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 .
Specification
The objection to the title is withdrawn in view of applicants’ submission of a replacement title.
Claim Objections
Claim 11 is objected to under 37 CFR 1.75 as being a substantial duplicate of claim 10. When two claims in an application are duplicates or else are so close in content that they both cover the same thing, despite a slight difference in wording, it is proper after allowing one claim to object to the other as being a substantial duplicate of the allowed claim. See MPEP § 608.01(m).
Double Patenting
The nonstatutory double patenting rejection of claims 1-10 over U.S. Patent Appl. No. 18/344,863 (hereinafter “the ‘863 application”) is withdrawn in view of claim amendments made within the ‘863 application and in the instant application.
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claims 1-3 and 8 is/are rejected under 35 U.S.C. 103 as being unpatentable over U.S. Patent Appl. Publ. No. 2002/0023581 to Vodakov, et al. (hereinafter “Vodakov”) in view of U.S. Patent Appl. Publ. No. 2016/0236375 to Hori, et al. (“Hori”).
Regarding claim 1, Vodakov teaches a method of growing silicon carbide crystals (see the Abstract, Figs. 1-12, and entire reference which teach a method of growing a SiC single crystal (1)), comprising:
providing a raw material comprising a carbon element and a silicon element, and a seed crystal above the raw material into a reactor (see Figs. 3-4 and ¶¶[0034]-[0045] which teach providing a SiC raw material (417) with a seed crystal (401) provided above the raw material in a reactor);
performing a silicon carbide crystal growth process, wherein the growth process comprises heating the reactor and the raw material to form a silicon carbide crystal on the seed crystal (see Figs. 3-4 and ¶¶[0034]-[0045] which teach that the raw material (417) is heated to form a SiC crystal on the seed (401) via the sublimation method), and
during the growth process, a ratio difference (ΔTz/ΔTx) between an axial temperature gradient (ΔTz) and a radial temperature gradient (ΔTx) of the silicon carbide crystal is adjusted so that the ratio difference is controlled in the range of 0.5 to 3 to form the silicon carbide crystal (See Figs. 6-9, ¶[0007], ¶[0026], and ¶¶[0057]-[0058] of Vodakov which teach that during the growth stage in which the SiC crystal grows both laterally and vertically, the ratio of the lateral growth rate to the axial growth rate is in the overlapping range of between 0.35 and 1.75 which translates to values of 2.86 to 0.57 (i.e., 1/0.35 and 1/1.75) for the ratio of the axial to radial growth rate. Since the lateral and axial growth rates are determined by the lateral and axial temperature gradients, they necessarily are directly proportional to each other. Then in at least ¶[0031] Vodakov further teaches that the growth angle (107) during lateral crystal growth is determined by the lateral temperature gradient and the vertical temperature gradient. Thus, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Vodakov and, starting with a ratio in the overlapping range of 0.57 to 2.86, would be motivated to utilize routine experimentation to determine the optimal ratio of the axial temperature gradient to the radial temperature gradient during the lateral growth stage in order to produce a higher quality SiC crystal.).
Vodakov does not teach that during the growth process, the method further comprises increasing a doping amount of a nitrogen concentration, so that the nitrogen concentration increases from a first concentration at a start of the growth process to a second concentration at an end of the growth process, the first concentration is 2*1018 atom/cm3, the second concentration is 3*1018 atom/cm3, and the doping amount of the nitrogen concentration does not decrease during the growth process. However, in Figs. 1-5 and ¶¶[0020]-[0037] as well as elsewhere throughout the entire reference Hori teaches an analogous method of growing a nitrogen-doped SiC ingot (1) by the sublimation method. In Fig. 3, ¶[0016], and ¶¶[0031-[0033] Hori specifically teaches that the warpage of individual substrates which are cut from the SiC ingot (1) may be suppressed by producing a gradient in the nitrogen concentration which increases from a first concentration at point (22) at a start of the growth process to a second location at point (21) at an end of the growth process without decreasing during the growth process. Figure 3, ¶[0016], and ¶[0031] of Hori further teach that the nitrogen concentration gradient is preferably not more than 1×1018 cm-4 while the SiC layer (13) itself has a nitrogen concentration in the range of 1017 to 2×1019 cm-3. Thus, when the SiC layer (13) begins with a nitrogen concentration of 2×1018 cm-3 at point (22) it necessarily increases to 3×1018 cm-3 at point (21) after depositing a SiC layer having a thickness of 1 cm. Accordingly, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Hori and would be motivated to increase a nitrogen doping concentration from 2 to 3×1018 cm-3 from point (22) to point (21) over a thickness of 1 cm without decreasing the nitrogen concentration during the growth process in order to suppress the warpage of individual substrates that are cut from the grown SiC ingot.
