Ex Parte Khater

Patent Trial and Appeal BoardNov 15, 2012

11161286 (P.T.A.B. Nov. 15, 2012)

UNITED STATES PATENT AND TRADEMARK OFFICE ________________ BEFORE THE PATENT TRIAL AND APPEAL BOARD ________________ Ex parte MARWAN H. KHATER ________________ Appeal 2010-006520 Application 11/161,286 Technology Center 2800 ________________ Before KALYAN K. DESHPANDE, JASON V. MORGAN, and JOHN G. NEW, Administrative Patent Judges. MORGAN, Administrative Patent Judge. DECISION ON APPEAL Appeal 2010-006520 Application 11/161,286 2 STATEMENT OF THE CASE Introduction This is an appeal under 35 U.S.C. § 134(a) from the Examiner’s Final Rejection of claims 1, 2, 4, 6, 8–15, and 19. Claims 3, 5, 7, and 16–18 are canceled. See App. Br. 2. We have jurisdiction under 35 U.S.C. § 6(b)(1). We affirm. Invention The invention relates to methods of fabricating a bipolar transistor for improved isolation, passivation, and critical dimension control. See Title. These methods can include disposing an additional layer of silicon nitride over a passivation oxide layer as a sacrificial layer which protects the passivation oxide layer from being reduced in thickness or being undercut during a reactive ion etch (RIE) process and one or more cleaning processes conducted after the RIE process. See Abstract. Exemplary Claim 1. A method of making a bipolar transistor, comprising: forming a portion of said bipolar transistor including a collector region, an intrinsic base layer overlying said collector region, a mandrel having an upwardly rising wall overlying a first portion of said intrinsic base layer, with an etch stop layer formed between said intrinsic base layer and said mandrel, a replaceable dielectric spacer disposed on said wall of said mandrel, and a raised extrinsic base layer overlying a second portion of said intrinsic base layer, wherein said etch stop includes a layer of oxide deposited to overlie said intrinsic base layer and a layer of nitride deposited to overlie said layer of oxide; etching to remove said mandrel to form an emitter opening having an upwardly rising wall by processing Appeal 2010-006520 Application 11/161,286 3 including reactive ion etching said mandrel selective to a material of said etch stop layer; and forming a replacement dielectric spacer on said wall of said emitter opening and forming an emitter layer separated from said raised extrinsic base layer by at least said replacement dielectric spacer. App. Br. 11 (Claims App’x) (emphasis added). Rejections The Examiner rejects claims 1, 4, 6, 8, 10–13, and 19 under 35 U.S.C. § 103(a) as being unpatentable over Khater (US 2004/0188797 A1; Sept. 30, 2004; filed Mar. 28, 2003) (“Khater ’797”) and Yi (US 2004/0157387 A1; Aug. 12, 2004). Ans. 5–12. The Examiner rejects claim 2 under 35 U.S.C. § 103(a) as being unpatentable over Khater ’797, Yi, and Appellant’s Admitted Prior Art (Spec. fig. 3A and ¶ [0003]) (“AAPA”). Ans. 12. The Examiner rejects claims 14 and 15 under 35 U.S.C. § 103(a) as being unpatentable over Khater ’797, Yi, and Trivedi (US 6,524,901 B1; Feb. 25, 2003). Ans. 13 – 15. The Examiner rejects claim 9 under 35 U.S.C. § 103(a) as being unpatentable over Khater ’797, Yi, Trivedi, and AAPA. Ans. 15 – 18. ISSUE Does Yi teach away from modifying Khater ’797 to include “wherein said etch stop includes a layer of oxide deposited to overlie said intrinsic base layer and a layer of nitride deposited to overlie said layer of oxide,” as recited in claim 1? Appeal 2010-006520 Application 11/161,286 4 ANALYSIS The Examiner finds that Khater ’797 teaches most of the recitations of claim 1, including a third silicon oxide layer OX3 that forms an etch stop layer. See Ans. 5 – 6 (citing, e.g., Khater ’797 fig. 2Q and ¶ [0038]). The Examiner acknowledges that Khater ’797 fails to expressly disclose “wherein said etch stop includes a layer of oxide deposited to overlie said intrinsic base layer and a layer of nitride deposited to overlie said layer of oxide,” as recited in claim 1. See Ans. 6. Thus, the Examiner relies on Yi, which is directed