectional areas of the
`
`individual portions 1 Oa and 1 Ob are selected to be smaller than the disconnection cross-sectional
`
`area of the fuse member 1 0," and that "by reducing the coverage rate of each of the conductive
`
`member portions 1 Oa and 1 Ob it is possible to achieve a relative increase in the thermal resistance
`
`of the contact portion relative to that of the fuse member 10" (see para. [0016] and FIG. 2 of
`
`Koyou).
`
`(F!G2)
`CllJY.;S-S<:CTIO!<At.
`·rHJ:· C:RHlC.·\.l
`&."H£M.~n(.:~Lt.Y nff: Sl'RtrCn.::t::r.
`f.W
`CW.·n'D!'li:SJ (Tlll> LMf.lt f(!S);}
`!>I A S!'MI<X>NcllX~H>R
`Dt.>'10i. AS Sr:r FORTH r~; .~ l'!R>l EX.~Ml'l.!: Of fMll<.1\1lMt.'N'l
`ACCO:~DlNG ·rn l"Hf: ltltJ~s:t:::-.rf it; Vi~~·~ no:~
`~~---....... _ ... _________ .,., .. ,, ... -.~----~------------~
`t(SO)
`.
`10
`~
`'
`'
`
`12
`
`.
`
`'lOa
`
`.'
`10b
`
`'110
`
`5
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
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`14.
`
`FIG. 2 of Koyou also clearly demonstrates that the length L of fuse member 10
`
`includes the portions 1 Oa and 1 Ob and that portions 1 Oa and 1 Ob are completely within the laser
`
`spot diameter D (i.e., L :::; D). Therefore, it is also clear that portions lOa and lOb of this
`
`embodiment are part of [use member 10 and are not "first and second electrically-conductive
`
`lines" as recited in Claim 3.
`
`15.
`
`Further, Koyou does not affirmatively disclose that the width of fuse member 10
`
`is at least ten percent greater than the width of interconnection layers lla and lib. Therefore,
`
`the interconnection layers 11 a and 11 b do not necessarily constrain the flow of heat/thermal
`
`energy from the fuse member 1 0.
`
`16.
`
`In the embodiment of FIG. 3 (see below), Koyou discloses a fuse member 20,
`
`contact holes 21 a and 21 b and interconnection layers 22a and 22b. The individual contact holes
`
`21 a and 21 b are connected to the fuse member 20 and to the underlying connection layers 22a
`
`and 22b using a "buried contact structure." The buried contact structure makes it possible to
`
`select material properties for the electrically conductive material buried within the contact holes
`
`to be different from the material of fuse 20 (see para. [0020] and FIG. 3 ofKoyou).
`
`(l'!G3)
`Dt.\.GRl-.M
`hLus·~~A'l't~..:{;
`C~o~s-Stct!oN.·~l~
`C~.lT!(",--\l
`.Sc~-n.-i.:...5.olo, nr:Au. Y ·n~E STRt~c:r:t..:R~
`nff."
`C>:f
`Cu~;,~fC!~~!~0:T (ll31: LASE~ HJ.~~:.) t~ -~ SRM!cnr4l;~.<:CH.)R
`nr-.VlCf. A.$ Stn F{)-Kf!-1 J~ ,..,: St:co: .. :r.;
`E-..1\.~V.-lfl..J~
`(>f
`f::?"~fi?A..)r>f:-..'E~;l" Ao:..:·o:t:.Oi~~G TO -rem PRf:~t::O.:T l'N'Vf,N1'JON
`
`(Rnri:>Rnl,)
`l.(,:iD}
`1' ......................................................... :>1
`! 23
`l
`20(R,,,)
`
`17.
`
`However, Koyou is silent with regard to the relative widths of the fuse member 20
`
`and the material filling each of the contact holes 21 a and 21 b. Thus, Koyou does not
`
`affirmatively disclose that 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.
`
`6
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
`
`18.
