Ex Parte Chua et alDownload PDFBoard of Patent Appeals and InterferencesApr 23, 200810430499 (B.P.A.I. Apr. 23, 2008) Copy Citation UNITED STATES PATENT AND TRADEMARK OFFICE ____________________ BEFORE THE BOARD OF PATENT APPEALS AND INTERFERENCES ____________________ Ex parte LAY-LAY CHUA, YANG YANG, and CHUN-TING LIU ____________________ Appeal 2007-4445 Application 10/430,499 Technology Center 2800 ____________________ Decided: April 23, 2008 ____________________ Before CHUNG K. PAK, ROMULO H. DELMENDO, and LINDA M. GAUDETTE, Administrative Patent Judges. DELMENDO, Administrative Patent Judge. DECISION ON APPEAL STATEMENT OF THE CASE Appellants appeal under 35 U.S.C. § 134(a) from a final rejection of all pending claims (claims 1-11, 21-29). (Final Office Action entered December 8, 2005). We have jurisdiction under 35 U.S.C. § 6(b). We AFFIRM. Appeal 2007-4445 Application 10/430,499 Appellants’ invention relates to a method of manufacturing bipolar transistors having compound semiconductors. (Spec. ¶ 0001). According to Appellants, “[t]he method includes depositing a compound semiconductor layer over a semiconductor substrate and forming a patterned metal layer on the compound semiconductor layer.” (Spec. ¶ 0006). Using the metal layer as an etch mask, the compound semiconductor layer is dry etched so the etched perimeter of the compound semiconductor layer is “substantially coextensive” with the perimeter of the metal layer. (Spec. ¶ 0014). Representative claims 1, 2, 6, 7, 24, and 27 read as follows: 1. A method of manufacturing a bipolar transistor, comprising: depositing a compound semiconductor layer over a semiconductor substrate; forming a patterned metal layer on said compound semiconductor; and performing a dry etch of said compound semiconductor layer in a manner that uses said metal layer to align said dry etch, wherein said dry etch causes a perimeter of said compound semiconductor layer to be substantially coextensive with a perimeter of said metal layer. 2. The method as recited in Claim 1, wherein performing said dry etch causes an undercut of said compound semiconductor layer to vary by less than ±20 percent on all sides of said perimeter. 6. The method as recited in Claim 1, wherein said dry etching includes an etchant gas comprising chlorine and boron. 7. The method as recited in Claim 6, wherein said etchant gas further includes boron trichloride gas provided at between about 0.1 sccm and about 50 sccm. 24. The method as recited in Claim 1, wherein said dry etching includes etching said compound semiconductor along a [001] lattice direction at a first rate and etching said compound semiconductor along a 2 Appeal 2007-4445 Application 10/430,499 [011] lattice directions [sic] at a second rate, a ratio of said first rate to said second rate being in a range of about 0.8:1 to about 1.2:1. 27. The method as recited in Claim 2, wherein said undercut is greater than about 0.01 microns and less than about 0.03 microns. The prior art references relied upon by the Examiner to reject the claims on appeal are: Bayraktaroglu US 5,648,294 Jul. 15, 1997 Hamm US 6,165,859 Dec. 26, 2000 Hwang US 6,265,318 B1 Jul. 24, 2001 Pullela US 6,645,819 B2 Nov. 11, 2003 Akagi US 4,739,379 Apr. 19, 1988 The following rejections are before us for review: Claims 1, 3, 6 and 8-11 are rejected under 35 U.S.C. § 102(b) as anticipated by Bayraktaroglu. Claims 2, 7, 24, and 27 are rejected under 35 U.S.C. § 103(a) as unpatentable over Bayraktaroglu. Claims 4 and 5 are rejected under 35 U.S.C. § 103(a) as unpatentable over Bayraktaroglu in view of Hamm. Claims 21-23 are rejected under 35 U.S.C. § 103(a) as unpatentable over Bayraktaroglu in view of Hwang. Claims 25 and 26 are rejected under 35 U.S.C. § 103(a) as unpatentable over Bayraktaroglu in view of Pullela. Claims 28 and 29 are rejected under 35 U.S.C. § 103(a) as unpatentable over Bayraktaroglu in view of Akagi. 