JP5582217B2 - Method for growing gallium nitride based semiconductor film for gallium nitride based semiconductor electronic device, method for producing gallium nitride based semiconductor electronic device, epitaxial substrate, and gallium nitride based semiconductor electronic device - Google Patents

Description

  The present invention relates to a method for growing a gallium nitride based semiconductor film, a method for producing a gallium nitride based semiconductor electronic device, an epitaxial substrate, and a gallium nitride based semiconductor electronic device.

Patent Document 1 describes a group III nitride electronic device. The drift layer of the group III nitride electronic device is provided on the main surface of the substrate. The drift layer is made of an n-type group III nitride semiconductor having a silicon concentration of less than 1 × 10 ¹⁷ cm ⁻³ . This silicon acts as a donor. The combined off angle is 0.15 degrees or more over the entire main surface of the substrate. The carbon concentration in the drift layer is 3 × 10 ¹⁶ cm ⁻³ or less.

JP 2007-299793 A

  According to the knowledge of the inventors, the device characteristics of the group III nitride semiconductor device are sensitive not only to the crystal quality of the group III nitride semiconductor film but also to the surface orientation of the base of the group III nitride semiconductor film. .

  According to the inventors' attempts, when the off-angle of the underlying semiconductor surface is very close to zero, step flow growth hardly occurs in the growth of the epitaxial layer. In addition, carbon impurities taken into the epitaxial layer increase. The increase in carbon impurities causes carrier compensation in the epitaxial layer. These result in degradation of device characteristics. On the other hand, when the plane orientation of the underlying semiconductor surface is greatly inclined at an angle of several degrees from the c-axis, the plane orientation of the underlying crystal is greatly deviated from the c-plane. Therefore, in the growth of the epitaxial layer, the crystal grows microscopically in several plane orientations. As a result, the surface morphology becomes rough.

  The above phenomenon in crystal growth causes non-uniformity in the electric field distribution in the reverse direction in the group III nitride semiconductor device, non-uniformity in the amount of local carbon impurity incorporation, and the carrier concentration caused by the carbon impurity. Causes unevenness. It is desired to improve the device characteristics by comprehensively solving these phenomena.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for growing a gallium nitride based semiconductor film that can provide good surface morphology and a desired carrier concentration. It is another object of the present invention to provide a method for manufacturing a gallium nitride based semiconductor electronic device including the gallium nitride based semiconductor film. Another object of the present invention is to provide an epitaxial substrate including the gallium nitride based semiconductor film. Still another object of the present invention is to provide a gallium nitride semiconductor electronic device using the gallium nitride semiconductor film.

One aspect of the present invention is a method of growing a gallium nitride based semiconductor film for a gallium nitride based semiconductor electronic device . This method includes (a) preparing a substrate having a main surface made of hexagonal gallium nitride, and (b) gallium nitride having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less on the main surface of the substrate. And a step of epitaxially growing a system semiconductor film. The off-angle of the main surface of the substrate is 0.35 degree or more and 1.0 degree or less (except 0.35 degree ) in the <1-100> direction of the hexagonal gallium nitride over the whole main surface. ) And in the <1-210> direction is not less than −0.3 degrees and not more than +0.3 degrees, and the off-angle is the normal between the main surface of the substrate and the c-axis of the hexagonal gallium nitride. It is defined by the angle formed. The gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

Another aspect of the present invention is a method of fabricating a gallium nitride based semiconductor electronic device. This method includes (a) preparing a substrate having a main surface made of hexagonal gallium nitride, and (b) gallium nitride having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less on the main surface of the substrate. A step of growing an epitaxial semiconductor region including a semiconductor film, and (c) a step of forming an electrode on the epitaxial semiconductor region. The off-angle of the main surface of the substrate is 0.35 degree or more and 1.0 degree or less (except 0.35 degree ) in the <1-100> direction of the hexagonal gallium nitride over the whole main surface. ) And in the <1-210> direction is not less than −0.3 degrees and not more than +0.3 degrees, and the off-angle is the normal between the main surface of the substrate and the c-axis of the hexagonal gallium nitride. It is defined by the angle formed. The gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

Another aspect of the present invention is an epitaxial substrate for a gallium nitride based semiconductor electronic device. The epitaxial substrate includes: (a) a substrate having a main surface made of hexagonal gallium nitride; and (b) a gallium nitride system provided on the main surface of the substrate and having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less. A semiconductor film. The off-angle of the main surface of the substrate is 0.35 degree or more and 1.0 degree or less (except 0.35 degree ) in the <1-100> direction of the hexagonal gallium nitride over the whole main surface. ) And in the <1-210> direction is not less than −0.3 degrees and not more than +0.3 degrees, and the off-angle is the normal between the main surface of the substrate and the c-axis of the hexagonal gallium nitride. It is defined by the angle formed. The gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

Yet another aspect of the present invention is a gallium nitride based semiconductor electronic device. The gallium nitride based semiconductor electronic device includes (a) a support base having a main surface made of hexagonal gallium nitride, and (b) a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ provided on the main surface of the support base. The following gallium nitride based semiconductor film is provided. The off angle of the main surface of the support base is 0.35 degrees or more and 1.0 degrees or less (however, 0.35 degrees in the <1-100> direction of the hexagonal gallium nitride over the entire main surface. Except in the <1-210> direction, which is not less than −0.3 degrees and not more than +0.3 degrees, and the off-angle is the normal of the main surface of the support substrate and the c-axis of the hexagonal gallium nitride. It is defined by the angle formed by The gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

  The present inventor completed the present invention by finding the following points. When epitaxially growing a gallium nitride based semiconductor film on a substrate, a large amount of carbon impurities are taken into the gallium nitride based semiconductor film when the off angle of the substrate is less than 0.3 degrees in the <1-100> direction. Therefore, device characteristics are deteriorated. Further, when the off angle of the substrate is larger than 1.0 degree in the <1-100> direction and the off angle of the substrate is smaller than −0.3 degree and larger than +0.3 degree in the <1-210> direction, gallium nitride The surface morphology of the semiconductor film becomes rough. As a result, the flatness on the surface of the gallium nitride based semiconductor film is lost, and the device characteristics deteriorate.

Another aspect of the present invention is a method of fabricating a gallium nitride based semiconductor electronic device. This method includes (a) preparing a substrate having a main surface made of hexagonal gallium nitride, and (b) gallium nitride having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less on the main surface of the substrate. A step of growing an epitaxial semiconductor region including a semiconductor film, and (c) a step of forming an electrode on the epitaxial semiconductor region. The main surface of the substrate has first and second areas, and the epitaxial semiconductor region is provided with first and second areas provided on the first and second areas of the main surface of the substrate. The electrode is formed on a surface of the first portion, and an off angle in the first area of the main surface of the substrate is in a <1-100> direction of the hexagonal gallium nitride. 0.3 degrees or more and 1.0 degrees or less, and −0.3 degrees or more and +0.3 degrees or less in the <1-210> direction, and the off-angle is the normal of the main surface of the substrate and the hexagonal crystal It is defined by the angle between the gallium nitride and the c-axis.

  Here, when the gallium nitride based semiconductor film is epitaxially grown on the substrate, a large amount of carbon impurities are taken into the gallium nitride based semiconductor film when the off angle of the substrate is smaller than 0.3 degrees in the <1-100> direction. Therefore, device characteristics are deteriorated. Further, when the off angle of the substrate is larger than 1.0 degree in the <1-100> direction and the off angle of the substrate is smaller than −0.3 degree and larger than +0.3 degree in the <1-210> direction, gallium nitride The surface morphology of the semiconductor film becomes rough. As a result, the flatness on the surface of the gallium nitride based semiconductor film is lost, and the device characteristics deteriorate. In general, since an electrode for a gallium nitride based semiconductor electronic device is formed on the surface of the first portion, according to the present invention, it is possible to avoid device characteristic deterioration due to off-angle distribution of the substrate surface. .

