JPH11135832A - Gallium nitride group compound semiconductor and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve element characteristics and manufacturing efficiency. SOLUTION: A layer 5 composed of Al0.15 Ga0.85 N is formed on a silicon substrate 1, and a layer 6 composed of GaN is formed on the layer 5. A third layer is constituted of the layer 5 and the layer 6. On the layer 6, a first layer 2 of the film thickness of about 2,000 Å composed of SiO2 is formed in a stripe shape or a grating shape. A second layer 3 composed of GaN is grown in the upper region A of the first layer 2 and on the exposed part B of the layer 6. At the time, GaN is grown in a direction vertical to a surface with GaN at the exposed part B of the layer 6 as a core. Then, in the upper region A of the first layer 2, with GaN grown on the exposed part B of the layer 6 as the core, GaN is epitaxially grown in a horizontal direction. In this manner, since GaN is epitaxially grown both in the vertical direction and the horizontal direction with GaN as the core, the gallium nitride group compound semiconductor of non dislocation is obtained in a horizontal directional growth region which is the upper region A of the first layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compound represented by the general formula: Al _x Ga _y In
_{The present} invention relates to a gallium nitride-based compound semiconductor of _1-xy N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and a method of manufacturing the same. In particular, the present invention relates to a substrate using silicon (Si).

[0002]

2. Description of the Related Art Gallium nitride-based compound semiconductors are direct-transition semiconductors whose emission spectrum covers a wide range from ultraviolet to red, and include light-emitting diodes (LEDs) and laser diodes.
(LD) and the like. This gallium nitride-based compound semiconductor is usually formed on sapphire.

[0003]

However, according to the prior art, when a gallium nitride-based compound semiconductor is formed on a sapphire substrate, cracks and warpage occur in the semiconductor layer due to a difference in thermal expansion coefficient between sapphire and the gallium nitride-based compound semiconductor. Occurs, and dislocation occurs due to a misfoot, which causes a problem that device characteristics are not good. further,
Since sapphire is insulative, it is necessary to form both electrodes on the same surface side with respect to the substrate, and therefore, it is necessary to etch up to the n layer on the side close to the substrate, so that the production efficiency is not good There is a problem. Also, since both electrodes are formed on the same surface side, the element size increases. In addition, wire bonding is required for both electrodes, and a current path in the lateral direction is formed in the n-layer, and the current path becomes longer. In addition, since the substrate and the semiconductor layer are made of different materials, it is difficult to satisfactorily cleave the laser diode.

Accordingly, an object of the present invention is to provide a gallium nitride-based semiconductor layer formed on a silicon substrate to improve the device characteristics and realize an efficient manufacturing method in view of the above problems.

[0005]

According to the first aspect of the present invention, there is provided a silicon (Si) substrate, and silicon exposed portions are scattered on the silicon substrate. And a first layer in which a gallium nitride-based compound semiconductor is not epitaxially grown thereon, and an exposed portion of silicon not covered with the first layer. And a second layer made of a gallium nitride-based compound semiconductor formed by epitaxially growing in the lateral direction above the first layer.

[0006] The term "horizontal direction" used herein means the plane direction of the substrate. As a result, the second layer made of the gallium nitride-based compound semiconductor does not epitaxially grow on the first layer, and the layer grown from the exposed portion of the silicon substrate grows laterally on the first layer. Is done. As a result, dislocations due to misfit between the silicon substrate and the gallium nitride-based compound semiconductor grow only in the vertical direction and do not grow in the horizontal direction. Therefore, the crystallinity of the gallium nitride-based compound semiconductor on the first layer is improved.
Further, since the first layer and the gallium nitride-based compound semiconductor thereover are not chemically bonded, warpage of the second layer is prevented and stress strain is suppressed from entering the layer.

[0007] According to the means of claim 2, silicon
An (Si) substrate, a third layer made of a gallium nitride-based compound semiconductor formed on a silicon substrate, and a third layer formed on the third layer and having an exposed portion of the third layer scattered. Nuclei are formed in a first layer on which a gallium nitride-based compound semiconductor is not epitaxially grown and an exposed portion of a third layer which is not covered with the first layer. And a second layer made of a gallium nitride-based compound semiconductor formed by epitaxial growth in the lateral direction above the first layer.

According to this structure, the second layer is made of a gallium nitride-based compound semiconductor, with the exposed portion of the third layer made of the gallium nitride-based compound semiconductor as a nucleus. Two layers are formed. As a result of using a semiconductor of the same kind as the semiconductor of the second layer to be grown instead of silicon as the nucleus for crystal growth, the crystallinity of the second layer is further improved.

