DETAILED ACTION
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 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 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.
This Office Action is in response to Amendments/Remarks filed on December 22, 2025.
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 set forth in Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), that are applied 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.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 1, 13, 16, and 37 are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Application Publication No. 2004/0041229 A1 to Chol et al. (“Chol”) in view of U.S. Patent Application Publication No. 2010/0140628 A1 to Zhang (“Zhang”) and U.S. Patent Application Publication No. 2007/0072352 A1 to Kushiyama et al. (“Kushiyama”). As to claim 1, although Chol discloses an insulated gate bipolar transistor (IGBT) device comprising: an IGBT stack, wherein the IGBT stack includes: an injector region (802); a drift region (804) over the injector region (802); a spreading region (806) over the drift region (804), the spreading region (806) providing a first surface of the IGBT stack opposite the drift region (804) and having a doping concentration (n+) that is greater than a doping concentration (n-) of the drift region (804), wherein the doping concentration (n+) of the spreading region (806) comprises a graduated doping concentration (¶ 0037) which is higher adjacent the first surface than adjacent the drift region (804); a pair of junction implants (808, 810, 812) in the spreading region (806), wherein: the pair of junction implants (808, 810, 812) are separated by a channel (a’) and extend from the first surface of the IGBT stack along a lateral edge of the IGBT stack towards the drift region (804) to a first depth; and a thickness of the spreading region (806) is greater than the first depth; a gate contact (818) and an emitter contact (820) on the first surface of the IGBT stack; and a collector contact (822) on a second surface of the IGBT stack, which is provided by the injector region (802) opposite the drift region (804) (See Fig. 2, Fig. 3, Fig. 5, Fig. 7, ¶ 0014, ¶ 0015, ¶ 0028, ¶ 0031, ¶ 0032, ¶ 0033, ¶ 0037, ¶ 0038, ¶ 0039, ¶ 0040) (Notes: the recited regions and contacts are met by the disclosed relative conductivity types and positions), Chol does not further disclose wherein the IGBT stack is a silicon carbide (SiC) IGBT stack; and a junction field-effect transistor (JFET) implant in the channel and extending from the first surface of the SiC IGBT stack towards the drift region, the JFET implant having a same conductivity type as the drift region and comprising a central portion between the pair of junction implants, and the central portion of the JFET implant having a doping concentration that is greater than both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region, wherein an outermost portion of the JFET implant in a lateral direction is between the pair of junction implants. However, Chol also discloses the IGBT stack is obtained by providing the p-type injector region (802) different from an n-type semiconductor substrate (302) of a MOSFET device (See Fig. 2, Fig. 5, Fig. 7, ¶ 0014, ¶ 0015, ¶ 0028, ¶ 0031, ¶ 0032, ¶ 0033, ¶ 0037, ¶ 0038, ¶ 0039). Zhang does disclose wherein the IGBT stack is a silicon carbide (SiC) IGBT stack (See Fig. 1, ¶ 0003, ¶ 0015, ¶ 0035, ¶ 0038, ¶ 0039, ¶ 0040, ¶ 0042, ¶ 0047, ¶ 0051, ¶ 0061) and Kushiyama does disclose and a junction field-effect transistor (JFET) implant (14) in the channel (under 13) and extending from the first surface (top) of the IGBT stack towards the drift region (2), the JFET implant (14) having a same conductivity type as the drift region (2) and comprising a central portion (at 14) between the pair of junction implants (4), and the central portion (at 14) of the JFET implant (14) having a doping concentration (1E17) that is additionally added in the drift region (2) in the channel (under 13) under the gate contact (13), wherein an outermost portion of the JFET implant (14) in a lateral direction is between the pair of junction implants (4) (See Fig. 3, ¶ 