TEXAS INSTRUMENTS INCORPORATED

Patent Trials and Appeals Board

Feb 18, 2022

2021002751 (P.T.A.B. Feb. 18, 2022)

UNITED STATES PATENT AND TRADEMARK OFFICE UNITED STATES DEPARTMENT OF COMMERCE United States Patent and Trademark Office Address: COMMISSIONER FOR PATENTS P.O. Box 1450 Alexandria, Virginia 22313-1450 www.uspto.gov APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO. 16/056,827 08/07/2018 Huang-Chun Wen TI-75481.1 7636 23494 7590 02/18/2022 TEXAS INSTRUMENTS INCORPORATED P O BOX 655474, MS 3999 DALLAS, TX 75265 EXAMINER GRAYBILL, DAVID E ART UNIT PAPER NUMBER 2894 NOTIFICATION DATE DELIVERY MODE 02/18/2022 ELECTRONIC Please find below and/or attached an Office communication concerning this application or proceeding. The time period for reply, if any, is set in the attached communication. Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the following e-mail address(es): uspto@ti.com PTOL-90A (Rev. 04/07) UNITED STATES PATENT AND TRADEMARK OFFICE BEFORE THE PATENT TRIAL AND APPEAL BOARD Ex parte HUANG-CHUN WEN, RICHARD ALLEN BAILEY, ANTONIO GUILLEMO ACOSTA, JOHN A. RODRIGUEZ, SCOTT ROBERT SUMMERFELT, and KEMAL TAMER SAN Appeal 2021-002751 Application 16/056,827 Technology Center 2800 Before TERRY J. OWENS, DONNA M. PRAISS, and DEBRA L. DENNETT, Administrative Patent Judges. DENNETT, Administrative Patent Judge. DECISION ON APPEAL1 Pursuant to 35 U.S.C. § 134(a), Appellant2 appeals from the Examiner’s decision to reject claims 7 and 8 of Application 16/056,827, 1 In our Decision, we refer to the Specification (“Spec.”) of Application 16/056,827 filed Aug. 7, 2018 (“the ’827 App.”); the Final Office Action dated Nov. 13, 2020 (“Final Act.”); the Appeal Brief filed Dec. 25, 2020 (“Appeal Br.”); the Examiner’s Answer dated Mar. 8, 2021 (“Ans.”), and the Reply Brief filed Mar. 21, 2021 (“Reply Br.”). 2 We use the term “Appellant” to refer to “applicant” as defined in 37 C.F.R. § 1.42. Appellant identifies Texas Instruments Incorporated as the real party in interest. Appeal Br. 3. Appeal 2021-002751 Application 16/056,827 2 which constitute all the claims pending in this application.3 See Final Act. 1. We have jurisdiction under 35 U.S.C. § 6(b). For the reasons set forth below, we AFFIRM. BACKGROUND The subject matter of the invention relates to formation of capacitors in memory devices such as ferroelectric memories. Spec. ¶ 4. Appellant explains that technology for realizing non-volatile solid-state memory devices involves the construction of capacitors in which the dielectric material is a polarizable ferroelectric material, such as lead-zirconium- titanate (PZT) or strontium-bismuth-tantalate (SBT), rather than silicon dioxide or silicon nitride as typically used in non-ferroelectric capacitors. Id. ¶ 4. In contrast to conventional metal on silicon capacitors which lose their stored charge on power-down of the device, ferroelectric capacitors have non-volatile storage of binary states. Id. According to Appellant, ferroelectric capacitors and thus memories incorporating such devices are vulnerable over time to weakening of switching polarization, commonly referred to as “aging.” Id. ¶ 11. The weakened switching polarization will appear as a loss of read margin and a corresponding increased likelihood of read errors. Id. In addition, according to Appellant, exposing ferroelectric integrated circuits to high temperatures, such as those encountered in manufacturing processes following the deposition of the ferroelectric material, will degrade the polarization characteristic of that material. Id. ¶ 12. Moreover, packaging of the 3 The Final Office Action indicates that claims 1-6 are withdrawn from consideration. Appeal 2021-002751 Application 16/056,827 3 integrated circuit can also result in mechanical stresses applied to the surface of the die, with such stresses being sufficient in some cases as to cause cracking of the protective overcoat film at the die or even displacement of metal conductors or other features so as to cause device failure. Id. ¶ 13. Appellant indicates that one approach to reducing the mechanical stresses caused by packaging is the application of a stress relief layer, such as a polyimide film, to the surface of the integrated circuit die prior to molding. Id. Conventionally, the formation of the polyimide film involves a final