A third aspect of the present invention is that the first layer is made of silicon dioxide (SiO ₂ ). In this case, the second layer is made of a gallium nitride-based compound semiconductor containing no Al, so that the second layer has good crystallinity by lateral epitaxial growth without epitaxial growth on the first layer. Obtainable.

The invention according to claim 4 is characterized in that the first layer is made of a metal having a high melting point or amorphous silicon (Si). Since the first layer has conductivity, by providing conductivity to the silicon substrate, it is possible to allow a current to flow uniformly between the second layer and the silicon substrate in a direction perpendicular to the plane. Therefore, the electrodes of the element can be formed on both end surfaces. Incidentally, the metal having a high melting point is a metal having a melting point of 2000 ° C. or more, for example, Nb, Mo, Ru, Hf, Ta, W
Is raised.

[0011] According to a fifth aspect of the present invention, the third layer is made of Al
_This is a two-layer structure in which a layer made of GaN is formed on a layer made of xGa ₁ -xN (0 ≦ x ≦ 1). According to this structure,
If GaN is used as the second layer, GaN can be grown using GaN as a nucleus.
Can be obtained.

[0012] The invention of claim 6 is the method of manufacturing a semiconductor according to claim 1, and the invention of claim 7 is the method of manufacturing the semiconductor of claim 2. According to this method, a gallium nitride-based compound semiconductor having good quality can be obtained. Claim 8,
9 and 10 have the same effects as in claims 3, 4, and 5.
An eleventh aspect is characterized in that at least the silicon substrate among the silicon substrate, the third layer, and the first layer is removed to obtain a wafer composed of the second layer. Thus, a substrate of a single crystal gallium nitride-based compound semiconductor having good crystallinity can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. (First Embodiment) FIG. 1 is a schematic view showing a cross-sectional structure of a gallium nitride-based compound semiconductor according to a first embodiment of the present invention. On the silicon substrate 1, a film thickness of about 2000 made of SiO ₂
The first layer 2 of Å is formed in a stripe shape (FIG. 1B) or a lattice shape (FIG. 1C). A second layer 3 made of GaN and having a thickness of about 10 μm is formed on the exposed region B except the first layer 2 on the silicon substrate 1 and on the first layer 2.

Next, a method of manufacturing the GaN-based compound semiconductor will be described. This semiconductor was manufactured by a sputtering method and a metal organic chemical vapor deposition method (hereinafter abbreviated as "MOVPE"). The gas used in MOVPE was ammonia (N
H ₃ ), carrier gas (H ₂ , N ₂ ), trimethylgallium (Ga
(CH ₃ ) ₃ ) (hereinafter referred to as “TMG”).

First, an n-silicon substrate having a (111) plane, a (100) plane, or a (110) plane as a main surface, which is washed with a hydrofluoric acid solution (HF: H ₂ O = 1: 1). 1 is mounted on a susceptor placed in the reaction chamber of the MOVPE apparatus. Next, flow H ₂ at normal pressure at 2
The substrate 1 was baked at a temperature of 1150 ° C. while flowing into the reaction chamber at liter / minute for about 10 minutes. Next, a first layer 2 made of SiO _{2 is formed} on the substrate 1 by sputtering to a thickness of about 2000 ° and a width a.
Was formed in a stripe shape (FIG. 1 (b)) or a lattice shape (FIG. 1 (c)) in which the distance b between the exposed portions B was approximately 5 μm.

Next, the temperature of the substrate 1 is set to 600 by the MOVPE method.
℃ To 20Liter / min N ₂ or H ₂ and the NH ₃ 10liter / min, TM
G was supplied at 1.0 × 10 ⁻⁴ mol / min, and silane diluted to 0.86 ppm with H ₂ gas was supplied at 20 × 10 ⁻⁸ mol / min.
The second layer 3 was obtained by forming GaN of μm.
At this time, GaN grows perpendicularly to the surface with the silicon in the exposed portion B of the silicon substrate 1 as a nucleus. And the first layer 2
In the upper region A, GaN is epitaxially grown in the lateral direction, that is, in the plane direction of the silicon substrate 1 with GaN grown on the exposed portion B of the silicon substrate 1 as a nucleus. This second
In the layer 3, dislocations occur in the vertical direction only in the exposed portions B of the silicon substrate 1, and no dislocations occur in the upper region A of the first layer 2 because of lateral epitaxial growth. By increasing the area of the first layer 2 as compared with the area of the exposed portion B of the silicon substrate 1, GaN having good crystallinity over a wide area
The second layer 3 made of Further, since the first layer 2 and the GaN thereon are not chemically bonded, the warp and the stress strain of the second layer 3 can be extremely reduced.

