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 title of the invention is not descriptive. A new title is required that is clearly indicative of the invention to which the claims are directed.
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.
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 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.
Claims 1-4, 8-14 are rejected under 35 U.S.C. 103 as being unpatentable over Ujita, and further in view of Shibata.
Regarding independent claim 1, Ujita discloses in FIG. 1 and associated text a nitride semiconductor device comprising:
a first nitride semiconductor layer made of a nitride semiconductor (elements 102 and 103; layers 102 and 103 are GaN ([0043]));
a second nitride semiconductor layer formed on the first nitride semiconductor layer and made of a nitride semiconductor having a bandgap larger than that of the first nitride semiconductor layer (element 104; channel layer 104 is made of AlGaN, which is well-known in the art to have a larger bandgap than GaN ([0048]));
a gate electrode located above the second nitride semiconductor layer (element 107); and
a source electrode (element 108) and a drain electrode (element 109) formed on the second nitride semiconductor layer,
wherein the first nitride semiconductor layer includes one or more stacked bodies (elements 102 and 103 form a stacked body), each of which includes a doped layer, which is a gallium nitride layer doped with carbon (layer 102 is disclosed as being carbon-doped gallium nitride), and a non-doped layer which is a non-doped gallium nitride layer formed on the doped layer (layer 103 is disclosed as being undoped gallium nitride), and
the non-doped layer has a bottom surface in contact with the doped layer and a top surface opposite to the bottom surface (elements 102 and 103; the bottom surface of non-doped layer 103 is shown in contact with the doped layer 102 and is shown to have a surface opposite the bottom surface).
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Ujita does not explicitly disclose that the non-doped layer includes a plurality of dislocation lines, wherein in a region below at least one of the gate electrode or the drain electrode, the number of dislocation lines passing through the top surface of the non-doped layer is smaller than the number of dislocation lines passing through the bottom surface of the non-doped layer.
However, in the same field of endeavor, Shibata discloses in FIG. 4E and associated text that:
the non-doped layer includes a plurality of dislocation lines (elements 12 and 15; dislocation lines 15 are depicted propagating through a GaN crystal 12), and
wherein in a region below at least one of the gate electrode or the drain electrode, the number of dislocation lines passing through the top surface of the non-doped layer is smaller than the number of dislocation lines passing through the bottom surface of the non-doped layer (elements 12 and 15; a greater quantity of dislocation lines 15 are depicted at the bottom of the GaN crystal 12 than at the top).
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Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita and Shibata to provide a nitride semiconductor device as taught by Ujita, but with fewer crystal defects as taught by Shibata, resulting in enhanced quality and yield in the semiconductor device (Shibata paragraphs [0090]-[0093]).
Regarding dependent claim 2, Ujita, as modified by Shibata, further discloses in Shibata FIG. 4E and 4F and associated text that a dislocation density of the non-doped layer is lower than a dislocation density of the doped layer (the dislocation lines 14 and 15 depicted have a greater density in the GaN layer formed first in the disclosed method (FIG. 4E) than in the GaN layer formed on it (FIG. 4F)). Shibata does not explicitly disclose that the aforementioned layers of high and low dislocation density correspond to a doped and non-doped layer respectively. However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita and Shibata to provide a non-doped layer with lower dislocation density than that of the non-doped layer because doing so would result in enhanced quality and yield in the non-doped layer (Shibata paragraphs [0090]-[0093]). Please refer to the following figure.
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Regarding dependent claim 3, Ujita, as modified by Shibata, further discloses in Shibata FIG. 4F and associated text each stacked body includes a plurality of dislocation lines (elements 12, 14, and 15; the stacked body in this instance being the GaN first layer completed in FIG. 4E and the subsequently deposited layer of FIG. 4F, together forming a stacked body 12, with dislocation lines 14 and 15 running throughout), and at least some of the plurality of dislocation lines are bent inside the stacked body (as depicted by the bent and curved dislocation lines 14).
Regarding dependent claim 4, Ujita, as modified by Shibata, further discloses in Shibata FIG. 4E at least some of the plurality of dislocation lines are bent at an interface (elements 15, 11, and 12; dislocation lines 15 are bent at the interface between a GaN layer 12 and substrate 11). Shibata does not explicitly disclose that the aforementioned interface corresponds to an interface between a doped layer and a non-doped layer. However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita and Shibata to provide an interface between the doped and non-doped layers wherein at least some of the dislocation lines are bent because doing so would result in lower dislocation density in the non-doped layer than that of the non-doped layer and enhanced quality and yield in the non-doped layer (Shibata paragraphs [0090]-[0093]).
Regarding dependent claim 8, Ujita, as modified by Shibata, further discloses in Ujita FIG. 1 and associated text that the number of stacked bodies included in the first nitride semiconductor layer is one, two, or three (elements 102 and 103 are layers forming a single stacked body).
Regarding dependent claim 9, Ujita, as modified by Shibata, further discloses a carbon concentration in the doped layer is 5×1017 cm-3 or more and 5×1019 cm-3 or less (Ujita [0045]; the disclosed carbon concentration of doped layer 102 is at least 5×1017 cm-3).
Regarding dependent claim 10, Ujita, as modified by Shibata, further discloses in Ujita FIG. 1 and associated text a gate layer formed on the second nitride semiconductor layer and made of a nitride semiconductor containing acceptor-type impurities (element 106; [0050]; GaN gate layer 106 contains p-type a.k.a. acceptor impurities), wherein the gate electrode is formed on the gate layer (elements 106, 107; gate 107 is on gate layer 106).
Regarding dependent claim 11, Ujita, as modified by Shibata, further discloses the gate layer is made of gallium nitride containing at least one of Mg or Zn as impurities (Ujita [0050]; the p-type, or acceptor, impurities may be Mg).
