JP2003112999A - Semiconductor substrate, semiconductor device and method for manufacturing the same, and crystal growth method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a wurtzite type substrate which is improved in the flatness of the main surface of the substrate and does not particularly contain hexagonal columnar crystals (columns). SOLUTION: The semiconductor substrate having a crystal structure of the wurtzite type has a main surface inclined about 45 to about 65 deg. in a <10-10> direction of a crystal zone axis from a (0001) face. As a result, the substrate does no contain the hexagonal columnar crystals as in the case the semiconductor crystal is grown on the semiconductor substrate having the crystalline structure of the wurtzite type having the (0001) face as its main surface like heretofore.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate having a wurtzite type crystal structure, a method for manufacturing the same, a semiconductor device using the semiconductor substrate, a method for manufacturing the same, and a crystal growth method using the semiconductor substrate. .

[0002]

2. Description of the Related Art As a conventional method of manufacturing a semiconductor substrate having a wurtzite type crystal structure (hereinafter abbreviated as wurtzite type substrate), the following methods are known.

First, a structure in which a crystal layer made of gallium nitride (GaN) is formed on a substrate made of sapphire (Al ₂ O ₃ ) has been reported (S. Nakamura:
J. Vac. Sci. Technol. A, Vol. 1
3, No. 3, P.I. 705, May / Jun 199
5) (hereinafter referred to as the first conventional example). In this case,
As shown in (a), a (0001) plane (= c plane) having a plane orientation appears on the surface of the crystal layer made of gallium nitride.

On the other hand, as shown in FIG. 6 (b), a method for growing a crystal layer made of gallium nitride having a principal plane whose plane orientation is other than the (0001) plane is disclosed in Japanese Patent No. 2743901. (Referred to as a second conventional example).
The publication discloses that a substrate made of gallium arsenide (GaAs) having a zinc blende type crystal structure has an inclination angle of more than 0 ° with reference to the (001) plane.
It is described that a semiconductor crystal made of gallium nitride is grown on the main surface having an angle of less than 5 °. The plane orientation of the surface of the grown gallium nitride crystal layer is not taught.

Further, in Japanese Unexamined Patent Publication No. 10-190059 (hereinafter, referred to as a third conventional example), the plane orientation of the main surface is determined by using a vapor phase growth method using a chloride as a raw material of a group III element. On a substrate made of (100) plane gallium arsenide, or (1
When a gallium nitride-based semiconductor is grown on a tilted substrate having a main surface tilted within 15 ° from the (00) plane, a high-quality wurtzite-type gallium nitride-based semiconductor layer whose c-axis is oriented in the [111] direction of the gallium arsenide substrate. Is growing. It is disclosed that the c-axis of this gallium nitride based semiconductor layer is inclined by about 55 ° from the direction perpendicular to the substrate surface, and the cleavage plane is the (11-20) plane perpendicular to the substrate surface. Here again, the plane orientation of the surface of the grown gallium nitride crystal layer is not taught.

[0006]

However, in the first conventional example, the surface of the gallium nitride crystal layer grown on the sapphire substrate is the (0001) plane and further includes hexagonal columnar crystals. . That is, the gallium nitride crystal layer is substantially an aggregate of many column-type crystals. As a result, a part of the columnar crystal rotates around each c-axis to generate a lattice defect, and there is a problem that the crystallinity deteriorates. Further, since the crystal growth rate is different for each columnar crystal, there is a problem that a flat surface cannot be obtained.

Further, in the first conventional example, when the crystal growth is performed by the vapor phase growth method, the crystal surface becomes a gallium surface. This corresponds to the (111) A plane in zinc blende type gallium arsenide. In general, it is difficult to grow crystals on the (111) A plane of gallium arsenide, and it is particularly difficult to grow two-dimensionally. Further, even if the (111) A plane is etched, there is a problem that flat etching is difficult to be performed. This is because the etching rate is slow and the other surface having a high etching rate is etched, resulting in an uneven etching surface. This is in good agreement with the fact that when wet etching is performed on the (0001) plane of gallium nitride, the vicinity of the etch pits is severely etched to form an uneven shape.

On the other hand, in the third conventional example, the gallium nitride grown on the substrate made of gallium arsenide has a c-axis direction inclined by about 5 ° due to the influence of strain due to the difference in lattice constant, and further has a hexagonal columnar shape. The crystal also rotates and lattice defects are introduced. Therefore, in the growth method according to the third conventional example, even if the c-axis of gallium nitride is inclined by 55 ° from the direction perpendicular to the substrate surface, the surface is formed by microcrystals of various plane orientations. There is.

Further, also in silicon carbide (SiC) forming a wurtzite type single crystal, the (0001) plane is used for the plane orientation of the surface.

It is an object of the present invention to solve the above-mentioned conventional problems, improve the flatness of the main surface of the substrate, and form a wurtzite type substrate containing no columnar crystals.

[0011]

In order to achieve the above-mentioned object, the present invention is generally used for the main surface of a wurtzite type substrate and the main surface of a substrate made of zinc blende type crystal (001).
The (10-12) plane, which is almost equivalent to the plane, is used. In the specification of the present application, a negative sign "-" in the Miller index representing a crystal plane represents an inverted value of one index following the sign.

