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 .
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 14-19 are rejected under 35 U.S.C. 103 as being unpatentable over Hahnel et al. (Scripta Materialia 60 (2009) 858–861, of record), in view of De Silva et al. (Appl. Phys. Lett. 110, 252108 (2017), of record) and Tamaso et al. (US 2016/0056041, of record).
Re Claim 14, Hahnel teaches a method for producing an ohmic contact on a crystallographic C-side of a silicon carbide substrate, comprising the following steps:
applying a layer stack (Ni/Ge stack on 6H-SiC, abstract) to the crystallographic C-side of the silicon carbide substrate (N-doped {000-1} 6H-SiC substrate, Pg-858/Right Col/3rd para), the layer stack (Ni/Ge stack) including at least one semiconducting layer containing germanium (contains Ge as the interlayer) and at least one metallic layer (Ni layer); wherein the semiconducting layer is applied as the first layer of the stack and the metallic layer is applied directly over the semiconducting layer (the multilayer composition is Ni/Ge/6H-SiC, where Ge is the interlayer and is placed between 6H-SiC and Ni, see abstract, also see Pg-858/Right Col/3rd para) and
producing a liquid phase of the layer stack (formation of a solid solution of nickel silicide and nickel germanide after heating at 1245 K, Pg-860/Right Col/last two paras. Examiner notes that a solid solution can be created by melting two or more solids into liquids at high temperatures and then cooling the result, and according to the phase diagrams for these materials, some melting will occur at this temperature.)
Hahnel is silent about the procedure of the heat treatment and does not teach point-by-point heating by laser beam by scanning a surface of the layer stack, wherein the laser beams for producing the point-by-point liquid phase of the layer stack have a diameter of 10 µm to 100 µm and transmit an energy density of at least 1 J/cm2 onto the surface of the layer stack.
In a related semiconductor field of art, De Silva teaches forming ohmic contacts and discloses a laser treatment that offers advantages over conventional heating processes such as a furnace process. A laser treatment offers better control of the energy delivered at a lower thermal budget than conventional heating means which employ furnaces. De Silva further discloses scanning the laser, i.e., a point-by-point scanning type treatment as is well known in the laser processing art (Pg-2/Left Col/1st para and Right Col/1st para), where the laser power can vary between 1.9 J/cm2 to 2.8 J/cm2, within the claimed range (Pg-2/Right Col/1st para).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, absent unexpected results, to make the ohmic contact of Hahnel by laser treatment disclosed by De Silva because the laser process is better than a conventional furnace-based process due to the lower thermal budget (Pg-2/Left Col/1st para, De Silva).
Hahnel modified by De Silva is silent about the diameter of the laser beam to be between of 10 µm to 100 µm.
In a related semiconductor field of art, Tamaso teaches that the laser beams used in laser treatment process for establishing ohmic contact are normally pulsed, and the spot diameter of laser beams varies between approximately from several ten µm to several hundred µm, which in turn will vary the emitted laser energy as required (para [0029]).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, absent unexpected results, to use the range of diameters of the laser beam as disclosed by Tamaso in to the method of Hahnel modified by De Silva, in order to have more control on the emitted laser energy and vary the energy as needed for optimal performance.
Hahnel does not disclose that the thickness of the layer stack (Ni/Ge stack) is between 20 nm and 300 nm.
However, Hehnel discloses that the thickness of Ge layer can be 11 nm (Pg-858/Right Col/3rd para) and the thickness of the Ni layer can be 5 nm (Pg-858/Right Col/3rd para), resulting in a total thickness of 16 nm of the Ni/Ge layer stack. It would have been obvious to one of ordinary skill in the art, at the time of invention, to optimize the thickness of the layer stack and arrive at the claimed range. With respect to the limitations of the claim, where the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation. See In re Aller, 220 F.2d 454, 456, 105 USPQ 233 (CCPA 1955). The optimization of the thickness of the layer stack would have been obvious to one of ordinary skill in the art.
Re Claim 15, Hahnel modified by De Silva and Tamaso teaches the method as recited in claim 14, wherein semiconducting layers (Hahnel, Germanium layer) and metallic layers (Hahnel, Nickel layer) are applied to the crystallographic C-side of the silicon carbide substrate (Hahnel, N-doped {000-1} 6H-SiC substrate, Pg-858/Right Col/3rd para) in alternation (Hahnel, Ni/Ge/6H-SiC stack, abstract).
Re Claim 16, Hahnel modified by De Silva and Tamaso teaches the method as recited in claim 14, wherein nickel or titanium (Hahnel, Nickel layer, Pg-858/Right Col/3rd para) are applied as the metallic layers (Hahnel, Ni/Ge/6H-SiC stack, abstract).
Re Claim 17, Hahnel modified by De Silva and Tamaso teaches the method as recited in claim 16, wherein (i) vanadium or (ii) tantalum or (iii) niobium or (iii) zirconium or (iv) molybdenum or (v) tungsten or (vi) an alloy of (i) or (ii) or (iii) or (iv), with nickel or titanium, are applied as the metallic layers (De Silva, ohmic contacts on 4H-SiC with Ni, Nb, Mo, Nb/Ni, Mo/Ni multilayer contacts and NbNi mixed contact were reported, Pg-2/Left Col/2nd para).
Re Claim 18, Hahnel modified by De Silva and Tamaso teaches the method as recited in claim 14, wherein layer thicknesses of the semiconducting layers and layer thicknesses of the metallic layers of 3 nm to 100 nm are applied (Hahnel, Ge layer is ~11 nm and Ni layer is 5nm, Pg-858/Right Col/3rd para).
