DETAILED ACTION
Claims 1-7, 13-15, 17-18, 23-24, 26-28, 43, 45 and 51 are pending before the Office for review.
In the response filed October 23, 2025:
Claims 1-2 were amended.
No new matter is present.
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claims 1, 5-7 and 43 are rejected under 35 U.S.C. 103 as being unpatentable over HIROOKA et al (U.S. Patent Application Publication 2016/0218003) in view of MIKAMI et al (Reduction of Fluoride Species and Surface Roughness by H2Gas addition in SiC Dry Etching) and PALMOUR (U.S. Patent 4,981,551).
With regards to claim 1, Hirooka discloses a method of preparing a silicon carbide wafer for subsequent epitaxial growth thereon (Paragraph [0008]), the method comprising: proving a silicon carbide wafer unmasked, flowing an etch gas mixture wherein the etch gas mixture comprises molecular hydrogen, H2; generating a plasma from the etch gas mixture and using the plasma to etch the unmasked surface of the wafer so as to reduce the roughness of the unmasked surface (Paragraphs [0062]-[0073], [0097] discloses providing a silicon carbide substrate without a mask, subjecting the substrate with hidden scratches to a gas phase etching including a plasma etching using reactive gas including a fluorine containing gas or hydrogen gas; wherein the etching removes hidden scratches and removal of the hidden scratches reduces the surface roughness.)
Hirooka does not explicitly disclose a plasma processing chamber containing a silicon carbide wafer mounted on a support table; establishing a flow of an etch gas mixture comprising a noble gas into the plasma processing chamber and generating a plasma from the etch gas mixture within the plasma processing chamber .
Mikami discloses a method of preparing a silicon carbide wafer wherein a silicon carbide sample is placed in an ICP chamber to anisotropic plasma etching the surface; the surface is etched with an etching gas comprising hydrogen in a plasma processing chamber; wherein the gas is generated into a plasma; wherein the addition of hydrogen to the processing gas increases the etching rate and lowers the surface roughness of the etched area (Page 1 Introduction, Pages 2-3 Surface morphology and etching property, Page 4 Summary) which renders obvious a plasma processing chamber containing a silicon carbide wafer mounted on a support table; establishing a flow of an etch gas mixture into the plasma processing chamber and generating a plasma from the etch gas mixture within the plasma processing chamber .
It would have been prima facie obvious to one of ordinary skill in the art prior to the effective filing date of the invention to modify the method of Hirooka to include the reduction of surface roughness of Mikami because the reference of Mikami teaches that reduction in the surface roughness provide for an improvement in the device performance (Page 4 Summary) and one of ordinary skill in the art prior to the effective filing date of the invention would have had a reasonable expectation of predictably achieving the desired etching using the reduced surface roughness as rendered obvious by Mikami. MPEP 2143D
Palmour discloses a method of dry etching a silicon carbide target comprising a plasma comprising a fluorine containing etchant and dilutant gas comprising helium and argon (Col. 4 line 25-Col. 5 line 9) rendering obvious wherein the etch gas mixture further comprises a noble gas.
It would have been prima facie obvious to one of ordinary skill in the art prior to the effective filing date of the invention to further modify the modified method of Hirooka to include the dilutant gas of Hirooka because one of ordinary skill in the art prior to the effective filing date of the invention would have had a reasonable expectation of predictably achieving the desired etching using the noble gas as rendered obvious by Palmour. MPEP 2143D
With regards to claim 5, the modified teachings of Hirooka discloses wherein the etch gas mixture further comprises one or more fluorine bearing gases each configured to release fluorine radicals when in the plasma (Hirooka Paragraph [0072],Mikami Pages 1-2).
With regards to claim 6, the modified teachings of Hirooka discloses wherein the etching gas comprises a fluorine containing as such as SF6, hydrogen and oxygen (Pages 1-2) wherein the hydrogen was added in sufficient amounts to the SF6 gas to reduce the surface roughness (Mikami Pages 2-3). Generally, differences in concentration or temperature will not support the patentability of subject matter encompassed by the prior art unless there is evidence indicating such concentration or temperature is critical. "[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation." In re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955). MPEP 2144.05(II)(A) Therefore it would have been prima facie obvious to one of ordinary skill in the art prior to the effective filing date of the invention to optimize the ratio of H2 to the fluorine bearing gas in the etch gas mixture to amounts including applicant’s claimed amount of 100:1 to 51 in order provide the hydrogen gas at amounts sufficient to the SF6 gas to reduce the surface roughness as taught by the modified teachings of Hirooka (Mikami Pages 2-3, MPEP 2144.05(II)(A)).