3 Appeal 2007-4445 Application 10/430,499 ISSUES Have Appellants shown error in the Examiner’s determination that Bayraktaroglu anticipates the subject matter of claims 1, 3, 6, and 8-11? Have Appellants shown the Examiner erred in determining claims 2, 4, 5, 7, and 21-29 would have been obvious to one of ordinary skill in the art over the applied prior art? FINDINGS OF FACT 1. Appellants’ Specification establishes that “substantially coextensive” means “a maximum uniform undercut on all sides of the compound semiconductor 105, and the respective sides of the patterned metal layer 115, following dry etching.” (Spec. ¶ 0015; Figures 1A-1E). 2. The Specification explains that the term “uniform,” with respect to an undercut, means “varying by less than ±20 percent on all sides of the perimeter” of the compound semiconductor. (Id. ¶ 0019). 3. The “substantially coextensive” limitation of the claims therefore requires an undercut on all sides of the perimeter of the compound semiconductor that varies by less than ±20 percent. (Id. ¶ 0015, 0019). 4. The Specification explains that “dry etching comprises exposing the compound semiconductor 105 and the patterned metal layer 115 to an etching plasma.” (Id. ¶ 0016; Figures 1A-1E). 5. The Specification states that “[t]he compound semiconductor 105 comprises Group IIA and IVA or Group IIIA and VA elements from the Periodic Table of the Elements (Groups 2 and 4 or Groups 3 and 5 of the IUPAC convention).” (Id. ¶ 0014). 4 Appeal 2007-4445 Application 10/430,499 6. The Specification states “the compound semiconductor 105 is dry etched in a manner in which the metal layer 115 functions as an etch mask.” (Id. ¶ 0014; Figures 1A-1E). 7. The Specification discloses “[t]he metal layers 115, 135 can comprise any metal commonly used in the semiconductor industry, such as gold, titanium, platinum, palladium or composite layers thereof.” (Id. ¶ 0021; Figures 1A-1E). 8. The Specification states that the etching is performed with an etchant gas and that the etchant gas desirably includes “chemical components [that] are dissociated into free radicals that interact with and etch the compound semiconductor,” with boron trichloride being the more preferred chemical component of the etchant gas. (Id. ¶ 0018). 9. While the Specification describes use of inert gases to provide a physical component of etchant gases that have a “desirable feature” of giving an etch rate “substantially independent of the orientation of the crystal comprising the compound semiconductor,” Appellants do not identify any portion of the Specification stating that this “desirable feature” is an absolute requirement for achieving the substantially coextensive characteristic of the final product; furthermore, Appellants do not identify any portion of the Specification stating that the chemical component of the etchant gases alone does not provide a physical component as well. (Id. ¶ 0017-0018). 10. The Specification indicates to one skilled in the relevant art that suitable etching conditions within the scope of the invention, with respect to pressure, temperature, and power, are not particularly limited: 5 Appeal 2007-4445 Application 10/430,499 In preferred embodiments, dry etching comprises exposing the compound semiconductor 105 and the patterned metal layer 115 to an etching plasma. In one embodiment, the conditions for dry etching via inductively coupled plasma reactive ion etch (ICP RIE) includes a bias power of between about 1 Watt and about 100 Watts and a source power of between about 20 Watts and about 2000 Watts and pressure of about 0.1 to about 20 mTorr. More preferably, the ICP RIE conditions include a power of between about 5 Watts and about 100 Watts and a source power of between about 100 Watts and about 1000 Watts. Preferably, dry etching is performed in a temperature range of between about 25°C and about 300°C, and more preferably between about 150°C and about 300°C. One skilled in the art would understand that the above-described conditions for dry etching are machine-dependent, and therefore vary such conditions according to the particular characteristics of the instrument used for dry etching. (Id. ¶ 0016). 11. Bayraktaroglu describes a preferred embodiment using a compound semiconductor made of Al0.3Ga0.7As and GaAs, (col. 4, ll. 3-4); where Al (Aluminum), Ga (Gallium), and As (Arsenide) are elements from Groups IIIA and VA of the Periodic Table of Elements. 