In the above embodiment, the width a of the first layer 2 formed in a stripe or a lattice is set to about 5 μm, but when the width a of the first layer 2 exceeds 10 μm, the width a in the horizontal direction is increased. If the growth is required for a long time and the width a of the first layer 2 is less than 1 μm, it becomes difficult to remove the SiO ₂ film later with acetone or the like, so that the range is preferably 1 to 10 μm. In the above embodiment, the distance b between the exposed portions B of the silicon substrate 1 is 5 μm.
However, when the distance b between the exposed portions B exceeds 10 μm, the probability of dislocation increases, and when the distance b between the exposed portions B is less than 1 μm, it becomes difficult to form a good GaN film. A range of 10 μm is good. In addition, the width ratio a / b is preferably 1 to 10 from the viewpoint of the crystallinity of the second layer 3.

(Second Embodiment) In the first embodiment described above, the first layer 2 is formed on the silicon substrate 1, but this embodiment is characterized in that the gallium nitride-based compound semiconductor is formed on the silicon substrate 1. Is provided, a first layer is formed in an island shape on the third layer, and a gallium nitride-based compound semiconductor is formed thereon.

FIG. 2 is a schematic view showing a sectional structure of a gallium nitride-based compound semiconductor according to a second embodiment of the present invention. A third layer 5 made of Al _0.15 Ga _0.85 N and having a thickness of about 1000 ° is formed on the silicon substrate 1.
A first layer 2 made of SiO ₂ and having a thickness of about 2000 ° is formed in a stripe shape or a lattice shape similarly to the first embodiment.
Also, the exposed portion B of the third layer 5 and the upper region A of the first layer 2
Is formed with a second layer 3 made of GaN and having a thickness of about 10 μm.

Next, a method of manufacturing the GaN-based compound semiconductor will be described. Up to the point where the silicon substrate 1 is baked, it is the same as the first embodiment. Thereafter, the temperature of the substrate 1 is maintained at 1150 ° C., and N ₂ or H ₂ is set at 10 liter / min.
NH ₃ at 10 liter / min, TMG at 1.0 × 10 ^-4 mol / min, trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMA”)
1.0 × 10 ⁻⁵ mol / min, silane diluted to 0.86 ppm by H ₂ gas is supplied at 20 × 10 ⁻⁸ mol / min, and the film thickness is about 1000 Å.
A third layer 5 made of Al _0.15 Ga _0.85 N having a Si concentration of 1.0 × 10 ¹⁸ / cm ³ was formed.

Next, as in the first embodiment, a first layer 2 made of SiO _{2 is formed} on the third layer 5 to a thickness of about 2000 ° and a width a of about 5 mm.
μm, and the distance b between the exposed portions B of the third layer 5 is about 5 μm in the form of a stripe or grid. Next, in the same manner as in the first embodiment, a film thickness of about 1 mm is formed on the exposed portions B of the first layer 2 and the third layer 5.
A second layer 3 of 10 μm GaN is formed. At this time, GaN grows in the direction perpendicular to the surface with Al _0.15 Ga _0.85 N in the exposed portion B of the third layer 5 as a nucleus. Then, in the upper region A of the first layer 2, GaN is epitaxially grown in the lateral direction with GaN grown on the exposed portion B of the third layer 5 as a nucleus. Thus, the second layer 3 made of GaN is formed on the exposed portions of the first layer 2 and the third layer 5.

As indicated above, GaN is Al _0.15 Ga
Since GaN is grown first with _0.85 N as a nucleus, the crystallinity of GaN is higher than in the case of using Si as a nucleus. Further, by removing the silicon substrate 1 or the region C from the silicon substrate 1 to the first layer 2 by polishing or etching, a dislocation-free gallium nitride-based compound semiconductor substrate can be obtained by the second layer 3. Can be.

In this embodiment, the composition of the third layer 5 is Al
_0.15 Ga _0.85 N, but the general formula Al _x Ga _y In
_A gallium nitride-based compound semiconductor of _1-xy N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) can be used. For epitaxial growth on the silicon substrate 1, Al _x Ga _1-x N
(0 ≦ x ≦ 1) (including AlN) is desirable. The second layer 3 has a general formula of Al _x Ga _y In _1-xy N (0 ≦ x
≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) gallium nitride-based compound semiconductor can be used, and the same composition ratio as that of the third layer 5 or a different composition ratio can be used. good. Further, in the present embodiment, the thickness of the third layer 5 is set to about 1000
If the film thickness of the third layer 5 is less than 500 °, the growth of the second layer in the lateral direction is deteriorated, so that the film thickness of the third layer 5 is preferably 500 ° or more.