Specifically, the semiconductor substrate according to the present invention is
A semiconductor substrate having a wurtzite crystal structure is a target, and has a main surface whose plane orientation is inclined from the (0001) plane in the <10-10> direction of the crystal zone axis by about 45 ° to about 65 °.

According to the semiconductor substrate of the present invention, the plane orientation is about 4 from the (0001) plane in the <10-10> direction of the crystal zone axis.
The plane inclined by 5 ° to about 65 ° is a plane substantially equivalent to the (001) plane of the zinc blende type crystal structure such as gallium arsenide, as described later. Since the (001) plane does not become a hexagonal columnar crystal, the crystal surface can be flattened, and the etched surface is also flattened.

Further, the two elements forming the semiconductor substrate are AX
Then, unlike the A plane in which only the first element A appears on the substrate surface, or the B plane in which only the second element X appears, a plane orientation showing a specific polarity does not appear, so that it grows on the substrate. The quality of the crystal layer is improved, and the etching surface of the substrate can be flattened.

In the semiconductor substrate of the present invention, the plane orientation of the main surface is preferably the (10-12) plane. That is, since the (10-12) plane is a plane inclined by 55 ° from the (0001) plane in the <10-10> direction of the crystal zone axis,
It is preferable because it is a plane substantially equivalent to the (001) plane of the zinc blende type crystal structure.

In the semiconductor substrate of the present invention, the plane orientation of the main surface is approximately −10 ° to + in the <1-210> direction of the zone axis.
It is preferable to incline in the range of 10 °. The (10-12) plane of the wurtzite type crystal structure is not a crystal plane which is completely equivalent to the (001) plane of the zinc blende type crystal structure, and thus the plane orientation of the main plane is set as follows. 1-210
When the tilt is adjusted in the range of −10 ° to + 10 ° in the> direction, the crystal quality of the substrate is improved.

In the semiconductor substrate of the present invention, the main surface has a plane orientation of about −10 ° to the <3-30-2> direction of the zone axis.
It is preferable to incline in the range of + 10 °. Even in this case, the crystal quality of the substrate can be improved.

In the semiconductor substrate of the present invention, it is preferable that columnar crystals do not exist in the semiconductor substrate.

The semiconductor substrate of the present invention is preferably made of a nitride such as gallium nitride, aluminum nitride or boron nitride. Alternatively, the semiconductor substrate of the present invention is preferably made of a carbide such as silicon carbide, hafnium carbide or zirconium carbide. Further, the semiconductor substrate of the present invention is preferably made of a boride such as hafnium boride or zirconium boride.

The method of manufacturing a semiconductor substrate according to the present invention is intended for a method of manufacturing a semiconductor substrate having a wurtzite type crystal structure, and the principal plane of the substrate is oriented from the (0001) plane to the crystal zone axis <10. It is provided with a step of tilting in the −10> direction by about 45 ° to about 65 °.

According to the semiconductor substrate manufacturing method of the present invention,
The orientation of the principal plane of the substrate from the (0001) plane is <1 of the crystal zone axis.
The semiconductor substrate of the present invention can be obtained because it is formed by inclining in the 0-10> direction by about 45 ° to about 65 °.

In the method for manufacturing a semiconductor substrate of the present invention,
The plane orientation of the main surface is preferably the (10-12) plane.

In the method of manufacturing a semiconductor substrate of the present invention, in the step of forming the main surface, the plane orientation of the main surface is set to <1 of the crystal zone axis.
It is preferable to incline in the −210> direction within a range of approximately −10 ° to + 10 °.

In the method of manufacturing a semiconductor substrate of the present invention, in the step of forming the main surface, the plane orientation of the main surface is set to <3 of the crystal zone axis.
It is preferable to incline in the −30-2> direction within a range of approximately −10 ° to + 10 °.

In the method for manufacturing a semiconductor substrate of the present invention, before the step of forming the main surface, a step of forming a seed crystal having a composition that constitutes the semiconductor substrate, melting the material constituting the semiconductor substrate, The method further comprises a step of forming a single crystal body that constitutes a semiconductor substrate by a pulling method in which a seed crystal is added to a molten material and pulled up, and the step of forming the main surface includes a step of slicing the single crystal body into a wafer. It is preferable to include.

In this way, a single crystal body is formed by the pulling method, and the formed single crystal body is sliced so that the (10-12) plane becomes the main surface of the substrate to produce a semiconductor substrate. In principle, crystal defects due to rotation of columnar crystals around the axis do not occur.

In the method of manufacturing a semiconductor substrate of the present invention,
It is preferable that the semiconductor substrate is made of nitride. Further, it is preferable that the semiconductor substrate is made of carbide or boride.

A semiconductor device according to the present invention includes a semiconductor substrate having a wurtzite crystal structure and a semiconductor element formed on the semiconductor substrate, and the semiconductor substrate has a plane orientation of (000).
1) The main surface is inclined from the plane in the <10-10> direction of the crystal zone axis by about 45 ° to about 65 °.

According to the semiconductor device of the present invention, since the semiconductor substrate of the present invention is used in which the main surface is flattened well and there is no lattice defect due to the rotation of columnar crystals, the semiconductor element formed on the semiconductor substrate can be manufactured. The electrical characteristics are extremely good.

