JP2001160539A - Forming method for nitride semiconductor device and nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming device for a nitride semiconductor and a nitride semiconductor device, with which rearrangement can be reduced further, without using a selective growing mask. SOLUTION: On a side C of a sapphire substrate 1, an AlGaN first buffer layer 2, a GaN second buffer layer 3 and a first GaN layer 4 are grown sequentially, and the first GaN layer 4 on a line A-A in the figure is polished. Thus, a surface slanted by a prescribed angle B from the side C of the sapphire substrate 1 to a prescribed direction is exposed on the first GaN layer 4. Thus, a GaN off substrate 25 with an off surface formed on the first GaN layer 4 is produced, and a second GaN layer is grown on the off surface of the first GaN layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaN (gallium nitride), AlN (aluminum nitride), InN (indium nitride), BN (boron nitride) or T1N (thallium nitride) or a mixed crystal thereof such as III-V. Group III-V nitride semiconductors such as group nitride semiconductors (hereinafter referred to as nitride semiconductors) and mixed crystals containing at least one element of As, P and Sb in these mixed crystals The present invention relates to a nitride-based semiconductor device having the same and a method for forming a nitride-based semiconductor.

[0002]

2. Description of the Related Art At present, semiconductor devices utilizing GaN-based semiconductors, for example, semiconductor light-emitting devices such as light-emitting diode devices and electronic devices such as transistors have been actively developed. When manufacturing such a GaN-based semiconductor device, it is difficult to manufacture a substrate made of GaN.
A GaN-based semiconductor layer is epitaxially grown on a substrate made of sapphire, SiC, Si, or the like.

In this case, since a substrate such as sapphire and GaN have different lattice constants, dislocations (lattice defects) extending vertically from the substrate exist in the GaN-based semiconductor layer grown on the substrate such as sapphire. And the dislocation density is about 10 ⁹ cm ^-2 . Such dislocations in the GaN-based semiconductor layer cause deterioration of device characteristics and reliability of the semiconductor device.

As a method of reducing dislocations in the GaN-based semiconductor layer as described above, pages 53 to 58 and 210 of Journal of Applied Electronic Properties, Vol. 4 (1998).
Selective lateral growth (ELO: Epitaxial La
teral Overgrowth) is shown.

FIG. 13 is a schematic sectional view showing an example of a conventional method for forming a nitride semiconductor using selective lateral growth.

As shown in FIG. 13A, GaN having a thickness of about 1 μm is formed on a C (0001) plane of a sapphire substrate 201 by MOVPE (metal organic chemical vapor deposition).
A layer 202 is formed. Further, a plurality of stripe-shaped SiO ₂ films 21 are selectively formed on the GaN layer 202 as a selective growth mask.
0 is formed. Note that there are many dislocations propagating in the c-axis direction in the GaN layer 202.

[0007] As shown in FIG. 13 (b), SiO ₂ film 2
After the formation of 10, the regrown GaN layer 203 is grown by HVPE (halide vapor phase epitaxy). Where Si
Since GaN hardly grows on the O ₂ film 210,
The regrown GaN layer 203 at the initial stage of growth is made of striped Si
It is selectively grown on the GaN layer 202 exposed between the O ₂ films 210. In this case, on the GaN layer 202, the regrown GaN layer 203 grows in the direction of the arrow Y (c-axis direction) in the figure. In such growth, dislocations propagate from the GaN layer 202 in the c-axis direction.

As described above, the exposed GaN layer 20
2 on top of regrown GaN with triangular facet structure
The layer 203 is grown.

[0009] As shown in FIG.
As the growth of the regrown GaN layer 203 on the layer 202 progresses, the regrown GaN layer 203 further grows in the direction of arrow X (lateral direction) in the figure. By such lateral growth of the regrown GaN layer 203, the regrown GaN layer 203 is formed on the SiO ₂ film 210. In the growth on the C-plane of the surface of the regrown GaN layer 203, growth occurs in a step flow mode. For this reason, the regrown GaN layer 2
The dislocations propagated from the GaN layer 202 in the c-axis direction along with the lateral growth of the sapphire substrate 20
1 is bent in a direction parallel to the C plane.

As a result, in the regrown GaN layer 203, it is possible to reduce dislocations propagating in the c-axis direction.

As shown in FIG. 13D, when the regrown GaN layer 203 is further grown in the lateral direction, the regrown GaN layers 203 having the facet structure are united to form a continuous film. Thus, a flat regrown GaN layer 203 is formed. In this case, dislocations are reduced near the surface of the planarized regrown GaN layer 203.

As described above, in the above-described method for forming a nitride-based semiconductor, it is possible to reduce dislocations in the regrown GaN layer 203 by performing selective lateral growth of the regrown GaN layer 203. Become. By forming the nitride-based semiconductor layer on the regrown GaN layer 203 in which such dislocations are reduced, a nitride-based semiconductor layer having good crystallinity can be formed on the sapphire substrate 201.

[0013]

In the above-described method for forming a nitride-based semiconductor, a plurality of striped SiO ₂ films 210 are formed as selective growth masks in order to grow the regrown GaN layer 203 in the lateral direction.

Here, the thermal expansion coefficient differs between the SiO ₂ film 210 and GaN. Therefore, the regrown GaN layer 203
When a plurality of SiO ₂ films 210 are formed therein, the regrowth G
Cracks easily occur in the aN layer 203. In the case where an insulating film such as a TiO ₂ film or a thin film of a high melting point metal such as W is used as a selective growth mask instead of the SiO ₂ film 210, as in the case where the SiO ₂ film 210 is used, selective growth is performed. Cracks are likely to occur in the regrown GaN layer 203 due to the difference in thermal expansion coefficient between the mask and GaN.

In the above-described method for forming a nitride-based semiconductor, as shown in FIG. 12D, when the regrown GaN layers 203 having the facet structure grown laterally are united, the void 215 is formed at the united portion. May occur, and cracks may easily occur in the regrown GaN layer 203 due to such voids 215.

From the above, when a nitride-based semiconductor layer including an element region is formed on the regrown GaN layer 203 formed by the above-described method for forming a nitride-based semiconductor to manufacture a semiconductor element, Cracks are likely to occur in the separation step and the like. The occurrence of such cracks causes deterioration of device characteristics and reliability of the semiconductor device, as well as a reduction in yield.

In order to realize a semiconductor device having better device characteristics and higher reliability, it is desired to further reduce lattice defects in a nitride semiconductor.

An object of the present invention is to provide a method of forming a nitride-based semiconductor which can further reduce dislocations without using a selective growth mask.

It is another object of the present invention to provide a semiconductor device in which dislocations are reduced and cracks are prevented without using a selective growth mask.

[0020]

Means for Solving the Problems and Effects of the Invention (1)
First invention A method for forming a nitride-based semiconductor according to the first invention is to grow a first nitride-based semiconductor layer on a C-plane of a substrate, and to perform a predetermined process on the first nitride-based semiconductor layer from the C-plane A second nitride semiconductor layer closer to a single crystal than the first nitride semiconductor layer on the inclined surface of the first nitride semiconductor layer. It is to grow. Here, the second nitride-based semiconductor layer is substantially a single crystal.

In the method for forming a nitride-based semiconductor according to the first invention, a step of an atomic order is formed on the inclined surface of the first nitride-based semiconductor layer.

The first having such a step of the atomic order is
When the second nitride-based semiconductor layer is grown on the inclined surface of the nitride-based semiconductor layer, the growth mainly occurs in the step flow mode. For this reason, dislocations propagated in the vertical direction from the first nitride-based semiconductor layer bend in the horizontal direction with the step flow growth of the second nitride-based semiconductor layer. This makes it possible to reduce dislocations that propagate in the vertical direction in the second nitride-based semiconductor layer. Therefore, good crystallinity is realized on the surface of the second nitride-based semiconductor layer.

Further, according to the above-described method for forming a nitride-based semiconductor, the second nitride-based semiconductor layer can be grown in a step flow without using a selective growth mask.
Therefore, in the second nitride-based semiconductor layer, cracks due to a difference in thermal expansion coefficient between the selective growth mask and the nitride-based semiconductor are prevented, and voids are also prevented.

The surface of the first nitride-based semiconductor layer may be polished to expose a surface inclined at a predetermined angle from the C-plane in a predetermined direction. In this case, a small step-like step extending in a stripe shape in a predetermined direction is formed on the inclined surface of the first nitride-based semiconductor layer exposed by polishing.

In the process of growing the first nitride semiconductor layer on the substrate, a surface inclined at a predetermined angle from the C plane in a predetermined direction may be exposed. In this case, for example, by growing a first nitride-based semiconductor layer having a non-uniform film thickness, the surface inclined at a predetermined angle from the C-plane in a predetermined direction to the first is formed.
In the nitride-based semiconductor layer.
On the exposed surface of the first nitride-based semiconductor layer, a small step-like step extending in a stripe shape in a predetermined direction is formed.

(2) Second invention A method of forming a nitride semiconductor according to one aspect of the second invention is a method of forming a nitride semiconductor in which a nitride semiconductor layer is grown on a semiconductor substrate. The substrate is a semiconductor substrate made of a group IV semiconductor, a group IV-IV semiconductor, or a group II-VI semiconductor, in which an uneven pattern is formed on the surface of the semiconductor substrate, and a nitride-based semiconductor layer is grown on the uneven pattern. is there. Here, the nitride-based semiconductor layer is substantially a single crystal.

According to another aspect of the present invention, there is provided a method of forming a nitride-based semiconductor in which a nitride-based semiconductor layer is grown on a semiconductor substrate. Differs from lattice constant of nitride-based semiconductor layer
A semiconductor substrate made of a III-V semiconductor, in which an uneven pattern is formed on the surface of the semiconductor substrate, and a nitride-based semiconductor layer is grown on the uneven pattern. Here, the nitride-based semiconductor layer is substantially a single crystal.

A method for forming a nitride semiconductor according to still another aspect of the second invention is a method for forming a nitride semiconductor in which a nitride semiconductor layer is grown on an insulator substrate. And a nitride semiconductor layer is grown on the uneven pattern. Here, the nitride-based semiconductor layer is substantially a single crystal.

A method for forming a nitride-based semiconductor according to still another aspect of the second invention includes forming an uneven pattern on a surface of a substrate, growing a buffer layer on the uneven pattern, Then, a nitride-based semiconductor layer is grown until the surface becomes substantially flat. here,
The nitride-based semiconductor layer is substantially single crystal, and the buffer layer is non-single crystal.

In the method for forming a nitride-based semiconductor according to the second aspect of the invention, a step of the nitride-based semiconductor layer is formed near the step of the substrate at the initial stage of growth, originating from the step of the substrate.

As the growth of the nitride-based semiconductor layer further proceeds,
The lateral growth in the nitride-based semiconductor layer on the step side surface becomes dominant. Thereby, the recesses are gradually filled in the nitride-based semiconductor layer, and a nitride-based semiconductor layer having a flat surface is formed. In the lateral growth of such a nitride-based semiconductor layer, generation of voids can be suppressed.

Here, since the nitride-based semiconductor layer grows in the lateral direction as described above, dislocations generated in the vicinity of the substrate and propagated in the vertical direction are generated in the lateral direction with the lateral growth of the nitride-based semiconductor layer. Bends. This makes it possible to reduce dislocations that propagate in the vertical direction in the nitride-based semiconductor layer. Therefore, good crystallinity is realized on the surface of the nitride-based semiconductor layer.

According to the method for forming a nitride-based semiconductor, the nitride-based semiconductor layer can be grown laterally without using a selective growth mask. For this reason, in the nitride-based semiconductor layer, generation of cracks due to a difference in thermal expansion coefficient between the selective growth mask and the nitride-based semiconductor is prevented. In some cases, it is also possible to prevent the occurrence of voids.

Further, according to the above-described method for forming a nitride-based semiconductor, a nitride-based semiconductor layer having reduced dislocations can be easily formed by a single growth of the nitride-based semiconductor.

In particular, when a substrate whose surface can be easily processed is used in the above-described method for forming a nitride-based semiconductor,
Since the concavo-convex pattern can be easily formed on the surface of the substrate, a nitride-based semiconductor layer with reduced dislocations can be formed more easily.

The concavo-convex pattern may have concave portions and convex portions extending in a stripe shape. In this case, lateral growth can be performed on the nitride-based semiconductor layer on the concave portion formed in the substrate.

