DETAILED ACTION
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
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claim(s) 11,12, 21 and 22 is/are rejected under 35 U.S.C. 103 as being unpatentable over Watanabe (US 2015/0275394) in view of Kitabatake (US 6,214,107), Kordina et al (US 6,297,522) and Hiyoshi (US 2016/0086799).
Watanabe teaches a method of forming a 3C-SiC film 3 on a monocrystalline silicon substrate 2 comprising rapidly heating the silicon substrate from room temperature to a growth temperature T1 to limit epitaxial growth to only the monocrystalline silicon, wherein in the process of rapid heating, and then rapidly heating to a temperature T2 higher than T1 while introducing carbon gas onto to the silicon substrate to grow cubic silicon carbide, wherein a carbon source gas carbonizes the surface of the silicon substrate and forms a cubic silicon carbide film ([0048]-[0075]), which clearly suggests step of adhering carbon on a surface of a silicon single-crystal substrate by an RTA treatment of the silicon single-crystal substrate in a carbon-containing gas atmosphere; a step of forming a 3C-SiC single-crystal film on the surface of the silicon single-crystal substrate by reacting the carbon and the silicon single-crystal substrate. Watanabe also teaches a carbon source gas is preferably a hydrocarbon gas, such as methane (CH4), ethane (C2H6), or propane (C3H8), and these may be used either alone or as a mixture of two or more ([0056]). Watanabe et al also teaches a film thickness of less than 7 nm (Fig 9; [0100]-[0101]). It is noted that applicant’s response filed 11/26/2025 states that the RTA condition is not particularly limited as long as the condition can adhere the carbon 2 on the surface of the silicon single crystal substrate (See page 5 of the remarks); therefore, the carbonization taught by Watanabe et al meets the claimed limitation regarding RTA because carbon is adhered and SiC is formed.
Watanabe et al teaches rapidly heating to a temperature T2 higher than T1 while introducing carbon gas onto to the silicon substrate to grow cubic silicon carbide, wherein a carbon source gas carbonizes the surface of the silicon substrate and forms a cubic silicon carbide film, however does not explicitly teach a temperature of 1150 to 1300°C.
In a method of forming silicon carbide, Kitabatake teaches a Si substrate 31, forming a thin film 34 containing carbon at a temperature below 600°C to form a carbon film; then the Si substrate is heated in a second step, wherein carbonization of the Si substrate 32 and formation of a SiC thin film 35; and a carbon has a thickness of 1 atomic layer to 20 atomic layers (col 8, ln 1-67), which would overlap the claimed thickness of 7 nm or less. Kitabatake also teaches heating the Si substrate to 800-1414°C to carbonize in a second step (col 8, ln 1-67, col 20, ln 1-67, col 21, ln 1-67).
It would have been obvious to one of ordinary skill in the art at the time of filing to modify Watanabe by optimizing the temperature and thickness to obtain the claimed ranges to form a uniform thin film containing carbon on the surface that is stable, as taught by Kitabatake (col 8, ln 1-67).
The combination of Watanabe et al and Kitabatake does not teach the Ar+H2.
In a method of making silicon carbide layers, Kordina et al teaches a carrier gas is a blend formed of hydrogen and argon, and the presence of argon moderates the thermal conductivity of the carrier gas which in turn moderates the rate at which the source gases deplete as they move through the reactor (col 3, ln 25-67).
It would have been obvious to one of ordinary skill in the art at the time of filing to modify the combination of Watanabe et al and Kitabatake by using a blend of Ar+H2 as a carrier gas, as taught by Kordina et al, to moderate the rate at which the source gases deplete as they move through the reactor and because combining equivalents known for the same purpose is prima facie obvious (MPEP 2144.06 I).
