Nitride semiconductor, semiconductor device, and method for manufacturing nitride semiconductor

According to one embodiment, a nitride semiconductor includes a base body, a nitride member, and an intermediate region provided between the base body and the nitride member. The nitride member includes a first nitride region including Alx1Ga1-x1N (0<x1≤1), and a second nitride region including Alx2Ga1-x2N (0≤x2<1, x2<x1). The first nitride region is between the intermediate region and the second nitride region. The intermediate region includes nitrogen and carbon. A concentration of carbon in the intermediate region is not less than 1.5×1019/cm3 and not more than 6×1020/cm3.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-132234, filed on Aug. 16, 2021; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein generally relate to a nitride semiconductor, a semiconductor device and a method for manufacturing a nitride semiconductor.

BACKGROUND

For example, a semiconductor device is manufactured using a wafer including a nitride semiconductor. Suppression of warpage is desired.

DETAILED DESCRIPTION

According to one embodiment, a nitride semiconductor includes a base body, a nitride member, and an intermediate region provided between the base body and the nitride member.

The nitride member includes a first nitride region including Alx1Ga1-x1N (0<x1≤1), and a second nitride region including Alx2Ga1-x2N (0≤x2<1, x2<x1). The first nitride region is between the intermediate region and the second nitride region.

The intermediate region includes nitrogen and carbon. A concentration of carbon in the intermediate region is not less than 1.5×1019/cm3and not more than 6×1020/cm3.

First Embodiment

FIG.1is a schematic cross-sectional view illustrating a nitride semiconductor according to a first embodiment.

As shown inFIG.1, the nitride semiconductor110according to the embodiment includes a base body18s, a nitride member10M, and an intermediate region11M. The intermediate region11M is provided between the base body18sand the nitride member10M. A wafer210includes a nitride semiconductor110.

The base body18sincludes, for example, silicon. The base body18sis, for example, a silicon substrate.

The nitride member10M includes a first nitride region11and a second nitride region12. The first nitride region11is provided between the intermediate region11M and the second nitride region12.

The nitride member10M may include a third nitride region13, a fourth nitride region14, a fifth nitride region15, and the like. The fourth nitride region14and the fifth nitride region15correspond to a functional layer. The third nitride region13, the fourth nitride region14, and the fifth nitride region15are provided as necessary and may be omitted. At least one of the third nitride region13, the fourth nitride region14, and the fifth nitride region15may be considered to be included in the second nitride region12.

The first nitride region11includes Alx1Ga1-x1N (0<x1≤1). The composition ratio x1 of Al in the first nitride region11is, for example, not less than 0.35 and not more than 1. In one example, the first nitride region11includes AlN.

A direction from the first nitride region11to the second nitride region12is defined as a first direction. The first direction is a Z-axis direction. One direction perpendicular to the Z-axis direction is defined as an X-axis direction. The direction perpendicular to the Z-axis direction and the X-axis direction is defined as a Y-axis direction.

The base body18s, the intermediate region11M, the first nitride region11and the second nitride region12are layered along the X-Y plane.

For example, the intermediate region11M is in contact with the base body18s. For example, the intermediate region11M is in contact with the first nitride region11. For example, the first nitride region11is in contact with the second nitride region12.

For example, at least a part of the intermediate region11M may include aluminum. For example, at least a part of the intermediate region11M may include silicon.

The intermediate region11M includes nitrogen and carbon. A concentration of carbon in the intermediate region11M is not less than 1.5×1019/cm3and not more than 6×1020/cm3. The concentration of carbon in the intermediate region11M may be not less than 3×1019/cm3and not more than 4×1020/cm3.

It has been found that by providing such an intermediate region11M, warpage can be suppressed in the nitride semiconductor110(for example, the wafer210).

FIG.2is a graph illustrating the nitride semiconductor according to the first embodiment.

FIG.2illustrates the results of SIMS (Secondary Ion Mass Spectrometry) analysis of the nitride semiconductor110. InFIG.2, the horizontal axis is the position pZ in the Z-axis direction. The vertical axis on the left side ofFIG.2is the concentration of carbon C (C) or the silicon concentration C (Si). The vertical axis on the right side ofFIG.2is the secondary ion strength Int_Al of Al or the secondary ion strength Int_N of N.