0007, ¶ 0042, ¶ 0043, ¶ 0055, ¶ 0056, ¶ 0058, ¶ 0059). In view of the teachings of Chol, Zhang, and Kushiyama, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the teaching of Chol to have wherein the IGBT stack is a silicon carbide (SiC) IGBT stack; and a junction field-effect transistor (JFET) implant in the channel and extending from the first surface of the SiC IGBT stack towards the drift region, the JFET implant having a same conductivity type as the drift region and comprising a central portion between the pair of junction implants, and the central portion of the JFET implant having a doping concentration that is greater than both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region, wherein an outermost portion of the JFET implant in a lateral direction is between the pair of junction implants because the silicon carbide (SiC) IGBT stack is suitable for high power and high temperature applications with a capability of blocking high voltages, where having the spreading region with the graduated doping concentration above the drift region in the IGBT device improves the switching speed and breakdown voltage (See Chol ¶ 0033, ¶ 0038 and Zhang ¶ 0003, ¶ 0030, ¶ 0034, ¶ 0047). Further, the JFET implant that is selectively formed in the channel under the gate contact and designed independently in the spreading region and between the pair of junction implants can reduce a resistance value under the gate contact without affecting pinch-off voltage (See Kushiyama ¶ 0058, ¶ 0059). As to claim 13, although Chol discloses an insulated gate bipolar transistor (IGBT) device comprising: an IGBT stack, wherein the IGBT stack includes: an injector region (802); a drift region (804) over the injector region (802), the drift region (804) having a different conductivity type than the injector region (802); a spreading region (806) over the drift region (804), the spreading region (806) providing a first surface of the IGBT stack opposite the drift region (804) and having a doping concentration (n+) that is greater than a doping concentration (n-) of the drift region (804), wherein the doping concentration (n+) of the spreading region (806) comprises a graduated doping concentration (¶ 0037) which is higher adjacent the first surface than adjacent the drift region (804); a pair of junction implants (808, 810, 812) in the spreading region (806), wherein: the pair of junction implants (808, 810, 812) are separated by a junction field-effect transistor (JFET) region (a’) and extend from the first surface of the IGBT stack along a lateral edge of the IGBT stack towards the drift region (804) to a first depth; and a thickness of the spreading region (806) is greater than the first depth such that a spreading layer buffer (below junction implants) is between the pair of junction implants (808, 810, 812) and the drift region (804), the spreading layer buffer (below junction implants) having a doping concentration that is greater than the doping concentration of the drift region (804); a gate contact (818) and an emitter contact (820) on the first surface of the IGBT stack; and a collector contact (822) on a second surface of the IGBT stack, which is provided by the injector region (802) opposite the drift region (804) (See Fig. 2, Fig. 3, Fig. 5, Fig. 7, ¶ 0014, ¶ 0015, ¶ 0028, ¶ 0031, ¶ 0032, ¶ 0033, ¶ 0037, ¶ 0038, ¶ 0039, ¶ 0040) (Notes: the recited regions and contacts are met by the disclosed relative conductivity types and positions), Chol does not further disclose wherein the IGBT stack is a silicon carbide (SiC) IGBT stack; the thickness of the spreading region is in a range from one and a half to four times greater than the first depth; and a JFET implant in the JFET region and extending from the first surface of the SiC IGBT stack towards the drift region, the JFET implant having a doping concentration that is greater than both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region, wherein the JFET implant has a same conductivity type as the drift region and does not extend over the pair of junction implants. However, Zhang does disclose wherein the IGBT stack is a silicon carbide (SiC) IGBT stack; the thickness (about 1 