Ex Parte Liu et alDownload PDFPatent Trial and Appeal BoardAug 29, 201813755058 (P.T.A.B. Aug. 29, 2018) Copy Citation UNITED STA TES p A TENT AND TRADEMARK OFFICE APPLICATION NO. FILING DATE 13/755,058 01/31/2013 107476 7590 09/05/2018 Eschweiler & Potashnik, LLC Rosetta Center 629 Euclid Ave., Suite 1000 Cleveland, OH 44114 FIRST NAMED INVENTOR Po-Chun Liu 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 ATTORNEY DOCKET NO. CONFIRMATION NO. TSMCP228US 7933 EXAMINER HATZILAMBROU, MARK ART UNIT PAPER NUMBER 2891 NOTIFICATION DATE DELIVERY MODE 09/05/2018 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 PO-CHUN LIU, 1 Chi-Ming Chen, Chung-Yi Yu, and Chia-Shiung Tsai Appeal2017-011047 Application 13/755,058 Technology Center 2800 Before ROMULO H. DELMENDO, MARK NAGUMO, and JEFFREY R. SNAY, Administrative Patent Judges. NAGUMO, Administrative Patent Judge. DECISION ON APPEAL Taiwan Semiconductor Manufacturing Company Limited ("Liu") timely appeals under 35 U.S.C. § 134(a) from the Final Rejection2 of all pending claims 9--11, 13-18, and 3 5--40. We have jurisdiction. 35 U.S.C. § 6. We affirm. 1 The applicant under 3 7 C.F .R. § 1.46, and hence the appellant under 35 U.S.C. § 134, is the real party in interest, identified as Taiwan Semiconductor Manufacturing Company Limited. (Appeal Brief, filed 26 April 2017 ("Br."), 1.) 2 Office Action mailed 26 August 2016 ("Final Rejection"; cited as "FR"). Appeal 2017-011047 Application 13/755,058 A. Introduction 3 OPINION The subject matter on appeal relates to high electron mobility transistors ("HEMTs"). The majority charge carriers in HEMTs, as the name indicates, are electrons, which form a high mobility, low resistivity two-dimensional electron gas ("2DEG") in a high resistivity gallium nitride ("GaN") channel layer under an active layer such as aluminum doped gallium nitride ("AlGaN"). As a result of interactions at the AlGaN:GaN heterojunction, the 2DEG forms when an appropriate voltage is applied to the gate over the channel between the source and the drain of the transistor. (Spec. 1 [0001].) The prior art of record indicates that HEMTs are very useful for high power, high frequency applications. (Harris4 1 [0003].) That prior art indicates further that a high purity channel is important to achieve high mobility in the 2DEG (id. at [0005]), and a high resistance buffer layer underlying the channel is critical to prevent current leakage (id. at [0006]). HEMT 1005 is illustrated in Figure 1, shown on the following page. 6 AlxGao-x)N active layer 102 forms heterojunction 104 at the interface with first resistivity GaN buffer layer 106, which is also referred to as a "channel 3 Application 13/755,058, High electron mobility transistor structure, filed 31 January 2013. We refer to the "'058 Specification," which we cite as "Spec." 4 Full cite at 7 n.11, infra. 5 Throughout this Opinion, for clarity, labels to elements are presented in bold font, regardless of their presentation in the original document. 6 The Specification does not make clear whether HEMT 100 is prior art; but the claimed invention is an improvement on it. 2 Appeal 2017-011047 Application 13/755,058 layer" or as a "breakdown voltage layer." (Id. at 2 [0008].) As shown, first breakdown voltage layer 106 forms a breakdown voltage bilayer with underlying second breakdown voltage layer 110, which has a higher resistance than first breakdown voltage layer 106. HEMT 100 further comprises underlying AlyGa(l-y)N thermal expansion layer 112, aluminum nitride ("AlN") buffer layer 114, and substrate 116. (Id.) Contacts for a source, gate, and drain are not shown. The 2DEG is indicated as dashed line 108. (Id. at [0009].) {Figure 1 is shown below} riM ·)os~·-, i - ~\ I i \, ,i>,l,S31>,,,_ ,,N i,ct\,0 t,,y0r ... / 1 ~ \ ~ ,.. l ,• l,_ ...... t'··· ,. . ma , .. m. . ---~ --~" l ~.~..,-· ~~":I'~:~ ....... ~ >ti·.~--~~~ .. q,t. r '+(~ ,-r. ~·~ ·~ t--+t ~ '\'I:\. Joto~~)-."!~~ ~' f ~ '-...' \...!, ..._, V ~~ \..