Regarding dependent claim 12, Ujita, as modified by Shibata, further discloses the second nitride semiconductor layer is made of AlxGa1-xN, where x is 0<x<0.3 (Ujita [0048]; 0.1<x<0.5). However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to try various ranges of aluminum/gallium ratios to produce an AlGaN semiconductor layer with the preferred material properties such as a larger bandgap than and similar lattice structure to an adjacent GaN semiconductor layer, since it has been held that where the general conditions of a claim are disclosed in the prior art, discovering the optimum or workable ranges involves only routine skill in the art.
Regarding dependent claim 13, Ujita, as modified by Shibata, further discloses in Ujita FIG. 6 and associated text a semiconductor substrate (element 101); and a buffer layer formed on the semiconductor substrate, wherein the first nitride semiconductor layer is formed on the buffer layer (element 121). Please refer to the following figure.
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Regarding dependent claim 14, Ujita, as modified by Shibata, further discloses in FIG. 1 and associated text the semiconductor substrate is electrically connected to the source electrode (elements 108 and 101; [0053]; the line connecting the source electrode 108 to the substrate 101 is disclosed as an electrical connection).
Claims 5-7 are rejected under 35 U.S.C. 103 as being unpatentable over Ujita, and further in view of Shibata and Lee et al. (KR 101451257 B1, hereinafter Lee).
Regarding dependent claim 5, Ujita, as modified by Shibata, discloses the nitride semiconductor device of claim 1. Ujita, as modified by Shibata, does not explicitly disclose the one or more stacked bodies include a first stacked body and a second stacked body formed on the first stacked body.
However, in the same field of endeavor, Lee discloses in FIG. 2 and associated text the one or more stacked bodies include a first stacked body and a second stacked body formed on the first stacked body (elements 120, 220; the layers are disclosed as at least one of each, a doped and an undoped nitride layer, alternately stacking).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita, Shibata, and Lee to provide a gallium nitride semiconductor with additional stacked bodies, which would result in reduced leakage current, improving the efficiency of the device.
Regarding dependent claim 6, Ujita, as modified by Shibata and Lee, further discloses in Shibata FIG. 4E and 4F and associated text a dislocation density of the non-doped layer of the second stacked body is lower than a dislocation density of the non-doped layer of the first stacked body (the dislocation lines 14 and 15 depicted have a greater density in the GaN layer formed first in the disclosed method (FIG. 4E) than in the GaN layer formed on it (FIG. 4F)). Shibata does not explicitly disclose that the aforementioned layers of high and low dislocation density correspond to a first and second stacked body, respectively. However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita, Shibata, and Lee to provide a second stacked body with lower dislocation density than that of the first stacked body because doing so would result in enhanced quality and yield in the second stacked body (Shibata paragraphs [0090]-[0093]).
Regarding dependent claim 7, Ujita, as modified by Shibata discloses the nitride semiconductor device of claim 1. They do not explicitly disclose the one or more stacked bodies are a plurality of stacked bodies, and a dislocation density of the non-doped layer is lower in the stacked body that is closer to the second nitride semiconductor layer among the plurality of stacked bodies.
However, in the same field of endeavor, Lee discloses in FIG. 2 and associated text the one or more stacked bodies are a plurality of stacked bodies (elements 120, 220; the layers are disclosed as at least one of each, a doped and an undoped nitride layer, alternately stacking).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita, Shibata, and Lee to provide a gallium nitride semiconductor with a plurality of stacked bodies, which would result in reduced leakage current, improving the efficiency of the device.
Additionally, in the same field of endeavor, Shibata discloses in Shibata FIG. 4E and 4F and associated text a dislocation density of the non-doped layer is lower in the stacked body that is closer to the second nitride semiconductor layer among the plurality of stacked bodies (the dislocation lines 14 and 15 depicted have a greater density in the GaN layer formed first in the disclosed method (FIG. 4E) than in the GaN layer formed on it (FIG. 4F)). Shibata does not explicitly disclose that the aforementioned layers of high and low dislocation density correspond to a plurality of stacked bodies. However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita, Shibata, and Lee to provide a plurality of stacked bodies with lower dislocation density in the stacked body closest to the second nitride semiconductor layer because doing so would result in enhanced quality and yield (Shibata paragraphs [0090]-[0093]).
Claim 15 is rejected under 35 U.S.C. 103 as being unpatentable over Ujita, and further in view of Shibata and Takado et al. (JP 2012109344 A, as provided by applicant, hereinafter Takado).
Regarding dependent claim 15, Ujita, as modified by Shibata, discloses the nitride semiconductor device of claim 13. They do not explicitly disclose the buffer layer includes a plurality of AlGaN layers having different aluminum compositions from one another.
However, in the same field of endeavor, Takado discloses in FIG. 4 and associated text the buffer layer includes a plurality of AlGaN layers having different aluminum compositions from one another (elements 48 and 49; first AlGaN layer 48 has an Al composition of 50% while second AlGaN layer 49 has a composition of 20%).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to combine the teachings of Ujita, Shibata, and Takado to provide a nitride semiconductor device with a buffer layer comprising a plurality of layers of AlGaN with differing Al compositions, for example, a gradient of decreasing Al composition toward the surface of the buffer layer near the first GaN semiconductor layer, resulting in improved adhesion and reduced crystal defects between the first GaN semiconductor layer and a substrate, improving yield.
Conclusion
Pertinent Art
The prior art made of record and not relied upon is considered pertinent to the applicant’s disclosure:
US 9608103 B2, an application disclosing a nitride semiconductor device with several alternately stacked layers of doped and non-doped GaN between a buffer layer and AlGaN layer.
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/EVERETT T RIRIE/Examiner, Art Unit 2897