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 .
Response to Amendment
This Office Action is in response to Applicant’s Amendment filed on March 10, 2026. Claim 52 has been amended. No new claims have been added. Claims 6, 14, 16-38, 41 and 53-59 have been canceled. Claims 5 and 11 have been withdrawn. Currently, claims 1-4, 7-10, 12-13, 15, 39-40, 42—52 and 60-62 are pending.
Applicant’s amendment to claim 52 successfully overcomes the objection to claim 52 set forth in the previous Office Action.
Response to Arguments
Applicant's arguments filed on March 10, 2026 have been fully considered but they are not persuasive.
The Applicant argues that, “Applicant respectfully notes that in its description of Fig. 5 at paragraphs 0050-0055, Jelinek makes no indication regarding the implant energies actually used to produce the illustrated implant profile. Thus, it is impossible to tell from the description of Fig. 5 what implant energies were actually used to produce the implant profile illustrated therein….The description of Fig. 5 in Jelinek indicates that: The vertical distribution profile 505 represents a first interval phosphorous implantation process. [para. 0051]…. The vertical distribution profile 510 represents a second interval nitrogen implantation process. [para. 0051]… Note that there is no description in the discussion of Fig. 5 in Jelinek 106 of the actual implant energies that were used. Thus, the explanation in the Office Action quoted above ["Nitrogen is implanted at a high energy such as 1500keV, or any energy exceeding 300keV. ...Subsequently, phosphorous is implanted using a lower energy, approximately 800-120keV."] is based on conjecture and is not supported by the actual disclosure of Jelinek 106.”
The Examiner respectfully disagrees with the Applicant’s analysis. The Applicant is selectively ignoring the broader description of the invention and focusing on a narrow interpretation of Figure 5 that is contrary to the overall teachings of Jelinek 106. The Applicant, in their arguments, acknowledges that Figure 5 of Jelinek 106 teaches a vertical distribution profile 505 representing a phosphorous implantation process and a vertical distribution profile 510 representing a nitrogen implantation process. However, the Applicant attempts to detach these profiles from the corresponding textual description of the process. Jelinek 106 clearly defines the implantation energies for phosphorous, approximately 800-120keV (see e.g., paras [0049]), and nitrogen, exceeding 300keV (see e.g., paras [0049], [0077]), which would be recognized as applicable to the profiles shown in Figure 5. A person of ordinary skill in the art would interpret the described implantation processes and the vertical distribution profiles not as disparate elements but as a unified teaching.
Therefore, the Examiner maintains that the combination of the profile description in Figure 5 and the explicit energy parameters in the specification provide a sufficient basis for rejection.
The Applicant further argues, “In contrast, at paragraph 0046, Jelinek 106 expressly teaches that the second implant interval is performed at a lower implant energy than the first implant interval: a first interval of the implantation is first performed with a first implantation energy and a second interval is performed with a second implantation energy less than the first implantation energy to avoid reducing the achievable maximum penetration depth significantly by the crystal damage generated during the first ion implantation." Thus, a skilled person would understand that the "first interval" referenced in the description of Fig. 5 was performed at a higher implantation energy than the "second interval" referenced in the description of Fig. 5. Moreover, Jelinek 106 expressly teaches that the reason for using a lower implant energy for the second interval is not to position the second channeled peak shallower than the first channeled peak, but instead is "to avoid reducing the achievable maximum penetration depth significantly by the crystal damage generated during the first ion implantation." Accordingly, the "second interval" implantation process of Jelinek must be performed after the "first interval" implantation process, and Fig. 5 of Jelinek clearly illustrates that the implant profile 510 of the "second interval" implantation process has a channeled peak 510B that is deeper than the channeled peak 505B of the implant profile 505 of the "first interval" implantation process. As previously noted, this is the opposite of the claimed method, which recites that "the second channelized doping profile has a second channeled peak at a third depth in the silicon carbide semiconductor layer that is between the first depth and the second depth, wherein the second implant energy is less than the first implant energy."
The Examiner respectfully disagrees with the Applicant’s analysis. The Applicant’s arguments acknowledge that the second implant interval of Jelinek 106, particularly as interpreted from the embodiment in paragraph 49, is performed at a lower implant energy than the first implant interval. This is exactly what the claim requires. While the specific motivations or reasons indicated by Jelinek 106 may differ, the process results in a similar outcome, as shown in the distribution profiles of Figure 5.
