Continental Circuits LLC v. Intel Corporation ( 2019 )


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  •   United States Court of Appeals
    for the Federal Circuit
    ______________________
    CONTINENTAL CIRCUITS LLC,
    Plaintiff-Appellant
    v.
    INTEL CORPORATION, IBIDEN U.S.A.
    CORPORATION, IBIDEN COMPANY LIMITED,
    Defendants-Appellees
    ______________________
    2018-1076
    ______________________
    Appeal from the United States District Court for the
    District of Arizona in No. 2:16-cv-02026-DGC, Judge David
    G. Campbell.
    ______________________
    Decided: February 8, 2019
    ______________________
    JEFFREY A. LAMKEN, MoloLamken LLP, Washington,
    DC, argued for plaintiff-appellant. Also represented by
    MICHAEL GREGORY PATTILLO, JR., BENJAMIN THOMAS
    SIROLLY; BRADLEY WAYNE CALDWELL, JASON DODD
    CASSADY, JOHN AUSTIN CURRY, WARREN JOSEPH MCCARTY,
    III, Caldwell Cassady & Curry, Dallas, TX.
    JOSEPH J. MUELLER, Wilmer Cutler Pickering Hale
    and Dorr LLP, Boston, MA, argued for defendants-appel-
    lees. Also represented by KEVIN GOLDMAN, RICHARD WELLS
    O'NEILL, SARAH B. PETTY, KEVIN SCOTT PRUSSIA; NINA S.
    2           CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    TALLON, Washington, DC. Defendant-appellee Intel Cor-
    poration also represented by MATTHEW JOHN HULT, Intel
    Corporation, Santa Clara, CA.
    ______________________
    Before LOURIE, LINN, and TARANTO, Circuit Judges.
    LOURIE, Circuit Judge.
    Continental Circuits LLC appeals from the judgment
    of the United States District Court for the District of Ari-
    zona of noninfringement of the asserted claims of U.S. Pa-
    tents 7,501,582 (“the ’582 patent”); 8,278,560 (“the ’560
    patent”); 8,581,105 (“the ’105 patent”); and 9,374,912 (“the
    ’912 patent”). See Final Judgment, Cont’l Circuits LLC v.
    Intel Corp., No. 16-2026 (D. Ariz. Sept. 12, 2017), ECF No.
    273. The parties stipulated to a judgment of noninfringe-
    ment, see Stipulation & Joint Motion, Cont’l Circuits LLC
    v. Intel Corp., No. 16-2026 (D. Ariz. Sept. 7, 2017), ECF No.
    266, based on the district court’s claim construction of cer-
    tain claim terms, see Cont’l Circuits LLC v. Intel Corp., No.
    16-2026, 
    2017 WL 3478659
    (D. Ariz. Aug. 9, 2017) (“Claim
    Construction Order”). Because we conclude that the dis-
    trict court erred in its claim construction, we vacate the
    judgment of noninfringement and remand for further pro-
    ceedings.
    BACKGROUND
    Continental owns the ’582, ’560, ’105, and ’912 patents,
    which are directed to a “multilayer electrical device . . .
    having a tooth structure” and methods for making the
    same. See, e.g., ’582 patent Abstract. The four patents at
    issue, which have since expired, are continuations of one
    another and thus share substantially the same
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION                3
    specification. 1 According to the patents, multilayer electric
    devices “suffer from delamination, blistering, and other re-
    liability problems,” especially when “subjected to thermal
    stress.” 
    Id. col. 1
    ll. 30–32. The inventions of the patents
    purport to solve this problem by “forming a unique surface
    structure . . . comprised of teeth that are preferably angled
    or hooked like fangs or canine teeth to enable one layer to
    mechanically grip a second layer.” 
    Id. col. 1
    ll. 52–57. The
    specification further explains that the increased surface
    area of the teeth improves the adhesion of the layers to one
    another. See 
    id. col 1
    l. 58–col. 2 l. 6.