`
`At the time of Koyou's publication, line widths of 1.1-1.3 f.lm in the uppermost
`
`layer of metal were not uncommon (see, e.g., "Min metal 2 width" on pp. 10 and 11,
`
`respectively, of the Construction Analyses of the Lattice ispLSI2032-180L CPLD [hereinafter
`
`the "Lattice Analysis"] and the Samsung KM44C4000J-7 16 Megabit DRAM [hereinafter the
`
`"Samsung Analysis"], published by Integrated Circuit Engineering, Scottsdale AZ, Report Nos.
`
`SCA 9712-573 and SCA 9311-3001, respectively submitted herewith as Exhibits B & C). Also,
`
`it was not uncommon for the vias between the uppermost layer of metal and the next layer of
`
`metal therebelow in these devices to have a width of 1.0- 1.2 f.lm (see, e.g., "Min via" on p. 10
`
`of the Lattice Analysis and "Min via (metal2-to-metal1)" on p. 11 of the Samsung Analysis).
`
`Thus, while the uppermost layer of metal in the Lattice ispLSI2032-180L CPLD was arguably
`
`10% wider than the vias connected thereto (1.1 f.lm vs. 1.0 f.lm), the uppermost layer of metal in
`
`the Samsung KM44C4000J-7 16 Megabit DRAM was not (i.e., [1.3 - 1.2] I 1.2 = 8.3%). Thus,
`
`the width of the fuse member 20 disclosed in FIG. 3 of Koyou is not necessarily at least ten
`
`percent greater than the width of the material filling each of the contact holes 21 a and 21 b.
`
`B.
`
`Koyou Does Not Disclose or Suggest a Cut-link Pad Having Substantially
`Less Thermal Resistance Per Unit Length Than the Electrically-Conductive
`Lines
`
`19.
`
`FIG. 1(a) ofKoyou shows that the width of the interconnection layers 3a and 3b is
`
`greater than the width of the contact holes 2a and 2b. Since the material in the narrow contact
`
`holes 2a and 2b is part of the fuse, and at least part of the material in contact holes 2a and 2b is
`
`irradiated by the laser, the portions of the fuse pad 1 that are in the contact holes 2a and 2b have
`
`a thermal resistance that is greater than the thermal resistance of the interconnection layers 3a
`
`and 3b, if the material of the interconnection layers 3a and 3b is the same as that of the fuse
`
`member 1, including the material in the contact holes 2a and 2b. Thus, fuse member 1 of Koyou
`
`does not have substantially less thermal resistance per unit length than interconnection layers 3a
`
`and 3b.
`
`20.
`
`As illustrated in FIG. 2 of Koyou, the cross-sectional areas of the individual
`
`portions 1 Oa and 1 Ob are selected to be smaller than the disconnection cross-sectional area of the
`
`7
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
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`Control No.: 90/011,607
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`fuse member 10. By reducing the coverage rate of each of the conductive member portions lOa
`
`and 1 Ob, it is possible to achieve a relative increase in the thermal resistance of the contact
`
`portion relative to that of the fuse member 10. (See para. [0016] and FIG. 2 of Koyou.)
`
`However, as the thermal resistance of the portions 1 Oa and 1 Ob are increased, the thermal
`
`resistance of fuse member 10 is likewise increased, since portions 1 Oa and 1 Ob are part of the
`
`[use (see discussion ofKoyou in paragraph 10 above).
`
`21.
`
`Koyou discloses that the portions 1 Oa and 1 Ob in this embodiment are formed of
`
`the same material as the fuse member 10. However, portions lOa and lOb may also be formed
`
`from other materials, so long as they are electrically-conductive materials. Koyou states that
`
`"[i]n this case, electrically conductive materials should be selected that have thermal resistances
`
`that are as great as possible (see para. [0017] of Koyou; emphasis added). Consequently,
`
`because portions 1 Oa and 1 Ob are part of the fuse member 10, the fuse member 10 would have a
`
`correspondingly high thermal resistance.
`
`22.