In the semiconductor device of the present invention, it is preferable that the plane direction of the main surface of the semiconductor substrate is the (10-12) plane.

In the semiconductor device of the present invention, it is preferable that the plane orientation of the main surface of the semiconductor substrate is inclined in the range of −10 ° to + 10 ° in the <1-210> direction of the crystal zone axis.

Further, in the semiconductor device of the present invention, the plane orientation of the main surface of the semiconductor substrate is inclined in the range of −10 ° to + 10 ° in the <3-30-2> direction of the crystal zone axis. Is preferred.

In the semiconductor device of the present invention, it is preferable that the semiconductor substrate does not have columnar crystals.

In the semiconductor device of the present invention, the semiconductor element is preferably a light emitting element.

In this case, the light emitting element preferably has a resonator whose resonance direction is the <1-210> direction of the crystal zone axis. In the light emitting element, the resonance direction is <
It is preferable to have a resonator having a 2-1-1-2> direction. This makes it easier to cleave the end face of the resonator.

In the semiconductor device of the present invention, the semiconductor element is preferably a light receiving element.

Further, in the semiconductor device of the present invention, the semiconductor element is preferably a transistor.

In the crystal growth method according to the present invention, the plane orientation of the main surface of the semiconductor substrate having a wurtzite crystal structure is set to (000
1) From the plane, about 45 ° in the <10-10> direction of the crystal zone axis
The method includes a step of forming the substrate at a tilt of about 65 °, a step of cleaning the main surface of the semiconductor substrate with an etching solution, and a step of growing a semiconductor crystal on the cleaned main surface of the semiconductor substrate.

According to the crystal growth method of the present invention, even if the semiconductor substrate of the present invention is washed with an etching solution, the surface does not become uneven and the flatness is maintained, so that the semiconductor substrate is grown on the semiconductor substrate. The crystal quality of the resulting semiconductor crystal becomes extremely good.

In the crystal growth method of the present invention, it is preferable that the semiconductor substrate has no columnar crystals.

In the crystal growth method of the present invention, the step of forming the main surface of the semiconductor substrate includes the step of forming a seed crystal having a composition forming the semiconductor substrate and the material forming the semiconductor substrate is melted and melted. It is preferable to include a step of forming a single crystal body to be a semiconductor substrate and a step of slicing the single crystal body into a wafer by a pulling method in which a seed crystal is introduced into a material and pulled up.

In the method for manufacturing a semiconductor device according to the present invention, the plane orientation of the main surface of the semiconductor substrate having a wurtzite crystal structure is about 4 from the (0001) plane to the <10-10> direction of the crystal zone axis.
Forming at an angle of 5 ° to about 65 °; cleaning the main surface of the semiconductor substrate with an etching solution; growing a plurality of semiconductor layers on the cleaned main surface of the semiconductor substrate; Etching the layer to selectively form a resonator whose resonance direction is the <1-210> direction of the crystal zone axis.

In the method of manufacturing a semiconductor device according to the present invention, the plane orientation of the main surface of the semiconductor substrate having the wurtzite crystal structure is about 4 from the (0001) plane to the <10-10> direction of the crystal zone axis.
Forming at an angle of 5 ° to about 65 °; cleaning the main surface of the semiconductor substrate with an etching solution; growing a plurality of semiconductor layers on the cleaned main surface of the semiconductor substrate; Etching the layer to selectively form a resonator in which the resonance direction is the <2-1-1-2> direction of the crystal zone axis.

In the method of manufacturing a semiconductor device of the present invention,
It is preferable that columnar crystals do not exist in the semiconductor substrate.

In the method of manufacturing a semiconductor device of the present invention,
The step of forming the main surface of the semiconductor substrate is a step of forming a seed crystal having a composition that constitutes the semiconductor substrate, and a pulling method of melting the material that constitutes the semiconductor substrate and then adding the seed crystal to the molten material and pulling it up. Therefore, it is preferable to include a step of forming a single crystal body to be a semiconductor substrate and a step of slicing the single crystal body into a wafer.

In the method of manufacturing a semiconductor device of the present invention,
It is preferable that the semiconductor substrate is made of nitride. Further, it is preferable that the semiconductor substrate is made of carbide or boride.

[0047]

(First Embodiment) First Embodiment of the Present Invention
Embodiments will be described with reference to the drawings.

Conventionally, as shown in FIG. 6A, when a III-V group compound semiconductor is crystal-grown on a wurtzite type substrate having a wurtzite type crystal structure such as gallium nitride (GaN), A wurtzite type substrate having a main surface whose plane orientation is the (0001) plane is used. As described above, when grown on a wurtzite type substrate having a (0001) plane as a main surface, columnar crystals are included in the crystal, so that in the zinc blende type crystal structure shown in FIG. It is not possible to obtain good crystal quality as in the case of crystal growth on the (001) plane.

Therefore, as a result of various studies on the wurtzite type crystal structure, the present inventors have obtained the following findings.

That is, as shown in FIG. 1, the (10-12) plane of the wurtzite type crystal structure is substantially equivalent to the (001) plane in the zinc blende type crystal structure shown in FIG. It is a finding that there is.

