Trials@uspto.gov
`571.272.7822
`
`Paper 8
`Entered: November 9, 2016
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`____________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`____________
`
`NANYA TECHNOLOGY CORP.,
`Petitioner,
`
`v.
`
`NORTH STAR INNOVATIONS INC.,
`Patent Owner.
`____________
`
`Case IPR2016-00965
`Patent 6,372,638 B1
`____________
`
`
`
`
`
`Before J. JOHN LEE, CHARLES J. BOUDREAU, and
`MICHELLE N. WORMMEESTER, Administrative Patent Judges.
`
`WORMMEESTER, Administrative Patent Judge.
`
`DECISION
`Institution of Inter Partes Review
`37 C.F.R. § 42.108
`
`
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`IPR2016-00965
`Patent 6,372,638 B1
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`Nanya Technology Corp. (“Petitioner”) filed a Petition (Paper 1,
`“Pet.”) requesting inter partes review of claims 1–11 of U.S. Patent No.
`6,372,638 B1 (Ex. 1001, “the ’638 patent”). North Star Innovations Inc.
`(“Patent Owner”) did not file a Preliminary Response. We have jurisdiction
`under 35 U.S.C. § 314 and 37 C.F.R. 42.4(a). Under 35 U.S.C. § 314(a), an
`inter partes review may not be instituted “unless . . . there is a reasonable
`likelihood that the petitioner would prevail with respect to at least 1 of the
`claims challenged in the petition.” For the reasons that follow, we institute
`an inter partes review as to claims 1–11 of the ’638 patent.
`
`
`I. BACKGROUND
`A. Related Proceedings
`The parties identify the following related case: North Star Innovations
`Inc. v. Nanya Technology Corp., Case No. 1:15-cv-01027-GMS (D. Del.
`Nov. 5, 2015). Pet. v; Paper 7, 2.
`Patent Owner also identifies the following related request for inter
`partes review: IPR2016-01022. Paper 7, 2.
`
`
`B. The ’638 Patent
`The ’638 patent is titled “Method for Forming a Conductive Plug
`Between Conductive Layers of an Integrated Circuit.” Ex. 1001, at [54].
`According to the ’638 patent, tungsten deposition in the integrated circuit
`industry has become highly nonconformal, resulting in the problem of
`inconsistent step coverage. Id. at 1:30–32. To illustrate this problem,
`Figures 1 and 2 of the ’638 patent are reproduced below.
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`Figures 1 and 2 show, in cross-sectional diagrams, a method for forming a
`contact structure. Id. at 2:16–18. The top surfaces of dielectric layer 16
`accumulate tungsten material 20a at a much faster rate than the bottom
`corners of contact opening 18. Id. at 1:46–48, Fig. 1. Due to this
`nonconformal deposition, the contacts end up with keyholes or voids 22. Id.
`at 1:59–61, Fig. 2.
`To address this problem, the ’638 patent proposes a method for
`forming tungsten plug contacts that are free of keyholes or voids. Id. at
`2:28–29. According to one embodiment of the ’638 patent, the method
`alters the contact profile, tapering the sidewalls of the contact to form a “golf
`tee” profile. Id. at 2:37–39. Figures 5 and 6 of the ’638 patent, which
`illustrate such a profile, are reproduced below.
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`Figures 5 and 6 show, in cross-sectional diagrams, a method for forming a
`contact structure without keyholes or voids. Id. at 2:19–21. The method
`tapers the upper portions of contact openings 55a–55c. Id. at 4:9–12. This
`tapering step enlarges the upper portions of contacts 55a–55c to radius Y,
`which is greater than radius X. Id. at 4:20–24. Radius X of Figure 5 and
`radius X of Figure 1 are the same. Id. at 4:24–25. As a result of the golf tee
`profiles, keyholes and voids within the contact openings are reduced or
`eliminated. Id. at 5:25–30.