As shown inFIG.2, the intermediate region11M is provided between the base body18sand the first nitride region11. The intermediate region11M includes carbon. The intermediate region11M includes nitrogen. In this example, the intermediate region11M includes aluminum and silicon. The base body18ssubstantially does not include nitrogen. The intermediate region11M, the first nitride region11and the second nitride region12include nitrogen.

As will be described later, such an intermediate region11M is obtained by supplying a first gas including carbon to the base body18s, then stopping the supply of the first gas including carbon, and supplying a second gas including nitrogen, and after that, forming the first nitride region11and the second nitride region12.

The concentration of carbon C (C) in the intermediate region11M can be controlled by, for example, the supply amount of the first gas including carbon. The concentration of carbon C (C) in the intermediate region11M can also be controlled by, for example, a temperature of a heat treatment of the base body18s. When the supply amount of the first gas is large, the concentration of carbon C (C) in the intermediate region11M becomes high. When the heat treatment temperature is low, the concentration of carbon C (C) in the intermediate region11M becomes high.

Hereinafter, an example of experimental results regarding the change in warpage when the concentration of carbon C (C) is changed will be described.

FIG.3is a graph illustrating the nitride semiconductor according to the first embodiment.

The horizontal axis ofFIG.3is the concentration of carbon CC1in the intermediate region11M. The vertical axis ofFIG.3is a warp amount W1of the wafer210. The warp amount W1is standardized based on a warp amount when the intermediate region11M is not provided (a first reference example). In the first reference example, the first nitride region11is in contact with the base body18s. In this experimental example, the amount of warpage in the first reference example is about 170 μm.

As shown inFIG.3, when the concentration of carbon CC1in the intermediate region11M is not less than 1.5×1019/cm3and not more than 6×1020/cm3, the warp amount W1is small. When the concentration of carbon CC1is less than 1.5×1019/cm3, the warpage amount of W1is large. When the concentration carbon CC1exceeds 6×1020/cm3, the warpage amount W1is large.

In the first reference example, the warp is caused by, for example, a stress generated between the base body18sand the nitride member10M. The stress is caused by, for example, a difference in the coefficient of thermal expansion between the base body18sand the nitride member10M.

Warpage can be suppressed when the concentration of carbon CC1in the intermediate region11M is not less than 1.5×1019/cm3and not more than 6×1020/cm3. It is considered that the stress is relaxed by providing the intermediate region11M having such a concentration of carbon CC1between the base body18sand the nitride member10M. As a result, warpage can be suppressed.

As shown inFIG.3, the characteristics of the concentration of carbon CC1and the warp amount W1in the intermediate region11M are critical. The warpage amount W1changes abruptly when the concentration of carbon CC1is in the vicinity of about 1.5×1019/cm3. The warpage amount W1changes abruptly when the concentration of carbon CC1is in the vicinity of about 6×1020/cm3. As shown inFIG.3, when the concentration of carbon CC1in the intermediate region11M is not less than 3×1019/cm3and 4×1020/cm3, the warp amount W1is smaller.

As shown inFIG.2, for example, the first nitride region11substantially does not include carbon. Alternatively, the concentration of carbon C (C) in the first nitride region11is lower than the concentration of carbon C (C) in the intermediate region11M. By the concentration of carbon C (C) in the first nitride region11being low, a defect density tends to be low, for example, in the nitride member10M. For example, the strain applied to the second nitride region12becomes large. This reduces defects.

As shown inFIG.2, for example, the second nitride region12includes carbon. The concentration of carbon C (C) in the second nitride region12is higher than the concentration of carbon C (C) in the first nitride region11. By the second nitride region12including carbon, it is easy to obtain a low dislocation density in, for example, the nitride member10M. For example, dislocations are easily bent in the second nitride region12including carbon. As a result, dislocations extending above the second nitride region12along the first direction (Z-axis direction) are reduced.