Paragraph 49 of Jelinek introduces multiple, distinct implantation intervals with different dopants (phosphorous and nitrogen). Specifically, Jelinek teaches, “In some embodiments, the first interval implantation is performed using phosphorous and an implant energy of about 800-1200 keV … In some embodiments, the second interval implantation is performed using nitrogen and an implant energy of greater than 300 keV…. In some embodiments, the second interval is performed prior to the first interval.”
Jelinek provides several alternative embodiments rather than a single, rigid sequence. The prior art must be read as a whole and the entire disclosure including alternative embodiments must be considered. Therefore, when using different dopants such as nitrogen and phosphorous, nitrogen may be implanted first at a high implant energy of 300keV or greater (profile 510 of Figure 5) and phosphorous maybe implanted afterwards at a lower implant energy of about 800-1200keV (profile 505 of Figure 5) as allowed for within the context of paragraph 49.
In this specific implementation, the second implants that is, phosphorous would be implanted at a lower implant energy than the first implant which is nitrogen. Consequently, the channeled peak 505B of the phosphorous profile is positioned at a third depth between the channel peak 510B and the de-channeled peak 510A of the nitrogen profile, thus reading on claim 1 limitation.
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 1-3, 7-8, 15, 60 and 62 are rejected under 35 U.S.C. 103 as being unpatentable over Jelinek et al. (US 2023/0083106 A1; hereafter Jelinek 106’) in view of Jelinek et al. (US 2021/0193435 A1; hereafter Jelinek 435’).
Regarding claim 1, Jelinek 106’ teaches in Figures 1, 4 and 5, a method of forming a buried implanted region in a silicon carbide semiconductor layer (see e.g., forming the doped region 110 in the drift layer 104, which maybe a silicon carbide layer, using channeled implantation processes, Paras [0028], [0053], Figure 1), comprising:
A first implantation interval is performed using phosphorous as the dopant with its resulting vertical distribution profile represented by 505. A second implantation interval is performed using nitrogen as the dopant with its resulting vertical distribution profile represented by 510. In some embodiments, the second interval (nitrogen) is performed prior to the first interval (phosphorous).
implanting first dopant ions having a first conductivity type (see e.g., n-type nitrogen dopant having a vertical distribution profile 510 representing nitrogen implantation process, Paras [0049], [0051], Figure 5) into the silicon carbide semiconductor layer (see e.g., silicon carbide drift layer 104, Figure 1) along a first axis (see e.g., nitrogen implantation process is performed in the <11-23> or <0001> crystal channel direction using the target axis 115B, Paras [0049], [0051], Figure 1) at a first dose (see e.g., implanting nitrogen includes implanting the nitrogen at a dose less than 5×10.sup.13/cm.sup.2, Para [0078]) and first implant energy (see e.g., implanting nitrogen includes implanting the nitrogen at an implantation energy greater than 300 keV, Para [0077]) to form a first channelized doping profile (see e.g., vertical distribution profile 510 represents nitrogen implantation process, Para [0051], Figure 5),
wherein the first channelized doping profile has a first peak at a first depth (see e.g., the vertical distribution profile 510 comprises a primary implantation peak 510A at a depth from the surface, Para [0051], Figure 5)in the silicon carbide semiconductor layer and a first channeled peak at a second depth (see e.g., the vertical distribution profile 510 comprises a channeling implantation peak 510B at a depth from the surface, Para [0051], Figure 5) in the silicon carbide semiconductor layer that is greater than the first depth (see e.g., as can be seen from Figure 5 the channeled implantation peak 510B is at a greater depth than the primary peak 510A); and
implanting second dopant ions having the first conductivity type (see e.g., n-type phosphorous dopant having a vertical distribution profile 505 representing phosphorous implantation process, Paras [0049], [0051], Figure 5) into the silicon carbide semiconductor layer along the first axis (see e.g., phosphorous implantation process is performed in the <0001> direction or the <11-23> direction using the target axis 115A or the target axis 115B, Para [0049], Figure 1) at a second dose (see e.g., implanting phosphorous includes implanting the phosphorous at a dose less than 5×1013/cm.sup.2, Para [0067]) and second implant energy (see e.g., implanting phosphorous includes implanting the phosphorous at an implantation energy greater than 500 keV, Para [0066]) to form a second channelized doping profile (see e.g., vertical distribution profile 505 represents phosphorous implantation process, Para [0051], Figure 5),
wherein the second channelized doping profile has a second channeled peak at a third depth (see e.g., the vertical distribution profile 505 has a channeled implantation peak 505B at a depth from the surface, Para [0051], Figure 5) in the silicon carbide semiconductor layer that is between the first depth and the second depth (see e.g., as can be seen from Figure 5 the channeled implantation peak 505 is between the primary implantation peak 510A and the channeled implantation peak 510B).
