JPH10135140A - Hetero-epitaxial growing method, hetero-epitaxial layer and semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the warping or crack of an epitaxially grown layer and substrate by forming a layer having openings on specified area of the substrate to expose specified parts of the substrate through the openings and selectively hetero-epitaxially growing a semiconductor layer on the exposed parts. SOLUTION: A substrate single crystal 3 uses sapphire. On the exposed surface of the single crystal 3, an SiO2 film 2 is periodically crosswise formed to form a layer having openings through which the sapphire substrate is exposed. An epitaxial crystal layer 4 is selectively grown on the exposed surface of the substrate single crystal 3. After forming electrodes, it is polished and a resist is coated on the epitaxially grown surface as a protective film, and the substrate is scribed from its epitaxially grown surface to form chips, using a diamond scriber. Thus, no crack occurs in the grown epitaxial crystal, and the substrate will not break, making the process easy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heteroepitaxial growth method, a heteroepitaxial layer grown by the method, and a semiconductor light emitting device having the heteroepitaxial layer.

[0002]

2. Description of the Related Art Conventionally, when a material different from that of a substrate is epitaxially grown on the substrate, the epitaxial growth has been conventionally performed only by performing a surface treatment without performing any processing on the substrate.

[0003]

When there is a difference between the coefficient of thermal expansion and the lattice constant between the substrate and the epitaxially grown material, distortion occurs in the epitaxially grown layer and the substrate. Therefore, if the difference between the coefficient of thermal expansion and the lattice constant is large,
The epitaxial growth layer was cracked, the epitaxial growth layer was peeled off, and sometimes the substrate was broken. In addition, the substrate was constantly warped.

[0004] When a group III nitride semiconductor, which is important as a short-wavelength light-emitting element such as blue light or an electronic device for a high-temperature environment, is epitaxially grown, there is no suitable substrate material from the viewpoints of thermal expansion coefficient and lattice constant. For example, if sapphire or silicon carbide (SiC) is used as the substrate, a large number of cracks will be formed in the group III nitride epitaxial growth film grown on the substrate, and the yield of the light emitting device fabrication will be about 40%. In general, when forming a chip, the substrate is polished and thinned after epitaxial growth in order to facilitate separation of individual semiconductor light emitting elements. However, the substrate may be broken when the substrate is polished and separated. To avoid this, when a semiconductor light emitting device is chipped,
After the substrate is polished, the substrate is attached to the polishing jig and cut with a diamond saw from the substrate side, or the substrate attached to the polishing jig is painted with diamond or the like, and then the substrate is removed from the polishing jig. Has been performed. In this case, it is necessary to perform the cutting and the hair drawing when the semiconductor light emitting element isolation region is viewed from the substrate side, and it is impossible to do so unless the substrate is a transparent substrate. If it were not a transparent substrate, the yield of the process would be extremely low.
In addition, the warpage of the substrate has made the photolithography process more difficult.

Further, a group III nitride semiconductor In _1-xy Ga
_x Al _y N layer (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦
In the case of manufacturing a semiconductor light emitting device having a semiconductor layer composed of 1), even if the substrate has cleavage, In _1-xy G
Since a _x Al _y N layer cleaved difficult or no cleavage to, there is a problem of low yield of the chips. On the other hand, when manufacturing a laser, it is necessary that the cleavage plane be a mirror surface, but it is difficult to obtain a mirror surface. Therefore, dry etching is performed to make the cleavage plane a mirror surface, but there is a problem that the etching rate is generally low and the etching throughput is low. Further, the etched surface needs to be perpendicular (90 degrees) to the growth surface, but is generally only about 70 degrees, and has a low effect as a mirror for a laser resonator, which causes an increase in oscillation threshold current. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a heteroepitaxial growth method that does not cause distortion, cracks, and the like in an epitaxial growth layer and a substrate, and a heteroepitaxial growth layer grown by the method. It is to provide a semiconductor light emitting device having the following. Also. Another object of the present invention is to provide an epitaxial growth method capable of manufacturing a semiconductor light emitting device containing a group III nitride semiconductor In _1-xy Ga _x Al _y N at a high yield, and a semiconductor having an epitaxial layer grown by the method. It is to provide a light emitting element.