~ V ,...i,: ,;,.>. ~"" 'W ' 'w \~._, ..__. ~' 1 ~ ti!"'S: l i ''' Ri•<:,i<>~."''' \ i OS l l ::Nc.,:n~~~ ~ ~ ' ~ .. ,.. .. ~ ... .: ... J ;} ... · "' ~ ' ~~ ~~--= ~ ~~ ... ~ · l ~ va::,.. ·e Sreat<<:$o'wn f L...................... . ... ... .lllli. ... . ...... ... ........ .. ......... ~ .l -'" \.~o!>,S \ : j l ~-·),i,'i ... ~,. v• :i-,.,_l(;i:~" 1 ~ :-~.... . . . . . . . . ... . . . . ~ ~ S.¢.c-0-tsd ~ ~ 2 · .~ R~~:1:.,eyr.:.~·rt~r G;sN B~ffu.r L~~y~tr ! ! ~.._: .,~-~ .. ~& ,.: l :: 11.Q l l ""'''' '~ ~ ~ . : t v~~~ \ i j l ' . , : "'"''""" '"""",lk·-'"'" •• ,., 1 · :,--, ................. ~ ......................................... ~ ............................... -, : A:N 6uf>131· L,sy'* ! :: t ·1,'.1, ~ :' .............................................. ······· ........................................ ~ :: S S~it-=~f.ra~e ! .Uf ! ·· ................. """"' .............................. """ ....................................................................... ~ ........................ ~-.-.-. ................. ~ .................... ...........,. ..... ..;: {Figure 1 shows a diagram ofHEMT 100} The '058 Specification teaches that the resistance of the high resistivity GaN layers may be increased further ( equivalently, the "breakdown voltage" may be increased) by doping with, e.g., carbon ("C") 3 Appeal 2017-011047 Application 13/755,058 (Id.) However, a heavily carbon-doped GaN layer, which is grown at reduced pressure and temperature, is said to have degraded crystal quality, "which in tum degrades electron mobility within the 2DEG, as well as a drain saturation current (Idsat) and dynamic on-state resistance (Rm) of the HEMT." (Id. at 2 [0009].) The Specification reveals that these problems are alleviated in HEMT 200, of the invention, illustrated in Figure 2, below, /;:~:::~~,:,rn-~::.,.~ .. ~.1,,,,,,,. ·····rl',',,,···· ·:'~,~.".; ... , _·~,,.·,,,.~,-i-~5: i i '::...: :~:."!~~~;",,'i[)' ~3~N 13'.~:f~'!'r L~y,::~ .,.,:;;;.;.;~"'!- :::;!\:t' } !······ ............................ ~~~ ........................... . ~~:,{~r vf G$!t~ i i ;,::".:: ~'8i:.~~{Svi::.v r):~N ·~:&.x ::.~'.'. ... X , \ : . i~~ . I I ~~~:·%$ ,: ........ ~~ .. , .... u~~ ........ ~~ ..................................... , ... l .Y. : :.:::,-s~: l'-.1h'f.'~:..b):: ;..s~·i:}; t ! ............... -................................................... v ----~~:~: ................................... - ......................................................................... J : A~.(,s,,.,.;l'l i>>'<'> <:>,x<,,M,o ,~;,s,:· l ! .................................. ~~~· ........ ········· ... ..J / ... ::N fK~; t.~;h':i ;""""""'"·'""'"·"""~''\ ............................ ! s; f~~~&:..c,-,.t~ j li.~ ' ' ......................................................................... \ {Figure 2 shows HEMT 200 according to the invention} by introducing "crystal adaptation layer" 210 below second breakdown voltage layer 208 and above AlyGa(l-y)N thermal expansion layer 212. (Id. at 3 [0010].) Crystal adaptation layer 210 is doped with a carbon concentration ("C210") that is substantially less than the carbon concentration doping ("C2os") of second breakdown voltage layer 208, but at about the same carbon concentration ("C204'') of first breakdown voltage layer 204. (Id.) Crucially, crystal adaptation layer 210 is configured to lattice-match second 4 Appeal 2017-011047 Application 13/755,058 breakdown voltage layer 208. (Id.) In the words of the Specification, using a Si substrate 216 with a <111> crystal orientation "spawn[s] <0001> c-plane orientations along interfaces of the buffer layer 214 of AlN, the thermal expansion layer 212 of AlyGa(l-y)N, the crystal adaptation layer 210, the first breakdown voltage layer 204 of GaN, and the second breakdown voltage layer 208 of GaN." (Id. at 4 [0013].) As a result, (Id.) the crystal adaptation layer 210 comprising GaN with a lattice constant of approximately 0.57 nm is essentially equal to