`
`
`C. Illustrative Claim
`Petitioner challenges claims 1–11 of the ’638 patent. Claims 1, 8, and
`11 are independent. Claim 1 is illustrative of the claims under challenge:
`1. A method for forming a contact structure, the method
`comprising the steps of:
`forming a first conductive material overlying a semiconductor
`substrate;
`forming a dielectric layer overlying the first conductive layer;
`forming a resist layer over the dielectric layer;
`patterning the resist layer to form an opening that exposes
`portions of the dielectric layer;
`placing the semiconductor substrate into a reactive ion
`etching chamber and in-situ processing the semiconductor
`substrate as follows:
`etching portions of the dielectric layer using a gas mixture
`that includes a fluorocarbon source gas to form an
`opening in the dielectric layer, the opening having a
`bottom portion and a sidewall portion;
`etching a portion of the resist layer using a gas mixture that
`includes a fluorocarbon source gas and an oxygen
`source gas to remove the portion of the resist layer and
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`expose a top surface portion of the dielectric layer
`adjacent the sidewall portion;
`etching the top surface portion of the dielectric layer
`adjacent the sidewall portion to form a taper that
`extends between a top surface of the dielectric layer
`and the sidewall portion, wherein the taper towards the
`top surface portion has a radius Y and the taper towards
`the sidewall portion has a radius X wherein X<Y; and
`removing remaining portions of the resist layer;
`depositing a second conductive material within the opening;
`and
`polishing away a top portion of the conductive material and a
`top portion of the dielectric layer to remove the taper.
`
`
`
`D. Asserted Grounds of Unpatentability
`Petitioner challenges claims 1–11 of the ’638 patent on the following
`grounds. Pet. 2, 34–84.
`Reference(s)
`Mathews1
`Mathews
`Mathews and Langley2
`Mathews, Langley, and Wuu3
`
`Basis
`§ 102
`§ 103
`§ 103
`§ 103
`
`Claim(s) Challenged
`8–11
`8–11
`1–7 and 11
`1–74
`
`
`1 Mathews, U.S. Patent No. 5,580,821, issued Dec. 3, 1996 (Ex. 1004).
`2 Langley, U.S. Patent No. 4,939,105, issued July 3, 1990 (Ex. 1005).
`3 Wuu, U.S. Patent No. 5,547,892, issued Aug. 20, 1996 (Ex. 1006).
`4 For the ground based on Mathews, Langley, and Wuu, Petitioner identifies
`claims 1–7 and 11 in its summary of the asserted grounds on page 2 of the
`Petition, but omits claim 11 from the heading on page 78 of the Petition.
`Given the substance of Petitioner’s arguments, we presume the former to be
`a typographical error, and, therefore, we address only claims 1–7 with
`respect to this ground.
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`As additional support, Petitioner proffers the Declaration of Dr. Martin G.
`Walker (Ex. 1003). See id.
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`
`E. Claim Interpretation
`We construe claims in an unexpired patent by applying the broadest
`reasonable interpretation in light of the specification of the patent in which
`they appear. See 37 C.F.R. § 42.100(b); Cuozzo Speed Techs. LLC v. Lee,
`136 S. Ct. 2131, 2144–46 (2016) (upholding the use of the broadest
`reasonable interpretation standard). Under this standard, claim terms are
`generally given their ordinary and customary meaning, as would be
`understood by one of ordinary skill in the art in the context of the entire
`disclosure. See In re Translogic Tech., Inc., 504 F.3d 1249, 1257 (Fed. Cir.
`2007). A “claim term will not receive its ordinary meaning if the patentee
`acted as his own lexicographer,” however, and clearly set forth a definition
`of the claim term in the specification. CCS Fitness, Inc. v. Brunswick Corp.,
`288 F.3d 1359, 1366 (Fed. Cir. 2002).
`Petitioner provides proposed interpretations for various limitations of
`the claims. See Pet. 10–22. For purposes of this Decision, we conclude that
`no term requires interpretation at this time to resolve any controversy in this
`proceeding. See Vivid Techs., Inc. v. Am. Sci. & Eng’g, Inc., 200 F.3d 795,
`803 (Fed. Cir. 1999) (“only those terms need be construed that are in
`controversy, and only to the extent necessary to resolve the controversy”).
