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 .
Election/Restrictions
Applicant’s election without traverse of Invention I (claims 1-15) and Species 3 in the reply filed on 03 August 2026 is acknowledged. Claims 2-5 (drawn to non-elected species 1 and 2) and 16-20 (drawn to non-elected Invention II) are withdrawn from consideration.
Drawings
The drawings are objected to under 37 CFR 1.83(a). The drawings must show every feature of the invention specified in the claims. Therefore, the “distance between the contact layer and the substrate in a vertical direction is less than a height of the second semiconductor layer in the vertical direction,” of claim 12 must be shown or the feature(s) canceled from the claim(s). No new matter should be entered.
Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application. Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as “amended.” If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency. Additional replacement sheets may be necessary to show the renumbering of the remaining figures. Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either “Replacement Sheet” or “New Sheet” pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
Claim Rejections - 35 USC § 103
Claims 1 and 7-15 are rejected under 35 U.S.C. 103 as being unpatentable over Bahl et al. (US PGPub 20120223317 A1; hereinafter referred to as "Bahl”) in view of Okagawa et al. (JP 2006059933 A; hereinafter referred to as "Okagawa”).
Re claim 1: Bahl teaches a semiconductor device (FIG. 1, 2E), comprising: a substrate (para. 25| layers of FIG. 2E formed on a substrate); an epitaxial structure (FIG. 1, 2E: el. 102, 104; para. 25) disposed on the substrate (para. 25); a passivation layer (FIG. 2E: el. 210; para. 29) disposed on the epitaxial structure (FIG. 2E: el. 210, (102,104)); and an ohmic contact electrode (FIG. 1, 2E: el. 108; para. 22, 25) disposed in parallel with the passivation layer on the epitaxial structure (FIG. 2E: el. 108, 210, (102, 104)), wherein the ohmic contact electrode comprises a contact layer (FIG. 1, 2E: el. 114 of 108), the contact layer is in contact with the epitaxial structure such that a contact interface is formed between the contact layer and the epitaxial structure (FIG. 1, 2E: el. 114 of 108, (102, 104)). Bahl fails to teach wherein the ohmic contact electrode comprises a non-contact layer and a contact layer that are disposed in a laminated manner, wherein composition elements of the contact layer comprise a germanium element and a tantalum element.
In a similar field of endeavor, Okagawa teaches an ohmic contact electrode for contacting a nitride semiconductor such as GaN and AlGaN (para. 1, 15). Okagawa teaches wherein the ohmic contact electrode comprises a non-contact layer (FIG. 1: el. 12, 13; para. 10, 14) and a contact layer (FIG. 1: el. 11; para. 10, 14, 18) that are disposed in a laminated manner (FIG. 1: el. 11, (12, 13)), wherein composition elements of the contact layer comprise a germanium element and a tantalum element (para. 18). Okagawa discloses Al-Ta-Ge alloy as one predictable solution for contact materials which suppress stress migration in the contact layer (para. 18). One of ordinary skill in the art would have recognized the finite number of predictable solutions for alloy materials which suppress stress migration in the contact layer as taught by Okagawa. Absent unexpected results, it would have been obvious to try each of the alloy materials with improved stress migration taught by Okagawa, including the Al-Ta-Ge alloy, to yield an ohmic contact structure with reduced stress migration and improved reliability and contact resistance. Okagawa also teaches a benefit of the multilayer ohmic contact structure utilizing Al-Ta-Ge alloy is improved reliability owing to reduced stress migration, reduced high temperature degradation, and a reduction in contact resistance (para. 10, 18).
Therefore, it would have been obvious at the time of the effective filling date of the claimed invention to combine the teachings of Bahl and Okagawa, to enable using the contact layer and non-contact layer of Okagawa in the semiconductor device of Bahl, for the benefit of reduced stress migration and improved reliability, as well as an improved contact resistance.
Re claim 7: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 1, wherein the contact layer comprises elements Ge, Ta, and A, wherein the A element is any one of the following: Ti, Al, Pt, Au, Ni, Mo, and W (Okagawa – para. 18| Al-Ta-Ge alloy comprises Al as the A element).
Re claim 8: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 7, wherein the contact layer comprises an alloy formed by the elements Ge, Ta, and A (Okagawa – para. 18| Al-Ta-Ge alloy comprises an alloy with Al as the A element).
Re claim 9: The combination of Bahl and Okagawa fails to disclose the semiconductor device according to claim 8, wherein element composition of the alloy formed by the elements Ge, Ta, and A is shown in formula (II): GexAyTa1-x-y alloy wherein 0.5>x≥0.1, and 0.1≥y>0. However, it appears that the concentration of materials is a result effective variable to obtain a desired work function and suppress deformation and migration of the contact electrode (Okagawa – para. 7-9, 18). Therefore, it would have been obvious at the time of the effective filing date of the claimed invention to vary, through routine optimization, the compositional range of the alloy. In the absence of an indication that the claimed range produces unexpected results or has criticality, one of ordinary skill in the art would have had a reasonable expectation of success to arrive at the to arrive at the claimed compositional range, to achieve a robust contact with limited temperature induced deformation and with the desired migration and work function properties.
