DETAILED ACTION
This Office Action is in response to RCE filed October 29, 2025.
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Objections
Claim 1 is objected to because of the following informalities: “the SiC substrate side” should be replaced with “a SiC substrate side” on line 5, because (a) Applicants do not claim “a SiC substrate side” before claiming “the SiC substrate side”, and (b) therefore, when strictly interpreted, the limitation “the SiC substrate side” is indefinite due to lack of the antecedent basis. Appropriate correction is required.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claims 6 and 7 are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
(1) Regarding claim 6, it is not clear how many measurements “a plurality of in-plane nitrogen concentration measurements” recited on lines 7-8 refer to, and what the corresponding measurement areas of the “in-plane nitrogen concentration measurements” are, because (a) Applicants do not claim “a plurality of in-plane nitrogen concentration measurements” per se, which would have been broadly interpreted, but rather claim “a minimum in-plane nitrogen concentration measurement value” on lines 8-9 and “a maximum in-plane nitrogen concentration measurement value” on line 9, (b) the minimum in-plane nitrogen concentration measurement value and the maximum in-plane nitrogen concentration measurement value would vary depending on how many measurements are made, especially when the claimed in-plane nitrogen concentrations of the SiC substrate, the first layer, the second layer and the third layer do not appear to be uniform, (c) for example, the claimed in-plane uniformity of the nitrogen concentration when one measures the in-plane nitrogen concentration in a measurement area of 1 µm × 1 µm for 2 or 3 times would likely be different from the claimed in-plane uniformity of the nitrogen concentration when one measures the in-plane nitrogen concentration in a measurement area of 10 µm × 10 µm for 20 or 30 times, (d) for another example, even for the same measurement area, the claimed in-plane uniformity of the nitrogen concentration when one measures the in-plane nitrogen concentrations of 1, 2 and 1 (arbitrary unit) would be different from the claimed in-plane uniformity of the nitrogen concentration when one measures the in-plane nitrogen concentrations of 1, 2, 1 and 2 (arbitrary unit) since the average value are different from each other, while the minimum and maximum are the same, and (e) therefore, even for a single SiC epitaxial wafer structure, the claimed in-plane uniformity of the nitrogen concentration would be different when the number of “a plurality of in-plane nitrogen concentration measurements” varies.
(2) Regarding claim 7, it is not clear whether the limitation recited in claim 7 suggests that any arbitrary portion of the SiC epitaxial wafer at or more than 5 mm away from the edge of the SiC epitaxial wafer can be measured for the claimed nitrogen concentrations, because (a) if this is the case, claim 7 may fail to comply with the written description requirement since Applicants originally disclosed in paragraph [0040] of current application that “For example, a plurality of points are measured in the cross direction with the center of the wafer as the origin”, that “For example, a total of 21 points consisting of 5 points arranged at equal intervals in each of the 4 directions of the cross with the origin as the center are measured”, that “The nitrogen concentration described above is the average of the concentrations measured at each point”, and that “The concentration at each measurement point does not deviate significantly from the mean value, and at least one of the measurement points satisfies the above range of nitrogen concentrations”, and (b) therefore, it appears that the measurement points for the claimed nitrogen concentrations are very specific, while the limitation recited in claim 7 may suggest that any arbitrary portion of the SiC epitaxial wafer at or more than 5 mm away from the edge of the SiC epitaxial wafer can be measured for the claimed nitrogen concentrations.
Claim Rejections - 35 USC § 103
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.
