Ex Parte Dautet et al

Patent Trial and Appeal BoardMay 13, 2016

11725661 (P.T.A.B. May. 13, 2016)

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. 11/725,661 03/20/2007 Henri Dautet 41067-6106 6544 57449 7590 05/13/2016 SHEEHAN PHINNEY BASS & GREEN, PA c/o PETER NIEVES 1000 ELM STREET MANCHESTER, NH 03105-3701 EXAMINER SHINGLETON, MICHAEL B ART UNIT PAPER NUMBER 2815 MAIL DATE DELIVERY MODE 05/13/2016 PAPER 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. PTOL-90A (Rev. 04/07) UNITED STATES PATENT AND TRADEMARK OFFICE ____________________ BEFORE THE PATENT TRIAL AND APPEAL BOARD ____________________ Ex parte HENRI DAUTET and RICHARD SEYMOUR ____________________ Appeal 2014-001887 Application 11/725,661 Technology Center 2800 ____________________ Before ADRIENE LEPIANE HANLON, CATHERINE Q. TIMM, and JAMES C. HOUSEL, Administrative Patent Judges. TIMM, Administrative Patent Judge. DECISION ON APPEAL1 STATEMENT OF CASE Appellants2 appeal the Examiner’s decision to reject claims 1, 6–8, 10–12, 14–21, 28, 29, and 31–37 under 35 U.S.C. § 103(a). Claims 1, 6–8, 1 In our opinion below, we refer to the Specification filed March 20, 2007 (Spec.), Final Office Action mailed Dec. 10, 2012 (Final), the Appeal Brief filed June 4, 2013 (Appeal Br.), the Examiner’s Answer mailed Aug. 15, 2013 (Ans.), and the Reply Brief filed Oct. 15, 2013 (Reply Br.). 2 Appellants identify the real party in interest as Excelitas Canada Inc. Appeal Br. 1. Appeal 2014-001887 Application 11/725,661 2 10–12, 14–21, 28, 29, and 31–35 stand rejected as obvious over Kobayashi3 in view of McCann4 and Neilson.5 To reject claims 36 and 37, the Examiner adds Nishizawa6 or Bui7 or Veliadis.8 We have jurisdiction under 35 U.S.C. §§ 6(b) and 134(a). We AFFIRM. The claims are directed to an avalanche photodiode with an active substrate bonded to a handle substrate. The active substrate includes a heavily doped layer at the bonded surface. Claim 1, with emphasis on limitations at issue in the appeal, is reproduced below: 1. An avalanche photodiode comprising: an electrooptically active substrate, wherein the active substrate includes a portion of a first wafer, wherein the active substrate has a lightly doped silicon region, and wherein the active substrate includes a heavily doped layer at a first silicon surface of the active substrate; a handle substrate including heavily doped silicon, wherein the handle substrate includes a portion of a second wafer, and wherein a second silicon surface of the handle substrate is directly bonded to the first silicon surface of the active substrate; and an avalanche photodiode active area formed in the active substrate including a high field region for generating avalanche current gain, 3 Kobayashi, US 5,596,186, patented Jan. 21, 1997. 4 McCann et al., US 2004/0087109 A1, pub. May 6, 2004. 5 Neilson et al., US 6,054,369, pat. Apr. 25, 2000. 6 Nishizawa, US 4,727,649, pat. Mar. 1, 1988. 7 Bui et al., US 7,655,999 B2, pat. Feb. 2, 2010. 8 Veliadis, US 7,863,647 B1, pat. Jan. 4, 2011. Appeal 2014-001887 Application 11/725,661 3 wherein the heavily doped layer is adapted to improve interface quality between the active substrate and the handle substrate. Claims Appendix of the Appeal Br. (emphasis added). OPINION As Appellants focus their arguments on the rejection of claim 1, we do the same. Kobayashi teaches an avalanche photodiode with an n+ silicon substrate 10 upon which is grown an n- epitaxial growth layer 11 that serves as the active substrate. Kobayashi, col. 6, l. 66–col. 7, l. 25; Fig. 1. The two layers of silicon are present but not made by the direct bonding process recited in claim 1. Kobayashi does not expressly teach a heavily doped layer at the surface of the active substrate adapted to improve interface quality. In Kobayashi, the n+ substrate 10 has a higher doping concentration than the n- epitaxial growth layer 11. Kobayashi, col. 7, ll. 3–6 (layer 11 has an impurity concentration of 1x1014 cm-3 and substrate 10 has an impurity concentration of 1x1017 cm-3). The Examiner advances several bases for rejection. First, although Kobayashi’s photodiode is not made by directly bonding an active substrate to a handle substrate, the Examiner finds that the process differences do not patentability distinguish the claimed photodiode from the one taught by Kobayashi. Final 4–5. To support this rejection, the Examiner relies upon McCann as extrinsic evidence supporting the finding that the structure is not patentably different. Id. In another basis for rejection, the Examiner concludes it would have been obvious to have replaced the substrate of Kobayashi with two wafers Appeal 2014-001887 Application 11/725,661 4 bonded together given that the two alternative structures are art-recognized equivalents as taught by McCann. Final 5–7. The Examiner relies upon Neilson as teaching that it was known in the prior art to heavily dope prior to bonding to improve the interface. Final 7. We will consider the issues for the obviousness of substituting Kobayashi’s epitaxial growth substrate 11 and substrate 10 with McCann’s bonded substrates first. McCann is directed to a method of direct bonding two silicon wafers. McCann ¶ 1. McCann indicates that the method can be used to form a range of devices including PIN diodes and bipolar devices where two silicon layers of different resistivity are required. McCann ¶¶ 2–3. McCann describes the direct bonding method as an alternative that overcomes some of the problems with the epitaxial growth method. McCann ¶ 3. McCann fusion bonds the two substrates together in a way that minimizes interfacial oxide and stress at the bond interface. McCann ¶¶ 9– 12. Because oxide is minimized at the bond interface, and effectively eliminated, dopant diffused into one of the wafers diffuses through the bond interface to the other wafer without hindrance. McCann ¶ 82. Appellants contend that the ordinary artisan would have had no reason to modify Kobayashi’s avalanche photodiode in view of McCann’s “fairly generic disclosure,” and the Examiner has