Further, the concave / convex pattern may have a plurality of concave portions or convex portions which are two-dimensionally dispersed. When a plurality of concave portions are dispersedly arranged on the surface of the substrate, lateral growth can be performed on the nitride-based semiconductor layer on the concave portions of the substrate. On the other hand, when a plurality of protrusions are dispersedly arranged on the surface of the substrate, lateral growth can be performed on the nitride-based semiconductor layer in a region between the protrusions of the substrate.

Further, the uneven pattern may have a step-like step. In this case, the nitride-based semiconductor layer can be laterally grown by utilizing the step-like steps formed on the substrate.

(3) Third invention A method for forming a nitride semiconductor according to one aspect of the third invention is a method for forming a nitride semiconductor in which a nitride semiconductor layer is grown on a semiconductor substrate. The substrate is a semiconductor substrate made of a group IV semiconductor, a group IV-IV semiconductor, or a group II-VI semiconductor. A plurality of buffer layers having a width Y are dispersedly formed at intervals X on the semiconductor substrate by etching. When X [μm] and width Y [μm] are Y [μm] ≦ −X [μ
m] +40 [μm] and Y [μm] ≧ 1 [μm] and X
This satisfies the relationship [μm] ≧ 1 [μm] and grows a nitride-based semiconductor layer on a semiconductor substrate and a plurality of buffer layers. Here, the nitride-based semiconductor layer is substantially a single crystal.

A method for forming a nitride-based semiconductor according to another aspect of the third invention is a method for forming a nitride-based semiconductor in which a nitride-based semiconductor layer is grown on a semiconductor substrate. Differs from lattice constant of nitride-based semiconductor layer
A semiconductor substrate made of a III-V semiconductor. A plurality of buffer layers having a width Y are formed on the semiconductor substrate in a distributed manner at an interval X by etching, and an interval X [μm] and a width Y [μ
m] is Y [μm] ≦ −X [μm] +40 [μm] and Y
This satisfies the relationship of [μm] ≧ 1 [μm] and X [μm] ≧ 1 [μm], and grows a nitride-based semiconductor layer on a semiconductor substrate and a plurality of buffer layers. Here, the nitride-based semiconductor layer is substantially a single crystal.

A method for forming a nitride-based semiconductor according to still another aspect of the third invention is a method for forming a nitride-based semiconductor in which a nitride-based semiconductor layer is grown on an insulator substrate. A plurality of buffer layers having a width Y are dispersedly formed at an interval X by etching, and an interval X [μm] and a width Y are formed.
[Μm] is Y [μm] ≦ −X [μm] +40 [μm] and Y [μm] ≧ 1 [μm] and X [μm] ≧ 1 [μm]
Is satisfied, and a nitride-based semiconductor layer is grown on the insulator substrate and the plurality of buffer layers. Here, the nitride-based semiconductor layer is substantially a single crystal.

In the method for forming a nitride-based semiconductor according to the third aspect of the invention, since the substrate and the nitride-based semiconductor have different lattice constants, the nitride-based semiconductor layer is grown on the substrate without a buffer layer. It is difficult. For this reason,
The nitride-based semiconductor layer is selectively grown on the plurality of buffer layers at an early stage of growth. In this case, the nitride-based semiconductor layer grows vertically on the buffer layer.

As the growth of the nitride-based semiconductor layer in the vertical direction proceeds, the nitride-based semiconductor layer grown on the buffer layer further grows in the horizontal direction. Thereby, a nitride-based semiconductor layer is formed on the substrate exposed between the plurality of buffer layers. By such lateral growth of the nitride-based semiconductor layer,
A continuous film nitride-based semiconductor layer having a flat surface is formed. In the lateral growth of such a nitride-based semiconductor layer, generation of voids can be suppressed.

Here, since the nitride-based semiconductor layer grows in the lateral direction as described above, dislocations generated in the vicinity of the substrate and propagated in the vertical direction are generated in the lateral direction with the lateral growth of the nitride-based semiconductor layer. Bends. This makes it possible to reduce dislocations that propagate in the vertical direction in the nitride-based semiconductor layer. Therefore, good crystallinity is realized on the surface of the nitride-based semiconductor layer.

Further, according to the method for forming a nitride-based semiconductor, the nitride-based semiconductor layer can be grown laterally without using a selective growth mask. For this reason, in the nitride-based semiconductor layer, generation of cracks due to a difference in thermal expansion coefficient between the selective growth mask and the nitride-based semiconductor is prevented. In some cases, it is also possible to prevent the occurrence of voids.

Further, according to the above-described method for forming a nitride-based semiconductor, a nitride-based semiconductor layer having reduced dislocations can be easily formed by a single growth of the nitride-based semiconductor.

Since the non-single-crystal buffer layer is easy to process, a plurality of buffer layers can be easily formed in the above-described method for forming a nitride-based semiconductor. Therefore, a nitride-based semiconductor layer with reduced dislocations can be formed more easily.

Further, in this case, since the interval X and the width Y of the buffer layer satisfy the above relationship, the buffer layer can be easily patterned by etching, and the nitride-based semiconductor formed on the buffer layer can be formed. The layer can be easily flattened. Therefore, in this case, a nitride-based semiconductor layer can be easily formed.

The plurality of buffer layers may be arranged in a stripe. In this case, lateral growth can be performed on the nitride-based semiconductor layer on the substrate exposed between the plurality of striped buffer layers.

The plurality of buffer layers may be two-dimensionally distributed. In this case, lateral growth can be performed on the nitride-based semiconductor layer on the substrate exposed between the two-dimensionally dispersed buffer layers.

(4) Fourth Invention In a nitride semiconductor device according to a fourth invention, a first nitride semiconductor layer is formed on a C-plane of a substrate, and the first nitride semiconductor layer On a plane inclined at a predetermined angle in a predetermined direction from the C plane, a second crystal closer to a single crystal than the first nitride-based semiconductor layer is formed.
Is formed, and a nitride-based semiconductor layer including an element region is formed on the second nitride-based semiconductor layer. Here, the second nitride-based semiconductor layer is substantially single crystal, and the nitride-based semiconductor layer including the element region is substantially single crystal.

The inclined surface of the first nitride semiconductor layer of the nitride semiconductor device according to the fourth invention has a step in the atomic order. The first having such a step of the atomic order
When the second nitride-based semiconductor layer is grown on the inclined surface of the nitride-based semiconductor layer, the growth mainly occurs in the step flow mode. For this reason, the dislocation propagated in the vertical direction from the substrate is bent in the horizontal direction with the step flow growth of the second nitride-based semiconductor layer. Thereby, in the second nitride-based semiconductor layer, dislocations that propagate in the vertical direction are reduced. Therefore, good crystallinity is realized on the surface of the second nitride-based semiconductor layer.

In the above-described nitride-based semiconductor device, a nitride-based semiconductor layer including a device region is formed on the second nitride-based semiconductor layer in which dislocations are reduced as described above. Therefore, good crystallinity is realized in the nitride-based semiconductor layer. Thereby, in the nitride-based semiconductor device, device characteristics and reliability are improved.

In the second nitride-based semiconductor layer of the above-described nitride-based semiconductor device, step flow growth is performed without using a selective growth mask. The generation of cracks due to the difference in expansion coefficient is prevented, and the generation of voids is also prevented. As a result, in the nitride-based semiconductor device described above, cracks are prevented from occurring in the device isolation step or the like during manufacturing, and a high yield is realized.

(5) Fifth Invention A nitride semiconductor device according to one aspect of the fifth invention is a nitride semiconductor device in which a nitride semiconductor layer is formed on a semiconductor substrate. A semiconductor substrate made of a group IV semiconductor, a group of IV-IV semiconductors or a group of II-IV semiconductors, an uneven pattern is formed on the surface of the semiconductor substrate, and a nitride-based semiconductor layer including an element region is formed on the uneven pattern. Things. Here, the nitride-based semiconductor layer is substantially a single crystal.

A nitride-based semiconductor device according to another aspect of the fifth invention is a nitride-based semiconductor device in which a nitride-based semiconductor layer is formed on a semiconductor substrate. A semiconductor substrate made of a group III-V semiconductor having a lattice constant different from the lattice constant of the semiconductor layer. An uneven pattern is formed on the surface of the semiconductor substrate, and a nitride-based semiconductor layer including an element region is formed on the uneven pattern. . here,
The nitride-based semiconductor layer is substantially single crystal.

A nitride semiconductor device according to still another aspect of the fifth invention is a nitride semiconductor device in which a nitride semiconductor layer is formed on an insulator substrate. Is formed, and a nitride-based semiconductor layer including an element region is formed on the concave / convex pattern. Here, the nitride-based semiconductor layer is substantially a single crystal.

In a nitride semiconductor device according to still another aspect of the fifth invention, an uneven pattern is formed on the surface of the substrate, a buffer layer is formed on the uneven pattern, and at least the buffer layer is formed on the uneven pattern and the buffer layer. Forming a first nitride-based semiconductor layer having a partially substantially flat surface;
A second nitride semiconductor layer including an element region is formed on a flat surface of a first nitride semiconductor layer. Here, the first nitride-based semiconductor layer and the second nitride-based semiconductor layer are substantially single-crystal, and the buffer layer is non-single-crystal.

In the nitride-based semiconductor device according to the fifth aspect of the present invention, in the initial stage of growth, a step of the nitride-based semiconductor layer is formed near the step of the substrate due to the step of the substrate.

As the growth of the nitride-based semiconductor layer further proceeds,
The lateral growth in the nitride-based semiconductor layer on the step side surface becomes dominant. Thereby, the recesses are gradually filled in the nitride-based semiconductor layer, and a nitride-based semiconductor layer having a flat surface is formed.

Here, since the nitride-based semiconductor layer grows in the lateral direction as described above, dislocations generated in the vicinity of the substrate and propagated in the vertical direction are generated in the lateral direction with the lateral growth of the nitride-based semiconductor layer. Bends. Thereby, in the nitride semiconductor layer, dislocations propagating in the vertical direction are reduced. Therefore, good crystallinity is realized on the surface of the nitride-based semiconductor layer.

In the above-described nitride-based semiconductor device, a nitride-based semiconductor layer including a device region is formed on the nitride-based semiconductor layer with reduced dislocation. Therefore, good crystallinity is realized in the nitride-based semiconductor layer. Thereby, in the nitride-based semiconductor device, device characteristics and reliability are improved.

In the nitride-based semiconductor layer of the above-described nitride-based semiconductor device, since the lateral growth is performed without using a selective growth mask, the coefficient of thermal expansion between the selective growth mask and the nitride-based semiconductor is reduced. The occurrence of cracks due to the difference is prevented. In some cases, the generation of voids can be prevented. As a result, in the nitride-based semiconductor device described above, cracks are prevented from occurring in the device isolation step or the like during manufacturing, and a high yield is realized.

Further, in the above-mentioned nitride-based semiconductor device, a nitride-based semiconductor layer having reduced dislocations can be easily formed by one growth of the nitride-based semiconductor. Therefore, such a nitride-based semiconductor device is easy to manufacture.

In particular, when a substrate whose surface can be easily processed is used, a nitride-based semiconductor device can be manufactured more easily because an uneven pattern is easily formed on the surface of the substrate.

Preferably, a second nitride-based semiconductor layer including an element region is formed in a region other than the center of the concave portion of the concave-convex pattern. In this case, better crystallinity can be realized in the second nitride-based semiconductor layer including the element region. Thereby, in the nitride-based semiconductor device, the device characteristics and the reliability are further improved.

(6) Sixth Invention A nitride semiconductor device according to one aspect of the sixth invention is a nitride semiconductor device in which a nitride semiconductor layer is formed on a semiconductor substrate. A semiconductor substrate made of a group IV semiconductor, a group IV-IV semiconductor or a group II-VI semiconductor, on which a plurality of buffer layers having a width Y are formed dispersively at an interval X, and an interval X [μm] and a width Y [μm]
Is Y [μm] ≦ −X [μm] +40 [μm] and Y [μm]
m] ≧ 1 [μm] and X [μm] ≧ 1 [μm], and a nitride-based semiconductor layer is formed on a semiconductor substrate and a plurality of buffer layers. Here, the nitride-based semiconductor layer is substantially a single crystal.