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`II. DISCUSSION
`A. Anticipation by Mathews
`Petitioner argues that Mathews anticipates claims 8–11 of the ’638
`patent under 35 U.S.C. § 102. Pet. 2, 34–51. For the reasons explained
`below, we are persuaded that Petitioner has demonstrated a reasonable
`likelihood of prevailing on its asserted ground as to claims 8–10, but not as
`to claim 11.
`
`
`1. Mathews
`Mathews describes a method of forming an electrically conductive
`contact plug. Ex. 1004, 1:7–9. Figure 5 of Mathews is reproduced below.
`
`
`
`Figure 5 shows a wafer during a processing step, namely a facet sputter
`etching step. Id. at 2:34–35, 3:40–41. This step provides contact opening 44
`with outwardly angled sidewalls 48 that effectively widen the contact
`opening at its outermost region 46. Id. at 3:40–43. As a result, undesired
`keyholes or voids that typically form when depositing a conductive material
`within the contact can be avoided. See id. at 1:44–45; 2:7–9.
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`2. Claims 8–10
`Petitioner explains in its Petition how Mathews discloses all the
`elements of independent claim 8. See Pet. 34–45. For example, Petitioner
`directs us to Figures 4, 5, 7, and 8 of Mathews, which are reproduced below.
`Id. at 35, 37–38, 40, 42–44.
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`Figures 4, 5, 7, and 8 show a wafer during various processing steps.
`Ex. 1004, 2:30–41. Petitioner identifies Mathews’ electrically insulative
`material 40 as a “dielectric layer” and Mathews’ photoresist 42 as a “resist
`layer,” which is formed over insulative material 40. Pet. 35–36; Ex. 1004,
`Fig. 4.
`Petitioner points out that Figure 4 illustrates the step of etching
`insulative material 40 to form contact opening 44, which Petitioner identifies
`as an “opening.” Pet. 36. Petitioner argues that such etching is anisotropic
`because it is carried out in the vertical direction only. Id. at 37. Referring to
`an annotated version of Figure 4 of Mathews, which is reproduced below,
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`Petitioner further argues that contact opening 44 includes a “top portion,” “a
`bottom portion,” and a “sidewall portion,” as recited in claim 8. Id. at 38.
`
`
`As discussed above, Figure 4 shows a wafer during a processing step.
`Petitioner also points out that Figures 4 and 5 illustrate the step of
`removing photoresist 42 after contact opening 44 is formed. Id. at 39 (citing
`Ex. 1004, 3:39–40). Petitioner points out that Figure 5 further illustrates the
`step of facet sputter etching after removing the photoresist in order to
`provide contact opening 44 with outwardly angled sidewalls 48. Id. at 40–
`41 (citing Ex. 1004, 3:39–43). Petitioner identifies this latter step as
`“tapering the top portion of the opening.” Id. Petitioner further argues that
`sputter etching is anisotropic because it is highly directional. Id. at 41.
`Petitioner additionally points out that Figure 7 illustrates the step of
`depositing conductive materials 52 and 54 over the top surface of insulative
`material 40 as well as within contact opening 44. Id. at 42.
`Finally, Petitioner points out that Figure 8 illustrates the step of
`removing the conductive and insulative materials “down to the point where
`the outwardly angled sidewalls (48) meet the vertical sidewalls (50).” Id. at
`44. As Petitioner asserts, Mathews uses chemical-mechanical polishing for
`this step. Id.; Ex. 1004, 4:33–34.
`Based on the record before us, at this stage of the proceeding, we
`determine that Petitioner has demonstrated a reasonable likelihood of
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`prevailing on its assertion that Mathews anticipates claim 8. Having
`reviewed Petitioner’s arguments asserting that Mathews anticipates
`dependent claims 9 and 10 (see Pet. 45–46), we also determine that
`Petitioner has demonstrated a reasonable likelihood of prevailing on its
`assertion as to these claims on the basis of Petitioner’s contentions.