In regards to the thickness of the SiC film having a thickness of 7 nm or less, Watanabe et al also teaches a film thickness of less than 7 nm (Fig 9; [0100]-[0101]). Also, Kitabatake teaches a carbon layer has a thickness of 1 atomic layer to 20 atomic layers and annealing to form SiC, as applicant; therefore, the formed SiC layer would be expected to overlap the claimed thickness of 7 nm or less and heating the Si substrate to 800-1414°C to carbonize (Kitabatake col 8, ln 1-67). Overlapping ranges are prima facie obvious (MPEP 2144.05).
The combination of Watanabe, Kitabatake and Kordina et al does not teach a step of oxidizing the 3C-SiC single-crystal film to be an oxide film and diffusing carbon inward the silicon single-crystal substrate by an RTA treatment of the silicon single-crystal substrate on which the 3C-SiC single-crystal film is formed, the RTA treatment being performed in an oxidative atmosphere; and a step of removing the oxide film.
In a method of producing a SiC substrate, Hiyoshi teaches a substrate 10, forming an first SiC epitaxial SiC layer on the substrate; and introducing carbon into the first epitaxial layer by thermal oxidation under an oxygen atmosphere at 1100°C to 1300°C for about 5 minutes to 24 hours; and an oxide film produced by the oxidation of SiC may be removed by etching ([0078]-[0105]), which meets the definition of RTA, as defined by applicant, as discussed above.
It would have been obvious to one of ordinary skill in the art at the time of filing to modify the combination of Watanabe, Kitabatake and Kordina et al by forming an oxide and removing the oxide, as taught by Hiyoshi, to reduce Z1/2 centers (Hiyoshi [0005]-[0015]).
Referring to claim 12, the combination of Watanabe, Kitabatake, Kordina et al and Hiyoshi teaches a Si substrate 31, forming a thin film 34 containing carbon at a temperature below 600°C to form a carbon film; then the Si substrate is heated in a second step, wherein carbonization of the Si substrate 32 and formation of a SiC thin film 35; and a carbon has a thickness of 1 atomic layer to 20 atomic layers (Kitabatake col 8, ln 1-67).
Referring to claim 21, the combination of Watanabe, Kitabatake, Kordina et al and Hiyoshi teaches repeatedly forming the epitaxial layer and repeating the carbon diffusion process (Hiyoshi Fig 2-3).
Referring to claim 22, the combination of Watanabe, Kitabatake, Kordina et al and Hiyoshi teaches forming an epitaxial SiC layer on the Si substrate.
Claim(s) 15, 16 and 19-20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Watanabe (US 2015/0275394) in view of Kitabatake (US 6,214,107), Kordina et al (US 6,297,522) and Hiyoshi (US 2016/0086799), as applied to claim 11, 12, 21 and 22 above, and further in view Tanimoto (JP 2006-074024), an English computer translation (CT) is provided.
The combination of Watanabe, Kitabatake, Kordina et al and Hiyoshi teaches all of the limitation of claims 15 and 16, as discussed above, except the combination of Watanabe and Hiyoshi does not teach in the step of oxidizing the 3C-SiC single-crystal film to be the oxide film and diffusing carbon inward the silicon single-crystal substrate, the RTA treatment is performed in the oxygen atmosphere at 1150°C to 1400°C for 1 to 60 seconds.
In a method of making SiC, Tanimoto teaches a SiC substrate, and thermally oxidizing the substrate in an oxygen atmosphere to grow a sacrificial thermal oxide film with a thickness of less than 50 nm at a temperature of greater than 1100°C and lower than 1350°C, and then the sacrificial oxide immediately removed (CT [0014], [0054], [0066]). Tanimoto also teaches forming the silicon oxide film and then heat treating the surface in an inert atmosphere (such as N or Ar) within the same oxidation temperature range for 1 minute to 180 minutes (CT [0066]). Tanimoto also teaches removing an oxide film using a buffered hydrofluoric acid solution for 5 to 10 seconds, and then the buffered hydrofluoric acid solution is completely rinsed off with ultrapure water and dried (CT [0021], [0026], [0039]). Tanimoto also teaches the oxide film can be removed using well known wet or dry etching (CT [0054]).