For example, the concentration of carbon C (C) in the second nitride region12is lower than the concentration of carbon C (C) in the intermediate region11M. By the concentration of carbon C (C) in the second nitride region12being not excessively high, for example, the strain applied to the second nitride region12becomes large. For example, when the second nitride region12is formed, the strain applied to the second nitride region12is less likely to be relaxed. Thereby, the warpage control becomes easier.

As shown inFIG.2, for example, the silicon concentration C (Si) in the first nitride region11is lower than the concentration of carbon C (C) in the first nitride region11. For example, a ratio of the silicon concentration C (Si) in the first nitride region11to the concentration of carbon C (C) in the first nitride region11is not less than 0.0001 and not more than 0.01. By the silicon concentration C (Si) in the first nitride region11being low, for example, when the second nitride region12is formed, the strain applied to the second nitride region12is less likely to be relaxed. This makes it easier to control the warpage.

For example, the silicon concentration C (Si) in the second nitride region12is lower than the concentration of carbon C (C) in the second nitride region12. For example, a ratio of the silicon concentration C (Si) in the second nitride region12to the concentration of carbon C (C) in the second nitride region12is not less than 0.0001 and not more than 0.1. When the silicon concentration C (Si) in the second nitride region12is low, for example, the strain applied to the second nitride region12is less likely to be relaxed. This makes it easier to control the warpage.

In the embodiment, a thickness of the intermediate region11M (an intermediate region thickness tm1(seeFIG.1)) is, for example, not less than 0.5 nm and not more than 100 nm.

A thickness of the first nitride region11(a first nitride region thickness tr1(seeFIG.1)) is, for example, not less than nm and not more than 500 nm.

A thickness of the second nitride region12(a second nitride region thickness tr2(seeFIG.1)) is, for example, not less than 50 nm and not more than 200 nm.

As shown inFIG.1, the nitride member10M may include the third nitride region13. The third nitride region13includes, for example, Alx3Ga1-x3N (0≤x3≤1). The third nitride region13includes, for example, AlGaN or GaN. As will be described later, the third nitride region13may have, for example, a stacked structure. A thickness of the third nitride region13(a third nitride region thickness tr3(seeFIG.1)) is, for example, not less than 100 nm and not more than 8000 nm.

As shown inFIG.1, as already described, the nitride member10M may include the fourth nitride region14and the fifth nitride region15. The fourth nitride region14includes Alx4Ga1-x4N (0≤x4<1). The composition ratio x4 of Al in the fourth nitride region14is, for example, not less than 0 and not more than 0.5. The fourth nitride region14includes, for example, GaN. The composition ratio x4 of Al in the fourth nitride region14is lower than the composition ratio of Al in the third nitride region13. A thickness of the fourth nitride region14(a fourth nitride region thickness tr4(seeFIG.1)) is, for example, not less than 50 nm and not more than 5000 nm.

As shown inFIG.1, the fourth nitride region14may include a first film region14aand a second film region14b. The first film region14ais provided between the third nitride region13and the second film region14b. The first film region14aincludes carbon. The second film region14bdoes not include carbon. Alternatively, a concentration of carbon in the second film region14bis lower than a concentration of carbon in the first film region14a. By providing the first film region14aincluding carbon, for example, a low dislocation density can be easily obtained. By the second film region14bhaving a low concentration of carbon, for example, high electron mobility can be easily obtained. A thickness of the first film region14a(a first film region thickness tr4a(seeFIG.1)) is, for example, not less than 100 nm and not more than 3000 nm. A thickness of the second film region14b(a second film region thickness tr4b(seeFIG.1)) is, for example, not less than 50 nm and no more than 2000 nm.

The fifth nitride region15includes Alx5Ga1-x5N (0<x5≤1, x4<x5). The composition ratio x5 of Al in the fifth nitride region15is, for example, not less than 0.05 and not more than 0.35. The fifth nitride region15is, for example, AlGaN. A thickness of the fifth nitride region15(a fifth nitride region thickness tr5(seeFIG.1)) is, for example, not less than 15 nm and not more than 50 nm. The second nitride region12is between the first nitride region11and the fifth nitride region15. The third nitride region13is between the second nitride region12and the fifth nitride region15. The fourth nitride region14is between the third nitride region13and the fifth nitride region15. The fourth nitride region14is between the second nitride region12and the fifth nitride region15.