(Third Embodiment) In the second embodiment described above, the third layer 5 is constituted by a single layer.
Has a two-layer structure. FIG. 3 shows a third embodiment of the present invention.
FIG. 1 is a schematic diagram illustrating a cross-sectional configuration of a gallium nitride-based compound semiconductor according to an example. Al _0.15 on silicon substrate 1
A layer 5 made of Ga _0.85 N and having a thickness of about 1000 ° is formed, and a layer 6 made of GaN and having a thickness of about 1000 ° is formed on the layer 5. The layer 5 and the layer 6 constitute a third layer. On the layer 6, a first layer 2 made of SiO ₂ and having a thickness of about 2000 ° is formed in a stripe shape or a lattice shape as in the above-described embodiment. On the layer 6 and the first layer 2, a film thickness of about 10
A second layer 3 of μm is formed.

Next, a method of manufacturing the GaN-based compound semiconductor will be described. Bake the substrate 1 and place it on the substrate 1
The process is the same as that of the second embodiment up to the point where the layer 5 is formed by the MOVPE method. After the formation of the layer 5, the temperature of the substrate 1 is set to 1100 ° C. on the layer 5 by MOVPE, and N ₂ or H ₂ is added at 20 liter / min.
NH ₃ was supplied at 10 liter / min, TMG was supplied at 2.0 × 10 ⁻⁴ mol / min, and silane diluted to 0.86 ppm with H ₂ gas was supplied at 20 × 10 ⁻⁸ mol / min to form GaN. A layer 6 of about 1000 ° is obtained.

Next, as in the first and second embodiments, the first layer 2 made of SiO _{2 is formed} on the third layer 5 to a thickness of about 2000 Å and a width a.
Are formed in a striped or lattice shape with a distance b of about 5 μm and an interval b between exposed portions B of the layer 6 of about 5 μm. Next, a second layer 3 made of GaN having a thickness of about 10 μm is grown on the upper region A of the first layer 2 and the exposed portion B of the layer 6. At this time, GaN grows in a direction perpendicular to the surface with GaN of the exposed portion B of the layer 6 as a nucleus. Then, in the upper region A of the first layer 2, GaN epitaxially grows in the lateral direction with GaN grown on the exposed portion B of the layer 6 as a nucleus. Thus, in this embodiment,
Since GaN is epitaxially grown in the vertical and horizontal directions with GaN as a nucleus, GaN having higher crystallinity than that of the above embodiment can be obtained.

In this embodiment, the second layer 3 is similarly removed by polishing or etching the silicon substrate 1 or the portion C from the silicon substrate 1 to the first layer 2.
And a dislocation-free GaN substrate composed of Also,
Although the layer 6 and the second layer 3 are made of GaN, the layer 6 and the second layer 3
And the general formula Al _x Ga _y In _1-xy N (0 ≤ x ≤ 1,
A gallium nitride-based compound semiconductor satisfying 0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) may be used. However, when SiO ₂ is used for the first layer 2, a gallium nitride-based compound semiconductor containing no Al is preferably used. Of course, the composition ratio between the layer 6 and the second layer 3 may be changed.

In all the above embodiments, the second layer 3 is made of Ga.
Although N 2 was used, InGaN having an arbitrary composition ratio may be used. Al
The gallium nitride-based compound semiconductor containing Al grows on the SiO ₂ layer, so that it is preferable not to contain Al. However, instead of SiO ₂ , the first layer 2 formed in a stripe or lattice may be made of a metal having a high melting point such as tungsten (W) or amorphous Si. Thus, the first layer 2
Is composed of metal or amorphous Si, the first layer 2
Since the current flows through the GaN compound semiconductor, it is possible to more uniformly flow the current uniformly in the thickness direction of the GaN compound semiconductor. tungsten
(W) high melting point metal or amorphous Si, when using the general formula Al _x Ga _y In _1-xy N (0 ≤ x ≤
The gallium nitride-based compound semiconductor of 1,0 ≤ y ≤ 1,0 ≤ x + y ≤ 1) does not epitaxially grow thereon, so the general formula
The _{Al x Ga y In 1-xy} N can be used as the second layer. Further, in all of the above embodiments, each layer may be formed after forming a buffer layer by low-temperature growth of a gallium nitride-based compound semiconductor on a substrate. In all of the above embodiments, the MOVPE method was performed in a normal pressure atmosphere, but may be performed under reduced pressure growth. Further, it may be performed under a combination of normal pressure and reduced pressure.

