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 .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 6/16/2026 has been entered.
Information Disclosure Statement
Acknowledgement is made of Applicant’s Information Disclosure Statement (IDS) form PTO-1449. The IDS has been considered.
Specification/Drawings
In view of Applicant’s new figures and specification, the prior objection for new matter is withdrawn.
Drawings
The drawings are objected to under 37 CFR 1.83(a). The drawings must show every feature of the invention specified in the claims. Therefore, a depletion layer generated at an interface between the P-type silicon carbide layer and the unintentionally doped silicon carbide layer; the steps of the first grooves; and where defects are repaired in an interface between the N-type silicon carbide substrate and the P-type silicon carbide layer, as found in claim 1, must be shown or the feature(s) canceled from the claim(s). No new matter should be entered.
Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application. Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as “amended.” If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency. Additional replacement sheets may be necessary to show the renumbering of the remaining figures. Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either “Replacement Sheet” or “New Sheet” pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
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 and 21 are rejected under 35 U.S.C. 103 as being unpatentable over Henning et al. (US 2007/0292999), Miura et al. (US 2006/0169987), and Khlebnikov et al. (US 2021/0198804), all of record.
(Re Claim 1) Henning teaches a silicon carbide homoepitaxial substrate, comprising: an N-type silicon carbide substrate (10; Fig. 5A, ¶69); a defect repair layer (16; 16 may be formed on the N-type silicon carbide substrate 10 when the optional layer 12 is not formed; Fig. 5A, ¶70); and an unintentionally doped silicon carbide layer (18; Fig. 3A, ¶70) on the defect repair layer, and the unintentionally doped silicon carbide layer has N-type element impurities (N-type element impurities are introduced to alter the conductivity of particular regions of the unintentionally doped silicon carbide layer; ¶48);
wherein the defect repair layer is a P-type silicon carbide layer (¶47).
Henning has not been shown to teach a silicon carbide homoepitaxial substrate, comprising:
an N-type silicon carbide substrate with first grooves; a defect repair layer on inner walls of the first grooves and outside the first grooves, provided with second grooves corresponding to the first grooves; and an unintentionally doped silicon carbide layer on the defect repair layer, wherein the second grooves are fully filled with the unintentionally doped silicon carbide layer, wherein a conductivity of the unintentionally doped silicon carbide layer is lower than a conductivity of the N-type silicon carbide substrate;
wherein the P-type silicon carbide layer forms a P-N junction with the unintentionally doped silicon carbide layer, and a depletion layer is generated at an interface therebetween, thereby reducing a leakage current of the silicon carbide substrate; and
wherein the P-type silicon carbide layer preferentially nucleates and grows at steps of the first grooves, and defects in the N-type silicon carbide substrate are repaired at an interface between the N-type silicon carbide substrate and the P-type silicon carbide layer.
Miura teaches a substrate (1; Fig. 11) with first grooves (4; see the Fig. 11 markup showing the span between each first groove of the substrate) forming a defect repair layer (4; formed from silicon carbide; “It is best suitable to use a SiC layer formed by carbonization, SiC layer formed at lower temperatures…for example, as a material for the buffer layer 4”; ¶54; Fig. 11) on inner walls of the first grooves and outside the first grooves (Fig. 11), provided with second grooves (see the Fig. 11 markup showing the span between each second groove of the defect repair layer) corresponding to the first grooves, wherein the second grooves are fully filled with a silicon carbide layer (5; Fig. 11).
Additionally, Miura teaches that SiC may be used as the material of the substrate (¶67).
A PHOSITA would find it obvious to form the N-type silicon carbide substrate 10 of Henning with first grooves as taught by Miura; such that the defect repair layer 16 of Henning is formed on inner walls of the first grooves and outside the first grooves, and is provided with second grooves corresponding to the first grooves; and the doped silicon carbide layer fully fills the second grooves of the defect repair layer 16, in the manner taught by Miura, in order to improve the film quality of the unintentionally doped silicon carbide layer 18 of modified Henning, by suppressing defect propagation from the substrate into higher silicon carbide layers (“[m]aking the buffer layer more subject to the defect than the SiC layer allows the layer to include the defects. Thus, production of the defects with a higher probability at the specified positions relieves strain. The control of development of the defects causes the defects to disappear, realizing a less-strained and lower defect-density SiC layer.”; ¶48; see also ¶¶62, 67-68).
