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 .
Election/Restrictions
Applicant’s election without traverse of Group I, claims 1-11, in the reply filed on 20 October 2025 is acknowledged. New claims 21-30 are acknowledged as reciting subject matter that is encompassed by Group I.
The requirement is still deemed proper and is therefore made FINAL.
Claims 12-20 would have been withdrawn from further consideration pursuant to 37 CFR 1.142(b) as being drawn to a nonelected invention, there being no allowable generic or linking claim; however, claims 12-20 were canceled.
Claim Interpretation
Claim 9 recites a resistivity but does not state whether the resistivity is sheet resistivity (i.e. typically having units of Ω/□) or bulk resistivity (i.e. typically having units of Ω∙cm). Since the instant specification discloses measuring sheet resistance (paragraph 0079) and does not mention measuring bulk resistivity, the instantly claimed resistivity will be considered to refer to sheet resistivity even though the units are simply Ω (i.e. instead of Ω/□).
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.
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.
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.
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.
Claims 1-9 and 21-27 are rejected under 35 U.S.C. 103 as being unpatentable over Dabiran et al. (US 2010/0117118), as evidenced by Enatsu et al. (US 2021/0384336) regarding claims 6 and 24.
Claim 1: Dabiran teaches a group III nitride materials based heterojunction device comprising growing, on a substrate, a buffer structure having a plurality of buffer structure layers (paragraph 0013). A highly resistive GaN multi-stage buffer layer is grown on a nucleation layer that is formed on a substrate (i.e. a substrate having a surface and a group III-nitride on the surface of the substrate, since GaN is a group III nitride) (paragraphs 0027-0028). Being resistive is considered to teach the group III-nitride structure as being semi-insulating. Dabiran teaches the resistive GaN multi-stage buffer layer 13 is grown with an iron (Fe) doping level of about 1E17 cm-3 to improve the buffer resistivity as high resistivity is needed to avoid having the layer provide a shunt path for charge carriers in the subsequently provided channel layer (paragraph 0028). Dabiran further teaches that the MBE growth of the GaN buffer layer 13 is started in a Ga-rich condition at the growth surface to typically the first tenth of the layer 13 thickness to promote the growth surface of layer material being smooth and then the remaining layer portion is grown in an N-rich condition at the growth surface to enhance incorporation of Fe impurities (i.e. Fe-dopant atoms) in GaN and to leave a smooth final grown surface for the next layer to be grown thereon (paragraph 0028). Next a diffusion stop layer 14 of undoped GaN is grown beginning under an N-rich condition at the growth surface for typically the first eight tenths thereof to limit the diffusion of Fe impurities occurring at the final surface of layer 13 to essentially tailing off to a negligible density through the layer 14 rather than continuing into the layers to be provided following layer 14 and then the growth conditions are made Ga-rich at the growth surface for the remaining growth of layer 14 to provide a finally grown surface that is again smooth for the subsequent layer to be grown thereon (paragraph 0029).
The first tenth of layer 13 being started in a Ga-rich condition (paragraph 0028), in view of the subsequent teaching of an N-rich growth condition being to enhance incorporation of Fe impurities (i.e. Fe-dopant) in GaN (paragraph 0028), would have been obvious to one of ordinary skill in the art before the effective filing date to be a region (i.e. a region of the first tenth of layer 13) that is free of Fe-dopant atoms as it would have been obvious to one of ordinary skill in the art before the effective filing date to wait to add Fe dopant into the MBE system when the incorporation of Fe into GaN would be favorable, and one would have had a reasonable expectation of success. This first tenth of layer 13 is considered to correspond to the instantly claimed substrate surface-adjacent region of the group III-nitride.