Therefore, the plane orientation of the principal plane is almost equivalent to the (001) plane of the zinc blende type crystal structure (10-1).
2) When a semiconductor crystal having a wurtzite type crystal structure is grown on a wurtzite type substrate having a plane, a flat surface can be easily formed as in the case of gallium arsenide (GaAs) having a zinc blende type crystal structure. And it can be obtained reliably.

Further, for example, even if a wurtzite type substrate made of gallium nitride is etched, its main surface does not have a specific polarity which is almost equivalent to the zinc blende type (001) surface ( 10-12) surface, therefore, by wet etching using phosphoric acid or sulfuric acid,
A flat etching surface can be obtained.

FIG. 3 shows an inclination angle θ at which the (10-12) plane in the wurtzite type crystal structure is inclined with respect to the (0001) plane, and an inclination direction. As shown in FIG. 3, the inclination angle θ is 55 °, and the inclination direction is <1.
It has been confirmed that the direction is 0-10>.

Further, the inventors of the present application show (1
It has been found that when the (0-12) plane is tilted within ± 10 °, the flatness of the crystal surface is improved, and when tilted within ± 5 °, it is more preferable.

The reason why the (10-12) plane is tilted within ± 10 ° is that the atom X, which should exist in the case of the face-centered cubic lattice of the zinc blende type crystal structure, is as shown in FIG.
This is because it does not exist in the case of the close-packed lattice of the wurtzite type crystal structure, but instead exists at the lattice position of atom Y.

Thus, like ABCABC,
A zinc blende type crystal structure in which three layers are regularly stacked, and ABA
Due to the difference in the essential atomic arrangement of the wurtzite type crystal structure in which two layers are regularly stacked, such as B, the (001) plane in the zinc blende type crystal structure and the (10- 12) The surface is not a completely equivalent surface.

Therefore, in the wurtzite type crystal structure, the plane equivalent to the (001) plane of the zinc blende type crystal structure deviates within ± 5 ° from the (10-12) plane. Therefore, in the wurtzite type substrate, if the plane orientation of the main surface is tilted within ± 5 ° from the (10-12) plane, it should have a plane orientation extremely close to the (001) plane of the zinc blende type crystal structure. You can

In the (10-12) plane of the wurtzite type crystal structure, the <1-210> direction is equivalent to the <110> direction of the zinc blende type crystal structure. You may incline in the direction> ± 10 °. Further, it may be tilted within ± 10 ° in the <3-30-2> direction equivalent to the <100> direction in the zinc blende type crystal structure.

Although gallium nitride (GaN) is used as the material of the wurtzite type substrate, the material is not limited to this, and a III-V group compound semiconductor made of aluminum nitride (AlN) or boron nitride (BN) may be used. Good. Further, as a material for the wurtzite type substrate, a IV-IV group compound semiconductor made of silicon carbide (SiC), germanium carbide (GeC), or the like may be used.

Further, as the material of the substrate, ceramics made of carbide such as hafnium carbide (HfC) or zirconium carbide (ZrC), or hafnium boride (HfB ₂ )
Alternatively, a ceramic made of boride such as zirconium boride (ZrB ₂ ) may be used.

(First Method for Manufacturing Wurtzite Type Substrate)
Hereinafter, the first method of manufacturing the wurtzite type substrate configured as described above will be described.

First, the pulling direction is set to <0001> (= c
A 5 mm square seed crystal having a (axis) direction is prepared. For this seed crystal, an undoped crystal piece in which no lattice defect is introduced and which is not doped with impurities is used.

Next, the pressure is about 40,000 atm and the temperature is about 2500.
The gallium nitride is melted in a nitrogen atmosphere at 0 ° C., and a single crystal body made of gallium nitride is pulled up in the c-axis direction using the prepared seed crystal.

Next, from the formed crystal, (000
1) About 45 ° to 6 in the <10-10> direction from the (= c) plane
By slicing at an angle of 5 °, and more preferably at an angle of about 50 ° to 60 °, a wafer made of gallium nitride having the (10-12) plane or its neighboring plane as the main surface is formed.

Here, a seed crystal having the <10-12> direction of the crystal zone axis as the pulling direction may be used. In this case, the (10-12) plane can be cut by slicing the (10-12) plane perpendicularly to the pulling direction, so that the diameter of the wafer made of gallium nitride can be increased.

Next, the surface of the formed wafer is made almost mirror-like by polishing, and thereafter, etching is performed with phosphoric acid, sulfuric acid or a mixed solution thereof so as to have a more flat mirror-like surface.

As described above, according to the first manufacturing method, since the single crystal body made of gallium nitride is formed by the pulling method, the single crystal body does not include columnar crystals in principle. Furthermore, a single crystal having a wurtzite type crystal structure was sliced at an angle of about 55 ° in the <10-10> direction from the c-plane to obtain a (001) zincblende type crystal structure.
A (10-12) plane corresponding to a plane orientation extremely close to the plane or a plane in the vicinity thereof is cut out to form a wafer main surface. Therefore, even if wet etching is performed on the main surface of the wafer, the etching surface does not become uneven, and the mirror surface state can be maintained.