It would have been obvious to one of ordinary skill in the art at the time of filing to modify the combination of Watanabe, Kitabatake, Kordina et al and Hiyoshi by annealing at 1100°C-1350°C for 1-60 seconds, to grow an oxide layer having a desired thickness using suitable temperatures, as evidenced by Tanimoto. In regards to RTA, the combination of Watanabe and Hiyoshi teaches rapid heating, and also forming oxide layers less than 50 nm which would be expected to occur rapidly under the same processing temperature, as taught by applicant.
Referring to claim 19, the combination of Watanabe, Kitabatake, Kordina et al, Hiyoshi and Tanimoto teaches the oxide film can be removed using well known wet or dry etching (CT [0054]), removing an oxide film using a buffered hydrofluoric acid solution for 5 to 10 seconds, and then the buffered hydrofluoric acid solution is completely rinsed off with ultrapure water and dried (CT [0021], [0026], [0039]), and forming the silicon oxide film and then heat treating the surface in an inert atmosphere (such as N or Ar) within the same oxidation temperature range for 1 minute to 180 minutes (CT [0066]). Overlapping ranges are prima facie obvious (MPEP 2144.05). The combination of Watanabe, Kitabatake, Kordina et al, Hiyoshi and Tanimoto does not teach the oxide film is etched by an RTA treatment in a hydrogen atmosphere at 1150°C to 1400°C for 1 to 60 seconds. It would have been obvious to one of ordinary skill in the art at the time of filing to modify the combination of Watanabe, Kitabatake, Kordina et al, Hiyoshi and Tanimoto by etching the oxide oxide film is etched by an RTA treatment in a hydrogen atmosphere at 1150°C to 1400°C for 1 to 60 seconds to remove the oxide film rapidly.
Referring to claim 20, the combination of Watanabe, Kitabatake, Kordina et al, Hiyoshi and Tanimoto teaches the oxide film can be removed using well known wet or dry etching (CT [0054]), removing an oxide film using a buffered hydrofluoric acid solution for 5 to 10 seconds, and then the buffered hydrofluoric acid solution is completely rinsed off with ultrapure water and dried (CT [0021], [0026], [0039]), and forming the silicon oxide film and then heat treating the surface in an inert atmosphere (such as N or Ar) within the same oxidation temperature range for 1 minute to 180 minutes (CT [0066]). It would have been obvious to one of ordinary skill in the art at the time of filing to modify the combination of Watanabe, Kitabatake, Kordina et al, Hiyoshi and Tanimoto is performed with 0.1 to 5.0% hydrofluoric acid, an aqueous HF solution, for shorter than 10 minutes, and then rinsing is performed with pure water because optimization of concentration and time through routine experimentation would have been obvious to one of ordinary skill in the art at the time of filing. (MPEP 2144.05).
Response to Arguments
Applicant’s arguments with respect to claim(s) 11, 12, 15, 16, 19-22 have been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument.
Applicant's arguments filed 11/26/2025 have been fully considered but they are not persuasive.
In response to applicant's argument that the references fail to show certain features of the invention, it is noted that the features upon which applicant relies (i.e., a carbon diffusion layer can be formed on the surface of the silicon substrate, which as a high concentration of carbon, much higher than the solid solubility of carbon) are not recited in the rejected claim(s). Although the claims are interpreted in light of the specification, limitations from the specification are not read into the claims. See In re Van Geuns, 988 F.2d 1181, 26 USPQ2d 1057 (Fed. Cir. 1993).
In response to applicant's arguments against the references individually, one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986). Applicant’s argument that if source gases contain silicone raw materials such as silane as in Hiyoshi it is not possible to form a 3C-SiC single crystal film having a high concentration of carbon is noted but not found persuasive. Hiyoshi is not relied upon to teach carbonization and 3C-silicon carbide formation. Hiyoshi is merely relied upon to teach forming an oxide layer to diffuse carbon. Watanabe teaches forming a 3C-cubic silicon carbide film by carbonizing the substrate and then rapidly heating without supplying a silicon gas raw materials to form the silicon carbide film ([0050]-[0061], [0100]-[0101]).