Another aspect of the present invention is a method of manufacturing a gallium nitride based semiconductor electronic device. This method includes (a) preparing a substrate having a main surface made of hexagonal gallium nitride, and (b) gallium nitride having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less on the main surface of the substrate. A step of growing an epitaxial semiconductor region including a semiconductor film, and (c) a step of forming an electrode on the epitaxial semiconductor region. The off angle of the main surface of the substrate at least in the range of the electrode is 0.3 degree or more and 1.0 degree or less in the <1-100> direction of the hexagonal gallium nitride, and is −0 in the <1-210> direction. 3 degrees or more and +0.3 degrees or less, and the off-angle is defined by an angle formed between the normal line of the main surface of the substrate and the c-axis of the hexagonal gallium nitride.

  The electrode is formed on a portion of the epitaxial semiconductor region. The portion of the epitaxial semiconductor region is grown on a portion of the substrate major surface. Since the off angle in the part of the main surface of the substrate is in the above-mentioned range of the off angle, it is possible to avoid device characteristic deterioration due to the distribution of the off angle on the substrate surface.

Yet another aspect of the present invention is a gallium nitride based semiconductor electronic device. The gallium nitride based semiconductor electronic device includes (a) a support base having a main surface made of hexagonal gallium nitride, and (b) a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ provided on the main surface of the support base. The following gallium nitride based semiconductor film is provided. The main surface of the support base includes a first area and a second area surrounding the first area, and the epitaxial semiconductor region includes the first and second of the main surface of the support base. The off angle in the first area of the main surface of the support base is 0 in the <1-100> direction of the hexagonal gallium nitride. 3 degrees or more and 1.0 degrees or less, and −0.3 degrees or more and +0.3 degrees or less in the <1-210> direction, and the off-angle is the normal of the main surface of the support substrate and the hexagonal crystal. It is defined by the angle between the gallium nitride and the c-axis.

  Here, when the gallium nitride based semiconductor film is epitaxially grown on the supporting base, when the off angle of the supporting base is smaller than 0.3 degrees in the <1-100> direction, a large amount of carbon impurities are taken into the gallium nitride based semiconductor film. It is. Therefore, device characteristics are deteriorated. Further, when the off angle of the support substrate is greater than 1.0 degree in the <1-100> direction and the off angle of the support substrate is less than -0.3 degree and greater than +0.3 degree in the <1-210> direction, The surface morphology of the gallium nitride semiconductor film is roughened. As a result, the flatness on the surface of the gallium nitride based semiconductor film is lost, and the device characteristics deteriorate. In general, an epitaxial semiconductor region, which is the main path of current from an electrode for a gallium nitride based semiconductor electronic device, is provided on the first area of the support substrate. It is possible to avoid the deterioration of device characteristics due to the distribution of.

Yet another aspect of the present invention is a gallium nitride based semiconductor electronic device. The gallium nitride based semiconductor electronic device includes (a) a support base having a main surface made of hexagonal gallium nitride, and (b) a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ provided on the main surface of the support base. The following gallium nitride based semiconductor film is provided. The off angle of the main surface of the support substrate at least in the range of the semiconductor electronic device structure is 0.3 degree or more and 1.0 degree or less in the <1-100> direction of the hexagonal gallium nitride, <1-210> The off angle is defined by an angle formed between a normal line of the main surface of the support substrate and the c-axis of the hexagonal gallium nitride.

  Here, when the gallium nitride based semiconductor film is epitaxially grown on the supporting base, when the off angle of the supporting base is smaller than 0.3 degrees in the <1-100> direction, a large amount of carbon impurities are taken into the gallium nitride based semiconductor film. It is. Therefore, device characteristics are deteriorated. Further, when the off angle of the support substrate is greater than 1.0 degree in the <1-100> direction and the off angle of the support substrate is less than -0.3 degree and greater than +0.3 degree in the <1-210> direction, The surface morphology of the gallium nitride semiconductor film is roughened. As a result, the flatness on the surface of the gallium nitride based semiconductor film is lost, and the device characteristics deteriorate. According to the present invention, the epitaxial semiconductor region of the semiconductor electronic device structure that becomes a current path from the electrode for the gallium nitride based semiconductor electronic device is formed on the area having the off-angle of the desired range. Degradation of device characteristics due to the distribution of the off-angle of the surface can be avoided.

  In the present invention, (the supply molar amount of nitrogen raw material) / (the supply molar amount of group III raw material) in the growth of the gallium nitride based semiconductor film may be 1250 or more. The growth temperature in the growth of the gallium nitride based semiconductor film may be 1050 degrees Celsius or higher. According to this method, a group III nitride semiconductor film having a low carrier concentration and a low carbon concentration can be grown using growth conditions with a high degree of raw material supersaturation.

  Further, (the supply molar amount of nitrogen raw material) / (the supply molar amount of group III raw material) can be 10,000 or less. The growth temperature of the gallium nitride based semiconductor film may be 1100 degrees Celsius or less.

  In the method according to the present invention, a growth pressure in the growth of the group III nitride semiconductor film may be 200 Torr or more. This method is useful for reducing the carbon concentration of the group III nitride semiconductor film. The growth pressure in the growth of the group III nitride semiconductor film may be 300 Torr or less.

In the method according to the present invention, the growth of the gallium nitride-based semiconductor film, the metal organic vapor phase growth method is performed using a source gas containing no n-type dopant gas include organic metal source and the nitrogen source, the organic trimethyl gallium as the metal source, trimethyl aluminum, and at least one of trimethylindium is used, ammonia Ru is used as the nitrogen source, it is possible. According to this method, a so-called undoped gallium nitride based semiconductor film can be provided.

In the present invention, the gallium nitride based semiconductor film may have a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ or less. According to the present invention, a gallium nitride based semiconductor film useful for a power device is provided.

In the present invention, the thickness of the gallium nitride-based semiconductor film is Ru der than 3 micrometers. According to the present invention, a gallium nitride based semiconductor film useful for high breakdown voltage is provided. The gallium nitride based semiconductor film may have a thickness of 100 micrometers or less.

  In the present invention, the gallium nitride based semiconductor film may have a surface roughness (rms) of 1 nm or less. According to the present invention, a gallium nitride based semiconductor film having a good surface morphology is provided. This gallium nitride based semiconductor film is useful for power devices.

In the present invention, the dislocation density of the gallium nitride based semiconductor film may be 1 × 10 ⁸ cm ⁻² or less. According to the present invention, the density of electron traps in the gallium nitride based semiconductor film is reduced.

In the method according to the present invention, the gallium nitride-based semiconductor film, the carbon concentration of 1 × 10 ¹⁶ cm ^-3 ing from the gallium nitride semiconductor. According to the present invention, carrier compensation in a gallium nitride based semiconductor film can be reduced. The carbon concentration of the gallium nitride based semiconductor film is preferably 3 × 10 ¹⁵ cm ⁻³ or less.

  The method according to the present invention may further include a step of forming a Schottky electrode on the gallium nitride based semiconductor film. According to this method, it is possible to provide a gallium nitride semiconductor film having a good surface morphology for an electronic device including a Schottky electrode.

  In the present invention, it is preferable that the gallium nitride based semiconductor film form a homojunction with the surface of the substrate. For example, the gallium nitride based semiconductor film can be made of GaN, and the substrate can be made of GaN.

  The method according to the present invention may further include a step of growing another gallium nitride based semiconductor film on the gallium nitride based semiconductor film and a step of forming an ohmic electrode on the other gallium nitride semiconductor film. . The gallium nitride based semiconductor film has a first conductivity type, and the another gallium nitride based semiconductor film has a second conductivity type. The another gallium nitride based semiconductor film forms a pn junction with the gallium nitride based semiconductor film.

  According to this method, a gallium nitride-based semiconductor film having a good surface morphology can be provided in an electronic device including a pn junction.

  In the present invention, the gallium nitride based semiconductor film forms a homojunction with the surface of the substrate, and another gallium nitride based semiconductor film forms a homojunction with the surface of the gallium nitride based semiconductor film. For example, the gallium nitride based semiconductor film can be made of GaN, another gallium nitride based semiconductor film can be made of GaN, and the substrate can be made of GaN.