µm) of the spreading region (54) is in a range from one and a half to four times greater than the first depth (about 0.5 µm) (See Fig. 2, ¶ 0003, ¶ 0030, ¶ 0033, ¶ 0034, ¶ 0044, ¶ 0047, ¶ 0048). Further, Kushiyama does disclose and a JFET implant (14) in the JFET region (between 4) and extending from the first surface (top) of the IGBT stack towards the drift region (2), the JFET implant (14) having a doping concentration (1E17) that is greater than a doping concentration of the drift region (2) in the channel (under 13) under the gate contact (13), wherein the JFET implant (14) has a same conductivity type as the drift region (2) and does not extend over the pair of junction implants (4) (See Fig. 3, ¶ 0007, ¶ 0042, ¶ 0043, ¶ 0055, ¶ 0056, ¶ 0058, ¶ 0059). In view of the teachings of Chol, Zhang, and Kushiyama, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the teaching of Chol to have wherein the IGBT stack is a silicon carbide (SiC) IGBT stack; the thickness of the spreading region is in a range from one and a half to four times greater than the first depth; and a JFET implant in the JFET region and extending from the first surface of the SiC IGBT stack towards the drift region, the JFET implant having a doping concentration that is greater than both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region, wherein the JFET implant has a same conductivity type as the drift region and does not extend over the pair of junction implants because the silicon carbide (SiC) IGBT stack is suitable for high power and high temperature applications with a capability of blocking high voltages, where having the spreading region with the graduated doping concentration above the drift region in the IGBT device improves the switching speed and breakdown voltage. Further, varying the thickness and/or doping concentration of the spreading region/spreading layer buffer is based on the specific on-resistance, withstand voltage, blocking capability, and static and dynamic characteristics of the device that may affect or be interdependent upon each other (See Chol ¶ 0033, ¶ 0038 and Zhang ¶ 0003, ¶ 0030, ¶ 0034, ¶ 0047). Lastly, the JFET implant that is selectively formed in the channel under the gate contact and designed independently in the spreading region and between the pair of junction implants can reduce a resistance value under the gate contact without affecting pinch-off voltage (See Kushiyama ¶ 0058, ¶ 0059). As to claim 16, Chol in view of Zhang and Kushiyama further discloses wherein the JFET implant (14) is free of overlap with the pair of junction implants (808, 810, 812/4) in a direction perpendicular to the first surface of the SiC IGBT stack (See Chol Fig. 7 and Kushiyama Fig. 3).
As to claim 37, Chol in view of Kushiyama further discloses wherein the JFET implant (14) does not extend over the pair of junction implants (808, 810, 812/4), and wherein the gate contact (818) vertically overlaps a lateral midpoint of the JFET implant (14) (See Chol Fig. 7 and Kushiyama Fig. 3).
Claims 4, 6-7, 18, 23, 31, and 33-34 are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Application Publication No. 2004/0041229 A1 to Chol et al. (“Chol”) in view of U.S. Patent Application Publication No. 2010/0140628 A1 to Zhang (“Zhang”), and U.S. Patent Application Publication No. 2007/0072352 A1 to Kushiyama et al. (“Kushiyama”). As to claim 4, Chol in view of Zhang/Kushiyama further discloses wherein the IGBT device is configured to operate in a front-side injection mode where current transferred between the collector contact (822) and the emitting contact (820) is primarily due to electrons supplied from the emitter contact (820), rather than holes supplied from the injector region (802) (See Chol ¶ 0014, ¶ 0015 and Zhang/Kushiyama). Further regarding the recited limitations above, the claim limitations “wherein the IGBT device is configured to operate in a front-side injection mode where current transferred between the collector contact and the emitting contact is primarily due to electrons supplied from the emitter contact, rather than holes supplied from the injector region” specify an intended use or field of use, and is met by the prior art since it has been held that in device claims, intended use must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. In re Casey, 152 USPQ 235 (CCPA 1967); In re Otto, 136 USPQ 458, 459 (CCPA 1963). A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex Parte Masham, 2 USPQ 2d 1647 (Bd. Pat. App. & Inter. 