Regarding claim 2, Vodakov teaches that the ratio difference is controlled in the range of 2 to 3 to form the silicon carbide crystal (see supra with respect to the rejection of claim 1 in which ¶[0007], ¶[0026], and ¶¶[0057]-[0058] of Vodakov teach that during the growth stage in which the SiC crystal grows both laterally and vertically, the ratio of the lateral growth rate to the axial growth rate is in the overlapping range of between 0.35 and 1.75 which translates to values of 2.86 to 0.57 (i.e., 1/0.35 and 1/1.75) for the ratio of the axial to radial growth rate; accordingly, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Vodakov and, starting with a ratio in the overlapping range of 0.57 to 2.86, would be motivated to utilize routine experimentation to determine the optimal ratio of the axial temperature gradient to the radial temperature gradient during the lateral growth stage in order to produce a higher quality SiC crystal).
Regarding claim 3, Vodakov teaches that the ratio difference is controlled in the range of 2.5 to 3 to form the silicon carbide crystal (see supra with respect to the rejection of claim 1 in which ¶[0007], ¶[0026], and ¶¶[0057]-[0058] of Vodakov teach that during the growth stage in which the SiC crystal grows both laterally and vertically, the ratio of the lateral growth rate to the axial growth rate is in the overlapping range of between 0.35 and 1.75 which translates to values of 2.86 to 0.57 (i.e., 1/0.35 and 1/1.75) for the ratio of the axial to radial growth rate; accordingly, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Vodakov and, starting with a ratio in the overlapping range of 0.57 to 2.86, would be motivated to utilize routine experimentation to determine the optimal ratio of the axial temperature gradient to the radial temperature gradient during the lateral growth stage in order to produce a higher quality SiC crystal).
Regarding claim 8, Vodakov does not teach that the nitrogen concentration increases in a linear fashion. However, as noted supra with respect to the rejection of claim 1, in Fig. 3, ¶[0016], and ¶[0033] Hori specifically teaches that the warpage of individual substrates which are cut from the SiC ingot (1) may be suppressed by producing a gradient in the nitrogen concentration which increases linearly from a first concentration at point (22) to a second location at point (21). Thus, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Hori and would be motivated to linearly increase a nitrogen doping concentration from a first to a second concentration during sublimation growth in the method of Vodakov in order to suppress the warpage of individual substrates that are cut from the grown SiC ingot.
Claim 9 is/are rejected under 35 U.S.C. 103 as being unpatentable over Vodakov in view of Hori and further in view of U.S. Patent Appl. Publ. No. 2012/0241766 to Ohtsuka, et al. (“Ohtsuka”).
Regarding claim 9, Vodakov and Hori do not teach that the nitrogen concentration increases in a stepwise fashion. However, in Figs. 1-2 and ¶¶[0016]-[0027] Ohtsuka teaches a method of growing a nitrogen-doped SiC layer (3) onto a SiC substrate (1) through the use of a buffer layer (2). In order to accommodate a lattice-constant difference between the SiC layer (3) and the substrate (1) the nitrogen concentration in the buffer layer (2) is increased in a step-wise manner as shown specifically in Figs. 1(a)-(c) which show embodiments in which the nitrogen concentration is increased in N = 2, 3, or 4 equal stepwise increments. In this manner the lattice constant difference is evenly split into N + 1 stages which helps mitigate the effects of lattice misfit. Thus, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Ohtsuka and would recognize that the nitrogen concentration gradient utilized to the method of Vodakov and Hori may be increased in a stepwise fashion in order to reduce the number of defects and presence of residual stress. In this case, a stepwise instead of linear increase may be considered as the use of a known equivalent for the same purpose. It is prima facie obvious to combine or substitute known equivalents for the same purpose. See MPEP 2144.06.
Claims 10-11 is/are rejected under 35 U.S.C. 103 as being unpatentable over Vodakov in view of Hori and further in view of U.S. Patent Appl. Publ. No. 2019/0106807 to Lin, et al. (“Lin”).
Regarding claim 10, Vodakov does not teach that increasing the doping amount of the nitrogen concentration is performed by increasing a flow of nitrogen in the reactor. However, in ¶[0018] Hori teaches that an increase in the nitrogen concentration is obtained by increasing the nitrogen flow rate during deposition such that a larger concentration of nitrogen is incorporated into the growing SiC ingot.