Khlebnikov teaches concentration ranges for N-type silicon carbide substrates or unintentionally doped silicon carbide (¶80), where the conductivity (the inverse of resistivity) of the unintentionally doped silicon carbide layer is lower than a conductivity of the N-type silicon carbide layers (highest resistivity for N-type silicon carbide of 0.03 ohm-cm; lowest resistivity listed for either an unintentionally doped silicon carbide layer or undoped SiC is 1,500 ohm-cm; ¶80).
As a PHOSITA would find it obvious to form the N-type silicon carbide substrate of modified Henning according to Khlebnikov’s N-type silicon carbide substrate, as that doping treatment predictably produces an N-type silicon carbide substrate as required by an embodiment of Henning. Khlebnikov’s N-type silicon carbide substrate is suitable for power devices (Khlebnikov: ¶80; Henning: ¶44). See Ruiz v. A.B. Chance Co., 357 F.3d 1270, 69 USPQ2d 1686 (Fed. Cir. 2004).
This results in modified Henning having an N-type silicon carbide substrate with a lower bound for conductivity of 1/(0.03 ohm-cm) (Khlebnikov: ¶80).
Furthermore, Khlebnikov teaches that undoped silicon carbide has a conductivity smaller than the N-type silicon carbide (¶80).
As Henning teaches that the unintentionally doped silicon carbide layer may be unintentionally doped and undoped (¶47), a conductivity of the unintentionally doped silicon carbide layer of modified Henning is lower than a conductivity of the N-type silicon carbide substrate as doped according to Khlebnikov, due at least to also being undoped.
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Furthermore, as the prior art has been shown to be identical to the claimed structure of the invention, a PHOSITA would find it obvious for modified Henning’s silicon carbide epitaxial substrate to possess the claimed properties of the different material layers and interfacial interactions resulting therefrom. Where the claimed and prior art products are identical or substantially identical in structure or composition, or are produced by identical or substantially identical processes, a prima facie case of either anticipation or obviousness has been established. In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433 (CCPA 1977). "When the PTO shows a sound basis for believing that the products of the applicant and the prior art are the same, the applicant has the burden of showing that they are not." In re Spada, 911 F.2d 705, 709, 15 USPQ2d 1655, 1658 (Fed. Cir. 1990). See especially MPEP 2112.01.
Therefore, modified Henning teaches the silicon carbide homoepitaxial substrate wherein the P-type silicon carbide layer forms a P-N junction with the unintentionally doped silicon carbide layer (as a result of the properties of these layers), and a depletion layer is generated at an interface (where the layers contact, as a result of their properties) therebetween, thereby reducing a leakage current of the silicon carbide substrate; and
wherein the P-type silicon carbide layer preferentially nucleates and grows (as a result of its properties due to the material or geometry) at steps (each of the L-shaped portions of each first groove) of the first grooves, and defects in the N-type silicon carbide substrate are repaired at an interface (where contact occurs) between the N-type silicon carbide substrate and the P-type silicon carbide layer (due to the layers’ properties).
(Re Claim 21) Modified Henning teaches the silicon carbide homoepitaxial substrate of claim 1, but has not been shown to teach wherein a depth to width ratio of the first groove ranges from 1:1 to 1:3; and wherein defects in the N-type silicon carbide substrate are terminated in the defect repair layer.
Miura teaches that a depth of a first groove may be 0.5 µm (“The insulating film may be preferably one tenth to one fifth of a thickness of a pattern depth formed later. It has been set at 50 nm to 100 nm in the present embodiment”; ¶53), and a width may be about 0.5 µm (“a pattern width is about 0.5 µm”; ¶53). This results in a depth to width ratio of about 1:1.