A nitride-based semiconductor device according to another aspect of the sixth invention is a nitride-based semiconductor device in which a nitride-based semiconductor layer is formed on a semiconductor substrate. A semiconductor substrate made of a III-V group semiconductor having a lattice constant different from that of the semiconductor layer.
, A buffer layer having a width Y is formed in a dispersed manner, and an interval X [μ
m] and width Y [μm] are Y [μm] ≦ −X [μm] +
40 [μm] and Y [μm] ≧ 1 [μm] and X [μm]
m] ≧ 1 [μm], and a nitride-based semiconductor layer is formed on a semiconductor substrate and a plurality of buffer layers. Here, the nitride-based semiconductor layer is substantially a single crystal.

A nitride semiconductor device according to still another aspect of the sixth invention is a nitride semiconductor device in which a nitride semiconductor layer is formed on an insulator substrate. A buffer layer having a width Y is formed in a dispersed manner,
[Μm] and width Y [μm] are Y [μm] ≦ −X [μ
m] +40 [μm] and Y [μm] ≧ 1 [μm] and X
This satisfies the relationship of [μm] ≧ 1 [μm], and a nitride-based semiconductor layer is formed on an insulating substrate and a plurality of buffer layers. Here, the nitride-based semiconductor layer is substantially a single crystal.

In the nitride semiconductor device according to the sixth aspect, a plurality of buffer layers are dispersed on the substrate. Here, since the lattice constant is different between the substrate and the nitride semiconductor, it is difficult to grow the nitride semiconductor on the substrate exposed between the buffer layers. For this reason, the nitride-based semiconductor layer in the initial stage of growth selectively grows on the plurality of buffer layers. In this case, the nitride-based semiconductor layer grows vertically on the buffer layer.

As the growth of the nitride semiconductor layer in the vertical direction proceeds, the nitride semiconductor layer grown on the buffer layer becomes
Further grow laterally. Thereby, a nitride-based semiconductor layer is formed on the substrate exposed between the buffer layers. In this way, a continuous nitride semiconductor layer having a flat surface is formed. In the lateral growth of such a nitride-based semiconductor layer, generation of voids can be suppressed.

Here, since the nitride-based semiconductor layer grows in the lateral direction as described above, dislocations generated in the vicinity of the substrate and propagated in the vertical direction are generated in the lateral direction with the lateral growth of the nitride-based semiconductor layer. Bends. Thereby, in the nitride-based semiconductor layer, dislocations propagating in the vertical direction are reduced. Therefore, good crystallinity is realized on the surface of the nitride-based semiconductor layer.

In the nitride-based semiconductor device described above, a nitride-based semiconductor layer including a device region is formed on the nitride-based semiconductor layer having reduced dislocations. Therefore, good crystallinity is realized in the nitride-based semiconductor layer. Thereby, in the nitride-based semiconductor device, device characteristics and reliability are improved.

In the nitride-based semiconductor layer of the above-described nitride-based semiconductor device, since the lateral growth is performed without using a selective growth mask, the coefficient of thermal expansion between the selective growth mask and the nitride-based semiconductor is reduced. The occurrence of cracks due to the difference is prevented. In some cases, it is also possible to prevent the occurrence of voids.

As a result, in the above-mentioned nitride-based semiconductor device, the occurrence of cracks in the device isolation step or the like during manufacturing is prevented, and a high yield is realized.

Further, in the above-mentioned nitride-based semiconductor device, a nitride-based semiconductor layer having reduced dislocations can be easily formed by one growth of the nitride-based semiconductor. In addition, a plurality of buffer layers are easily formed because a buffer layer grown at a low temperature and having poor crystallinity is easily processed. Therefore, such a nitride-based semiconductor device is easy to manufacture.

In this case, since the interval X and the width Y of the buffer layer satisfy the above relationship, the etching can be easily performed at the time of patterning the buffer layer, and the buffer layer is formed on the buffer layer. It is possible to easily planarize the nitride-based semiconductor layer. Therefore, such a nitride-based semiconductor device is easy to manufacture.

[0078]

1 and 2 are schematic sectional views showing a method for forming a nitride semiconductor according to an embodiment of the first invention.

As shown in FIG.
The sapphire substrate 1 having a diameter of 50.8 mm was formed by MOVPE (metal organic chemical vapor deposition) while maintaining the temperature at 0 ° C.
A film thickness of about 1 made of undoped AlGaN
An AlGaN first buffer layer 2 of 5 nm is formed. Further, a film thickness of about 0.5 μm of undoped GaN is formed by MOVPE while maintaining the substrate temperature at 1150 ° C.
GaN second buffer layer 3 is formed.

Subsequently, as shown in FIG. 1B, the first GaN layer of undoped GaN having a thickness of about 600 μm was formed by HVPE (halide vapor phase epitaxy) while maintaining the substrate temperature at 1150 ° C. 4 is formed. At the time of forming the first GaN layer 4, undoped GaN is grown while rotating the sapphire substrate 1. Thereby, it is possible to form the first GaN layer 4 having a uniform film thickness over the whole.

After the first GaN layer 4 is grown as described above, the first GaN layer 4 on the line AA in the figure is polished and removed. As a result, in the first GaN layer 4, a surface (hereinafter, referred to as an off-plane) inclined by a predetermined angle (hereinafter, referred to as an off-angle) B from a C plane of the sapphire substrate 1 in a predetermined direction (hereinafter, referred to as an off-direction). Expose).

As described above, as shown in FIG. 1C, a GaN off-substrate 25 in which the first GaN layer 4 has an off-surface is manufactured. In this case, a step in the atomic order is formed on the surface of the GaN off substrate 25, that is, the off surface of the first GaN layer 4. 1 (c) and FIG.
(D) and (e) are schematic diagrams in which the steps in the atomic order are exaggerated in the height direction. In addition, the GaN second buffer layer 3
Generated in the vicinity of the sapphire substrate 1 in Ga
It propagates through the N second buffer layer 3 and the first GaN layer 4 in the c-axis direction.

Subsequently, as shown in FIGS. 2D to 2E, the undoped Ga is deposited on the off surface of the first GaN layer 4 by MOVPE while keeping the substrate temperature at 1150 ° C.
A second GaN layer 5 made of N is grown. In this case, growth mainly occurs in the step flow mode. Therefore, dislocations propagated from the sapphire substrate 1 in the c-axis direction are:
With the step flow growth of the second GaN layer 5, the lateral direction (the direction of arrow X), that is, (000) of the second GaN layer 5
1) It bends in a direction parallel to the plane. Thereby, the second G
In the aN layer 5, dislocations propagating in the c-axis direction are reduced.

The thus formed second GaN layer 5
On the surface of, dislocations are reduced and good crystallinity is obtained.

According to the method of forming a nitride semiconductor as described above, the step of atomic order on the off surface of the first GaN layer 4 is utilized to form the second GaN without using a selective growth mask such as a SiO ₂ film. The layer 5 can be grown laterally to reduce dislocations. Therefore, the second GaN layer 5 having good crystallinity can be formed on the GaN off substrate 25.

In the above-described method for forming a nitride-based semiconductor, since a selective growth mask is not used, the occurrence of cracks due to a difference in thermal expansion coefficient between the selective growth mask and GaN can be prevented. Further, generation of voids in the second GaN layer 5 can be prevented.

As described above, when a nitride-based semiconductor layer including an element region is formed on the second GaN layer 5 to manufacture a semiconductor device, the nitride-based semiconductor layer formed on the second GaN layer 5 has a good quality. Crystallinity can be obtained, and generation of cracks in the element separation step and the like can be prevented. Thereby, a semiconductor device having good device characteristics and high reliability can be obtained.

In the above-described method for forming a nitride-based semiconductor, the off-angle B of the off-plane of the first GaN layer 4 is not particularly limited.

Here, for example, the off angle B of the off plane of the first GaN layer 4 is set to 0.02 °, 0.05 °, 0.1 °,
When the crystallinity of each of the second GaN layers 5 at 0.2 °, 0.5 °, 1 °, 2 °, and 5 ° is evaluated based on the half width of the X-ray diffraction rocking curve, etc., the first GaN layer 4 The result shows that the larger the off-angle B of the off-plane, the better the crystallinity of the second GaN layer 5 formed on the off-plane.

Further, the inclination direction of the off surface of the first GaN layer 4, that is, the off direction is not particularly limited.

Here, for example, the off direction of the first GaN layer 4 is changed from the [1-100] direction and the [1-100] direction to [1-21].
0] direction, 10 ° from [1-210] direction to [1-100] direction, and [1-2].
10], the crystallinity of each second GaN layer 5 is evaluated by the same method as described above.
The result shows that the closer the off direction of the layer 4 is to the [1-100] direction, the more the crystallinity of the second GaN layer 5 formed on the off plane is improved.

In the above, the first GaN layer 4 having a uniform thickness is rotated by rotating the substrate during the growth of the first GaN layer 4.
After forming the first GaN layer 4, the first GaN layer 4 is polished to form an off surface, but the first GaN layer 4 is grown without rotating the substrate during growth to form the first GaN layer 4 having a non-uniform film thickness. However, the surface of the first GaN layer 4 having a non-uniform film thickness may be used as the off surface.

In the first GaN layer 4 thus formed, the thickness of the thickest portion is, for example, about 700 μm, and the thickness of the thinnest portion is, for example, about 500 μm. Therefore, the surface of such a first GaN layer 4 is:
The first GaN layer 4 is inclined about 0.2 ° with respect to the (0001) plane on average. Thereby, an off surface can be formed in the first GaN layer 4 without polishing the surface.

Since the substrate can be rotated on the first GaN layer 4 to form a nitride-based semiconductor layer having a uniform thickness, the nitride-based semiconductor layer can be formed once without interrupting the growth. By growing the layer, a nitride-based semiconductor layer with reduced dislocations can be easily formed.

Further, in the above, the sapphire substrate 1
However, an insulating substrate such as spinel may be used. Alternatively, a group IV semiconductor such as Si, Ge, etc .;
A semiconductor substrate made of a group IV-IV semiconductor or a group II-VI semiconductor such as ZnSe, or GaAs, InP, Ga having a lattice constant of the semiconductor substrate different from that of the nitride-based semiconductor layer.
A semiconductor substrate made of a group III-V semiconductor such as P may be used. Any of an insulating substrate, an n-type substrate, and a p-type substrate may be used as the semiconductor substrate. When a substrate having a lattice constant different from the lattice constant of the nitride-based semiconductor layer is used as described above, a large number of dislocations are generated in the nitride-based semiconductor layer near the substrate, and the present invention reduces this dislocation. The effect is great.

Further, conventional selective lateral growth using a selective growth mask may be applied to the above-described method of forming a nitride-based semiconductor layer. This case will be described below.

FIG. 3 is a schematic process sectional view showing a method of forming a nitride semiconductor according to another embodiment of the first invention.

In this case, as shown in FIG.
A 15 nm-thick film is formed on the C-plane of the sapphire substrate 1 by the same method as the method for forming the nitride-based semiconductor shown in FIG.
AlGaN first buffer layer 2 and 0.5 μm-thick GaN second buffer layer 3 are sequentially grown.

After that, in a predetermined region on the GaN second buffer layer 3, a film thickness of about 0.1 mm extending in the [11-20] direction of GaN.
A 5 μm-stripe SiO ₂ film 15 is formed as a selective growth mask. The interval between the SiO ₂ films 15 in this case may be larger than the interval between the SiO ₂ films 210 in the conventional selective lateral growth shown in FIG. Therefore, the number of SiO ₂ films 15 formed on the GaN second buffer layer 3 may be smaller than the number of SiO ₂ films 210 in the conventional selective lateral growth.

Subsequently, as shown in FIG. 3B, while rotating the sapphire substrate 1 while keeping the substrate temperature at 1150 ° C., the GaN second buffer layer 3 and the SiO ₂ film 15 were formed by HVPE. A first GaN layer 4 made of undoped GaN is grown thereon.

Here, on the SiO ₂ film 15, Ga
Since the N is difficult to grow, the first GaN layer 4a
Selectively grows on the GaN second buffer layer 3 exposed between the SiO ₂ films. At this time, the first GaN layer 4a
It grows in the direction of arrow Y (c-axis direction) in the figure. In such growth of the first GaN layer 4a, dislocations propagate from the second GaN buffer layer 3 in the c-axis direction.

As the growth of the first GaN layer 4a on the GaN second buffer layer 3 proceeds, the first GaN layer 4a formed on the GaN second buffer layer 3 further moves in the direction of arrow X (lateral direction). grow up. Thereby, Si
The first GaN layer 4a is formed on the O ₂ film 15.

