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 § 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 5, 7, 8, 16, 20 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.
Claim 5 includes “wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, and wherein the two or more first layers have different Al composition ratios from each other.” It is unclear what the first layers and the second layers are. For the purpose of the instant examination, the Examiner interprets the first layers as 128a, 128c, and128e, and the second layers as 128b, 128d, and 128f.
Claim 7 includes “wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, and wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other It is unclear what the first layers and the second layers are. For the purpose of the instant examination, the Examiner interprets the first layers as 128a, 128c, and128e, and the second layers as 128b, 128d, and 128f.
Claim 8 includes “wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.” It is unclear what the first layers and the second layers are. For the purpose of the instant examination, the Examiner interprets the first layers as 128a, 128c, and128e, and the second layers as 128b, 128d, and 128f.
Claim 16 includes “wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other, wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.” It is unclear what the first layers and the second layers are. For the purpose of the instant examination, the Examiner interprets the first layers as 128a, 128c, and128e, and the second layers as 128b, 128d, and 128f.
Claim 20 includes “wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other, wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.” It is unclear what the first layers and the second layers are. For the purpose of the instant examination, the Examiner interprets the first layers as 128a, 128c, and128e, and the second layers as 128b, 128d, and 128f.
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, 2, 3, 5, 10, 11 are rejected under 35 U.S.C. 103 as being unpatentable over Tang et al. US 20210320197 A1 (hereinafter Tang) and further in view of Chu et al. US 20190067464 A1 (hereinafter Chu)
Regarding claim 1, Tang discloses:
a channel layer; (the buffer layer 210 is a narrow band-gap channel layer. paragraph [0030])
a barrier layer above the channel layer and comprising a material having an energy band gap that is different from an energy band gap of the channel layer; (The barrier layer 206 is a wide band-gap donor-supply layer and the buffer layer 210 is a narrow band-gap channel layer. paragraph [0030])
a gate electrode above the barrier layer; (the thinner barrier layer 206 below the second gate 204; paragraph [0030])
a gate semiconductor layer between the barrier layer and the gate electrode. (Fig 2 shows a region of semiconductor material 206 under second gate 104)
a source electrode at a first side of the gate electrode and on a first side surface of the channel layer and a first side surface of the barrier layer; (FIG. 2, applying the same gate-to-source voltage to the first gate 202 and the second gate 204 restores high mobility carriers to the opening 216 in the 2DEG 212, forming a conductive channel between the source 208S and the drain 208D, and turning on the HEMT 200. Paragraph [0031])
a drain electrode at a second side of the gate electrode, opposite to the first side, and on a second side surface of the channel layer and a second side surface of the barrier layer; (forming a conductive channel between the source 208S and the drain 208D, and turning on the HEMT 200. paragraph [0031])
Tang does not disclose:
a superlattice layer between the barrier layer and the gate semiconductor layer, the superlattice layer comprising at least one first layer comprising AlGaN and at least one second layer comprising GaN, wherein the at least one first layer and the at least one second layer are alternately stacked.
Chu discloses:
a superlattice layer between the barrier layer and the gate semiconductor layer, (a digital superlattice alloy 205 back barriers mounted over the buffer layer 201. paragraph [0051]) the superlattice layer comprising at least one first layer comprising AlGaN and at least one second layer comprising GaN, wherein the at least one first layer and the at least one second layer are alternately stacked. (The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages. Paragraph [0051]
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 2, Tang in view of Chu teaches the limitations of claim 1, as discussed above.
Tang does not disclose:
the barrier layer comprises AlGaN, and the AlGaN in the barrier layer has an Al composition ratio different from an Al composition ratio of the AlGaN in the at least one first layer.
Chu discloses:
the barrier layer comprises AlGaN, and the AlGaN in the barrier layer has an Al composition ratio different from an Al composition ratio of the AlGaN in the at least one first layer. (An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages; paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 3, Tang in view of Chu teaches the limitations of claim 2, as discussed above.
Tang does not disclose:
wherein the Al composition ratio of the AlGaN in the at least one first layer is less than the Al composition ratio of the AlGaN in the barrier layer.
Chu discloses:
wherein the Al composition ratio of the AlGaN in the at least one first layer is less than the Al composition ratio of the AlGaN in the barrier layer. (An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages; paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 5, Tang in view of Chu teaches the limitations of claim 1, as discussed above.
Tang does not disclose:
At least one first layer is two or more first layers, and the at least one second layer is two or more second layers, and wherein the two or more first layers have different Al composition ratios from each other.
Chu discloses:
at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, and wherein the two or more first layers have different Al composition ratios from each other. (The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages; paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 10, Tang in view of Chu does not disclose:
wherein the superlattice layer has a narrower width than a width of the barrier layer.