When aluminum is added to the molten gallium nitride at the time of pulling the single crystal, the single crystal made of aluminum gallium nitride (AlGaN) can be pulled. In addition, aluminum (A
By adding l) and boron (B) in advance, it is possible to pull up the single crystal body made of boron aluminum gallium nitride (BAlGaN).

(Crystal Growth Method) Further, when a group III-V nitride semiconductor crystal is grown on the wurtzite type substrate according to the first embodiment, again by phosphoric acid, sulfuric acid or a mixed solution thereof, The wafer surface is cleaned by etching the wafer surface and removing the surface by a thickness of about 10 nm.

Next, for example, a wurtzite type substrate cleaned by etching is put into a reaction chamber, and the wurtzite type substrate is heated to about 900 ° C. in an ammonia atmosphere by a metal organic chemical vapor deposition (MOVPE) method. .

Next, the substrate temperature is continuously raised to about 1000 ° C., and for example, at least one of gallium (Ga), aluminum (Al) and indium (In) is used as a group III source, and ammonia is used. A group III-V nitride semiconductor crystal is grown using (NH ₃ ) as a group V source.

Here, the conductivity type of the growing semiconductor crystal is n.
In the case of forming a mold, silicon (Si), tin (Sn), and oxygen (O) are doped as impurities. When the conductivity type is p-type, magnesium (Mg), zinc (Z
n), beryllium (Be) or calcium (Ca) is doped as an impurity.

(Second Method for Manufacturing Wurtzite Type Substrate)
The second manufacturing method when the wurtzite type substrate according to the first embodiment is made of silicon carbide will be described below.

First, the pulling direction is set to <0001> (= c
A 5 mm square seed crystal having a (axis) direction is prepared. For this seed crystal, an undoped crystal piece in which no lattice defect is introduced and which is not doped with impurities is used.

Next, the pressure is about 100,000 atm and the temperature is about 320.
Silicon carbide is melted in a silicon atmosphere at 0 ° C., and a single crystal made of silicon carbide is pulled up in the c-axis direction using a prepared seed crystal.

Next, from the formed crystal, (000
1) The (10-12) plane or its neighboring plane is obtained by slicing the <10-10> direction from the plane at an angle of about 45 ° to 65 °, more preferably at an angle of about 50 ° to 60 °. A wafer made of silicon carbide as a main surface is formed.

Here again, <10-12> of the crystal zone axis
You may use the seed crystal which makes a direction a pulling direction. As described above, in this case, the (10-12) plane can be cut out by slicing the (10-12) plane perpendicularly to the pulling direction, so that the diameter of the wafer made of silicon carbide can be increased. You can

Next, the surface of the formed wafer is made almost mirror-like by polishing, and thereafter, it is further mirror-likely etched by hydrofluoric acid, nitric acid or a mixed solution thereof.

As described above, according to the second manufacturing method, since the single crystal body made of silicon carbide is formed by the pulling method, the single crystal body does not include columnar crystals in principle. Furthermore, a single crystal having a wurtzite crystal structure was sliced from the c-plane in the <10-10> direction at an angle of about 55 ° to obtain a plane orientation extremely close to the (001) plane of the zinc blende type crystal structure. Then, the (10-12) plane or its vicinity is cut out to form the wafer main surface. Therefore, even if wet etching is performed on the main surface of the wafer, the etching surface does not become uneven, and the mirror surface state can be maintained.

(Crystal Growth Method) The semiconductor substrate made of silicon carbide thus formed is subjected to etching cleaning of the wafer surface with hydrofluoric acid, nitric acid or a mixed solution thereof before crystal growth to obtain a surface having a thickness of about 10 nm. The wafer is cleaned by removing the amount.

Next, for example, a semiconductor substrate that has been cleaned by etching is placed in a reaction chamber, and the wurtzite type substrate is heated to about 900 ° C. in an ammonia atmosphere by the MOVPE method.

Next, the substrate temperature is continuously raised to about 1000 ° C., and for example, at least one of gallium, aluminum, and indium is used as a group III source, and ammonia is used as a group V source, and a group III-V group is used. Growing a nitride semiconductor crystal.

(Second Embodiment) A method for manufacturing a wurtzite type substrate according to a second embodiment of the present invention will be described below.

First, as shown in FIG. 6 (a), a nitriding process is performed on a sapphire substrate having a (001) main surface by vapor deposition such as sublimation or MOVPE, as in the conventional method. A first crystal layer made of gallium having a surface plane orientation of (0001) and a thickness of at least 5 mm is grown.

Next, as shown in FIG. 3, at the angle of about 55 ° in the <10-10> direction from the (001) plane in the grown first crystal layer, the (001) of the zinc blende type crystal structure was formed. Slice so that the (10-12) plane having a plane orientation extremely close to the plane or a plane within ± 10 ° with respect to this plane becomes the main plane.

Then, a second crystal layer made of gallium nitride having a thickness of about 2 μm is grown on the formed main surface by vapor phase epitaxy, and the main surface is a (10-12) plane or this. A wurtzite type substrate having a close plane orientation is formed.