`
`Further, it is clear from FIG. 3 ofKoyou that the width of the contact holes (vias)
`
`2la and 2lb (designated as "WV" below) is much greater than the thickness of the fuse member
`
`20 (designated as "TF" below). Based on measurements ofthe relative dimensions ofWV (e.g.,
`
`about 7.8 mm in the diagram below) and TF (e.g., about 4.7 mm in the diagram below) in FIG. 3
`
`of Koyou, the thickness TF of the fuse member 20 is approximately 60% of the width (WV) of
`
`the material in the contact holes 2la and 2lb (i.e., TF/WV::::: 0.6).
`
`8
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
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`Control No.: 90/011,607
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`TF
`
`220
`
`2'10 {RrHl}
`
`wv
`
`23.
`
`Although Koyou does not disclose the width of the fuse member 20 or the width
`
`of the contact holes 21 a and 21 b, based on (i) dimensions for these parameters that were
`
`arguably considered "state of the art" at the time of Koyou's publication, (ii) the approximate
`
`ratio of the thickness of the fuse member 20 to the width of the contact holes 21 a and 21 b as
`
`calculated from FIG. 3 of Koyou, and (iii) the thermal conductivity of the most likely or most
`
`commonly used metals for the fuse member 20 and the material in the contact holes 21 a and 21 b
`
`in FIG. 3 of Koyou, the fuse member 20 of Koyou does not necessarily have less thermal
`
`resistance per unit length than the material in the contact holes 21 a and 21 b, much less
`
`substantially less thermal resistance per unit length.
`
`24.
`
`For example, at the time of Koyou's publication, a width of 1.1 J.lm for the
`
`uppermost metal layer and a width of 1.0 J.lm for vias was not unusual (see the Lattice Analysis,
`
`p. 10). Thus, based on the via width from the Lattice Analysis and the ratio of fuse member
`
`thickness to via width calculated from FIG. 3 of Koyou, the thickness of the fuse member 20 is
`
`estimated to be 0.6 J.lm (i.e., 1.0 J.lm x 0.6, or 60%). Koyou discloses that the fuse member 20
`
`may be aluminum and the material filling the contact holes 21a and 21b may be tungsten (see
`
`paragraphs [0016] and [0021] of Koyou). Accordingly, based on the thermal conductivities of
`
`aluminum (i.e., 235 W/m-°K) and tungsten (i.e., 170 W/m-°K), the relative thermal conductance
`
`9
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`

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`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
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`Control No.: 901011,607
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`per unit length of (i) the fuse member 20 to (ii) the vias in contact holes 21a and 21 b in FIG. 3 of
`
`Koyou is estimated to be 155 : 170 (i.e., [1.1 x 0.6 x 235] to [1.0 x 1.0 x 170]). Thus, based on
`
`the widths of the uppermost metal layer and the uppermost via disclosed in the Lattice Analysis
`
`and the ratio of the thickness of fuse member 20 to the width of the vias in the contact holes 21 a
`
`and 21b in FIG. 3 of Koyou, the estimated thermal conductance per unit length of the fuse
`
`member 20 is less than the estimated thermal conductance per unit length of the material filling
`
`the contact holes 21 a and 21 b (i.e., the estimated thermal resistance per unit length of the fuse
`
`member 20 of FIG. 3 ofKoyou is greater than the estimated thermal resistance per unit length of
`
`the material filling the contact holes 21 a and 21 b).
`
`25.