A prima facie case of obviousness exists where the claimed ranges or amounts do not overlap with the prior art but are merely close. Titanium Metals Corp. of America v. Banner, 778 F.2d 775, 783, 227 USPQ 773, 779 (Fed. Cir. 1985) (Court held as proper a rejection of a claim directed to an alloy of "having 0.8% nickel, 0.3% molybdenum, up to 0.1% iron, balance titanium" as obvious over a reference disclosing alloys of 0.75% nickel, 0.25% molybdenum, balance titanium and 0.94% nickel, 0.31% molybdenum, balance titanium. "The proportions are so close that prima facie one skilled in the art would have expected them to have the same properties."). Therefore, modified Henning teaches the claimed depth to width ratio.
Furthermore, as the prior art has been shown to be identical to the claimed structure of the invention, a PHOSITA would find it obvious for modified Henning’s silicon carbide homoepitaxial substrate to possess the claimed defect termination location. Where the claimed and prior art products are identical or substantially identical in structure or composition, or are produced by identical or substantially identical processes, a prima facie case of either anticipation or obviousness has been established. In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433 (CCPA 1977). "When the PTO shows a sound basis for believing that the products of the applicant and the prior art are the same, the applicant has the burden of showing that they are not." In re Spada, 911 F.2d 705, 709, 15 USPQ2d 1655, 1658 (Fed. Cir. 1990). See MPEP 2112.01.
Claim 4 is rejected under 35 U.S.C. 103 as being unpatentable over Henning et al. (US 2007/0292999), Miura et al. (US 2006/0169987), and Khlebnikov et al. (US 2021/0198804), all of record, as applied to claim 1 above, and further in view of Majhi et al. (US 2011/0147845), Sriram (US 2003/0075719), and Chirovsky et al. (US 6,169,756), all of record.
(Re Claim 4) Modified Henning teaches the silicon carbide homoepitaxial substrate of claim 1, but has not been shown to explicitly teach the silicon carbide homoepitaxial substrate wherein in a thickness direction of the N-type silicon carbide substrate, doping of P-type ions in the P- type silicon carbide layer comprises at least one of: uniform doping, modulation doping, or Delta doping.
Sriram teaches forming a defect repair layer (14; buffer layer 12 is optionally formed; Fig. 1, ¶29) as a P-type silicon carbide layer (¶¶30, 33) that is delta doped (¶30).
A person having ordinary skill in the art before the effective filing date of the claimed invention would find it obvious to form the P-type silicon carbide layer 16 of modified Henning with a Delta doping in a thickness direction of the N-type silicon carbide substrate, as taught by Sriram, as this is an appropriate dopant profile for a P-type silicon carbide layer situated on an N-type silicon carbide substrate, Delta doping is a well known technique that predictably introduces dopants into a layer (Chirovsky: col. 8 ln. 14-20), and a Delta doped layer may improve short channel characteristics (Majhi: ¶5). See Ruiz v. A.B. Chance Co., 357 F.3d 1270, 69 USPQ2d 1686 (Fed. Cir. 2004).
Claim 22 is rejected under 35 U.S.C. 103 as being unpatentable over Henning et al. (US 2007/0292999), Miura et al. (US 2006/0169987), and Khlebnikov et al. (US 2021/0198804), all of record as applied to claim 1 above, and further in view of Piao et al. (CN 112746314, with line number reference to the provided translation) newly cited.
(Re Claim 22) Modified Henning teaches the silicon carbide homoepitaxial substrate of claim 1, but has not been explicitly shown to teach the N-type silicon carbide substrate is a silicon carbide substrate without a deflection angle.
Piao teaches forming a silicon carbide wafer with 0 degree of deflection angle i.e., is formed without a deflection angle (ln. 451-452).
A PHOSITA would find it obvious to form the N-type silicon carbide substrate without a deflection angle as taught by Piao to form the N-type silicon carbide substrate with excellent crystal characteristics (ln. 454).
Response to Arguments
Applicant's arguments filed 6/16/2026 have been fully considered but they are not persuasive.