bake at an elevated temperature for a significant duration, such as at 375° C for one hour, to cure the material. Id. However, according to Appellant, thermal processes following the fabrication of ferroelectric capacitors tend to degrade the switching polarization characteristics of the material and, consequently, performance parameters, thus application of polyimide stress relief film in the conventional manner is discouraged for ferroelectric integrated circuits. Id. Appellant states that the invention disclosed provides a method of fabricating a ferroelectric integrated circuit in which the polarization characteristics are enhanced without requiring modification of processes involved in forming the ferroelectric structure, such that the integrated circuit can tolerate subsequent thermal processes. Id. ¶¶ 17, 18, 20. Appellant describes an approach “for curing a passivation film, such as polyimide, at the surface of a ferroelectric integrated circuit such that the intrinsic tensile stress in the cured passivation film imparts beneficial compressive stress in underlying ferroelectric material, without degrading the polarization of that ferroelectric material due to hydrogen diffusion or other time-and temperature polarization degradation mechanisms.” Id. ¶ 33. Appeal 2021-002751 Application 16/056,827 4 Claim 7, reproduced from the Claims Appendix of the Appeal Brief, illustrates the claimed subject matter: 7. A method of manufacturing an integrated circuit, comprising: forming at least one circuit element comprising a layer of a ferroelectric material near a semiconducting surface of a body; then forming at least one level of conductors overlying the element, each level comprising patterned metal conductors and a dielectric layer; forming a protective overcoat layer over the surface and overlying the at least one circuit element and the at least one level of conductors; then depositing a passivation layer of a material comprising a polymer-containing film over the protective overcoat layer; and applying electromagnetic energy to the passivation layer at a vibrational frequency of the polymer, to heat the passivation layer to a temperature between 340° C and a Curie temperature of the ferroelectric material for a duration sufficient to cure the material of the passivation layer into a tensile stress state. REFERENCES The Examiner relies on the following prior art in rejecting the claims on appeal: Name Reference Date Sashida US 2004/0046185 A1 Mar. 11, 2004 Wong et al. (“Wong”) US 2015/0056819 A1 Feb. 26, 2015 REJECTIONS Appeal 2021-002751 Application 16/056,827 5 The Examiner maintains the rejection of claims 7 and 8 as obvious under 35 U.S.C. § 103 over Sashida in view of Wong. Final Act. 3-8. DISCUSSION We review the appealed rejections for error based upon the issues identified by Appellant and in light of the arguments and evidence produced thereon. Ex parte Frye, 94 USPQ2d 1072, 1075 (BPAI 2010) (precedential), (cited with approval in In re Jung, 637 F.3d 1356, 1365 (Fed. Cir. 2011)) (“[I]t has long been the Board’s practice to require an applicant to identify the alleged error in the [E]xaminer’s rejections.”). After considering the evidence presented in this Appeal and each of Appellant’s arguments, we are not persuaded that Appellant identifies reversible error. Thus, we affirm the Examiner’s rejections for the reasons expressed in the Final Office Action and the Answer. We add the following primarily for emphasis. Appellant argues that the cited prior art references, alone or in combination, do not teach “applying electromagnetic energy to the passivation layer at a vibrational frequency of the polymer, to heat the passivation layer to a temperature between 340° C and a Curie temperature of the ferroelectric material for a duration sufficient to cure the material of the passivation layer into a tensile stress state,” as required by claim 7. Appeal Br. 7-10. The Examiner finds that the combination of Sashida and Wong teaches the limitation. Final Act. 3-6. The Examiner finds that Sashida discloses using lead zirconate titanate (“PZT”) as a ferroelectric material (Final Act. 3), which the Specification states is one of two ferroelectric materials typically used in Appeal 2021-002751 Application 16/056,827 6 construction of capacitors (Spec. ¶¶ 4, 7, 