wherein the second implant energy is less than the first implant energy and (see e.g., nitrogen implantation maybe performed before the phosphorous implantation. Nitrogen is implanted at a high energy such as 1500keV, or any energy exceeding 300keV to create a vertical distribution profile 510. While phosphorous is implanted using a lower energy, approximately 800-120keV to create a vertical distribution profile 505, Paras [0049], [0051], Figure 5)
wherein the first channelized doping profile and the second channelized doping profile form a combined doping profile that defines the buried implanted region (see e.g., The vertical distribution profile 515 represents the combined phosphorous and nitrogen vertical distribution in the doped region 110. The vertical distribution profile 515 comprises a primary implantation peak 515A and a channeling implantation peak 515B., Para [0051], Figure 5).
Jelinek 106’ teaches a primary implantation peak but does not explicitly teach that this is a de-channeled peak.
In a similar field of endeavor Jelinek 435’ teaches that the primary implantation peak is a de-channeled peak (see e.g., end-of range peak 404 in Figure 2A is the primary peak that is, end-of range peak of the randomly dopant ions, Para [0136]).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Jelinek 435’s teachings of having a channelized doping profile with a de-channeled peak and a channeled peak in the method of Jelinek 106’ so that the vertical dopant concentration profile of the implanted dopant ions approximates a desired profile, e.g., a wide, plateau-like dopant profile with a less pronounced minimum or a dopant profile with two pronounced peaks.
Regarding claim 2, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches further comprising:
annealing the silicon carbide semiconductor layer after implanting the first and/or second dopant ions to activate the first and second dopant ions (see e.g., channeled implants result in reduced damage to the drift layer 104 which allows the activation annealing to be performed at a lower temperature-time product, Para [0053]).
Regarding claim 3, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches wherein the first dose is less than 1E13 cm-2 (see e.g., the first nitrogen implantation is performed at a dose less than 5x10.sup.13/cm.sup.2, Paras [0042], [0049], [0051]; Examiner’s interpretation: the dose for nitrogen implantation can have any value less than 5x10.sup.13/cm.sup.2).
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990).
Regarding claims 7-8, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches wherein the combined doping profile has a variation in doping concentration between the first de-channeled peak and the first channeled peak between 5% and about 10% (see e.g., In some embodiments, a ratio of dopant maximum concentration to minimum concentration in the vertical extension region is less than 1.2. Therefore, the percentage increase in the maximum concentration in the vertical extension region, that is, between the primary implantation peak and the channeling implantation peak, can have any value less than 20%. According to some embodiments, the resulting implanted dopant profile consists of exactly two local maxima and a drop of dopant concentration between these two local maxima of less than 50% or less than 20% or less than 10%, Paras [0055], [0084]).
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990).
Regarding claim 15, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches wherein a distance between the first depth and the second depth is greater than about 1 micron (see e.g., a vertical extension region is defined as the region between the first depth (having a primary implantation peak from the first surface) and the second depth (having a channeling implantation peak from the first surface). For a doped region 110 having a vertical extension region from about 0.2 to 2.1 microns means that the primary implantation peak occurs at 0.2 microns from the surface and the channeling implantation peak occurs at 2.1 microns from the surface resulting in a depth range of the vertical extension region to be 1.9 microns that is the primary implantation peak and the channeling implantation peak are apart by a distance of 1.9 microns, Paras [0008], [0055], Figure 5).