For example, a carrier region is formed in a portion of the fourth nitride region14facing the fifth nitride region15. The carrier region is, for example, a two-dimensional electron gas.

In a semiconductor device based on the nitride semiconductor110, the carrier region is used for the operation of the semiconductor device.

The nitride member10M is formed by a MOCVD (metal organic chemical vapor deposition) method or the like using, for example, a raw material gas including a group III element (Al or Ga) and a raw material gas including a group V element (N), for example.

FIG.4is a schematic cross-sectional view illustrating a nitride semiconductor according to the first embodiment.

As shown inFIG.4, in a nitride semiconductor111and a wafer211according to the embodiment, the third nitride region13has a stacked structure.

For example, the third nitride region13includes a plurality of first regions13aand a plurality of second regions13b. In the first direction (the Z-axis direction) from the first nitride region11to the second nitride region12, one of the plurality of first regions13ais located between one of the plurality of second regions13band another one of the plurality of second regions13b. The one of the plurality of second regions13bis located between the one of the plurality of first regions13aand another one of the plurality of first regions13a. For example, the first region13aand the second region13bare alternately provided along the Z-axis direction.

The Al composition ratio (a composition ratio y1) in the first region13ais, for example, not less than 0.75 and not more than 1. In one example, the first region13ais AlN.

The Al composition ratio (a composition ratio y2) in the second region13bis, for example, not less than 0.06 and not more than 0.3. In one example, the second region13bis Al0.13Ga0.87N.

In one example, the composition ratio y1 is not more than the composition ratio x1. In one example, the composition ratio y2 is higher than the composition ratio x2.

For example, one of the plurality of first regions13amay be in contact with the second nitride region12. For example, one of the plurality of second regions13bmay be in contact with the second nitride region12. For example, one of the plurality of first regions13amay be in contact with the fourth nitride region14. For example, one of the plurality of second regions13bmay be in contact with the fourth nitride region14. The plurality of first regions13aand the plurality of second regions13bmay form, for example, a superlattice structure. The absolute value of the difference between the number of the plurality of first regions13aand the number of the plurality of second regions13bmay be 0 or 1. The number of the plurality of first regions13ais, for example, not less than 10 and not more than 200. One of the plurality of first regions13amay be regarded as the second nitride region12.

Each of the plurality of first regions13ahas a first region thickness t1along the first direction (the Z-axis direction). For example, the first region thickness t1is thinner than the second nitride region thickness tr2along the first direction of the second nitride region12. Each of the plurality of second regions13bhas a second region thickness t2along the first direction. For example, the second region thickness t2is thinner than the second nitride region thickness tr2. For example, the first region thickness t1is thinner than the second region thickness t2.

For example, the thickness t1of the first region along the first direction of each of the plurality of first regions13ais thinner than the thickness tr1of the first nitride region along the first direction of the first nitride region11. The second region thickness t2along the first direction of each of the plurality of second regions13bis thinner than the first nitride region thickness tr1.

The region thickness t1is, for example, not less than 3 nm and not more than 10 nm. In one example, the first region thickness t1is 5 nm. The second region thickness t2is, for example, not less than 15 nm and not more than 40 nm. In one example, the second region thickness t2is 25 nm.

In the third nitride region13having such a structure, for example, at the interface between the first region13aand the second region13b, dislocations tend to bend. It is easy to obtain a lower dislocation density. By providing a plurality of regions having different Al composition ratio, for example, high breakdown voltage can be easily obtained.

Hereinafter, an example of a method for manufacturing the nitride semiconductor111(wafer211) will be described.

The base body18sis treated by organic cleaning and acid cleaning. The base body18sis introduced into an MOCVD apparatus. The surface of the base body18sis heat treated at 1000° C. in a hydrogen atmosphere. By the heat treatment, for example, an oxide film on the surface of the base body18sis removed.