  The gallium nitride based semiconductor electronic device according to the present invention may further include a step of forming an insulating film having an opening on the epitaxial semiconductor region. The electrode includes a Schottky electrode connected to the epitaxial semiconductor region through the opening.

According to this gallium nitride semiconductor electronic device, an excellent figure of merit (VB ² / R _ON ) can be provided for an electronic device having a shot electrode.

  In the gallium nitride based semiconductor electronic device according to the present invention, the gallium nitride based semiconductor film is preferably made of GaN, and the substrate is preferably made of GaN. According to the present invention, an electronic device is provided using a binary compound having good crystal quality.

  In the gallium nitride based semiconductor electronic device according to the present invention, the gallium nitride based semiconductor film has a first conductivity type. The method may further include a step of growing another gallium nitride semiconductor film on the gallium nitride semiconductor film and a step of forming an insulating film having an opening on the epitaxial semiconductor region. The electrode includes an ohmic electrode connected to the epitaxial semiconductor region through the opening, and the second conductivity type gallium nitride based semiconductor film forms a pn junction with the gallium nitride based semiconductor film.

According to this gallium nitride based semiconductor electronic device, an excellent figure of merit (VB ² / R _ON ) can be provided for an electronic device having a pn junction.

  In the gallium nitride semiconductor electronic device according to the present invention, the gallium nitride semiconductor film is made of p-type GaN, the another gallium nitride semiconductor film is made of n-type GaN, and the support base is made of n-type GaN. Can do. According to the present invention, an electronic device is provided using a binary compound having good crystal quality.

  In the gallium nitride based semiconductor electronic device according to the present invention, when the first and second areas of the main surface of the support base are included, the second area of the main surface of the support base is the hexagonal gallium nitride. Including a portion having an off angle in the range of 0.3 ° or less and 1.0 ° or more in the <1-100> direction, or −0.3 ° or less and + 0.3 ° or more in the <1-210> direction. Also good. This is because the device characteristics are not very sensitive to the crystal quality of the epitaxial semiconductor region formed on the second area of the main surface of the support substrate.

  The method for producing a gallium nitride based semiconductor electronic device according to the present invention includes: (d) estimating off angles at a plurality of positions on the main surface of the substrate before growing the epitaxial semiconductor region; and (e) Dividing the main surface of the substrate into the first and second areas based on the off-angle estimation result; and (f) prior to forming the electrode, Determining an electrode arrangement on the main surface. The position of the electrode follows the electrode arrangement.

  According to this method, since the electrode arrangement is determined based on the section, it is possible to increase the number of gallium nitride based semiconductor electronic devices having electrodes located on an area of a desired off angle range. Further, according to this method, since the electrode arrangement is determined based on the section, the electrode area bonded to the desired off-angle range area can be increased.

  The method of fabricating a gallium nitride based semiconductor electronic device according to the present invention includes (g) estimating off angles at a plurality of positions on the main surface of the substrate before growing the epitaxial semiconductor region, and (h) And a step of dividing the main surface of the substrate into the first and second areas based on the off-angle estimation result. Forming the insulating film on the epitaxial semiconductor region includes growing an insulating layer on the epitaxial semiconductor region; determining an array of openings on the main surface of the substrate based on the partition; Forming an array of the openings in the insulating layer according to the determination. The position of the opening follows the electrode arrangement. Preferably, the opening is located on the first area.

  According to this method, since the opening arrangement is determined based on the section, it is possible to increase the number of gallium nitride based semiconductor electronic devices having openings provided on an area in a desired off-angle range. Further, according to this method, since the opening arrangement is determined based on the section, an area having a desired range of off-angle is exposed to the opening for metal bonding.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, there is provided a method for growing a gallium nitride based semiconductor film that can provide a good surface morphology and a good carrier concentration. In addition, according to the present invention, a method for producing a gallium nitride based semiconductor electronic device including the gallium nitride based semiconductor film is provided. Furthermore, an object of the present invention is to provide an epitaxial substrate including the gallium nitride based semiconductor film. Furthermore, according to the present invention, a gallium nitride semiconductor electronic device using the gallium nitride semiconductor film is provided.

FIG. 1 is a drawing showing a main process flow in a method for producing a gallium nitride based semiconductor electronic device and an epitaxial substrate according to the present embodiment. FIG. 2 is a drawing showing main steps in a method for producing an epitaxial substrate. FIG. 3 is a drawing showing an electronic device manufactured by the process flow shown in FIG. FIG. 4 is a drawing showing the off-angle distribution on the main surface of the epitaxial substrate E. As shown in FIG. FIG. 5 is a drawing showing the off-angle distribution of the GaN wafer in Example 1. FIG. 6 is a drawing showing a carrier density distribution in an epitaxial wafer. FIG. 7 is a drawing showing the relationship between carrier density and off-angle. FIG. 8 is a drawing showing the surface morphology over the entire main surface of the epitaxial substrate. FIG. 9 is a drawing showing the surface morphology of area (b). FIG. 10 is a drawing showing the surface morphology of area (c). FIG. 11 is a drawing showing the surface morphology of area (d). FIG. 12 is a drawing showing the surface morphology of area (e). FIG. 13 is a diagram showing the relationship between the figure of merit of an electronic device and the off angle. FIG. 14 is a drawing showing a main process flow in the method of manufacturing a gallium nitride based semiconductor electronic device and an epitaxial substrate according to the present embodiment. FIG. 15 is a drawing showing a layer structure of an electronic device and an epitaxial substrate manufactured by the process flow shown in FIG. FIG. 16 is a drawing showing an electronic device manufactured by the process flow shown in FIG.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples.

  Subsequently, referring to the attached drawings, a method for growing a gallium nitride based semiconductor film, a method for producing a gallium nitride based semiconductor electronic device, a method for producing an epitaxial substrate, an epitaxial substrate, and a gallium nitride based semiconductor electron An embodiment relating to a device will be described. Where possible, the same parts are denoted by the same reference numerals. In the following description, for example, the crystal axis direction <000-1> is shown as being opposite to the direction <0001>.

FIG. 1 is a drawing showing a main process flow in a method for producing a gallium nitride based semiconductor electronic device and an epitaxial substrate according to the present embodiment. FIG. 2 is a drawing showing the main steps in the above method. In step S101, a substrate 11 is prepared as shown in FIG. The substrate 11 has a main surface 11a and a back surface 11b made of hexagonal gallium nitride. An off angle A _OFF is defined for the entire main surface 11a. The off-angle A _OFF is the normal of the main surface 11a of the gallium nitride substrate 11 (represented by “normal vector VN”) and the c-axis (represented by “c-axis vector VC”) of the gallium nitride substrate 11. It is defined by the angle formed by The off angle A _OFF is an angle (θ _M ) in the range of not less than 0.3 degrees and not more than 1.0 degrees in the <1-100> direction of the hexagonal gallium nitride and <1-210 over the entire main surface 11a. It is defined by an angle (θ _A ) in the range of −0.3 degrees to +0.3 degrees in the> direction. This condition of the angle A _OFF is satisfied over the entire main surface 11a. The substrate 11 has conductivity, and can be made of, for example, n-type GaN. The combined off angle is defined by (θ _M ² + θ _A ² ) ^1/2 .

The substrate 11 can be a GaN wafer, for example. The dislocation density of the GaN wafer is 1 × 10 ⁸ cm ⁻² or less. The dislocation density can be 1 × 10 ⁷ cm ⁻² or less.

  An epitaxial substrate for a gallium nitride based semiconductor electronic device is produced using the substrate 11. Crystal growth can be performed, for example, by metal organic vapor phase epitaxy.

In step S102, thermal cleaning of the main surface 11a of the substrate 11 is performed. For this purpose, the substrate 11 is placed on the susceptor 10 a of the growth reactor 10 as shown in FIG. If necessary, the main surface 11a of the substrate 11 is heat-treated in an atmosphere supplied with a gas G0 containing hydrogen and ammonia. By this heat treatment, a pretreatment for epitaxial growth is performed on the main surface 11a of the substrate 11 at a temperature _TTC . The pretreatment temperature _TTC can be, for example, 1050 degrees Celsius.

