Texas Instruments Incorporated

Patent Trials and Appeals Board

Feb 9, 2022

2021002537 (P.T.A.B. Feb. 9, 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. 15/909,679 03/01/2018 Nazila Dadvand TI-78926 7299 23494 7590 02/09/2022 TEXAS INSTRUMENTS INCORPORATED P O BOX 655474, MS 3999 DALLAS, TX 75265 EXAMINER BRASFIELD, QUINTON A ART UNIT PAPER NUMBER 2814 NOTIFICATION DATE DELIVERY MODE 02/09/2022 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 NAZILA DADVAND, KEITH EDWARD JOHNSON, CHRISTOPHER DANIEL MANACK, and SALVATORE FRANK PAVONE Appeal 2021-002537 Application 15/909,679 Technology Center 2800 Before JAMES B. ARPIN, MINN CHUNG, and AMBER L. HAGY, Administrative Patent Judges. HAGY, Administrative Patent Judge. DECISION ON APPEAL STATEMENT OF THE CASE Pursuant to 35 U.S.C. § 134(a), Appellant1 appeals from the Examiner’s non-final decision to reject claims 1-6.2 Non-Final Act. 1. We have jurisdiction under 35 U.S.C. § 6(b). We REVERSE. 1 Appellant refers to “applicant” as defined in 37 C.F.R. § 1.42(a) (2012). Appellant identifies Texas Instruments Incorporated as the real party in interest. Appeal Br. 3. 2 Claims 1-20 are pending. Non-Final Act. 1. Claims 7-12 are withdrawn from consideration pursuant to 37 C.F.R. § 1.14(b) (2015). Id. at 2. The Examiner has determined that claims 13-20 are allowable. Id. at 1, 6. Appeal 2021-002537 Application 15/909,679 2 CLAIMED SUBJECT MATTER Appellant’s disclosure pertains to “the fabrication of a pillar over a via of a semiconductor die.” Spec. ¶ 2. Of the claims before us, claims 1 and 4 are independent. Claim 1, reproduced below, is illustrative: 1. A method for fabricating a copper pillar over a semiconductor wafer, comprising: providing said semiconductor wafer including a via; forming a layer of titanium tungsten (TiW) over said semiconductor wafer; forming a layer of zinc (Zn) in direct contact with said layer of TiW; forming a patterned photoresist over said layer of Zn, said patterned photoresist being absent over said via; forming said copper pillar over said via, said copper pillar having a perimeter; removing said patterned photoresist; performing an anneal; removing said layer of Zn; and removing said layer of TiW that is located outside said perimeter of said copper pillar. Appeal Br. 24 (Claims App.). Appeal 2021-002537 Application 15/909,679 3 REFERENCES The Examiner relies on the following references: Name3 Reference Date Shih US 2009/0197114 A1 Aug. 6, 2009 Rinne US 2011/0037171 A1 Feb. 17, 2011 Ho US 2018/0047688 A1 Feb. 15, 2018 REJECTIONS Claims 1-3 stand rejected under 35 U.S.C. § 103 as obvious over the combined teachings of Rinne and Shih. Non-Final Act. 2-4. Claims 4-6 stand rejected under 35 U.S.C. § 103 as obvious over the combined teachings of Rinne, Shih, and Ho. Id. at 4-6. OPINION The Examiner relies on Rinne as teaching or suggesting the limitations of claim 1, except for “forming a layer of zinc (Zn) in direct contact with said layer of TiW,” for which the Examiner relies on Shih. Non-Final Act. 2-3. In particular, the Examiner finds Rinne teaches a metal layer in contact with a layer of TiW, but does not teach that the metal is Zn. Id. at 2. The Examiner relies on Shih to teach Zn as the metal layer, finding that: Shih teaches a minor addition of Zn to SAC alloys was found to be effective in controlling the supercooling of the solder alloy below the melting point and, consequently, modifying the bulk microstructure and mechanical properties of the alloys (par 9). Also, Shih teaches the use of Zn to minimize interfacial voiding (par 14-18). Id.; see Ans. 7. 3 All references are identified by the first-named inventor only. Appeal 2021-002537 Application 15/909,679 4 Appellant argues the Examiner’s findings are in error because Shih “does not teach a layer of Zn in direct contact with a layer of TiW, as required by Claim 1,” and, therefore, Shih does not cure the deficiencies of Rinne as noted by the Examiner. Appeal Br. 9. In particular, Appellant argues Shih does not teach a metal layer: Shih et al. teaches the formation of solder bumps containing Zn to the cited (page 3 of the Office Action) “metal pad (27)” that “may include layers of Cu or Ni and Zn, Bi. or Sb” (cited paragraph 0076). . . . Furthermore, Shih et al. teaches that the cited (page 3 of the Office Action) “laminate