not presented a compelling reason why the modification would have been obvious. Appeal Br. 13–14. But McCann’s “fairly generic disclosure” specifically identifies the direct bonding method as a substitute for epitaxially grown layers on silicon substrates to form bipolar devices where two silicon layers of different resistivity are required. The photodiode of Kobayashi is just such a Appeal 2014-001887 Application 11/725,661 5 structure. Moreover, McCann discusses the pros and cons of using two directly bonded substrates instead of an epitaxially grown layer on a substrate. Both the direct bonding and epitaxial growth methods were known in the art, and the evidence indicates that those of ordinary skill in the art would have reasonably expected the direct bonding method to solve the problems with epitaxial growth discussed in McCann. “The combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.” KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 416 (2007). A preponderance of the evidence supports the Examiner’s finding of a reason to substitute the epitaxial growth method of Kobayashi with the direct bonding method of McCann. Appellants further contend that none of the prior art references “would have suggested adding a ‘heavily doped layer’ to ‘improve interface quality’ between Kobayashi’s epitaxial growth layer 11 to Kobayashi’s silicon substrate 10, as recited by claim 1.” Appeal Br. 14; Reply Br. 6. But the prior art need not suggest adding a ‘heavily doped layer’ to ‘improve interface quality’ in order to meet the requirements of the claim. This is because the claim is directed to an avalanche photodiode; a structure. Thus, the claim language “the heavily doped layer is adapted to improve interface quality between the active substrate and the handle substrate” must be read to determine how the language limits the structure of the photodiode; the layer need not be added for the reason set forth by the claim. See In re Michlin, 256 F.2d 317, 320 (CCPA 1958) (“It is well settled that patentability of apparatus claims must depend upon structural limitations and not upon statements of function.”). At best, the “improve interface quality” Appeal 2014-001887 Application 11/725,661 6 language may limit the range of dopant concentrations within the heavily doped layer. We turn to the Specification to determine whether and how the language limits the dopant concentration. In our search to determine the concentrations of dopants that would “improve interface quality” and thus be encompassed by the language of the claim, we find little guidance in the Specification. All we find is the naked statement that “[h]eavily doped silicon layer 20 improves interface quality between substrates 12 and 14.” Spec. 8:19–22. The Specification does not discuss what concentrations of dopant come under the umbrella of “heavily doped,” what concentrations “improve interface quality,” or even what property improvements constitute an improvement in interface quality. The Specification also states that, alternatively, an oxide layer may be used to improve interface quality. Spec. 8:23–9:2. Thus, what constitutes an improvement to interface quality is further clouded. In the absence of any indication that a particular concentration is required to improve interface quality, we determine the active layer need only have a heavily doped layer having some concentration of the dopant. Kobayashi dopes substrate 10 to a concentration of 2x1017 cm-3, and epitaxial growth layer 11 to a concentration of 1x1014 cm-3. Kobayashi, col. 7, ll. 4–6. The Examiner finds, and Appellants do not dispute, that substrate 10 of Kobayashi is heavily doped. Final 6; Appeal Br. 7, 9–12, 14. McCann suggests replacing the epitaxially grown layer 11 on substrate 10 with two substrates such that there would be two substrates in place of epitaxially grown layer 11 bonded to a substrate 10. McCann teaches that dopant diffused into one of the substrates diffuses unhindered through the bond interface to the other substrate. McCann ¶ 82. Diffusion of dopant from the Appeal 2014-001887 Application 11/725,661 7 heavily doped substrate 10 of Kobayashi into the bonded substrate replacing epitaxial layer 11 (per the bonding method of McCann) would result in a heavily doped layer in the active substrate at the concentrations as required by the “improve interface quality” language of claim 1. Moreover, the Examiner relies upon Neilson as evidence that it was conventional to heavily dope prior to bonding to improve the interface, and concludes it would have been obvious to one of ordinary skill to further employ such doping “to control the density of the recombination centers to be that desired as it is taught by Neilson.” Final 7. Appellants do not address this finding and conclusion, but merely state that none of the references suggest what is claimed. Appeal Br. 14. Appellants have not identified a reversible error in the Examiner’s finding and conclusion in this regard. As to the Examiner’s alternate basis of rejection that relies upon Kobayashi with McCann used as extrinsic evidence, Appellants have not convinced us of a reversible error in this basis for rejection. Appellants as well as Kobayashi and McCann all create a structure with two layers of material, each material being silicon. Whether directly bonding or epitaxially growing silicon onto silicon, the result is a two-layer silicon structure. Where one defines the boundary between the heavily doped lower substrate and the heavily doped layer in the active substrate does not seem to result in a patentable distinction between the claimed and prior art devices. McCann indicates that dopant diffuses across the interface. Appellants rely upon arguments addressed above for all the claims and both rejections. Appellants have not identified a reversible error in either rejection. Appeal 2014-001887 Application 11/725,661 8 CONCLUSION We sustain the Examiner’s rejections. DECISION The Examiner’s decision is affirmed. 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). AFFIRMED