Vodakov and Hori do not teach that the increase of the flow of nitrogen is controlled in the range of 10 sccm to 50 sccm. However, in Figs. 1-4 and ¶¶[0024]-[0033] Lin teaches an analogous system and method for forming nitrogen doped SiC layers. In ¶[0030] Lin specifically teaches that a nitrogen concentration of about 1015 up to 1020 cm-3 in the deposited layer may be obtained by utilizing a nitrogen flow rate in the overlapping range of 0.01 up to 30,000 sccm. Thus, a person of ordinary skill in the art would look to the teachings of Lin and would be motivated to utilize routine experimentation to determine the optimal nitrogen flow rate, including within the claimed range of 10 to 50 sccm, which is necessary to produce the targeted nitrogen concentration in the SiC crystal ingot produced according to the method of Vodakov and Hori.
Regarding claim 11, Vodakov teaches a method of growing silicon carbide crystals (see the Abstract, Figs. 1-12, and entire reference which teach a method of growing a SiC single crystal (1)), comprising:
providing a raw material comprising a carbon element and a silicon element, and a seed crystal above the raw material into a reactor (see Figs. 3-4 and ¶¶[0034]-[0045] which teach providing a SiC raw material (417) with a seed crystal (401) provided above the raw material in a reactor);
performing a silicon carbide crystal growth process, wherein the growth process comprises heating the reactor and the raw material to form a silicon carbide crystal on the seed crystal (see Figs. 3-4 and ¶¶[0034]-[0045] which teach that the raw material (417) is heated to form a SiC crystal on the seed (401) via the sublimation method), and
during the growth process, a ratio difference (ΔTz/ΔTx) between an axial temperature gradient (ΔTz) and a radial temperature gradient (ΔTx) of the silicon carbide crystal is adjusted so that the ratio difference is controlled in the range of 0.5 to 3 to form the silicon carbide crystal (See Figs. 6-9, ¶[0007], ¶[0026], and ¶¶[0057]-[0058] of Vodakov which teach that during the growth stage in which the SiC crystal grows both laterally and vertically, the ratio of the lateral growth rate to the axial growth rate is in the overlapping range of between 0.35 and 1.75 which translates to values of 2.86 to 0.57 (i.e., 1/0.35 and 1/1.75) for the ratio of the axial to radial growth rate. Since the lateral and axial growth rates are determined by the lateral and axial temperature gradients, they necessarily are directly proportional to each other. Then in at least ¶[0031] Vodakov further teaches that the growth angle (107) during lateral crystal growth is determined by the lateral temperature gradient and the vertical temperature gradient. Thus, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Vodakov and, starting with a ratio in the overlapping range of 0.57 to 2.86, would be motivated to utilize routine experimentation to determine the optimal ratio of the axial temperature gradient to the radial temperature gradient during the lateral growth stage in order to produce a higher quality SiC crystal.).
Vodakov does not teach that during the growth process, the method further comprises increasing a doping amount of a nitrogen concentration, so that the nitrogen concentration increases from a first concentration at a start of the growth process to a second concentration at an end of the growth process, the first concentration is 2*1018 atom/cm3, the second concentration is 3*1018 atom/cm3, and the doping amount of the nitrogen concentration does not decrease during the growth process. However, in Figs. 1-5 and ¶¶[0020]-[0037] as well as elsewhere throughout the entire reference Hori teaches an analogous method of growing a nitrogen-doped SiC ingot (1) by the sublimation method. In Fig. 3, ¶[0016], and ¶¶[0031-[0033] Hori specifically teaches that the warpage of individual substrates which are cut from the SiC ingot (1) may be suppressed by producing a gradient in the nitrogen concentration which increases from a first concentration at point (22) at a start of the growth process to a second location at point (21) at an end of the growth process without decreasing during the growth process. Figure 3, ¶[0016], and ¶[0031] of Hori further teach that the nitrogen concentration gradient is preferably not more than 1×1018 cm-4 while the SiC layer (13) itself has a nitrogen concentration in the range of 1017 to 2×1019 cm-3. Thus, when the SiC layer (13) begins with a nitrogen concentration of 2×1018 cm-3 at point (22) it necessarily increases to 3×1018 cm-3 at point (21) after depositing a SiC layer having a thickness of 1 cm. Accordingly, a person of ordinary skill in the art prior to the effective filing date of the invention would look to the teachings of Hori and would be motivated to increase a nitrogen doping concentration from 2 to 3×1018 cm-3 from point (22) to point (21) over a thickness of 1 cm without decreasing the nitrogen concentration during the growth process in order to suppress the warpage of individual substrates that are cut from the grown SiC ingot.