With regards to claim 7, the modified teachings of Hirooka discloses wherein the etching gas comprises a fluorine containing as such as SF6, hydrogen and oxygen (Mikami Pages 1-2) wherein the hydrogen was added in sufficient amounts to reduce the surface roughness when etching in a fluorine composition (Mikami Pages 2-3). Generally, differences in concentration or temperature will not support the patentability of subject matter encompassed by the prior art unless there is evidence indicating such concentration or temperature is critical. "[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation." In re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955). MPEP 2144.05(II)(A) Therefore it would have been prima facie obvious to one of ordinary skill in the art prior to the effective filing date of the invention to optimize the concentration of hydrogen to amounts including at least 20% in order provide the hydrogen gas at amounts sufficient to reduce the surface roughness as taught by the modified teachings of Hirooka (Mikami Pages 2-3, MPEP 2144.05(II)(A)).
With regards to claim 43, the modified teachings of Hirooka renders obvious wherein the wafer is oriented such that the unmasked surface is a silicon face (Hirooka Paragraphs [0062]).
Claims 23-24 and 26-28 are rejected under 35 U.S.C. 103 as being unpatentable over HIROOKA et al (U.S. Patent Application Publication 2016/0218003) in view of ZHANG et al (CN 106816372 as evidenced by the machine translation).
With regards to claim 23, Hirooka discloses a method of preparing a silicon carbide wafer for subsequent epitaxial growth thereon (Paragraph [0008]), the method comprising: proving a silicon carbide wafer unmasked, flowing an etch gas mixture; generating a plasma from the etch gas mixture and using the plasma to etch the unmasked surface of the wafer so as to reduce the roughness of the unmasked surface (Paragraphs [0062]-[0073], [0097] discloses providing a silicon carbide substrate without a mask, subjecting the substrate with hidden scratches to a gas phase etching including a plasma etching using reactive gas including a fluorine containing gas or hydrogen gas; wherein the etching removes hidden scratches and removal of the hidden scratches reduces the surface roughness.)
Hirooka does not explicitly disclose a plasma processing chamber containing a silicon carbide wafer mounted on a support table; establishing a flow of an etch gas mixture into the plasma processing chamber, wherein the etch gas mixture comprises at least hydrogen bromide, HBr and oxygen, O2; and (c) generating a plasma from the etch gas mixture within the plasma processing chamber.
Zhang discloses an method of etching a silicon carbide wafer comprising proving a SiC substrate in an etching apparatus for generating a plasma comprising placing a substrate into a chamber and using an etching gas including a fluorine containing gas, oxygen gas and hydrogen bromide wherein the etching provides a smooth etched surface (Pages 2, 4) which renders obvious a plasma processing chamber containing a silicon carbide wafer mounted on a support table; establishing a flow of an etch gas mixture into the plasma processing chamber, wherein the etch gas mixture comprises at least hydrogen bromide, HBr and oxygen, O2; and (c) generating a plasma from the etch gas mixture within the plasma processing chamber.
It would have been prima facie obvious to one of ordinary skill in the art prior to the effective filing date of the invention to modify the method of Hirooka to include the etching gas of Zhang because the reference of Zhang teaches that such etching composition has the ability to provide a reliable etch (Page 4) and one of ordinary skill in the art prior to the effective filing date of the invention would have had a reasonable expectation of predictably achieving the desired etching using the etching gas and smooth surface as rendered obvious by Zhang. MPEP 2143D
With regards to claim 24, the modified teachings of Hirooka renders obvious wherein 60-80% of the comprising consist of HBr (Zhang Page 2) which renders obvious at least 40% of the etch gas mixture consists of HBr. In the case where the claimed ranges "overlap or lie inside ranges disclosed by the prior art" a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976). MPEP 2144.05(I)
With regards to claim 26, the modified teachings of Hirooka renders obvious wherein the etch gas mixture further comprises one or more halogen-bearing gases that do not comprise bromine (Hirooka Paragraphs p0072], Zhang Page 2 discloses SF6).