  In step S103, an epitaxial semiconductor region 13 is formed on the substrate 11 on the susceptor 10a of the growth reactor 10, as shown in FIG. In order to form the epitaxial semiconductor region 13, for example, one or a plurality of gallium nitride based semiconductor layers are grown on the main surface 11 a of the substrate 11. The grown gallium nitride based semiconductor can be, for example, GaN, AlGaN, InGaN, or the like.

For example, in one embodiment, in step S104, a source gas G1 containing an organic gallium source material and a nitrogen source material is supplied to the growth reactor 10 to form a gallium nitride epitaxial film 15 having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less. It grows on the main surface 11a. The nitrogen source can be, for example, ammonia (NH ₃ ). The organic gallium raw material can be trimethylgallium (TMG), trimethylaluminum (TMAl), trimethylindium (TMIn), or the like. As the organic gallium raw material, a highly purified material is used, which has reduced impurities such as silicon.

  The growth conditions of the gallium nitride epitaxial film 15 can be as follows, for example. The supply molar ratio ([V] / [III]) between the organic gallium raw material and the nitrogen raw material can be 1250 or more. By using a high supply molar ratio, the amount of carbon occupying the group V site can be reduced. The feed molar ratio ([V] / [III]) can be 10000 or less. If the supply molar ratio ([V] / [III]) is too high, the crystal growth interface is covered with N, making it difficult for Ga to reach and increasing Ga missing defects.

The growth temperature T1 of the gallium nitride epitaxial film 15 can be 1050 degrees Celsius or higher. By keeping the growth furnace at a high temperature, decomposition of the organometallic raw material can be promoted. This high temperature growth makes it easier for hydrocarbon fragments such as methyl groups to leave the gallium atoms. The temperature T1 can be 1100 degrees Celsius or less. When the growth temperature is too high, decomposition of GaN is promoted, and N having a high vapor pressure is preferentially lost. As a result, defects due to missing N increase. According to this method, the amount of carbon acting as an acceptor in the gallium nitride epitaxial film 15 can be reduced under these conditions. Furthermore, the pressure P1 of the growth furnace 10 can be 200 Torr (1 Torr is converted to 133.322 Pa) or more. By keeping the growth furnace 10 at a high pressure, decomposition of the organometallic raw material can be promoted. This promotion can reduce the incorporation of carbon into the gallium nitride being deposited along with the gallium atoms. The pressure P1 can be 760 Torr or less. Usually, the impurity C reacts with NH ₃ to form CH ₄ (methane) and is extracted to the outside. However, when the growth pressure is low, the reaction with NH ₃ becomes dull, and the incorporation of C into the crystal increases. This is because defects increase.

  After the growth of the gallium nitride epitaxial film 15, the epitaxial substrate E can be taken out from the growth furnace 10 in step S105.

  In another embodiment, the gallium nitride epitaxial film 15 is grown in step S104, and another gallium nitride epitaxial film 17 is grown on the gallium nitride epitaxial film 15 in step S106 after step S104 and before step S105. To do. In order to grow the gallium nitride epitaxial film 17, a source gas G 1 containing an organic gallium source and a nitrogen source is supplied to the growth reactor 10. The conductivity type of the gallium nitride epitaxial film 17 can be opposite to the conductivity type of the gallium nitride epitaxial film 15, for example, another gallium nitride epitaxial film 17 shows p-type. For this purpose, a p-type dopant (for example, magnesium (Mg)) is added to the source gas when the gallium nitride epitaxial film 17 is grown. As the growth conditions of the gallium nitride epitaxial film 17, for example, the growth conditions of the gallium nitride epitaxial film 15 can be used. After the growth of the gallium nitride epitaxial film 17, the epitaxial substrate E can be taken out from the growth furnace 10 in step S105.

In the epitaxial growth on the substrate 11, threading dislocations exist in the epitaxial film 15, and these threading dislocations are inherited from the substrate 11. However, in the range of the off angle A _{OFF according} to the present embodiment, since the epitaxial film for the drift layer is grown by step flow growth, the threading dislocation density of this epitaxial film can be made smaller than the threading dislocation density of the substrate 11. . If necessary, one or more further gallium nitride based semiconductor epitaxial films can be grown on the gallium nitride epitaxial films 15 and / or 17.

  Subsequently, a process for manufacturing an electronic device is performed. In step S107, an insulating film 19 is deposited on the main surface 13a of the epitaxial semiconductor region 13 of the epitaxial substrate E shown in FIG. The insulating film 19 can be made of, for example, a silicon-based inorganic insulator, and can be made of, for example, silicon oxide, silicon nitride, or the like. The insulating film 19 has an opening 19a.

In step S108, electrodes 21a, 21b, and 21c for the gallium nitride based semiconductor electronic device are formed on the epitaxial substrate E. Through these steps, substrate products P _SH and P _PN for gallium nitride based semiconductor electronic devices are produced. As the gallium nitride semiconductor electronic device, for example, a Schottky diode, a pn junction diode, a vertical field effect transistor, a high electron mobility transistor, or the like can be manufactured. Thereafter, the substrate products P _SH and P _PN are separated to form individual gallium nitride based semiconductor electronic devices.

Referring to FIG. 3 (a), the substrate product P _SH for gallium nitride-based semiconductor electronic devices is shown. In this figure, a gallium nitride-based semiconductor electronic devices, shot keys chips barrier diode D _SH is shown. Schottky barrier diode _DSH includes a substrate (support base) 11 and a gallium nitride epitaxial film (drift layer) 15 provided on main surface 11a of substrate 11. The main surface 11a of the substrate 11 and the gallium nitride epitaxial film 15 form a junction 23a, which can be a homojunction. The electrode (anode) 21 a is provided on the gallium nitride epitaxial film 15 and is in contact with the gallium nitride epitaxial film 13 through the opening 19 a of the insulating film 19. The electrode 21a has a field plate structure, and is provided around a first portion 20a that forms a Schottky junction 23b with the gallium nitride epitaxial film 15 and an opening 19a that accommodates the first portion 20a. A second portion 20b located on the top. The edge of the second portion 20b is sufficiently separated from the edge of the opening 19a.

  The electrode (cathode) 21b is provided on the back surface 11b of the substrate 11, and the electrode 21b is formed on the entire surface of the back surface 11b, for example. The electrode 21b and the back surface 11b form a junction 23c, which can be an ohmic junction.

Since the gallium nitride epitaxial film 15 has a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ or less, it is useful for the drift layer. The thickness of the gallium nitride epitaxial film 15 can be 3 micrometers or more, and the thickness can be 100 micrometers or less. The surface roughness (rms) of the main surface of the gallium nitride epitaxial film 15 is 1 nm or less, and this film 15 has a good surface morphology. Therefore, the gallium nitride epitaxial film 15 is useful for the Schottky junction 23b.

Referring to FIG. 3 (b), a substrate product _PPN for a gallium nitride based semiconductor electronic device is shown. In this drawing, one chip of a pn junction diode _DPN is shown as a gallium nitride based semiconductor electronic device. In this drawing, one chip of a pn junction diode _DPN is shown as a gallium nitride based semiconductor electronic device. The pn junction diode _DPN includes a substrate (support base) 11, a gallium nitride epitaxial film (n-type drift layer) 15 provided on the main surface 11 a of the substrate 11, and a gallium nitride epitaxial provided on the drift layer. Film (p-type layer) 17. The main surface 11a of the substrate 11 and the gallium nitride epitaxial film 15 form a junction 23a. The gallium nitride epitaxial film 15 and the gallium nitride epitaxial film 17 form a pn junction 23d, which can be a homojunction.

  The electrode (anode) 21 c is provided on the gallium nitride epitaxial film 17 and is in contact with the epitaxial semiconductor region 13 through the opening 19 a of the insulating film 19. The electrode 21c has a field plate structure, and includes a first portion 22a that forms the ohmic junction 23e in the epitaxial semiconductor region 13, and a second portion 22b that is positioned on the insulating film 19 that defines the opening 19a. Have. The edge of the second portion 22b is sufficiently separated from the edge of the opening 19a. The electrode (cathode) 21b is provided on the back surface 11b of the substrate 11, and the electrode 21b is formed on the entire back surface 11b. The electrode 21b and the back surface 11b form a joint 23c.

