Ex Parte Langdo et alDownload PDFPatent Trial and Appeal BoardJan 17, 201411073780 (P.T.A.B. Jan. 17, 2014) Copy Citation UNITED STATES PATENT AND TRADEMARK OFFICE ____________________ BEFORE THE PATENT TRIAL AND APPEAL BOARD ____________________ Ex parte THOMAS A. LANGDO, MATTHEW T. CURRIE, RICHARD HAMMOND, ANTHONY J. LOCHTEFELD, and EUGENE A. FITZGERALD ____________________ Appeal 2011-006333 Application 11/073,780 Technology Center 2800 ____________________ Before CHUNG K. PAK, PETER F. KRATZ, and CATHERINE Q. TIMM, Administrative Patent Judges. TIMM, Administrative Patent Judge. DECISION ON REQUEST FOR REHEARING Appellants request rehearing of our Decision of October 31, 2013. In conformance with MPEP §1214.01(II), Appellants submit the Request in two papers, which we will refer to as Request (I) and Request (II). Request (I) requests rehearing of our decision to sustain the rejection of claims 61, Appeal 2011-006333 Application 11/073,780 2 64, and 66 under 35 U.S.C § 103(a) as obvious over Chu1 in view of Kakizaki.2 Request (II) requests rehearing of the new ground of rejections we entered with respect to claims 92, 93, and 110. We address both papers in this Decision as a single Request for Rehearing. A. Request I: The Rejection over Chu in view of Kakizaki With respect to the rejection of claims 61, 64, and 66 under 35 U.S.C. § 103(a) over Chu in view of Kakizaki, Appellants contend we misapprehended or overlooked the requirements of claim 61 in sustaining the rejection (Req. Reh’g I at 2). Claim 61 reads as follows: 61. A method for forming a structure, the method comprising: providing a first substrate having a first strained semiconductor layer formed thereon; performing a step to increase a bond strength between the first strained semiconductor layer and an insulator layer disposed on a second substrate and to which the first strained semiconductor is subsequently bonded; after performing the step to increase the bond strength, bonding the first strained semiconductor layer to the insulator layer disposed on the second substrate; and removing the first substrate from the first strained semiconductor layer, the first strained semiconductor layer remaining bonded to the insulator layer, wherein bonding comprises achieving a bond strength greater than or equal to about 1000 milliJoules/meter squared (mJ/m2) at a temperature less than approximately 600 °C. 1 Chu et al., US 6,649,492 B2, issued Nov. 18, 2003. 2 Kakizaki et al., US 6,326,279 B1, issued Dec. 4, 2001. Appeal 2011-006333 Application 11/073,780 3 (Claims App’x at Br. A2 (emphasis added).) According to Appellants, we did not address Appellants’ argument that neither Chu nor Kakizaki teaches or suggests the requirement of the last clause of claim 61 (Req. Reh’g I at 2, citing Br. 43-44, and further directing our attention to Br. 41). We disagree. We addressed this argument in Section G of the Decision (Decision 13-14). Appellants contend that bonding that achieves the recited bond strength is not taught by the references (Req. Reh’g I at 2). We agree with Appellants that neither Chu nor Kakizaki expressly teaches the level of bonding required by the last clause of claim 61. However, such an express teaching is not required. The obviousness analysis “need not seek out precise teachings directed to the specific subject matter of the challenged claim, for a court [or this Board] can take account of the inferences and creative steps that a person of ordinary skill in the art would employ.” KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 418 (2007). “If a person of ordinary skill can implement a predictable variation, § 103 likely bars its patentability.” Id. at 417. As pointed out by Appellants, both Chu and Kakizaki seek to perform bonding (Req. Reh’g I at 2). Moreover, bond strength was a known parameter sought to be increased: As we pointed out, “[t]he Examiner relies upon Kakizaki for a teaching of increasing bond strength by exposing an insulating layer to be bonded to a nitrogen plasma or oxygen plasma to activate its surface (Ans. 9; see also Kakizaki, col. 7, ll. 33-37 and col. 15, ll. 24-27).” (Decision 13.) Therefore, there was a reason within the art to apply the plasma treatment step of Kakizaki to increase bond strength of Appeal 2011-006333 Application 11/073,780 4 Chu’s bond. Consistent with the teachings of Kakizaki, “Appellants' own Specification provides evidence that nitrogen plasma and oxygen plasma activation increases bond strength between silicon-based layers,” as we stated in our Decision, Id. This is not disputed by Appellants (Req. Reh’g I). Given that there was a reason within the art to increase bond strength by adopting a plasma treatment that is the same or similar to the plasma treatment Appellants themselves disclose will result in the claimed bond strength, it is reasonable to conclude that a bond strength within the claimed range would result in the process suggested by Chu in combination with Kakizaki. When a claimed property value necessarily flows from the conventional practice of the prior art, an express teaching of the property value is not required in order to