Here, the first G on the SiO ₂ film 15
Since the aN layer 4a grows in the lateral direction, the sapphire substrate 1
The dislocation that propagates in the c-axis direction generated in the vicinity is the first GaN
As the layer 4a grows in the lateral direction, it is bent in the lateral direction (the direction of arrow X), that is, in a direction parallel to the (0001) plane of the first GaN layer 4a. Thereby, in the first GaN layer 4a, the dislocation propagating in the c-axis direction is reduced.

Further, as shown in FIG. 3 (c), a first GaN layer 4a is grown until the first
The first GaN layer 4a is formed. Then, by the same method as the method of forming the nitride-based semiconductor layer in FIGS. 1 and 2,
The first GaN layer 4a on the line AA in the figure is polished and removed.

As described above, as shown in FIG. 3D, the GaN off substrate 2 having the off surface having the predetermined off angle B in the predetermined off direction formed on the first GaN layer 4a.
6 is produced.

In the GaN off substrate 26, the first GaN layer 4a is formed by selective lateral growth. Therefore, the first GaN layer 4a of the GaN off substrate 26
In the GaN off-substrate 25, dislocations are reduced as compared with the first GaN layer 4 of the GaN off substrate 25, and the crystallinity is improved.

On the off surface of the first GaN layer 4a, Ga
The second GaN layer 5a made of undoped GaN is grown by the same method as in the case of the N-off substrate 25. In this case, through the same process as the growth process of the second GaN layer 5 on the first GaN layer 4 of the GaN off substrate 25, the first G
The second GaN layer 5a is formed on the aN layer 4a. On the surface of the second GaN layer 5a thus formed, dislocations are further reduced, and good crystallinity is obtained.

According to the method for forming a nitride-based semiconductor as described above, the step of atomic order on the off surface of the GaN off-substrate 26 is utilized so that the second GaN layer 5a can be oriented in the lateral direction without using a selective growth mask. It becomes possible to grow and reduce dislocations. Therefore, the GaN off substrate 26
A second GaN layer 5a having better crystallinity can be formed thereon.

Further, the second GaN thus formed
In the layer 5a, generation of cracks due to a difference in thermal expansion coefficient between the selective growth mask and GaN is prevented,
Void formation is prevented.

Here, in the GaN off substrate 26,
The dislocation of the first GaN layer 4a is reduced by the selective lateral growth using the SiO ₂ film 15 as described above. For this reason, the second G layer formed on the first GaN layer 4a
In the aN layer 5a, the first Ga
As compared with the second GaN layer 5 formed on the N layer 4, dislocations are further reduced, and better crystallinity is realized.

In the above-described method for forming a nitride-based semiconductor, the second GaN layer is formed by two steps of selective lateral growth of the first GaN layer 4a using the SiO ₂ film 15 and formation of the off plane in the first GaN layer 4a. 5a, the dislocation is reduced. Therefore, in the above-described method for forming a nitride-based semiconductor, the effect of reducing dislocations due to the selective lateral growth of the first GaN layer 4a may be small. Therefore, as described above, in this example, the number of SiO ₂ films 15 can be made smaller than the number of SiO ₂ films formed during the conventional selective lateral growth. Thereby, the first GaN
In the layer 4a, it is possible to prevent the occurrence of cracks due to the difference in thermal expansion coefficient between the SiO ₂ film 15 and GaN,
The generation of voids on the iO ₂ film 15 can be prevented.

As described above, when a semiconductor device is manufactured by forming a nitride-based semiconductor layer including an element region on the second GaN layer 5a, the nitride-based semiconductor layer formed on the second GaN layer 5a is more favorable. In addition to obtaining excellent crystallinity, it is possible to prevent the occurrence of cracks in the element separation step and the like. Thereby, a semiconductor device having better device characteristics and higher reliability can be obtained.

Although the SiO ₂ film 15 is used as a selective growth mask in the above description, an insulating film such as a TiO ₂ film or a thin film made of a high melting point metal such as W may be used as a selective growth mask. .

In the above, the GaN off substrate 2
Although a substrate with reduced dislocations by selective growth was used as 6, a bulk GaN substrate with few dislocations was used as an off-substrate by polishing or the like, and this was used as a substrate.
The crystallinity can be further improved.

In addition, in the first invention, the substrate such as sapphire on the back surface of the off-substrate of the nitride semiconductor may be removed before forming the nitride-based semiconductor on the off-substrate. The effect of is obtained.

FIGS. 4 and 5 are schematic process sectional views showing a method of forming a nitride-based semiconductor according to one embodiment of the second invention.

First, as shown in FIG. 4A, a predetermined region of the sapphire substrate 11 having the C surface as a substrate surface is subjected to RIE.
Etching (reactive ion etching method) or the like. Thus, the sapphire substrate 11 on which the plurality of stripe-shaped concave portions extending in the predetermined direction are formed is manufactured.

In this case, the width w of the concave portion is several μm to several tens μm.
m, and the width b of the projection is several hundred nm to several tens μm.
m, and the depth d of the concave portion is several nm to several μm.
m is preferable. For example, in this example, the width w of the concave portion is about 29 μm, the width b of the convex portion is 2 μm, and the depth d of the concave portion is about 1 μm.

The angle of the side surface of the recess with respect to the C plane of the sapphire substrate 11 is not particularly limited. For example, in this example, the side surface of the concave portion is the C of the sapphire substrate 11.
It is almost perpendicular to the plane.

Further, the direction in which the stripe-shaped concave portions are formed is not particularly limited. For example, in this example, a stripe-shaped concave portion is formed in the [1-100] direction. In addition, a stripe-shaped recess may be formed in the [11-20] direction, for example.

Subsequently, as shown in FIG. 4B, the undoped AlGaN is formed on the upper surface of the sapphire substrate 11, the lower surface of the concave portion, and the side surface of the concave portion by MOVPE while maintaining the substrate temperature at 600 ° C. An AlGaN buffer layer 12 having a thickness of about 15 nm is grown. In this case, A
The lGaN buffer layer 12 is formed on the upper surface of the convex portion, the lower surface of the concave portion, and the side surface of the concave portion of the sapphire substrate 11 by arrows Y in FIG.
(C-axis direction) and the direction of arrow X (lateral direction). On the surface of the AlGaN buffer layer 12 thus formed, a concavo-convex pattern similar to that of the sapphire substrate 11 is formed.

Subsequently, as shown in FIG. 5C, while the substrate temperature was kept at 1150.degree.
A GaN layer 13 made of undoped GaN is grown on the lGaN buffer layer 12. In this case, the GaN layer 13 in the initial stage of growth grows in the direction of arrow Y (c-axis direction) on the convex top surface, concave bottom surface and concave side surface of the AlGaN buffer layer 12, and then in the direction of arrow X (horizontal direction). Direction) also grows. Such a GaN layer 13 in the initial stage of growth
A surface pattern similar to that of the AlGaN buffer layer 12 is formed on the surface of the substrate.

As shown in FIG. 5D, as the growth of the GaN layer 13 in the direction of arrow Y progresses, the growth of the GaN layer 13 in the direction of arrow X becomes dominant. In this case, on the GaN layer 13 on the bottom surface of the concave portion, the GaN layer 13 on the upper surface of the convex portion and the side surface of the concave portion further grows in the lateral direction.
Thereby, the concave portions of the GaN layer 13 are gradually filled.

Here, since the GaN layer 13 grows in the lateral direction as described above, dislocations generated in the vicinity of the sapphire substrate 11 and propagated in the c-axis direction are caused by the lateral growth of the GaN layer 13. (In the direction of arrow X), that is, the sapphire substrate 11 is bent in a direction parallel to the C plane. Thereby, in the GaN layer 13, dislocations propagating in the c-axis direction are uniformly reduced. Further, a region where the dislocation density is particularly reduced is formed on the concave portion excluding the central portion. In this case, in the central region of the GaN layer 13 formed on the concave portion of the sapphire substrate 11, a portion where dislocations are concentrated occurs linearly, and a region having a relatively high dislocation density is formed. .

As shown in FIG. 5E, the GaN layer 13 is grown until the GaN layer 13 is flattened, and the GaN layer 13 having a thickness of 10 μm is formed.
To form Dislocations are reduced on the surface of the GaN layer 13 thus formed, and good crystallinity is obtained. Further, voids are unlikely to be generated in such a GaN layer 13.

According to the method for forming a nitride-based semiconductor as described above, the GaN layer 13 is laterally grown without using a selective growth mask by using the sapphire substrate 11 in which the stripe-shaped concave portions are formed. Dislocations can be reduced. Therefore, the GaN layer 13 having good crystallinity can be formed.

In this case, the step of growing GaN involves G
This is only once when the aN layer 13 is formed. As described above, according to the above-described method for forming a nitride-based semiconductor, the GaN layer 13 with reduced dislocations can be easily obtained by a single GaN growth.

In the above-described method for forming a nitride-based semiconductor, since a selective growth mask is not used, it is possible to prevent cracks in the GaN layer 13 due to a difference in thermal expansion coefficient between the selective growth mask and GaN. Further, generation of voids in the GaN layer 13 can be prevented. Note that voids may remain.

As described above, when a nitride-based semiconductor layer including an element region is formed on the GaN layer 13 to manufacture a semiconductor device, the nitride-based semiconductor layer formed on the GaN layer 13 has good crystallinity. Can be obtained, and the occurrence of cracks in the element separation step or the like can be prevented. Thereby, a semiconductor device having good device characteristics and high reliability can be obtained.

As described above, the dislocation of the GaN layer 13 is uniformly reduced, but a region having a relatively high dislocation density is formed in the central region of the GaN layer 13 on the concave portion of the sapphire substrate 11. Is done. For this reason, when manufacturing a semiconductor element, it is preferable to form an element region in a region excluding a central portion on a concave portion of the sapphire substrate 11. Further, since a region having a particularly reduced dislocation density is formed on the concave portion except for the central portion, it is more preferable to form the element region in a region on the concave portion except for the central portion on the concave portion of the sapphire substrate 11.

In the above, the sapphire substrate 11
However, an insulating substrate such as spinel may be used. Alternatively, a group IV semiconductor such as Si, Ge, etc .;
A semiconductor substrate made of a group IV-IV semiconductor or a group II-VI semiconductor such as ZnSe, or GaAs, InP, Ga having a lattice constant of the semiconductor substrate different from that of the nitride-based semiconductor layer.
A semiconductor substrate made of a group III-V semiconductor such as P may be used. Any of an insulating substrate, an n-type substrate, and a p-type substrate may be used as the semiconductor substrate. In particular, a substrate made of Si, GaAs or SiC is easier to etch than GaN. Therefore, when a substrate made of Si, GaAs or SiC is used, a stripe-shaped concave portion can be easily formed on the substrate by etching. Thereby, it is possible to easily form the GaN layer 13 with reduced dislocation.

For example, a predetermined region on the surface of an n-type 6H-SiC substrate having a (0001) plane as a substrate surface is etched by RIE or the like, and has a width of about 14 μm, a height of about 1 μm, and [11-20]. ] To form a stripe-shaped concave portion extending in the direction. Thus, an n-type 6H-SiC substrate having a stripe-shaped concave portion on the surface is manufactured. Or,
A predetermined region on the surface of the n-type Si substrate having the (111) plane as a substrate surface is removed by wet etching or the like, and the width is reduced to about 2
A stripe-shaped concave portion having a size of 2 μm, a height of about 2 μm and extending in the [1-10] direction is formed. In this case, the side surface of the concave portion includes the (110) plane and the (001) plane. Thereby, an n-type Si substrate having a stripe-shaped concave portion on the surface is manufactured.

Further, in the above description, the stripe-shaped uneven pattern is formed on the substrate, but the uneven pattern formed on the substrate may be other than the stripe pattern.

On a n-type 6H-SiC substrate or an n-type Si substrate having the above-described stripe-shaped concave portions, AlG is formed by the method of forming a nitride-based semiconductor shown in FIGS.
When the aN buffer layer 12 and the GaN layer 13 are formed, first, the MOVP
A single crystal AlGaN buffer layer 1 of n-Al _0.09 Ga _0.91 N having a thickness of about 0.05 μm was formed on the substrate by the E method.
Form 2 Further, with the substrate temperature kept at 1150 ° C., the AlGaN buffer layer 12 was formed by MOVPE.
A GaN layer 13 of about 10 μm in thickness made of n-GaN
To form

As described above, when the n-type 6H-Si substrate or the n-type Si substrate is used in the method of forming the nitride-based semiconductor shown in FIGS. The same effect can be obtained.