Claims 1-3, 5-7, 9, 11 and 12 are rejected under 35 U.S.C. 103 as being unpatentable over Tawara (US 10,796,906)
Regarding claim 1, Tawara discloses a SiC epitaxial wafer (Fig. 1), comprising: a SiC substrate (1) (col. 5, lines 43-44); and, a SiC epitaxial layer (composite layer of 2-4) (col. 2, lines 13-29) laminated on the SiC substrate, wherein the SiC epitaxial layer comprises a first layer (4) (col. 5, lines 40-41), an n-type second layer (2) (col. 5, lines 51-53) directly on the first layer, and a third layer (3) (col. 6, lines 37-38) directly on the second layer in order from the SiC substrate side, the SiC substrate (1) has a nitrogen concentration of 1 × 1018 cm-3 or higher and 2 × 1019 cm-3 or less (col. 5, lines 45-49), the first layer (4) has a nitrogen concentration of 1.0 × 1017 cm-3 or more and 1.5 × 1018 cm-3 or less (1 × 1017 cm-3 or higher and 1 × 1018 cm-3 or less on lines 53-54 of column 5, and on lines 1-2 and 5-6 of column 6), the n-type second layer (2) has a nitrogen concentration of 1 × 1018 cm-3 to 2 × 1019 cm-3 (col. 6, line 67 - col. 7, line 1) or about 5 × 1018 cm-3 (col. 6, lines 60-64), and the third layer (3) has a nitrogen concentration of 5.0 × 1013 cm-3 or more and less than 1.0 × 1017 cm-3 (about 1 × 1016 cm-3, on lines 10-13 of column 7).
Tawara differs from the claimed invention by not showing that the SiC substrate has a nitrogen concentration of 6.0 × 1018 cm-3 or more and 1.5 × 1019 cm-3 or less, the n-type second layer has a nitrogen concentration of 1.0 × 1018 cm-3 or more and less than 5.0 × 1018 cm-3, and wherein the nitrogen concentration of the n-type second layer is higher than the nitrogen concentration of the first layer, and the nitrogen concentration of the n-type second layer is lower than the nitrogen concentration of the SiC substrate.
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the SiC substrate can have a nitrogen concentration of 6.0 × 1018 cm-3 or more and 1.5 × 1019 cm-3 or less, and the n-type second layer can have a nitrogen concentration of 1.0 × 1018 cm-3 or more and less than 5.0 × 1018 cm-3, because (a) the nitrogen concentrations for the SiC substrate and the n-type second layer disclosed by Tawara each overlaps with the claimed ranges, respectively, (b) even when the nitrogen concentration of the n-type second layer is about 5 × 1018 cm-3 as disclosed by Tawara, the nitrogen concentration of the n-type second layer can be in a range of 1.0 × 1018 cm-3 or more and less than 5.0 × 1018 cm-3 as recited in claim 1 since (i) the combined teachings of the nitrogen concentration of the n-type second layer of 1 × 1018 cm-3 or more and less than 2 × 1019 cm-3 and about 5 × 1018 cm-3 would suggest that “about 5 × 1018 cm-3” can be interpreted to be less than 5 × 1018 cm-3 as well as about 5 × 1018 cm-3, which belongs to a range of a range of 1.0 × 1018 cm-3 or more and less than 5.0 × 1018 cm-3, and (c) the nitrogen concentrations for the SiC substrate and the n-type second layer should be controlled and optimized to obtain a SiC epitaxial wafer suitable for a semiconductor device formed on the SiC epitaxial wafer such as a transistor device.