Since the gallium nitride epitaxial film 15 has a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ or less, it is useful for the drift layer. The thickness of the gallium nitride epitaxial film 13 can be 3 micrometers or more, and the thickness can be 100 micrometers or less. The surface roughness (rms) of the main surface of the gallium nitride epitaxial film 15 is 1 nm or less, and this film 15 has a good surface morphology. This gallium nitride epitaxial film 15 is useful for the pn junction 23d.

  The carrier concentration of the gallium nitride epitaxial film 17 is higher than the carrier concentration of the gallium nitride epitaxial film 15. Therefore, it is useful for forming the gallium nitride epitaxial film 17. The surface roughness (rms) of the main surface of the gallium nitride epitaxial film 17 is 1 nm or less, and this film 17 has a good surface morphology. This gallium nitride epitaxial film 17 is useful for a good ohmic junction 23e.

4 is a drawing showing an example of off-angle distribution on the main surface of the epitaxial substrate E. FIG. An off angle B _OFF is defined in the entire main surface 13a of the epitaxial region 13 of the epitaxial substrate E. The off angle B _OFF is formed by the normal line of the principal surface 13a of the epitaxial region 13 (represented by “normal vector VM”) and the c axis of the epitaxial region 13 (represented by “c-axis vector VC”). Defined by angle. The off angle B _OFF is 0.3 degrees or more and 1.0 degrees or less in the <1-100> direction and −0.3 degrees in the <1-210> direction of the hexagonal gallium nitride over the entire main surface 13a. More than +0.3 degrees. This angle B _OFF is satisfied over the entire main surface 13a. The c-plane of the substrate 11 of the epitaxial substrate E may be warped, for example, in a concave shape or a convex shape. As a contribution of the warpage, an off-angle distribution is generated on the main surface 11a of the substrate 11. For example, the distribution of the off angle and the surface morphology over the entire main surface 13a can be controlled according to the curvature radius of the curvature of the c-plane. The main surface size of the substrate 11 is equal to or larger than the area of the 2 inch size substrate.

Referring to FIG. 4A, the arrangement of crystal axes on the main surface 13a of the epitaxial region 13 is shown. A line segment L1 passing near the center Ax of the main surface 13a extends from the edge E10 to the edge E20 of the main surface 13a. The line segment L1 can be defined in the <1-100> direction, for example. In the main surface 13a, the line segment L2 indicates the direction of another crystal axis obtained by rotating the line segment L1 around the c axis at an angle (+ θ1) with respect to the <1-100> axis. It extends from the edge E11 to the edge E21. In the main surface 13a, the line segment L3 indicates the direction of another crystal axis obtained by rotating the line segment L1 around the c axis at an angle (−θ1) with respect to the <1-100> axis. 13a extends from edge E12 to edge E22. The line segments L4 and L5, the line segments L6 and L7, and the line segments L8 and L9 can also be defined similarly to the line segments L1 and L2. When the line segments L0 to L8 expand according to the fan-shaped arrangement shown as an example, the entire main surface 13a is 0.3 degrees or more and 1.0 degrees or less in the <1-100> direction of the hexagonal gallium nitride. And the distribution of the off angle B _OFF can be set in the range of −0.3 degrees or more and +0.3 degrees or less in the <1-210> direction. Line segments L1-L9 do not cross each other. Also on the main surface 11a of the substrate 11, the group of crystal axes as described above can have a similar arrangement.

Referring to FIG. 4B, the off-angle distribution on the main surface 13a of the epitaxial region 13 is shown. A curve C1 passing near the center Ax of the main surface 13a extends from the edge F10 to the edge F20 of the main surface 13a. The off angle B _OFF has an equal value AG1 on the curve C1 defined on the main surface 13a. Further, the curve C2 extends from the edge F11 to the edge F21 of the main surface 13a. The off angle B _OFF has an equal value AG2 on the curve C2 defined on the main surface 13a. Further, the curve C3 extends from the edge F13 to the edge F23 of the main surface 13a. The off angle B _OFF has an equal value AG3 on the curve C3 defined on the main surface 13a. The curve C4 is defined similarly to the curves C1 to C3. For example, the relationship of value AG4 <AG3 <value AG1 <value AG2 is satisfied. The illustrated curves C1 to C4 are convex curves, starting from one point on the edge of the main surface 13a and ending at another point. Also on the main surface 11a of the substrate 11, the off angle B _OFF can have a similar distribution. Further, the equal off-angle curve is not closed on the main surface 13a. The equal off-angle curve is represented by an arc, for example.

Example 1
A free-standing GaN wafer was prepared. This GaN substrate was cut out from an ingot produced by the HVPE method. The GaN wafer has a substantial c-plane principal surface. This GaN wafer has a structure called a dot core type. The dot core type includes a plurality of first regions having a high dislocation density and a single second region having a low dislocation density. The first regions are arranged in an array. The second area surrounds the first area. The GaN wafer has a size of 2 inches and its diameter is about 50 mm. A GaN substrate having an off-angle distribution suitable for observing changes in surface morphology according to the off-angle without being affected by variations in growth conditions for each growth batch was prepared.

Referring to FIG. 5, the off-angle distribution of the GaN wafer is shown. In the GaN wafer, the A direction is defined as the m-axis (<1-100> axis) direction, and the B direction is defined as the a-axis (<1-210> axis) direction. The off-angle distribution is shown below:
With respect to direction A (<1-100> axis): -0.5 degrees to +1.5 degrees.
Regarding B direction (<1-210> axis): -1.0 degree to +1.0 degree.

The off angle at the center of the GaN substrate is 0.5 degrees in the A direction and zero degrees in the B direction. The off angle A _OFF is zero at one point on the line segment passing through the center and extending in the m-axis direction. On the line segment, the off angle in the A direction is 1.4 degrees on one point 20 mm away from the center, and the off angle in the A direction is −20 degrees on the other point 20 mm away from the center. 0.4 degrees. The off-angle distribution has 6-fold symmetry with respect to the center of the GaN substrate.

On this GaN wafer, GaN was epitaxially grown by metal organic vapor phase epitaxy. A GaN film was grown on the GaN wafer. The thickness of the GaN film was 3 μm. The following undoped deposition conditions were used in the fabrication of the epitaxial substrate:
Flow rate of trimethylgallium (TMG): 56 sccm (320 μmol / min)
Ammonia (NH ₃ ) flow rate: 9 slm (0.4 mol / min)
Susceptor temperature: 1050 degrees Celsius Furnace pressure: 200 Torr
Carrier gas flow rate: 11 slm.

  A structure for a test element group (TEG) was fabricated on the main surface of the epitaxial substrate. An array of a plurality of sections was produced on the main surface of the substrate. Each section for the TEG has a size of 2.4 mm × 3.2 mm, for example, and an ohmic electrode was formed on the back surface of the GaN wafer. Each section contained a plurality of types of characteristic evaluation devices. One characterization device includes a Schottky electrode. CV characteristics and IV characteristics were measured using the Schottky electrode and the ohmic electrode.

  FIG. 6 is a drawing showing a carrier density distribution in an epitaxial wafer. FIG. 7 is a drawing showing the relationship between carrier density and off-angle. Referring to FIGS. 6 and 7, the carrier density was reduced in the range where the off angle was less than 0.3 degrees. This decrease is caused by carrier compensation in the GaN film having an off angle of less than 0.3 degrees due to an increase in carbon impurities. With respect to the <1-100> axial direction, the carrier concentration is stable when the off-angle is in the range of 0.35 degrees to 1 degree.