`
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`3. Claim 11
`Claim 11 recites the step of “tapering the top portion of the opening
`using an anisotropic etch process while removing the resist layer” (emphasis
`added). For this limitation, Petitioner directs us to where Mathews describes
`the step of facet sputter etching, which Petitioner identifies as a “tapering”
`step. Pet. 48–49. Mathews discloses first using an oxygen etch to “move
`the resist back away from the contact, and not to necessarily fully strip the
`resist,” and then using an argon etch “to produce the desired facet.”
`Ex. 1004, 3:46–55. Given this disclosure, Petitioner contends that
`photoresist remains after moving the resist back away from the contact. Pet.
`48. Petitioner further contends that “sputter etching will remove any
`material the sputter ions collide with, including the remaining photoresist
`layer,” because such etching is a non-selective physical process. Id. at 50.
`That is, according to Petitioner, “the (facet) sputter etching necessarily
`removes the photoresist layer as well as the exposed dielectric layer while
`the taper is being formed.” Id. Thus, Petitioner contends this limitation is
`disclosed inherently.
`Petitioner’s contentions are not persuasive. As Petitioner
`acknowledges in its discussion of claim 8, Mathews’ “photoresist layer (42)
`is partially or completely removed before creating the outwardly angled
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`sidewalls.” Id. at 40. Moreover, in the case of partial removal, Mathews
`does not specify how far back away from the contact to move the
`photoresist. Nor does Petitioner proffer persuasive evidence showing how
`far back away to move the photoresist. Based on the record before us, we
`are not persuaded that Mathews’ disclosure of partially or completely
`removing photoresist before creating outwardly angled sidewalls necessarily
`discloses the recited tapering step while removing the resist layer. See
`Continental Can Co. USA v. Monsanto Co., 948 F.2d 1264, 1269 (Fed. Cir.
`1991) (“Inherency, however, may not be established by probabilities or
`possibilities. The mere fact that a certain thing may result from a given set
`of circumstances is not sufficient.”).
`In view of the foregoing, we determine that Petitioner has not
`demonstrated a reasonable likelihood of prevailing on its assertion that
`Mathews anticipates claim 11.
`
`
`B. Obviousness over Mathews
`Petitioner argues that claims 8–11 of the ’638 patent would have been
`obvious over Mathews under 35 U.S.C. § 103. Pet. 2, 51–53. For the
`reasons explained below, we are persuaded that Petitioner has demonstrated
`a reasonable likelihood of prevailing on this asserted ground as to claim 11,
`but not as to claims 8–10.
`
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`1. Claims 8–10
`As discussed above, Petitioner argues that Mathews anticipates claims
`8–10. Petitioner alternatively argues that, to the extent that we are not
`persuaded by its anticipation arguments, “Mathews nevertheless renders
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`Claims 8–10 obvious because they would have been obvious to a skilled
`artisan in light of Mathews.” Pet. 51. Petitioner relies on Dr. Walker’s
`declaration testimony to support its contention. Id. (citing Ex. 1003 ¶¶ 113–
`115). In his declaration, Dr. Walker only testifies conclusorily that claims
`8–10 would have been obvious for the same reasons Mathews anticipates
`those claims. Ex. 1003 ¶¶ 90–104, 113–115. Neither Petitioner nor Dr.
`Walker provides further explanation as to how claims 8–10 would have been
`obvious over Mathews if they are not anticipated. Under 35 U.S.C.
`§ 312(a)(3), a petition must identify, “with particularity, each claim
`challenged, the grounds on which the challenge to each claim is based, and
`the evidence that supports the grounds for the challenge to each claim.” Our
`rules further require that a petition must identify “[h]ow the construed claim
`is unpatentable under the statutory grounds identified” and “where each
`element of the claim is found in the prior art,” and must explain the
`“relevance of the evidence to the challenge raised. 37 C.F.R. § 42.104(b);
`see also 37 C.F.R. § 42.22(a)(2) (requiring a petition to include a “full
`statement of the reasons for the relief requested, including a detailed
`explanation of the significance of the evidence”). The Petition fails to meet
`these requirements sufficiently for this asserted ground of unpatentability.
