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
The amendment filed on Nov. 20th 2025 has been entered. Claims 1-18 and 21-24 remain pending in the application. Applicant's amendments to the Claims have overcome each and every objection and 112 rejection previously set forth in the Non-Final Office Action mailed on May 22nd 2025.
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.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-3 are rejected under 35 U.S.C. 103 as being unpatentable over Ma et al. ("Comparison of Different GaN Etching Techniques". CS MANTECH Conference, April 24-27, (2006)) in view of Song et al. (“Nitrogen-Polar (000-1) GaN Grown on c-Plane Sapphire with a High-Temperature AlN Buffer” Materials (2017), 10, 252).
Regarding claim 1, Ma teaches a method (Abstract) of etching a device (GaN based devices; INTRODUCTION), comprising:
obtaining an III-N layer (fig. 5, GaN samples are grown on C plane sapphire substrate; p. 106, para. 3) having a surface (surface for etching), wherein the surface has a starting surface roughness (roughness 3.8nm); and
etching the surface, wherein the etching (Citric Acid/H2O2 (2:1); TABLE I) is a wet etch (Citric Acid wet etch; p. 105, para. 4) using a wet etchant (Citric Acid) such that a final surface roughness of the surface (Roughness 2.3 nm; TABLE I), formed by the wet etching (Citric Acid etch), is not increased by more than a factor of 3 (2.3nm bigger than 3.8/3 nm) as compared to the starting surface roughness, and the final surface roughness is less than 3.0 nm rms roughness (2.3nm less than 3nm).
Ma fails to explicitly teach the III-N layer is an N-polar III-N layer.
However, Song teaches the III-N layer is an N-polar III-N layer (Song: fig. 5, N-polar GaN epilayers, p. 1, para. 2, similar to GaN of Ma).
Song and Ma are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the detail of N-polar as taught by Song.
Doing so would realize a GaN with N-polar orientation to achieve special device applications and starting surface roughness with improving the crystal quality (Song: p. 1, para. 1 and p. 6, para. 1).
Regarding claim 2, Ma further teaches the method of claim 1, wherein the etching (etching with Citric Acid/H2O2) comprises:
(a) the wet etching (Citric Acid etch wet etch) using the wet etchant comprising aqueous citric acid (Citric Acid) at a temperature (higher temperature than room temperature; p. 106, para. 2) above room temperature;
(b) the wet etchant comprising ammonium sulfide;
(c) the wet etchant comprising a mixture of phosphoric acid, nitric acid, acetic acid, and water;
(d) the wet etchant comprising an aqueous mixture of HCl; or
(e) the wet etchant comprising an aqueous mixture of HBr.
Regarding claim 3, Ma further teaches the method of claim 2, wherein the wet etchant comprising aqueous citric acid (Citric Acid) further comprises H202 (Citric Acid/H2O2), or
the wet etchant comprising HCL further comprises HNO3, or
the wet etchant comprising HBr further comprises HNO3.
Claims 4-6 and 10-13 are rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk et al. (“Demonstration of constant 8 W/mm power density at 10, 30, and 94 GHz in state-of-the-art millimeter-wave N-Polar GaN MISHEMTs,” IEEE Transactions on Electron Devices, vol. 65, no. 1, pp. 45-50, (2018)) in view of Huang et al. (US 20190206994).
Regarding claim 4, Romanczyk teaches a method of etching (Abstract) an N-polar III-N device structure (fig. 1a, N-polar GaN-based metal–insulator–semiconductor high-electron-mobility transistors MISHEMT; Abstract), comprising:
etching (etching the GaN and AlGaN caps; p. 46, para. 1) the N-polar III-N device structure (MISHEMT) comprising at least two layers (GaN Gap and AlGaN cap; p. 46, para. 2) comprising an AlxGa1-xN layer (GaN Gap, x=0) and an AlyGa1-yN (AlGaN cap, y=0.27) layer where x is less than y (0 less than 0.27).
Romanczyk fails to teach the etching comprising at least one of: (a) performing a pure wet etch, wherein the wet etch uses a solution comprising a first etchant that etches AlxGa1-xN faster than AlyGai-yN, or (b) performing a pure wet etch wherein the wet etch uses a solution comprising a second etchant that etches AlyGa1-yN faster than AlxGa1-xN.