1987). As to claims 6 and 18, Chol in view of Zhang/Kushiyama further discloses wherein each one of the pair of junction implants (808, 810, 812/18, 20, 22) comprises: a base well (808/18); a source well (810/20); and an ohmic well (812/22), wherein doping concentrations of the base well (808/18), the source well (810/20), and the ohmic well (812/22) are different from one another (See Chol and Zhang ¶ 0034) (Notes: overlapping concentration of ohmic well and the base well). Further, the applicant also has not established the critical nature of the “wherein the doping concentration of the base well, the source well, and the ohmic well are different from one another”. “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the doping concentrations of the base well, the source well, and the ohmic well so that wherein the doping concentration of the base well, the source well, and the ohmic well are different from one another. See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious). As to claim 7, Chol in view of Zhang/Kushiyama further discloses wherein: the gate contact (818/32) partially overlaps and runs between each source well (810/20) in the pair of junction implants (808, 810, 812/18, 20, 22); the emitter contact (820/28) partially overlaps both the source well (810/20) and the ohmic well (812/22) in each one of the pair of junction implants (808, 810, 812/18, 20, 22), respectively, without contacting the gate contact (818/32); and the emitter contact (820/28) has a “U” shape in a cross-sectional view (See Chol and Zhang Fig. 2, ¶ 0034, ¶ 0044) to apply appropriate common bias. As to claim 23, Chol in view of Zhang further discloses wherein the first depth (¶ 0034) is in the range of about 0.3 µm to about 1.5 µm (See Zhang ¶ 0034). As to claim 31, Chol in view of Zhang/Kushiyama further discloses wherein the doping concentration (1E17) of the central portion of the JFET implant (14) is in a range from two times greater to twenty times greater than the doping concentration (1E16) of the at least a portion of the spreading region (806/54), and wherein the JFET implant (14) extends from the first surface of the SiC IGBT stack towards the drift region (804/14/2) to a second depth that is less than or equal to the first depth (See Zhang Fig. 2, ¶ 0048 and Kushiyama Fig. 3, ¶ 0056). As to claim 33, Chol in view of Zhang/Kushiyama further discloses wherein the doping concentration of the spreading region (806/54) adjacent the first surface is in a range from five to ten times greater than the doping concentration of the spreading region (806/54) adjacent the drift region (804/14/2) (See Chol, Zhang Fig. 2, ¶ 0048, and Kushiyama Fig. 3, ¶ 0056) (Notes: the spreading region adjacent the first surface and the JFET implant has a concentration of about 1E17 that is in a range from five to ten times greater than a concentration of the spreading region adjacent the drift region of about 1E16). As to claim 34, Chol in view of Zhang further discloses wherein the doping concentration of the drift region (804/14) is between 1E13 cm-3 and 1E15 cm-3 , and wherein the doping concentration of the spreading region (806/54) is between 5E15 cm-3 and 5E16 cm-3 (See Zhang ¶ 0033, ¶ 0047, ¶ 0048) such that a desired tradeoff in device static and dynamic characteristics is obtained. Further, the applicant also has not established the critical nature of the “in a range from five to ten times greater, wherein a doping concentration of the drift region is between 1E13 cm-3 and 1E15 cm-3, and wherein the doping concentration of the spreading region is between 5E15 cm-3 and 5E16 cm-3.” “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the thickness and/or concentration of the spreading region to obtain a desired tradeoff in device static and dynamic characteristics. See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious).
