Attorney Docket Number: 01_4342
Filing Date: 11/30/2023
Claimed Foreign Priority Date: 01/13/2023 (JP2023-003853)
Inventor: Noborio
Examiner: Thomas McCoy
DETAILED ACTION
This Office action responds to the application filed 11/30/2023.
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 . In the event the determination of the status of the
application as to 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 a 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.
Claim Interpretation
Claim 1 reads “…a plurality of trench gate structures, each of which having a trench extending…” which will be interpreted as “… a plurality of trench gate structures, wherein each trench gate structure has a trench extending…”.
Claim Objections
Claim 1 is objected to because of the following informalities: a portion of “…an impurity layer of the first conductivity type or the second conductivity type formed opposite to the base layer through the drift layer…” is unclear and not previously shown or described. For the purposes of examination, the line will be construed to recite “…an impurity layer of the first conductivity type or the second conductivity type formed opposite to the base layer relative to the drift layer…”. Appropriate correction is required.
Claim Rejections - 35 USC § 103
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.
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 1-3 are rejected under 35 U.S.C. 103 as being unpatentable over Naito (US 20180082996 A1) in view of Kachi (US 20180019160 A1).
Regarding claim 1, Naito (see, e.g., fig.3) shows most aspects of the instant invention including a semiconductor device comprising:
A drift layer (e.g., drift region 18) having a first conductivity type (see, e.g., paragraph 74 “…(N-)-type drift region 18 …”);
A base layer (e.g., base region 14) having a second conductivity type (see, e.g., fig. 3 or paragraph 73 “A (P-)-type base region 14 is formed...”);
An impurity layer (e.g., buffer region 20) of the first conductivity type (e.g., (N-)-type, see fig. 3) formed opposite to the base layer (e.g., base region 14) relative to the drift layer (e.g., drift region 18);
A plurality of trench gate structures (e.g., plurality of trench gate portions 40 + dummy trench portions 30), wherein each trench gate structure (e.g., individual trench gate portion 40) has a trench (see, e.g., trench configuration of trench gate portion 40/30 within fig. 3) extending through the base layer (e.g., base region 14) and having a longitudinal direction (e.g., vertical direction of fig. 3) crossing a stacking direction of the drift layer (e.g., drift region 18) and the base layer (e.g., base region 14), a gate insulating film (e.g., insulating films 42 and 32) formed on a wall surface of the trench, and a gate electrode (e.g., gate conductive portions 44 and 34) formed on the gate insulating film (e.g., insulating films 42 and 32);
A first impurity region (e.g., emitter 12) of the first conductivity type (see, e.g., paragraph 59 “…the emitter region 12 is of (N+)-type”) formed on a surface layer portion of the base layer (e.g., base region 14) and having an impurity concentration higher (see, e.g., paragraph 17 “The semiconductor device may further include a drift region which is provided below the base region and has a lower impurity concentration than the emitter region”) than that of the drift layer (e.g., drift region 18);
A second impurity region (e.g., contact region 15 (see fig. 1, noting fig. 3 is a cross section of fig. 1)) of the second conductivity type (see, e.g., paragraph 59 “In the present example, the contact region 15 is of (P+)-type”) formed on a surface layer portion of the base layer (e.g., base region 14) and having an impurity concentration higher (see, e.g., paragraph 59 “The contact region 15, which is of the second conductivity type and has a higher impurity concentration than the base region 14, is formed in the front surface of the base region 14…”);
A first electrode (e.g., emitter electrode 52) electrically connected (see, e.g., paragraph 61 “The emitter electrode 52 is connected to the emitter region 12 and the contact region 15…”) to the first impurity region (e.g., emitter 12) and the second impurity region (e.g., contact region 15);
A second electrode (e.g., collector electrode 24) electrically connected to the impurity layer (e.g., buffer region 20);
The first impurity region (e.g., emitter 12) and the second impurity region (e.g., contact region 15) are alternately formed along the longitudinal direction of the trench (see, e.g., figs 1 or 2, noting that fig. 3 and fig. 2 are cross sections of fig. 1);
The second impurity region (e.g., contact region 15), which is viewed in the stacking direction of the drift layer (e.g., drift region 18) and the base layer (e.g., base region 14), has a first contact side (see, e.g., annotated fig. 1 or fig. 2 of Naito) in contact with a first trench (e.g., left-side trench structure 40) in a lateral direction intersecting the longitudinal direction (e.g., vertical direction), the first contact side (see, e.g., annotated fig. 1) having a predetermined length and two boundaries (e.g., left-side top and bottom contact points), and a second contact side (see, e.g., annotated fig. 1) in contact with a second trench (e.g., right-side dummy trench structure 30) adjacent to the first trench (e.g., left-side trench structure 40) in the lateral direction, the second contact side (see, e.g., annotated fig. 1) having a predetermined length and two boundaries (e.g., right-side top and bottom contact points).