Regarding claim 60, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches wherein the first implant energy is between about 1.8 MeV and 2.0 MeV implanting phosphorous includes implanting the phosphorous at an implantation energy greater than 500 keV. Implanting nitrogen includes implanting the nitrogen at an implantation energy greater than 300 keV, Paras [0066], [0077]; Examiner’s interpretation: the implantation energies for phosphorus and nitrogen can have any value greater than 500keV and 300keV respectively).
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990).
Regarding claim 62, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches
wherein the combined doping profile has a variation in doping concentration between the de-channeled peak and the channeled peak of less than about 15% (see e.g., In some embodiments, a ratio of dopant maximum concentration to minimum concentration in the vertical extension region is less than 1.2 that is, the percentage increase in the maximum concentration in the vertical extension region, that is, between the primary implantation peak and the channeling implantation peak, can have any value less than 20%. According to some embodiments, the resulting implanted dopant profile consists of exactly two local maxima and a drop of dopant concentration between these two local maxima of less than 50% or less than 20% or less than 10%, Paras [0055], [0084]).
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990).
Claims 9-10 are rejected under 35 U.S.C. 103 as being unpatentable over Jelinek et al. (US 2023/0083106 A1; hereafter Jelinek 106’) in view of Jelinek et al. (US 2021/0193435 A1; hereafter Jelinek 435’) and further in view of Van Brunt et al. (US 2015/0028351 A1; hereafter Van Brunt 351’).
Regarding claim 9, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ does not explicitly teach wherein the buried implanted region comprises a channel region of a vertical semiconductor device.
In a similar field of endeavor Van Brunt 351’ teaches wherein the buried implanted region comprises a channel region of a vertical semiconductor device (see e.g., channel 15 of a JFET 10 maybe formed by channeled implants, Paras [0049], [0060], Figure 1).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 351’s teachings of the buried implanted region comprises a channel region of a vertical semiconductor device in the method of Jelinek 106’ since channeled implants may have significantly greater depths than non-channeled implants and implant depth can be controlled by carefully controlling the tilt angle of the implantation. Rotation angle during implantation may also affect dopant distributions of channeled implants.
Regarding claim 10, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 351’, teaches the limitations of claim 9 as mentioned above. Jelinek 106’ does not explicitly wherein the vertical semiconductor device comprises a vertical junction field effect transistor device.
In a similar field of endeavor Van Brunt 351’ teaches wherein the vertical semiconductor device comprises a vertical junction field effect transistor device (see e.g., channel 15 of a JFET 10 maybe formed by channeled implants, Paras [0049], [0060], Figure 1).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 351’s teachings of the vertical semiconductor device comprises a vertical junction field effect transistor device in the method of Jelinek 106’ since channeled implants may have significantly greater depths than non-channeled implants and implant depth can be controlled by carefully controlling the tilt angle of the implantation. Rotation angle during implantation may also affect dopant distributions of channeled implants.
Claims 12-13 are rejected under 35 U.S.C. 103 as being unpatentable over Jelinek et al. (US 2023/0083106 A1; hereafter Jelinek 106’) in view of Jelinek et al. (US 2021/0193435 A1; hereafter Jelinek 435’) and further in view of Zhang et al. (US 2022/0359710 A1; hereafter Zhang).
Regarding claims 12-13, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches wherein the buried implanted region has a dopant concentration tail beneath the buried implanted region that decreases (see e.g., as shown in Figure 5 the buried implanted region 110 has a dopant concentration tail (on the right side of the curve) beneath the buried implanted region with a decreasing dopant concentration).
Jelinek 106’ does not explicitly teach dopant concentration that decreases at a rate of greater than about 1.0 E17 atoms/(cm.sub.3-micron).
In a similar field of endeavor Zhang teaches dopant concentration that decreases at a rate of greater than about 1.0 E17 atoms/(cm.sub.3-micron) (see e.g., Figures 3 and 4 where the tails attached to the right side of the second peaks decrease over the course of greater than 10^17, as for example 420 peaks at just above 10^18, then dips down from 10^18 to 10^16).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Zhang’s teachings of dopant concentration that decreases at a rate of greater than about 1.0 E17 atoms/(cm.sub.3-micron) in the method of Jelinek 106’ so that the channelized profile has drop offs which are fast and dramatic, so the field is constant for a part of the depth and then almost not present thereafter.
