JP2000091253A - Method of producing gallium nitride based compound semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a semiconductor layer without crack and dislocation by etching in the shape of an island with a dot-shape, a stripe-shape or a grid-shape and laterally growing a second gallium nitride based compound semiconductor on an exposed surface of a substrate using an island-shaped first gallium nitride based compound semiconductor as core. SOLUTION: An SiO2 layer is etched in a specified form by photolithography. Next an Al0.15Ga0.85N layer 2 is dry-etched using the SiO2 layer with the specified shape as mask. A GaN layer 3 is epitaxially grown on a substrate 1 by MOVPE method. At that time, the GaN layer 3 is epitaxially grown on an Al0.15Ga0.85N layer 2 using the Al0.15Ga0.85N layer 2 as core. But the GaN layer dose not epitaxially grow on an exposed region A of a silicon substrate 1. The GaN is epitaxially grown on the exposed region A of the silicon substrate 1 in the direction of the surface of the silicon substrate 1 using the GaN grown on the Al0.15Ga0.85N layer 2 as core.

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, it relates to a method using lateral epitaxial growth (ELO) on a substrate.

[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, in the prior art, when a gallium nitride-based compound semiconductor is formed on a sapphire substrate, cracks and warpages occur in the semiconductor layer due to the 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.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a gallium nitride-based semiconductor layer free from cracks and dislocations in view of the above problems, thereby improving device characteristics and realizing an efficient manufacturing method. .

[0005]

In order to solve the above-mentioned problems, according to the present invention, a first gallium nitride-based compound semiconductor is grown on a substrate, and then the first gallium nitride-based compound semiconductor is grown. Gallium nitride-based compound semiconductor is etched into islands such as dots, stripes, or lattices so that the exposed portions of the substrate are scattered, and then the first gallium nitride-based compound semiconductor in the islands is nucleated. A second gallium nitride-based compound semiconductor that grows as a nucleus but does not epitaxially grow with the exposed portion of the substrate as a nucleus is grown, and the exposed surface of the substrate is formed by lateral growth, and Forming a device layer made of a gallium nitride-based compound semiconductor on the substrate.

[0006] The term "horizontal direction" used herein means the plane direction of the substrate. As a result, the second gallium nitride-based compound semiconductor does not grow on the exposed portion of the substrate, but also grows three-dimensionally and immediately in the plane direction on the first gallium nitride-based compound semiconductor. Grows uniformly. As a result, dislocations due to misfit between the substrate and the gallium nitride-based compound semiconductor grow in the vertical direction and do not grow in the horizontal direction. Therefore, the threading dislocations in the vertical direction of the second gallium nitride-based compound semiconductor on the exposed portion of the substrate are eliminated, and threading dislocations in the vertical direction remain only in the portion above the first gallium nitride-based compound semiconductor. As a result, the areal density of threading dislocations in the vertical direction of the second gallium nitride-based compound semiconductor is extremely reduced. Therefore, the crystallinity of the second gallium nitride-based compound semiconductor is improved. Further, since the exposed portion of the substrate and the second gallium nitride-based compound semiconductor thereon are not chemically bonded, warpage of the second gallium nitride-based compound semiconductor is prevented and stress distortion is applied to the semiconductor. The entry is suppressed.

According to a second aspect of the present invention, a buffer layer is formed on a substrate, a first gallium nitride compound semiconductor is grown on the buffer layer, and thereafter, the buffer layer and the first gallium nitride compound semiconductor are grown. Is etched into islands such as dots, stripes, or grids so that the exposed portions of the substrate are scattered, and then grown using the first gallium nitride-based compound semiconductor in the islands as a nucleus. A method for manufacturing a gallium nitride-based compound semiconductor, characterized in that a second gallium nitride-based compound semiconductor that does not epitaxially grow is grown with the exposed portion as a nucleus, and that the exposed surface of the substrate is formed by lateral growth.

According to a third aspect of the present invention, the substrate is made of sapphire, silicon, or silicon carbide. According to a fourth aspect of the present invention, the buffer layer includes AlGaN having an arbitrary composition ratio,
It is characterized by being AlGaInN having an arbitrary composition ratio. Claim 5
According to the invention, the first gallium nitride-based compound semiconductor and the second gallium nitride-based compound semiconductor have the same composition ratio. The invention according to claim 6 is characterized in that the thickness of the first gallium nitride-based compound semiconductor is from 500 to 2000 degrees. The invention according to claim 7 is characterized in that the exposed portion is wider than the first gallium nitride-based compound semiconductor left after etching.

In the above invention, sapphire, silicon, or silicon carbide can be used for the substrate.
The crystallinity of the second gallium nitride-based compound semiconductor obtained on the substrate can be improved.