32). The Specification defines the Curie temperature of a ferroelectric material as “the temperature at which, absent an externally applied electric field, the crystal structure of the ferroelectric material undergoes a phase change that causes loss of polarization.” Spec. ¶ 42. The Specification discloses the Curie temperature of PZT to be 400° C. Id. ¶ 44. The Examiner finds, and Appellant does not dispute, that the Curie temperature of PZT is inherent to the ferroelectric material. Final Act. 4; see also generally Appeal Br.; Reply Br. The Examiner finds that Wong discloses applying electromagnetic energy in the form of variable microwave radiation to the passivation (packaging) layer. Final Act. 5. Wong discloses using variable microwave radiation to raise the temperature to that at which the packaging layer can complete the curing process. Wong ¶ 55. The Specification discloses use of electromagnetic energy in the form of variable frequency microwaves at a frequency that couples to the vibrational frequency of the polymer of the passivation film, to heat and cure the film. Spec. ¶ 44. The Examiner finds, and Appellant does not dispute, that the vibrational frequency of a polymer is an inherent property of that polymer. Final Act. 4-5; see also generally Appeal Br.; Reply Br. Wong discloses: The dipole molecules are oscillated by the microwave energy. It is this oscillation which creates the internal heat which can be used to reduce H2O and other adsorbed molecule accumulation in the porous polymer material. Wong ¶ 58. The Examiner finds that Wong discloses a packaging layer (passivation layer) may comprise a polyimide, particularly HD4100. Final Act. 5; see Wong ¶¶ 34, 78. The Specification states: Appeal 2021-002751 Application 16/056,827 7 It is known in the art that cured polyimide adheres well to the surface of an integrated circuit, and that such adhesion is important in the ability of the polyimide film to serve as a stress relief agent for the integrated circuit when packaged, for example in a molded plastic package. . . . [T]he application of a stress relief film of polyimide or other materials that require curing or anneal is strongly discouraged for integrated circuits that include ferroelectric devices, because the time and temperature required for curing the stress relief film significantly degrade the polarization characteristics of the ferroelectric material. For a specific example, the typical curing process for a polyimide stress relief film is a bake at 375° C for on the order of one hour, which is essentially fatal to the polarization characteristics of lead-zirconium-titanate (PZT) ferroelectric material. It is believed that this degradation results from the diffusion of hydrogen into the ferroelectric film, such diffusion accelerated by the time and temperature required to cure polyimide in the conventional manner. Spec. ¶ 32. The composition of this passivation film is of a material that attains a stress state when cured in the manner to be described below according to this embodiment, such that the stress state of the cured passivation film exerts a stress on the underlying ferroelectric circuit elements in the integrated circuit. An example of such a passivation film is a polyimide, such as the HD4100 polyimide product available from HD. Spec. ¶ 39. The Examiner finds that Wong discloses using variable frequency microwaves to heat the packaging layer at 300° C to 400° C for a time sufficient to cure the polymer. Final Act. 5; Wong ¶ 55. The Examiner finds that Wong discloses examples in which a polyimide layer is fully cured using variable frequency microwaves at a temperature of 340° C for a duration of 8 minutes. Final Act. 5; Wong ¶ 82. Appeal 2021-002751 Application 16/056,827 8 The Examiner finds that when the passivation layer is cured, the tensile stress state is an inherent property of the material. Final Act. 5-6. The Specification states “polyimide film, when cured, exhibits an intrinsic tensile stress” (Spec. ¶ 33) and “upon curing of polyimide passivation film . . . , passivation film . . . exhibits an intrinsic tensile stress” (Spec. ¶ 50). The Examiner concludes that it would have been obvious to one of ordinary skill in the art at the time of filing to combine the disclosures of Sashida and Wong. Final Act. 6-8. The Examiner