In the second embodiment, columnar crystals cannot be completely eliminated because the hexagonal rotation is present in the first crystal layer.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings.

5A to 5C show a semiconductor laser device according to a third embodiment of the present invention, in which FIG. 5A is a plane orientation of a main surface of a semiconductor substrate on which the semiconductor laser device is formed. (B) represents the forming direction of the resonator in the semiconductor laser device, and (c) represents the other forming direction of the resonator in the semiconductor laser device.

First, the forming direction of the conventional resonator will be described.

As shown in FIG. 7A, conventionally, since a resonator for laser oscillation is formed on a wurtzite type substrate whose main surface has a (0001) plane orientation, The resonance direction (laser oscillation direction), the so-called stripe direction, is the <11-20> direction indicated by reference numeral 51 or the <1-100> direction indicated by reference numeral 52.

On the other hand, in the case of the semiconductor substrate having the zinc blende type crystal structure shown in FIG. 7B, the plane orientation of its main surface is generally the (001) plane, and the stripes are as described above. The direction is the <110> direction indicated by reference numeral 53 or the <1-10> direction indicated by reference numeral 54.

From this, when the semiconductor laser device is formed on the wurtzite type substrate whose plane orientation is the (10-12) plane, as shown in FIG. It can be seen that it is preferable to select the −210> direction, or the <2-1-1-2> direction indicated by reference numeral 12, as shown in FIG.

Thus, (1-210) is formed on the end face of the resonator.
When the resonator structure having the plane or the (2-1-1-2) plane is formed, the cleavage planes of the facing end faces are parallel to each other and function as a flat resonator.

As a result, the workability of the resonator structure is improved, the luminous efficiency is improved, and long-term reliability is obtained.

The method of manufacturing the semiconductor laser device according to the third embodiment will be described below.

First, the semiconductor substrate obtained by the manufacturing method according to the first embodiment or the second embodiment, that is,
The plane orientation of the main surface is the (10-12) plane or the (10-12) plane
A wurtzite type substrate made of gallium nitride that is inclined within ± 10 ° in the <10-10> direction from the plane is prepared.

Next, the main surface of the substrate is etched and washed with phosphoric acid, sulfuric acid or a mixed solution thereof,
The main surface of the wurtzite type substrate is cleaned by removing the main surface by a thickness of about 10 nm.

Next, for example, metal organic chemical vapor deposition (MOV)
A wurtzite type substrate, which has been etched and cleaned by the PE) method, is put into a reaction chamber, and the temperature of the substrate is raised to about 900 ° C. in an ammonia atmosphere. Then, the substrate temperature is set to 10
The temperature is raised to about 00 ° C., for example, tetramethylgallium (TMG) and tetramethylaluminum (TMA) which are group III sources and ammonia (NH ₃ ) which is a group V source.
And silane gas containing n-type dopant silicon are introduced into the reaction chamber, and n-type Al is formed on the main surface of the wurtzite-type substrate.
A first clad layer made of GaN is grown.

Next, the introduction of TMA is stopped and a first optical guide layer made of n-type GaN is grown on the first cladding layer.

Then, the introduction of the silane gas is stopped and trimethylindium (TMI) is introduced instead to grow a quantum well active layer made of InGaN on the first optical guide layer.

Next, TMA is introduced instead of TMI,
Further, biscyclopentadienyl magnesium (Cp ₂ Mg) containing magnesium as a p-type dopant is introduced to grow a cap layer made of p-type AlGaN on the quantum well active layer.

Next, the introduction of TMA is stopped and a second optical guide layer made of p-type GaN is grown on the cap layer.

Next, the introduction of TMA is restarted to grow a second cladding layer made of p-type AlGaN on the second optical guide layer. After that, the introduction of TMA was stopped again,
A contact layer made of p-type GaN is grown.

Next, nickel (Ni), platinum (Pt) and Au are formed on the entire surface of the p-type contact layer by a vapor deposition method or the like.
A conductor film made of (gold) is sequentially deposited to form a first laminated conductor film. After that, the resonance direction of the laser beam is <1-210> direction or <2-1-1-2> by the lithography method.
A resist mask having a stripe pattern in the> direction is formed. Then, using the formed resist mask, the first laminated conductor film, the contact layer, the second cladding layer, and the second optical guide layer are sequentially dry-etched to form the first laminated conductor on the upper surface. A resonator structure having a p-side electrode made of a film is formed. After that, the damaged layer exposed by dry etching is removed by etching using phosphoric acid or sulfuric acid.

Next, aluminum (A) is formed on the surface opposite to the main surface of the wurtzite type substrate by a vapor deposition method or the like.
l), a second laminated conductor film made of titanium (Ti) and gold (Au) is formed to form an n-side electrode.

Next, using a wurtzite type substrate, the cavity length is about 300 μm to 1 mm and the cleavage plane is (1-21).
The semiconductor laser device is obtained by cleaving so as to form the (0) plane or the (2-1-1-2) plane.

During growth of the quantum well active layer containing indium, the substrate temperature may be lower than 1000 ° C., for example, about 800 ° C.

Further, a light emitting diode element can also be obtained by providing a structure in which the second cladding layer made of p-type AlGaN is not provided and a stripe resonator is not provided.