lattice constants of the first breakdown voltage layer 204 and second breakdown voltage layer 208, making it possible to epitaxially grow almost an arbitrarily thick first breakdown voltage layer 204 and second breakdown voltage layer 208 without loss of crystal quality due strain effects of substantially different lattice constants. The Specification explains that "[ t ]he channel bi-layer of GaN obtains a high breakdown voltage without impacting performance of the HEMT, specifically the Idsat and Ron, and achieves approximately 2x to 4x less defect density than some prior art approaches." (Id. at 12 [0043].) Independent claim 9 is representative and reads: A high electron mobility transistor (HEMT) [200], compnsmg: an active layer [202]; a first breakdown voltage layer [204] which directly contacts a lower portion of the active layer [202] at a heterojunction and comprises a first resistivity value, wherein the first breakdown voltage layer exhibits a first lattice-constant and is doped with carbon at a first non-zero doping concentration [C204]; 5 Appeal 2017-011047 Application 13/755,058 a second breakdown voltage layer [208] disposed beneath the first breakdown voltage layer [204] and comprising a second resistivity value that is greater than the first resistivity value, wherein the second breakdown voltage layer exhibits a second lattice-constant that is substantially equal to the first lattice-constant and is doped with carbon at a second doping concentration [C2os] that is greater than the first doping concentration [C204]; and a crystal adaptation layer [210] disposed beneath the second breakdown voltage layer [208], wherein the crystal adaptation layer exhibits a third lattice-constant which is substantially equal to each of the first and second lattice-constants; and wherein the crystal adaptation layer is doped with carbon at a third doping concentration [ C210] that is approximately equal to the first doping concentration [C204]. (Claims App., Br. 14; some indentation, paragraphing, emphasis. and bracketed labels to figure 2 added.) Appealed claim 40 depends from claim 9 7 and requires direct contact between second breakdown layer [208] and first breakdown voltage layer [204] on the top, and crystal adaptation layer [210] on the bottom. (Id. at 17.) Appealed independent claim 35 (id. at 16-17) recites, from the bottom up, all layers shown in Figure 2 and adds source, drain, and gate regions 7 It may be noted that claim 9 does not recite lower layers 212-216, or the source, drain, and gate-related structures of a transistor. Claim 10 depends from claim 9 and does recite the lower structures. (Id.) Independent claim 14 is drawn to a transistor, and is similar to claim 9, but does not recite that the transistor is an HEMT. (Id. at 15.) 6 Appeal 2017-011047 Application 13/755,058 (illustrated in Figure 3P (not reproduced here)). Appealed claim 38 depends from claim 35 and parallels appealed claim 40. (Id. at 17 .) The Examiner maintains the following grounds of rejection 8, 9, 10, 11 : A. Claims 9, 11, 13-16, and 40 stand rejected under 35 U.S.C. § I03(a) in view of the combined teachings of Harris 12 and Hashimoto. 13 Al. Claims 10 and 35, 36, 37, 38, and 39 stand rejected under 35 U.S.C. § I03(a) in view of the combined teachings of Harris, Hashimoto, and Hwang. 14 A2. Claims 17 and 18 stand rejected under 35 U.S.C. § I03(a) in view of the combined teachings of Harris, Hashimoto, and Cao. 15 8 Examiner's Answer mailed 7 June 2017 ("Ans."). 9 Because this application was filed before the 16 March 2013, effective date of the America Invents Act, we refer to the pre-AIA version of the statute. 10 A rejection of claims 36 and 37 as indefinite under 35 U.S.C. § 112(2) has been withdrawn. 11 Appealed claims are highlighted in bold font. 12 Christopher Harris et al., Method of manufacturing an adaptive AlGaN buffer layer, U.S. Patent Application Publication 2006/0281238 Al (2006). 