It should be noted that a group IV semiconductor such as Si or Ge, SiC
GaAs, InP, a semiconductor substrate made of a group IV-IV semiconductor such as II or a group II-VI semiconductor such as ZnSe, and a lattice constant of the semiconductor substrate different from a lattice constant of the nitride-based semiconductor layer.
In the case of a semiconductor substrate made of a III-V semiconductor such as GaP, a single crystal buffer layer may be formed as the AlGaN buffer layer 12 as described above.
The same effect can be obtained by forming a non-single-crystal buffer layer at a temperature of ℃.

Further, the shape of the unevenness is not limited to the above shape. FIG. 6A is a schematic cross-sectional view showing another example of the substrate used in the method for forming the nitride-based semiconductor shown in FIGS. 4 and 5.

As shown in FIG. 6A, the surface of the substrate 21 is formed with a saw-toothed uneven pattern.
For example, in the substrate 21 made of sapphire having a sawtooth-shaped uneven pattern, the side surface of the concave portion is an R surface, that is, (1
-101) It is composed of a plane equivalent to the plane.

In the case where such a substrate 21 is used, the same effect as in the case where the sapphire substrate 11 having the above-mentioned stripe-shaped uneven pattern is used can be obtained. In this case, in the region of the GaN layer 13 formed on the concave portion of the substrate 21, a portion where dislocations are concentrated occurs linearly.

Further, the substrate may be a substrate in which a plurality of concave portions or convex portions having a shape such as a circle, a hexagon, and a triangle are dispersedly arranged. This case will be described below.

FIG. 6B is a plan view showing still another example of the substrate used in the method for forming the nitride semiconductor shown in FIGS.

As shown in FIG. 6B, a hexagonal concave portion or convex portion is formed on the surface of the substrate 31.

In the case where such a substrate 31 is used, similarly to the case where the sapphire substrate 11 having the above-mentioned stripe-shaped uneven pattern is used, the effect that the dislocation of the GaN layer is uniformly reduced is obtained. Can be

Further, the substrate 3 on which the hexagonal concave portions are formed
In the case of using No. 1, a region where the dislocation density is particularly reduced is formed on the concave portion excluding the central portion. In this case, in the central portion of the GaN layer formed on the hexagonal concave portion of the substrate 31, a portion where dislocations are concentrated occurs, and a region having a relatively high dislocation density is formed.

On the other hand, the substrate 31 on which the hexagonal projections are formed
In the case where is used, a region where the dislocation density is particularly reduced is formed on the concave portion except for the central portion on the concave portion between the convex portions. In this case, in the central region of the GaN layer formed on the concave portion between the hexagonal convex portions of the substrate 31, a portion where dislocations are concentrated occurs linearly, and the dislocation density is relatively low. High areas are formed.

As described above, the dislocation of the GaN layer is uniformly reduced, but the central region of the GaN layer formed on the hexagonal concave portion of the substrate 31 or the hexagonal convex portion of the substrate 31 is formed. A region having a relatively high dislocation density is formed in the central region of the GaN layer formed on the concave portion between the portions. For this reason, at the time of manufacturing a semiconductor device, an element region is formed in a region excluding a central portion on a hexagonal concave portion of the substrate 31 or a region excluding a central portion on a concave portion between hexagonal convex portions of the substrate 31. Is preferred. Further, since a region having a particularly reduced dislocation density is formed on the hexagonal concave portion excluding the central portion or on the concave portion excluding the central portion between the hexagonal convex portions, the center on the hexagonal concave portion of the substrate 31 is formed. Area on the concave part except the part or the substrate 3
More preferably, the element region is formed in a region on the concave portion except for a central portion on the concave portion between the hexagonal convex portions.

Further, as the substrate 31, a sapphire substrate may be used, or an insulator substrate such as spinel may be used. Alternatively, a semiconductor substrate made of a group IV semiconductor such as Si or Ge, a group IV-IV semiconductor such as SiC or a group II-VI semiconductor such as ZnSe, or a lattice constant of the semiconductor substrate is different from a lattice constant of the nitride-based semiconductor layer. GaAs, InP, G
A semiconductor substrate made of a III-V group semiconductor such as aP may be used. Any of an insulating substrate, an n-type substrate, and a p-type substrate may be used as the semiconductor substrate. In particular, a substrate made of Si, GaAs or SiC is easier to etch than GaN. Therefore, Si, GaAs or SiC
When a substrate made of is used, a stripe-shaped concave portion can be easily formed in the substrate by etching. Thereby, it is possible to easily form the GaN layer 13 with reduced dislocation.

It should be noted that even when a substrate having a concave or convex portion other than a hexagon such as a circle or a triangle is used,
As in the case where the substrate 31 having hexagonal concave portions or convex portions is used, a portion where dislocations are concentrated occurs in the GaN layer.

In the case where a substrate 31 having a hexagonal uneven pattern as shown in FIG. 6B or a substrate having a triangular uneven pattern is manufactured, each side of a hexagon or a triangle is formed. The forming direction may coincide with any crystal orientation of the substrate.

When a hexagonal or triangular concavo-convex pattern is formed on a sapphire substrate or a SiC substrate having the (0001) plane as a substrate surface, each side is equivalent to the [1-100] direction or the [11-20] direction. It is preferable to form a hexagonal or triangular concavo-convex pattern so as to match the direction. On the other hand, when forming a hexagonal or triangular concavo-convex pattern on a Si substrate having the (111) plane as a substrate surface,
It is preferable to form a hexagonal or triangular concavo-convex pattern such that each side coincides with a direction equivalent to the [1-10] direction or the [11-2] direction.

FIGS. 7 and 8 are schematic process sectional views showing a method of forming a nitride semiconductor according to still another embodiment of the second invention.

As shown in FIG. 7A, the off surface inclined at a predetermined angle from the C plane of the sapphire substrate 41 in a predetermined direction is etched by RIE or the like. Thereby, a step-like step extending in a stripe shape in a predetermined direction is formed on the off surface of the sapphire substrate 41. In this case, the C surface is exposed on the bottom surface of the step of the sapphire substrate 41.

The step formed by the etching has a larger size than the step of the atomic order originally existing on the off surface of the sapphire substrate 41. In the sapphire substrate 41, the width of the bottom surface of the step is preferably several μm to several tens μm, and the height of the step is preferably several nm to several μm. For example, in this example, the width of the bottom surface of the step is set to about 29 μm, and the height of the step is set to about 1 μm.

The direction in which the step is formed is not particularly limited. For example, in this example, the off-surface of the sapphire substrate inclined at 2 ° in the [11-20] direction from the C plane is etched to form a step-like step extending in a stripe shape in the [1-100] direction. . In addition to this, for example, a step-like step extending in a stripe shape in the [11-20] direction may be formed.

As shown in FIG. 7B, the undoped AlG was deposited on the bottom and side surfaces of the step of the sapphire substrate 41 by MOVPE while maintaining the substrate temperature at 600 ° C.
AlGaN buffer layer 42 made of aN and having a thickness of 15 nm
To form In this case, the AlGaN buffer layer 42
On the bottom and side surfaces of the step of the sapphire substrate 41,
It grows in the direction of arrow Y (c-axis direction) and in the direction of arrow X (lateral direction) in the figure. AlG grown in this way
The surface of the aN buffer layer 42 has a step-like step extending like a stripe like the sapphire substrate 41.

Subsequently, as shown in FIG. 7C, while the substrate temperature was kept at 1150 ° C., the Al
A GaN layer 43 made of undoped GaN is grown on the bottom and side surfaces of the step of the GaN buffer layer. In this case, the GaN layer 43 in the initial stage of growth grows in the direction of arrow Y on the bottom and side surfaces of the step of the AlGaN buffer layer 42, and then grows in the direction of arrow X. The surface of the GaN layer 43 in the initial stage of the growth has a step-like step extending like a stripe like the AlGaN buffer layer 42.

As shown in FIG. 8D, as the growth of the GaN layer 43 in the direction of arrow Y in the figure progresses, the growth of the GaN layer 43 in the direction of arrow X becomes dominant.
In this case, on the GaN layer 43 on the bottom surface of each step of the step, the GaN layer 43 on the upper bottom surface and the upper side surface grows laterally. Thereby, the steps on the surface of the GaN layer 43 are gradually filled. Note that such a GaN layer 43
In the growth of GaN, voids are hardly generated. Note that voids may remain.

Here, since the GaN layer 43 grows in the lateral direction, the dislocations generated in the vicinity of the sapphire substrate 41 and propagated in the c-axis direction are generated in the lateral direction (arrows) as the GaN layer 43 grows in the lateral direction. X direction), that is, in a direction parallel to the (0001) plane of the GaN layer 43. Thereby, in the GaN layer 43, dislocations propagating in the c-axis direction are reduced.

As shown in FIG. 8E, as the growth of the GaN layer 43 further proceeds, the surface of the GaN layer 43 is flattened. On the surface of the GaN layer 43 thus formed, dislocations are reduced and good crystallinity is obtained.

According to the method for forming a nitride-based semiconductor as described above, the GaN layer 43 is laterally grown without using a selective growth mask by utilizing the step-shaped steps formed on the sapphire substrate 41. Dislocations can be reduced. Therefore, GaN with good crystallinity
Layer 43 can be formed.

In the above-described method of forming a nitride-based semiconductor, since a selective growth mask is not used, it is possible to prevent cracks in the GaN layer 43 due to a difference in thermal expansion coefficient between the selective growth mask and GaN. . In some cases, it is also possible to prevent the occurrence of voids.

As described above, when a nitride-based semiconductor layer including an element region is formed on the GaN layer 43 to manufacture a semiconductor device, the nitride-based semiconductor layer formed on the GaN layer 43 has good crystallinity. Can be obtained, and the occurrence of cracks in the element separation step or the like can be prevented. Thereby, a semiconductor device having good device characteristics and high reliability can be obtained.

In the above description, the sapphire substrate 4
Although 1 is used, an insulating substrate such as spinel may be used. Alternatively, a semiconductor substrate made of a group IV semiconductor such as Si or Ge, a group IV-IV semiconductor such as SiC or a group II-VI semiconductor such as ZnSe, or a lattice constant of the semiconductor substrate is different from a lattice constant of the nitride-based semiconductor layer. GaAs, InP, G
A semiconductor substrate made of a III-V group semiconductor such as aP may be used. Any of an insulating substrate, an n-type substrate, and a p-type substrate may be used as the semiconductor substrate. In particular, Si, GaAs, Si
The substrate made of C is more easily etched than GaN. Therefore, a substrate having the above-described stepped step can be easily manufactured.

For example, an n-type 6H-SiC substrate (000
1) The off plane inclined at 4 ° in the [1-100] direction from the plane is denoted by R
Etching is performed by the IE method. Thus, the n-type 6
On the off surface of the H-SiC substrate, a step-like step having a bottom surface width of about 14 μm, a step height of about 1 μm, and extending in a stripe shape in the [11-20] direction may be formed.
Alternatively, a step-like step extending in a stripe shape in the [11-100] direction may be formed on the n-type 6H-SiC substrate.

Further, the off surface inclined by 5 ° in the [11-2] direction from the (111) plane of the n-type Si substrate is wet-etched. Thus, on the off surface of the n-type SiC substrate, the width of the bottom surface is about 22 μm and the height of the step is about 2 μm.
And a step-like step extending in a stripe shape in the [1-10] direction may be formed. Alternatively, a step-like step extending in a stripe shape in the [11-2] direction may be formed on the n-type Si substrate.

On a n-type 6H-SiC substrate or an n-type Si substrate having the above-mentioned stripe-shaped concave portions, AlG is formed by the method of forming a nitride-based semiconductor shown in FIGS.
When forming the aN buffer layer 42 and the GaN layer 43, first, the MOVP
An AlGaN buffer layer 42 of n-Al _0.09 Ga _0.91 N having a thickness of about 0.05 μm is formed on the substrate by the E method. Further, while maintaining the substrate temperature at 1150 ° C., M
By the OVPE method, n-
A GaN layer 43 made of GaN and having a thickness of about 10 μm is formed.

As described above, the n-type 6H-SiC substrate or n-type
When the type SiC substrate is used in the method of forming the nitride-based semiconductor shown in FIGS. 7 and 8, the same effects as those described above can be obtained when the sapphire substrate 41 is used.

FIG. 9 is a schematic process sectional view showing a method of forming a nitride-based semiconductor according to one embodiment of the third invention.