However, Huang teaches the etching comprising at least one of: (a) performing a pure wet etch (Huang: wet chemical etching; para. 0054), wherein the wet etch (Huang: wet chemical etching) uses a solution (Huang: wet chemical etch chemistries; para. 0054) comprising a first etchant (Huang: HBr; para. 0054) that etches AlxGa1-xN (Huang: GaN; para. 0054) faster than AlyGa1-yN (Huang: Al-containing etch stop layer, AlN; para. 0054), or (b) performing a pure wet etch wherein the wet etch uses a solution comprising a second etchant that etches AlyGa1-yN faster than AlxGa1-xN.
Huang and Romanczyk are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the wet etch uses a solution that etches AlxGa1-xN faster than AlyGa1-yN where x is less than y as taught by Huang.
Doing so would realize better controlling of etching GaN recess depth.
Regarding claim 5, Romanczyk in view of Huang further teach the method of claim 4, further comprising performing the step (a) wherein the solution (Huang: wet chemical etch chemistries; para. 0054) comprising the first etchant (Huang: HBr) includes a mixture (Huang: etch chemistries of HBr; para. 0054) containing an inorganic acid (Huang: HBr) as an active ingredient.
Regarding claim 6, Romanczyk in view of Huang further teaches the method of claim 5, wherein the mixture comprises an aqueous mixture of at least one of HCl or HBr (Huang: HBr).
Regarding claim 10, Romanczyk in view of Huang further teaches the method of claim 4, wherein the layers (Romanczyk: fig. 1a, GaN Gap and AlGaN cap) comprise a doping profile (Romanczyk: GaN to AlGaN) that increases the preferential etching:
of the first etchant (Huang: HBr) when performing the step (a), increasing the etch rate of the AlxGa1-xN (Huang: GaN) as compared to the AlyGa1-yN (Huang: AlN similar to AlGaN), or
of the second etchant when performing the step (b), increasing the etch rate of the AlyGa1-yN as compared to the AlxGa1-xN.
Regarding claim 11, Romanczyk in view of Huang further teaches the method of claim 4, comprising:
obtaining the III-Nitride N-polar device structure (Romanczyk: fig. 1a, MISHEMT) comprising the at least two layers layers (Romanczyk: GaN Gap and AlGaN cap and layers below) comprising a nitride barrier layer comprising aluminum (Romanczyk: AlN, AlGaN backbarrier; p. 46, para. 1), a GaN channel layer (Romanczyk: GaN channel; p. 46, para. 1) on or above the nitride barrier layer (Romanczyk: AlN); a nitride cap layer comprising aluminum (Romanczyk: AlGaN cap layer; p. 46, para. 1) on or above the GaN channel layer (Romanczyk: GaN channel); and a GaN cap layer (Romanczyk: GaN cap layer; p. 46, para. 1) on or above the nitride cap layer (Romanczyk: AlGaN cap); and etching one or more of the layers (Romanczyk: GaN Gap and AlGaN cap), comprising the wet etching (Huang: wet chemical etching) using one or more solutions (Huang: wet chemical etch chemistries) comprising the first etchant (Huang: HBr) when the step (a) is performed or the second etchant when the step (b) is performed.
Regarding claim 12, Romanczyk in view of Huang further teaches the method of claim 11, wherein:
the device comprises a high electron mobility transistor (Romanczyk: fig. 1a, HEMTs, similar to HEMTs of Buttari), and
the method further comprises depositing an etch mask (Romanczyk: SiO2 hard mask; p. 47, para. 1) on the GaN cap layer (Romanczyk: GaN cap), the wet etching (Huang: wet chemical etching) etches a recess (Romanczyk: GaN cap recess; p. 46, para. 4) comprising a gate recess (Romanczyk: recess for foot gate G; p. 46, para. 4) through the GaN cap layer (Romanczyk: GaN cap), forming a lateral undercut (Romanczyk: bottom shape of G and undercut is normal in wet etching) in the etch mask (Romanczyk: SiO2 hard mask), and
the method further comprises depositing gate metal (Romanczyk: Cr/Au gate; p. 47, para. 1) in the gate recess (Romanczyk: G), wherein the lateral undercut (Romanczyk: bottom shape of G) allows deposition of the gate metal (Romanczyk: Cr/Au) in a self-aligned manner (Romanczyk: self-aligned to the GaN cap recess; p. 46, para. 4) and reduces or eliminates deposition of the gate metal on sidewalls of the GaN cap layer (Romanczyk: eliminating the variation associated with realignment of the foot gate to reduces or eliminates deposition of the gate metal; p. 46, para. 1).