`As Petitioner does not explain sufficiently how any of claims 8–10 would
`have been obvious in light of Mathews, we determine that Petitioner has not
`demonstrated a reasonable likelihood of prevailing on its assertion that
`claims 8–10 would have been obvious over Mathews if we ultimately
`determine those claims are not anticipated.
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`2. Claim 11
`As discussed above, claim 11 recites the step of “tapering the top
`portion of the opening using an anisotropic etch process while removing the
`resist layer” (emphasis added). For this limitation, Petitioner directs us to
`where Mathews teaches complete or partial removal of photoresist (i.e.,
`“resist layer”) before5 facet sputter etching (i.e., “tapering”). Pet. 52 (citing
`Ex. 1004, 3:44–50). Petitioner explains that sputter etching is a nonselective
`process, which would remove any remaining photoresist. Id. Petitioner also
`explains that, “[if] the photoresist were completely removed prior to the
`facet etch, it would take longer to obtain the same amount of tapering since
`the flat portions of the dielectric would be receding at the same time the
`edges are being tapered.” Id.; see also id. at 52–53 (stating that “exposing
`the edges would permit the tapering of the via faster since the flat portions of
`the dielectric are not etched until the remaining photoresist is removed
`completely”). Thus, Petitioner contends, “it would have been obvious for a
`person of ordinary skill in the art to not remove the photoresist layer
`completely prior to the sputter etching process, and instead retain portions of
`the photoresist layer and remove them simultaneously during the facet
`sputter etching step.” Id. at 53. Petitioner relies on Dr. Walker’s declaration
`
`
`5 In arguing that claim 11 would have been obvious over Mathews,
`Petitioner asserts that Mathews discloses “complete or partial removal of the
`photoresist during the tapering etch.” Pet. 52 (emphasis added). In arguing
`that Mathews anticipates claim 8, however, Petitioner asserts that Mathews’
`“photoresist layer (42) is partially or completely removed before creating the
`outwardly angled sidewalls.” Id. at 40 (emphasis added). Given the cited
`disclosures in Mathews (see Ex. 1004, 3:38–60), as well as the substance of
`Petitioner’s arguments, we presume the former to be a typographical error.
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`testimony to support its contention. Id. at 52–53 (citing Ex. 1003 ¶¶ 120–
`121).
`
`Based on the record before us, at this stage of the proceeding, we are
`persuaded by Petitioner’s proffered reasoning for partially removing the
`photoresist in Mathews in order to carry out the facet sputter etching while
`removing remaining portions of the photoresist. See In re Kahn, 441 F.3d
`977, 988 (Fed. Cir. 2006) (“[T]here must be some articulated reasoning with
`some rational underpinning to support the legal conclusion of
`obviousness.”). Accordingly, we determine that Petitioner has demonstrated
`a reasonable likelihood of prevailing on its assertion that claim 11 would
`have been obvious over Mathews.
`
`
`C. Obviousness over Mathews and Langley
`Petitioner argues that claims 1–7 and 11 of the ’638 patent would have
`been obvious over Mathews and Langley under 35 U.S.C. § 103. Pet. 2, 53–
`78. For the reasons explained below, we are persuaded that Petitioner has
`demonstrated a reasonable likelihood of prevailing on its asserted ground as
`to claims 1–4 and 11, but not as to claims 5–7.
`
`
`1. Langley
`Langley describes a method of contact etching. Ex. 1005, 1:6–10.
`Figures 4–7 of Langley, which illustrate the method, are reproduced below.