to a method for manufacturing self-aligned BiCMOS, to illustrate that this claimed feature is well-known in the art. See id. Specifically, the Examiner relies on Yi’s teaching of applying a thin oxide layer 120 and a nitride layer 122 on a SiGe base layer 118 to teach or suggest an etch stop that includes a layer of oxide deposited on an intrinsic base layer and a nitride layer deposited on the oxide layer. See Ans. 6 (citing Yi figs. 2 – 3 and ¶¶ [0045] – [0046]). Appellant contends that the Examiner erred in relying on the combined teachings of Khater ’797 and Yi, arguing that “Yi’s description of the formation of and extent of oxide and nitride layers teach away from the method described in the ’797 Patent [Application] and, therefore, cannot be combined with the ’797 Patent [Application] to render the claims obvious.” App. Br. 7. Specifically, Appellant argues that: Yi’s requirement that the blanket oxide and nitride layers 120, 122, 124 of Yi be present adjacent to the polysilicon plug 132 when the polysilicon plug is removed teaches away from the claimed fabrication method (cl.l) that requires a “raised extrinsic base layer” be disposed overlying a second portion of an intrinsic base. The blanket oxide and nitride layers 120, 122, 124 of Yi are insulating layers which preclude conductive Appeal 2010-006520 Application 11/161,286 5 connection. A raised extrinsic base layer would not be a “raised extrinsic base layer” if it is not conductively connected to the intrinsic base layer (See Fig. 2P and ¶[0049] of the ’797 Patent [Application]), because then, the transistor would not operate. App. Br. 9. The Examiner correctly notes that the test for whether the combination of Khater ’797 and Yi is obvious is not whether the features of Yi can be bodily incorporated into the method taught or suggested by Khater ’797. Rather, the test is what the combined teachings of Khater ’797 and Yi would have suggested to an artisan of ordinary skill. See Ans. 18–19; see also In re Keller, 642 F.2d 413, 425 (CCPA 1981). We find that Appellant’s arguments are not persuasive of error because “the exact process that Yi uses the taught etch stop layers for need not be bodily incorporated into the ’797 patent” application. Ans. 19. Furthermore, we find that the Examiner properly relies on Yi for the limited teaching of using an oxide layer with an overlying nitride layer to form multiple etch stop layers of different etch rates. See Ans. 6 – 7 and 19. The Examiner correctly finds that Yi provides evidence that “multiple etch stop layers of different etch rates are well known in the art and the application of said multiple etch stop layers provides the predictable result of allowing for enhanced etching control.” Ans. 19. We agree with the Examiner. Modifying Khater ’797 to replace the third silicon oxide layer OX3 etch stop layer with Yi’s oxide and nitride layers represents alteration of Khater ’797 by mere substitution of one element for another element known in the field to yield a predictable result. See KSR Int’l, Co. v. Teleflex, Inc., 550 U.S. 398, 416 (2007). Appeal 2010-006520 Application 11/161,286 6 Appellant also does not persuasively show that Yi “criticizes, discredits, or otherwise discourages” the use of multiple oxide and nitride etch stop layers in other fabrication processes, such as the one described in Khater ’797. See In re Fulton, 391 F.3d 1195, 1201 (Fed. Cir. 2004). Therefore, we agree with the Examiner that Yi does not teach away from modifying Khater ’797 to include “wherein said etch stop includes a layer of oxide deposited to overlie said intrinsic base layer and a layer of nitride deposited to overlie said layer of oxide,” as recited in claim 1. Accordingly, we sustain the Examiner’s 35 U.S.C. § 103(a) rejection of claim 1, and of claims 2, 4, 6, 8–15, and 19, which are not argued separately with sufficient specificity. See App. Br. 9–10. DECISION The Examiner’s decision to reject claims 1, 2, 4, 6, 8–15, and 19 is affirmed. 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 msc