  FIG. 8 is a drawing showing the surface morphology of the main surface of the epitaxial substrate. The surface morphology was observed using a microscope, an AFM, and a guide step gauge. FIG. 8A shows the entire area of the main surface associated with the off-angle distribution. Referring to FIG. 8 (a), six-fold symmetry about the c-axis appears. The main surface of the GaN wafer includes areas (b) to (e) shown in FIGS. 8 (b) to 8 (e), respectively. FIG. 8B is a drawing showing surface morphology in the vicinity of zero off angle. FIG. 8C shows a surface in a range of an off angle of 0.2 degrees to 1.0 degrees in the <1-100> direction and −0.3 degrees to +0.3 degrees in the <1-210> direction. It is drawing which shows morphology. FIG. 8D is a drawing showing the surface morphology in the area (d) sandwiched between the area (b) and the area (c) with a combined off angle of 1.0 ° or less. FIG. 8E shows the surface morphology in the area (e) exceeding the combined off angle of 1.0 degree.

Referring to FIG. 9 (a), a microscopic image representing the surface morphology of area (b) is shown, and the surface morphology includes a number of hexagonal pyramidal projections. Referring to FIG. 9B, a sketch of a microscopic image is shown, and the inclination angle α of the side surface of the hexagonal pyramid is in the range of 0.1 degree to 1.0 degree, and one side L _HEX of the bottom surface of the hexagonal pyramid is shown. Was about 50 μm to 500 μm, and the height H _HEX of the hexagonal pyramid was 200 nm to 2000 nm.

  Referring to FIG. 10 (a), a microscopic image representing the surface morphology of area (c) is shown and the surface morphology is very flat. Referring to FIG. 10 (b), a microscopic image representing the surface morphology is shown. The surface was flat and the distribution of slight roughness height was 1 nm to 10 nm. The surface roughness (rms) was 0.936 nm in an area of 100 μm × 100 μm, and the surface roughness (rms) was 5 nm or less from several observation results. When the surface showed good flatness, the surface roughness (rms) was, for example, 1 nm or less.

Referring to FIG. 11A, a microscopic image representing the surface morphology of area (d) is shown, and the surface morphology includes a large number of linear protrusions. Referring to FIG. 11 (b), a sketch of a microscopic image is shown, and the side surface inclination angle β in the cross-section of the linear protrusion is in the range of 0.1 degrees to 2.0 degrees, and the width of the linear protrusion. One side L _STRP was about 10 μm to 100 μm, and the height H _STRP of the linear protrusion was 50 nm to 500 nm.

Referring to FIG. 12 (a), a microscopic image representing the surface morphology of area (e) is shown, and the surface morphology includes a number of point-like protrusions. Referring to FIG. 12 (b), a microscopic image representing the surface morphology is shown. The height distribution of the dot-like protrusions was 10 nm to 100 nm. The surface roughness (rms) was 9.447 nm in an area of 100 μm × 100 μm. FIG. 13 is a diagram showing the relationship between the figure of merit of an electronic device and the off angle. In FIG. 13, the horizontal axis is a diagram showing the behavior of the figure of merit in the direction on the <1-100> axis. The figure of merit is defined by (VB ² / R _ON ) using the device breakdown voltage VB and the on-resistance R _ON . The figure of merit is a good value in the range of an off angle of 0.2 degrees to 1.0 degrees. The breakdown voltage and on-resistance of the device were measured using the reverse characteristics and the forward characteristics of the Schottky barrier diode. The device breakdown voltage VB is defined by the voltage when the reverse leakage current is 1 × 10 ⁻³ [A / cm ² ], and the on-resistance R _ON is 500 [A / cm ² ] in the forward direction. It is defined by the differential resistance.

  In this embodiment, the Schottky barrier diode has been described as an example, but good device characteristics can be obtained even in an electronic device having another structure, such as a pn junction diode, a vertical field effect transistor, a high electron mobility transistor, or the like.

  As described above, when a GaN semiconductor surface having an off angle of 0.3 degrees or more from the hexagonal c-axis of the GaN wafer is used, the amount of carbon impurities incorporated into the epitaxial layer is reduced, and the influence of carrier compensation is affected. Reduced. Further, the hexagonal <1-100> direction of the GaN wafer has an off angle of 0.2 degrees to 1.0 degrees and a <1-210> direction of -0.3 degrees to +0.3 degrees. When an epitaxial layer is grown on the GaN semiconductor surface, an epitaxial layer with a flat surface can be obtained. In addition, from the hexagonal c-axis of the GaN wafer, it is 0.45 ° to 0.7 ° in the <1-100> direction and −0.1 ° to + 0.1 ° in the <1-210> direction. When an epitaxial layer is grown on a GaN semiconductor surface having a corner, an even epitaxial layer can be obtained.

FIG. 14 is a drawing showing a main process flow in the method of manufacturing a gallium nitride based semiconductor electronic device and an epitaxial substrate according to the present embodiment. In step S201, the substrate 31 is prepared as shown in FIG. The substrate 11 has a main surface 31a and a back surface 31b made of hexagonal gallium nitride. The off angle A _OFF is defined on the main surface 31a. The off-angle A _OFF is defined by the angle formed between the normal vector VN of the principal surface 31a and the c-axis vector VC of gallium nitride, as with the substrate 11. The off angle A _OFF is distributed over the entire main surface 31a. The main surface 31a has a first angle area 31c and a second angle area 31d. The first angle area 31c satisfies the first angle condition AG1, and the second angle area 31d satisfies the second angle condition AG2.
First angle condition AG1: An angle (θ _M ) in the range of 0.3 ° to 1.0 ° in the <1-100> direction of the hexagonal gallium nitride and −0. An angle (θ _A ) in the range of 3 ° to + 0.3 °.
Second angle condition AG2: An angle deviating from the first angle condition.
The main surface 31a may not include the second angle area. The substrate 31 has conductivity and can be made of, for example, n-type GaN. As already explained, the combined off angle is defined by (θ _M ² + θ _A ² ) ^1/2 . The substrate 31 can be a GaN wafer, for example. The dislocation density of this GaN wafer is 1 × 10 ⁸ cm ⁻² or less. The dislocation density can be 1 × 10 ⁷ cm ⁻² or less.

  In step S202, the off angles at a plurality of positions on the main surface of the substrate 31 are estimated. The estimation of the off angle can be performed by, for example, X-ray diffraction. X-ray diffraction provides an estimate of the off angle at the measurement point. From the off angles at a plurality of measurement points, the distribution of off angles on the main surface 31a can be estimated. The estimation result of the off-angle distribution is defined by an off-angle map, for example. Referring to FIG. 8A and FIG. 8C, the off-angle distribution is such that the first angle condition AG1 extends along the <1-100> direction and the <1-210> direction and has a predetermined value. This is a region having an off-angle range. When the GaN crystal is grown so that this region is sufficiently wide, a substrate that satisfies the first angle condition AG1 can be obtained on the entire principal surface. Referring to FIG. 15B, the <1-100> axis or the <1-210> axis passes through the central area (for example, the central point) of the substrate. However, as shown in FIG. 15B, there is a substrate in which the center area 31c of the substrate satisfies the first angle condition AG1, but the periphery of the substrate surface is an area that does not satisfy the first angle condition AG1. In FIG. 15B, although the area satisfying the first angle condition AG1 is not a complicated shape, the shape of the area that can provide good device characteristics depends on the off-angle distribution of each substrate.

  In step S203, the substrate main surface 31a is partitioned based on the off-angle estimation result. By dividing the main surface 31a, the main surface 31a is divided into a first angle area and a second angle area. A region satisfying the first angle condition on the main surface 31a can provide good device characteristics.

  In step S204, thermal cleaning of the main surface 31a of the substrate 31 is performed. For this reason, this thermal cleaning can be performed in the same manner as the thermal cleaning in step S102, for example.

  An epitaxial substrate for a gallium nitride based semiconductor electronic device is produced using the substrate 31. Crystal growth can be performed, for example, by metal organic vapor phase epitaxy.

In step S205, after the substrate 31 is placed on the susceptor of the growth reactor, an epitaxial semiconductor region is formed on the main surface 31a of the substrate 31. The epitaxial semiconductor region can include one or more gallium nitride based semiconductor layers. The grown gallium nitride based semiconductor can be, for example, GaN, AlGaN, InGaN, InAlGaN, or the like. The epitaxial semiconductor region includes a gallium nitride based semiconductor film having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less. The epitaxial semiconductor region can have the same structure as the epitaxial semiconductor region 13 grown in step S103. After the growth of the gallium nitride epitaxial film, the epitaxial substrate can be removed from the growth furnace.