With regards to claim 27, the modified teachings of Hirooka renders obvious wherein the one or more halogen-bearing gases comprise one or more fluorine-bearing gases each configured to release fluorine radicals when in the plasma, wherein preferably each fluorine-bearing gas is one of sulphur hexafluoride, SF6 and carbon tetrafluoride CF4 (Hirooka Paragraph [0072] Zhang Pages 2, 4)
With regards to claim 28, the modified teachings of Hirooka discloses wherein the etching gas comprises HBr, oxygen and a fluorine containing gas wherein the HBr gas comprises 80% and the remaining oxygen and fluorine are provided at a 1:1 ration (Zhang Pages 4-5) rendering obvious wherein the ratio of HBr to the fluorine bearing gas in the etch gas mixture is in the range of 100:1 to 2:1. In the case where the claimed ranges "overlap or lie inside ranges disclosed by the prior art" a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976). MPEP 2144.05(I)
Allowable Subject Matter
Claims 2-4, 45 and 51 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
Claims 13-15 and 17-18 are allowed.
Response to Arguments
Applicant’s arguments, see 7-13 of Applicant’s response, filed October 23, 2025, with respect to 2-4, 13-15 and 17-18 have been fully considered and are persuasive. In particular, Applicant’s claimed amendment and arguments have overcome the rejection of record. The 103 rejection of claims 2-4, 13-15 and 17-18 has been withdrawn.
Applicant's remaining arguments filed October 23, 2025 have been fully considered but they are not persuasive.
Applicant argues on pages 7-13 of Applicant’s response that the cited prior art fails to teach or render obvious a gas mixture comprising molecular hydrogen, H2, and a noble gas a requires by amended claim 1. Applicant argues that Hirooka in view of Mikami fail to teach Applicant’s claimed limitation and Palmour fails to cure the deficiencies. Applicant argues that Palmour is provided for dry etching SiC to form “mesa-type structures’ using an NF3 as an etchant. Applicant argues that Palmour is intended for forming a deice structure and that differs from Hirooka which is concerned with etching an unmasked wafer. In addition Palmour specifically contrasts NF3 with other “conventional gases.” Therefore one of ordinary skill would not look towards Palmour for modifying the reference of Hirooka. In addition Mikami does not remedy the deficiencies of Palmour and Hirooka.
With regards to claim 23, Applicant argues that Hirooka fails to teach or render obvious Applicant’s claimed etch gas mixture. Zhang fails to cure these deficiencies as Zhang is directed toward s etching through a mask which differs from Hirooka. Applicant argues that Zhang is directed towards etching through a mask and therefore one of ordinary skill in the art prior to the effective filing date of the invention would not have been motivated to look at the teachings of Zhang. It is Applicant’s position that Hirooka does not seek to perform a patterned etch and does not use any mask. As to the dependent claims they are rejected as no separate arguments have been provided. This is found unpersuasive.
It is the Examiner’s position that Zhang as modified by Mikami and Palmour render obvious Applicant’s claimed invention including an etch gas mixture comprising molecular hydrogen and a carrier gas including a noble gas such as argon. It is the Examiner position that Hirooka discloses a gas phase etching using a fluorine containing gas (Paragraph [0072]). While Hirooka provides examples of fluorine containing gases, it is not limited towards those examples. Disclosed examples and preferred embodiments do not constitute a teaching away from a broader disclosure or nonpreferred embodiments. In re Susi, 440 F.2d 442, 169 USPQ 423 (CCPA 1971). MPEP 2123(II) Therefore one of ordinary skill in the art would be motivated to look for suitable etching gases for etching silicon carbide including the reference of Mikami and Palmour. As such the Examiner maintains that Zhang as modified by Mikami and Palmour render obvious Applicant currently amended claim 1.
With regards to claims 23, it is the Examiner’s position that Hirooka as modified by Zhang renders obvious Applicant’s claimed invention. It is Applicant’s position that Hirooka discloses a method of etching a silicon carbide surface, Zhang discloses a suitable composition for etching a silicon carbide surface. The selection of a known material based on its suitability for its intended use supported a prima facie obviousness determination in Sinclair & Carroll Co. v. Interchemical Corp., 325 U.S. 327, 65 USPQ 297 (1945) MPEP 2144.07 It is the Examiner’s position that the composition of Zhang would be suitable for etching the same material of silicon carbide as present in the reference of Hirooka. As such the Examiner maintains the rejection of claim 23. As to the dependent claims they remain rejected as no separate arguments have been provided.
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to STEPHANIE P. DUCLAIR whose telephone number is (571)270-5502. The examiner can normally be reached 9-6:30 M-F.
Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice.
If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Joshua Allen can be reached at 571-270-3176. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/STEPHANIE P DUCLAIR/Primary Examiner, Art Unit 1713