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`Figures 4–7 show an oxide layer with an overlying mask during various
`etching steps. Id. at 2:60–68. The mask is a layer of resist 14, which is
`patterned for contacts 15 and 15′. Id. at 3:9–10, Fig. 4. The first step
`involves forming slopes in the contacts by eroding resist 14. Id. at 3:36–38,
`Fig. 5. The second step involves etching oxides 12, 13 as well as remaining
`resist 14. Id. at 3:48–50, Fig. 6. The contacts are essentially complete at
`this point. Id. at 3:57–58. The third step involves etching most of the
`remaining oxide out of the contacts. Id. at 3:62–65. The final step involves
`etching the rest of the oxide out of contacts 15′ down to substrate 10. Id. at
`4:9–12, Fig. 7. The contacts are well sloped at their tops, and deeper
`contacts 15′ have vertical walls. Id. at 4:21–24.
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`2. Claims 1–4
`For claim 1, Petitioner relies primarily on Mathews. See Pet. 56–74.
`For example, claim 1 recites “forming a first conductive material overlying a
`semiconductor substrate.” As to this limitation, Petitioner directs us to
`Figure 4 of Mathews, which is reproduced below. Id. at 57.
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`Figure 4 shows a wafer during a processing step. Ex. 1004, 2:30–32.
`Petitioner identifies Mathews’ active area 38 as a “first conductive material”
`and Mathews’ bulk substrate 36 as a “semiconductor substrate.” Pet. 58.
`Petitioner argues that active area 38 overlies bulk substrate 36, even though
`Figure 4 shows active area 38 being formed within the top surface of bulk
`substrate 36. Id. at 57. In support of this argument, Petitioner points out that
`claim 7, which depends from claim 1, recites “forming the first conductive
`layer as a doped current electrode for a transistor within a substrate.” Id. at
`58. Given the dependency of claim 7 from claim 1, Petitioner explains that
`the term “overlying a semiconductor substrate” in claim 1 encompasses the
`term “within a substrate” in claim 7. Id. On this record, we are persuaded
`that Mathews teaches the recited “forming” limitation for the reasons
`outlined by Petitioner.
`Claim 1 further recites “placing the semiconductor substrate into a
`reactive ion etching chamber and in-situ processing the semiconductor
`substrate.” For this limitation, Petitioner directs us to where Mathews
`teaches that all mask removal and etching are conducted in the same
`chamber, where etching can be carried out in a reactive manner. Id. at 62–
`63 (citing Ex. 1004, 3:44–46, 3:55–57). On this record, we are persuaded
`that Mathews teaches the recited “placing” and “processing” limitations.
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`Claim 1 further recites “etching a portion of the resist layer using a
`gas mixture that includes a fluorocarbon source gas and an oxygen source
`gas to remove the portion of the resist layer and expose a top surface portion
`of the dielectric layer adjacent the sidewall portion.” For this limitation,
`Petitioner directs us to where Mathews teaches that “an oxygen etch is
`conducted to strip the resist.” Id. at 66 (citing Ex. 1004, 3:46–48). Relying
`on Dr. Walker’s declaration testimony, Petitioner further argues that “it
`would have been obvious for a skilled artisan to etch the photoresist layer
`without completely evacuating the fluorocarbon gas that was used in the
`previous step (of vertically etching the vias).” Id. (citing Ex. 1003 ¶ 148);
`see also Ex. 1004, 3:34–36 (“[a]n example etch of the BPSG oxide to form
`contact 44 would be a dry etch using a carbon/fluorine based chemistry”); id.
`at 3:39–40 (“masking layer 42 is removed after the etching which formed
`contact opening 44”). In his declaration, Dr. Walker testifies that it would
`have been simpler for a person of ordinary skill in the art to add oxygen to
`the fluorocarbon gas in the chamber than to completely evacuate the
`fluorocarbon gas. Ex. 1003 ¶ 148. Based on the record before us, we are
`persuaded that the recited “etching” step is taught by Mathews.
`Claim 1 further recites “removing remaining portions of the resist
`layer.” As to this limitation, Petitioner refers to its argument that claim 11 is
`obvious over Mathews. Pet. 70. For the reasons discussed above, we are
`persuaded that this “removing” step would have been obvious over
`Mathews.