In step S206, prior to the formation of the electrodes, the electrode arrangement on the main surface 31a of the substrate 31 is determined based on the sections. The definition of the electrode arrangement is performed, for example, by forming an insulating film having an opening. Specifically, in step S207, an insulating layer is grown on the epitaxial substrate. This insulating layer can be made of, for example, a silicon-based inorganic insulator such as silicon oxide, and can be the same as the insulating film 19, for example. In step S208, the arrangement of openings in the main surface of the substrate is determined based on the sections. Adjustment of the position of the opening array on the epitaxial substrate is performed, for example, when aligning a photomask or reticle defining the opening with the epitaxial substrate. The arrangement of the openings may be determined so that as many openings as possible are located on the first angle area, for example. In step S209, an array of openings in the main surface of the substrate is formed based on the sections. The opening can be formed using, for example, photolithography and etching. The surface of the epitaxial semiconductor region is exposed in each opening. When all of these exposed surfaces are not formed on the main surface portion that satisfies the first angle condition, an opening arrangement that satisfies the following condition is good: provided on the main surface portion that satisfies the first angle condition An opening arrangement in which the sum of the exposed surfaces is larger than the sum of the exposed surfaces provided on the main surface portion that satisfies the second angle condition. Moreover, the opening arrangement | positioning which satisfy | fills the following conditions is good: Opening arrangement | positioning which maximizes the sum total of the exposed surface provided on the main surface part which satisfy | fills 1st angle conditions. Furthermore, the opening arrangement satisfying the following conditions is good: the number of openings in which all of the exposed surfaces are located on the main surface portion satisfying the first angle condition is the exposed surface on the main surface portion satisfying the second angle condition. An orientation arrangement that is greater than the number of openings in which all of the are located. Still further, an aperture arrangement that satisfies the following condition is preferable: an aperture arrangement that maximizes the total number of apertures where all of the exposed surfaces are located on the main surface portion that satisfies the first angle condition.

  According to this method, since the opening arrangement is determined based on the section, it is possible to increase the number of gallium nitride based semiconductor electronic devices having openings provided on an area in a desired off-angle range. Moreover, since the opening arrangement is determined based on the section, an area having an off angle within a desired range is exposed to the opening for metal bonding. Preferably, the opening is located on the first angle area.

  In step S210, an electrode array for the gallium nitride based semiconductor electronic device is formed on the epitaxial substrate. The electrode is formed in the same manner as the electrode formation in step S108. By these steps, for example, a Schottky diode, a pn junction diode, a vertical field effect transistor, a high electron mobility transistor, or the like can be manufactured as a gallium nitride semiconductor electronic device. Thereafter, the substrate product is separated to form individual gallium nitride based semiconductor electronic devices.

  According to this method, since the electrode arrangement is determined based on the section, it is possible to increase the number of gallium nitride based semiconductor electronic devices having electrodes located on an area of a desired off angle range. Although elements may be arranged at the boundaries of the sections, according to this method, since the electrode arrangement is determined based on the sections, it is possible to increase the electrode area bonded to the area of the desired off-angle range, Reduction can be suppressed.

  Here, when the gallium nitride based semiconductor film is epitaxially grown on the substrate, a large amount of carbon impurities are taken into the gallium nitride based semiconductor film when the off angle of the substrate is smaller than 0.3 degrees in the <1-100> direction. Therefore, device characteristics are deteriorated. Further, when the off angle of the substrate is larger than 1.0 degree in the <1-100> direction and the off angle of the substrate is smaller than −0.3 degree and larger than +0.3 degree in the <1-210> direction, gallium nitride The surface morphology of the semiconductor film becomes rough. As a result, the flatness on the surface of the gallium nitride based semiconductor film is lost, and the device characteristics deteriorate. According to the present invention, since the electrode for the gallium nitride based semiconductor electronic device is formed on the surface of the first angle area, it is possible to avoid device characteristic deterioration due to the off-angle distribution of the substrate surface.

  Further, the off angle of the main surface 31a of the substrate 31 at least in the range of the electrode is 0.3 degrees or more and 1.0 degrees or less in the <1-100> direction of the hexagonal gallium nitride and in the <1-210> direction. It is −0.3 degrees or more and +0.3 degrees or less. The electrode is formed on a portion of the main surface of the epitaxial semiconductor region. The portion of the epitaxial semiconductor region is grown on a portion of the substrate main surface 31a. Since the off-angle in the part of the substrate main surface 31a is in the above-mentioned off-angle range, it is possible to avoid device characteristic deterioration due to the off-angle distribution of the substrate surface 31a.

FIG. 16 is a drawing showing a layer structure of an electronic device and an epitaxial substrate manufactured by the process flow shown in FIG. The gallium nitride based semiconductor electronic device 41 includes a support base 43 having a main surface 43 a made of hexagonal gallium nitride, an epitaxial semiconductor region 45 provided on the main surface 43 a of the support base 43, and a junction with the epitaxial semiconductor region 45. A first electrode 47, an insulating film 51 having an opening 51 a defining the junction 49, and a second electrode 53 provided on the back surface 43 b of the support base 43. The epitaxial semiconductor region 45 includes a gallium nitride based semiconductor film having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less. The main surface 43a of the support base 43 has a first area 44a and a second area 44b surrounding the first area 44a. The epitaxial semiconductor region 45 includes first and second portions 46 a and 46 b provided on the first and second areas of the main surface 43 a of the support base 43. The off angle in the first area 44a of the main surface 43a of the support base 43 is not less than 0.3 degree and not more than 1.0 degree in the <1-100> direction of the hexagonal gallium nitride, and in the <1-210> direction. It is −0.3 degrees or more and +0.3 degrees or less.

  In the epitaxial growth of the epitaxial semiconductor region 45 including the gallium nitride based semiconductor film on the support base 43, when the off angle of the support base 43 is less than 0.3 degrees in the <1-100> direction, the carbon impurity is gallium nitride based. A large amount is taken into the semiconductor film. Therefore, device characteristics are deteriorated. Further, when the off angle of the support substrate is greater than 1.0 degree in the <1-100> direction and the off angle of the support substrate is less than -0.3 degree and greater than +0.3 degree in the <1-210> direction, The surface morphology of the gallium nitride based semiconductor film is roughened. As a result, the surface morphology of the epitaxial semiconductor region 45 is also roughened. Therefore, the flatness on the surface 45a of the epitaxial semiconductor region 45 is lost, and the device characteristics are deteriorated.

  According to the electronic device shown in FIG. 16, the junction 49 of the electrode 47 for the gallium nitride based semiconductor electronic device is provided on the first area 44 a of the support base 43. Therefore, it is possible to avoid device characteristic deterioration due to the off-angle distribution of the support base surface 43a. Further, according to the arrangement of the electrode 47, the epitaxial semiconductor region 45 serving as a main path of current from the electrode 47 to the electrode 53 is grown on the first area 44 a of the support base 43. Furthermore, not only the off angle of the first area 44a of the support base main surface 43a located under the electrode 47 satisfies the first angle condition, but also the third area located between the first area 44a and the second area 44b. The area 44c preferably satisfies the first angle condition. A third portion 46c of the epitaxial semiconductor region 45 is provided on the third area 44c. The first portion 46a and the third portion 46c form a semiconductor electronic device structure that serves as a current path from the electrode 47 for the gallium nitride based semiconductor electronic device. The first portion 46a and the third portion 46c are grown on a part of the main surface 43a, and this portion has an off angle in a desired range. Therefore, it is possible to avoid device characteristic deterioration due to the off-angle distribution of the support base surface 43a. The insulating film 51 covers the surface of the epitaxial semiconductor region 45 grown on the second and third areas 44b and 44c, and the off-angle of the third area 44c may not satisfy the first angle condition. It is preferable that the first angle condition is satisfied. Moreover, although it is preferable that the off-angle of the second area 44b satisfies the first angle condition, the first angle condition may not be satisfied.