In the above invention, the substrate is silicon, the first gallium nitride compound semiconductor formed in an island state is a gallium nitride compound semiconductor containing aluminum,
The gallium nitride-based compound semiconductor may be a gallium nitride-based compound semiconductor containing no aluminum. In this case, the gallium nitride compound semiconductor containing aluminum grows epitaxially on silicon, but the gallium nitride compound semiconductor not containing aluminum does not grow epitaxially on silicon. Therefore,
A first gallium nitride-based compound semiconductor in an island state is formed on a silicon substrate, and thereafter, a second nitride that is epitaxially grown on the first gallium nitride-based compound semiconductor but is not epitaxially grown on an exposed portion of the silicon substrate A gallium-based compound semiconductor can be formed. As a result, the second gallium nitride-based compound semiconductor is epitaxially grown laterally on the exposed portion of the silicon substrate with the first gallium nitride-based compound semiconductor as a nucleus, and the gallium nitride-based compound semiconductor having high crystallinity is obtained. Can be obtained.

[0011]

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, Al _0.15 Ga having a thickness of about 1000
_{The 0.85} N layer (first gallium nitride-based compound semiconductor) 2 is formed in a stripe shape (FIG. 1B) or a lattice shape (FIG. 1C). The exposed region A excluding the layer 2 on the silicon substrate 1 and the upper surface region B of the layer 2 have a thickness of about 10 μm.
An N layer (second gallium nitride-based compound semiconductor) 3 is formed.

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”) and trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMA”).

First, an n-silicon substrate having a (111) plane, a (100) plane, or a (110) plane as a main surface, which has been washed with a hydrofluoric acid-based 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 a flow rate of 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.

Thereafter, the temperature of the substrate 1 is maintained at 1150 ° C.
N ₂ or H ₂ 10 liter / min, NH ₃ 10 liter / min, TMG 1.0
× 10 ^-4 mol / min, trimethyl aluminum (Al (CH ₃ ) ₃ )
(Hereinafter referred to as “TMA”) was supplied at 1.0 × 10 ⁻⁵ mol / min, and silane diluted to 0.86 ppm with H ₂ gas was supplied at 20 × 10 ⁻⁸ mol / min. × 10 ¹⁸ / cm ³ Al _{0.
A 15} Ga _0.85 N layer 2 was formed.

Next, an SiO ₂ layer was uniformly formed on this layer 2 to a thickness of about 2000 ° by sputtering, a resist was applied, and the SiO ₂ layer was etched into a predetermined shape by photolithography. Next, the Al _0.15 Ga _0.85 N layer 2 was dry-etched using the SiO ₂ layer having the predetermined shape as a mask. Thus, the width b of the upper region B of the layer 2 is about 5 μm.
m, and the distance a between the exposed regions A of the substrate 1 was about 5 μm in the form of a stripe (FIG. 1B) or a grid (FIG. 1C).

Next, the temperature of the substrate 1 is set to 1100 by the MOVPE method.
° C and N_TwoOr H_Two20 liter / min, NH _Three10 liter / min, TM
G is 1.0 × 10^-FourMol / min, H_TwoDiluted to 0.86 ppm by gas
20 × 10^-8The film thickness is about 10
A μm GaN layer 3 was epitaxially grown. This and
GaN, Al_0.15Ga_0.85On the N layer 2, this Al_0.15Ga
_0.85Epitaxial growth with N as a nucleus. But,
On the exposed region A of the silicon substrate 1, GaN is epitaxy.
Shall not grow. Then, the exposed region of the silicon substrate 1
In A, Al_0.15Ga_0.85With GaN grown on the N layer 2 as the core
As a result, GaN is oriented in the horizontal direction, that is, in the plane direction of the silicon substrate 1.
Epitaxial growth. This GaN layer 3 is made of Al_0.15
Ga_0.85Dislocations occur in the vertical direction only in the upper region B of the N layer 2,
In the exposed area A of the silicon substrate 1, a lateral epitaxy
Dislocation does not occur because of the thermal growth. Silicon substrate
The area of the exposed area A is_0.15Ga_0.85Upper area of N layer 2
By making it larger than the area of B, over a large area
The GaN layer 3 having good crystallinity can be formed. Ma
Also, the silicon substrate 1 and the GaN thereon are chemically bonded.
Therefore, warpage and stress strain of the GaN layer 3 are extremely large.
Can be reduced.