Regarding claim 13, Romanczyk in view of Huang further teaches the method of claim 11, wherein:
the device comprises a high electron mobility transistor (Romanczyk: fig. 1a, HEMTs, similar to HEMTs of Buttari), and
the wet etching (Huang: wet chemical etching) etches at least one of:
a recess through part of the GaN cap layer that does not expose the nitride cap layer;
a recess (Romanczyk: GaN cap recess; p. 46, para. 4) through the GaN cap layer (Romanczyk: GaN cap) that exposes the nitride cap layer (Romanczyk: AlGaN cap), or
a thickness through the GaN cap layer and the nitride cap layer so as to expose the GaN channel layer.
Claim 7 is rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk in view of Huang as applied to claim 4 above, and further in view of Zhuang et al. ("Wei etching of GaN, AIN, and SiC: a review". Materials Science and Engineering R 48 (2005) 1-46).
Regarding claim 7, Romanczyk in view of Huang teaches the method of claim 4 including the wet etching (Huang: wet chemical etching HBr).
Romanczyk in view of Huang fails to explicitly teach adding an additional component comprising at least one of HNO3 or H2O2 to the solutions to tune an etch property of the wet etching.
However, Zhuang teaches an additional component (Zhuang: HCl/H2O2/HNO3; p. 5, Table 1) comprising at least one of HNO3 or H202 (Zhuang: H2O2/HNO3) to the solutions (Zhuang: HCl, similar to HBr of Huang) to tune an etch property of the wet etching (Zhuang: etching in acid and base solutions; p. 5, Table 1).
Zhuang, Huang and Romanczyk are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add at least one of HNO3 or H2O2 to the solutions to tune an etch property of the wet etching as taught by Zhuang.
Doing so would realize HNO3 or H2O2 for oxidizing and oxide removing agents.
Claims 4 and 8-10 are rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk in view of Ide et al. (“Advantages of AlN/GaN Metal Insulator Semiconductor Field Effect Transistor using Wet Chemical Etching with Hot Phosphoric Acid” in Jpn. J. Appl. Phys. Vol. 40 (2001) pp. 4785–4788).
Regarding claim 4, Romanczyk teaches a method of etching (Abstract) an N-polar III-N device structure (fig. 1a, N-polar GaN-based metal–insulator–semiconductor high-electron-mobility transistors MISHEMT; Abstract), comprising:
etching (etching the GaN and AlGaN caps; p. 46, para. 1) the N-polar III-N device structure (MISHEMT) comprising at least two layers (GaN Gap and AlGaN cap; p. 46, para. 2) comprising an AlxGa1-xN layer (GaN Gap, x=0) and an AlyGa1-yN (AlGaN cap, y=0.27) layer where x is less than y.
However, Ide teaches the etching comprising at least one of: (a) performing a pure wet etch, wherein the wet etch uses a solution comprising a first etchant that etches AlxGa1-xN faster than AlyGai-yN, or (b) performing a pure wet etch (Ide: wet chemical etching; p. 4785, para. 1 of EXPERIMENT) wherein the wet etch uses a solution (Ide: hot phosphoric acid; p. 4785, para. 1 of EXPERIMENT) comprising a second etchant (Ide: phosphoric acid; p. 4785, para. 1 of EXPERIMENT) that etches AlyGa1-yN (Ide: AlN films are etched at higher than GaN; p. 4785, para. 2 of EXPERIMENT) faster than AlxGa1-xN (Ide: GaN).
Ide and Romanczyk are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the wet etch uses a solution comprising a second etchant that etches AlxGa1-xN faster than AlyGa1-yN where x is greater than y as taught by Ide.
Doing so would realize a technique of wet chemical etching to improve the ohmic contacts in the AlN/GaN MISFET structure (Ide: p. 4785, para. 3).
Regarding claim 8, Romanczyk in view of Ide further teaches the method of claim 4, further comprising performing the step (b) the solution (Ide: hot phosphoric acid) comprising the second etchant (Ide: phosphoric acid) includes a mixture containing an organic acid (Ide: phosphoric acid) as an active ingredient.