Vodakov does not teach that increasing the doping amount of the nitrogen concentration is performed by increasing a flow of nitrogen in the reactor. However, in ¶[0018] Hori teaches that an increase in the nitrogen concentration is obtained by increasing the nitrogen flow rate during deposition such that a larger concentration of nitrogen is incorporated into the growing SiC ingot.
Vodakov and Hori do not teach that the increase of the flow of nitrogen is controlled in the range of 10 sccm to 50 sccm. However, in Figs. 1-4 and ¶¶[0024]-[0033] Lin teaches an analogous system and method for forming nitrogen doped SiC layers. In ¶[0030] Lin specifically teaches that a nitrogen concentration of about 1015 up to 1020 cm-3 in the deposited layer may be obtained by utilizing a nitrogen flow rate in the overlapping range of 0.01 up to 30,000 sccm. Thus, a person of ordinary skill in the art would look to the teachings of Lin and would be motivated to utilize routine experimentation to determine the optimal nitrogen flow rate, including within the claimed range of 10 to 50 sccm, which is necessary to produce the targeted nitrogen concentration in the SiC crystal ingot produced according to the method of Vodakov and Hori.
Response to Arguments
Applicant's arguments filed August 20, 2025, have been fully considered but they are not persuasive and are moot in view of the new grounds of rejection set forth in this Office Action.
Applicant initially argues that Hori teaches that the nitrogen concentration varies from two locations in the SiC ingot rather than two time points during the growth process. See applicants’ 8/20/2025 reply, pp. 8-9. This argument is not found persuasive as Fig. 3 of Hori clearly shows that growth proceeds in the vertical direction and that there is a gradual and continuous increase in the nitrogen concentration during growth of the SiC layer (13) from the start of growth to the end of the growth process. Since the thickness of the SiC layer (13) increases with time there therefore is an increase in the nitrogen concentration from the start to the end of the growth process.
Applicant also argues against the teachings of Lin by arguing that in Lin the dopant cycles between high and low concentrations and, as such, the dopant decreases during growth. Id. at pp. 9-10. Applicant’s argument is noted, but it is pointed out that the rejections of claims 1 and 11 do not rely on the teachings of Lin. Moreover, applicants’ amendment to claim 1 necessitated the introduction of U.S. Patent Appl. Publ. No. 2012/0241766 to Ohtsuka, et al. to teach the use of a nitrogen concentration which increases in a stepwise fashion as recited in dependent claim 9.
Applicant generally argues that the Examples within the specification show that the recited method produces SiC wafers with improved materials properties. Id. at p. 10. Applicants’ argument is noted, but it is pointed out that since the cited prior art teaches each and every step of the process recited in claims 1 and 11 it must necessarily produce SiC wafers with the same materials properties. It is axiomatic that one who performs the steps of the known process must necessarily produce all of its advantages. Mere recitation of a newly discovered function or property, that is inherently possessed by things in the prior art does not cause a claim drawn to these things to distinguish over the prior art. See Leinoff v. Louis Milona & Sons, Inc. 220 USPQ 845 (CAFC 1984).
Applicants arguments with respect to the obviousness-type double patenting rejections of claims 1-10 have been considered (Id. at pp. 10-12) and are persuasive in view of amendments to the claims in U.S. Patent Appl. No. 18/344,863 and to the claims in the instant application.
Applicant refers to newly added claim 11 and specifically argues that Lin does not teach the recited nitrogen flow rate of 10 to 50 sccm with sufficient specificity. Id. at pp. 12-13. Applicant’s argument is noted, but is unpersuasive as applicant has not shown that a nitrogen flow rate of 10 to 50 sccm as claimed is critical or produces unexpected results. As explained supra with respect to the rejection of claims 10-11, in ¶[0030] Lin specifically teaches that a nitrogen concentration of about 1015 up to 1020 cm-3 in the deposited layer may be obtained by utilizing a nitrogen flow rate in the overlapping range of 0.01 up to 30,000 sccm. Since the nitrogen flow rate determines the nitrogen concentration in the SiC layer it is therefore considered to be a result-effective variable, i.e., a variable which achieves a recognized result. See, e.g., In re Antonie, 559 F.2d 618, 195 USPQ 6 (CCPA 1977). See also MPEP 2144.05(II)(B). Moreover, since the nitrogen flow rate is directly proportional to the resulting nitrogen concentration in the deposited SiC layer an ordinary artisan would recognize that the desired nitrogen concentration may be obtained through routine experimentation by, for example, gradually increasing the nitrogen flow rate until the targeted dopant concentration is achieved in the deposited SiC layer.
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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/KENNETH A BRATLAND JR/Primary Examiner, Art Unit 1714