    The patents additionally “theorize[] . . . that the best
    methods for producing the teeth [are] to use non-homoge-
    nous materials and/or techniques . . . such that slowed
    and/or repeated etching will form teeth instead of a uni-
    form etch.” 
    Id. col. 2
    ll. 24–29. The specification then ex-
    plains that “[o]ne technique for forming the teeth is . . . the
    swell and etch or desmear process, except that contrary to
    all known teachings in the prior art . . . a ‘double desmear
    process’ is utilized.” 
    Id. col. 5
    ll. 40–44. It continues by
    explaining that “the peel strength produced in accordance
    with the present invention is greater than the peal [sic]
    strength produced by the desmear process of the prior art,
    i.e., a single pass desmear process.” 
    Id. col. 7
    ll. 3–6. The
    specification then discloses that “[i]n stark contrast with
    the etch and swell process of the known prior art . . . a sec-
    ond pass through the process . . . is used” because it
    “make[s] use of [the] non-homogenaities [sic] in bringing
    about a formation of the teeth.” 
    Id. col. 9
    ll. 1–5.
    Continental sued Intel Corp.; its supplier, Ibiden
    U.S.A. Corp.; and Ibiden U.S.A. Corp.’s parent company,
    Ibiden Co. Ltd. (collectively, “Intel”), for patent
    1   In this opinion, citations are only to the ’582 patent
    specification because the specifications of the four patents
    are substantially identical.
    4            CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    infringement in the District of Arizona. Continental as-
    serted claims 85, 87, 89, 92, 94, 95, 100, 109, 114, and 122
    of the ’582 patent; claims 14 and 19 of the ’560 patent;
    claims 13, 53, 71, 80, 82, 86, 88, 91, 95, 97, 101, and 103 of
    the ’105 patent; and claims 2, 3, 18–20, and 26–28 of the
    ’912 patent. All of the asserted claims include claim limi-
    tations regarding the “surface,” “removal,” or “etching” of
    “a dielectric material” or “epoxy,” which the district court
    construed together as the “Category 1 Terms,” and their
    construction depends on resolving whether they should be
    limited to a repeated desmear process. See Claim Con-
    struction Order, 
    2017 WL 3478659
    , at *2; see also J.A.
    1879–89. 2
    Claim 100 of the ’582 patent is illustrative of a claim
    that includes a “surface” claim term and reads as follows:
    100. An electrical device including:
    a conductive layer built up so as to fill undercut-
    tings with respect to a surface of a dielectric mate-
    rial so as to form teeth in cavities, a plurality of the
    undercuttings being obtuse to the surface, wherein
    2   The Category 1 Terms include “surface,” “removal,”
    and “etching” related claim terms:
    • The “surface” claim terms are “surface of a dielectric
    material,” “surface of a layer of a dielectric mate-
    rial,” and “a dielectric material comprising a sur-
    face.”
    • The “removal” claim terms are “removal of a portion
    of the dielectric material,” and “removal of some of
    the dielectric material.”
    • The “etching” claim terms are “etching [of] the
    epoxy” and “etching [of] the dielectric material.”
    The district court construed all of these claim terms to-
    gether.
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION                5
    the conductive layer is a portion of circuitry of an
    electrical device, and a plurality of the teeth are
    within the range of 1 tenth of a mil deep to 1.75
    tenths of a mil deep, and
    wherein at least one of the cavities includes an up-
    grade slope with respect to the surface of the dielec-
    tric material, and one of the teeth engages a portion
    of the dielectric material at the slope.
    ’582 patent col. 18 ll. 48–59 (emphases added).
    Claim 114 of the ’582 patent is representative of a claim
    that includes a “removal” claim term and reads as follows:
    114. An electrical device including:
    a dielectric material having a surface remaining
    from removal of a portion of the dielectric material;
    and
    means for mechanically gripping a conductive layer
    to the surface of the dielectric material so that the
    conductive layer is burrowed in and under the top
    surface of the dielectric material, wherein the con-
    ductive layer forms a portion of circuitry of an elec-
    trical device, wherein the means for mechanically
    gripping is comprised of teeth, and a plurality of
    the teeth are within the range of 1 tenth of a mil
    deep to 1.75 tenths of a mil deep, and
    wherein at least one of the cavities includes an up-
    grade slope with respect to the surface of the die-
    lectric material, and one of the teeth engages a
    portion of the dielectric material at the slope.