[0007]

According to a first aspect of the present invention, there is provided a heteroepitaxial growth method for growing a semiconductor layer having a lattice constant different from that of a substrate on a substrate, wherein the semiconductor layer is selectively grown at a predetermined position on the substrate. Forming a layer having an opening for exposing a predetermined portion of the substrate by the opening; and selectively heteroepitaxially growing a semiconductor layer on the surface of the substrate exposed by the opening. It is characterized by having.

In the heteroepitaxial growth method according to the first aspect, the semiconductor layer is an In _1-xy Ga _x Al _y N layer (0
≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).

In the heteroepitaxial growth method according to claim 1 or 2, the openings may be formed periodically.

[0010] In the heteroepitaxial growth method according to claim 1, 2, or 3, the substrate may be sapphire or silicon carbide.

[0011] The invention according to claim 5 is the invention according to claims 1, 2, and 3.
And a heteroepitaxial layer grown by the method of any one of the inventions of (4) and (4).

According to a sixth aspect of the present invention, a semiconductor light emitting device has the heteroepitaxial layer of the fifth aspect.

In the present invention, it is preferable that the openings whose substrate surfaces are exposed are periodically arranged vertically and horizontally. However, the arrangement interval may or may not be equal, and the size of the opening is heterogeneous so that the growth layer does not peel off from the substrate, large cracks do not enter the film, and the substrate does not break. It can be changed as long as the strain of the epitaxial layer does not increase. Its size is determined by the combination of the substrate and the epitaxial layer. For example, when GaN is heteroepitaxially grown on a sapphire substrate, one side can be changed within a range of 1500 μm or less.
The size of a film that exposes a predetermined portion on the substrate, that is, a film in which the growth rate of the semiconductor is lower than the growth rate on the substrate (hereinafter referred to as a “mask”) can be changed within a range that does not hinder the relaxation effect, For example, if the width of the mask is 1500
It can be changed within the range of μm or less.

(Operation) According to the present invention, when a heteroepitaxial layer is crystal-grown on a substrate, an InGaAlN single crystal grows in a portion where the single crystal surface of the substrate is exposed, but the single crystal surface of the substrate grows. Crystals do not grow, become polycrystalline, or become amorphous depending on the conditions in the portions that are not exposed. Compared with the case of growing a single crystal on the entire surface of the substrate, the strain generated in the crystal and the substrate can be reduced or eliminated, and the substrate is not cracked and the InGaAlN crystal does not crack, and furthermore, Also, the substrate after growth does not warp. Therefore, the group III nitride semiconductor In _1-xy Ga _x A
l _y N layer can be set high yield of chips of a semiconductor light emitting device having a made of, can be provided with good reproducibility consequently inexpensive semiconductor device.

InGaAlN has the property that it is difficult to grow flat two-dimensionally and it is easy to grow three-dimensionally. on the one hand,
InGaAlN has the property that a flat two-dimensional growth surface can be easily obtained by selective growth in a narrow region. Further, the side wall is likely to be substantially mirror-surface and perpendicular to the substrate surface. Therefore, when manufacturing a laser, an ideal resonator can be formed by selectively growing a semiconductor layer in a stripe shape.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. The embodiment is merely an example, and it goes without saying that various changes or improvements can be made without departing from the spirit of the present invention.