The remainder of layer 13 (i.e. grown under an N-rich condition and having incorporation of Fe impurities), which is contiguous with the first tenth of layer 13 (i.e. contiguous with the substrate surface-adjacent region), is considered to correspond to the instantly claimed donor-impurity-compensating layer of the group III-nitride because Dabiran teaches that the iron doping creates deep acceptor levels in GaN to capture electrons made available therein due to the crystal defects occurring due to being grown on layer 12 of another kind of material. Dabiran further teaches that the concentration of Fe doping of about 1E16 cm-3 to 1E18 cm-3 in combination with donor concentration less than 1E16 cm-3 (i.e. Fe-dopant atom concentration is greater than donor impurity atom concentration) yields semi-insulating GaN (paragraph 0083). Dabiran shows in Fig. 5 that the Fe concentration reaches a peak followed by a tapering in Fe dopant concentration (i.e. following the graph from right to left since the substrate would be at the greatest depth of the x-axis).
Dabiran shows in Fig. 5 that the Fe dopant concentration decreases from about 3x1017 cm-3 to about 1x1016 cm-3 (i.e. from depth of about 2.5 µm to depth of about 2.1 µm) for the formation temperature of about 1200°C, and this region (i.e. the depth of about 2.5 µm to about 2.1 µm) after Fe is turned off corresponds to the instantly claimed cut-off layer and is shown to be contiguous with the region when Fe is on (i.e. contiguous with the donor-impurity-atom-compensating layer). This decrease is a factor of about 30, which overlaps the instantly claimed range and the courts have held that a prima facie case of obviousness exists where claimed ranges overlap, lie inside of, or are close to ranges in the prior art. See MPEP § 2144.05. It is noted that as of the writing of this Office Action, no demonstration of a criticality to the claimed ranges has been presented.
While not reciting a singular example of the instantly claimed semi-insulating group III-nitride structure, it would have been obvious to one of ordinary skill in the art before the effective filing date as each of the instantly claimed features are taught or obvious to one of ordinary skill in the art, as outlined above, and one would have had a reasonable expectation of success.
Claim 2: Dabiran teaches that the first tenth of layer 13 is started in a Ga-rich condition, and in view of the subsequent teaching of an N-rich growth condition being to enhance incorporation of Fe impurities (i.e. Fe-dopant) in GaN (paragraph 0028), it would have been obvious to one of ordinary skill in the art before the effective filing date to be a region (i.e. a region of the first tenth of layer 13) that is free of Fe-dopant atoms as it would have been obvious to one of ordinary skill in the art before the effective filing date to wait to add Fe dopant into the MBE system when the incorporation of Fe into GaN would be favorable, and one would have had a reasonable expectation of success.
Claim 3: Dabiran teaches that the MBE growth of the GaN buffer layer 13 is started in a Ga-rich condition at the growth surface to typically the first tenth of the layer 13 thickness to promote the growth surface of layer material being smooth and then the remaining layer portion is grown in an N-rich condition at the growth surface to enhance incorporation of Fe impurities (i.e. Fe-dopant atoms) in GaN and to leave a smooth final grown surface for the next layer to be grown thereon (paragraph 0028). As outlined above, the first tenth of the layer 13 corresponds to the substrate surface-adjacent region and it would have been obvious to one of ordinary skill in the art for this region to be substantially free of Fe dopant atoms. As outlined above, the remaining layer portion (i.e. the portion grown in N-rich condition to enhance incorporation of Fe impurities) corresponds to the donor-impurity-atom-compensating layer. Dabiran further teaches the resistive GaN multi-stage buffer layer 13 is grown with an iron (Fe) doping level of about 1E17 cm-3 (i.e. in the portion corresponding to the donor-impurity-atom-compensating layer) to improve the buffer resistivity as high resistivity is needed to avoid having the layer provide a shunt path for charge carriers in the subsequently provided channel layer (paragraph 0028). Fig. 5 also shows the iron doping level increase when Fe dopant is turned on and then decrease after Fe dopant is turned off (i.e. the average Fe-dopant atom concentration is measured across the depth of the layer). This iron doping level (i.e. about 1E17 cm-3, which is equivalent to 1x1017 cm-3) overlaps the instantly claimed range for Fe-dopant atom concentration. See MPEP § 2144.05.