  The epitaxial semiconductor region 45 may have an epitaxial structure that can provide the device structure already described with reference to FIG. The support base 43 is made of, for example, GaN. The electrode 47 can include, for example, a Schottky electrode that forms a Schottky junction with a gallium nitride based semiconductor film. This Schottky electrode preferably forms a Schottky junction with the surface of the first portion 46 a of the epitaxial semiconductor region 45. Alternatively, the electrode 47 can include, for example, an ohmic electrode that forms an ohmic junction with a gallium nitride based semiconductor film. The ohmic electrode preferably forms an ohmic junction with the surface of the first portion 46 a of the epitaxial semiconductor region 45.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

10 Growth furnace, 11, 31 substrate, 11a, 31a substrate main surface, 11b, 31b substrate back surface, A _OFF , B _OFF off angle, VN normal vector, VM normal vector, VC c-axis vector, (θ _M ² + θ _A ² ) ^1/2 synthetic off angle, 13 epitaxial semiconductor region, 13a main surface of semiconductor region, 15 gallium nitride epitaxial film, E epitaxial substrate, G1, G0 gas, 17 gallium nitride epitaxial film, 19 insulating film, 19a insulating film Aperture, P _SH , P _PN substrate product, D _SH Schottky barrier diode, D _PN pn junction diode, 23a, 23b, 23c, 23d, 23e junction, 21a electrode (anode), 21b electrode (cathode), 21c electrode, 41 Gallium nitride semiconductor electronic device, 43 support base, 43a support base main surface, 45 epitaxial semiconductor region Region, 47 first electrode, 49 junction region, 51 insulating film, 51a insulating film opening, 53 second electrode.

Claims (20)

A method for growing a gallium nitride based semiconductor film for a gallium nitride based semiconductor electronic device comprising :
Preparing a substrate having a main surface made of hexagonal gallium nitride;
And epitaxially growing a gallium nitride based semiconductor film having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less on the main surface of the substrate,
The off-angle of the main surface of the substrate is 0.35 degree or more and 1.0 degree or less (except 0.35 degree ) in the <1-100> direction of the hexagonal gallium nitride over the whole main surface. ) , And in the <1-210> direction from −0.3 degrees to +0.3 degrees,
The off-angle is defined by an angle formed between a normal line of the main surface of the substrate and a c-axis of the hexagonal gallium nitride,
The gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.   The method according to claim 1, wherein the gallium nitride based semiconductor film has a surface roughness (rms) of 5 nm or less. The method according to claim 1, wherein the gallium nitride based semiconductor film has a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ or less. The gallium nitride-based semiconductor film is made of _{Ga X In Y Al 1-XY} N (0 <X ≦ 1,0 ≦ Y <1, X + Y <1),
In the growth of the gallium nitride based semiconductor film, (the supply molar amount of nitrogen raw material) / (the supply molar amount of group III raw material) is 1250 or more,
4. The method according to claim 1, wherein a growth temperature in the growth of the gallium nitride based semiconductor film is 1050 degrees Celsius or higher.   The growth of the gallium nitride based semiconductor film is performed by a metal organic vapor phase growth method using a source gas containing an organic metal source and a nitrogen source but not an n-type dopant gas. The method according to any one of claims 1 to 4, wherein at least one of aluminum and trimethylindium is used, and ammonia is used as the nitrogen raw material. A method for fabricating a gallium nitride based semiconductor electronic device,
Preparing a substrate having a main surface made of hexagonal gallium nitride;
Growing an epitaxial semiconductor region including a gallium nitride based semiconductor film having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less on the main surface of the substrate;
Forming an electrode on the epitaxial semiconductor region,
The off-angle of the main surface of the substrate is 0.35 degree or more and 1.0 degree or less (except 0.35 degree ) in the <1-100> direction of the hexagonal gallium nitride over the whole main surface. ) In the <1-210> direction is not less than −0.3 degrees and not more than +0.3 degrees,
The off-angle is defined by an angle formed between a normal line of the main surface of the substrate and a c-axis of the hexagonal gallium nitride,
The gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less. The method according to claim 6, wherein the gallium nitride based semiconductor film has a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less and a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less.   The method according to claim 6 or 7, wherein a thickness of the gallium nitride based semiconductor film is 3 micrometers or more. A step of forming an insulating film having an opening on the epitaxial semiconductor region;
The method according to any one of claims 6 to 8, wherein the electrode includes a Schottky electrode connected to the epitaxial semiconductor region through the opening. The gallium nitride based semiconductor film is made of GaN,
The method according to claim 9, wherein the substrate is made of GaN. The gallium nitride based semiconductor film has a first conductivity type,
The method includes a step of growing a second conductivity type gallium nitride semiconductor film on the gallium nitride semiconductor film;
Forming an insulating film having an opening on the epitaxial semiconductor region,
The electrode includes an ohmic electrode connected to the epitaxial semiconductor region through the opening;
11. The method according to claim 6, wherein the second conductivity type gallium nitride based semiconductor film forms a pn junction with the gallium nitride based semiconductor film. The gallium nitride based semiconductor film is made of GaN,
The second conductivity type gallium nitride based semiconductor film is made of GaN,
The method of claim 11, wherein the substrate comprises GaN. An epitaxial substrate for a gallium nitride based semiconductor electronic device,
A substrate having a main surface made of hexagonal gallium nitride;
A gallium nitride based semiconductor film provided on the main surface of the substrate and having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
The off-angle of the main surface of the substrate is 0.35 degree or more and 1.0 degree or less (except 0.35 degree ) in the <1-100> direction of the hexagonal gallium nitride over the whole main surface. ) In the <1-210> direction is not less than −0.3 degrees and not more than +0.3 degrees,
The off-angle is defined by an angle formed between a normal line of the main surface of the substrate and a c-axis of the hexagonal gallium nitride,
An epitaxial substrate, wherein the gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.   The epitaxial substrate according to claim 13, wherein the thickness of the gallium nitride based semiconductor film is 3 micrometers or more.   The epitaxial substrate according to claim 13 or 14, wherein the gallium nitride based semiconductor film has a surface roughness (rms) of 5 nm or less. A gallium nitride based semiconductor electronic device,
A support substrate having a main surface made of hexagonal gallium nitride;
A gallium nitride based semiconductor film provided on the main surface of the support base and having a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
The off angle of the main surface of the support base is 0.35 degrees or more and 1.0 degrees or less (however, 0.35 degrees in the <1-100> direction of the hexagonal gallium nitride over the entire main surface. Except) , in the <1-210> direction is −0.3 degrees or more and +0.3 degrees or less,
The off-angle is defined by an angle formed between a normal line of the main surface of the support base and a c-axis of the hexagonal gallium nitride,
The gallium nitride based semiconductor electronic device is characterized in that the gallium nitride based semiconductor film is made of a gallium nitride semiconductor having a thickness of 3 micrometers or more and a carbon concentration of 1 × 10 ¹⁶ cm ⁻³ or less.   The gallium nitride based semiconductor electronic device according to claim 16, further comprising a Schottky electrode that forms a Schottky junction with the gallium nitride based semiconductor film. The gallium nitride based semiconductor film is made of GaN,
The gallium nitride based semiconductor electronic device according to claim 16 or 17, wherein the support base is made of GaN. Another gallium nitride based semiconductor film provided between the gallium nitride based semiconductor film and the support base;
An ohmic electrode that forms a junction with the gallium nitride based semiconductor film;
The another gallium nitride based semiconductor film has a first conductivity type,
The gallium nitride based semiconductor film has a second conductivity type,
The gallium nitride semiconductor electronic device according to claim 16, wherein the gallium nitride semiconductor film forms a pn junction with the another gallium nitride semiconductor film. The gallium nitride based semiconductor film is made of p-type GaN,
The another gallium nitride based semiconductor film is made of n-type GaN,
The gallium nitride based semiconductor electronic device according to claim 19, wherein the support base is made of n-type GaN.