Regarding claim 9, Romanczyk in view of Ide further teaches the method of claim 8, wherein the mixture comprises an aqueous mixture of at least one of citric acid or phosphoric acid (Ide: phosphoric acid).
Regarding claim 10, Romanczyk in view of Ide further teaches the method of claim 4, wherein the layers (Romanczyk: fig. 1a, GaN Gap and AlGaN cap) comprise a doping profile (Romanczyk: GaN to AlGaN) that increases the preferential etching:
of the first etchant when performing the step (a), increasing the etch rate of the AlxGa1-xN as compared to the AlyGa1-yN, or
of the second etchant (Ide: phosphoric acid) when performing the step (b), increasing the etch rate of the AlyGa1-yN (Ide: AlN, AlGaN) as compared to the AlxGa1-xN (Ide: GaN).
Claim 14 is rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk in view of Huang as applied to claim 13 above, and further in view of Downey et al. (“Electrical characterization of Schottky contacts to N-polar GaN,” Solid-State Electronics, vol. 86, pp. 17-21, (2013)).
Regarding claim 14, Romanczyk in view of Huang further teaches the method of claim 13, wherein the wet etching (Huang: wet chemical etching) forms the gate recess (Romanczyk: fig. 1a, GaN cap recess for foot gate G; p. 46, para. 4) exposing a wet etched surface (top etched surface) of the nitride cap layer (Romanczyk: AlGaN cap), the method further comprising:
depositing gate metal (Romanczyk: Cr/Au gate; p. 47, para. 1) on the wet etched surface (top etched surface) so as to form an electrical interface (Romanczyk: interface between gate G and AlGaN cap) with the wet etched surface (top etched surface).
Romanczyk in view of Huang fails to teach the electrical interface comprising a Schottky barrier, the electrical interface comprising at least one of:
a higher Schottky barrier height by 0.1 eV or more or a reduced gate leakage by a factor of 10 or more, relative to a dry-etched or non-wet-etch treated surface, and such that the gate metal forms a gate with an absolute gate leakage below 1 mA/mm at a drain voltage at or below 0.5 V and a gate voltage corresponding to 1 milliamp/millimeter of drain current.
However, Downey teaches the electrical interface (Downey: fig. 1, Schottky contact; p. 17, para. 2, similar to the interface between gate G and nitride cap layer of Romanczyk) comprising a Schottky barrier (Downey: Schottky barrier; p. 17, para. 1)
comprising a higher Schottky barrier height by 0.1 eV or more (Downey: barrier height higher than 0.5 eV; Table 1) or
a reduced gate leakage by a factor of 10 or more, relative to a dry-etched or non-wet-etch treated surface, and such that the gate metal forms a gate with an absolute gate leakage below 1 mA/mm at a drain voltage at or below 0.5 V and a gate voltage corresponding to 1 milliamp/millimeter of drain current.
Downey, Huang and Romanczyk are considered to be analogous to the claimed invention because they are in the same field of semiconductor devices.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the detail of the Schottky barrier as taught by Downey.
Doing so would realize a Schottky barrier to improve the HEMTs with excellent device properties (Downey: p. 17, para. 1).
Claim 15 is rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk in view of Huang and Downey as applied to claims 14 above, and further in view of Ramesh et al. (“Effect of annealing temperature on electrical characteristics of ruthenium-based Schottky contacts on n-type GaN”, J Mater Sci: Mater Electron 17, 999–1004 (2006)).
Regarding claim 15, Romanczyk in view of Huang and Downey further teaches the method of claim 14, wherein the gate metal (Romanczyk: fig. 1a, G).
Romanczyk in view of Huang and Downey fails to teach the gate metal comprises ruthenium metal or an alloy containing greater than 20% ruthenium metal and forms a barrier height greater than 0.6 eV to the nitride cap layer.
However, Ramesh teaches the gate metal (Ramesh: ruthenium (Ru) Schottky contacts; Abstract, similar to G of Romanczyk) comprises ruthenium metal (Ramesh: ruthenium (Ru); Abstract) or an alloy containing greater than 20% ruthenium metal and forms a barrier height greater than 0.6 eV (Ramesh: barrier height is 0.75 eV to 0.93 eV; Abstract) to the nitride cap layer (Ramesh: n-GaN, similar to nitride cap layer of Romanczyk).