After that, the intermediate region11M is formed. For example, at 580° C., a first gas including carbon is supplied. As a result, carbon adheres to the surface of the base body18s. The first gas including carbon includes, for example, trimethylaluminum (TMAI). The first gas including carbon may include, for example, a hydrocarbon gas such as acetylene or ethylene. After that, the supply of the first gas including carbon is stopped.

After that, a second gas including nitrogen is supplied. The second gas includes, for example, ammonia (NH3). In supplying the second gas, the temperature is changed, for example, from 580° C. to 1040° C. By supplying the second gas, the intermediate region11M is formed.

The concentration of carbon C (C) in the intermediate region11M can be controlled by, for example, the supply amount of the first gas including carbon (for example, partial pressure) or the supply time of the first gas. The concentration of carbon C (C) in the intermediate region11M may be controlled by the temperature of the base body18s. For example, by increasing the supply amount of the first gas, the concentration of carbon C (C) in the intermediate region11M increases. By increasing the supply time of the first gas, the concentration of carbon C (C) in the intermediate region11M increases. When the temperature of the base body18sis low, the concentration of carbon C (C) in the intermediate region11M increases. In the forming the intermediate region11M, the temperature of the base body18swhen the second gas is supplied is, for example, not less than 550° C. and not more than 800° C.

After the above supply of the second gas, the first nitride region11is formed. For example, an AlN layer served as the first nitride region11is formed at 1040° C. by using TMAI and NH3. The thickness of the first nitride region11(the first nitride region thickness tr1) is, for example, 150 nm (for example, not less than 5 nm and not more than 500 nm). For example, the first nitride region11does not include carbon. For example, the concentration of carbon in the first nitride region11is lower than the concentration of carbon in the intermediate region11M. For example, the ratio of the concentration of carbon in the first nitride region11to the concentration of carbon in the intermediate region11M is not more than 0.05. For example, the ratio of the concentration of carbon in the first nitride region11to the concentration of carbon in the intermediate region11M may be not less than 0.0001. For example, the oxygen concentration in the first nitride region11is lower than the oxygen concentration in the intermediate region11M. For example, the ratio of the oxygen concentration in the first nitride region11to the oxygen concentration in the intermediate region11M is not more than 0.05. The ratio of the oxygen concentration in the first nitride region11to the oxygen concentration in the intermediate region11M may be not less than 0.0001.

After that, the second nitride region12is formed. For example, an AlGaN layer served as at least part of the second nitride region12is formed at 960° C. by using TMAI, trimethylgallium (TMGa) and ammonia. The AlGaN layer is, for example, a carbon-doped Al0.12Ga0.88N layer. The thickness of the second nitride region12(the second nitride region thickness tr2) is, for example, 250 nm (for example, not less than 50 nm and not more than 2000 nm). The concentration of carbon C (C) in the second nitride region12is, for example, 4.0×1018/cm3. The oxygen concentration in the second nitride region12is, for example, 7.9×1015/cm3. For example, the concentration of carbon in the second nitride region12is lower than the concentration of carbon in the intermediate region11M. For example, the concentration of carbon in the second nitride region12is higher than the concentration of carbon in the first nitride region11. For example, the oxygen concentration in the second nitride region12is lower than the oxygen concentration in the intermediate region11M. For example, the oxygen concentration in the second nitride region12is lower than the oxygen concentration in the first nitride region11.

After that, the third nitride region13is formed. For example, the third nitride region13includes a plurality of first regions13aand a plurality of second regions13b. For example, an AlN layer served as the first region13ais formed in an atmosphere including nitrogen and hydrogen using TMAI and ammonia. The temperature at which the first region13ais formed is, for example, 940° C. The thickness of the first region13a(the first region thickness t1) is, for example, 5 nm (for example, not less than 2 nm and not more than 15 nm).

On the first region13a, an Al0.13Ga0.87N layer serves as the second region13bis formed using TMAI, TMGa and ammonia. The temperature at which the second region13bis formed is, for example, 940° C. The thickness of the second region13b(the second region thickness t2) is, for example, 25 nm (for example, not less than 15 nm and not more than 40 nm). The forming the first region13aand the formation of the second region13bare repeated 125 times in total. A first region13ais further formed on the last second region13b. As a result, the third nitride region13is formed.