The semiconductor device is not limited to the light emitting element,
It may be a light receiving element or may be an active element such as a field effect transistor (FET) or a heterojunction bipolar transistor (HBT). In the case of such an active element, there is an extremely large effect in reducing the leak current.

The wurtzite type substrate is not limited to gallium nitride (GaN), but silicon carbide (SiC) may be used.

[0112]

According to the semiconductor substrate having the wurtzite crystal structure according to the present invention, the plane orientation is inclined from the (0001) plane by about 45 ° to about 65 ° in the <10-10> direction of the crystal zone axis. Since it has a major surface, (00) of the zinc blende type crystal structure
1) The surface is almost equivalent to the surface. Since the surface almost equivalent to this (001) surface does not become a hexagonal columnar crystal, the crystal surface can be flattened, and the etching surface is also flattened.

Further, since the semiconductor device according to the present invention is formed on the semiconductor substrate of the present invention which is excellent in flattening the surface, it is possible to have excellent electrical or optical characteristics.

[Brief description of drawings]

FIG. 1 is a wurtzite type crystal structure of a semiconductor substrate according to a first embodiment of the present invention, and is a schematic view showing a (10-12) plane which is a main surface of the substrate.

FIG. 2 is a zinc-blende type crystal structure having a principal surface equivalent to that of the semiconductor substrate according to the first embodiment of the present invention, and is a schematic view showing a (001) plane which is a principal surface of the substrate. .

FIG. 3 is a schematic diagram showing a wurtzite type crystal structure of the semiconductor substrate according to the first embodiment of the present invention, showing a plane in which a (10-12) plane is tilted from (0001) and tilt angles are equivalent. Is.

FIG. 4 is a schematic view showing a wurtzite type crystal structure of the semiconductor substrate according to the first embodiment of the present invention, and showing a plane equivalent to a (10-12) plane.

5A and 5B show a semiconductor laser device according to a third embodiment of the present invention, FIG. 5A is a schematic view showing a wurtzite type crystal structure of a semiconductor substrate and a plane orientation of a main surface thereof, and FIG.
FIG. 4A is a schematic diagram showing a first stripe direction in a resonator of a semiconductor laser device, and FIG. 7C is a schematic diagram showing a second stripe direction in a resonator of a semiconductor laser device.

FIG. 6A is a schematic view showing a crystal structure of a conventional wurtzite type substrate and a (0001) plane which is a main surface of the substrate. (B) is a schematic diagram showing a crystal structure of a conventional zinc blende type substrate and a (001) plane which is a main surface of the substrate.

FIG. 7A is a schematic view showing a crystal structure of a conventional wurtzite type substrate and a stripe direction of a resonator formed on a (0001) plane which is a main surface of the substrate. (B)
FIG. 3 is a schematic view showing a crystal structure of a conventional zinc blende type substrate and a stripe direction of a resonator formed on a (001) plane which is a main surface of the substrate.

[Explanation of symbols]

11 resonator 12 resonator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihiko Ishibashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yasutoshi Kawaguchi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 4G077 AA02 AA03 BE12 BE13 BE15                       CF10 ED05 FG16 HA02                 5F045 AB14 AC08 AC12 AC19 AF02                       AF04 AF13 BB16 CA12 CA13                       DA61 HA04

Claims (33)