`Petitioner also relies alternatively on Langley for certain of the
`limitations of claim 1. For example, Petitioner relies alternatively on
`Langley for the following “etching” step discussed above: “etching a
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`portion of the resist layer using a gas mixture that includes a fluorocarbon
`source gas and an oxygen source gas to remove the portion of the resist layer
`and expose a top surface portion of the dielectric layer adjacent the sidewall
`portion.” Pet. 66. In particular, Petitioner directs us to where Langley
`teaches that “a chamber atmosphere of O2, He, CHF3, and CF4 is provided,
`widening, or forming slopes in, contacts 15 and 15′ by eroding resist.” Id.
`(citing Ex. 1005, 3:36–38). Petitioner also directs us to Figure 5 of Langley,
`which is reproduced below.
`
`
`Figure 5 shows a cross-sectional view of the result of an etching step. Ex.
`1005, 2:62–63. According to Petitioner, Figure 5 specifically shows that
`“the surface of a portion of the dielectric layer (13) is exposed where the
`photoresist layer (14) is etched back.” Pet. 66–67. Based on the record
`before us, we are persuaded that Langley also teaches the recited “etching”
`step.
`
`In addition to showing that Langley teaches this “etching” step,
`Petitioner must provide “some articulated reasoning with some rational
`underpinning to support the legal conclusion of obviousness.” Kahn, 441
`F.3d at 988; see KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 418 (2007). In
`that regard, Petitioner contends that, “[b]ecause of the significant overlap in
`the process environment, it would have been a simple substitution for a
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`person practicing the invention of Mathews to use a mixture of CHF3, CF4,
`and O2 (as taught in Langley) during the photoresist removal step instead of
`using just O2 as Mathews suggests.” Pet. 68. Petitioner relies on Dr.
`Walker’s declaration testimony to support its contention. Id. at 67–68
`(citing Ex. 1003 ¶ 147 (referring to ¶ 127)). Based on the record before us,
`at this stage of the proceeding, we are persuaded that Petitioner has provided
`adequately articulated reasoning with some rational underpinning to support
`the legal conclusion of obviousness. See Kahn, 441 F.3d at 988.
`In view of the foregoing, we determine that Petitioner has
`demonstrated a reasonable likelihood of prevailing on its assertion that
`claim 1 would have been obvious over Mathews and Langley. Having
`reviewed Petitioner’s arguments asserting that dependent claims 2–4 would
`have been obvious over Mathews and Langley (see Pet. 74–76), we also
`determine that Petitioner has demonstrated a reasonable likelihood of
`prevailing on its assertion as to these claims.
`
`
`3. Claims 5–7
`Petitioner asserts that “[c]laims 5–7 are directed to applying [c]laim 1
`to various portions of an SRAM cell, that is forming a via over various
`elements of an SRAM transistor.” Pet. 77. Petitioner further argues that “it
`would have been obvious for a person of ordinary skill in the art to apply the
`inventions disclosed in Mathews and Langley to an SRAM cell.” Id.
`According to Petitioner, “[c]laims 5–7 simply recite characteristics of
`SRAM cells that were well-known at the time of the alleged invention,” and
`they “do not recite any elements that are particularly suited for or targeted at
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`SRAM cells.” Id. at 77–78. Thus, Petitioner concludes, “[c]laims 5–7 are
`obvious over Mathews in view of Langley.” Id. at 78.
`Based on the record before us, we are not persuaded that Petitioner
`has provided adequately articulated reasoning with some rational
`underpinning to support the legal conclusion of obviousness. See Kahn, 441
`F.3d at 988. Petitioner does not explain persuasively why one of ordinary
`skill in the art would have considered combining elements of Mathews with
`elements of Langley, or why one of ordinary skill in the art would have
`considered modifying the teachings of Mathews in view of the teachings of
`Langley to arrive at the claimed invention. For example, Petitioner does not
`direct us to any portion of Mathews or Langley that describes an SRAM cell.