In response to applicant's arguments against the references individually, one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986). Applicant’s argument that Watanabe teaches a first step was set between 800 and 1000°C is noted but not found persuasive. Kitabatake teaches heating the Si substrate to 800-1414°C to carbonize in a second step (col 8, ln 1-67, col 20, ln 1-67, col 21, ln 1-67). The examiner maintains Watanabe merely teaches a preferred embodiment with a temperature range of 800-1000°C, and is not limited to this range. Watanabe broadly teaches the silicon substrate 2 is rapidly heated to the epitaxial growth temperature T2 of cubic silicon carbide higher than the epitaxial growth temperature T1 of monocrystalline silicon while introducing a carbon source gas (carbon-containing gas) onto the silicon substrate 2 ([0055]). The examiner maintains that one of ordinary skill in the art knows that temperature is a result effective variable and a carbonization temperature of 800-1414°C is known in the art, as evidenced by Kitabatake; therefore, it would have been obvious to one of ordinary skill in the art at the time of filing through routine experimentation and optimization. It is noted that US 2004/0053438 teaches 3C-SiC epitaxial CVD growth at 800-1200°C ([0041]).
Applicant’s argument that Kitabataka teaches the thickness of the carbon layer not the 3C-SiC layer is noted but not found persuasive. First, Watanabe teaches a layer thickness of less than 7 nm (Fig 9); therefore, the claimed thickness is not novel and would have been obvious to one of ordinary skill in the art at the time of filing. Second, the examiner maintains that Kitabataka teaches a carbon layer thickness is only 1 atomic layer, which would react with the silicon to produce 1 atomic layer of SiC, which would be less than 7nm. Kawana (JP 2017-095305) teaches the thickness of the carbonized buffer layer 3 may be at least one atomic layer, for example, a thickness of 2 nm or more and 30 nm or less.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure.
Shimizu (US 2016/0087043) teaches a thermally-oxidized film 20 is then formed on the SiC substrate 10 through thermal oxidation in an oxidizing atmosphere at 1200°C to 1500°C, and when the thermally-oxidized film 20 is formed, interstitial carbon diffuses into the SiC substrate 10, and enters carbon vacancies in the SiC substrate 10 ([0040]-[0050].
Koga (JP 2016-063198), an English computer translation (CT) is provided, teaches a silicon wafer was subjected to a carbonization treatment under the following conditions: supplying a carbonaceous gas, such as methane (CH4), propane gas (C3H8) or ethane (C2H6), and a hydrogen carrier gas were introduced into the heat treatment furnace, and the silicon wafer was carbonized in a carbon atmosphere at a temperature of 1000 to 1300°C for 1 to 60 minutes with an explicit example of supplying propane gas at 1200° C. for 3 minutes; and the surface layer of the silicon wafer became a β-type single crystal SiC layer (CT [0053]-[0060], [0075]). Overlapping ranges are prima facie obvious (MPEP 2144.05).
Kawana (JP 2017-095305), an English computer translation (CT) is provided, teaches a carbonization buffer layer 3 is formed on a silicon substrate 2, and a first silicon carbide layer 5 is formed on the carbonization buffer layer 3, wherein the thickness of the carbonized buffer layer 3 may be at least one atomic layer, for example, a thickness of 2 nm or more and 30 nm or less (CT [0038]-[0039]).
Abe et al (US 2004/0053438) teaches a raw material gas containing the gas having carbon element and the gas having silicon element is applied on a Si substrate, thereby a 3C-SiC single crystal film is synthesized on the Si substrate, wherein, the deposition temperature at this time is in the range of 800 to 1200°C ([0037]-[0041], [0071]-[0072]).
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). 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 MATTHEW J SONG whose telephone number is (571)272-1468. The examiner can normally be reached Monday-Friday 10AM-6PM.
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MATTHEW J. SONG
Examiner
Art Unit 1714
/MATTHEW J SONG/ Primary Examiner, Art Unit 1714