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.
Claims 1-18 are rejected under 35 U.S.C. 112(b) as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor regards as the invention.
Specifically, “the second direction” lacks antecedent basis and should be “a second direction.” Independent Claims 10-18 carry the same defect by incorporation. The remaining claims are rejected as being dependent on Claim 1.
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, 4, 5, 10, 11, 13 and 14 are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Pat. Pub. No. 20210288156 to Fukui et al. (Fukui) in view of U.S. Pat. Pub. No. 20100059816 to Shimada et al. and further in view of JP2007019412 to Koyama et al. (Koyama).
Regarding Claim 1, Fukui teaches in Fig. 3 at least, silicon carbide semiconductor device comprising:
a drift layer 3 of a first conductivity type that is provided between a first main surface and a second main surface of a semiconductor substrate;
a base layer 4 of a second conductivity type that is provided on a first main surface side of the drift layer;
a source layer 5 of the first conductivity type that is selectively provided on a first main surface side of the base layer;
a trench gate that has a gate electrode 8 provided via a gate insulating film 7 on an inner surface of each of a plurality of trenches, the plurality of trenches being provided side by side in a first direction and extending in a second direction in a plan view, and in contact with the base layer and the source layer in a cross-sectional view (see Fig. 3;
an insulating film 9; and
a source electrode 10 that is provided on the insulating film and is electrically connected to the source layer
Fukui does not explicitly teach that:
the insulating film has a plurality of source contact holes intermittently provided in the second direction along the trench gate in a plan view, and is provided on the first main surface in a cross-sectional view and that the source electrode contacts the source layer via the plurality of source contact holes.
However, in analogous art, Shimada teaches in Figs. 15-16, openings H2 intermittently formed in an insulating film 24 so that source electrodes 23 may contact the source 21 therethrough. It would have been obvious to the person of ordinary skill in the art before the time of filing to include the teaching of Shimada to enhance the reliability of the transistor, as taught by Shimada [0042].
Fukui and Shimada do not explicitly teach:
a first metal film that is provided on the source electrode and contains nickel; and
a second metal film that is provided on the first metal film and contains a metal having a lower ionization tendency than ionization tendency of the first metal film (gold), wherein intermittent recesses reflecting shapes of the plurality of source contact holes are provided on a surface of the source electrode on a side opposite to the semiconductor substrate.
However, in analogous art, Koyama teaches in Fig. 1 at least, a nickel film 25 and a gold film 26 over current carrying electrodes 18. It would have been obvious to the person of ordinary skill in the art before the time of filing to include the teaching of Koyama to suppress warpage, as taught by Koyama (abstract).
Regarding Claim 2, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, wherein a shape of each of the plurality of source contact holes in a plan view is a line shape, a rectangular shape, a circular shape (Fig. 15 of Shimada), or a square shape.
Regarding Claim 4, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, further comprising a silicide layer 17 that contains nickel and that makes ohmic connection between the source electrode and at least one of the base layer and the source layer.
Regarding Claim 5, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, further comprising a bottom layer 13 of the second conductivity type provided at a bottom portion of the trench; and
a side layer 12 of the second conductivity type that is provided at a side portion of the trench and electrically connects the bottom layer and the base layer.
Regarding Claim 10, Fukui, Shimada and Koyama teach a power conversion apparatus comprising:
a main conversion circuit that has the silicon carbide semiconductor device according to claim 1 (see above), and converts power that is input and outputs the power;
a drive circuit 602 that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and
a control circuit 603 that outputs a control signal for controlling the drive circuit to the drive circuit.
Regarding Claim 11, Fukui, Shimada and Koyama teach a power conversion apparatus comprising:
a main conversion circuit that has the silicon carbide semiconductor device according to claim 2 (see above), and converts power that is input and outputs the power;
a drive circuit 602 that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and
a control circuit 603 that outputs a control signal for controlling the drive circuit to the drive circuit.
Regarding Claim 13, Fukui, Shimada and Koyama teach a power conversion apparatus comprising:
a main conversion circuit that has the silicon carbide semiconductor device according to claim 4 (see above), and converts power that is input and outputs the power;
a drive circuit 602 that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and
a control circuit 603 that outputs a control signal for controlling the drive circuit to the drive circuit.