13 Shin Hashimoto et al., High electron mobility transistor, field-effect transistor, epitaxial substrate, method of manufacturing epitaxial substrate, and method of manufacturing Group III nitride transistor, U.S. Patent Application Publication 2009/0189190 Al (2009). 14 Injun Hwang et al., 1.6 kV, 2.9 mQ normally-off p-GaN HEMT device, Proc. 2012 24th Int'l Symposium on Power Semiconductor Devices and ICs, 3-7 June 2012, Bruges, Belgium. 15 Jianjun Cao et al., Via structure of a semiconductor device and method for fabricating the same, U.S. Patent Application Publication 2011/0248283 Al (2011). 7 Appeal 2017-011047 Application 13/755,058 B. Discussion The Board's findings of fact throughout this Opinion are supported by a preponderance of the evidence of record. In Liu's words, "[r ]eversal of the rejections of claims 35, 38, and 40 is respectfully requested." (Br. 5, § IV.) Liu does not present any arguments for patentability of the remaining claims. We therefore affirm, summarily, the rejections of claims 9--11, 13-18, 36, 37, and 39. The Federal Circuit has explained that on appeal, the appellant must not only show the existence of error, but also that the error was harmful because it affected the decision below. In re Chapman, 595 F.3d 1330, 1338 (Fed. Cir. 2010) ("the burden of showing that an error is harmful normally falls upon the party attacking the agency's determination."), quoting Shinseki v. Sanders, 556 U.S. 396, 409 (2009). The Examiner finds that Harris describes, in Figure 7, below, l.£4.P {Harris Figure 7 shows a sketch of an HEMT ( annotations following the Examiner's findings added)} 8 Appeal 2017-011047 Application 13/755,058 an HEMT comprising a second breakdown voltage layer ( 420b and 420c) having a high second resistivity due to high carbon doping, and a second lattice constant (FR 4, 11. 3-9, citing Harris [0056], [0061], and [0066]), and a crystal adaptation layer 420a having a third carbon doping level less than the second doping level and a third lattice constant substantially equal to the second lattice constant (id. at 11. 9-16, citing Harris [0050], [0057]-[0059], and [0066].) In the Examiner's words, "Harris appears not to explicitly disclose that the device layer includes an active layer; and a first breakdown voltage layer [ meeting the resistivity and lattice limitations] ... and that the second breakdown voltage layer is disposed beneath the first breakdown voltage layer." (Id. at 5, 1st para.) The Examiner finds that Hashimoto describes, in Figure 1, below 11 23 21 {Hashimoto Figure 1 shows a diagram of an HEMT ( annotations added)} HEMT 11 with high carbon doping (Nc1 2: 4 x 1017 cm-3), high resistivity GaN buffer layer 15, GaN channel layer 17 with low carbon doping 9 Appeal 2017-011047 Application 13/755,058 (Nc2 :S 4 x 1016 cm-3), and overlying AlGaN active layer 19 contacting channel layer 17 and forming 2DEG 27. (FR 5, 2d para.) The Examiner concludes that "it would have been obvious ... to have used the AlGaN/GaN active/channel heterojunction and channel and buffer layer carbon doping concentrations as in Hashimoto for its art recognized suitability in an HEMT to provide a high quality channel and high resistivity sub-layers." (Id., 3d para.) Liu urges the Examiner "does not clearly identify which features of Hashimoto constitute the recited 'first breakdown voltage layer' and 'active layer' in claim 40" (Br. 7, 11. 13-15, bold emphasis omitted), and "proceed[ s] by assuming GaN buffer layer 15 (?) is being interpreted as the 'first breakdown voltage layer' of claim 40, and AlGaN active layer 19 is being interpreted as the 'active layer' of claim 40" (id. at sentence bridging 7-8). Based on this interpretation, Liu argues that, "Hashimoto's GaN buffer layer 15 (alleged first breakdown voltage layer) would have to be placed in direct contact with Harris' s layer 420c ( alleged second breakdown voltage layer)." (Id. at 8, 11. 