Claim(s) 24 and 30 are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Application Publication No. 2004/0041229 A1 to Chol et al. (“Chol”), U.S. Patent Application Publication No. 2010/0140628 A1 to Zhang (“Zhang”), U.S. Patent Application Publication No. 2007/0072352 A1 to Kushiyama et al. (“Kushiyama”) as applied to claims 1 and 13 above, and further in view of U.S. Patent Application Publication No. 2011/0101375 A1 to Zhang (“Zhang5”). The teachings of Chol, Zhang, and Kushiyama have been discussed above. As to claim 24, Chol in view of Zhang5 further discloses wherein a width of the SiC IGBT stack is between about 5µm to 15µm (See Zhang5 Fig. 5, Fig. 7, ¶ 0052, ¶ 0054, ¶ 0059) because a smaller device is obtained with a reduced electric field. As to claim 30, Chol in view of Kushiyama and Zhang5 further discloses wherein a width of the channel is between 1 µm to 4 µm, wherein the pair of junction implants (808, 810, 812/4) comprise a pair of base wells (808/4), and wherein the central portion of the JFET implant (14) is between the pair of base wells (808/4) (See Kushiyama Fig. 3 and Zhang5 Fig. 5, Fig. 7, ¶ 0052, ¶ 0054, ¶ 0059) because a smaller device is obtained with a reduced electric field. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have wherein the width of the SiC IGBT stack is between about 5µm to 15µm, wherein a width of the channel is between 1 µm to 4 µm because the width should be optimized based on current crowding factor and resistance of the JFET region and the channel region. Further, present day device is further miniaturized to obtain high density and integration. Thus, it would have been obvious to minimize the device dimension. However, such miniaturization should be balanced with device constraints (See Zhang5 Fig. 5, Fig. 7, ¶ 0052, ¶ 0054, ¶ 0059). Further, the applicant also has not established the critical nature of the “wherein the width of the SiC IGBT stack is between about 5µm to 15µm and wherein a width of the channel is between 1 µm to 4 µm”. “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the width of the SiC IGBT stack to be between about 5µm to 15µm and adjust the width of the channel to be between 1 µm to 4 µm. See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious).
Claim(s) 32 is rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Application Publication No. 2004/0041229 A1 to Chol et al. (“Chol”), U.S. Patent Application Publication No. 2010/0140628 A1 to Zhang (“Zhang”), and U.S. Patent Application Publication No. 2007/0072352 A1 to Kushiyama et al. (“Kushiyama”) as applied to claim 13 above, and further in view of U.S. Patent Application Publication No. 2013/0092978 A1 to Sugawara et al. (“Sugawara”). The teachings of Chol, Zhang, and Kushiyama have been discussed above. As to claim 32, Chol in view of Zhang and Sugawara further discloses wherein a thickness of the spreading layer buffer (34) is in a range from 1.5 µm to 10 µm (See Sugawara Fig. 3, ¶ 0095, ¶ 0101) such that the breakdown voltage is improved. Further, the applicant also has not established the critical nature of the “wherein a thickness of the spreading layer buffer is in a range from 1.5 µm to 10 µm”. “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the thickness of the spreading layer buffer and the concentrations to obtain a desired breakdown voltage and tradeoff in device static and dynamic characteristics . See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious).
Claims 35-36, 38-40, and 42 are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Application Publication No. 2004/0041229 A1 to Chol et al. (“Chol”) in view of U.S. Patent Application Publication No. 2010/0140628 A1 to Zhang (“Zhang”), U.S. Patent Application Publication No. 2013/0092978 A1 to Sugawara et al. (“Sugawara”), and U.S. Patent Application Publication No. 2007/0072352 A1 to Kushiyama et al. (“Kushiyama”). As to claim 35, although Chol discloses a semiconductor device comprising: a drift region (804); a spreading region (806) on the drift region (804), the spreading region (806) having a doping concentration that is greater than a doping concentration of the drift region (804); a pair of junction implants (808, 810, 812) in the spreading region (806) and separated by a channel (a’), the pair of junction implants (808, 810, 812) extending in a first direction from an upper surface of the spreading region (806) towards the drift region (804) to a first depth (See Fig. 2, Fig. 3, Fig. 5, Fig. 7, ¶ 0014, ¶ 0015, ¶ 0028, ¶ 0031, ¶ 0032, ¶ 0033, ¶ 0037, ¶ 0038, ¶ 0039, ¶ 0040) (Notes: the recited regions and