Claims 4, 39-40, 42-45, 50-52 and 61 are rejected under 35 U.S.C. 103 as being unpatentable over Jelinek et al. (US 2023/0083106 A1; hereafter Jelinek 106’) in view of Jelinek et al. (US 2021/0193435 A1; hereafter Jelinek 435’) and Van Brunt et al. (US 2017/0345891 A1; hereafter Van Brunt 891’).
Regarding claim 4, Jelinek 106’, as modified by Jelinek 435’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ does not explicitly teach wherein implanting the first dopant ions and/or implanting the second dopant ions is performed at room temperature.
In a similar field of endeavor Van Brunt 891’ teaches wherein implanting the first dopant ions and/or implanting the second dopant ions is performed at room temperature (see e.g., the multi-step channeling implant described with reference to Figure 23 is performed at room temperature, Para [0147], Figure 23).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 891’s teachings of implanting the first dopant ions and/or implanting the second dopant ions at room temperature in the method of Jelinek 106’ in order to reduce manufacturing cost.
Regarding claim 39, Jelinek 106’ teaches in Figures 1, 4 and 5, a method of forming a buried implanted region in a silicon carbide semiconductor layer (see e.g., forming the doped region 110 in the drift layer 104, which maybe a silicon carbide layer, using channeled implantation processes, Paras [0028], [0053], Figure 1), comprising:
Jelinek 106’ in Figure 4 shows the vertical distribution profile 410 for a phosphorus implantation. The doped region 110 in Figure 1 maybe doped with phosphorous using the implantation process corresponding to the vertical distribution profile 410 (see e.g., Paras [0039], [0081]). Jelinek 106’ discloses in paragraph [0046] to achieve a vertical distribution for the dopants of the doped region 110 as homogeneous as possible, the implantation energy may be varied during implantation. For example, a first interval of the implantation is first performed with a first implantation energy and a second interval is performed with a second implantation energy less than the first implantation energy. In some embodiments, at most two implantation energies are employed.
Hence, although not explicitly shown the vertical distribution profile 410 maybe formed by a first interval of the implantation at a first energy and a second interval of the implantation at a second energy.
wherein the first implanted region and the second implanted region form a combined doping profile that defines the buried implanted region (see e.g., the doped region 110 in the drift layer 104 may have a vertical distribution profile 410 for a phosphorus implantation that maybe formed by varying implantation energy during the implantation. For example, a first interval of the implantation is first performed with a first implantation energy and a second interval is performed with a second implantation energy less than the first implantation energy to avoid reducing the achievable maximum penetration depth significantly by the crystal damage generated during the first ion implantation. In some embodiments, at most two implantation energies are employed, Paras [0039], [0046], Figure 4)
wherein forming the first implanted region comprises implanting first dopant ions of a first element type having a first conductivity type into the silicon carbide semiconductor layer along a first axis (see e.g., doped region 110 formed in silicon carbide may be doped with phosphorus. phosphorous implantation process is performed in the <0001> direction or the <11-23> direction using the target axis 115A or the target axis 115B, Paras [0046], [0049], [0081], Figure 4) at a first dose (see e.g., implanting phosphorous includes implanting the phosphorous at a dose less than 5×1013/cm.sup.2, Para [0067]) and first implant energy (see e.g., phosphorus is doped using two implantation intervals where a first interval of the implantation is first performed with a first implantation energy and second interval of the implantation is performed with a second implantation energy, Para [0046])
wherein forming the second implanted region comprises implanting second dopant ions of the first element (see e.g., the doped region 110 may be formed of phosphorus in which case the second dopant ions would be similar to the first dopant ions that is, both will be phosphorus, Para [0081]) into the silicon carbide semiconductor layer along the first axis (see e.g., phosphorous implantation process is performed in the <0001> direction or the <11-23> direction using the target axis 115A or the target axis 115B, Para [0049], Figure 4) and second implant energy (see e.g., phosphorus is doped using two implantation intervals where a first interval of the implantation is first performed with a first implantation energy and second interval of the implantation is performed with a second implantation energy, Para [0046])
wherein the second implant energy is less than the first implant energy (see e.g., phosphorus is doped using two implantation intervals where a first interval of the implantation is first performed with a first implantation energy and second interval of the implantation is performed with a second implantation energy where the second implantation energy is less than the first implantation energy, Para [0046])
Jelinek 106’ does not explicitly teach
“forming a first implanted region having a first channelized doping profile and a second implanted region having a second channelized doping profile in the silicon carbide semiconductor layer,
to form a first channelized doping profile,
wherein the first channelized doping profile has a first de-channeled peak at a first depth in the silicon carbide semiconductor layer and a first channeled peak at a second depth in the silicon carbide semiconductor layer that is greater than the first depth; and
to form a second channelized doping profile,
wherein the second channelized doping profile has a second channeled peak at a third depth in the silicon carbide semiconductor layer that is between the first depth and the second depth”.