The concentration of carbon in the third nitride region13is, for example, 1.5×1019/cm3(for example, not less than 5×1018/cm3and not more than 9×1019/cm3). The oxygen concentration in the third nitride region13is, for example, 3.9×1016/cm3(for example, not less than 5×1015/cm3and not more than 1×1017/cm3). For example, the concentration of carbon in the third nitride region13is higher than the concentration of carbon in the intermediate region11M. For example, the oxygen concentration in the third nitride region13is higher than the oxygen concentration in the intermediate region11M. For example, the concentration of carbon in the third nitride region13is higher than the concentration of carbon in the second nitride region12. For example, the oxygen concentration in the third nitride region13is higher than the oxygen concentration in the second nitride region12. For example, the concentration of carbon in the third nitride region13is higher than the concentration of carbon in the first nitride region11. For example, the oxygen concentration in the third nitride region13is lower than the oxygen concentration in the first nitride region11.

After that, the temperature of the base body18sis set to, for example, 940° C., and the first film region14ais formed in a hydrogen atmosphere using TMGa and ammonia. The first film region14ais, for example, a GaN layer. The first film region14aincludes carbon. The thickness of the first film region14ais, for example, 1000 nm (for example, not less than 600 nm and not more than 3000 nm). The concentration of carbon in the first film region14ais, for example, 3×1019/cm3(for example, not less than 5×1018/cm3and not more than 9×1019/cm3).

After that, the temperature of the base body18sis set to, for example, 1040° C., the second film region14bis formed using TMGa and ammonia. The second film region14bis, for example, an undoped GaN layer. The thickness of the second film region14bis, for example, 500 nm (for example, not less than 50 nm and not more than 2000 nm).

After that, the temperature of the base body18sis set to, for example, 1020° C., and the fifth nitride region15is formed using TMGa, TMAI and ammonia. The fifth nitride region15is, for example, an undoped Al0.2Ga0.8N layer. The thickness of the fifth nitride region15is, for example, 30 nm (for example, not less than 15 nm and not more than 50 nm).

The first film region14a, the second film region14b, and the fifth nitride region15become a part of the functional layer.

Second Embodiment

The second embodiment relates to a semiconductor device.

FIG.5is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment.

As shown inFIG.5, a semiconductor device120according to the embodiment includes a nitride semiconductor (in this example, a nitride semiconductor110) according to the first embodiment, a first electrode51, a second electrode52, a second electrode, and an insulating member61.

A direction from the first electrode51to the second electrode52is along a second direction crossing the first direction (the Z-axis direction). The second direction is, for example, the X-axis direction. A position of the third electrode53in the second direction is between a position of the first electrode51in the second direction and a position of the second electrode52in the second direction.

The nitride member10M includes first to fifth nitride regions11to15. The fourth nitride region14includes a first partial region10a, a second partial region10b, a third partial region10c, a fourth partial region10d, and a fifth partial region10e. A direction from the first partial region10ato the first electrode51is along the first direction (the Z-axis direction). A direction from the second partial region10bto the second electrode52is along the first direction. The third partial region10cis between the first partial region10aand the second partial region10bin the second direction (the X-axis direction). A direction from the third partial region10cto the third electrode53is along the first direction. The fourth partial region10dis between the first partial region10aand the third partial region10cin the second direction. The fifth partial region10eis between the third partial region10cand the second partial region10bin the second direction.

The fifth nitride region15includes a sixth partial region15fand a seventh partial region15g. The direction from the fourth partial region10dto the sixth partial region15fis along the first direction (the Z-axis direction). A direction from the fifth partial region10eto the seventh partial region15gis along the first direction.

The insulating member61is located between the nitride member10M and the third electrode53. For example, the insulating member61includes a first insulating region61p. The first insulating region61pis provided between the third partial region10cand the third electrode53in the first direction (Z-axis direction).