`
`Likewise, using the dimensions of the uppermost metal layer and the uppermost
`
`vias in the Samsung Analysis (i.e., 1.3 J.lm and 1.2 J.lm respectively; see p. 11 of the Samsung
`
`Analysis), the estimated relative thermal conductance per unit length of the fuse member 20 to
`
`the material filling the contact holes 21a and 21b in FIG. 3 ofKoyou is 220: 245 (i.e., [1.3 x (1.2
`
`x 0.6) x 235] to [1.2 x 1.2 x 170]). Thus, based on the dimensions disclosed in the Samsung
`
`Analysis, the estimated thermal resistance per unit length of the fuse member 20 is greater than
`
`the estimated thermal resistance per unit length of the material filling the contact holes 21 a and
`
`21 b. Therefore, it cannot be said that the thermal resistance per unit length of the fuse member
`
`20 in FIG. 3 of Koyou is necessarily less than the thermal resistance per unit length of the
`
`material in the contact holes 21a and 21b, much less substantially less than the thermal
`
`resistance per unit length of the material in the contact holes 21 a and 21 b. Thus, even though
`
`Koyou discloses that the material filling each of the contact holes 21 a and 21 b has a higher
`
`thermal resistance than the fuse member 20 (see paragraph [0022]), it is not necessarily true that
`
`the material filling each of the contact holes 21 a and 21 b has a higher thermal resistance per unit
`
`length than the fuse member 20, because the ratio of (i) the cross-sectional area of the material
`
`filling each of the contact holes 21 a and 21 b to (ii) the cross-sectional area of the fuse member
`
`20 (i.e., [1.0 x 1.0] I [1.1 x 0.6] = 1.51 based on the Lattice Analysis or [1.2 x 1.2] I [1.3 x 1.2 x
`
`0.6] = 1.54 based on the Samsung Analysis) may be greater than the ratio of (i') the thermal
`
`conductance ofthe fuse member 20 to (ii') the thermal conductance of the material filling each of
`
`10
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`

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`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
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`Control No.: 90/011,607
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`the contact holes 21a and 21b (i.e., [235/170] = 1.38 based on an aluminum fuse member and
`
`tungsten in the contact holes).
`
`26.
`
`Thus, even though Koyou discloses that the material filling each of the contact
`
`holes 21a and 21b has a higher thermal resistance than the fuse member 20 (paragraph [0022] of
`
`Koyou), it is not necessarily true that the material filling each of the contact holes 21a and 21 b
`
`has a higher thermal resistance per unit length than the fuse member 20.
`
`27.
`
`The fuse structures recited in Claim 3 retain thermal energy more effectively than
`
`the fuse structures ofKoyou because (1) the conductive lines have a substantially higher thermal
`
`resistance per unit length than the fuse pad, thereby restricting the dissipative heat transfer into
`
`the conductive lines and improving the probability of a fuse being successfully cut by laser
`
`irradiation, and (2) the fuse pad has a width at least 10% greater than the conductive lines,
`
`thereby increasing the absorption of laser radiation and decreasing the probability of damage to
`
`the underlying structures.
`
`C. Wada Does Not Cure the Deficiencies of Koyou With Regard to the Two
`Most Significant Features of Claim 3
`
`28.
`
`As explained below, Wada does not cure the deficiencies ofKoyou with regard to
`
`a cut-link pad having (1) at least a ten percent greater width and (2) substantially greater thermal
`
`conductivity per unit length than the first and second electrically-conductive lines bonded thereto
`
`in a vertical fuse (i.e., a fuse wherein the electrically-conductive cut-link pad has an inner surface
`
`facing the substrate and an opposing outer surface facing away from the substrate, the first and
`
`second electrically-conductive lines extending from the inner surface into the substrate).
`
`29.
`
`In a first embodiment, Wada discloses a redundancy fuse 1 formed ofpolysilicon,
`
`polycide, aluminum or similar material having a fusing portion 1 a continuously provided
`
`between non-fusing portions 1 b. Wada also discloses that the width of the non-fusing portions
`
`1 b is approximately 1 J.lm and that the size of the fusing portion 1 a is set to be closer to the area
`
`of the irradiation region 4 of the laser light. For example, if the irradiation region 4 of the laser
`
`light is set to be an area of a circle with the diameter of 3 J.lm, the area of the fusing portion 1 a is
`
`P<~<TP 11 of 'J'\
`
`11
`
`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
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`set to be approximately 60% thereof, being a square with one side of 2 J.lm. (See para. [0010]
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`and FIG. 1 of Wada.) Wada further discloses that the fusing portion of the redundancy fuse in
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`this first embodiment is closer to the area of the irradiation region 4 of the laser light so that the
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`overlapping area of the irradiation region 4 and the fusing portion 1 a is larger than in a
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`conventional configuration, and the amount of laser light leaking to a lower layer is reduced (see
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`paras. [0012] and [0013] ofWada).