4--7, bold emphasis omitted.) On the present record, we cannot say that Liu's assumption that the Examiner interpreted GaN buffer layer 15 as the first breakdown voltage layer recited in claim 40 is justifiable. Although the '058 Specification, Harris, and Hashimoto use slightly different terminologies, each makes clear that the 2DEG is formed in the GaN layer that forms a heterojunction with an overlying AlGaN layer. Hashimoto refers to this layer, which is layer 17, as the "channel layer." The Examiner recognized this function of Hashimoto' s layer 17, finding that Hashimoto discloses "an overlying 10 Appeal 2017-011047 Application 13/755,058 AlGaN layer contacting and forming a 2DEG (para. 0063 & 0069) in a GaN channel layer 17 with a carbon doping concentration of less than 4 x 1016 cm-3." (FR 5, 11. 11-12.) As we found in the introduction, supra, sentence bridging 2-3, the '058 Specification refers to this layer as the "first voltage breakdown layer" or as the "channel layer" (Spec. 2 [0008]). Consistently, Harris, referring to Figure 1 (not reproduced here), teaches that "[a]s charge transfers from AlGaN layer 50 to GaN layer 40 because of the difference in bandgap between the materials, electron gas 60 comprised of a planar region of high-charge, high mobility electrons is formed in GaN layer 40 at the interface between AlGaN layer 50 and GaN layer 40." All of Liu' s subsequent arguments 16 are based on this mistaken characterization of the Examiner's interpretation of what is the "first breakdown layer," i.e., the channel layer that contains the 2DEG of the HEMT. It follows that these arguments cannot suffice to demonstrate harmful error in the appealed rejections. Returning to Liu's initial criticism that the detailed basis of the rejection was insufficiently clear, we cannot say that the rather detailed findings presented by the Examiner in the Final Rejection (FR 4--5) were insufficient to apprise Liu of the basis and rationale of the rejection. While 16 Part c (Br. 9: Hashimoto's GaN buffer layer 15, even if interpreted as a "first breakdown voltage layer", is not in direct contact with an active layer). Part d[first] (Br. 9-10: the interpretation would frustrate a primary purpose of Harris or render Harris inoperable for its intended purpose). Part d[second] (Br. 11-12: direct contact limitations required by claim 35 are not met by Harris and Hashimoto, and Hwang does not cure these deficiencies). 11 Appeal 2017-011047 Application 13/755,058 we would encourage the Examiner, in any Office Action, to be more explicit about exactly which structures from one reference are to be combined with exactly what structures in a second or other reference, we cannot say that on the facts of this case, that the rejection was insufficiently clear. In this regard, we observe that an interview after the Final Rejection was conducted on 14 November 2016. Thus, Liu had the opportunity to raise issues and to seek clarification relating to all aspects of the rejection at that time. While we cannot determine from the interview summaries provided by the Examiner (Examiner's Interview Summary, mailed 23 November 2017) or by Appellant's representative (Interview Summary filed 27 December 2016) whether Liu's interpretation of the rejection was discussed, it is clear that if it was discussed, there was no meeting of minds. We observe further that the interpretation of the rejection presented in the Brief by Liu was expressed in Liu's Pre-Appeal Request for Review, which was filed on 21 November 2016. Moreover, Liu has not favored us with a Reply Brief, in which any further clarification of Liu's position might have been presented. We conclude that Liu has failed to demonstrate harmful error in the appealed rejections. We therefore affirm. 12 Appeal 2017-011047 Application 13/755,058 C. Order It is ORDERED that the rejection of claims 9--11, 13-18, 35--40 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). AFFIRMED 13 Copy with citationCopy as parenthetical citation