In the above embodiment, the width a of the exposed region A of the silicon substrate 1 formed in a stripe or lattice is set to about 5 μm. However, when the width a of the exposed region A exceeds 10 μm, the width a in the horizontal direction is increased. If the width a of the exposed region A of the silicon substrate 1 is less than 1 μm, a good Ga
Since it becomes difficult to form an N 2 film, the thickness is preferably in the range of 1 to 10 μm. Although the width b of Al _0.15 Ga _0.85 upper region of the N layer 2 B and 5 [mu] m, the probability of Al _0.15 Ga _0.85 width b of the upper region B of the N layer 2 is more than 10μm and dislocation generation is increased,
When the width “b” of the upper region B is less than 1 μm, nucleation for lateral growth cannot be performed well, and therefore, lateral epitaxial growth with good crystallinity becomes difficult. Therefore,
Desirably, the range is 1 to 10 μm. Further, from the viewpoint of the crystallinity of the layer 3, the width a of the exposed region A of the silicon substrate 1
_0.15 Ga _0.85 N Ratio a / to width b of upper region B of layer 2
b is preferably 1 to 10.

In the above embodiment, a silicon substrate is used.
However, other conductive substrates, sapphire substrates, silicon carbide, etc.
Can be used. If a conductive substrate is used,
Electrodes on the back of the plate and the top layer of the device layer formed on the substrate
To allow current to flow perpendicular to the substrate surface.
Improves current supply efficiency in photodiodes, lasers, etc.
You. In this embodiment, the composition of the layer 2 is changed to Al_0.15Ga_0.85N
Is an arbitrary composition ratio of the general formula Al _xGa_yIn_1-xyN (0 ≤x ≤1,
Gallium nitride-based compound semiconductor with 0 ≤ y ≤ 1,0 ≤ x + y ≤ 1)
Can be used. Epitaxy on silicon substrate 1
Al growth_xGa_1-xN (0 <x ≦ 1) (AlN
Is desirable. The layer 3 has a general formula of an arbitrary composition ratio.
Al_xGa_yIn_1-xyN (0 ≤x ≤1,0 ≤y ≤1,0 ≤x + y ≤1)
Gallium nitride-based compound semiconductor can be used.
The composition ratio may be the same as 2, or may be a different composition ratio.
However, the composition ratio that does not epitaxially grow with the substrate
There is a need to. In this embodiment, the thickness of the layer 2 is set to about 10
However, when the thickness of the layer 2 is large, cracks increase and the layer 2 is thin.
Layer 3 does not grow with layer 2 as a nucleus. Therefore, the thickness of layer 2
It is desirable that the size is 500 to 2000 mm.

(Second Embodiment) In the first embodiment, the second embodiment
Al gallium nitride based compound semiconductor_0.15Ga _0.85
Only one N layer 2 is provided. In the present embodiment, the first
AlGaN as a gallium nitride based compound semiconductor_0.15Ga_0.85N
It is characterized in that it was formed of two layers, a layer 21 and a GaN layer 22 thereon.
Sign.

FIG. 2 is a schematic diagram showing a sectional structure of a gallium nitride-based compound semiconductor according to a second embodiment of the present invention. On the silicon substrate 1, Al _0.15 Ga having a thickness of about 1000
_0.85 N layer 21 is formed, and a thickness of about 1000
A GaN layer 22 is formed. The layer 21 and the layer 22 constitute a first gallium nitride-based compound semiconductor. These layers 21 and 22 are formed in a stripe shape or a lattice shape as in the first embodiment. On the layer 22 and the exposed region A of the silicon substrate 1, a GaN layer 3 having a thickness of about 10 μm is formed.

In the gallium nitride-based compound semiconductor of the second embodiment, the layers 21 and 22 are formed uniformly on the silicon substrate 1 in the first embodiment, and then a predetermined pattern of SiO ₂ layer is used as a mask. , The layer 21 and the layer 22 are formed into a stripe shape or a lattice shape by dry etching as shown in FIG. The subsequent formation of the GaN layer 3 is the same as in the first embodiment.

The process of growing the GaN layer 3 having a thickness of about 10 μm is as follows. GaN is the GaN in the upper region B of the GaN layer 22.
With the nucleus as a nucleus, it grows in the direction perpendicular to the plane. Then, in the exposed region A of the silicon substrate 1, GaN epitaxially grows in the lateral direction with GaN grown on the exposed region B of the layer 22 as a nucleus. Thus, in the present embodiment, GaN is
Since GaN is used as a nucleus for epitaxial growth in both the vertical and horizontal directions, GaN having higher crystallinity than in the first embodiment can be obtained.
Is obtained.