determines, inter alia, that combining the disclosures of Sashida and Wong would result in cost savings and facilitate Sashida’s manufacturing method. Final Act. 6. Sashida teaches that polyimide film is cured at 250° C, but provides no details on the curing process, thus one of ordinary skill in the art would look elsewhere-such as to Wong’s variable frequency microwave radiation method-for curing polyimide. Wong teaches that “the variable frequency microwave radiation cured samples achieved a similar level of cure at a rate approximately 30 fold faster than the conventional cure method” (Wong ¶ 84), and its integrated cure disclosed in Wong “can eliminate the need for a stand-alone curing furnace and can further result in semiconductor manufacturing cost savings” (Wong ¶ 101). The Examiner determines that the combination of Sashida and Wong would involve substitution of one known process for another (employing variable frequency microwave radiation, rather than a conventional process, to cure the polyimide passivation layer), which would have been prima facie obvious. Final Act. 7 (citing, e.g., In re Fout, 675 F.2d 297, 301 (CCPA 1982) (“Express suggestion to substitute one equivalent for another need not be present to render such substitution obvious.”). Wong teaches that the Appeal 2021-002751 Application 16/056,827 9 predictable result would be rapid and cost-effective curing of the polyimide passivation layer. See KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 416 (2007) (“The combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.”); see also DePuy Spine, Inc. v. Medtronic Sofamor Danek, Inc., 567 F.3d 1314, 1326 (Fed. Cir. 2009) (“[T]he ‘predictable result’ discussed in KSR refers not only to the expectation that prior art elements are capable of being physically combined, but also that the combination would have worked for its intended purpose.”). The Examiner bears the initial burden, on review of the prior art or on any other ground, of presenting a prima facie case of unpatentability. In re Oetiker, 977 F.2d 1443, 1445 (Fed. Cir. 1992). If the Examiner meets that burden, the applicant bears the burden of coming forward with evidence or argument. Id. “After evidence or argument is submitted by the applicant in response, patentability is determined on the totality of the record, by a preponderance of evidence with due consideration to persuasiveness of argument.” Oetiker, 977 F.2d at 1445. The Examiner meets the initial burden, thus we look to Appellant’s evidence and arguments. First, Appellant argues that Sashida teaches that the polyimide resin is cured at the temperature of 250° C, thus does not teach heating the passivation layer to a temperature between 340° C and a Curie temperature of the ferroelectric material. Appeal Br. 7-8, 11. This argument is unpersuasive at least because the Examiner relies on Wong, not Sashida, for teaching the claimed temperature range. See Final Act. 4-5. “Non- obviousness cannot be established by attacking references individually Appeal 2021-002751 Application 16/056,827 10 where the rejection is based upon the teachings of a combination of references.” In re Merck & Co., 800 F.2d 1091, 1097 (Fed. Cir. 1986). Appellant next argues that “Sashida teaches that the needed tensile stress is provided by the underlying metal film.” Appeal Br. 8. Sashida discloses that “the overall multi-layered metal film exhibits slight tensile stress.” Sashida ¶ 79. This disclosure does not teach away from the inclusion of additional tensile stress in a passivation layer. See In re Fulton, 391 F.3d 1195, 1201 (Fed. Cir. 2004) (Teaching away requires that a reference “criticize, discredit, or otherwise discourage the solution claimed” by Appellant.). Thus, that Sashida discloses a different source of tensile stress does not render the combination of Sashida and Wong nonobvious. Appellant argues that “curing polyimide at a temperature of 250° C (Sashida) results in a mechanically weak polyimide that does not pass Texas Instruments’ reliability tests.” Appeal Br. 8. This argument is not probative to the issue of obviousness, as claim 7 does not relate to Texas Instruments’ reliability tests. See Ans. 10. Moreover, the Examiner does not rely on Sashida’s disclosure of curing temperature for the rejection. See Final Act. 5. In