(Embodiment 1) FIGS. 1 to 3 are views for explaining a first embodiment of the present invention. FIG. 1 shows a substrate structure before crystal growth in the present invention. FIG. 1A is a plan view of a substrate surface on a side on which a crystal grows, and FIG.
It is sectional drawing which shows the cut surface in -A '. here,
As the substrate single crystal 3, sapphire (00
01), and the film formed on the substrate surface has a thickness of 0.1 mm.
This is a 6 μm SiO ₂ film 2. The substrate single crystal exposed surface 1 composed of a square having a side of 500 μm is arranged vertically and horizontally at intervals of 600 μm. However, the arrangement intervals need not be equal intervals, and the size of one side of the exposed surface of the substrate single crystal of 500 μm can be changed within a range where the strain of the heteroepitaxial layer does not increase. Also, the size of the SiO ₂ film as a mask can be changed within a range that does not hinder the relaxation effect. FIG. 2 shows a cross-sectional structure of the substrate after crystal growth for a semiconductor light emitting device structure is performed. An epitaxial crystal layer 4 is grown on the exposed portion 1 on the sapphire substrate single crystal 3. At this time, the substrate surface has a depth of 5n.
It may be grown after nitriding by about m. The nitride layer may be formed before forming the mask. The epitaxial crystal layer grows selectively only on the exposed portion of the substrate,
₂ did not grow on film 2. Cracks hardly occurred in the grown epitaxial crystal layer, and the substrate did not crack or warp. Next, after forming an electrode, it was polished to a thickness of 80 μm. Subsequently, a resist having a thickness of about 1 μm was applied to the epitaxial growth surface side as a protective film, and the surface was coated with a diamond scriber from the epitaxial growth surface side. Then, the silicon substrate I
Chips were formed by a usual method used for C and the like. Since there was no substrate warpage, the photolithography process was easy. FIG. 3 shows the detailed structure of the completed semiconductor light emitting device. The semiconductor light emitting device of the present invention,
A nitride layer (nitrification depth 5 nm) 19 is formed on the surface of the substrate single crystal 3 of sapphire (0001), and a 50 nm-thick Al
N buffer layer 5, 5 μm thick Si-doped n-type low resistance G
An aN layer 6, a GaN light emitting layer 7, which is semi-insulated by Zn doping with a thickness of 50 nm, an electrode 8, and an ohmic electrode 9 of an n-type low resistance layer. A positive voltage is applied to the electrode 8 and the electrode 9
When a negative voltage was applied to, the GaN light emitting layer 7 emitted light at a wavelength of 480 nm. The maximum output was 0.8 mW, and the external quantum efficiency was 0.22%.

In the first embodiment, sapphire is used as the substrate single crystal, but another material such as silicon carbide (SiC) may be used instead. Further, although the SiO ₂ film is used as the film in which the growth rate of the semiconductor is lower than the growth rate on the substrate, another material such as SiN may be used instead. According to the growth conditions used here, perfect selective growth was possible, but even if some growth occurred on the mask, a single crystal did not grow on the mask, and the film thickness was smaller than that of the single crystal region. Since it is thin, no crack occurs in the epitaxially grown film. Of course, the substrate does not break. Therefore, the effects of the present invention can be enjoyed.

(Embodiment 2) FIG. 4 is a view for explaining a second embodiment of the present invention. FIG. 4 is a cross-sectional view when the semiconductor light emitting device is cut in a direction perpendicular to the axial direction of the resonator. The substrate used has the same structure as the substrate shown in the first embodiment. However, the shape of the single crystal exposed portion 1 on the substrate single crystal 3 is 0.5
× 1 mm square, and the mask width was 100 μm. The crystal growth method is basically the same as that of the first embodiment. When strictly selective growth was performed, complete selective growth similar to that shown in FIG. 2 was achieved. The semiconductor light emitting device shown in FIG. 4 is a substrate single crystal 3 of sapphire (0001).
Layer (nitride depth 5 nm) 19, GaN buffer layer 10 having a thickness of 50 nm, Si-doped n-type GaAlN current injection and optical confinement layer having a thickness of 5 μm and an electron concentration of 5 × 10 ¹⁸ cm ^-3 11, a Si-doped n-type GaN carrier confinement layer 12 with a film thickness of 2 μm and an electron concentration of 10 ¹⁹ cm ⁻³ , an undoped In _0.1 Ga _0.9 N single quantum well light-emitting layer 13 with a thickness of 10 nm, a film thickness of 2 μm and a hole concentration of 10 ¹⁸
cm- ³ Mg-doped p-type GaN carrier confinement layer 1
4. Mg with a film thickness of 2 μm and a hole concentration of 5 × 10 ¹⁷ cm ^-3
Doped p-type GaAlN current injection and light confinement layer 15,
SiO ₂ current confinement layer 16, p-type ohmic electrode 17, n
It consists of a type ohmic electrode 18. Here, the same method as in Example 1 was used for chip formation. Further, since the side walls of the epitaxial growth region were perpendicular to the surface of the substrate and were flat in the order of atoms, no steps were required for forming the resonator end face.