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`30.
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`In a second embodiment, Wada discloses that a redundancy fuse 5 is formed of a
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`fusing portion 5a positioned in the center of non-fusing portions 5b continuously provided on
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`both ends of the fusing portion 5a, in which a region 6 continuously provided on the both ends of
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`the fusing portion has a width that is smaller than the width of the periphery so that the heat
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`resistance is increased (see para. [0013] and FIG. 2 ofWada). In this embodiment, the widths of
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`the fusing portion 5a and the non-fusing portions 5b, excluding the region 6 are approximately 1
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`J.lm and a width of the region 6 is approximately 0.5 J.lm. Accordingly, the heat resistance of the
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`region 6 is higher than with a redundancy fuse with a uniform width. Thus, the escape of heat
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`generated in the fusing portion 5a is reduced (see paras. [0014] and [0015] ofWada).
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`31. W ada further discloses a third embodiment in which the heat resistance of the
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`region 6 is increased by providing slits 7 so as to increase the heat resistance of the region 6
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`compared to the periphery (see para. [0016] and FIG. 3 ofWada).
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`32.
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`The fuse structures disclosed in Wada are essentially horizontal structures,
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`because the fusing portion and the non-fusing portions are formed in the same layer of the device
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`and from the same material. Wada simply discloses (i) increasing the width of the fusing portion
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`so that the energy of the laser light can be effectively utilized, and (ii) decreasing the width of the
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`material in the regions 6 (either by narrowing the entire width as in FIG. 2, or creating a slit as in
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`FIG. 3) so as to increase the heat resistance of the regions 6, and thereby reduce the escape of
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`heat generated in the fusing portion.
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`33.
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`However, Wada fails to disclose or suggest a vertical fuse in which (i) the width
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`of the fuse is at least ten percent greater than the width of the first and second electrically-
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`12
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`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
`
`conductive lines conductively bonded thereto, and (ii) the fuse has substantially less thermal
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`resistance than each of the first and second electrically conductive lines. Vertical fuses have the
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`advantage of being manufacturable using structures having the smallest dimensions possible.
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`This is not the case with horizontal fuses, in which the width of the fuse is significantly wider
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`than the conductive lines thereto. Thus, if the fuse pad is to be at least ten percent wider than the
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`conductive lines, Wada requires that at least one dimension of the fuse (i.e., the width) is
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`increased well beyond the minimum width, so as to decrease the thermal resistance of the fusing
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`portion 5a compared to that of the non-fusing portions 5b.
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`D.
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`One of Ordinary Skill in the Art Would Not Combine Features From Wada
`With the Fuse of Koyou
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`34.
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`One of ordinary skill in the art would not combine features from the horizontal
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`fuse of Wada with the vertical fuse of Koyou because W ada and Koyou do not utilize a common
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`structure, and there are significantly different design considerations between the fuses of Koyou
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`and Wada.
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`35.
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`It is important to note that the structures disclosed in Koyou are vertical fuse
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`structures in which the electrically-conductive lines are in a metal layer under and/or below the
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`fuse pad, and wherein the fuse pad, the material in the first and second electrically-conductive
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`lines, and the underlying interconnection layers may be formed at different times and with
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`different materials. In contrast, the fuse structures disclosed in Wada are horizontal structures, in
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`which the fuse pad (i.e., the "fusing portion") and the first and second electrically-conductive
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`lines (i.e., the "non-fusing portions") are formed at the same time from the same material in the
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`same layer of metallization. Therefore, Koyou and W ada do not utilize a common structure. As
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`further explained below, the fundamental differences between a vertical fuse structure and a
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`horizontal fuse structure are significant, and one of ordinary skill in the art would generally not
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`look to a horizontal fuse for modifications to make in a vertical fuse, or otherwise combine
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`features of a horizontal structure with a vertical fuse structure.
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`13
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`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
`
`36.