As shown in FIG. 9 (a), on the C surface of the sapphire substrate 51, while maintaining the substrate temperature at 600.degree.
A 15 nm thick AlGaN buffer layer 52 made of undoped AlGaN is formed by OVPE.

Subsequently, as shown in FIG.
A predetermined region of the aN buffer layer 52 is etched by RIE or the like. The width w [μm] of etching the AlGaN buffer layer 52 is preferably about 1 to 40 μm, and the width b [μ] of the AlGaN buffer layer 52 that is left after etching.
m] is preferably about 1 to 40 μm. For example, in this embodiment, w [μm] = 8 μm and b [μm] = 4 μm. Thereby, a plurality of stripe-shaped A
While forming the lGaN buffer layer 52a,
The sapphire substrate 51 is exposed between the aN buffer layers 52a.

Here, as shown particularly in FIG. 10, the width w of the AlGaN buffer layer 52 to be etched and the remaining A
The width b [μm] of the lGaN buffer layer 52 is b [μm] ≦
−w [μm] +40 [μm] and b [μm] ≧ 1 [μm]
It is preferable that the value be within a range surrounded by と and w [μm] ≧ 1 [μm]. When the width w [μm] of the AlGaN buffer layer 52 to be etched is smaller than 1 μm and when the width b [μm] of the remaining AlGaN buffer layer 52 is smaller than 1 μm, the etching of AlGaN
It becomes difficult to pattern the buffer layer 52. On the other hand, the width w [μm] of the AlGaN buffer layer 52 to be etched
When the width b [μm] of the remaining AlGaN buffer layer 52 satisfies the relationship of b [μm]> − w [μm] +40 [μm], the A formed by patterning
GaN to be described later grown on the lGaN buffer layer 52a
The flattening of the layer 53 tends to be difficult.

As described above, the AlGaN buffer layer 52a
After forming the substrate, as shown in FIG.
With the temperature kept at 150 ° C., a GaN layer 53 made of undoped GaN is grown by MOVPE. Here, since GaN and the sapphire substrate 51 have different lattice constants, if the GaN and the sapphire substrate 51 do not pass through the AlGaN buffer layer 52a,
GaN hardly grows on the sapphire substrate 51. Therefore, in the initial stage of growth, the GaN layer 53 selectively grows on the AlGaN buffer layer 52a. In this case, Ga
The N layer 53 grows in the direction of the arrow Y (c-axis direction) in the figure,
It has a facet structure. In this portion, there are many dislocations generated near the sapphire substrate 51.

As shown in FIG. 9D, as the growth of the GaN layer 53 in the direction of arrow Y progresses, the GaN layer 53 grown on the AlGaN buffer layer 52a also moves in the direction of arrow X (lateral direction). grow up. Thereby, on the sapphire substrate 51 exposed between the AlGaN buffer layers 52a,
A GaN layer 53 is formed.

Here, since the GaN layer 53 as described above grows in the lateral direction, the dislocation in the GaN layer 53 generated on the AlGaN buffer layer 52a in FIG. Accordingly, the GaN layer 53 is bent in the horizontal direction (the direction of arrow X), that is, in a direction parallel to the (0001) plane of the GaN layer 53. Thereby, in the GaN layer 53, dislocations propagating in the c-axis direction are uniformly reduced. Further, a region where the dislocation density is particularly reduced is formed in a region other than the central portion of the GaN layer 53 formed on the exposed sapphire substrate 51. In this case, in the central region of the GaN layer 53 formed on the exposed sapphire substrate 51, a portion where dislocations are concentrated occurs linearly, and a region having a relatively high dislocation density is formed. .

As shown in FIG. 9E, when the GaN layer 53 is further grown, the facet-structured GaN layers 53 are united to form a continuous film, and a flattened GaN layer 53 having a thickness of about 10 μm is formed. Is done. Dislocations are reduced on the surface of the GaN layer 53 thus formed, and good crystallinity is obtained. Further, in this case, voids are less likely to occur in the united portion of the GaN layer 53 grown from the lateral direction. Note that voids may remain.

According to the above-described method for forming a nitride-based semiconductor, the GaN layer 53 can be formed without using a selective growth mask by using the plurality of stripe-shaped AlGaN buffer layers 52a formed on the sapphire substrate 51. It is possible to grow laterally and reduce dislocations. Therefore, the GaN layer 53 having good crystallinity can be formed.

In this case, the AlGaN buffer layer 52 is non-single crystal because it grows at a low temperature. Therefore, AlG
The aN buffer layer 52 can be etched more easily than GaN. In the above-described method for forming a nitride-based semiconductor, the step of growing GaN is performed only once when the GaN layer 53 is formed. Therefore, according to the above-described method for forming a nitride-based semiconductor, the GaN layer 53 with reduced dislocations can be easily formed.

In the above-described method for forming a nitride-based semiconductor, since the selective growth mask is not used, the GaN layer 5 is formed.
In 3, the generation of cracks due to the difference in thermal expansion coefficient between the selective growth mask and GaN can be prevented, and the generation of voids can be prevented. Note that voids may remain.

As described above, when a nitride-based semiconductor layer including an element region is formed on the GaN layer 53 to manufacture a semiconductor device, the nitride-based semiconductor layer formed on the GaN layer 53 has good crystallinity. Can be obtained, and the occurrence of cracks in the element separation step or the like can be prevented. Thereby, a semiconductor device having good device characteristics and high reliability can be obtained.

As described above, the dislocation of the GaN layer 53 is reduced uniformly, but in the central region of the GaN layer 53 on the exposed region of the sapphire substrate 51, a region having a relatively high dislocation density is formed. Is formed. For this reason, when manufacturing a semiconductor device, it is preferable to form the device region in a region other than the central portion on the exposed region of the sapphire substrate 51. Further, since a region having a particularly reduced dislocation density is formed on the exposed region of the sapphire substrate 51 except for the central portion, the region on the exposed region of the sapphire substrate 11 except for the central portion is formed on the exposed region of the sapphire substrate 11. More preferably, an element region is formed.

In the above, the sapphire substrate 51
However, an insulating substrate such as spinel may be used. Alternatively, a group IV semiconductor such as Si, Ge, etc .;
A semiconductor substrate made of a group IV-IV semiconductor or a group II-VI semiconductor such as ZnSe, or GaAs, InP, Ga having a lattice constant of the semiconductor substrate different from that of the nitride-based semiconductor layer.
A semiconductor substrate made of a group III-V semiconductor such as P may be used. Any of an insulating substrate, an n-type substrate, and a p-type substrate may be used as the semiconductor substrate.

For example, a SiC substrate or a Si substrate is
In the method of forming a nitride-based semiconductor shown in (1), the substrate temperature was kept at 1150 ° C., and the
An AlGaN buffer layer 52 of n-Al _0.09 Ga _0.91 N having a thickness of about 0.05 μm is formed on a C substrate or a Si substrate. Subsequently, the AlGaN buffer layer 52 is etched by the same method as when the sapphire substrate 51 is used, and a plurality of stripe-shaped AlGaN buffer layers 52 are formed.
a is formed. Then, with the substrate temperature kept at 1150 ° C., the Ga
The N layer 53 is grown on the AlGaN buffer layer 52a, and the GaN layer 53 is grown laterally to expose the exposed S layer.
A GaN layer 53 is grown on an iC substrate or a Si substrate. The flattened G film having a thickness of about 10 μm
An aN layer 53 is formed.

As described above, when the SiC substrate or the Si substrate is used in the method of forming the nitride semiconductor shown in FIG. 9, the same effects as those described above can be obtained when the sapphire substrate 51 is used.

A group IV semiconductor such as Si or Ge, SiC
GaAs, InP, a semiconductor substrate made of a group IV-IV semiconductor such as II or a group II-VI semiconductor such as ZnSe, and a lattice constant of the semiconductor substrate different from a lattice constant of the nitride-based semiconductor layer.
In the case of a semiconductor substrate made of a III-V semiconductor such as GaP, a single crystal buffer layer may be formed as the AlGaN buffer layer 52 as described above.
The same effect can be obtained by forming a non-single-crystal buffer layer at a temperature of ℃.

In the above description, a plurality of stripe-shaped AlGaN buffer layers 52a are formed on the substrate at predetermined intervals. However, the pattern of the AlGaN buffer layer 52a formed on the substrate is not limited to a stripe. is not.

For example, a plurality of AlGaN buffer layers 52a having a shape such as a circle, a hexagon, and a triangle may be formed on a substrate. Thereby, in the GaN layer 53,
Dislocations propagating in the c-axis direction are uniformly reduced. further,
Except for the exposed central part of the substrate between the AlGaN buffer layers 52a, a region where the dislocation density is particularly reduced is formed on the exposed substrate. In this case, in the region of the GaN layer 53 formed on the central portion of the exposed substrate between the AlGaN buffer layers 52a, a portion where dislocations are concentrated occurs linearly, and a region having a relatively high dislocation density is formed. It is formed.

As described above, although the dislocation of the GaN layer 53 is uniformly reduced, the GaN layer 53 formed on the exposed central portion of the substrate between the AlGaN buffer layers 52a is formed.
In this region, a region having a relatively high dislocation density is formed. For this reason, at the time of manufacturing a semiconductor device, it is preferable to form the device region in a region excluding the central portion on the exposed substrate between the AlGaN buffer layers 52a. Furthermore, AlG
Except for the central portion of the exposed substrate on the substrate between the aN buffer layers 52a, a region with a particularly reduced dislocation density is formed on the exposed substrate. It is preferable that the element region is formed in the region of the substrate which has been removed and is exposed.

Alternatively, in the AlGaN buffer layer 52 formed on the substrate, a plurality of regions having a shape such as a circle, a hexagon, and a triangle are removed by etching, and
A plurality of openings having a shape such as hexagon, triangle, etc.
It may be formed on the aN buffer layer 52. In this case, the GaN layer 53 formed on the central portion of the substrate exposed in the plurality of openings having a shape such as a circle, a hexagon, and a triangle.
In this region, a portion where dislocations are concentrated occurs, and a region having a relatively high dislocation density is formed.

Although the dislocation of the GaN layer 53 is uniformly reduced as described above, the GaN layer 53
In the central region of the layer 53, a region having a relatively high dislocation density is formed. For this reason, at the time of manufacturing a semiconductor device, it is preferable to form the device region in a region other than the central portion on the exposed region of the substrate. Furthermore, since a region having a particularly reduced dislocation density is formed on the exposed region of the substrate except for the central portion, an element region is formed on the exposed region of the substrate except for the central portion. More preferably,

Although a sapphire substrate can be used as the substrate, an insulating substrate such as spinel may be used. Alternatively, a group IV semiconductor such as Si, Ge, etc .;
A semiconductor substrate made of a group IV-IV semiconductor or a group II-VI semiconductor such as ZnSe, or GaAs, InP, Ga having a lattice constant of the semiconductor substrate different from that of the nitride-based semiconductor layer.
A semiconductor substrate made of a group III-V semiconductor such as P may be used. Any of an insulating substrate, an n-type substrate, and a p-type substrate may be used as the semiconductor substrate.

Next, a semiconductor device manufactured by using the method for forming a nitride semiconductor according to the first to third aspects of the present invention will be described. In this case, a semiconductor laser device will be described as an example of the semiconductor device.

A semiconductor laser device according to a fourth invention is a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the first invention.

FIG. 11 is a schematic perspective view showing a semiconductor laser device according to one embodiment of the fourth invention.

As shown in FIG. 11, the semiconductor laser device 5
1, the AlGaN first buffer layer 2, the GaN second buffer layer 3 made of undoped GaN, and the GaN second buffer layer 3 made of undoped GaN are formed on the sapphire substrate 1 by the method of forming the nitride semiconductor shown in FIGS. 1 and 2. 1Ga
An N layer 4 and a second GaN layer 5 made of undoped GaN are sequentially formed.

Further, MOVPE, HVPE, trimethylaluminum, trimethylgallium, trimethylindium, NH ₃ , SiH ₄ (silane gas),
The second G is obtained by a gas source MBE method using CpMg (cyclopentadienyl magnesium) as a source gas.
A 4 μm-thick n-G layer of n-GaN is formed on the aN layer 5.
aN contact layer 104, n-AlGaInN crack preventing layer 105 of about 0.1 μm in thickness made of n-AlGaInN, n of 0.45 μm in thickness of n-AlGaN
An AlGaN second cladding layer 106, an n-GaN first cladding layer 107 made of n-GaN and having a thickness of about 50 nm;
Multiple quantum well (MQW) light emitting layer 10 made of InGaN
8. A p-GaN first cladding layer 109 having a thickness of about 40 nm made of p-GaN is sequentially laminated. p-GaN
PA is applied to the stripe-shaped region on the first cladding layer 109.
A 0.45 μm-thick p-AlGaN second cladding layer 110 made of lGaN is formed. Thus, p
A ridge portion composed of the AlGaN second cladding layer 110 is formed, and the p-GaN first cladding layer 109 is formed.
Is formed.