Electrons and holes were injected into the light emitting layer 13 by applying a negative voltage to the electrode 18 and a positive voltage to the electrode 17. As a result, at liquid nitrogen temperature, the threshold current 6
Laser oscillation was performed at 20 mA. The oscillation wavelength is 375 nm. The maximum output was 3 mW and the external quantum efficiency was 12%.

The same layer structure as that of this embodiment was grown on a normal single-crystal substrate, and the cavity end face was formed by dry etching to produce a laser having the same structure. The threshold current was 960 mA. Met. An increase in the threshold value of 340 mA was observed as compared with the threshold value in the example of the present invention. The reason for this is that the end face formed by dry etching is inclined about 20 degrees from the perpendicular to the substrate surface, and streak-like striations generally occurring in the photolithography process for etching processing are present on the end face. It is thought to be.

[0022]

According to the present invention, no crack is formed in the epitaxial film, and no crack occurs in the substrate.
Therefore, the production yield of the element does not decrease due to the distortion. In addition, since chip formation can be performed from the epitaxial growth layer side, the process is facilitated, and the yield is increased as compared to chip formation from the substrate side. Furthermore, since no strain is introduced into the epitaxial growth layer, there is no need to consider a change in physical properties due to the strain, and there is an effect that the element design becomes easy.

In the semiconductor light emitting device of the present invention, since the epitaxial growth layer can be selectively grown, the device can be automatically separated after the epitaxial layer is grown.
In addition, by utilizing the property that the InGaAlN material has a facet and is easy to grow three-dimensionally, a smooth facet in the order of atoms can be formed substantially perpendicular to the substrate surface depending on conditions. This is an extremely large effect that simplification of the element manufacturing process and formation of a high-quality resonator can be achieved particularly when a laser is manufactured as a semiconductor light emitting element.

[Brief description of the drawings]

1A is a cross-sectional view illustrating a substrate structure before crystal growth according to the present invention, and FIG. 1B is a plan view illustrating a substrate structure before crystal growth according to the present invention.

FIG. 2 is a cross-sectional view showing a substrate structure after crystal growth according to the present invention.

FIG. 3 is a sectional view showing the structure of the semiconductor light emitting device of the present invention.

FIG. 4 is a cross-sectional view illustrating a structure of a semiconductor light emitting device according to another embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 substrate single crystal exposed surface 2 SiO ₂ film 3 substrate single crystal 4 epitaxial crystal layer 5 AlN buffer layer 6 Si-doped n-type GaN layer 7 Zn-doped GaN light emitting layer 8 electrode 9 electrode 10 GaN buffer layer 11 Si-doped n-type GaAlN layer Reference Signs List 12 Si-doped n-type GaN layer 13 In _0.1 Ga _0.9 N light-emitting layer 14 Mg-doped p-type GaN layer 15 Mg-doped p-type GaAlN layer 16 SiO ₂ layer 17 Electrode 18 Electrode 19 Nitride layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/203 H01L 21/203 M H01S 3/18 H01S 3/18

Claims (6)

[Claims] 1. A heteroepitaxial growth method for growing a semiconductor layer having a lattice constant different from that of a substrate on a substrate, wherein a layer having an opening for selectively growing the semiconductor layer is formed at a predetermined position on the substrate. Exposing the predetermined portion of the substrate by the opening, and selectively heteroepitaxially growing the semiconductor layer on the surface of the substrate exposed by the opening. Heteroepitaxial growth method. 2. The method according to claim 1, wherein the semiconductor layer is made of In _1-xy Ga _x Al.
_{2. The} heteroepitaxial growth method according to claim 1, wherein the multilayer film includes a yN layer (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). 3. The heteroepitaxial growth method according to claim 1, wherein the openings are formed periodically. 4. The heteroepitaxial growth method according to claim 1, wherein the substrate is sapphire or silicon carbide. 5. A heteroepitaxial layer grown by the method according to claim 1, 2, 3, or 4. 6. A semiconductor light emitting device comprising the heteroepitaxial layer according to claim 5.