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 .
Drawing Objections
Examiner withdraws the drawing objection as figure 1 is now labeled as prior art.
Specification Objections
Examiner withdraws the specification objection based upon the amendment to the specification.
Claim Rejections - 35 USC § 102
The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form the basis for the rejections under this section made in this Office action:
A person shall be entitled to a patent unless –
(a)(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention.
(a)(2) the claimed invention was described in a patent issued under section 151, or in an application for patent published or deemed published under section 122(b), in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention.
Claim(s) 8, and 10-12 is/are rejected under 35 U.S.C. 102(a)(1) and (a)(2) as being anticipated by Mirchandani et al. (US 9,673,318 B1) (“Mirchandani”).
Regarding claim 8, Mirchandani teaches at least in figure 3:
a front side and a rear side (examiner understands the front side to be a top side, and the rear side to be the bottom side based upon figure 2; the top side is the top of 338, the bottom side is bottom of 340),
the front side (top of 338) being situated opposite from the rear side (bottom of 340);
a drift region (304) that includes a first doping (doped with n-type) with a first charge carrier type (n-type);
a body region (306a-c and 342a-c, collectively “A”) that includes a second doping (doped with p-type) with a second charge carrier type (p-type),
the body region (A) being situated on the drift region (304);
trenches that extend, starting from the front side, perpendicularly into the drift region (the trenches are 316); and
first areas (326) and second areas (336) are situated between the trenches (316),
the first areas (326) being situated centrally between the trenches (316), and
the second areas (336) being situated between the first areas (326) and the trenches (316),
the first areas (326) and the second areas (336), starting from the body region (A), extending perpendicularly into the drift region (326 and 336 so extend),
the first areas (326/322) including a third doping (doped with p-type)with the second charge carrier type (p-type), and
the second areas (336) including the first doping (doped with n-type) with the first charge carrier type (n-type),
the second doping (A comprises P+ doping) and the third doping being different (322 does not comprise P+ doping) (A and 322 have different doping).
Regarding claim 10, Mirchandani teaches at least in figure 3:
wherein a field plate (318) is situated within each of the trenches (316).
Regarding claim 11, Mirchandani teaches at least in figure 3:
wherein the first areas (322) have a first depth (322 has a depth) that corresponds to a second depth of the trenches (316 has a second depth) (each of the depths correspond to each each other) in the drift region (304).
Regarding claim 12, Mirchandani teaches at least in figure 3:
wherein the first charge carrier type is n and the second charge carrier type is p (this limitation is shown in claim 8).
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.
Claim(s) 9, and 14 is/are rejected under 35 U.S.C. 103 as being unpatentable over Mirchandani, in view of Saito (US 2008/0135930 A1) (“Saito”).
Regarding claim 9, Mirchandani does not teach:
wherein the third doping within the first areas has a gradual profile,
the third doping, starting from the body region, decreasing in a direction of the drift region.
Saito teaches at least in figure 1:
wherein the third doping (p-type doping in 4) within the first areas (where 4 is located) has a gradual profile (figure 1 on the right shows the p-pillar concentration with a gradual profile),
the third doping (p-type doping in 4), starting from the body region (5), decreasing in a direction of the drift region (this is shown in figure 1 on the right).
It would have been obvious for one of ordinary skill in the art to combine the references and use the doping profile of Saito in the device of Mirchandani before the effective filing date of the current application because 1) Mirchandani is silent with respect to the doping profile, and 2) Saito teaches that by doping the p-pillar in this manner one of ordinary skill in the art could gain the following benefits:
the electric field peak can be positioned in the vicinity of the center of the trench along the depth direction. Hence occurrence of negative resistance at the time of avalanche breakdown can be prevented, and high avalanche withstand capability can be achieved. Furthermore, by decreasing the electric field at the trench bottom, hole generation due to avalanche breakdown can be prevented, and hence high reliability can be achieved. Thus, according to this embodiment, a power MOSFET having low ON resistance and high reliability can be obtained.
¶ 0051.
Thus it would have been obvious for one of ordinary skill in the art to combine the references to gain the above described benefits.
Regarding claim 14, Saito teaches at least in figure 1:
wherein a ratio of an average value of the third doping (the doping in the p-column 21) to an average value of the first doping (doping in the drift region 3) is in a range of 0.1 to 10 (as can be seen in the right figure 1 the average doping of the drift region (second doping) to the average doping in the p-column (third doping) is a result effective variable based upon how much doping one want in the p-column and how much doping one wants in the drift region to position the electric filed in relation to the drift region, thereby controlling where hole generation is due to avalanche breakdown. Therefore, with respect to the limitations of this claim, because the general conditions are disclosed in the prior art is it is not inventive to discover the optimum or workable ranges by routine experimentation. See In re Aller, 220 F.2d 454, 456, 105 USPQ 233 (CCPA 1955). Thus optimization of the claim would be obvious to one of ordinary skill in the art.
Claim(s) 13 is/are rejected under 35 U.S.C. 103 as being unpatentable over Mirchandani.
Regarding claim 13, Mirchandani teaches at least in figure 3:
wherein each of the first areas (322) has a first width (width of 322) and each of the second areas (336) has a second width (width of 336),
Mirchandani does not expressly teach:
a ratio of the first width to the second width being in a range of 0.1 to 10.
However, Mirchandani teaches that the width of 322 and 336 are result effective variables. Mirchandani teaches that the entire width 334 between trenches 316 must be big enough to meet the minimum size requirements for the process being using to form the body/source contact 338, and form a void free metal fill contact. Col. 9 at lines 26-51. Further, by forming the p-column 322 one can achieve a charge balancing effect, col. 9 at lines 5-4, and at the same time it reduces the size of the mesa region 336, Col. 9 at lines 26-51. This is important as the reduction of the mesa region can lead to reducing the cell pitch between trenches in the device. Col. 1 at lines 25-43. Further, by optimizing the size of the mesa region, and the p-column width one can reduce the mesa region, and thereby reduce the cell pitch, allowing more devices in the same given die area, and allowing a higher doping concentration in the drift region to lower Rdson. Id. Thus, the ratio of the first width to the second width is a result effective variable based upon the width necessary to form the source contact, and the min width one can form the mesa region, along with the desired Rdson and cell pitch one of ordinary skill in the art is designing the device for. Therefore, with respect to the limitations of this claim, because the general conditions are disclosed in the prior art is it is not inventive to discover the optimum or workable ranges by routine experimentation. See In re Aller, 220 F.2d 454, 456, 105 USPQ 233 (CCPA 1955). Thus optimization of the claim would be obvious to one of ordinary skill in the art.
For completeness the width of the p-column is the width of the contact 334 minus the width of the mesa region 336.
Response to Arguments
Applicant's arguments filed January 5, 2026 have been fully considered but they are not persuasive.
Applicant asserts the prior art does not teach:
the first areas (326) being situated centrally between the trenches (316), and
the second areas (336) being situated between the first areas (326) and the trenches (316),
the first areas (326) and the second areas (336), starting from the body region (A), extending perpendicularly into the drift region (326 and 336 so extend).
Applicant states the prior art does not teach this limitation because 322 is not between two trenches 316.
Examiner respectfully disagrees for the reasons given the analysis of the claim above.
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/VINCENT WALL/Primary Examiner, Art Unit 2898