Furthermore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the nitrogen concentration of the n-type second layer can be higher than the nitrogen concentration of the first layer, and the nitrogen concentration of the n-type second layer can be lower than the nitrogen concentration of the SiC substrate, because (a) the nitrogen concentration of the first layer disclosed by Tawara is 1 × 1017 cm-3 or more and 1 × 1018 cm-3, the nitrogen concentration of the n-type second layer disclosed by Tawara is 1 × 1018 cm-3 or more and less than 2 × 1019 cm-3, which can be 1.0 × 1018 cm-3 or more and less than 5.0 × 1018 cm-3 as recited in claim 1, and therefore, as long as the nitrogen concentration of the first layer is not 1.0 × 1018 cm-3, which is the upper limit of the range disclosed by Tawara or the nitrogen concentration of the n-type second layer is not 1.0 × 1018 cm-3, which is the lower limit of the range disclosed by Tawara, and thus would have been obvious to one of ordinary skill in the art, the claimed relative nitrogen concentrations of the n-type second layer and the first layer would be satisfied, and (b) the nitrogen concentration of the SiC substrate is 1 × 1018 cm-3 or more and 2 × 1019 cm-3 or less according to Tawara, and therefore, the nitrogen concentration of the n-type second layer can be lower than the nitrogen concentration of the SiC substrate when the nitrogen concentration of the n-type second layer is about 5 × 1018 cm-3, while the nitrogen concentration of the SiC substrate is in a range of 5 × 1018 cm-3 or more and 2 × 1019 cm-3 or less, which is a vast majority of the range of 1 × 1018 cm-3 or more and 2 × 1019 cm-3 or less of the nitrogen concentration of the SiC substrate disclosed by Tawara, and thus would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, especially when Tawara does disclose that the nitrogen concentration of the SiC substrate and the nitrogen concentration of the n-type second layer are controlled simultaneously.
Regarding claim 2, Tawara further discloses that a thickness of the n-type second layer (2) is 2.0 µm or more (col. 6, lines 57-59).
Regarding claims 3 and 5, Tawara differs from the claimed invention by not showing that a thickness of the first layer is 0.2 µm or more and 2.0 µm or less (claim 3 and 5).
Tawara further discloses that “Further, the film thickness of the n-type epitaxial layer 4 may be less than 5 μm because when the film thickness is too thick, the resistance increases due to the n-type epitaxial layer 4” on line 65 of column 5 - line 1 of column 6.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that a thickness of the first layer can be 0.2 µm or more and 2.0 µm or less, because (a) as disclosed by Tawara, the thickness of the first layer or n-type epitaxial layer 4 should be controlled and optimized to achieve a desired resistivity and resistance of the claimed SiC epitaxial wafer, and (b) the claims are prima facie obvious without showing that the claimed ranges of the thickness achieve unexpected results relative to the prior art range. In re Woodruff, 16 USPQ2d 1935, 1937 (Fed. Cir. 1990). See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious).
Regarding claim 6, Tawara differs from the claimed invention by not showing that an in-plane uniformity of the nitrogen concentration of the SiC substrate is within 50%, an in-plane uniformity of the nitrogen concentration of the first layer is within 20%, an in-plane uniformity of the nitrogen concentration of the n-type second layer is within 50%, and an in-plane uniformity of the nitrogen concentration of the third layer is within 20%, and wherein, for each of the SiC substrate, the first layer, the n-type second layer, and the third layer, the respective in-plane uniformity is obtained by obtaining a plurality of in-plane nitrogen concentration measurements comprising a minimum in-plane nitrogen concentration measurement value and a maximum in-plane nitrogen concentration measurement value, subtracting the minimum in-plane nitrogen concentration measurement value from the maximum in-plane nitrogen concentration measurement value, and dividing by an average value of the plurality of in-plane nitrogen concentration measurement values.
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the in-plane uniformity of the nitrogen concentrations of the SiC substrate, the first layer, the second layer and the third layer can be respectively within the claimed ranges, because one of ordinary skill in the art has been striving to obtain (substantially) uniform epitaxial layer structures since (substantially) uniform epitaxial layer structures would allow one of ordinary skill in the art to manufacture semiconductor devices on the (substantially) uniform epitaxial layer structures that have (substantially) identical semiconductor device characteristics, which would reduce the manufacturing cost of the semiconductor devices and improve the yield of the semiconductor devices.
Regarding claim 7, Tawara further disclose for the SiC epitaxial wafer according to claim 1 that the respective nitrogen concentrations of the SiC substrate (1), the first layer (4), the n-type second layer (2), and the third layer (3) are based on a nitrogen concentration of any portion of the SiC epitaxial wafer.
Tawara differs from the claimed invention that the any portion of the SiC epitaxial wafer is greater than or equal to 5 mm from an edge of the SiC epitaxial wafer.