contacts are met by the disclosed relative conductivity types and positions), Chol does not further disclose the drift region comprising silicon carbide; and a junction field-effect transistor (JFET) implant in the channel, the JFET implant having a doping concentration that is greater than both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region, wherein a thickness of the spreading region is in a range from one and a half to four times greater than the first depth, such that a thickness of a portion of the spreading region in the first direction between the drift region and a respective one of the pair of junction implants is at least 1.5 µm. However, Zhang does disclose the drift region (14) comprising silicon carbide; wherein a thickness (about 1 µm) of the spreading region (54) is in a range from one and a half to four times greater than the first depth (about 0.5 µm) (See Fig. 2, ¶ 0003, ¶ 0030, ¶ 0033, ¶ 0034, ¶ 0044, ¶ 0047, ¶ 0048) and Sugawara does disclose wherein a thickness (2.4 µm) of the spreading region (5) is in a range from one and a half to four times greater than the first depth (0.6 µm), such that a thickness (1.8 µm) of a portion of the spreading region (5) in the first direction between the drift region (3, 23) and a respective one of the pair of junction implants (6, 7, 8) is at least 1.5 µm (See Fig. 1, Fig. 2, ¶ 0033-¶ 0036, ¶ 0068, ¶ 0077). Further, Kushiyama does disclose and a junction field-effect transistor (JFET) implant (14) in the channel (under 13), the JFET implant (14) having a doping concentration (1E17) that is greater than the doping concentration of the drift region (2) in the channel (under 13) under the gate contact (13) (See Fig. 3, ¶ 0007, ¶ 0042, ¶ 0043, ¶ 0055, ¶ 0056, ¶ 0058, ¶ 0059). In view of the teachings of Chol, Zhang, Sugawara, and Kushiyama, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the teaching of Chol to have the drift region comprising silicon carbide; and a junction field-effect transistor (JFET) implant in the channel, the JFET implant having a doping concentration that is greater than both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region, wherein a thickness of the spreading region is in a range from one and a half to four times greater than the first depth, such that a thickness of a portion of the spreading region in the first direction between the drift region and a respective one of the pair of junction implants is at least 1.5 µm because the silicon carbide is suitable for high power and high temperature applications with a capability of blocking high voltages, where having the spreading region with the graduated doping concentration above the drift region in the semiconductor device improves the switching speed and breakdown voltage. Further, varying the thickness and/or doping concentration of the spreading region and the first depth is based on the specific on-resistance, withstand voltage, blocking capability, and static and dynamic characteristics of the device that may affect or be interdependent upon each other, where the concentration of electric field around a corner of the junction implants is prevented to increase the breakdown voltage (See Chol ¶ 0033, ¶ 0038, Zhang ¶ 0003, ¶ 0030, ¶ 0034, ¶ 0047, and Sugawara ¶ 0077). Lastly, the JFET implant that is selectively formed in the channel under the gate contact and designed independently in the spreading region and between the pair of junction implants can reduce a resistance value under the gate contact without affecting pinch-off voltage (See Kushiyama ¶ 0058, ¶ 0059). Further, the applicant also has not established the critical nature of the “in a range from one and a half to four times greater than the first depth, such that a thickness of a portion of the spreading region in the first direction between the drift region and a respective one of the pair of junction implants is at least 1.5 µm, the doping concentrations of the drift region, the spreading region, and the JFET implant”. “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the thickness of the spreading region and the first depth so that the thickness of the spreading region is in a range from one and a half to four times greater than the first depth, such that a thickness of a portion of the spreading region in the first direction between the drift region and a respective one of the pair of junction implants is at least 1.5 µm and select the appropriate doping concentrations to obtain desired characteristics. See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious). As to claim 36, Chol in view of Zhang further