Ex Parte LIDownload PDFPatent Trial and Appeal BoardFeb 21, 201713942906 (P.T.A.B. Feb. 21, 2017) Copy Citation 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. 13/942,906 07/16/2013 Jung-Jui Li TSMCP309US (TSMC2013-0496 8206 107476 7590 02/23/2017 Fsiohweiler Rr Asisinoiates; T T C EXAMINER 629 Euclid Avenue, Suite 1000 National City Bank Building GATES, BRADFORD M Cleveland, OH 44114 ART UNIT PAPER NUMBER 1713 NOTIFICATION DATE DELIVERY MODE 02/23/2017 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): docketing @ eschweilerlaw. com PTOL-90A (Rev. 04/07) UNITED STATES PATENT AND TRADEMARK OFFICE BEFORE THE PATENT TRIAL AND APPEAL BOARD Ex parte TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD. Appeal 2016-001488 Application 13/942,906 Technology Center 1700 Before LINDA M. GAUDETTE, RAE LYNN P. GUEST, and JENNIFER R. GUPTA, Administrative Patent Judges. GAUDETTE, Administrative Patent Judge. DECISION ON APPEAL Appeal 2016-001488 Application 13/942,906 Appellant1 appeals under 35 U.S.C. § 134(a) from the Examiner’s decision2 finally rejecting claims 1—10 and 12—21. We have jurisdiction under 35 U.S.C. § 6(b). We REVERSE. Claim 1 is representative of the invention, and is reproduced below: 1. A method of fabricating a semiconductor device, the method comprising: providing a substrate having an oxide layer; removing at least a portion of the oxide layer by reacting HF and NH3 with the oxide layer to form a nitride layer over an unconsumed portion of the oxide layer; removing the nitride layer and leaving a nitride precipitate byproduct on the unconsumed portion of the oxide layer; and removing the nitride precipitate byproduct by dipping the substrate in a liquid solution of phosphoric acid. App. Br. 9 (Claims App’x). The claims stand rejected under 35 U.S.C. § 103 as follows: 1. claims 1, 6—8, 10, 12—15, and 17—20 over Hur et al. (US 2010/0210099 Al, pub. Aug. 19, 2010 (“Hur”)) and Rink et al. (US 2006/0153331 Al, pub. July 13, 2006 (“Rink”)); and 2. claims 2—5, 9, 16, and 21 over Hur, Rink, and Kiehlbauch et al. (US 2009/0275205 Al, pub. Nov. 5, 2009 (“Kiehlbauch”)). Of the appealed claims, claims 1,14, and 18 are independent. See App. Br. 9 and 11—12 (Claims App’x). Each of claims 1, 14, and 18 recites a method of fabricating a semiconductor device that includes steps of 1 Appellant identifies itself as the real party in interest. Appeal Brief filed May 21, 2015 (“App. Br.”), 2. The named inventor is Jung-Jui Li. 2 Final Office Action mailed Dec. 4, 2014 (“Final Act.”). 2 Appeal 2016-001488 Application 13/942,906 (1) removing a nitride layer formed over an unconsumed portion of an oxide layer on a substrate, during which removal nitride precipitates are formed on the unconsumed oxide layer, and (2) removing the nitride precipitates by dipping the substrate in a liquid solution of phosphoric acid. The only process explicitly described in the Specification for removing the nitride layer is “heating” (Specification filed July 16, 2013 (“Spec.”) 119), for example, by placing the semiconductor device in a chamber on a heating stage set to a temperature “over about 90 degrees C” whereby the nitride layer is evaporated from the device’s surface as a gas-phase byproduct {id. 31, 46). Claims 14 and 18 also explicitly recite heating the substrate to evaporate the nitride layer. The Specification discloses that the gas-phase byproduct produced during heating of the nitride layer is removed from the chamber using an exhaust or other mechanism, but some amount (“nitride relative precipitate”) remains on the surface of the oxide layer. Spec. H 31, 46. Examples of the nitride relative precipitates include, NO-, N02-, N03-, NH4+, NH20H, NH2(OH), and the like.” Id. H 30, 45. According to the Specification, dipping the substrate in a phosphoric acid bath removes substantially all the nitride relative precipitates that remain on the oxide layer. Id. H 33, 48. The respective positions of the Examiner and Appellant raise the following issue on appeal: Did the Examiner reversibly err in finding one of ordinary skill in the art at