The ridge extends in the direction of the first Ga.
It is preferable to form the N layer 4 in a direction perpendicular to the off direction.

In this case, the MQW light emitting layer 108
It has a multiple quantum well structure in which five undoped GaN barrier layers with a thickness of about 4 nm and four undoped InGaN well layers with a thickness of about 4 nm are alternately stacked.

On the p-GaN first cladding layer 109 and on the side surfaces of the p-AlGaN second cladding layer 110, n-G
An n-GaN current confinement layer 111 made of aN and having a thickness of about 0.2 μm is formed. In this case, the n-GaN current confinement layer 11 is formed on the upper surface of the p-AlGaN second cladding layer 110.
One stripe-shaped opening is formed. n-Ga
Top and side surfaces of N current confinement layer 111, and p-A
On the 1GaN second cladding layer 110, a p-GaN contact layer 112 made of p-GaN and having a thickness of 3 to 5 μm is formed.

From the p-GaN contact layer 112 to the n-G
A part of the region up to the aN contact layer 104 is etched, and a predetermined region of the n-GaN contact layer 104 is exposed. An n-electrode 113 is formed on a predetermined region of the exposed n-GaN contact layer 4. Also, p-G
A p-electrode 114 is formed in a predetermined region on the aN contact layer 112. Note that, on the side surfaces from the exposed p-GaN contact layer 112 to the n-GaN first contact layer 104 and on the upper surface of the n-GaN contact layer 104, S
An iO ₂ film 115 is formed.

In the above-described semiconductor laser device 500, each of the layers 104 to 11 is formed on the second GaN layer 5 formed by the nitride semiconductor forming method shown in FIGS.
2 are formed. Here, as described above with reference to FIGS. 1 and 2, since the dislocation is reduced on the surface of the second GaN layer 5, each of the layers 104 to 115 formed on the second GaN layer 5 has good crystallinity. Is realized. Thus, the semiconductor laser device 500 has good device characteristics and high reliability.

In this case, dislocations can be reduced in second GaN layer 5 without using a selective growth mask as described above.
In the method, cracks due to a difference in thermal expansion coefficient between the selective growth mask and GaN are prevented, and voids are also prevented.

Therefore, at the time of manufacturing the semiconductor laser device 500, generation of cracks in the device separation step and the like is prevented. Thereby, a high yield can be realized.

In the above, instead of the sapphire substrate 1, a substrate made of an insulator other than sapphire may be used.

FIG. 12 is a schematic perspective view showing a semiconductor laser device according to another embodiment of the fourth invention.

[0205] As shown in FIG.
01 has the same structure as the semiconductor laser device 500 of FIG. 11 except for the following points.

In this case, instead of sapphire substrate 1, AlGaN first buffer layer 2 made of n-AlGaN is formed on n-Si substrate 1A by the method of forming a nitride-based semiconductor shown in FIGS. , GaN second buffer layer 3 made of n-GaN, first Ga made of n-GaN
An N layer 4 and a second GaN layer 5 made of n-GaN are sequentially formed.

In this case, the p-GaN contact layer 112 is formed on the n-GaN current confinement layer 111 and the p-AlGaN second cladding layer 110. An n-electrode 113 is formed on the back surface of the n-Si substrate 1A, and a p-electrode 114 is formed on the upper surface of the ridge portion of the p-GaN contact layer 112.

In such a semiconductor laser element 501, dislocations are reduced in the second GaN layer 5 formed by the method of forming a nitride semiconductor shown in FIGS. Is prevented from occurring. Therefore, in the semiconductor laser device 501, the same effects as those described above in the semiconductor laser device 500 can be obtained.

In the above, a substrate made of a semiconductor other than Si may be used instead of n-Si substrate 1A.

Further, the semiconductor laser devices 500 and 501
In the above, an n-type semiconductor layer and a p-type semiconductor layer are sequentially formed on the substrates 1 and 1A.
The type semiconductor layer and the n-type semiconductor layer may be sequentially formed.

Furthermore, the semiconductor laser devices 500 and 501
In the method, the respective layers 2 to 5 are formed on the substrates 1 and 1A by the method of forming the nitride semiconductor shown in FIGS. 1 and 2, but the substrates 1 and 1 are formed by the method of forming the nitride semiconductor shown in FIG. Each layer 2, 3, 4a, 5a may be formed on 1A. In this case, in the manufactured semiconductor laser device, the same effects as those described above in the semiconductor laser devices 500 and 501 can be obtained.

[0212] Here, in the 2GaN layer 5a of Figure 3 formed by the method of forming a nitride-based semiconductor shown in FIG. 3, lateral overgrowth of the 1GaN layer 4a of Figure 3 using the SiO ₂ film 15 As a result, dislocations are further reduced. Therefore, the respective layers 104 to 112 of FIG. 11 or FIG. 12 formed on the second GaN layer 5a of FIG.
In, the crystallinity is further improved. Thereby, in the semiconductor laser device in this case, the device characteristics and the reliability are further improved.

The semiconductor laser device according to the fifth invention is a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the second invention. This case will be described below.

The semiconductor laser device according to one embodiment of the fifth invention has the same structure as the semiconductor laser device 500 of FIG. 11 except for the following points.

In this case, the undoped AlGaN is formed on the sapphire substrate 11 by the method of forming the nitride-based semiconductor shown in FIGS. 4 and 5 as shown in FIGS.
An AlGaN buffer layer 12 made of GaN and a GaN layer 13 made of undoped GaN are sequentially formed. On this GaN layer 13, the layers 104 to 112 of FIG. 11 are formed. In addition, instead of the sapphire substrate 11,
A substrate made of an insulator other than sapphire may be used.

In the semiconductor laser device of this example, the GaN layer 13 of FIG. 5 formed by the method of forming a nitride-based semiconductor shown in FIGS. 4 and 5 has reduced dislocations and has cracks and Void formation is prevented. Therefore, each layer 1 of FIG. 11 is placed on the GaN layer 13 of FIG.
In the semiconductor device of this example in which the semiconductor devices 04 to 112 are formed, the same effects as those described above in the semiconductor laser device 500 can be obtained. Note that voids may remain.

Here, in this example, FIGS.
As shown in FIG.
By growing N, a GaN layer 13 with reduced dislocations is formed. Therefore, the semiconductor laser device of this example is easy to manufacture.

A semiconductor laser device according to another embodiment of the fifth invention has the same structure as the semiconductor laser device 501 of FIG. 12, except for the following points.

In this case, as shown in FIGS. 4 and 5, AlGa made of n-AlGaN is formed on the n-Si substrate by the method of forming the nitride-based semiconductor shown in FIGS.
N buffer layer 12 and GaN layer 1 composed of n-GaN
3 are formed. The GaN layer 13 shown in FIG.
Two layers 105 to 112 are formed. Note that n-
A substrate made of a semiconductor other than Si may be used instead of the Si substrate.

In the semiconductor laser device of this example, the GaN layer 13 of FIG. 5 formed by the method of forming a nitride semiconductor shown in FIGS. 4 and 5 has reduced dislocations, and has cracks and Void formation is prevented. Therefore, each layer 1 of FIG. 12 is placed on the GaN layer 13 of FIG.
In the semiconductor laser device of this example in which the layers 05 to 112 are formed, the same effects as those described above in the semiconductor laser device 501 can be obtained. Note that voids may remain.

Here, in this example, FIGS.
As shown in FIG.
By growing N, a GaN layer 13 with reduced dislocations is formed. Therefore, the semiconductor laser device of this example is easy to manufacture.

In particular, in this example, since an n-Si substrate which is easily etched is used, a concave portion as shown in FIG. 4 can be easily formed by etching. Therefore, the semiconductor laser device of this example is easier to manufacture.

In the semiconductor laser device according to the two embodiments of the fifth invention, dislocations are uniformly reduced as described above with reference to FIGS. 4 and 5, so that the nitride-based semiconductor layer The above-described effects can be obtained even if an element region (light emitting portion) is formed in any part of the device. However, in the central region of the nitride-based semiconductor layer on the concave portion of the substrate,
A region having a relatively high dislocation density is formed. For this reason, in the semiconductor laser device, it is preferable to form an element region (light emitting portion) in a region other than the center portion on the concave portion of the substrate.
Further, since a region having a particularly reduced dislocation density is formed on the concave portion excluding the central portion, an element region (light emitting portion) can be formed in a region on the concave portion except for the central portion on the concave portion of the substrate. preferable.

FIGS. 7 and 8 show a semiconductor laser device according to still another embodiment of the fifth invention, which is formed by the method of forming a nitride semiconductor shown in FIGS. 7 and 8.
As shown in FIG. 8, an AlGaN buffer layer 42 and a GaN layer 43 are sequentially formed on a substrate.
A semiconductor laser device in which the layers 104 to 112 of FIG. 11 or 12 are formed thereon may be used. Also in such a semiconductor laser device, the AlG shown in FIGS. 4 and 5 is formed by the method of forming the nitride-based semiconductor shown in FIGS.
The same effects as described above can be obtained in the semiconductor laser devices of the above two embodiments in which the aN buffer layer 12 and the GaN layer 13 are formed.

A semiconductor laser device according to a sixth invention is a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the third invention. This case will be described below.

The semiconductor laser device according to the sixth embodiment of the present invention has the same structure as the semiconductor laser device 500 shown in FIG. 11 except for the following points.

In this case, the sapphire substrate 51 is formed as shown in FIG. 9 by the method of forming the nitride semiconductor shown in FIG.
A plurality of striped AlGaN buffer layers 52a made of undoped AlGaN are formed thereon.
Further, on the AlGaN buffer layer 52a and on the AlGa
Sapphire substrate 51 exposed between N buffer layers 52a
A GaN layer 53 made of undoped GaN is formed thereon. The layers 104 to 112 of FIG. 10 are formed on the GaN layer 53 of FIG. Instead of the sapphire substrate 51, a substrate made of an insulator other than sapphire may be used.

In the semiconductor laser device of this example, the GaN layer 53 of FIG. 9 formed by the method of forming a nitride semiconductor shown in FIG. 9 can reduce dislocations and prevent cracks and voids. Have been. Therefore, each of the layers 104 to 11 of FIG. 11 is formed on the GaN layer 53 of FIG.
In the semiconductor laser device of the present example in which 2 is formed, the same effects as those described above in the semiconductor laser device 500 can be obtained. Note that voids may remain.

Here, in this example, as shown in FIG. 9, by growing GaN once on the AlGaN buffer layer 52a, a GaN layer 53 with reduced dislocation is obtained. Further, in this example, Al grown at a low temperature is used.
Since the etching of the GaN buffer layer 52 is easy, a plurality of striped AlGaN buffer layers 52a are formed.
Can be easily formed. Therefore, the semiconductor laser device of this example is easy to manufacture.

A semiconductor laser device according to another embodiment of the sixth invention has the same structure as the semiconductor laser device 501 of FIG. 12, except for the following points.

In this case, according to the method of forming a nitride-based semiconductor shown in FIG. 9, as shown in FIG.
Plural stripe-shaped AlGa made of n-AlGaN
An N buffer layer 52a is formed. Furthermore, AlG
aN buffer layer 52a and AlGaN buffer layer 5
The GaN layer 53 made of n-GaN is formed on the n-Si substrate exposed between 2a. The GaN of FIG.
The layers 105 to 112 of FIG. 12 are formed on the layer 53. Note that a substrate made of a semiconductor other than Si may be used instead of the Si substrate.

In the semiconductor laser device of this example, the GaN layer 53 of FIG. 9 formed by the method of forming a nitride semiconductor shown in FIG. 9 can reduce dislocations and prevent cracks and voids. Have been. Therefore, each layer 105 to 11 of FIG. 12 is formed on the GaN layer 53 of FIG.
In the semiconductor laser device of the present example in which 2 is formed, the same effects as those described above in the semiconductor laser device 501 can be obtained. Note that voids may remain.