support a conclusion of obviousness. See In re Kubin, 561 F.3d 1351, 1357 (Fed. Cir. 2009) (Prior art need not explicitly discuss a property that is necessarily present in the thing formed when following the process of the prior art); Perricone v. Medicis Pharmaceutical Corp., 432 F.3d 1368, 1378 (Fed. Cir. 2005) (“If Pereira discloses the very same methods, then the particular benefits must naturally flow from those methods even if not recognized as benefits at the time of Pereira's disclosure.”). It is knowledge within the art of the use of plasma treatment to increase bond strength that forms the foundation of the rejection. The result, i.e., the bond strength obtained, follows from that knowledge. Plasma treatment was known to result in increased bond strength and it appears reasonable that bond strengths within the claimed range would have been predictable and expected. “The combination of familiar elements Appeal 2011-006333 Application 11/073,780 5 according to known methods is likely to be obvious when it does no more than yield predictable results.” KSR, 550 U.S. at 416. Appellants have not convinced us that we overlooked or misapprehended the requirements of claim 61 in sustaining the Examiner’s rejection of claims 61, 64, and 66 as obvious over Chu in view of Kakizaki. B. Request II: New Grounds of Rejection In our Decision, we reversed the Examiner’s decision to reject claim 92 as anticipated by Chu, but affirmed the Examiner’s decision to reject claims 93 and 110 as obvious over Chu (Decision 3-7). Because claims 93 and 110 depend from claim 92, we held that broader claim 92 was rendered obvious based on the grounds of rejection applied against claims 93 and 110 (Decision 6-7). Because the Examiner did not list claim 92 as rejected as obvious over Chu, we denominated our affirmance with regard to claim 92 a new ground of rejection (id.). In our Decision, we also determined that the Examiner made a faulty finding in rejecting claims 92 and 93 as anticipated by Godbey3 (Decision 7). We, however, found that Godbey supported a finding of anticipation on different grounds (Decision 8). Therefore, we affirmed the Examiner’s rejection of claims 92 and 93, but denominated our affirmance as involving a new ground of rejection (id.). The Examiner further rejected claim 110 as obvious over Godbey (Ans. 6). We determined that Godbey anticipated claim 110 and, therefore, entered a new ground of anticipation by Godbey with respect to claim 110 (Decision 8). 3 Godbey et al., US 5,013,681, issued May 7, 1991. Appeal 2011-006333 Application 11/073,780 6 With respect to the new grounds of rejection of claims 92, 93, and 110 as obvious over Chu and claims 92, 93, and 110 as anticipated by Godbey, Appellants contend that we did not establish that the strained layer of either of these references has an initial misfit dislocation density capable of being reduced (Req. Reh’g II at 2). Because Appellants’ arguments are confined to limitations found in claim 92, we select that claim as representative for deciding the issue on rehearing. Claim 92, with the limitations of particular interest highlighted reads as follows: 92. A method for forming a structure, the method comprising: providing a first substrate having a dielectric layer disposed thereon; forming a semiconductor layer on a second substrate, the semiconductor layer having an initial misfit dislocation density; bonding the semiconductor layer to the dielectric layer; removing the second substrate, the semiconductor layer remaining bonded to the dielectric layer; and reducing the initial misfit dislocation density in the semiconductor layer. (Claims App’x at Br. A4-A5 (emphasis added).) With regard to Chu, there is no dispute that Chu epitaxially deposits a strained layer 100 (Req. Reh’g II at 2; see also Decision 4; Br. 20-21). Or that “[s]train occurs because the relatively high Ge concentration layer 140, upon which layer 100 is deposited or grown, has larger lattice spacing than Appeal 2011-006333 Application 11/073,780 7 the Si based layer 100.” (Decision 4-5, citing Br. 20-21; Chu, col. 6, ll. 33- 40 and Vossen,4 cited by Appellants at Br. 20.) According to Appellants, a strained layer may be defect-free (Req. Reh’g II at 2-3). Appellants cite a passage of Vossen, a reference supplied in the Evidence Appendix of the Appeal Brief, as well as a statement in Chu in support of an argument that Chu does not expressly or inherently teach that layer 100 has an initial misfit dislocation density capable of being reduced in a subsequent step (Req. Reh’g II at 3). The passage of Chu referred to by Appellants is found in a discussion of the Background of the Invention relating to carrier mobility in the semiconductor raw material used in device fabrication (Chu, col. 1, ll. 16- 48). According to Chu, there is great difficulty in keeping carrier mobility high in devices with small submicron transistors (Chu, col. 1, ll. 28-30). Chu states that A promising avenue toward better carrier mobility is to modify slightly the semiconductor that serves as raw material for device fabrication. It has been known, and recently further studied, that