The Van Brunt 891’ reference is used to show the different dopant profiles for the same type of dopant at different implant energies which result in a combined dopant profile having dopant concentration changes less than one half an order of magnitude (see e.g., Para [0146]). The combined vertical distribution profile 410 of Jelinek 106’ for phosphorus implantation maybe formed by varying the implantation energy, in which case there would be individual vertical distributions profiles (not explicitly shown by Jelinek) which together form the combined vertical distribution profile 410.
In a similar field of endeavor Van Brunt 891’ teaches
forming a first implanted region having a first channelized doping profile (see e.g., curve 968 shows the dopant concentration for an implant energy of 900 keV and a dose of 1×10.sup.13 cm.sup.−2, with the implant performed at room temperature. .sup.27Al.sup.+ ions implanted in silicon carbide, Para [0143], Figure 23) and a second implanted region having a second channelized doping profile in the silicon carbide semiconductor layer (see e.g., curve 964 shows the dopant concentration for an implant energy of 500keV with the implant performed at room temperature. .sup.27Al.sup.+ ions implanted in silicon carbide, Para [0143], Figure 23),
to form a first channelized doping profile (see e.g., curve 968, Para [0143], Figure 23),
wherein the first channelized doping profile has a first de-channeled peak at a first depth in the silicon carbide semiconductor layer and a first channeled peak at a second depth in the silicon carbide semiconductor layer that is greater than the first depth (see e.g., the curve 968 has a de-channeled peak near the surface and a channeled peak further from the surface of the silicon carbide substrate, Paras [0143] – [0145], Figure 23); and
to form a second channelized doping profile (see e.g., curve 964, Para [0143], Figure 23),
wherein the second channelized doping profile has a second channeled peak at a third depth in the silicon carbide semiconductor layer that is between the first depth and the second depth (see e.g., the curve 964 has a channeled peak in between the de-channel and channeled peak of curve 968, Para [0143], Figure 23).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 891’s teachings of forming a first implanted region having a first channelized doping profile and a second implanted region having a second channelized doping profile in the silicon carbide semiconductor layer, to form a first channelized doping profile, wherein the first channelized doping profile has a first de-channeled peak at a first depth in the silicon carbide semiconductor layer and a first channeled peak at a second depth in the silicon carbide semiconductor layer that is greater than the first depth; and to form a second channelized doping profile, wherein the second channelized doping profile has a second channeled peak at a third depth in the silicon carbide semiconductor layer that is between the first depth and the second depth in the method of Jelinek 106’ since the multi-step channeling implant offers advantages such as the implant maybe performed at room temperature, which may reduce manufacturing costs. Additionally, the channeled implant may result in significantly less damage to the silicon carbide crystal, as the ions penetrate deep into the crystal with greatly reduced scattering (which causes crystal damage), and the ions are primarily slowed and stopped within the crystal lattice due to electron cloud interactions.
Jelinek 106’ teaches a primary implantation peak but does not explicitly teach that this is a de-channeled peak.
In a similar field of endeavor Jelinek 435’ teaches that the primary implantation peak is a de-channeled peak (see e.g., end-of range peak 404 in Figure 2A is the primary peak that is, end-of range peak of the randomly dopant ions, Para [0136]).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Jelinek 435’s teachings of having a channelized doping profile with a de-channeled peak and a channeled peak in the method of Jelinek 106’ so that the vertical dopant concentration profile of the implanted dopant ions approximates a desired profile, e.g., a wide, plateau-like dopant profile with a less pronounced minimum or a dopant profile with two pronounced peaks.