Here, in this example, as shown in FIG. 9, by growing GaN once on the AlGaN buffer layer 52a, a GaN layer 53 with reduced dislocations can be obtained. Further, in this example, Al grown at a low temperature is used.
Since the etching of the GaN buffer layer 52 is easy, a plurality of striped AlGaN buffer layers 52a are formed.
Can be easily formed. Therefore, the semiconductor laser device of this example is easy to manufacture.

In the semiconductor laser device according to the two embodiments of the sixth invention, as described above with reference to FIG.
Since the dislocation is uniformly reduced, the above-described effect can be obtained even if an element region (light emitting portion) is formed in any part of the nitride-based semiconductor layer on the substrate. However, a region having a relatively high dislocation density is formed in the central region of the nitride-based semiconductor layer on the exposed region of the substrate. For this reason, in a semiconductor laser device, it is preferable to form an element region (light emitting portion) in a region other than a central portion on an exposed region of the substrate. Furthermore, since a region having a particularly reduced dislocation density is formed on the exposed region of the substrate except for the central portion, the element is located in the region on the exposed region of the substrate except for the central portion on the exposed region of the substrate. It is preferable to form a region (light emitting portion).

In the above description, the semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the first to third inventions has been described. The formation method can be applied to the manufacture of semiconductor devices other than the semiconductor laser device, for example, semiconductor light emitting devices such as light emitting diodes, light receiving devices such as photodiodes, and electronic devices such as transistors.

In the first to sixth inventions, each layer is made of Ga.
N (gallium nitride), AlN (aluminum nitride), I
III- such as nN (indium nitride), BN (boron nitride) or TlN (thallium nitride) or a mixed crystal thereof;
III-type semiconductors such as group V nitride semiconductors and mixed crystals containing at least one of As, P and Sb in these mixed crystals;
What is necessary is just to consist of a group V nitride semiconductor.

In the second, third, fifth and sixth inventions, the semiconductor may have a wurtzite type crystal structure or a zinc blende type crystal structure.

[Brief description of the drawings]

FIG. 1 is a schematic process sectional view showing a method for forming a nitride semiconductor according to an embodiment of the first invention.

FIG. 2 is a schematic process sectional view showing a method for forming a nitride-based semiconductor according to one embodiment of the first invention.

FIG. 3 is a schematic process sectional view showing a method for forming a nitride semiconductor according to another embodiment of the first invention.

FIG. 4 is a schematic process sectional view showing a method of forming a nitride-based semiconductor according to one embodiment of the second invention.

FIG. 5 is a schematic process sectional view showing a method of forming a nitride-based semiconductor according to one embodiment of the second invention.

FIG. 6 is a view showing another example of the substrate used in the method for forming the nitride-based semiconductor shown in FIGS. 4 and 5;

FIG. 7 is a schematic sectional view showing a step of a method for forming a nitride-based semiconductor according to another embodiment of the second invention.

FIG. 8 is a schematic process sectional view showing a method of forming a nitride-based semiconductor according to another embodiment of the second invention.

FIG. 9 is a schematic process sectional view showing a method for forming a nitride-based semiconductor according to one embodiment of the third invention.

10 is a diagram showing a preferred range of a width w of a buffer layer to be etched and a width b of a remaining buffer layer in the embodiment of FIG. 9;

FIG. 11 is a schematic perspective view showing a semiconductor laser device according to an example of the fourth invention.

FIG. 12 is a schematic perspective view showing a semiconductor laser device according to another embodiment of the fourth invention.

FIG. 13 is a schematic process sectional view showing a conventional method of forming a nitride-based semiconductor using selective lateral growth.

[Explanation of symbols]

 1,11,21,31,51,201 Sapphire substrate 2,12,42,52,52a AlGaN buffer layer 4,4a first GaN layer 5,5a second GaN layer 13,43,53 GaN layer 104 n-GaN contact layer 105 n-AlGaInN crack prevention layer 106 n-AlGaN second cladding layer 107 n-GaN first cladding layer 108 MQW light emitting layer 109 p-GaN first cladding layer 110 p-AlGaN second cladding layer 111 n-GaN current confinement layer 112 p-GaN contact layer 500,501 Semiconductor laser device

Claims (24)

[Claims] A first nitride-based semiconductor layer is grown on a C-plane of the substrate, and a surface of the first nitride-based semiconductor layer inclined at a predetermined angle from the C-plane in a predetermined direction is exposed; Growing a second nitride-based semiconductor layer closer to a single crystal than the first nitride-based semiconductor layer on the inclined surface of the first nitride-based semiconductor layer. A method for forming a semiconductor. 2. The nitride according to claim 1, wherein the surface of the first nitride-based semiconductor layer is polished to expose a surface inclined at a predetermined angle from the C-plane in a predetermined direction. Method of forming a system semiconductor. 3. The nitride-based semiconductor according to claim 1, wherein a surface inclined at a predetermined angle from said C-plane in a predetermined direction is exposed in a process of growing said first nitride-based semiconductor layer. Formation method. 4. A method for forming a nitride-based semiconductor on which a nitride-based semiconductor layer is grown on a semiconductor substrate, wherein the semiconductor substrate comprises a group IV semiconductor, a group IV-IV semiconductor, or a group II-VI semiconductor. Forming a concave-convex pattern on a surface of the semiconductor substrate, and growing the nitride-based semiconductor layer on the concave-convex pattern. 5. A method of forming a nitride-based semiconductor in which a nitride-based semiconductor layer is grown on a semiconductor substrate, wherein the semiconductor substrate has a lattice constant different from that of the nitride-based semiconductor layer. A method of forming a nitride-based semiconductor, comprising: forming a concavo-convex pattern on a surface of the semiconductor substrate; and growing the nitride-based semiconductor layer on the concavo-convex pattern. 6. A method for forming a nitride-based semiconductor on which a nitride-based semiconductor layer is grown on an insulator substrate, wherein an uneven pattern is formed on a surface of the insulator substrate, and the nitride-based semiconductor is formed on the uneven pattern. A method for forming a nitride-based semiconductor, comprising growing a layer. 7. An uneven pattern is formed on a surface of a substrate, a buffer layer is grown on the uneven pattern, and a nitride-based semiconductor layer is grown on the uneven pattern and the buffer layer until the surface is substantially flat. A method for forming a nitride semiconductor. 8. The method according to claim 5, wherein the concave / convex pattern has concave portions and convex portions extending in a stripe shape.
8. The method for forming a nitride-based semiconductor according to any one of claims 1 to 7. 9. The method for forming a nitride-based semiconductor according to claim 5, wherein said concave / convex pattern has a plurality of concave portions or convex portions two-dimensionally dispersed. 10. The method according to claim 5, wherein the uneven pattern has a step-like step. 11. A method for forming a nitride-based semiconductor on which a nitride-based semiconductor layer is grown on a semiconductor substrate, wherein the semiconductor substrate comprises a group IV semiconductor, a group IV-IV semiconductor, or a group II-VI semiconductor.
A plurality of buffer layers having a width Y dispersedly at intervals X on the semiconductor substrate by etching, wherein the interval X [μm] and the width Y [μm] are Y [μm] ≦ −X [μm] +40 [μm] and Y [μ
m] ≧ 1 [μm] and X [μm] ≧ 1 [μm], and a nitride-based semiconductor layer is formed on the semiconductor substrate and the plurality of buffer layers. Method of forming a system semiconductor. 12. A method of forming a nitride-based semiconductor in which a nitride-based semiconductor layer is grown on a semiconductor substrate, wherein the semiconductor substrate has a lattice constant different from that of the nitride-based semiconductor layer. A semiconductor substrate consisting of
A plurality of buffer layers having a width Y are formed on the semiconductor substrate by etching at a distance X, and the distance X [μm] and the width Y [μm] are Y [μm] ≦ −X [μm] +40 [μ].
m] and Y [μm] ≧ 1 [μm] and X [μm] ≧ 1
A nitride semiconductor layer that satisfies the relationship of [μm] and forms a nitride semiconductor layer on the semiconductor substrate and the plurality of buffer layers. 13. A method for forming a nitride semiconductor in which a nitride semiconductor layer is grown on an insulator substrate, wherein a plurality of buffer layers having a width Y are formed dispersively at an interval X by etching on the insulator substrate. , Interval X [μm] and width Y [μ
m] is Y [μm] ≦ −X [μm] +40 [μm] and Y
A nitride semiconductor layer is formed on the insulating substrate and the plurality of buffer layers, satisfying a relationship of [μm] ≧ 1 [μm] and X [μm] ≧ 1 [μm]. A method for forming a nitride-based semiconductor. 14. The method according to claim 11, wherein the plurality of buffer layers are arranged in a stripe pattern. 15. The method according to claim 11, wherein the plurality of buffer layers are two-dimensionally dispersed. 16. A first nitride-based semiconductor layer is formed on a C-plane of a substrate, and the first nitride-based semiconductor layer is formed on a plane inclined at a predetermined angle in a predetermined direction from the C-plane of the first nitride-based semiconductor layer. Forming a second nitride-based semiconductor layer closer to a single crystal than the first nitride-based semiconductor layer; and forming a nitride-based semiconductor layer including an element region on the second nitride-based semiconductor layer. A nitride-based semiconductor device. 17. A nitride semiconductor device having a nitride semiconductor layer formed on a semiconductor substrate, wherein the semiconductor substrate is a semiconductor substrate made of a group IV semiconductor, a group IV-IV semiconductor, or a group II-IV semiconductor. A nitride-based semiconductor device, wherein an uneven pattern is formed on a surface of the semiconductor substrate, and a nitride-based semiconductor layer including an element region is formed on the uneven pattern. 18. A nitride semiconductor device in which a nitride semiconductor layer is formed on a semiconductor substrate, wherein the semiconductor substrate is made of a III-V semiconductor having a lattice constant different from that of the nitride semiconductor layer. A nitride semiconductor device comprising: a semiconductor substrate formed by forming an uneven pattern on a surface of the semiconductor substrate; and a nitride semiconductor layer including an element region formed on the uneven pattern. 19. A nitride semiconductor device in which a nitride semiconductor layer is formed on an insulator substrate, wherein a nitride pattern is formed on the surface of the insulator substrate, and includes an element region on the uneven pattern. A nitride-based semiconductor device having a base-semiconductor layer formed thereon. 20. A first nitride having an uneven pattern formed on a surface of a substrate, a buffer layer formed on the uneven pattern, and having a substantially flat surface at least partially on the uneven pattern and the buffer layer. Wherein a nitride-based semiconductor layer is formed, and a second nitride-based semiconductor layer including an element region is formed on the flat surface of the first nitride-based semiconductor layer. . 21. The nitride according to claim 17, wherein a second nitride-based semiconductor layer including the element region is formed in a region other than the center of the concave portion of the concave-convex pattern. Material semiconductor element. 22. A nitride-based semiconductor device having a nitride-based semiconductor layer formed on a semiconductor substrate, wherein the semiconductor substrate is a semiconductor substrate made of a group IV semiconductor, a group IV-IV semiconductor, or a group II-VI semiconductor. And an interval X on the semiconductor substrate.
A plurality of buffer layers having a width Y are formed in a distributed manner,
[Μm] and width Y [μm] are Y [μm] ≦ −X [μ
m] +40 [μm] and Y [μm] ≧ 1 [μm] and X
A nitride semiconductor device satisfying a relationship of [μm] ≧ 1 [μm], wherein a nitride semiconductor layer is formed on the semiconductor substrate and the plurality of buffer layers. 23. In a nitride-based semiconductor device having a nitride-based semiconductor layer formed on a semiconductor substrate, the semiconductor substrate is made of a III-V semiconductor having a lattice constant different from that of the nitride-based semiconductor layer. A plurality of buffer layers having a width Y are formed on the semiconductor substrate in a distributed manner at intervals X, and the interval X [μm] and the width Y [μm] are Y
[Μm] ≦ −X [μm] +40 [μm] and Y [μm]
≧ 1 [μm] and X [μm] ≧ 1 [μm], and a nitride-based semiconductor layer is formed on the semiconductor substrate and the plurality of buffer layers. Semiconductor element. 24. In a nitride-based semiconductor device having a nitride-based semiconductor layer formed on an insulator substrate, a buffer layer having a width Y is formed dispersively at intervals X on the insulator substrate substrate. [Μm] and width Y [μm] are Y [μm] ≦
−X [μm] +40 [μm] and Y [μm] ≧ 1 [μ
m] and X [μm] ≧ 1 [μm], and a nitride-based semiconductor layer is formed on the insulating substrate and on the plurality of buffer layers. .