However, a change in size or shape or both is an unpatentable modification when it results in optimum conditions that differ from the prior art in degree but not in kind. In Re Rose, 220 F.2d 459, 105 USPQ 237, In reDailey, 357 F.2d 669, 149 USPQ 47). In the instant case the prior art device would not perform differently if modified to the claimed shape or size. Therefore, the claimed limitations are considered met.
Regarding claim 11, Tang in view of Chu does not disclose:
wherein the superlattice layer has a width equal to a width of the gate semiconductor layer.
However, a change in size or shape or both is an unpatentable modification when it results in optimum conditions that differ from the prior art in degree but not in kind. In Re Rose, 220 F.2d 459, 105 USPQ 237, In reDailey, 357 F.2d 669, 149 USPQ 47). In the instant case the prior art device would not perform differently if modified to the claimed shape or size. Therefore, the claimed limitations are considered met.
Claim 4 is rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chu and further in view of Lu et al. US 20210265477 A1 (hereinafter Lu)
Regarding claim 4, Tang in view of Chu teaches the limitations of claim 1, as discussed above.
Tang in view of Chu does not disclose:
wherein the at least one first layer has an Al composition ratio of 1 to 5 at %.
Lu discloses:
wherein the at least one first layer has an Al composition ratio of 1 to 5 at %. (AlN and InAlGaN with Al percentage ranging from 0 to 100%. Paragraph [0063]; “0%-100%” satisfies the claimed atomic percentage range (1%-5%)
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Lu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claims 6, 7, and 8 are rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chu and further in view of Kim et al. US 20220359739 A1 (hereinafter Kim)
Regarding claim 6, Tang in view of Chu teaches the limitations of claim 1, as discussed above.
Tang in view of Chu does not disclose:
wherein the gate semiconductor layer and the superlattice layer are doped by p-type dopants, and the superlattice layer has a doping concentration equal to or greater than a doping concentration of the gate semiconductor layer.
Kim discloses:
wherein the gate semiconductor layer and the superlattice layer are doped by p-type dopants, and the superlattice layer has a doping concentration equal to or greater than a doping concentration of the gate semiconductor layer. (a first layer, such as a superlattice… A second layer, such as a p-type AlGaN layer, formed over the first layer and between the channel and the first layer may comprise a second amount of the metal material… the p-type AlGaN layer comprises a high density of p-type dopant… accumulated holes will then drift towards the gate and accumulate at the gate… paragraph [0021])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Kim's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 7, Tang in view of Chu and further in view of Kim teaches the limitations of claim 6, as discussed above.
Tang does not disclose:
wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, and wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other.
Chu discloses:
wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, and wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other. (The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages; paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 8, Tang in view of Chu and further in view of Kim teaches the limitations of claim 7, as discussed above.
Tang does not disclose:
wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.
Chu discloses:
wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer. (The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages; paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claim 9 is rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chu and further in view of Okada US 20220158025 A1 (hereinafter Okada)
Regarding claim 9, Tang in view of Chu teaches the limitations of claim 1, as discussed above.
Tang in view of Chu does not disclose:
wherein each of the at least one first layer and the at least one second layer has a thickness greater than or equal to 1 nm and less than or equal to 3 nm.
Okada discloses:
wherein each of the at least one first layer and the at least one second layer has a thickness greater than or equal to 1 nm and less than or equal to 3 nm. (The superlattice layer 26 is 1 nm or more and 3 nm or less. Paragraph [0020])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Okada 's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claim 12 is rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chu and further in view of Kim and further in view of Renaldo et al. US 20160049504 A1 (hereinafter Renaldo)
Regarding claim 12, Tang in view of Chu and further in view of Kim teaches the limitations of claim 6, as discussed above.
Tang in view of Chu and Kim does not disclose:
wherein one of the at least one second layer is on one of the at least one first layer, the one of the at least one first layer is in contact with an upper surface of the barrier layer, and the one of the at least one second layer is in contact with a lower surface of the gate
Renaldo discloses:
wherein one of the at least one second layer is on one of the at least one first layer, the one of the at least one first layer is in contact with an upper surface of the barrier layer, and the one of the at least one second layer is in contact with a lower surface of the gate. (a superlattice structure overlying the barrier layer, the superlattice structure comprising a plurality of heterostructures, and with trenches formed in portions of the multichannel structure to create castellated gate contacts; claim 17)
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Renaldo 's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claims 13, 14 are rejected under 35 U.S.C. 103 as being unpatentable over Tang and further in view of Chu.