Regarding claim 40, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ further teaches further comprising:
annealing the silicon carbide semiconductor layer after implanting the first and/or second dopant ions to activate the first and second dopant ions (see e.g., channeled implants result in reduced damage to the drift layer 104 which allows the activation annealing to be performed at a lower temperature-time product, Para [0053]).
Regarding claim 42, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ does not explicitly teach
“wherein implanting the first dopant ions and/or implanting the second dopant ions is performed at room temperature”.
In a similar field of endeavor Van Brunt 891’ teaches wherein implanting the first dopant ions and/or implanting the second dopant ions is performed at room temperature (see e.g., the multi-step channeling implant described with reference to Figure 23 is performed at room temperature, Para [0147], Figure 23).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 891’s teachings of implanting the first dopant ions and/or implanting the second dopant ions at room temperature in the method of Jelinek 106’ in order to reduce manufacturing cost.
Regarding claims 43-45, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ further teaches wherein the combined doping profile has a variation in doping concentration between the first de-channeled peak and the first channeled peak of less than about 15% (see e.g., In some embodiments, a ratio of dopant maximum concentration to minimum concentration in the vertical extension region is less than 1.2. Therefore, the percentage increase in the maximum concentration in the vertical extension region, that is, between the primary implantation peak and the channeling implantation peak, can have any value less than 20%. According to some embodiments, the resulting implanted dopant profile consists of exactly two local maxima and a drop of dopant concentration between these two local maxima of less than 50% or less than 20% or less than 10%, Paras [0055], [0084]).
Regarding claim 50, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ further teaches wherein the first depth is less than about 1.5 microns and the second depth is greater than about 2 microns (see e.g., a vertical extension region is defined as the region between the first depth (having a primary implantation peak from the first surface) and the second depth (having a channeling implantation peak from the first surface). For a doped region 110 having a vertical extension region from about 0.2 to 2.1 microns means that the primary implantation peak occurs at 0.2 microns from the surface, less than 1.5 microns, and the channeling implantation peak occurs at 2.1 microns, greater than 2 microns, from the surface, Paras [0008], [0055], Figure 5).
Regarding claim 51, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ further teaches wherein a distance between the first depth and the second depth is greater than about 1 micron (see e.g., a vertical extension region is defined as the region between the first depth (having a primary implantation peak from the first surface) and the second depth (having a channeling implantation peak from the first surface). For a doped region 110 having a vertical extension region from about 0.2 to 2.1 microns means that the primary implantation peak occurs at 0.2 microns from the surface and the channeling implantation peak occurs at 2.1 microns from the surface resulting in a depth range of the vertical extension region to be 1.9 microns that is the primary implantation peak and the channeling implantation peak are apart by a distance of 1.9 microns, Paras [0008], [0055], Figure 5).
Regarding claim 52, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ further teaches wherein the first element type comprises phosphorus (see e.g., the vertical distribution profile 410 for phosphorous implantation, Paras [0041], [0042], Figure 4).
Regarding claim 61, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 39 as mentioned above. Jelinek 106’ further teaches wherein the first implant energy is between about 1.8 MeV and 2.0 MeV, (see e.g., implanting phosphorous includes implanting the phosphorous at an implantation energy greater than 500 keV, Paras [0066], [0077]; Examiner’s interpretation: the implantation energy for phosphorus and can have any value greater than 500keV)
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990).
wherein the second depth is greater than 2 microns, and (see e.g., a vertical extension region is defined as the region between the first depth (having a primary implantation peak from the first surface) and the second depth (having a channeling implantation peak from the first surface). For a doped region 110 having a vertical extension region from about 0.2 to 2.1 microns means that the primary implantation peak occurs at 0.2 microns from the surface and the channeling implantation peak occurs at 2.1 microns, greater than 2 microns, from the surface, Paras [0008], [0055], Figure 5)
wherein the combined doping profile has a variation in doping concentration between the first de-channeled peak and the first channeled peak of less than about 15% (see e.g., In some embodiments, a ratio of dopant maximum concentration to minimum concentration in the vertical extension region is less than 1.2. Therefore, the percentage increase in the maximum concentration in the vertical extension region, that is, between the primary implantation peak and the channeling implantation peak, can have any value less than 20%. According to some embodiments, the resulting implanted dopant profile consists of exactly two local maxima and a drop of dopant concentration between these two local maxima of less than 50% or less than 20% or less than 10%, Paras [0055], [0084]).