In this embodiment, the layer 22 and the layer 3 are
Although GaN was used, the layer 22 and the layer 3 were formed by the general formula Al having the same composition ratio.
_{x Ga y In 1-xy N} (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) of may be gallium nitride-based compound semiconductor. However, layer 2
Must be a composition ratio that does not cause epitaxial growth with respect to the substrate. When silicon is used for the substrate, a gallium nitride-based compound semiconductor containing no Al is preferably used. Of course, the composition ratio between the layer 22 and the second layer 3 may be changed.

In all the above embodiments, the silicon substrate 1
Or a portion C from the silicon substrate 1 to the layer 2 or the layer 22
Is removed by polishing or etching, whereby a dislocation-free GaN substrate can be obtained. Although GaN is used for the layer 3 in all of the above embodiments, InGaN having an arbitrary composition ratio may be used. Further, a semiconductor layer of another material may be formed on the layer 3. In particular, by further growing a gallium nitride-based compound semiconductor, an element having good characteristics such as a light emitting diode and a laser can be obtained. In all of the above embodiments, an AlGaN buffer layer or an AlGaInN buffer layer having an arbitrary composition ratio may be provided between the substrate 1 and the layer 2 or the layer 22. This buffer layer has a crystal structure such as amorphous or amorphous mixed with microcrystals formed at a temperature lower than the single crystal growth temperature of the layers 2 and 22.

A light emitting diode or a laser having a quantum structure such as SQW or MQW as an element layer can be formed. 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 can be used not only for light-emitting devices such as LEDs and LDs, but also for light-receiving devices and electronic devices.

In the present application, a first gallium nitride-based compound semiconductor is grown on a substrate, and then the first gallium nitride-based compound semiconductor is placed in a dot-like manner so that exposed portions of the substrate are scattered. Is etched in an island state such as a stripe or lattice, and then grown using the first gallium nitride-based compound semiconductor in the island state as a nucleus, but not epitaxially grown using the exposed portion of the substrate as a nucleus. There is also disclosed a method of manufacturing a gallium nitride-based compound semiconductor, which comprises growing a compound semiconductor and forming the exposed surface of the substrate by lateral growth.

[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.

[Explanation of symbols]

_Reference Signs _List 1 silicon substrate 2 Al _0.15 Ga _0.85 N layer (first gallium nitride compound semiconductor) 3 GaN layer (second gallium nitride compound semiconductor) 21 Al _0.15 Ga _0.85 N layer (first gallium nitride compound semiconductor) 22 GaN layer (first gallium nitride compound semiconductor)

Claims (7)

[Claims] A first gallium nitride-based compound semiconductor is grown on a substrate, and then the first gallium nitride-based compound semiconductor is formed into a dot-like, stripe-like, or strip-like shape such that exposed portions of the substrate are scattered. The second gallium nitride-based compound is etched into an island state such as a lattice, and then grown using the first gallium nitride-based compound semiconductor in the island state as a nucleus, but not epitaxially grown using the exposed portion of the substrate as a nucleus. Growing a semiconductor, forming an exposed surface of the substrate by lateral growth, and forming an element layer made of a gallium nitride compound semiconductor on the second gallium nitride compound semiconductor. A method for manufacturing a gallium-based compound semiconductor. 2. A buffer layer is formed on a substrate, a first gallium nitride compound semiconductor is grown on the buffer layer, and then the buffer layer and the first gallium nitride compound semiconductor are formed on the substrate. Etching is performed in an island state such as a dot, a stripe, or a lattice so that the exposed portions are scattered, and then, the first gallium nitride-based compound semiconductor in the island state is grown as a nucleus. A second gallium nitride-based compound semiconductor that does not epitaxially grow with a portion as a nucleus, and the exposed surface of the substrate is formed by lateral growth. 3. The method according to claim 1, wherein the substrate is sapphire, silicon, or
3. The method according to claim 1, wherein the material is silicon carbide.
3. The method for producing a gallium nitride-based compound semiconductor according to item 1. 4. The buffer layer is composed of AlGaN having an arbitrary composition ratio,
The method for producing a gallium nitride-based compound semiconductor according to claim 2 or 3, wherein the composition is AlGaInN having an arbitrary composition ratio. 5. The semiconductor device according to claim 1, wherein said first gallium nitride-based compound semiconductor and said second gallium nitride-based compound semiconductor have the same composition ratio. A method for producing a gallium nitride-based compound semiconductor. 6. The method for manufacturing a gallium nitride-based compound semiconductor according to claim 1, wherein the thickness of the first gallium nitride-based compound semiconductor is from 500 to 2000 degrees. Method. 7. The gallium nitride-based semiconductor device according to claim 1, wherein the exposed portion is wider than the first gallium nitride-based compound semiconductor left after etching. A method for manufacturing a compound semiconductor.