Regarding Claim 14, Fukui, Shimada and Koyama teach a power conversion apparatus comprising:
a main conversion circuit that has the silicon carbide semiconductor device according to claim 5 (see above), and converts power that is input and outputs the power;
a drive circuit 602 that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and
a control circuit 603 that outputs a control signal for controlling the drive circuit to the drive circuit.
Claim 3 is rejected under 35 U.S.C. 103 as being unpatentable over Fukui, Shimada and Koyama as applied to claim 1 above, and further in view of WO 2019123601 to Hatta et al. (Hatta).
Regarding Claim 3, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, but do not explicitly teach that the plurality of source contact holes in a plan view is arranged side by side in the first direction and is arranged asymmetrically with respect to the second direction.
However, in analogous art, Hatta teaches in Fig. 5 at least offset source contact regions 12. It would have been obvious to the person of ordinary skill in the art before the time of filing to include the teaching of Hatta as the resistance value in the source contact region 12 is reduced, and the reliability of the MOSFET during large current flow is improved, as taught by Hatta.
Regarding Claim 12, Fukui, Shimada, Koyama and Hatta teach a power conversion apparatus comprising:
a main conversion circuit that has the silicon carbide semiconductor device according to claim 3 (see above), and converts power that is input and outputs the power;
a drive circuit 602 that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and
a control circuit 603 that outputs a control signal for controlling the drive circuit to the drive circuit.
Allowable Subject Matter
Claims 6-9 would be allowable if rewritten to overcome the rejection(s) under 35 U.S.C. 112(b) set forth in this Office action and to include 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:
Regarding Claim 6, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, but do not explicitly teach that one or more first portions on the first main surface side of the base layer and a second portion on a first main surface side of the source layer are adjacent to each other and overlap one of the plurality of source contact holes in a plan view, in context with the rest of the claim. The first and second portions are understood to be 2b and 3a respectively as embodied in Figs. 7-8 and the corresponding text.
Regarding Claim 7, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, but do not explicitly teach that silicon carbide semiconductor device according to claim 6, wherein the two first portions overlap both end portions of one of the plurality of source contact holes in the first direction in a plan view , in context with the rest of the claim. The two first and second portions are understood to be 2a/2b and 3a respectively as embodied in Fig 9 and the corresponding text.
Regarding Claim 8, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, but do not explicitly teach that a side surface of the insulating film in contact with one of the plurality of source contact holes is inclined such that the one of the plurality of source contact holes spreads toward a side opposite to the semiconductor substrate in a cross-sectional view, in context with the rest of the claim.
Regarding Claim 9, Fukui, Shimada and Koyama teach the silicon carbide semiconductor device according to claim 1, but do not explicitly teach that a curved surface is provided between a side surface of the insulating film in contact with one of the plurality of source contact holes and a surface of the insulating film on a side opposite to the semiconductor substrate in a cross-sectional view, in context with the rest of the claim.
Claims 15-18 would be allowable if rewritten or amended to overcome the rejection(s) under 35 U.S.C. 112(b) set forth in this Office action.
Regarding Claim 15, Fukui, Shimada and Koyama teach a power conversion apparatus comprising: a main conversion circuit that has the silicon carbide semiconductor device, and converts power that is input and outputs the power; a drive circuit that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and a control circuit that outputs a control signal for controlling the drive circuit to the drive circuit as explained above, but do not teach a power conversion circuit according to claim 6.
Regarding Claim 16, Fukui, Shimada and Koyama teach a power conversion apparatus comprising: a main conversion circuit that has the silicon carbide semiconductor device, and converts power that is input and outputs the power; a drive circuit that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and a control circuit that outputs a control signal for controlling the drive circuit to the drive circuit, but do not teach a power conversion circuit according to claim 7.
Regarding Claim 17, Fukui, Shimada and Koyama teach a power conversion apparatus comprising: a main conversion circuit that has the silicon carbide semiconductor device according to claim 8, and converts power that is input and outputs the power; a drive circuit that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; anda control circuit that outputs a control signal for controlling the drive circuit to the drive circuit, but do not teach a power conversion circuit according to claim 8.
Regarding Claim 18, Fukui, Shimada and Koyama teach a power conversion apparatus comprising: a main conversion circuit that has the silicon carbide semiconductor device, and converts power that is input and outputs the power; a drive circuit that outputs a drive signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device; and a control circuit that outputs a control signal for controlling the drive circuit to the drive circuit, but do not teach a power conversion circuit according to claim 8.
Conclusion
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/EVREN SEVEN/Primary Examiner, Art Unit 2812