Re Claim 19, Hahnel modified by De Silva and Tamaso teaches the method as recited in claim 14, wherein the at least one semiconducting layer containing germanium is applied to the silicon carbide substrate as a first layer (Hahnel, Ni/Ge/6H-SiC stack, abstract; also see Pg-858/Right Col/3rd para).
Claims 23-25 are rejected under 35 U.S.C. 103 as being unpatentable over Hahnel et al. (Scripta Materialia 60 (2009) 858–861, of record), and further in view of De Silva et al. (Appl. Phys. Lett. 110, 252108 (2017), of record).
Re Claim 23, Hahnel teaches an ohmic contact on a crystallographic C-side of a silicon carbide substrate, comprising:
a layer that includes semiconducting elements containing germanium and metallic elements situated on the crystallographic C-side of the silicon carbide substrate (Ni/Ge/6H-SiC stack formed on N-doped {000-1} 6H-SiC substrate, Pg-858/Right Col/3rd para. Formation of a solid solution layer of nickel silicide and nickel germanide after heating at 1245 K, Pg-860/Right Col/last two paras. Examiner notes that a solid solution can be created by melting two or more solids into liquids at high temperatures and then cooling the result, and according to the phase diagrams for these materials, some melting will occur at this temperature.).
Hahnel is silent about the layer being a result of a laser treatment. Hahnel also does not explicitly disclose that a contact resistance between the silicon carbide substrate and the layer has a value of less than 100 µΩ/cm2 at a current density greater than 3A/mm2.
In a related semiconductor field of art, De Silva teaches forming ohmic contacts and discloses a laser treatment that offers advantages over conventional heating processes such as furnace process. A laser treatment offers better control of the energy delivered at a lower thermal budget than conventional means which employ furnaces. De Silva further discloses scanning the laser, i.e., a point-by-point scanning type treatment as is well known in the laser processing art (Pg-2/Left Col/1st para and Right Col/1st para).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, absent unexpected results, to make the ohmic contact of Hahnel by laser treatment disclosed by De Silva because the laser process is better than a conventional furnace-based process due to the lower thermal budget (Pg-2/Left Col/1st para, De Silva).
Examiner also notes that the limitation, “the layer being a result of a laser treatment” is a product-by-process claim. A product-by-process claim is a product claim. Applicant has merely chosen to define the claimed product by the process by which it was made. It has been well established that process limitations do not impart patentability to an old/obvious product. Process limitations are significant only to the extent that they distinguish the claimed product over the prior art product. Even though product-by-process claims are limited by and defined by the process, determination of patentability is based on the product itself. The patentability of a product does not depend on its method of production. If the product in the product-by-process claim is the same as or obvious from a product of the prior art, the claim is unpatentable even though the prior product was made by a different process. In re Thorpe, 777 F.2d 695, 698, 227 USPQ 964, 966 (Fed. Cir.1985). In this case, the claimed “layer being a result of a laser treatment” need not be formed by the process of laser treatment and may be formed by any means, noting Hahnel discloses a heat treatment. Once the Examiner provides a rationale tending to show that the claimed product appears to be the same or similar to that of the prior art, although produced by a different process, the burden shifts to applicant to come forward with evidence establishing an unobvious difference between the claimed product and the prior art product. In re Marosi, 710 F.2d 798, 802, 218 USPQ 289, 292 (Fed. Cir.1983).
Furthermore, Hahnel modified by De Silva does not explicitly disclose that a contact resistance between the silicon carbide substrate and the layer has a value of less than 100 µΩ/cm2 at a current density greater than 3A/mm2. However, Hahnel modified by De Silva discloses substantially the same structure and the materials as recited in the claim. When the structure recited in the reference is substantially identical to that of the claims, the claimed properties or functions are presumed to be inherent, see MPEP §2112.01(I).
Re Claim 24, Hahnel modified by De Silva teaches that the ohmic contact as recited in claim 23, wherein the metallic elements include nickel or titanium (Hahnel, Nickel layer, Pg-858/Right Col/3rd para).
Re Claim 25, Hahnel modified by De Silva teaches that the ohmic contact as recited in claim 24, wherein the metallic elements include vanadium or tantalum or niobium or zirconium or molybdenum or tungsten (De Silva, ohmic contacts on 4H-SiC with Ni, Nb, Mo, Nb/Ni, Mo/Ni multilayer contacts and NbNi mixed contact were reported, Pg-2/Left Col/2nd para).
Claim 22 is rejected under 35 U.S.C. 103 as being unpatentable over Hahnel et al. (Scripta Materialia 60 (2009) 858–861, of record), De Silva et al. (Appl. Phys. Lett. 110, 252108 (2017), of record) and Tamaso et al. (US 2016/0056041, of record) as applied to claim 14 above, and further in view of Kitabayashi et al. (US 2013/0143398, of record).
Re Claim 22, Hahnel modified by De Silva and Tamaso teaches the method as recited in claim 14, but is silent about the pulse repetition frequency of the laser beams is between 10 kHz and 50 kHz.
In a related semiconductor field of art, Kitabayashi discloses that the pulsed laser used for making ohmic contact has a repetition frequency of 20 kHz (para [0091]).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, absent unexpected results, to use the repetition frequency of the laser beam as disclosed by Kitabayashi in to the method of Hahnel modified by De Silva, in order to have more control on the amount of laser energy deposited on the ohmic contact for optimal performance.
Response to Arguments
Applicant’s arguments with respect to claim 14 has been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument.
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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/P.D./Examiner, Art Unit 2898 /JULIO J MALDONADO/Supervisory Patent Examiner, Art Unit 2898