Claim 4: Dabiran teaches a group III nitride materials based heterojunction device comprising growing, on a substrate, a buffer structure having a plurality of buffer structure layers (paragraph 0013). A highly resistive GaN multi-stage buffer layer is grown on a nucleation layer that is formed on a substrate (i.e. GaN is the group III nitride) (paragraphs 0027-0028).
Claim 5: The limitations recited in claim 5 are substantially identical to the limitations recited in claim 3 (outlined above) except for the claim dependency.
Claim 6: Dabiran teaches that the substrate can be chosen from any of sapphire, silicon carbide, or silicon (i.e. comprises silicon atoms) (paragraph 0027) and teaches a donor concentration less than 1E16 cm-3 (paragraph 0083). Dabiran does not name specifically the donor species; however, known donor impurities that act as donors for GaN include oxygen, silicon, etc. as evidenced by Enatsu (paragraph 0073), and since Dabiran teaches the resistive buffer layer to be GaN (paragraphs 0027-0028), then the known donor impurities of at least oxygen and silicon are considered to be present.
Claim 7: Dabiran teaches the resistive buffer layer (i.e. the group III-nitride as outlined above) to be a GaN buffer layer (paragraphs 0027-0028).
Claim 8: Dabiran teaches that the substrate can be chosen from any of sapphire, silicon carbide, or silicon (paragraph 0027).
Claim 9: Dabiran teaches that being a semi-insulating GaN material means having a bulk resistivity >100 Ω∙cm at room temperature and teaches specific examples where the sheet resistivity ranges from 140 Ω/□ to 1390 Ω/□ (Table 1 and paragraphs 0068-0070).
Claim 21: The limitations recited in claim 21 are substantially identical to the limitations recited in claim 3 (outlined above) except for the claim dependency.
Claims 22-23: Dabiran teaches that the MBE growth of the GaN buffer layer 13 is started in a Ga-rich condition at the growth surface to typically the first tenth of the layer 13 thickness to promote the growth surface of layer material being smooth and then the remaining layer portion is grown in an N-rich condition at the growth surface to enhance incorporation of Fe impurities (i.e. Fe-dopant atoms) in GaN and to leave a smooth final grown surface for the next layer to be grown thereon (paragraph 0028). As outlined above, the first tenth of the layer 13 corresponds to the substrate surface-adjacent region and it would have been obvious to one of ordinary skill in the art for this region to be substantially free of Fe dopant atoms. As outlined above, the remaining layer portion (i.e. the portion grown in N-rich condition to enhance incorporation of Fe impurities) corresponds to the donor-impurity-atom-compensating layer. Dabiran further teaches the resistive GaN multi-stage buffer layer 13 is grown with an iron (Fe) doping level of about 1E17 cm-3 (i.e. in the portion corresponding to the donor-impurity-atom-compensating layer) to improve the buffer resistivity as high resistivity is needed to avoid having the layer provide a shunt path for charge carriers in the subsequently provided channel layer (paragraph 0028). Fig. 5 also shows the iron doping level increase when Fe dopant is turned on and then decrease after Fe dopant is turned off (i.e. the average Fe-dopant atom concentration is measured across the depth of the layer). This iron doping level (i.e. about 1E17 cm-3, which is equivalent to 1x1017 cm-3) in the region corresponding to the donor-impurity-atom-compensating layer is substantially higher than a level of about zero (i.e. at least 3 times greater and at least 5 times greater) in the region near the interface of the substrate and group III-nitride. This amount of increased Fe-dopant atom concentration overlaps the instantly claimed ranges. See MPEP § 2144.05.