12. Appellants’ disclosed materials used for the compound semiconductor in the inventive method encompass the compound semiconductor materials used in the prior art. (Spec. ¶ 0014; Bayraktaroglu, col. 4, ll. 3-4). 13. Bayraktaroglu discloses plasma etching with BCl3 (boron trichloride), where the etching conditions are such that the etching is conducted “generally anisotropically.” (Col. 4, ll. 56-61). 14. Bayraktaroglu teaches “the BCl3 etch could include diluents” (i.e., inert etching components). (Col. 8, l. 1). 6 Appeal 2007-4445 Application 10/430,499 15. Bayraktaroglu teaches the metal emitter contact 142 masks portions of the compound semiconductor when etching with BCl3 to form emitter 140 and emitter cap 141. (Col. 4, ll. 53-57; Figures 2a, 3a-3c). 16. Bayraktaroglu teaches “an overetch allows a controlled undercut of emitter contact 142 so that emitter contact 142 has an overhang of about 0.05 to 0.1 µm.” (Col. 4, ll. 64-67; Figures 2a, 3a-3c). PRINCIPLES OF LAW “To anticipate a claim, a prior art reference must disclose every limitation of the claimed invention, either explicitly or inherently.” In re Schreiber, 128 F.3d 1473, 1477 (Fed. Cir. 1997). “A reference includes an inherent characteristic if that characteristic is the ‘natural result’ flowing from the reference's explicitly explicated limitations.” Eli Lilly and Co. v. Barr Laboratories, Inc., 251 F.3d 955, 970 (Fed. Cir. 2001) (citing Continental Can Co. USA, Inc. v. Monsanto Co., 948 F.2d 1264, 1269 (Fed. Cir. 1991)). ANALYSIS Appellants have defined “substantially coextensive” in their Specification as “a maximum uniform undercut on all sides of the compound semiconductor 105, and the respective sides of the patterned metal layer 115, following dry etching.” (FF 1). Furthermore, the Specification explains that an undercut is “uniform” when the compound semiconductor has a perimeter varying by less than ±20 percent on all sides. (FF 2). From these definitions, it is clear that the “substantially coextensive” limitation of the claims requires an undercut on all sides of the compound semiconductor that 7 Appeal 2007-4445 Application 10/430,499 varies by less than ±20 percent. (FF 3). In re Morris, 127 F.3d 1048, 1054 (Fed. Cir. 1997) (“[I]t would be unreasonable for the PTO to ignore any interpretive guidance afforded by the applicant’s written description . . . .”); In re Zletz, 893 F.2d 319, 321 (Fed. Cir. 1989) (“When the applicant states the meaning that the claim terms are intended to have, the claims are examined with that meaning . . . .”). Claims 1, 3, 6, and 8-11. Appellants argue claims 1, 3, 6, and 8-11 together. Accordingly, we select claim 1 as representative and confine our discussion to this claim. 37 C.F.R. § 41.37(c)(vii) (2005). Appellants do not contest the Examiner’s finding that Bayraktaroglu discloses the steps recited in claim 1 for manufacturing a bipolar transistor by: 1) depositing a compound semiconductor layer over a semiconductor substrate; 2) forming a patterned metal layer on said compound semiconductor; and 3) performing a dry etch of said compound semiconductor layer in a manner that uses said metal layer to align said dry etch. (App. Br. 8-13; Reply Br. 2-4). Rather, Appellants argue that Bayraktaroglu cannot anticipate claim 1 because the reference does not describe “a dry etch that causes a perimeter of a compound semiconductor layer to be substantially coextensive with a perimeter of a metal layer, as recited in Claim 1.” (App. Br. 9). Though recognizing that Bayraktaroglu discloses an undercut of 0.05-0.1 microns, Appellants argue that there is no suggestion in the reference that the undercut is “uniform” because the Examiner has not provided a basis for assuming Bayraktaroglu’s dry etch method results in a “uniform” undercut. (App. Br. 10, ll. 11-17). 