pad including CuZn plating (par. 76)” is “sputtered onto the UBM containing for example, Cu or Ni” (paragraph 0076). Id. Appellant also takes issue with the Examiner’s reasoning underlying the findings of a motivation to make the combination, noting that the Examiner’s statement of motivation pertains to a feature of Shih that is unrelated to the claimed Zn layer in the present invention: The Appellant also submits that the statement (twice) on page 3 of the Office Action that “Shih teaches the use of Zn to minimize interfacial voiding (par 14-18)” is unrelated to the claimed “layer of zinc” because Shih et al. teaches that the location of minimized interfacial voiding is the “interface between the solder and the solder capture pad” (cited paragraphs 0014, 0017, and 0018) that are the interface between elements 24 and 29 of cited paragraph 0076 and FIG. 7 of Shih et al. That interface of Shih et al. corresponds to the interface between element 80 and 35 of the Applicant’s invention (FIG. 1) and does not touch the claimed zinc layer 130 at any location. Id. at 10-11; see Reply Br. 4-5. We are persuaded of Examiner error in the rejection. Claim 1 requires both “forming a layer of zinc (Zn) in direct contact with said layer of TiW” and also “removing said layer of Zn.” Appeal Br. 24 (Claims App.). As Appeal 2021-002537 Application 15/909,679 5 Appellant correctly contends, neither Rinne nor Shih teaches such a layer. Appeal Br. 9-11. The Examiner’s finding that the ordinarily skilled artisan would have had reason to combine the teachings of Shih with Rinne to choose Zn as the metal layer overlying the TiW layer in Rinne (Non-Final Act. 2) is not supported. Shih discloses Zn as a component of solder bumps used to electrically interconnect a die or chip to a substrate. Shih ¶¶ 74, 76. Shih further discloses sputtering a layer of Zn onto the under bump metallurgy (UBM) as a way of including Zn in the final solder joint. Id. ¶ 76. Although Shih discloses use of Zn, the Examiner does not adequately tie that teaching to the claimed invention or explain how and why the ordinarily skilled artisan would have been motivated to modify Rinne to achieve the claimed invention-namely, to include a Zn layer that is first added and then partially removed. Rather, as Appellant points out: Claim 1 positively recites forming a layer of titanium tungsten (TiW) over a semiconductor wafer (step 220; FIG. 4), forming a layer of zinc (Zn) in direct contact with the layer of TiW (step 240; FIG. 5), and forming a copper pillar over the layer of zinc (step 250; FIG. 7). In addition, as stated in paragraph 0023 of the Specification, solder resist 80 (such as SnAg) is placed on the exposed top portion of the copper pillar 70 (FIG. 1). Therefore, the cited teachings of Shih et al. concern the opposite side of the copper pillar than where the layer of zinc interdiffuses with the copper pillar 70 to form brass element 75 (FIG. 1; see also paragraph 0011 ). (Note that the Appellant’s “solder resist 80” (paragraph 0023; FIG.1) is a separate element from the Appellant’s “layer of Zn 130” (paragraph 0018; FIG. 5)). Reply Br. 3-4 (emphasis added). Appellant also persuasively contends: Furthermore, one of ordinary skill in the art would not look to teachings concerning the “interface between the solder and the Appeal 2021-002537 Application 15/909,679 6 solder capture pad” (cited paragraphs 0014, 0017, and 0018) that are the interface between elements 24 and 29 of cited paragraph 0076 and FIG. 7 of Shih et al. (that corresponds to the interface between element 80 and 35 of the Appellant’s invention (FIG. 1)) to modify the claimed method of forming the zinc layer 130. Id. at 5. In summary, for essentially the reasons expressed by Appellant, we are persuaded of Examiner error in the 35 U.S.C. § 103 rejection of claim 1, and we, therefore, do not sustain that rejection, or the rejection of claim 4, which contains commensurate limitations and was rejected on similar reasoning. See Non-Final Act. 4-6. Dependent claims 2, 3, 5, and 6 stand with their respective independent claims. CONCLUSION The Examiner’s rejections of claims 1-6 are reversed. DECISION SUMMARY In summary: Claims Rejected 35 U.S.C. § Reference(s)/Basis Affirmed Reversed 1-3 103 Rinne, Shih 1-3 4-6 103 Rinne, Shih, Ho 4-6 Overall Outcome 1-6 REVERSED