    
    Id. col. 2
    0 ll. 30–44 (emphasis added).
    Claim 14 of the ’560 patent is representative of a claim
    that includes an “etching” claim term and reads as follows:
    14. An article of manufacture, the article compris-
    ing:
    6           CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    an epoxy dielectric material delivered with solid
    content sufficient that etching the epoxy forms a
    non-uniformly roughened surface comprising cavi-
    ties located in and underneath a surface of the die-
    lectric material, and sufficient that the etching of
    the epoxy uses non-homogeneity with the solid con-
    tent to bring about formation of the non-uniformly
    roughened surface with at least some of the cavities
    having a first cross-sectional distance proximate
    the initial surface and a substantially greater
    cross-sectional distance distant from the initial
    surface, and
    a conductive material, whereby the etching of the
    epoxy forms the cavities, and a portion of the con-
    ductive material in the cavities thereby forming
    teeth in the cavities, wherein the etching of the
    non-homogeneous composition forms the cavities,
    and wherein the conductive material forms a por-
    tion of circuitry of an electrical device.
    ’560 patent col. 10 ll. 7–25 (emphases added).
    Aside from the “device” and “article of manufacture”
    claims recited above, the asserted claims also include pro-
    cess and product-by-process claims. Claims 2 and 18 of the
    ’912 patent are illustrative and read as follows:
    2. A process of making an article of manufacture,
    the process comprising:
    implementing a circuit design for an electrical de-
    vice by coupling a dielectric material delivered with
    solid content, the dielectric material and the solid
    content being non-homogeneous materials, suffi-
    cient that etching the dielectric material forms a
    non-uniformly roughened surface comprising cavi-
    ties located in, and underneath a surface of, the di-
    electric material, and sufficient that the etching of
    the dielectric material uses non-homogeneity with
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION                 7
    the solid content in bringing about formation of the
    non-uniformly roughened surface with at least
    some of the cavities having a first cross-sectional
    distance proximate the surface and a greater cross-
    sectional distance distant from the surface, with
    a conductive material, whereby the etching of the
    dielectric material forms the cavities, and a portion
    of the conductive material in the cavities thereby
    forming teeth in the cavities, wherein the etching
    of the non-homogeneous composition forms the cav-
    ities, in circuitry of the electrical device.
    ....
    18. A product produced by the process of claim 2.
    ’912 patent col. 9 l. 58–col. 10 l. 11, col. 11 l. 14.
    The district court construed the Category 1 Terms to
    require that the “surface,” “removal,” or “etching” of the di-
    electric material be “produced by a repeated desmear pro-
    cess.” See Claim Construction Order, 
    2017 WL 3478659
    , at
    *2–3 (emphasis added). The district court concluded that
    Intel had “met the exacting standard required” to read a
    limitation into the claims. 
    Id. at *3.
    Specifically, the dis-
    trict court found that the specification not only “repeatedly
    distinguishe[d] the process covered by the patent from the
    prior art and its use of a ‘single desmear process,’” 
    id. at *4,
    but also characterized “the present invention” as using a
    repeated desmear process, see 
    id. at *5.
        Additionally, the district court found that the prosecu-
    tion history corroborated its construction. The examiner
    made indefiniteness and written description rejections dur-
    ing the prosecution of the ’560 patent of the claim limita-
    tion “etching of the epoxy uses non-homogeneity with the
    solid content,” which is used to bring about formation of the
    non-uniformly roughened surface of the angular tooth-
    shaped cavities. See J.A. 2122–23. In response to the office
    action, Continental submitted an expert declaration
    8           CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    explaining that the “etching” process disclosed in the spec-
    ification uses “this known Probelec XB[ ]7081 resin” and
    “two separate swell and etch steps” as “a technique which
    forms the teeth.” J.A. 2074; see also J.A. 2068–69. The
    district court found that the expert declaration “clearly de-
    scribe[d] the patented method as involving two etching pro-
    cesses.” Claim Construction Order, 
    2017 WL 3478659
    , at
    *6. Moreover, the district court observed that extrinsic doc-
    uments produced by the inventors state the use of a “two
    pass desmear cycle” and that “we use a double pass
    desmear to achieve the tooth structure.” 