8 Appeal 2007-4445 Application 10/430,499 We cannot agree with Appellants. Bayraktaroglu teaches plasma etching a compound semiconductor made of elements from Group IIIA and VA of the Periodic Table of the Elements, (FF 11), using BCl3 (boron trichloride) in an etching gas, (FF 13), that may include diluents (i.e., inert components), (FF 14), under conditions that are generally anisotropic. (FF 13). Bayraktaroglu further teaches a metal emitter contact 142 masks portions of the compound semiconductor, (FF 15), to obtain a controlled undercut of the metal mask, forming an overhang of 0.05 - 0.1 microns. (FF 16). In a strikingly similar fashion, Appellants’ Specification describes the same etching method (dry etching) (FF 4), using the same boron trichloride in an etchant gas, (FF 8), and employing a metal layer to serve as an etching mask. (FF 6, 7). The Specification encompasses more than just the disclosed embodiments to achieve the claimed invention. The Specification does describe an example to achieve uniform etching by “exposing a compound semiconductor made of InP to BC13 and N2 gases supplied at about 5 and 15 sccm . . . [where t]he gases are supplied at a pressure of about 2 mTorr and temperature of about 200°C, using bias and source powers of about 10 Watts and about 500 Watts, respectively.” (Spec. ¶ 0019). However, other parts of the disclosure indicate that a suitable range of materials include elements selected from Groups IIIA and VA of the Periodic Table of Elements (FF 5). These suitable materials encompass the semiconductor materials used in the prior art. (FF 12). Also, while the Specification discloses that etchant gases provide physical and chemical components for etching (FF 8-9), we have not been directed to any evidence that the physical component is required to achieve the “substantially coextensive” characteristic of the final product, or 9 Appeal 2007-4445 Application 10/430,499 that the characteristic results only when inert gases are used. (FF 9). In any event, Bayraktaroglu teaches the use of inert diluents, as in Appellants’ disclosure of the preferred embodiments. (FF 14). Furthermore, while stating that the preferred etching conditions may vary depending on the particular etching machine used, Appellants have not established that the etching conditions that achieve the “substantially coextensive” characteristic of the etched product are limited in any way. (FF 10). To the contrary, Appellants’ Specification impresses one skilled in the relevant art that dry etching compound semiconductor materials chosen from Groups IIIA and VA using a preferred etchant such as boron trichloride, under etching conditions similar to Appellants’ preferred disclosed conditions, would inherently or necessarily provide etching that is “substantially coextensive” as recited in appealed claim 1. Under these circumstances, the burden was properly shifted to Appellants to prove that the prior art method would not result in a “substantially coextensive” structure. In re Best, 562 F.2d 1252, 1255 (CCPA 1977) (“Where, as here, the claimed and prior art products are identical or substantially identical, or are produced by identical or substantially identical processes, the PTO can require an applicant to prove that the prior art products do not necessarily or inherently possess the characteristics of his claimed product.”). In re Preda, 401 F.2d 825, 826 (CCPA 1968) (“[I]n considering the disclosure of a reference, it is proper to take into account not only specific teachings of the reference but also the inferences which one skilled in the art would reasonably be expected to draw therefrom.”). Appellants failed to meet their burden. 10 Appeal 2007-4445 Application 10/430,499 Moreover, Appellants broadly define “substantially coextensive” to include up to ±20 percent perimeter variations on all sides of the semiconductor, (FF 3), and have not relied on any evidence that the prior art’s similar dry etching method would result in a perimeter with over 20 percent variation. Instead, Appellants have relied on arguments that the prior art does not disclose the “substantially coextensive” characteristic. (App. Br. 9 - 10). These arguments do not satisfy Appellants’ burden to show the Examiner erred in finding a prima facie case of anticipation. In re Pearson, 494 F.2d 1399, 1405 (CCPA 1974) (“Attorney’s argument in a brief cannot take the place of evidence.”). For these reasons, we uphold the Examiner’s rejection on this ground. Claims 2, 4, 5, 7, and 21-29. In discussing the Examiner’s rejections of claims 2, 4, 5, 7, and 21-29, Appellants rely on similar arguments presented with respect to claim 1, above, and submit separate arguments for claims 2 and 24. We address these arguments accordingly. Appellants do not argue the Examiner’s combination of Bayraktaroglu with the other references, but rather they contend that Bayraktaroglu does not establish a prima facie case of obviousness of dependent claims 2, 7, 24, and 27 because these claims, like claim 1, require “a dry etch that causes a perimeter of a compound semiconductor layer to be substantially coextensive with a perimeter of a metal layer.” (App. Br. 11, ll. 8-13). With this argument, Appellants rely on the same reasoning as set forth above regarding claim 1. 