addition, Appellant argues that Wong does not teach a ferroelectric material or a Curie temperature of a ferroelectric material. Appeal Br. 8-9. However, this argument is based on attacking Wong individually, when the rejection is based upon the combined teachings of Sashida and Wong. See Merck, 800 F.2d at 1097 (“Non-obviousness cannot be established by attacking references individually where the rejection is based upon the teachings of a combination of references.”). The Examiner relies on Sashida, not Wong, for teaching use of a ferroelectric material, and inherency for the Curie temperature thereof. See Final Act. 3-4; Ans. 9-10. Appeal 2021-002751 Application 16/056,827 11 According to Appellant, Wong “does not teach ‘cure the material of the passivation layer into a tensile stress state.’” Appeal Br. 9. Appellant’s emphasis on portions of the limitation suggest that the focus of the argument is on whether obtaining the tensile stress state is demonstrated by Wong. In the rejection, the Examiner finds that the tensile stress state is inherent in the cured passivation layer. Final Act. 4. The Specification supports the Examiner’s finding. See Spec. ¶ 33 (stating that the polyimide film, when cured, exhibits an intrinsic tensile stress). Thus here, as in Alcon Research, Ltd. v. Apotex Inc., 687 F.3d 1362, 1369 (Fed. Cir. 2012) and In re Kubin, 561 F.3d 1351, 1357 (Fed. Cir. 2009), “[e]ven if no prior art of record explicitly discusses the [limitation], the [patent applicant's] application itself instructs that [the limitation] is not an additional requirement imposed by the claims on the [claimed invention], but rather a property necessarily present in [claimed invention].” Appellant argues that Wong does not teach a passivation layer of a material comprising a polymer-containing film over the protective overcoat layer. Appeal Br. 9. As with other arguments raised by Appellant, here Appellant attacks Wong individually, when the rejection is based upon the combined teachings of Sashida and Wong. See Merck, 800 F.2d at 1097. The Examiner relies on Sashida, not Wong, for teaching a passivation layer of a material comprising a polymer-containing film over the protective overcoat layer. See Final Act. 3; Ans. 16. Appellant argues that “[n]either Sashida nor Wong et al. teach ‘a duration sufficient to cure the material of the passivation layer into a tensile stress state,’” contending that “the Office Action does not show where either reference teaches” this portion of the limitation. Appeal Br. 10. Based on the Appeal 2021-002751 Application 16/056,827 12 specific language Appellant includes in this argument, the focus of the argument appears to be on whether the duration (length of time) required for curing the material of the passivation layer into a tensile stress state is taught by the references. As discussed supra, the Examiner finds that the tensile stress state is inherent in the cured passivation layer (see Final Act. 4), and the Specification supports the finding (see Spec. ¶ 33). In addition, the Examiner finds in relation to claim 8, which further limits the claimed duration to “less than twenty minutes,” that Wong discloses applying variable frequency microwave radiation to the passivation layer for “between 6 minutes and 10 minutes.” Final Act. 5; see Wong ¶ 83, claims 1 and 8. Thus, Wong discloses the required duration. Appellant disputes that it would have been obvious to combine the teachings of Sashida and Wong. Appeal Br. 10-13. According to Appellant, “Sashida concerns ‘improving characteristics of a capacitor that is covered with an interlayer insulating film, and a method of manufacturing the same,’” but Wong “concerns ‘methods and apparatus for degassing a substrate.’” Appeal Br. 11. We agree with the Examiner that Appellant appears to be asserting that the references are not analogous art, thus not properly combinable. See Ans. 11-13. The scope of analogous art is to be construed broadly. Wyers v. Master Lock Co., 616 F.3d 1231, 1238 (Fed. Cir. 2010) (“The Supreme Court’s decision in KSR International Co. v. Teleflex, Inc., 550 U.S. 398 (2007), directs us to construe the scope of analogous art broadly, stating that ‘familiar items may have obvious uses beyond their primary purposes, and a person of ordinary skill often will be able to fit the teachings