    Id. (quoting J.A.
    3321, 3324). The court acknowledged that those state-
    ments were “not reliable enough to be dispositive,” but
    found they “provide[d] helpful corroboration.” 
    Id. Based on
    the court’s claim construction and the fact
    that all of the asserted claims involve the question whether
    they should be limited to a repeated desmear process, the
    parties stipulated to noninfringement and the court en-
    tered judgment accordingly. On appeal, Continental chal-
    lenges only the district court’s claim construction. We have
    jurisdiction under 28 U.S.C. § 1295(a)(1).
    DISCUSSION
    Claim construction is ultimately a question of law that
    we review de novo. Teva Pharm. USA, Inc. v. Sandoz, Inc.,
    
    135 S. Ct. 831
    , 841 (2015). Any subsidiary factual findings
    based on extrinsic evidence “must be reviewed for clear er-
    ror on appeal.” 
    Id. But “when
    the district court reviews
    only evidence intrinsic to the patent (the patent claims and
    specifications, along with the patent’s prosecution history),
    the judge’s determination will amount solely to a determi-
    nation of law,” which we review de novo. 
    Id. Continental argues
    that the district court erred in con-
    struing the Category 1 Terms to require that the dielectric
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION               9
    material be “produced by a repeated desmear process.” 3
    See Claim Construction Order, 
    2017 WL 3478659
    , at *2–3.
    Continental contends that the plain language of the claims
    does not include a repeated desmear process. Also, accord-
    ing to Continental, the specification does not clearly and
    unmistakably limit the claims to require a repeated
    desmear process. Although Continental acknowledges that
    the preferred embodiment discusses using a repeated
    desmear process, Continental argues that it is not proper
    to limit the claims to the preferred embodiment. Continen-
    tal next contends that the expert declaration cited by the
    district court, which applicants invoked to respond to in-
    definiteness and written description rejections by the ex-
    aminer, does not include a clear and unmistakable
    disavowal for prosecution disclaimer to attach. Finally,
    Continental argues that the inventor documents cited by
    the district court merely reflect the inventors practicing the
    preferred embodiment and thus lend no support for the dis-
    trict court’s construction.
    Intel responds that it was proper for the district court
    to limit the claims to a repeated desmear process because
    the patentees repeatedly disparaged and disavowed the
    single-pass desmear process and expressly defined “the
    present invention” as requiring a repeated desmear
    3   We note that the specification discusses use of a
    “double desmear process” while the district court construed
    the claims to require a “repeated desmear process.” Com-
    pare generally ’582 patent, with Claim Construction Order,
    
    2017 WL 3478659
    , at *2–3 (emphasis added). The parties
    do not argue this difference is material, and because we ul-
    timately do not agree with the district court that the claim
    limitation should have been read into the claims, the dif-
    ference in wording does not impact the outcome. Thus, for
    purposes of this opinion, we assume the terms are inter-
    changeable.
    10           CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    process. Intel also argues that the prosecution history fur-
    ther supports reading in this limitation because the expert
    declaration submitted during prosecution reiterated that
    “the claimed invention is directed to surface roughening
    performed by ‘two separate’ passes of a desmear process.”
    Appellee’s Br. 29. Furthermore, Intel contends that docu-
    ments authored by the inventors demonstrate an inability
    to obtain the desired levels of roughening using a single-
    pass desmear process, which confirms that their alleged in-
    vention was limited to a repeated desmear process.