The semiconductor device120may include the nitride semiconductor111. In the semiconductor device120, a current flowing between the first electrode51and the second electrode52can be controlled by a potential of the third electrode53. The potential of the third electrode53is, for example, a potential based on a potential of the first electrode51. The first electrode51functions as, for example, a source electrode. The second electrode52functions as, for example, a drain electrode. The third electrode53functions as, for example, a gate electrode. In one example, the semiconductor device120is a HEMT (High Electron Mobility Transistor). According to the embodiment, it is possible to provide a semiconductor device whose characteristics can be improved.

In the semiconductor device120, at least a part of the third electrode53is between the sixth partial region15fand the seventh partial region15gin the second direction (for example, the X-axis direction). At least a part of the third electrode53may be between the fourth partial region10dand the fifth partial region10ein the second direction (for example, the X-axis direction). The semiconductor device120is, for example, of a normally-off type.

FIG.6is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment.

As shown inFIG.6, a semiconductor device121according to the first embodiment includes the nitride semiconductor (in this example, the nitride semiconductor110) according to the first embodiment, the first electrode51, the second electrode52, and the third electrodes53and the insulating member61. In the semiconductor device121, the third electrode53does not overlap the sixth partial region15fand the seventh partial region15gin the second direction (for example, the X-axis direction). The third electrode53does not overlap the fourth partial region10dand the fifth partial region10ein the second direction (for example, the X-axis direction). The semiconductor device121is, for example, of a normally-on type.

Third Embodiment

The third embodiment relates to a method for manufacturing a nitride semiconductor. The method for manufacturing a nitride semiconductor according to the third embodiment may be applied to a method for manufacturing a wafer or a method for manufacturing a semiconductor device.

FIG.7is a flowchart illustrating a method for manufacturing a nitride semiconductor according to the third embodiment.

As shown inFIG.7, in the method for producing a nitride semiconductor according to the embodiment, the first gas including carbon is supplied onto the base body18s(step S120). After the supplying the first gas, the second gas including nitrogen is supplied (step S130). The first nitride region11including Alx1Ga1-x1N (0<x1≤1) is formed on the base body18safter the supplying the second gas (step S140). After forming the first nitride region11, the second nitride region12including Alx2Ga1-x2N (0≤x2<1, x2<x1) is formed (step S150). The intermediate region11M is formed by steps S110and S120.

The intermediate region11M between the base body18sand the first nitride region11includes nitrogen and carbon. The concentration of carbon in the intermediate region11M is not less than 1.5×1019/cm3and not more than 6×1020/cm3. Warpage can be suppressed.

For example, the first gas is not supplied in at least a part of the supplying the second gas. For example, the supplying the first gas is stopped and the second gas including nitrogen is supplied (step S130). As a result, the intermediate region11M being intended can be stably formed. The base body18smay be heat treated prior to the supplying the first gas (step S110). As a result, an unnecessary layer (for example, a silicon oxide layer) on the surface of the base body18sis removed. Oxygen included in the intermediate region11M can be reduced. As a result, the intermediate region11M being intended can be stably formed.

For example, the first gas includes aluminum and carbon. For example, the second gas includes ammonia. For example, the first gas may include carbon and hydrogen. For example, the second gas may include nitrogen.

In the embodiment, information on the structure of the nitride region and the like can be obtained by, for example, electron microscope observation. Information on the composition and element concentration in the nitride region can be obtained by, for example, EDX (Energy Dispersive X-ray Spectroscopy) or SIMS (Secondary Ion Mass Spectrometry). Information on the composition in the nitride region may be obtained, for example, by X-ray reciprocal lattice space mapping.

According to the embodiment, it is possible to provide a nitride semiconductor, a semiconductor device, and a method for manufacturing a nitride semiconductor capable of suppressing warpage.

Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the embodiments of the invention are not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in nitride semiconductor such as nitride members, nitride region, base body, etc., from known art. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained.

Moreover, all nitride semiconductors, semiconductor devices, and methods for manufacturing nitride semiconductors practicable by an appropriate design modification by one skilled in the art based on the nitride semiconductors, the semiconductor devices, and the methods for manufacturing nitride semiconductors described above as embodiments of the invention also are within the scope of the invention to the extent that the purport of the invention is included.