Claim 24: Dabiran teaches that the substrate can be chosen from any of sapphire, silicon carbide, or silicon (i.e. comprises silicon atoms) (paragraph 0027) and teaches a donor concentration less than 1E16 cm-3 (paragraph 0083). Dabiran does not name specifically the donor species; however, known donor impurities that act as donors for GaN include oxygen, silicon, etc. as evidenced by Enatsu (paragraph 0073), and since Dabiran teaches the resistive buffer layer to be GaN (paragraphs 0027-0028), then the known donor impurities of at least oxygen and silicon are considered to be present.
Claim 25: Dabiran teaches the resistive buffer layer (i.e. the group III-nitride as outlined above) to be a GaN buffer layer (paragraphs 0027-0028).
Claims 26-27: Dabiran teaches that the MBE growth of the GaN buffer layer 13 is started in a Ga-rich condition at the growth surface to typically the first tenth of the layer 13 thickness to promote the growth surface of layer material being smooth and then the remaining layer portion is grown in an N-rich condition at the growth surface to enhance incorporation of Fe impurities (i.e. Fe-dopant atoms) in GaN and to leave a smooth final grown surface for the next layer to be grown thereon (paragraph 0028). As outlined above, the first tenth of the layer 13 corresponds to the substrate surface-adjacent region and it would have been obvious to one of ordinary skill in the art for this region to be substantially free of Fe dopant atoms. As outlined above, the remaining layer portion (i.e. the portion grown in N-rich condition to enhance incorporation of Fe impurities) corresponds to the donor-impurity-atom-compensating layer, which overlaps the instantly claimed range of less than 1x1016 cm-3. See MPEP § 2144.05. Dabiran further teaches the resistive GaN multi-stage buffer layer 13 is grown with an iron (Fe) doping level of about 1E17 cm-3 (i.e. in the portion corresponding to the donor-impurity-atom-compensating layer) to improve the buffer resistivity as high resistivity is needed to avoid having the layer provide a shunt path for charge carriers in the subsequently provided channel layer (paragraph 0028). Fig. 5 also shows the iron doping level increase when Fe dopant is turned on and then decrease after Fe dopant is turned off (i.e. the average Fe-dopant atom concentration is measured across the depth of the layer). Dabiran further teaches that Fe doping may be effective with concentrations of about 1E16 cm-3 to about 1E18 cm-3 (i.e. to about 1x1018 cm-3), which overlaps the instantly claimed ranges. See MPEP § 2144.05.
Claims 10-11 are rejected under 35 U.S.C. 103 as being unpatentable over Dabiran et al. (US 2010/0117118) as applied to claims 4 and 8 above, and further in view of Meguro et al. (US 2021/0210602).
Claims 10-11: The teaching of Dabiran regarding claims 4 and 8 are outlined above. Dabiran teaches a group III nitride materials based heterojunction device comprising growing, on a substrate, a buffer structure having a plurality of buffer structure layers (paragraph 0013). A highly resistive GaN multi-stage buffer layer is grown on a nucleation layer that is formed on a substrate (paragraphs 0027-0028). Dabiran teaches the resistive GaN multi-stage buffer layer 13 is grown with an iron (Fe) doping level of about 1E17 cm-3 to improve the buffer resistivity as high resistivity is needed to avoid having the layer provide a shunt path for charge carriers in the subsequently provided channel layer (paragraph 0028). Dabiran further teaches that the MBE growth of the GaN buffer layer 13 is started in a Ga-rich condition at the growth surface to typically the first tenth of the layer 13 thickness to promote the growth surface of layer material being smooth and then the remaining layer portion is grown in an N-rich condition at the growth surface to enhance incorporation of Fe impurities (i.e. Fe-dopant atoms) in GaN and to leave a smooth final grown surface for the next layer to be grown thereon (paragraph 0028). Next a diffusion stop layer 14 of undoped GaN is grown beginning under an N-rich condition at the growth surface for typically the first eight tenths thereof to limit the diffusion of Fe impurities occurring at the final surface of layer 13 to essentially tailing off to a negligible density through the layer 14 rather than continuing into the layers to be provided following layer 14 and then the growth conditions are made Ga-rich at the growth surface for the remaining growth of layer 14 to provide a finally grown surface that is again smooth for the subsequent layer to be grown thereon (paragraph 0029). However, although teaching a smooth final grown surface of the GaN, Dabiran does not teach a quantitative surface roughness.