    We agree with Continental that the district court erred
    in limiting the claims to require a repeated desmear pro-
    cess. In construing claims, district courts give claims their
    ordinary and customary meaning, which is “the meaning
    that the term would have to a person of ordinary skill in
    the art in question at the time of the invention.” Phillips
    v. AWH Corp., 
    415 F.3d 1303
    , 1312–13 (Fed. Cir. 2005) (en
    banc). “[B]ecause patentees frequently use terms idiosyn-
    cratically, the court looks to” sources including “the words
    of the claims themselves, the remainder of the specifica-
    tion, the prosecution history, and extrinsic evidence con-
    cerning relevant scientific principles, the meaning of
    technical terms, and the state of the art.” 
    Id. at 1314
    (quot-
    ing Innova/Pure Water, Inc. v. Safari Water Filtration
    Sys., Inc., 
    381 F.3d 1111
    , 1116 (Fed. Cir. 2004)).
    From this list of sources, “the claims themselves pro-
    vide substantial guidance as to the meaning of particular
    claim terms.” 
    Id. However, the
    claims “do not stand
    alone.” 
    Id. at 1315.
    They are part of “‘a fully integrated
    written instrument,’ consisting principally of a specifica-
    tion that concludes with the claims,” and must therefore
    “be read in view of the specification.” 
    Id. (quoting Mark-
    man v. Westview Instruments, Inc., 
    52 F.3d 967
    , 978–79
    (Fed. Cir. 1995)). Accordingly, the specification “is always
    highly relevant to the claim construction analysis. Usu-
    ally, it is dispositive; it is the single best guide to the
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION              11
    meaning of a disputed term.” 
    Id. (quoting Vitronics
    Corp.
    v. Conceptronic, Inc., 
    90 F.3d 1576
    , 1582 (Fed. Cir. 1996)).
    “In addition to consulting the specification, we have
    held that a court ‘should also consider the patent’s prose-
    cution history, if it is in evidence.’” 
    Id. at 1317
    (quoting
    
    Markman, 52 F.3d at 980
    ). “Like the specification, the
    prosecution history provides evidence of how the [United
    States Patent and Trademark Office (“PTO”)] and the in-
    ventor understood the patent.” 
    Id. We have
    cautioned,
    however, that “because the prosecution history represents
    an ongoing negotiation between the PTO and the applicant,
    rather than the final product of that negotiation, it often
    lacks the clarity of the specification and thus is less useful
    for claim construction purposes.” 
    Id. With these
    principles in mind, we turn to the construc-
    tion of the Category 1 Terms. Beginning with the claim
    language, we first note that none of the asserted claims ac-
    tually recite a “repeated desmear process.” Accord Claim
    Construction Order, 
    2017 WL 3478659
    , at *2. Thus, at
    least based on the plain language, the claims are not lim-
    ited to a repeated desmear process.
    We continue our analysis by reading the claims “in
    view of the specification, of which they are a part.” Phil-
    
    lips, 415 F.3d at 1315
    (quoting 
    Markman, 52 F.3d at 979
    ).
    Our case law has recognized that “the specification may re-
    veal a special definition given to a claim term by the pa-
    tentee that differs from the meaning it would otherwise
    possess.” 
    Id. at 1316.
    When the patentee acts as its own
    lexicographer, that definition governs. See 
    id. “To act
    as
    its own lexicographer, a patentee must ‘clearly set forth a
    definition of the disputed claim term’ other than its plain
    and ordinary meaning.” Thorner v. Sony Comput. Entm’t
    Am. LLC, 
    669 F.3d 1362
    , 1365 (Fed. Cir. 2012) (quoting
    CCS Fitness, Inc. v. Brunswick Corp., 
    288 F.3d 1359
    , 1366
    (Fed. Cir. 2002)). We have also found instances where “the
    specification may reveal an intentional disclaimer, or
    12           CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    disavowal, of claim scope.” 
    Phillips, 415 F.3d at 1316
    . In
    those situations, it is again the inventor’s disavowal that is
    dispositive of the claim construction. See 
    id. “To disavow
    claim scope, the specification must contain ‘expressions of
    manifest exclusion or restriction, representing a clear dis-
    avowal of claim scope.’” Retractable Techs., Inc. v. Becton,
    Dickinson & Co., 
    653 F.3d 1296
    , 1306 (Fed. Cir. 2011)
    (quoting Epistar Corp. v. Int’l Trade Comm’n, 
    566 F.3d 1321
    , 1335 (Fed. Cir. 2009)).