Applicant first argues (remarks, p. 11) that no reference appears to teach, alone or in combination, preferential nucleation, a P-N junction, and defect repair, as claimed. However, as the prior art has been shown to be identical to the claimed structure of the invention, a PHOSITA would find it obvious for modified Henning’s silicon carbide epitaxial substrate to possess the claimed properties of the different material layers and interfacial interactions resulting therefrom. Where the claimed and prior art products are identical or substantially identical in structure or composition, or are produced by identical or substantially identical processes, a prima facie case of either anticipation or obviousness has been established. In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433 (CCPA 1977). "When the PTO shows a sound basis for believing that the products of the applicant and the prior art are the same, the applicant has the burden of showing that they are not." In re Spada, 911 F.2d 705, 709, 15 USPQ2d 1655, 1658 (Fed. Cir. 1990). See especially MPEP 2112.01.
Applicant next argues (remarks, p. 12) that there would be no reason to consult Miura as Miura solves a problem different from the Applicant. However, the reason or motivation to modify the reference may often suggest what the inventor has done, but for a different purpose or to solve a different problem. It is not necessary that the prior art suggest the combination to achieve the same advantage or result discovered by applicant. See, e.g., In re Kahn, 441 F.3d 977, 987, 78 USPQ2d 1329, 1336 (Fed. Cir. 2006) (motivation question arises in the context of the general problem confronting the inventor rather than the specific problem solved by the invention).
Applicant then argues (remarks, p. 12) that there is no motivation to combine the teachings of Henning and Miura as applied in the rejection due to an incompatibility between the requirements of the layer 4 from Miura and layer 16 of Henning. From the paragraphs of Henning cited by Applicant for support that there is a requirement for Henning’s P-type layer to have a high crystal quality unmet by Miura’s teachings, there is neither mention of crystal quality nor of a critical current blocking function. Applicant also places in quotes “needs high crystal quality” as a likely reference to Henning but the origin of this phrase is unknown. It is unclear where the particular quality of Henning’s P-type layer is essential to Henning’s device is described – explicitly or otherwise. Miura teaches that providing its defect repair layer as shown in the rejection above improves the film quality of layers formed upon it by suppressing defect propagation from the substrate into higher silicon carbide layers (Miura: ¶48; see also ¶¶62, 67-68). As the properties of Henning’s P-type layer are not described as essential to the operation of Henning’s device, alterations of Henning’s P-type layer are acceptable, especially when it is in the pursuit of other desirable properties such as the crystal quality of the unintentionally doped silicon carbide layer (see the rejection of claim 1).
If there is a diminished capacity for current blocking after the modification in view of Miura due to lost crystal quality, then in the absence of evidence to suggest an essential current blocking function is lost, the tradeoff would still produce an operable device, just with different properties. In Allied Erecting v. Genesis Attachments, 825 F.3d 1373, 1381, 119 USPQ2d 1132, 1138 (Fed. Cir. 2016), the court stated "[a]lthough modification of the movable blades may impede the quick change functionality disclosed by Caterpillar, ‘[a] given course of action often has simultaneous advantages and disadvantages, and this does not necessarily obviate motivation to combine’" (quoting Medichem, S.A. v. Rolabo, S.L., 437 F.3d 1157, 1165, 77 USPQ2d 1865, 1870 (Fed. Cir. 2006) (citation omitted)).
Applicant also specifically argues (remarks, p. 13) that there is no motivation to combine Henning and Miura to achieve to arrive at the solution of claim 1. Again, as the prior art has been shown to be identical to the claimed structure of the invention, a PHOSITA would find it obvious for modified Henning’s silicon carbide epitaxial substrate to possess the claimed properties of the different material layers and interfacial interactions resulting therefrom. Where the claimed and prior art products are identical or substantially identical in structure or composition, or are produced by identical or substantially identical processes, a prima facie case of either anticipation or obviousness has been established. In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433 (CCPA 1977). "When the PTO shows a sound basis for believing that the products of the applicant and the prior art are the same, the applicant has the burden of showing that they are not." In re Spada, 911 F.2d 705, 709, 15 USPQ2d 1655, 1658 (Fed. Cir. 1990). See especially MPEP 2112.01.
The remainder of Applicant’s arguments are moot.
Conclusion
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/CHRISTOPHER A. SCHODDE/Examiner, Art Unit 2898
/JESSICA S MANNO/SPE, Art Unit 2898
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