Ramesh, Downey, Huang and Romanczyk are considered to be analogous to the claimed invention because they are in the same field of semiconductor devices.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to modify the gate metal comprising ruthenium metal as taught by Ramesh.
Doing so would realize a Ru Schottky contacts to improve the performance and reliability of Schottky contacts in the device (p. 999, para. 2).
Claim 16 is rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk in view of Huang as applied to claims 13 above, and further in view of Liu et al. (“An improved methodology for extracting interface state density at Si3N4/GaN,” Appl. Phys. Lett., vol. 116, 022104, (2020)).
Regarding claim 16, Romanczyk in view of Huang further teaches the method of claim 13, wherein the wet etching (Huang: wet chemical etching) forms the recess (Romanczyk: fig. 1a, GaN cap recess) comprising a gate recess (Romanczyk: recess for foot gate G; p. 46, para. 4) and exposes an N-polar wet etched surface (Romanczyk: N-polar GaN; p. 47, para. 1) of the nitride cap layer (Romanczyk: AlGaN cap), the method further comprising:
depositing a dielectric layer (Romanczyk: SiNx gate dielectric grown by MOCVD; p. 47, para. 1) ex situ in the recess (Romanczyk: GaN cap recess) and on the nitride cap layer (Romanczyk: AlGaN cap), wherein an electrical N-polar-dielectric interface (Romanczyk: the interface between SiNx and GaN cap), between the dielectric layer (Romanczyk: SiNx) and the N-polar wet etched surface (Romanczyk: AlGaN cap).
Romanczyk in view of Huang fails to teach a reduced number of interface states by a factor of 2 or more as compared to when the interface is formed using dry etching and with an overall density of interface states below 5x1012 cm-2eV1.
However, Liu teaches a reduced number of interface states (Liu: fig. 1, interface state density of Si3N4/GaN interface; Abstract.) by a factor of 2 or more as compared to when the interface is formed using dry etching and with an overall density of interface states below 5x10^12 cm-2eV-1 (Liu: 3.8x10^11 cm-2eV-1; Abstract).
Liu, Huang an Romanczyk are considered to be analogous to the claimed invention because they are in the same field of semiconductor devices.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the detail of the number of interface states as taught by Liu.
Doing so would realize evaluation of the number of interface states to improve and optimize the dielectrics on semiconductors (Liu: p. 022104-1, para. 2).
Claims 17-18 are rejected under 35 U.S.C. 103 as being unpatentable over Romanczyk in view of Huang as applied to claims 12 above, and further in view of Imada et al. (US20130083567).
Regarding claim 17, Romanczyk in view of Huang further teaches the method of claim 12, wherein the wet etching (Romanczyk: fig. 1a, SiO2 hard mask is then etched away using buffered HF acid diluted with H2O).
Romanczyk in view of Huang fails to teach a second wet etching step after formation of a gate in the gate recess, wherein the second wet etching step etches a thickness of the GaN cap layer so that the GaN cap layer is thinner on one side of the gate recess than the other.
However, Imada teaches a second wet etching step (Imada: fig. 3C, RIE and wet process; para. 0058, 0060, similar to wet etch remove hard mask of Romanczyk) after formation of a gate (Imada: 10B for gate electrode 6; para. 0068, similar to G of Romanczyk) in the gate recess (Imada: recess for 6), wherein the second wet etching step (Imada: RIE and wet process) etches a thickness of the GaN cap layer (Imada: n-GaN, n-type cap layer 2f; para. 0058, similar to GaN cap layer of Romanczyk) so that the GaN cap layer (Imada: 2f) is thinner on one side of the gate recess (Imada: recess for 6) than the other.
Imada, Huang and Romanczyk are considered to be analogous to the claimed invention because they are in the same field of semiconductor devices.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the detail of the GaN cap layer is thinner on one side of the gate recess than the other as taught by Imada.
Doing so would realize a thinner portion of n-type cap layer to the desired control of the amount of 2DEG by the field-plate electrode (para. 0058).