Re claim 10: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 1, wherein the epitaxial structure comprises: a first semiconductor layer located above the substrate (Bahl - FIG. 1, 2E: el. 104; para. 25| para. 25 teaches a first upper epitaxial semiconductor layer 104 formed above a substrate); and a second semiconductor layer located between the first semiconductor layer and the substrate and in contact with the first semiconductor layer (Bahl - FIG. 1, 2E: el. 102; para. 25| para. 25 teaches a second lower epitaxial semiconductor layer 102 formed between a substrate and first upper epitaxial semiconductor layer 104), wherein a two-dimensional electron gas is disposed on a side that is of the second semiconductor layer and that is close to the first semiconductor layer (Bahl - FIG. 1, 2E: el. 106; para. 15), wherein a distance between the contact layer and the second semiconductor layer in a vertical direction is less than a height of the first semiconductor layer in the vertical direction (Bahl - FIG. 1, 2E: el. 114 of 108, 102| distance between lower portion 114 of contact layer 108 and the 2nd semiconductor layer 102 is less than the height of the 1st semiconductor layer 104 because the lower portion 114 of the contact layer 108 contacts the 2nd semiconductor layer 102, resulting in a distance of zero).
Re claim 11: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 1, wherein the epitaxial structure comprises: a first semiconductor layer located above the substrate (Bahl - FIG. 1, 2E: el. 104; para. 25| para. 25 teaches a first upper epitaxial semiconductor layer 104 formed above a substrate); and a second semiconductor layer located between the first semiconductor layer and the substrate and in contact with the first semiconductor layer (Bahl - FIG. 1, 2E: el. 102; para. 25| para. 25 teaches a second lower epitaxial semiconductor layer 102 formed between a substrate and first upper epitaxial semiconductor layer 104), wherein a two-dimensional electron gas is disposed on a side that is of the second semiconductor layer and that is close to the first semiconductor layer (Bahl - FIG. 1, 2E: el. 106; para. 15), wherein the contact layer runs through the first semiconductor layer and is in contact with the second semiconductor layer (Bahl - FIG. 1, 2E: el. 114 of 108| lower portion 114 of contact layer 108 runs through the 1st semiconductor layer 104 and is in contact with the 2nd semiconductor layer 102).
Re claim 12: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 11, wherein a distance between the contact layer and the substrate in a vertical direction is less than a height of the second semiconductor layer in the vertical direction (Bahl - FIG. 1, 2E: el. 114 of 108; para. 25| distance between lower portion 114 of contact layer 108 and the substrate on which the 2nd semiconductor layer 102 is formed on, is less than the height of the 2nd semiconductor layer 102 because the lower portion 114 of the contact layer 108 extends below the top surface of the 2nd semiconductor layer 102).
Re claim 13: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 10, wherein the second semiconductor layer is gallium nitride (Bahl – para. 25; FIG. 2E: el. 102), and the first semiconductor layer is any one of AlGaN, InAiN, InAlGaN, AiN, ScAiN, and ScAlGaN (Bahl – para. 25; FIG. 2E: el. 104| 1st semiconductor layer 104 formed of AlGaN); or the second semiconductor layer is gallium arsenide, and the first semiconductor layer is InGaAs or AlGaAs.
Re claim 14: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 1, wherein the non- contact layer comprises a blocking layer comprising any one or more of the tantalum element, a titanium element, a nickel element, and a molybdenum element (Okagawa – FIG. 1: el. 12; para. 10, 14| non-contact layer formed of layers 12 and 13 comprises blocking layer 12 comprising titanium or molybdenum).
Re claim 15: The combination of Bahl and Okagawa teaches the semiconductor device according to claim 1, wherein the ohmic contact electrode is a source electrode or a drain electrode of the semiconductor device (Bahl – para. 18; FIG. 1, 2E: el. 108).
Claims 1 and 6 are rejected under 35 U.S.C. 103 as being unpatentable over Bahl in view of Anderson et al. (“Laser annealed Ta/Ge and Ni/Ge ohmic contacts to GaAs,” pg. 115-117; hereinafter referred to as “Anderson”) and in view of Kudymov et al. (US PGPub 20190139776 A1; hereinafter referred to as "Kudymov”).