`Moreover, contrary to Petitioner’s assertion that claims 5–7 “do not recite
`any elements that are particularly suited for or targeted at SRAM cells,” each
`of these claims expressly recites “an SRAM cell.”
`In view of the foregoing, we determine that Petitioner has not
`demonstrated a reasonable likelihood of prevailing on its assertion that
`claims 5–7 would have been obvious over Mathews and Langley.
`
`
`4. Claim 11
`As discussed above, Petitioner argues that Mathews anticipates or
`renders obvious claim 11. Petitioner further argues that, “[t]o the extent,
`however, that PTAB determines Mathews does not anticipate or render
`obvious Claim 11, it is nevertheless obvious over Mathews in view of
`Langley.” Pet. 53. Focusing on the recited step of “tapering the top portion
`of the opening . . . while removing the resist layer,” Petitioner directs us to
`Figures 4–6 of Langley, which are reproduced below. Pet. 54–55.
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`Figures 4–6 illustrate etching steps. Ex. 1005, 2:60–64. Referring to
`Figures 4 and 5, Petitioner points out that Langley teaches that “a chamber
`atmosphere of O2, He, CHF3, and CF4 is provided, widening, or forming
`slopes in, contacts 15 and 15′ by eroding resist.” Id. at 53–54 (citing Ex.
`1005, 3:36–38). Referring to Figures 5 and 6, Petitioner also points out that
`Langley further teaches that, “[a]fter the proper contact slope is obtained, a
`second etch is performed . . . in order to etch oxides 13 and 12 and
`remaining resist 14.” Id. at 54 (citing Ex. 1005, 3:48–52). Based on the
`record before us, we are persuaded that Langley teaches the recited step of
`“tapering the top portion of the opening . . . while removing the resist layer.”
`As mentioned above, Petitioner must also provide “some articulated
`reasoning with some rational underpinning to support the legal conclusion of
`obviousness.” Kahn, 441 F.3d at 988; see KSR, 550 U.S. at 418. In that
`regard, Petitioner contends that “a skilled artisan would have been motivated
`to combine the specific teachings of Langley (i.e., simultaneously etching
`the dielectric and the photoresist) with Mathews” because, “[i]n light of the
`overlap in the etch type, chemical, and environment, it would have been
`simple for a skilled artisan to substitute one or more etching steps disclosed
`in Langley for the etching steps disclosed in Mathews.” Pet. 30, 56.
`Petitioner relies on Dr. Walker’s declaration testimony to support its
`contention. Id. (citing Ex. 1003 ¶ 127). On this record, at this stage of the
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`proceeding, we are persuaded that Petitioner has provided adequately
`articulated reasoning with some rational underpinning to support the legal
`conclusion of obviousness. See Kahn, 441 F.3d at 988.
`In view of the foregoing, we determine that Petitioner has
`demonstrated a reasonable likelihood of prevailing on its assertion that claim
`11 would have been obvious over Mathews and Langley.
`
`
`D. Obviousness over Mathews, Langley, and Wuu
`Petitioner argues that claims 1–7 of the ’638 patent would have been
`obvious over Mathews, Langley, and Wuu under 35 U.S.C. § 103. Pet. 2,
`78–84. For the reasons explained below, we are persuaded that Petitioner
`has demonstrated a reasonable likelihood of prevailing on its asserted
`ground as to claims 1 and 5–7, but not as to claims 2–4.
`
`
`1. Wuu
`Wuu describes a method of fabricating a plug structure and metal
`contacts on the latch portion of a static random access memory (SRAM)
`circuit including thin film transistors. Ex. 1006, 1:9–12, 4:53–57.
`
`
`2. Claims 1 and 5–7
`Claim 1 recites “forming a first conductive material overlying a
`semiconductor substrate.” Each of claims 5–7 depends directly from claim 1
`and further limits the step of forming a first conductive layer. As discussed
`above, Petitioner argues that claims 1 and 5–7 would have been obvious
`over Mathews and Langley. For the reasons given above, we are persuaded
`by Petitioner’s argument as to claim 1, but not