[Claims] 1. A semiconductor substrate having a wurtzite type crystal structure, wherein a main surface having a plane orientation inclined from a (0001) plane in a <10-10> direction of a crystal zone axis by about 45 ° to about 65 °. A semiconductor substrate having. 2. The semiconductor substrate according to claim 1, wherein a plane orientation of the main surface is a (10-12) plane. 3. The plane orientation of the main surface is <1-2 of the crystal zone axis.
The semiconductor substrate according to claim 1, wherein the semiconductor substrate is inclined in the 10> direction in the range of approximately −10 ° to + 10 °. 4. The plane orientation of the main surface is <3-3 of the crystal zone axis.
The semiconductor substrate according to claim 1 or 2, wherein the semiconductor substrate is inclined in the 0-2> direction within a range of approximately -10 ° to + 10 °. 5. The semiconductor substrate according to claim 1, wherein columnar crystals do not exist in the semiconductor substrate. 6. The semiconductor substrate according to claim 1, wherein the semiconductor substrate is made of nitride. 7. The semiconductor substrate according to claim 1, wherein the semiconductor substrate is made of carbide or boride. 8. A method of manufacturing a semiconductor substrate having a wurtzite crystal structure, wherein the main surface of the substrate has a plane orientation of <0001 from a (0001) plane to a crystal zone axis.
A method of manufacturing a semiconductor substrate, comprising the step of forming the substrate by inclining it in the 0-10> direction by about 45 ° to about 65 °. 9. The method of manufacturing a semiconductor substrate according to claim 8, wherein the plane orientation of the main surface is a (10-12) plane. 10. The step of forming the main surface is characterized in that a plane orientation of the main surface is tilted in a range of about −10 ° to + 10 ° in a <1-210> direction of a crystal zone axis. The method for manufacturing a semiconductor substrate according to claim 8. 11. In the step of forming the main surface, the plane orientation of the main surface is tilted in the range of −10 ° to + 10 ° in the <3-30-2> direction of the crystal zone axis. The method for manufacturing a semiconductor substrate according to claim 8 or 9. 12. A step of forming a seed crystal having a composition that constitutes the semiconductor substrate before the step of forming the main surface; a step of melting a material that constitutes the semiconductor substrate; By the pulling method in which a seed crystal is charged and pulled up,
The method further comprising: a step of forming a single crystal body that constitutes the semiconductor substrate, wherein the step of forming the main surface includes a step of slicing the single crystal body into a wafer shape.
2. The method for manufacturing a semiconductor substrate according to any one of 1. 13. The method of manufacturing a semiconductor substrate according to claim 8, wherein the semiconductor substrate is made of nitride. 14. The method of manufacturing a semiconductor substrate according to claim 8, wherein the semiconductor substrate is made of carbide or boride. 15. A semiconductor substrate having a wurtzite crystal structure, and a semiconductor element formed on the semiconductor substrate, wherein the semiconductor substrate has a plane orientation <0001 from a (0001) plane to a crystal zone axis. A semiconductor device having a main surface inclined by about 45 ° to about 65 ° in the −10> direction. 16. The plane orientation of the main surface of the semiconductor substrate is
The semiconductor device according to claim 15, wherein the semiconductor device has a (10-12) plane. 17. The plane orientation of the main surface of the semiconductor substrate is approximately −10 ° to + 10 ° in the <1-210> direction of the crystal zone axis.
17. The semiconductor device according to claim 15, wherein the semiconductor device is inclined within the range. 18. The plane orientation of the main surface of the semiconductor substrate is approximately −10 ° to +10 in the <3-30-2> direction of the crystal zone axis.
The semiconductor device according to claim 15 or 16, wherein the semiconductor device is inclined in a range of °. 19. The semiconductor device according to claim 15, wherein columnar crystals do not exist in the semiconductor substrate. 20. The semiconductor device according to claim 15, wherein the semiconductor element is a light emitting element. 21. The semiconductor device according to claim 20, wherein the light emitting element has a resonator whose resonance direction is a <1-210> direction of a crystal zone axis. 22. The semiconductor device according to claim 20, wherein the light emitting element has a resonator whose resonance direction is a <2-1-1-2> direction of a crystal zone axis. 23. The semiconductor device according to claim 15, wherein the semiconductor element is a light receiving element. 24. The semiconductor device according to claim 15, wherein the semiconductor element is a transistor. 25. The principal plane of a semiconductor substrate having a wurtzite crystal structure has a crystallographic axis <10 from the (0001) plane.
-10> direction at an angle of about 45 ° to about 65 °, cleaning the main surface of the semiconductor substrate with an etching solution, and growing a semiconductor crystal on the cleaned main surface of the semiconductor substrate. A method of growing a crystal, comprising: 26. The crystal growth method according to claim 25, wherein columnar crystals are not present in the semiconductor substrate. 27. The step of forming the main surface of the semiconductor substrate includes the steps of forming a seed crystal having a composition forming the semiconductor substrate; melting a material forming the semiconductor substrate; By the pulling method in which a seed crystal is charged and pulled up,
26. The crystal growth method according to claim 25, comprising: a step of forming a single crystal body to be the semiconductor substrate; and a step of slicing the single crystal body into a wafer shape. 28. The principal plane of a semiconductor substrate having a wurtzite crystal structure has a plane orientation of <10 from the (0001) plane to the crystal zone axis.
-10> direction at an angle of about 45 ° to about 65 °, cleaning the main surface of the semiconductor substrate with an etching solution, and forming a plurality of semiconductor layers on the cleaned main surface of the semiconductor substrate. And a step of performing etching on the plurality of semiconductor layers to selectively form a resonator whose resonance direction is the <1-210> direction of the crystal zone axis. And a method for manufacturing a semiconductor device. 29. The principal plane of a semiconductor substrate having a wurtzite crystal structure has a plane orientation of <10 from a (0001) plane to a crystal zone axis.
-10> direction at an angle of about 45 ° to about 65 °, cleaning the main surface of the semiconductor substrate with an etching solution, and forming a plurality of semiconductor layers on the cleaned main surface of the semiconductor substrate. And a step of etching the plurality of semiconductor layers to selectively form a resonator whose resonance direction is the <2-1-1-2> direction of the crystal zone axis. A method for manufacturing a semiconductor device, comprising: 30. The method of manufacturing a semiconductor device according to claim 28, wherein columnar crystals are not present in the semiconductor substrate. 31. The step of forming the main surface of the semiconductor substrate includes the steps of forming a seed crystal having a composition forming the semiconductor substrate, melting the material forming the semiconductor substrate, and adding the melted material to the material. By the pulling method in which a seed crystal is charged and pulled up,
30. The method for manufacturing a semiconductor device according to claim 28, further comprising: a step of forming a single crystal body to be the semiconductor substrate; and a step of slicing the single crystal body into a wafer. 32. The method of manufacturing a semiconductor device according to claim 28, wherein the semiconductor substrate is made of nitride. 33. The method of manufacturing a semiconductor device according to claim 28, wherein the semiconductor substrate is made of carbide or boride.