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the any portion of the SiC epitaxial wafer can be greater than or equal to 5 mm from an edge of the SiC epitaxial wafer, because this limitation would be satisfied when the SiC substrate has a diameter equal to or greater than 5 mm or approximately 0.2 inches, which would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention since a large diameter SiC substate has been commonly employed since a large diameter SiC substrate would allow one of ordinary skill in the art to manufacture more semiconductor devices on the substrate, which would lower the manufacturing cost of the semiconductor devices.
Regarding claims 9 and 11, Tawara further discloses for the SiC epitaxial wafer according to claim 1 that the nitrogen concentration ofthe first layer (4) is higher than the nitrogen concentration ofthe third layer (3), because the first layer 4 has a nitrogen concentration of 1 × 1017 cm-3 or more and 1 × 1018 cm-3, while the third layer 3 has a nitrogen concentration of about 1 × 1016 cm-3 (claim 9), and the nitrogen concentration of the third layer (3) is 1 × 1016 cm-3 or less, because the third layer 3 has a nitrogen concentration of about 1 × 1016 cm-3 (claim 11).
Regarding claim 12, Tawara differs from the claimed invention by not showing that the n-type second layer has a nitrogen concentration of 1 × 1018 cm-3 or more and 3.7 × 1018 cm-3 or less.
As discussed above, Tawara discloses that the n-type second layer (2) has a nitrogen concentration of 1 × 1018 cm-3 or more and less than 2 × 1019 cm-3 (col. 6, line 67 - col. 7, line 1) or about 5 × 1018 cm-3 (col. 6, lines 60-64).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the n-type second layer can have a nitrogen concentration of 1 × 1018 cm-3 or more and 3.7 × 1018 cm-3 or less, because (a) the nitrogen concentrations for the n-type second layer disclosed by Tawara overlaps with the respective claimed range, (b) the nitrogen concentration for the n-type second layer should be controlled and optimized to obtain a SiC epitaxial wafer suitable for a semiconductor device formed on the SiC epitaxial wafer such as a transistor device, and (c) the claim is prima facie obvious without showing that the claimed range of the nitrogen concentration achieves unexpected results relative to the prior art range. In re Woodruff, 16 USPQ2d 1935, 1937 (Fed. Cir. 1990). See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious).
Response to Arguments
Applicants’ arguments with respect to claim 1 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.
Applicants’ arguments traversing the 35 USC 112(b) rejection of claims 6 and 7 in the REMARKS are not persuasive, because (a) the limitations of claims 6 and 7 are not simply broad, and Applicants did not provide any substantiating evidence that limitations of claims 6 and 7 are just broad, (b) if the enforceability of claim 6 depends on how many measurements were performed, and where and how the measurements were performed, how can claim 6 be broad?, and (c) in addition, Applicants’ arguments traversing the 35 USC 112(b) rejection of claim 7 would be persuasive only when the claimed SiC epitaxial wafer is absolutely and completely isotropic without any surface steps, surface terraces, and surface and bulk defects, which is impossible to achieve in reality, and Applicants cannot simply argue that the claim limitations of claim 7 are broad when Applicants measured the claimed nitrogen concentrations in a certain way, but did not measure the claimed nitrogen concentrations in any other ways; how can Applicants guarantee measurement results of the nitrogen concentrations that Applicants did not measure?
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure.
Fujiwara et al. (US 8,164,100)
Miyazato et al. (US 12,408,416)
Lin et al. (US 11,041,255)
Nakamura et al. (US 2019/0040545)
Hori et al. (US 12,125,881)
Kimoto et al., “Promise and Challenges of High-Voltage SiC Bipolar Power Devices,” Energies 9 (2016) 908.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to JAY C KIM whose telephone number is (571) 270-1620. The examiner can normally be reached 8:00 AM - 6:00 PM EST.
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/JAY C KIM/Primary Examiner, Art Unit 2815
/J. K./Primary Examiner, Art Unit 2815 March 13, 2026