Re claim 1: Bahl teaches a semiconductor device (FIG. 1, 2E), comprising: a substrate (para. 25| layers of FIG. 2E formed on a substrate); an epitaxial structure (FIG. 1, 2E: el. 102, 104; para. 16, 25| epitaxial structure formed of group III-V materials comprising a 2DEG) disposed on the substrate (para. 25| para. 25 teaches a substrate formed underneath the group III-V epitaxial structure); a passivation layer (FIG. 2E: el. 210; para. 29) disposed on the epitaxial structure (FIG. 2E: el. 210, (102,104)); and an ohmic contact electrode (FIG. 1, 2E: el. 108; para. 22, 25) disposed in parallel with the passivation layer on the epitaxial structure (FIG. 2E: el. 108, 210, (102, 104)), wherein the ohmic contact electrode comprises a contact layer (FIG. 1, 2E: el. 114 of 108), the contact layer is in contact with the epitaxial structure such that a contact interface is formed between the contact layer and the epitaxial structure (FIG. 1, 2E: el. 114 of 108, (102, 104)). Bahl fails to teach wherein the ohmic contact electrode comprises a non-contact layer and a contact layer that are disposed in a laminated manner, wherein composition elements of the contact layer comprise a germanium element and a tantalum element.
In a similar field of endeavor, Anderson teaches forming an ohmic contact to group III-V material devices using tantalum germanium alloy contacts (pg. 115: para. 1, 4: pg. 116: para. 4). Anderson teaches wherein composition elements of the contact layer comprise a germanium element and a tantalum element (pg. 115: para. 1, pg. 116: FIG. 2; para. 4). Anderson also teaches a benefit of the tantalum germanium contact is a reduction in contact resistance, an increase in robustness of a device to high temperature environments, and an improvement in device reliability in high temperature environments (pg. 115: para. 1, 4).
Therefore, it would have been obvious at the time of the effective filling date of the claimed invention to combine the teachings of Bahl and Anderson, to enable using the contact material of Anderson in the semiconductor device of Bahl, for the benefit of a reduction in contact resistance, an increase in robustness of a device to high temperature environments, and an improvement in device reliability in high temperature environments.
The combination of Bahl and Anderson fails to teach wherein the ohmic contact electrode comprises a non-contact layer and a contact layer that are disposed in a laminated manner.
In a similar field of endeavor, Kudymov teaches forming an ohmic contact to a group III-V material device. Kudymov teaches wherein the ohmic contact electrode comprises a non-contact layer (FIG. 2: el. 228; para. 31, 26| metal 228 in via 240 forms the non-contact layer of the ohmic contact electrode) and a contact layer (FIG. 2: el. 216; para. 26) that are disposed in a laminated manner (FIG. 2: el. 228, 216). Kudymov further teaches a benefit of laminating a non-contact layer of an ohmic contact electrode to a contact electrode of an ohmic contact electrode is to enable the contact electrode to be coupled to metal layers of the device (para. 31).
Therefore, it would have been obvious at the time of the effective filling date of the claimed invention to combine the teachings of the combination of Bahl and Anderson with the teachings of Kudymov, to enable using the non-contact layer of Kudymov in the semiconductor device of the combination of Bahl and Anderson, for the benefit of enabling electrical coupling of the contact electrode to other device layers.
Re claim 6: The combination of Bahl, Anderson, and Kudymov teaches the semiconductor device according to claim 1. Bahl fails to disclose wherein composition elements of the contact layer comprise a germanium element and a tantalum element and specifically wherein a ratio of a quantity of germanium to a quantity of tantalum is less than or equal to 50%.
In a similar field of endeavor, Anderson teaches forming an ohmic contact to group III-V material devices using tantalum germanium alloy contacts (pg. 115: para. 1, 4: pg. 116: para. 4). Anderson teaches wherein composition elements of the contact layer comprise a germanium element and a tantalum element (pg. 115: para. 1, pg. 116: FIG. 2; para. 4). Anderson teaches wherein a ratio of a quantity of germanium to a quantity of tantalum is less than or equal to 50% (Anderson – pg. 115: para. 5| Anderson specifically discloses a quantity of germanium to a quantity of Ta is less than 200% and greater than or equal to 50%, and as per MPEP 2144.05(i), "in the case where the claimed ranges ‘overlap or lie inside ranges disclosed by the prior art’ a prima facie case of obviousness exists”). Anderson also teaches a benefit of the disclosed tantalum germanium contact is a reduction in contact resistance, an increase in robustness of a device to high temperature environments, and an improvement in device reliability in high temperature environments (pg. 115: para. 1, 4).
Therefore, it would have been obvious at the time of the effective filling date of the claimed invention to use the overlapping range of the combination of Bahl, Anderson, and Kudymov to achieve a contact layer comprising a ratio of a quantity of germanium to a quantity of tantalum less than or equal to 50%, for the well-known benefits of increased device robustness to high temperature environments, improved device reliability in high temperature environments, and reduced contact resistance.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to DEVIN GOODLING whose telephone number is (571)272-2552. The examiner can normally be reached M-F 7:30am - 5:00pm.
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/D.G./Examiner, Art Unit 2898 /JULIO J MALDONADO/Supervisory Patent Examiner, Art Unit 2898
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