discloses wherein: the doping concentration of the drift region (804/14) is between 1E13 cm-3 and 1E15 cm-3; the doping concentration of the spreading region (806/54) is between 5E15 cm-3 and 5E16 cm-3; and the doping concentration of the JFET implant (14) is between 1E16 cm-3 and 1E17 cm-3 (See Zhang ¶ 0033, ¶ 0048 and Kushiyama ¶ 0056). Further, the applicant also has not established the critical nature of the “in a range from one and a half to four times greater, the doping concentrations of the drift region, the spreading region, and the JFET implant”. “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the thickness of the spreading region and the first depth so that the thickness of the spreading region is in a range from one and a half to four times greater than the first depth and select the appropriate doping concentrations to obtain desired characteristics. See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious). As to claim 38, Chol in view of Kushiyama further discloses wherein the JFET implant (14) has a same conductivity type as the drift region (2), is directly on the spreading region (806), and is bounded between the pair of junction implants (808, 810, 812/4) (See Chol Fig. 7 and Kushiyama Fig. 3, ¶ 0055, ¶ 0056). As to claim 39, Chol in view of Sugawara further discloses wherein a doping concentration of the portion of the spreading region (806/5) that is at least 1.5 µm thick is substantially constant or decreases towards the drift region (804/23), and wherein the portion of the spreading region (806/5) that is at least 1.5 µm thick shares a first interface with the drift region (804/23) and a second interface with the respective one of the pair of junction implants (808, 810, 812/6) (See Chol Fig. 7 and Sugawara Fig. 2). As to claim 40, Chol in view of Kushiyama further discloses wherein the JFET implant (14) has a same conductivity type as the drift region (804/2) and does not extend over the pair of junction implants (808, 810, 812/4) (See Chol Fig. 7 and Kushiyama Fig. 3, ¶ 0055, ¶ 0056). As to claim 42, Chol in view of Zhang and Sugawara further discloses wherein the portion of the spreading region (806/54/5) that is at least 1.5 µm thick is directly on a portion of the drift region (804/14/23) having a first doping concentration that is less than a second doping concentration of the portion of the spreading region (806/54/5) (See Chol ¶ 0037, Zhang, and Sugawara Fig. 2).
Claim(s) 41 and 43 are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Application Publication No. 2004/0041229 A1 to Chol et al. (“Chol”), U.S. Patent Application Publication No. 2010/0140628 A1 to Zhang (“Zhang”), U.S. Patent Application Publication No. 2013/0092978 A1 to Sugawara et al. (“Sugawara”), and U.S. Patent Application Publication No. 2007/0072352 A1 to Kushiyama et al. (“Kushiyama”) as applied to claims 1 and 35 above, and further in view of U.S. Patent Application Publication No. 2004/0119076 A1 to Ryu (“Ryu”) and U.S. Patent Application Publication No. 2013/0092978 A1 to Sugawara et al. (“Sugawara”). The teachings of Chol, Zhang, Sugawara, and Kushiyama have been discussed above. As to claim 41, although Chol does not specifically disclose wherein the thickness of the spreading region (54) is in a range from one and a half to four times greater than the first depth and is at least 2.0 µm greater than the first depth (See Chol Fig. 7), Zhang does disclose wherein the thickness of the spreading region (54) is in a range from one and a half to four times greater than the first depth (See Fig. 2, ¶ 0034, ¶ 0047, ¶ 0048) and Sugawara discloses the thickness of the spreading region (5) may be at most 6.2 µm (See ¶ 0034) and Ryu discloses the first depth may be about 1.2 µm (See ¶ 0042). In view of the teachings of Zhang, Sugawara, and Ryu, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have wherein the thickness of about 4.8 µm of the spreading region is in a range from one and a half to four times greater than the first depth of about 1.2 µm and is at least 2.0 µm greater than the first depth because the thicknesses/depths are selected to provide a desired tradeoff in device static and dynamic characteristics (See Zhang ¶ 0047, Sugawara, and Ryu). As to claim 43, although Chol does not specifically disclose wherein the thickness of the spreading region is at least 2.0 µm greater than the first depth, Zhang does disclose wherein the thickness of the spreading region (54) is in a range from one and a half to four times greater than the first depth (See Fig. 2, ¶ 0034, ¶ 0047, ¶ 0048) and Sugawara discloses the