11 Appeal 2007-4445 Application 10/430,499 As discussed above, we find Appellants’ argument with respect to the “substantially coextensive” limitation unpersuasive. Appellants failed to direct us to sufficient evidence showing “substantially coextensive” perimeters do not necessarily result when following the method taught by Bayraktaroglu. Indeed, Appellants have produced no evidence to indicate that an etched product that is made by uncontrolled and non-uniform (i.e., more than ±20% perimeter variation on all sides) etching would even have been considered in the art to be useful. Also, with respect to claim 2, Appellants argue that Bayraktaroglu does not suggest an undercut that “varies by less than ±20 percent on all sides of the perimeter [of] the compound semiconductor layer.” (App. Br. 11, ll. 14-16). Again, this argument is not persuasive. This limitation is subsumed in the “substantially coextensive” limitation of claim 1 because “substantially coextensive” requires an undercut of the compound semiconductor’s perimeter that varies by less than ±20% on all sides. (FF 3). For the same reasons as discussed above, Appellants have not met their burden to show the Examiner erred in determining claim 2 to be obvious to one of ordinary skill in the art. With respect to claim 24, Appellants additionally argue that Bayraktaroglu does not teach the required ratio of a first etching rate to a second etching rate because the reference is concerned with relative vertical etching rates, which are irrelevant to the required features of substantially coextensive perimeters and relative etch rates in lateral directions. (App. Br. 11 bridging to 12). Again, Appellants have not satisfied their burden to show that the Examiner erred in the obviousness determination. To begin with, 12 Appeal 2007-4445 Application 10/430,499 Bayraktaroglu would necessarily be concerned with etching in a transverse direction because the reference teaches a controlled undercut. (FF 16). Furthermore, the Examiner found the ratio of a first etching rate along a first direction and a second etching rate along a second direction to be a result effective variable that one of ordinary skill in the art would modify by routine optimization. (Ans. 9 bridging to 10). Appellants’ bare arguments that Bayraktaroglu does not teach the limitations found in the claim are not sufficient to overcome the Examiner’s finding. Here, Appellants have not even asserted that the Examiner’s finding that the ratio is a result effective variable is in error. (App. Br. 11-13; Reply Br. 3-4). With respect to the grounds of rejection for claims 4, 5, 21-23, 25, 26, 28, and 29, Appellants rely on the same arguments as discussed above with respect to claims 2, 7, 24, and 27. These arguments are unpersuasive to show that the Examiner made reversible error in finding claims 4, 5, 21-23, 25, 26, 28, and 29 obvious to one of ordinary skill in the art, for the reasons discussed above. CONCLUSION Appellants have failed to show that the Examiner reversibly erred in determining that Bayraktaroglu anticipates claims 1, 3, 6, and 8-11. Also, Appellants have not shown that the Examiner erred in determining that one of ordinary skill in the art would have found the subject matter of claims 2, 4, 5, 7, and 21-29 obvious over the prior art. Therefore, we affirm the decision of the Examiner to reject appealed claims 1-11 and 21-29. 13 Appeal 2007-4445 Application 10/430,499 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 tf/ls HITT GAINES, PC ALCATEL-LUCENT P.O. BOX 832570 RICHARDSON, TX 75083 14 Copy with citationCopy as parenthetical citation