    We acknowledge the difficulty in drawing the “fine line
    between construing the claims in light of the specification
    and improperly importing a limitation from the specifica-
    tion into the claims.” 
    Id. at 1305.
    To avoid improperly im-
    porting limitations into the claims, “it is important to keep
    in mind that the purposes of the specification are to teach
    and enable those of skill in the art to make and use the
    invention and to provide a best mode for doing so.” Phil-
    
    lips, 415 F.3d at 1323
    .
    Based on our review of the specification, none of the
    statements relied upon by the district court rises to the
    level of “a clear and unmistakable disclaimer.” 
    Thorner, 669 F.3d at 1367
    . The specification begins by explaining
    that the invention is an “electrical device” with teeth. See
    ’582 patent col. 1 ll. 13–15, col. 1 l. 50–col. 2 l. 6. The spec-
    ification then explains that “[o]ne technique for forming the
    teeth,” which is “contrary to all known teachings in the
    prior art” is the double desmear process. See 
    id. col. 5
    ll.
    40–44 (emphasis added). Additionally, the disclosures pro-
    vide that “the present invention can be carried out by a new
    use” of a dielectric material called Probelec XB 7081. See
    
    id. col. 6
    ll. 41–48 (emphasis added). And within this con-
    text, “[f]or example, the present invention differs from the
    common desmear process in that sub-steps in the desmear
    process are repeated as a way of forming the teeth.” 
    Id. col. 8
    ll. 49–52 (emphases added). This, the patent explains, is
    “[i]n stark contrast with the etch and swell process of the
    known prior art.” 
    Id. col. 9
    ll. 1–2. The specification also
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION              13
    notes that the peel strength produced by the new use of
    Probelec XB 7081 is greater than that of “the prior art, i.e.,
    a single pass desmear process.” See 
    id. col. 7
    ll. 3–9.
    Overall, those statements simply describe how to make
    the claimed invention using the preferred Probelec XB
    7081 in a “new” way that is different from the prior art pro-
    cess and are not statements clearly limiting the claimed
    “electrical device” to require a repeated desmear process.
    Heeding the warning in Phillips to keep in mind that a goal
    of the specification is to provide a best mode to make and
    use an invention, phrases such as “one technique,” “can be
    carried out,” and “a way” indicate that using Probelec XB
    7081 is only one method for making the invention and does
    not automatically lead to finding a clear disavowal of claim
    scope. See Phil
    lips, 415 F.3d at 1323
    . We have also “ex-
    pressly rejected the contention that if a patent describes
    only a single embodiment, the claims of the patent must be
    construed as being limited to that embodiment.” Id.; see
    also Liebel-Flarsheim Co. v. Medrad, Inc., 
    358 F.3d 898
    ,
    906 (Fed. Cir. 2004) (“Even when the specification de-
    scribes only a single embodiment, the claims of the patent
    will not be read restrictively unless the patentee has
    demonstrated a clear intention to limit the claim scope us-
    ing ‘words or expressions of manifest exclusion or re-
    striction.’” (quoting Teleflex, Inc. v. Ficosa N. Am. Corp.,
    
    299 F.3d 1313
    , 1327 (Fed. Cir. 2002))). Therefore, we con-
    clude that disclosing only the Probelec XB 7081 embodi-
    ment, without more, does not result in a clear disavowal of
    claim scope.
    Additionally, distinguishing the double desmear pro-
    cess as “contrary to” or “in stark contrast” with the single
    desmear process, which again appears within the context
    of disclosures of the preferred embodiment, are not clear
    and unmistakable limiting statements. We have held that
    “[m]ere criticism of a particular embodiment . . . is not suf-
    ficient to rise to the level of clear disavowal.” 