Regarding claim 13, Tang discloses:
a substrate (Fig. 1; 110); a buffer layer on the substrate (Fig. 1; 104); a channel layer (conductive channel 212; paragraph [0030]);
a barrier layer above the channel layer and comprising a material with an energy band gap that is higher than an energy band gap of the channel layer; (The barrier layer 206 is a wide band-gap donor-supply layer and the buffer layer 210 is a narrow band-gap channel layer. paragraph [0030])
a gate electrode above the barrier layer; a gate semiconductor layer between the barrier layer and the gate electrode; (Fig 2 shows a region of semiconductor material 206 under second gate 104)
a source electrode at a first side of the gate electrode and on a first side surface of the channel layer and a first side surface of the barrier layer; (FIG. 2, applying the same gate-to-source voltage to the first gate 202 and the second gate 204 restores high mobility carriers to the opening 216 in the 2DEG 212, forming a conductive channel between the source 208S and the drain 208D, and turning on the HEMT 200. Paragraph [0031])
a drain electrode at a second side of the gate electrode, opposite to the first side, and on a second side surface of the channel layer and a second side surface of the barrier layer; (forming a conductive channel between the source 208S and the drain 208D, and turning on the HEMT 200. paragraph [0031])
Tang does not disclose:
a spacer layer between the channel layer and the barrier layer and comprising a material with an energy band gap that is higher than the energy band gap of the barrier layer
the lower superlattice layer; an upper superlattice layer between the barrier layer and the gate semiconductor layer, the upper superlattice layer comprising at least one first layer comprising AlGaN and at least one second layer comprising GaN, wherein the at least one first layer and the at least one second layer are alternately stacked.
Chu discloses:
a spacer layer between the channel layer and the barrier layer and comprising a material with an energy band gap that is higher than the energy band gap of the barrier layer; (a AlN spacer 612, which is primarily introduced between the GaN channel 503 and the AlGaN layer 502; paragraph [0065])
a superlattice layer between the barrier layer and the gate semiconductor layer, (a digital superlattice alloy 205 back barriers mounted over the buffer layer 201. paragraph [0051])
the superlattice layer comprising at least one first layer comprising AlGaN and at least one second layer comprising GaN, wherein the at least one first layer and the at least one second layer are alternately stacked. (The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages. Paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's spacer into Tang’s device to keep transport electrons inside the high-purity channel, protecting them from alloy scatter; to boost the saturation and drain current density for high-power operations. And it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 14, Tang in view of Chu teaches the limitations of claim 13, as discussed above.
Tang does not disclose:
wherein the barrier layer comprises AlGaN, and an Al composition ratio of the AlGaN in the at least one first layer is less than an Al composition ratio of the AlGaN in the barrier layer.
Chu discloses:
wherein the barrier layer comprises AlGaN, and an Al composition ratio of the AlGaN in the at least one first layer is less than an Al composition ratio of the AlGaN in the barrier layer (The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages. Paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claims 15, 16 are rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chu and further in view of Kim.
Regarding claim 15, Tang in view of Chu teaches the limitations of claim 14, as discussed above.
Tang in view of Chu does not disclose:
wherein the gate semiconductor layer and the upper superlattice layer are doped by p-type dopants, and the upper superlattice layer has a doping concentration equal to or greater a doping concentration of the gate semiconductor layer.
Kim discloses:
wherein the gate semiconductor layer and the upper superlattice layer are doped by p-type dopants, and the upper superlattice layer has a doping concentration equal to or greater a doping concentration of the gate semiconductor layer. (a first layer, such as a superlattice… A second layer, such as a p-type AlGaN layer, formed over the first layer and between the channel and the first layer may comprise a second amount of the metal material… the p-type AlGaN layer comprises a high density of p-type dopant… accumulated holes will then drift towards the gate and accumulate at the gate… paragraph [0021])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Kim's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 16, Tang in view of Chu and Kim teaches the limitations of claim 15, as discussed above.
Tang does not disclose:
wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other, wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.