Claims 46-47 are rejected under 35 U.S.C. 103 as being unpatentable over Jelinek et al. (US 2023/0083106 A1; hereafter Jelinek 106’) in view of Jelinek et al. (US 2021/0193435 A1; hereafter Jelinek 435’) and Van Brunt et al. (US 2017/0345891 A1; hereafter Van Brunt 891’) and further in view of Van Brunt et al. (US 2015/0028351 A1; hereafter Van Brunt 351’).
Regarding claim 46, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ does not explicitly teach wherein the buried implanted region comprises a channel region of a vertical semiconductor device.
In a similar field of endeavor Van Brunt 351’ teaches wherein the buried implanted region comprises a channel region of a vertical semiconductor device (see e.g., channel 15 of a JFET 10 maybe formed by channeled implants, Paras [0049], [0060], Figure 1).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 351’s teachings of the buried implanted region comprises a channel region of a vertical semiconductor device in the method of Jelinek 106’ since channeled implants may have significantly greater depths than non-channeled implants and implant depth can be controlled by carefully controlling the tilt angle of the implantation. Rotation angle during implantation may also affect dopant distributions of channeled implants.
Regarding claim 47, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 9 as mentioned above. Jelinek 106’ does not explicitly wherein the vertical semiconductor device comprises a vertical junction field effect transistor device.
In a similar field of endeavor Van Brunt 351’ teaches wherein the vertical semiconductor device comprises a vertical junction field effect transistor device (see e.g., channel 15 of a JFET 10 maybe formed by channeled implants, Paras [0049], [0060], Figure 1).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Van Brunt 351’s teachings of the vertical semiconductor device comprises a vertical junction field effect transistor device in the method of Jelinek 106’ since channeled implants may have significantly greater depths than non-channeled implants and implant depth can be controlled by carefully controlling the tilt angle of the implantation. Rotation angle during implantation may also affect dopant distributions of channeled implants.
Claims 48-49 are rejected under 35 U.S.C. 103 as being unpatentable over Jelinek et al. (US 2023/0083106 A1; hereafter Jelinek 106’) in view of Jelinek et al. (US 2021/0193435 A1; hereafter Jelinek 435’) and Van Brunt et al. (US 2017/0345891 A1; hereafter Van Brunt 891’) and further in view of Zhang et al. (US 2022/0359710 A1; hereafter Zhang).
Regarding claims 48-49, Jelinek 106’, as modified by Jelinek 435’ and Van Brunt 891’, teaches the limitations of claim 1 as mentioned above. Jelinek 106’ further teaches wherein the buried implanted region has a dopant concentration tail beneath the buried implanted region that decreases (see e.g., as shown in Figure 5 the buried implanted region 110 has a dopant concentration tail (on the right side of the curve) beneath the buried implanted region with a decreasing dopant concentration).
Jelinek 106’ does not explicitly teach dopant concentration that decreases at a rate of greater than about 1.0 E17 atoms/(cm.sub.3-micron).
In a similar field of endeavor Zhang teaches dopant concentration that decreases at a rate of greater than about 1.0 E17 atoms/(cm.sub.3-micron) (see e.g., Figures 3 and 4 where the tails attached to the right side of the second peaks decrease over the course of greater than 10^17, as for example 420 peaks at just above 10^18, then dips down from 10^18 to 10^16).
Therefore, it would have been obvious to one skilled in the art at the time the invention was effectively filed to implement Zhang’s teachings of dopant concentration that decreases at a rate of greater than about 1.0 E17 atoms/(cm.sub.3-micron) in the method of Jelinek 106’ so that the channelized profile has drop offs which are fast and dramatic, so the field is constant for a part of the depth and then almost not present thereafter.
Conclusion
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/FAKEHA SEHAR/Examiner, Art Unit 2893
/YARA B GREEN/Supervisor Patent Examiner, Art Unit 2893
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