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Annotated Fig. 1
Naito (see, e.g., fig. 3), however, fails to show a first linear portion is defined to extend from one of the boundaries of the first contact side toward the second trench, a second linear portion is defined to extend from the other of the boundaries of the first contact side toward the second trench, a third linear portion is defined to extend from one of the boundaries of the second contact side toward the first trench, a fourth linear portion is defined to extend from the other of the boundaries of the second contact side toward the first trench, one of a first angle between the first trench and the first linear portion and a second angle between the first trench and the second linear portion is less than 90° and the other angle is less than or equal to 90°, and one of a third angle between the second trench and the third linear portion and a fourth angle between the second trench and the fourth linear portion is less than 90°, and the other angle is less than or equal to 90°.
Kachi (see, e.g., fig. 37), in a similar device to Naito, teaches an impurity region (e.g., p-type region SJ2) has a first linear portion (see, e.g., annotated fig. 2) that is defined to extend from one of the boundaries of a first contact side (see, e.g., annotated fig. 2) toward a second trench (see, e.g., annotated fig. 2), a second linear portion (see, e.g., annotated fig. 2) is defined to extend from the other of the boundaries (e.g., bottom left boundary of relevant n-type source region in annotated fig. 2) of the first contact side (see, e.g., annotated fig. 2) toward the second trench (see, e.g., annotated fig. 2), a third linear portion (see, e.g., annotated fig. 2) is defined to extend from the other of the boundaries of the second contact side (see, e.g., annotated fig. 2) toward the first trench (see, e.g., annotated fig. 2), a fourth linear portion (see, e.g., annotated fig. 2) is defined to extend from the other of the boundaries of the second contact side (see, e.g., annotated fig. 2) toward the first trench (see, e.g., annotated fig. 2), one of a first angle between the first trench (see, e.g., annotated fig. 2) and the first linear portion (see, e.g., annotated fig. 2) and a second angle between the first trench (see, e.g., annotated fig. 2) and the second linear portion (see, e.g., annotated fig. 2) is less than 90° (see, e.g., annotated fig. 3 – note that the angle is substantially more acute than a right-angle) and the other angle is less than or equal to 90° (note that angle between linear portion and trench is substantially acute, thus less than 90° (and note the structure is structurally symmetrical, thus the angles on the other side are identical)), and one of a third angle between the second trench (see, e.g., annotated fig. 3) and the third linear portion (see, e.g., annotated fig. 2) and a fourth angle between the second trench (see, e.g., annotated fig. 2) and the fourth linear portion (see, e.g., annotated fig. 2) is less than 90° (see, e.g., annotated fig. 3 – note that the angle is substantially more acute than a right-angle) and the other angle is less than or equal to 90° (note that angle between linear portion and trench is substantially acute, thus less than 90° (and note the structure is structurally symmetrical, thus the angles on the other side are identical)).
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Annotated Fig. 2
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Annotated Fig. 3
Accordingly, it would have been obvious to one of ordinary skill in the art at the time of filing the invention to include the impurity region geometry configuration of Kachi within the impurity regions of Naito, in order to optimize performance and space, and increase the total contact area of the impurity region away from the interface, expanding the amount of area available for current flow in the center of the region between trenches.
Regarding claim 2, Kachi (see, e.g., fig. 37) teaches a collection of a first, second, third, and fourth angle (see, e.g., annotated fig. 3) that can be defined as θ1, θ2, θ3, and θ4 respectively, which satisfies a formula of (1/tanθ1 + 1/tanθ2) = (1/tanθ3 + 1/tanθ4) (e.g., note that all of the angles are equivalent, as the trenches are parallel and the impurity regions laid out evenly between them – and (1/x + 1/x) = (1/x + 1/x)).
Accordingly, it would have been obvious to one of ordinary skill in the art at the time of filing the invention to include the equivalent and symmetric layout of Kachi (thus providing equivalent angles between the trenches and impurity linear portions) within the layout of Naito in view of Kachi, in order to refrain from altering the current functionality into an asymmetric current configuration between the trenches. Note that Naito’s impurity regions are also laid out symmetrically between the trenches.
Regarding claim 3, Kachi (see, e.g., fig. 37) teaches wherein one of the first angle (see, e.g., first angle in annotated fig. 3) and the second angle (see, e.g., second angle in annotated fig. 3) is equal to one of the third angle (see, e.g., third angle in annotated fig. 3) and the fourth angle (see, e.g., fourth angle in annotated fig. 3).
Accordingly, it would have been obvious to one of ordinary skill in the art at the time of filing the invention to include the equivalent angles of Kachi within the configuration of Naito in view of Kaito for the reasons listed above, which are considered to be relevant here (see, e.g., paragraphs 6-7 regarding claim 2).
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner
should be directed to Thomas McCoy at (571) 272-0282 and between the hours of 9:30 AM to 6:30 PM
(Eastern Standard Time) Monday through Friday or by e-mail via Thomas.McCoy@uspto.gov. If attempts
to reach the examiner by telephone are unsuccessful, the examiner's supervisor, Wael Fahmy, can be
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/THOMAS WILSON MCCOY/ Examiner, Art Unit 2814
/WAEL M FAHMY/Supervisory Patent Examiner, Art Unit 2814