of multiple patents together like pieces of a puzzle.’”). To label a reference as analogous Appeal 2021-002751 Application 16/056,827 13 art “merely connotes that it is relevant to a consideration of obviousness under § 103 as ‘prior art.’” In re Sovish, 769 F.2d 738, 742 (Fed. Cir. 1985). We agree with the Examiner that the references are in the same field of endeavor, and are reasonably pertinent to the problem of providing a passivation layer (see Ans. 13), therefore the references are analogous art. The argument is unpersuasive. Appellant contends that it would not have been obvious to combine Wong’s higher temperature for curing polyimide in place of Sashida’s lower temperature for curing polyimide because one of ordinary skill in the art knew “thermal processes following the fabrication of ferroelectric elements, such as ferroelectric capacitors, tend to degrade the switching polarization characteristics of the material.” Appeal Br. 11 (citing Spec. ¶¶ 12-13, 15, 60, 61). This argument is not persuasive of reversible error. See Ans. 14-15. Appellant fails to provide evidence to support the representation of a skilled artisan’s knowledge. In such circumstance, these statements are arguments of counsel, which cannot take the place of evidence in the record. Estee Lauder Inc. v. L’Oreal, S.A., 129 F.3d 588, 595 (Fed. Cir. 1997) (“[A]rguments of counsel cannot take the place of evidence lacking in the record.”). According to Appellant, “one of ordinary skill in the art would not use the more expensive soft cure and hard cure microwave technology processes taught by Wong . . . when Sashida teaches that the less expensive cure ‘at the temperature of 250° C is sufficient.’” Appeal Br. 11-12. This argument is unpersuasive as a reason not to combine the references. Combining Wong and Sashida need not be the best option, but only a suitable option from Appeal 2021-002751 Application 16/056,827 14 which the references do not teach away. Par Pharm., Inc. v. TWI Pharm., Inc., 773 F.3d 1186, 1197-98 (Fed. Cir. 2014). Appellant argues that one of ordinary skill in the art would not substitute Wong’s method of curing a polyimide layer under the metallization layer with Sashida’s method for curing a polyimide layer over the metallization layer because they are not “equivalents known in the art.” This argument is unpersuasive at least because Appellant provides no evidence to support its statement of a skilled artisan’s knowledge. Appellant argues that Wong teaches “an anneal at 340° C,” but claim 7 requires a temperature between 340° C and a Curie temperature of the ferroelectric material. Reply Br. 3-4. Appellant argues the claim 7’s range of temperatures “is outside Wong et al.’s temperature of 340° C.” Id. at 4 (citing Ex parte Song, No. 2020-4060, 2020 WL 6870036 (PTAB Nov. 18, 2020)). This argument is unpersuasive. Wong’s teachings are not limited to curing polyimide at 340° C, but include the temperature range of 300° C to 400° C. See Wong ¶¶ 55, 83. Given that Appellant discloses the Curie temperature of polyimide to be 400° C, Wong’s teaching completely overlaps the claimed temperature range. The overlap of ranges supports prima facie obviousness. In re Peterson, 315 F.3d 1325, 1329 (Fed. Cir. 2003) (“A prima facie case of obviousness typically exists when the ranges of a claimed composition overlap the ranges disclosed in the prior art.”); In re Malagari, 499 F.2d 1297, 1303 (CCPA 1974) (concluding that a claimed invention was rendered prima facie obvious by a prior art reference whose disclosed range (0.020-0.035% carbon) overlapped the claimed range (0.030-0.070% carbon)). Appeal 2021-002751 Application 16/056,827 15 We sustain the rejection of claim 7 as obvious over the combination of Sashida and Wong. Appellant’s arguments regarding nonobviousness of claim 8 (Appeal Br. 13-14) do not differ substantially from those made regarding claim 7. Therefore, we also sustain the rejection of claim 8 as obvious over Sashida and Wong. CONCLUSION The Examiner’s rejections are sustained. More specifically, DECISION SUMMARY Claim(s) Rejected 35 U.S.C. § Reference(s)/Basis Affirmed Reversed 7, 8 103 Sashida, Wong 7, 8 TIME PERIOD FOR RESPONSE No time period for taking any subsequent action in connection with this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv). AFFIRMED