tensilely strained Si has intriguing carrier properties. A Si layer embedded in a Si/SiGe heterostructure grown by UHV-CVD has demonstrated enhanced transport properties, namely carrier mobilities, over bulk Si. In particular, a 90-95% improvement in the electron mobility has been achieved in a strain Si channel n-MOS (Metal Oxide Semiconductor transistor, a name with historic connotations for Si Field- Effect-Transistors (FET)) in comparison to a bulk Si n-MOS mobility. Similarly, a 30-35% improvements in the hole carrier mobility has been obtained for a strained Si channel p-MOS, in comparison to bulk silicon p- MOS. The great difficulty lies in the production of a layer of tensilely strained Si, or SiGe, that are of high enough 4 John L. Vossen & Werner Kern, THIN FILM PROCESSES II. 370-442 (Academic Press Inc. 1991). Appeal 2011-006333 Application 11/073,780 8 crystalline quality, namely free of dislocations and other defects, to satisfy the exceedingly elevated demands of microelectronics. (Chu, col. 1, ll. 30-48 (emphasis added).) Chu conveys that it is difficult to produce strained layers that are free of dislocations and other defects. Vossen, in discussing pseudomorphic growth states that: The growth of defect-free, generally lattice-mismatched materials can take place only at specific compositions at which the lattice parameter matches the substrate. There is an intermediate growth regime for lattice-mismatched materials in which defect-free, but highly strained thin layers of material can be grown on a substrate [201, 202]. This growth mode is often referred to as pseudomorphic growth and is schematically shown in Fig. 11. (Vossen, p. 413, ll. 5-11 (emphasis added).) The caption for Figure 11 states that Pseudomorphic growth of strained layer structures results in a tetragonal distortion of the growing layer. Thick layers of lattice-mismatched materials relax to their bulk lattice parameter with the generation of extended defects. (Fig. 11 caption.) Vossen then describes the heteroepitaxial growth process, explaining that distortion builds up a strain in the material as the layer is grown with a large amount of energy stored in the structure (Vossen, p. 413, ll. 11-21). According to Vossen, The amount of energy stored in the structure eventually exceeds a critical value required for the creation of strain-relieving defects such as dislocations [201,202]. It is therefore possible to grow highly mismatched materials, without extended defects, to a limited thickness as shown in Fig. 11. The exact maximum Appeal 2011-006333 Application 11/073,780 9 thickness prior to the formation of extended defects, commonly referred to as the critical thickness, is materials-specific. Defect generation proceeds through a nucleation, propagation, and multiplication process. These processes are generally temperature-dependent, as well as being dependent on the material combination and, perhaps, the interfacial structure. There have been several theoretical predictions for the critical thickness as a function of strain or lattice mismatch. The initial pioneering work of Matthews and Blakeslee serves as a good working estimate of this critical thickness [201,202]. This estimate is based on an energy balance between the strain energy in the pseudomorphic structure and the energy associated with the formation of the requisite number of misfit dislocations. Other theoretical estimates are based on the inclusion of dislocation nucleation effects or the consideration of the interfacial stresses. The exact value of the critical thickness allowable in a particular layered structure still requires experimental verification. (Vossen, p. 413, l. 21 to p. 414, l. 18 (emphasis added).) Even though Vossen uses the term “defect-free” in the initial discussion, in the context of the further discussion, and given the disclosure in Chu that it is difficult to produce strained layers without defects, it is reasonable to conclude that the strained layer one of ordinary skill in the art would form when following the process of Chu would have some defects and hence an initial misfit dislocation density. Appellants cite to no evidence indicating that Chu’s etching process would not reduce defect density in the same or similar manner as Appellants etching process reduces such defects. In other words, there is no convincing evidence that the initial defect density of Chu’s strained layer would not be capable of being reduced. With respect to Godbey, Appellants contend that “[n]othing in Godbey expressly teaches a misfit dislocation density in layer 24.” (Req. Appeal 2011-006333 Application 11/073,780 10 Reh’g II at 3.) Again, Appellants state that a strained layer may be defect- free (id.). However, the evidence cited above indicates that forming defect- free strained layers is difficult and it is reasonable to conclude that some misfit defects would result when forming the strained layer 24 of Godbey. The subject Request has been granted to the extent that the Decision has been reconsidered, but denied with respect to making any changes therein. DENIED cdc Copy with citationCopy as parenthetical citation