In a related field of endeavor, Meguro teaches a GaN layer formed on an underlying substrate (paragraph 0005). Meguro teaches that the GaN layer has high surface flatness, specifically with a root mean square surface roughness determined by measurement of a 5-µm square region of 0.5 nm or less, more preferably 0.4 nm or less (paragraph 0042). Although the measurement area is not the same as the instantly claimed surface area (i.e. Meguro teaches a 5-µm square region instead of the instantly claimed surface area of 10 µm by 10 µm), this is considered a product-by-process limitation (i.e. how to measure the surface roughness) and is not considered to render a patentable distinction absent an objective showing that the surface roughness would be different for a different measurement area. The surface roughness of 0.5 nm or less overlaps the instantly claimed range of no greater than 3 nm, and the courts have held that a prima facie case of obviousness exists where claimed ranges overlap, lie inside of, or are close to ranges in the prior art. See MPEP § 2144.05. It is noted that as of the writing of this Office Action, no demonstration of a criticality to the claimed ranges has been presented.
As Dabiran and Meguro both teach a smooth/flat GaN layer formed on a substrate, they are analogous. It would have been obvious to one of ordinary skill in the art before the effective filing date to modify the GaN layer (i.e. the undoped portion formed after the Fe-doped portion) of Dabiran to include where the final rms surface roughness is 0.5 nm or less, or more preferably 0.4 nm or less as taught by Meguro as this is considered a conventionally known feature of a GaN layer (especially in view of Dabiran teaching a smooth surface is desirable), and one would have had a reasonable expectation of success.
Allowable Subject Matter
Claims 28-30 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.
The following is a statement of reasons for the indication of allowable subject matter:
The closest prior art is the teachings of Dabiran as outlined above. Dabiran teaches a diffusion stop layer 14 of undoped GaN is grown beginning under an N-rich condition at the growth surface for typically the first eight tenths thereof to limit the diffusion of Fe impurities occurring at the final surface of layer 13 to essentially tailing off to a negligible density through the layer 14 rather than continuing into the layers to be provided following layer 14 and then the growth conditions are made Ga-rich at the growth surface for the remaining growth of layer 14 to provide a finally grown surface that is again smooth for the subsequent layer to be grown thereon (paragraph 0029). The Fe-diffusion stop layer is grown to a thickness of about 0.3 µm (paragraph 0051). Dabiran shows in Fig. 5 that the Fe dopant concentration decreases from about 3x1017 cm-3 to about 1x1016 cm-3 (i.e. from depth of about 2.5 µm to depth of about 2.1 µm) for the formation temperature of about 1200°C, and this region (i.e. the depth of about 2.5 µm to about 2.1 µm) after Fe is turned off corresponds to the instantly claimed cut-off layer, and Fig. 5 shows this thickness to be about 0.5 µm (i.e. about 500 nm). Both of these thicknesses (i.e. about 0.3 µm for the Fe-diffusion stop layer and about 0.5 µm for the region of Fe dopant concentration decrease) are substantially greater than the instantly claimed cut-off layer depth of 50 nm or less. Furthermore, since the Fe dopant was turned off but the GaN layer still required a substantially greater depth than the instantly claimed depth in order for the Fe dopant to reduce to a residual level, then there is no teaching in Dabiran that provides motivation for a cut-off layer to have a depth of 50 nm or less while also having the Fe-dopant atom concentration decrease by a factor of at least ten across its depth.
Conclusion
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/KIM S. HORGER/Examiner, Art Unit 1784