    Thorner, 669 F.3d at 1366
    . Thus, comparing and contrasting the present
    14            CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    technique to that of the prior art does not “rise to the level
    of [a] clear disavowal” of claim scope. 
    Id. Similarly, the
    descriptions of “the present invention,”
    which also appear within the discussion of the preferred
    embodiment, are not limiting here. While descriptions “of
    the ‘present invention’ as a whole” could limit the scope of
    the invention, see Verizon Servs. Corp. v. Vonage Holdings
    Corp., 
    503 F.3d 1295
    , 1308 (Fed. Cir. 2007), “use of the
    phrase ‘present invention’ or ‘this invention’ is not always
    so limiting, such as where the references . . . are not uni-
    form, or where other portions of the intrinsic evidence do
    not support applying the limitation to the entire patent,”
    Absolute Software, Inc. v. Stealth Signal, Inc., 
    659 F.3d 1121
    , 1136–37 (Fed. Cir. 2011). In this case, the state-
    ments that “the present invention can be carried out by a
    new use” of a dielectric material called Probelec XB 7081,
    see ’582 patent col. 6 ll. 41–48 (emphasis added), and “the
    present invention differs from the common desmear process
    in that sub-steps in the desmear process are repeated as a
    way of forming the teeth,” 
    id. col. 8
    ll. 49–52 (emphases
    added), do not characterize the present invention “as a
    whole,” 
    Verizon, 503 F.3d at 1308
    . Instead, they disclose
    one way to carry out the present invention using Probelec
    XB 7081, and references to “the present invention” occur
    within this context.
    Moreover, the use of “the present invention” through-
    out the specification does not uniformly require use of a re-
    peated desmear process. See Absolute 
    Software, 659 F.3d at 1136
    –37. In certain portions of the specification, such
    as the summary, the invention is described with respect to
    its “unique surface structure,” ’582 patent col. 1 l. 52, with-
    out any requirement that the invention must encompass
    the repeated desmear process. In fact, “desmear” does not
    appear in the summary of the invention section at all. See
    
    id. col. 1
    l. 48–col. 2 l. 29. In light of this, it is difficult to
    say that the present invention “as a whole,” 
    Verizon, 503 F.3d at 1308
    , necessarily includes the repeated desmear
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION             15
    process. Thus, absent “clear and unmistakable” language
    suggesting otherwise, we conclude that the aforementioned
    statements do not meet the “exacting” standard required to
    limit the scope of the claims to a repeated desmear process.
    See 
    Thorner, 669 F.3d at 1366
    –67.
    The district court also found that the prosecution his-
    tory further supported its claim construction. Similar to
    disclaimers in the specification, “[t]o operate as a dis-
    claimer, the statement in the prosecution history must be
    clear and unambiguous, and constitute a clear disavowal of
    scope.” 
    Verizon, 503 F.3d at 1306
    . We do not agree that
    such a clear disavowal exists in this prosecution history.
    The expert declaration cited by the district court, which the
    applicants relied on to respond to both the indefiniteness
    and the written description rejections, explained that the
    written description disclosed “a technique which forms the
    teeth” by “performing two separate swell and etch steps.”
    J.A. 2074 ¶ 7 (citing ’582 patent col. 9 ll. 1–9) (emphasis
    added). The district court found this statement “clearly de-
    scribe[d] the patented method as involving two etching pro-
    cesses.” See Claim Construction Order, 
    2017 WL 3478659
    ,
    at *6. But clearly describing a particular claim term to
    overcome an indefiniteness or written description rejection
    is not the same as clearly disavowing claim scope. Moreo-
    ver, the statements in the expert declaration merely ex-
    plain one technique for forming teeth and do not amount to
    clear statements of disavowal. We therefore conclude that
    the cited statements in the prosecution history do not
    clearly and unmistakably disavow any claim scope.