the time of the invention would have modified Hur’s method of forming a metal silicide layer on a semiconductor substrate to include a step of “dipping the substrate in a liquid solution of phosphoric acid to remove . . . nitride precipitate” as recited in appealed claims 1,14, 3 Appeal 2016-001488 Application 13/942,906 and 18? See generally, App. Br. 4—7. We answer this question in the affirmative for the reasons discussed below. The Examiner finds Hur discloses a method of making a semiconductor device that includes a step of removing a portion of oxide layer 130 formed on semiconductor substrate 100 using an etchant such as HF/NH?. Final Act. 3. The Examiner further finds Hur discloses that the etchant reacts with the oxide to form a nitride-containing layer (NH^SiFe, which is then removed. Id. The Examiner finds Hur does not teach explicitly that the process of removing the nitride-containing layer leaves byproducts on the oxide layer, and, therefore, Hur’s method does not include a step of removing such byproducts by dipping the substrate in a liquid solution of phosphoric acid as required by the appealed claims. Id. The Examiner finds, however, that Rink discloses that residues form on the surface of silicon oxide during an etching process, and that these residues can be removed in a subsequent step of placing the substrate in a bath containing a phosphoric acid cleaning solution. Id. The Examiner finds one of ordinary skill in the art at the time of the invention would have modified Hur’s method by adding a step of placing the semiconductor substrate in a bath containing a phosphoric acid cleaning solution based on Rink’s teaching that such step provides an effective, yet inexpensive means of removing residue formed during etching of an oxide layer with little environmental impact. Id. at 4. Appellant argues Hur discloses that all solid byproducts formed by etching the oxide layer with HF/NH3 are removed by heating the substrate to a temperature of 100 degrees C or more to sublimate the byproducts. See App. Br. 5; Reply Brief filed Nov. 17, 2015 (“Reply Br.”), 3^4. Appellant 4 Appeal 2016-001488 Application 13/942,906 thus contends one of ordinary skill in the art would not have had a reason to modify Hur’s process to include another step of removing byproducts, i.e., Rink’s step of dipping the substrate in a liquid solution of phosphoric acid. See App. Br. 6—7; Reply Br. 4—5. Appellant has argued persuasively that the Examiner’s fact finding and reasoning is insufficient to support a finding that the ordinary artisan would have had a reason to modify Hur to include a step of dipping the substrate in a liquid solution of phosphoric acid. As argued by Appellant (see App. Br. 5; Reply Br. 3—4), and conceded by the Examiner (Final Act. 3), Hur does not disclose that byproducts remain on the substrate after the sublimation process (see, e.g., Hur || 71—74). Rink discloses, very generally, that residues are formed at the surface of the semiconductor body during an etch process (Rink || 1, 24) and that these residues can be removed using a cleaning agent comprising phosphoric acid (id. 125). The Examiner does not identify, however, nor do we find, any disclosure in Rink that the residues removed by the phosphoric acid cleaning agent include byproducts that remain on the semiconductor oxide layer after removal of a nitride-containing layer. See generally, Final Act. 3—11; Examiner’s Answer mailed Sept. 17, 2015 (“Ans.”), 15—17. Because the Examiner has not identified support in the prior art for finding that one of ordinary skill in the art would have included an additional step of using a phosphoric acid cleaning solution to remove residue from Hur’s oxide layer, despite Hur’s teaching that all byproducts are removed by the disclosed sublimation process, we find the Examiner’s obviousness determination is based on improper hindsight reconstruction. 5 Appeal 2016-001488 Application 13/942,906 Therefore, we do not sustain the Examiner’s rejections of claims 1—10 and 12-21. REVERSED 6 Copy with citationCopy as parenthetical citation