thickness of the spreading region (5) may be at most 6.2 µm (See ¶ 0034) and Ryu discloses the first depth may be about 1.2 µm (See ¶ 0042). In view of the teachings of Zhang, Sugawara, and Ryu, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have wherein the thickness of the spreading region of about 4.8 µm is at least 2.0 µm greater than the first depth of about 1.2 µm because the thicknesses/depths are selected to provide a desired tradeoff in device static and dynamic characteristics (See Zhang ¶ 0047, Sugawara, and Ryu). Further, the applicant also has not established the critical nature of the “wherein the thickness of the spreading region is in a range from one and a half to four times greater than the first depth and is at least 2.0 µm greater than the first depth”. “The law is replete with cases in which the difference between the claimed invention and the prior art is some range or other variable within the claims….In such a situation, the applicant must show that the particular range is critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range.” In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir.1990). Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention was made to have various ranges. It would also have been obvious to one of ordinary skill in the art at the time the invention was made to discover the optimum or workable ranges by routine experimentations to adjust the thickness of the spreading region and the first depth and select the appropriate doping concentrations to obtain desired characteristics. See also In re Huang, 40 USPQ2d 1685, 1688 (Fed. Cir. 1996) (claimed ranges of a result effective variable, which do not overlap the prior art ranges, are unpatentable unless they produce a new and unexpected result which is different in kind and not merely in degree from the results of the prior art). See also In re Boesch, 205 USPQ 215 (CCPA) (discovery of optimum value of result effective variable in known process is ordinarily within skill of art) and In re Aller, 105 USPQ 233 (CCPA 1955) (selection of optimum ranges within prior art general conditions is obvious).
Allowable Subject Matter
Claim 8 is objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
Response to Arguments
Applicant's arguments with respect to claim 1, 13, and 35 have been considered but are moot in view of the new ground(s) of rejection.
Although Applicants argue Kushiyama fails to teach the impurity region 14 has a greater doping concentration than at least a portion of a spreading region, it is noted that impurity region 14 of Kushiyama is combined/incorporated into Chol to provide the JFET implant in the channel such that the additionally provided JFET implant has a doping concentration that is greater than “both the doping concentration of the drift region and a doping concentration of at least a portion of the spreading region”.
Further, although [0037] of Sugawara discloses the “0.3 µm”, [0033]-[0035] clearly disclose different ranges for the nCELu5 and the p body region 6, where the thickness of the nCELu 5 maybe at least 0.9 µm and at most 6.2 µm, the depth of the p body region 6 may be 0.3 µm or 0.6 µm, and the thickness between nCELu 5 and nCELb 4/p body region 6 is from 0.3 µm to 2.6 µm. Thus, when the depth of the p body region 6 is 0.6 µm and the thickness of the nCELu 5 is 2.4 µm, which fall within the disclosed ranges, “the thickness of the spreading region is in a range from one and a half to four times greater than the first depth, such that a thickness of a portion of the spreading region in the first direction between the drift region and a respective one of the pair of junction implants is at least 1.5 µm” is fully met by Sugawara.
Furthermore, although the separation hole 12 is formed in a center of a gate electrode 13, the impurity region 14 is formed between the pair of junction implants (4). Thus, when incorporating the impurity region into Chol, the gate contact of Chol “vertically overlaps a lateral midpoint of the JFET implant”.
Moreover, although the layer 5 is directly on an n+ layer 4 having a greater doping concentration than the layer 5”, FIG. 2 clearly shows the lower doped drift region (23).
Lastly, in response to applicant's arguments against the references individually, one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986).
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). 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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/DAVID CHEN/Primary Examiner, Art Unit 2815
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