    Before we conclude our analysis of the intrinsic evi-
    dence, we note that in order to read a process limitation
    into a product claim, it must meet one more criterion. Gen-
    erally, “[a] novel product that meets the criteria of patent-
    ability is not limited to the process by which it was made.”
    Vanguard Prods. Corp. v. Parker Hannifin Corp., 
    234 F.3d 1370
    , 1372–73 (Fed. Cir. 2000). “However, process steps
    can be treated as part of a product claim if the patentee has
    16           CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION
    made clear that the process steps are an essential part of
    the claimed invention.” Andersen Corp. v. Fiber Compo-
    sites, LLC, 
    474 F.3d 1361
    , 1375 (Fed. Cir. 2007). For the
    same reasons that the statements relied upon by the dis-
    trict court do not show that the patentee clearly and un-
    mistakably disavowed claim scope, they also do not make
    clear that the repeated desmear process is “an essential
    part” of the claimed electrical device having a tooth struc-
    ture. 
    Id. Far from
    being essential, the statements from the
    intrinsic evidence merely indicate a preference for using
    Probelec XB 7081 and include comparisons with the prior
    art techniques. Because the patentee has not “made clear”
    that the repeated desmear process is “an essential part of
    the claimed invention,” 
    id., it was
    improper for the district
    court to read this process limitation into the product claims
    for this additional reason.
    Finally, secondary to the intrinsic evidence, “we have
    also authorized district courts to rely on extrinsic evidence,
    which ‘consists of all evidence external to the patent and
    prosecution history, including expert and inventor testi-
    mony, dictionaries, and learned treatises.’” 
    Phillips, 415 F.3d at 1317
    (quoting 
    Markman, 52 F.3d at 980
    ). But
    “while extrinsic evidence ‘can shed useful light on the rele-
    vant art,’” 
    id. (quoting C.R.
    Bard, Inc. v. U.S. Surgical
    Corp., 
    388 F.3d 858
    , 862 (Fed. Cir. 2004)), it is “less signif-
    icant than the intrinsic record in determining the ‘legally
    operative meaning of disputed claim language,’” C.R. 
    Bard, 388 F.3d at 862
    (quoting Vanderlande Indus. Nederland
    BV v. Int’l Trade Comm’n, 
    366 F.3d 1311
    , 1318 (Fed. Cir.
    2004)); see also 
    Phillips, 415 F.3d at 1317
    . Generally, we
    have viewed extrinsic evidence as “less reliable” than in-
    trinsic evidence. 
    Phillips, 415 F.3d at 1318
    .
    Here, the district court acknowledged that the extrinsic
    evidence, which consisted of documents authored by the in-
    ventors, was “not reliable enough to be dispositive,” but
    “provide[d] helpful corroboration.” See Claim Construction
    Order, 
    2017 WL 3478659
    , at * 6. The inventor documents
    CONTINENTAL CIRCUITS LLC v. INTEL CORPORATION             17
    state that the inventors used “two passes through
    desmear,” J.A. 3321, and a “double pass desmear” J.A.
    3324, to achieve the tooth structure. However, similar to
    the intrinsic evidence, those statements reflect use of the
    preferred embodiment but give the public no indication
    that they have any limiting effect. Because we have al-
    ready determined that the intrinsic evidence does not sup-
    port reading a repeated desmear process into the claims,
    the “less reliable” extrinsic evidence, 
    Phillips, 415 F.3d at 1318
    , which even the district court acknowledged was “not
    reliable enough to be dispositive,” see Claim Construction
    Order, 
    2017 WL 3478659
    , at * 6, does not counsel other-
    wise. Accordingly, we conclude that the Category 1 Terms
    should not be limited to requiring a repeated desmear pro-
    cess and should be given their plain and ordinary meaning.
    CONCLUSION
    For the foregoing reasons, we conclude that the district
    court erred in reading a “repeated desmear process” limi-
    tation into the Category 1 Terms. Because the parties stip-
    ulated to noninfringement based on the court’s erroneous
    construction, we vacate the judgment of noninfringement
    and remand for further proceedings.
    VACATED AND REMANDED