Chu discloses:
wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other, wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer. (a digital superlattice alloy 205 back barriers mounted over the buffer layer 201. The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages. Paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Tang’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claims 17, 18 are rejected under 35 U.S.C. 103 as being unpatentable over Takatani et al. US 20210226019 A1 (hereinafter Takatani) and further in view of Chu
Regarding claim 17, Takatani discloses:
a channel layer comprising GaN (Fig. 10 The drift layer 601 may adopt n-type GaN; paragraph [0069]); a barrier layer above the channel layer and comprising AlGaN (A barrier layer 602, a first nitride semiconductor layer; paragraph [0069]);
a gate electrode above the barrier layer and comprising a metallic material; a gate semiconductor layer between the barrier layer and the gate electrode and comprising GaN doped with p-type impurities; (Fig. 6; a gate electrode 209 is formed. Paragraph [0064]);
a source electrode at a first side of the gate electrode and in contact with a first side surface of the channel layer and a first side surface of the barrier layer (Fig. 10. A source electrode 611 is formed on the second nitride semiconductor layer 605 to obtain good electrical connection with low resistance with respect to the conduction layer 614. Paragraph [0069]);
a drain electrode at a second side of the gate electrode, opposite to the first side, and in contact with a second side surface of the channel layer and a second side surface of the barrier layer; (Fig. 10; the drain electrode 612 of the back surface may also be formed before other electrodes are formed. paragraph [0069])
Takatani does not disclose:
a superlattice layer between the barrier layer and the gate semiconductor layer, the superlattice layer comprising at least one first layer comprising AlGaN and at least one second layer comprising GaN, wherein the at least one first layer and the at least one second layer are alternately stacked.
Chu discloses:
a superlattice layer between the barrier layer and the gate semiconductor layer, the superlattice layer comprising at least one first layer comprising AlGaN and at least one second layer comprising GaN, wherein the at least one first layer and the at least one second layer are alternately stacked. (Fig. 2. It uses alternating AlN/GaN layers forming a superlattice structure 205, which is referred to as a digital AlGaN alloy, to serve as the back barrier. Paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Takatani’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 18, Takatani in view of Chu teaches the limitations of claim 17, as discussed above.
Takatani does not disclose:
wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.
Chu discloses:
wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer. (a digital superlattice alloy 205 back barriers mounted over the buffer layer 201. The superlattice (SL) back barrier 205 typically has more than two; preferably 30 to 40 pairs of alternating AlN and GaN layers. An alternative SL structure is an alternating AlGaN and GaN stack up 205 or AlGaN/AlGaN stack up 205 where the AlGaN layers have different amount Aluminum percentages. Paragraph [0051])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Chu's superlattice layer into Takatani’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Claims 19, 20 are rejected under 35 U.S.C. 103 as being unpatentable over Takatani in view of Chu and further in view Kim
Regarding claim 19, Takatani in view of Chu teaches the limitations of claim 18, as discussed above.
Takatani in view of Chu does not disclose:
wherein the gate semiconductor layer and the superlattice layer are doped by p-type dopants, and the superlattice layer has a doping concentration equal to or greater than a doping concentration of the gate semiconductor layer.
Kim discloses:
wherein the gate semiconductor layer and the superlattice layer are doped by p-type dopants, and the superlattice layer has a doping concentration equal to or greater than a doping concentration of the gate semiconductor layer. (a first layer, such as a superlattice… A second layer, such as a p-type AlGaN layer, formed over the first layer and between the channel and the first layer may comprise a second amount of the metal material… the p-type AlGaN layer comprises a high density of p-type dopant… accumulated holes will then drift towards the gate and accumulate at the gate… paragraph [0021])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Kim's superlattice layer into Takatani’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Regarding claim 20, Takatani in view of Chu and Kim teaches the limitations of claim 19, as discussed above.
Takatani does not disclose:
wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other, wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer.
Kim discloses:
wherein the at least one first layer is two or more first layers, and the at least one second layer is two or more second layers, wherein the two or more first layers have different doping concentrations from each other, and the two or more second layers have different doping concentrations from each other, wherein the two or more first layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more first layers to the barrier layer, and wherein the two or more second layers have an increasing doping concentration in an order of farthest to nearest layer among the two or more second layers to the barrier layer. (Fig. 4; The entire superlattice 103 is used as the hole draining structure 402. The hole draining structure 402 may comprise a first plurality of layers, such as a layer 404, a layer 408, a layer 412, a layer 416, a layer 420, layer 424, and/or any other number of layers. It may be appreciated that the first plurality of layers may comprise any number of layers. Paragraph [0062]; the first layer 102 and decreasing concentrations of the metal material going towards the third layer 106. For example, each layer going from layer 408 down to layer 424 may have a certain percentage increase in aluminum content, such a 0.4% increase, a 4% increase, or any other percentage increase, which may be based upon how many layers are in the first plurality of layers. Paragraph [0063]; a first layer, such as a superlattice… A second layer, such as a p-type AlGaN layer, formed over the first layer and between the channel and the first layer may comprise a second amount of the metal material… the p-type AlGaN layer comprises a high density of p-type dopant… paragraph [0021])
Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to add Kim's superlattice layer into Takatani’s device. The reason to do this would be to increase the threshold voltage, reduce acceptor ionization/scattering, and suppress dopant diffusion.
Conclusion
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/WEI LI/Examiner, Art Unit 2899
/Brent A. Fairbanks/Supervisory Patent Examiner, Art Unit 2899
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