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 species X, claims 8 and 10, in the reply filed on 01/7/2026 is acknowledged.
Claims 1-7, 9, and 11-19 are withdrawn from further consideration pursuant to 37 CFR 1.142(b) as being drawn to a nonelected species, there being no allowable generic or linking claim. Election was made without traverse in the reply filed on 01/07/2026.
Drawings
The drawings are objected to as failing to comply with 37 CFR 1.84(p)(5) because they include the following reference characters 701, 701’ – 724, 724’ not mentioned in the description: none of the reference numbers of elected species X, Figs 7A-7B, are in mentioned in the instant disclosure. Corrected drawing sheets in compliance with 37 CFR 1.121(d), or amendment to the specification to add the reference character(s) in the description in compliance with 37 CFR 1.121(b) 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. 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 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.
Claims 8 and 10 are rejected under 35 U.S.C. 103 as being unpatentable over Baliga, U.S. Pat. Pub. 2002/0036319, hereafter Baliga, in view of Su et. al., U.S. Pat. Pub. 2021/0020778, hereafter Su.
Regarding claim 1, Baliga discloses (see annotated Fig. 3B) a shielded gate trench (SGT) device comprising a plurality of unit cells (par. [0030], [0031]) with each unit cell in an active area comprising:
an epitaxial layer (par. [0010]) [112] of a first conductivity type (N-type) on a substrate [114];
at least one gate trench [120a] (par. [0011]) surrounded by a source region [118] of said first conductivity type (N-type) encompassed in a body region [116], [119] of a second conductivity type (P-type); said gate trench being filled with a gate electrode [127] and a shielded gate electrode [128a]; said shielded gate electrode being insulated from said epitaxial layer by a first insulating film [125], said gate electrode being insulated from said epitaxial layer by a gate oxide (par. [0056]), said shielded gate electrode [128a] and said gate electrode [127] being insulated from each other by an (Inter-polysilicon Oxide) IPO film, said gate oxide surrounding said gate electrode and having a less thickness than a thickness of said first insulating film (par. [0011]);
a P-shield zone of said second conductivity type for gate oxide electric-filed reduction adjoining a lower surface of said body region [116] and being apart from said gate trench [120a]; and said body region [116] and said source region [118] being shorted to a source metal [128b] through source contacts [119].
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Baliga fails to explicitly disclose a SiC shielded gate trench (SGT) device comprising at least one N-shield zone of said first conductivity type for gate oxide protection disposed at a position deeper than said shielded gate electrode in said epitaxial layer with a doping concentration higher than a doping concentration of said epitaxial layer.
However, Su discloses (Fig. 1B, par. [0034]) a shielded gate trench (SGT) device comprising at least one N-shield zone [118] of said first conductivity type for gate oxide protection disposed at a position deeper than said shielded gate electrode [106], [108] in said epitaxial layer with a doping concentration higher than a doping concentration of said epitaxial layer (par. [0054], the doping concentration is much higher than the epitaxial layer).
While neither reference specifically teaches Silicon carbide, it is a well known and widely used material for power MOSFET or IGBT devices such as ones disclosed by Baliga and Su.
It would have been obvious to one having ordinary skill in the art prior to effective filing date of the instant application to include doped regions of Su in the epitaxial layer in the device of Baliga because Su teaches (abstract, last sentence) that such a modification improves the breakdown voltage.
It would have been obvious to one having ordinary skill in the art prior to effective filing date of the instant application to use SiC material because SiC is a well known and widely used wide band gap semiconductor in power devices.
Regarding claim 10, Baliga in view of Su discloses everything as applied above. Baliga further discloses (par. [0052], “step graded” drift region corresponds to multiple stepped epitaxial (MSE) layers with different doping concentrations as claimed)
wherein said epitaxial layer has multiple stepped epitaxial (MSE) layers with different doping concentrations decreasing stepwise in a direction from said substrate to a top surface of said epitaxial layer, wherein each of said MSE layers has a uniform doping concentration as grown.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to VICTOR V BARZYKIN whose telephone number is (571)272-0508. The examiner can normally be reached Monday-Friday, 9am-5pm.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, BRITT HANLEY can be reached at (571)270-3042. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/VICTOR V BARZYKIN/ Examiner, Art Unit 2893
/Britt Hanley/ Supervisory Patent Examiner, Art Unit 2893
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