The GaN-based compound semiconductor obtained by the present invention is
The present invention can be used not only for light emitting elements of LEDs and LDs but also for light receiving elements and electronic devices.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a gallium nitride-based compound semiconductor according to a first specific example of the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of a gallium nitride-based compound semiconductor according to a second specific example of the present invention.

FIG. 3 is a schematic sectional view showing the structure of a gallium nitride-based compound semiconductor according to a third specific example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 1st layer 3 2nd layer 5 3rd layer

Claims (11)

[Claims] 1. A silicon (Si) substrate, and a gallium nitride-based compound semiconductor is formed on the silicon substrate in an island state such as a dot, stripe, or lattice so that exposed portions of silicon are scattered. A first layer that is not epitaxially grown thereon and an exposed portion of silicon that is not covered by the first layer are formed as nuclei by epitaxial growth, and an upper portion of the first layer is formed by laterally epitaxially growing. A second layer comprising a gallium nitride (GaN) -based compound semiconductor. 2. A silicon (Si) substrate, a third layer made of a gallium nitride-based compound semiconductor formed on the silicon substrate, and a third layer formed on the third layer, A first layer in which a gallium nitride-based compound semiconductor is not epitaxially grown thereon is formed in a dot-like, stripe-like, or lattice-like island state such that the exposed portions are scattered, and the first layer covers the gallium nitride-based compound semiconductor. And a second layer made of a gallium nitride-based compound semiconductor formed by epitaxially growing in a lateral direction above the first layer, with the exposed portion of the third layer not serving as a nucleus. A gallium nitride-based compound semiconductor, characterized in that: 3. The method according to claim 1, wherein the first layer is made of silicon dioxide (SiO ₂ ).
The gallium nitride-based compound semiconductor according to claim 1, wherein the compound semiconductor comprises: 4. The gallium nitride-based compound semiconductor according to claim 1, wherein the first layer is made of a metal having a high melting point or amorphous silicon (Si). 5. The method according to claim 1, wherein the third layer has a two-layer structure in which a layer made of GaN is formed on a layer made of Al _x Ga ₁ -xN (0 ≦ x ≦ 1). Item 3. A gallium nitride-based compound semiconductor according to item 2. 6. A method for manufacturing a gallium nitride-based compound semiconductor on a silicon (Si) substrate, comprising: an island state such as a dot-like, stripe-like, or lattice-like state such that exposed portions of silicon are scattered on the silicon substrate. Forming a first layer on which the gallium nitride-based compound semiconductor does not epitaxially grow, and epitaxially growing the exposed portion of the syringe not covered with the first layer as a nucleus; Forming a second layer of a gallium nitride-based compound semiconductor by epitaxially growing in a lateral direction. 7. A method for manufacturing a gallium nitride-based compound semiconductor on a silicon (Si) substrate, comprising: forming a third layer made of a gallium nitride-based compound semiconductor on the silicon substrate; In an island state such as a dot shape, a stripe shape, or a grid shape so that the exposed portions of the third layer are scattered,
Forming a first layer on which the gallium nitride-based compound semiconductor does not epitaxially grow, and epitaxially growing the exposed portion of the third layer not covered with the first layer as a nucleus; A method for manufacturing a gallium nitride-based compound semiconductor, comprising forming a second layer made of a gallium nitride-based compound semiconductor by epitaxially growing in a lateral direction at an upper portion. 8. The method according to claim 1, wherein the first layer is made of silicon dioxide (SiO ₂ ).
The method for producing a gallium nitride-based compound semiconductor according to claim 6, wherein the method comprises: 9. The gallium nitride-based compound semiconductor according to claim 6, wherein the first layer is made of a metal having a high melting point or amorphous silicon (Si). Production method. 10. The third layer is composed of Al _x Ga ₁ -xN (0 ≦ x ≦ 1).
8. The method for producing a gallium nitride-based compound semiconductor according to claim 7, wherein a two-layer structure in which a layer made of GaN is formed on a layer made of GaN. 11. A wafer made of a gallium nitride-based compound semiconductor by removing at least a silicon substrate among the silicon substrate, the third layer, and the first layer. Any one of claim 10
13. The method for producing a gallium nitride-based compound semiconductor according to the above item.