Regarding claim 18, Romanczyk in view of Huang and Imada further teaches the method of claim 17 comprising a T-shaped gate metal (Romanczyk: fig. 1a, gate G is T-shape) in the recess (Romanczyk: gate recess) and wherein the T-shaped gate metal (Romanczyk: G) is used as a mask (Romanczyk: G is used as mask on gate recess) during the wet etching (Romanczyk: SiO2 hard mask etched).
Claims 21-23 are rejected under 35 U.S.C. 103 as being unpatentable over Ma in view of Song as applied to claim 1 above, and further in view of DeSalvo et al. (“Wet Chemical Digital Etching of GaAs at Room Temperature” (1996) J. Electrochem. Soc. 143 3652).
Regarding claim 21, Ma further teaches the method of claim 1, wherein the etching further comprises: performing a first wet etchant step (Citric Acid wet etch) comprising aqueous citric acid (citric acid) at a temperature above room temperature (higher temperature than room temperature; p. 106, para. 2); Or a second wet etchant step (HCl etch; TABLE I) comprising aqueous HCl (HCl).
Ma in view of Song fails to explicitly teach after the first wet etchant step, performing a separate second wet etchant step comprising aqueous HCl.
However, DeSalvo teaches after the first wet etchant step (DeSalvo: cycles of 1 M Citric acid; Table II, similar to Citric Acid etch wet etch of Ma), performing a separate (DeSalvo: separate cycle digital etch step) second wet etchant step (DeSalvo: cycles of HCl:H20; Table II) comprising aqueous HCl (DeSalvo: HCl:H20).
DeSalvo, Song and Ma are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add performing a separate second wet etchant step as taught by DeSalvo.
Doing so would realize a wet chemical digital etching better control etch depth and to save processing time (DeSalvo: p. 3653, para. 4-5).
Regarding claim 22, Ma in view of Song and DeSalvo teaches the method of claim 21, wherein the wet etchant (DeSalvo: cycles of HCl:H20) comprising HCL (DeSalvo: HCl:H20) further comprises HNO3 (DeSalvo: oxidizing and oxide removing agents HNO3; p. 3654, para. 5).
Regarding claim 23, Ma in view of Song and DeSalvo teaches the device (Ma: GaN based devices) fabricated using the method of claim 21.
Claims 24 are rejected under 35 U.S.C. 103 as being unpatentable over Ma in view of Song and DeSalvo.
Regarding claim 24, Ma teaches a method (Abstract) of etching a device (GaN based devices; INTRODUCTION), comprising:
obtaining an III-N layer (GaN samples are grown on C plane sapphire substrate; p. 106, para. 3) comprising gallium nitride (GaN); and etching the III-N layer (GaN layer) using a first wet etching step (Citric Acid wet etch; p. 105, para. 4) comprising citric acid (Citric Acid/H2O2 (2:1); TABLE I).
Ma fails to explicitly teach the III-N layer is an N-polar III-N layer.
However, Song teaches the III-N layer is an N-polar III-N layer (Song: fig. 5, N-polar GaN epilayers, p. 1, para. 2, similar to GaN of Ma).
Song and Ma are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add the detail of N-polar as taught by Song.
Doing so would realize a GaN with N-polar orientation to achieve special device applications and starting surface roughness with improving the crystal quality (Song: p. 1, para. 1 and p. 6, para. 1).
Ma in view of Song fails to explicitly teach the first wet etchant step separate from a second wet etching step comprising HCl.
However, DeSalvo teaches after the first wet etchant step (DeSalvo: cycles of 1 M Citric acid; Table II, similar to Citric Acid etch wet etch of Ma) separate from a second wet etching step (DeSalvo: cycles of HCl:H20; Table II) comprising HCl (DeSalvo: HCl:H20).
DeSalvo, Song and Ma are considered to be analogous to the claimed invention because they are in the same field of III-V semiconductor layers.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed method to add performing a separate second wet etchant step as taught by DeSalvo.
Doing so would realize a wet chemical digital etching better control etch depth and to save processing time (DeSalvo: p. 3653, para. 4-5).
Response to Arguments
Applicant’s arguments with respect to claims 1-18 and 21-24 have 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.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to ZHIJUN XU whose telephone number is (571)270-3447. The examiner can normally be reached Monday-Thursday 9am-5pm ET.
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/ZHIJUN XU/Examiner, Art Unit 2818
/DUY T NGUYEN/Primary Examiner, Art Unit 2818 3/3/26