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`In horizontal fuse structures, one dimension is constant (i.e., the thickness of the
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`fuse pad and the conductive lines is the same). Therefore, in horizontal structures, the only way
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`to make a cut-link pad having (i) a width greater than ten percent of the width of the conducting
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`lines or (ii) a thermal conductivity greater than that of the conductive lines is to increase the
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`width of the material in the pad area. This approach is generally disfavored in integrated circuit
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`manufacturing due to the desire to keep the lines as narrow as possible and make the integrated
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`circuit as small as possible. However, in vertical structures, no dimension in both of ( 1) the fuse
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`pad and (2) the electrically-conductive lines is necessarily constant. Therefore, as evidenced by
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`the Lattice Analysis and Samsung Analysis design rules (i.e., line widths and via widths), it is
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`not necessary to increase the width and/or length dimensions to make a larger pad. Additionally,
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`considerations more complex than simply the relative widths of the fuse member and the
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`connecting lines apply in a vertical fuse structure, such as the relative thicknesses of the fuse pad
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`and the width ofthe conductive lines (vias) extending into the substrate.
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`37.
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`Specifically, vertical fuses require processing in multiple layers of material,
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`whereas horizontal fuses do not. For example, in a vertical fuse, the length of the vias is
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`determined by the thickness of the dielectric material in which the vias are formed, and the width
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`of the vias is determined by patterning and etching the dielectric material. Additionally, in
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`vertical fuses, the identity of the via material is limited by the materials that can be deposited into
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`the via hole, and the length, width and thickness of the fuse pad is determined by the deposition
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`and/or patterning of the pad metal.
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`In a horizontal fuse, the only parameter that can vary
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`between the fuse pad and the first and second electrically-conductive lines is the length and
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`width of the pad, which is determined by the patterning of the pad metal. Because these
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`dimensions can be made as small as possible in a vertical fuse, one of ordinary skill in the art is
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`not motivated and would not look to a horizontal fuse for modifications to make to a vertical
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`fuse.
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`38.
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`Consequently, because of the differing structures and design considerations of a
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`vertical fuse as compared to a horizontal fuse, there is no reason for one of ordinary skill in the
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`art to look to the fuse of W ada for modifications to make to the fuse of Koyou.
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`14
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`

`
`Atty. Docket No. MIT-7581L-RX1
`U.S. Patent No.: 6,057,221
`
`Control No.: 90/011,607
`
`2.
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`The Present Invention Runs Contrary to the Conventional Wisdom in the Art
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`39.
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`The present invention runs contrary to the conventional wisdom in the art because
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`to convert the fuse of FIG. 3 of Koyou into one that necessarily has a pad with substantially less
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`thermal resistance per unit length than each of the first and second electrically-conductive lines
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`conductively bonded thereto (and thus arrive at Claim 3 of the '221 patent), one must (i) increase
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`the width of the fuse member 20, (ii) increase the thickness of the fuse member 20, and/or (iii)
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`decrease the widths of the vias 21 a and 21 b until the ratio of the cross-sectional area of the vias
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`21 a and 21 b to the cross-sectional area of the fuse member 20 is substantially less than the ratio
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`of the thermal conductances of the corresponding materials. As explained below, one of
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`ordinary skill in the art would not do so.
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`A.
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`Increasing the Width of the Fuse Member Is Contrary to the Accepted
`Wisdom in the Art
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`40.
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`Increasing the width of the fuse member 20 is contrary to the wisdom in the art.
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`The conventional wisdom in the art at the time of the present invention was to make devices
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`smaller, not larger, by decreasing the dimensions of structures in integrated circuits. For
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`example, one of ordinary skill in the art would have at least two compelling reasons not to
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`increase the width of the fuse member 20. First, as recognized by Gordon Moore as far back as
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`the mid-1960's, (see Moore, Electronics, Vol. 38, No. 8, April19, 1965; submitted herewith as
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`Exhibit D), the art has continuously made device dimensions smaller, not larger. For example,
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`Dr. Moore stated in 1965 that complexity for minimum component costs has increased at a rate
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`of roug