JP2003046117A - Method for manufacturing semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the convexo-concaving of the surface of a film produced by an MOCVD method is difficult since thickness reduction is requested, though the convexo-concaving of the surface of a clad layer, etc., is easy since a film of at least several ten μm is formed there in a normal semiconductor light-emitting element. SOLUTION: On a semiconductor substrate, a one conductivity type semiconductor layer and an opposite conductivity type semiconductor layer are laminated in order so that the total of the film thickness of both of the layers is <=15 μm. One electrode is formed on the opposite conductivity type semiconductor layer, the other electrode is formed on the rear surface of the semiconductor substrate, the opposite conductivity type semiconductor layer additionally has light emitting layers and clad layers laminated in order, a film containing Zn is formed on an upper face, and thermal treatment is given after this to form a face given rough face treatment, thereby improving optical outside take-out efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a method for manufacturing a semiconductor light emitting device suitable for an infrared semiconductor light emitting device used for infrared communication or remote control.

[0002]

2. Description of the Related Art A conventional infrared semiconductor light emitting device is shown in FIG. This figure is a cross-sectional view of this device, in which 11 is a semiconductor substrate, on which semiconductor layer 11 of one conductivity type and semiconductor layer 13 of opposite conductivity type are epitaxially grown, and further semiconductor layer of opposite conductivity type. P-side electrode 14 is formed on 13. The N-side electrode 1 is formed on the back surface of the semiconductor substrate 11.
5 is formed.

Then, by applying a voltage between the P-side electrode 14 and the N-side electrode 15, the light emitted inside is taken out to the outside from the portion where the P-side electrode 14 is not provided or the side surface.

In such an infrared semiconductor light emitting device, a homojunction structure semiconductor light emitting device or a single heterojunction structure semiconductor light emitting device or a double heterojunction structure semiconductor light emitting device having high carrier injection efficiency, high output and high response speed can be obtained. A junction structure semiconductor light emitting device is known.

Further, the conventional infrared semiconductor light emitting device is usually manufactured by epitaxial growth by the LPE method (Liquid Phase Epitaxy). According to this method, the one-conductivity-type semiconductor layer 12 and the opposite-conductivity-type semiconductor layer 13 are each tens of μm.
The film is formed with a film thickness of m or more.

In addition, in such a semiconductor light emitting device, a technique of making unevenness on the light emitting surface has been proposed.

According to this proposal, unevenness is formed on the light extraction surface by making unevenness on the surface by forming unevenness on the surface, which increases the effective solid angle and increases the light extraction efficiency. Is improved.

The method of making the surface uneven as described above is as follows. First, the one conductivity type semiconductor layer 12 and the opposite conductivity type semiconductor layer 13 are sequentially epitaxially grown on the semiconductor substrate 11, and then the N-side electrode 15 is provided on the back surface and the P-side electrode 14 is provided on the front surface, followed by dicing. After forming a groove between each element by, etc., the surface is made uneven by immersing it in an etching solution. In the portion where this etching is most advanced, etching of several tens of μm or more is performed.

In this regard, Japanese Patent Application Laid-Open No. 10-200156 proposes a technique of using a nitric acid-based etching solution. Nitric acid can very effectively form irregularities on the semiconductor surface depending on the composition of the solution. Can be made, usually
For an infrared semiconductor light emitting device made of GaAs, an etching solution obtained by diluting nitric acid with water or the like is used to roughen the surface.

However, when this etching solution is used, the etching rate becomes very high, and therefore, in order to make the surface irregularities, a film having a thickness of about 10 μm or more is necessary only for that purpose. It should be noted that if the etching rate is reduced, the unevenness of the surface does not occur, so that the luminous efficiency cannot be increased.

Further, according to Japanese Patent Laid-Open No. 4-296723, in a semiconductor light emitting device in which the Al composition of the AlGaAs cladding layer is large (the Al composition ratio is about 0.35 or more), the surface is roughened by hydrofluoric acid. However, if the Al composition becomes small, the surface cannot be made uneven.

Further, Japanese Patent Application Laid-Open No. 3-247771 exemplifies a case where the surface is roughened by using an etching solution of ammonia-hydrogen peroxide system.

However, all of these known surface irregularities are for thick films formed by the LPE method, and are not suitable for thin films.

That is, in a film formed by the LPE method as in the prior art, it is easy to make the film thicker, and by making it thicker, the spread of light emission is increased, and the surface is greatly etched to make the surface uneven. We have been trying to improve the luminous efficiency.

[0015]

However, the semiconductor layer is formed by MOCVD (Metalorganic Chemical Vapor Depo Deposition).
In the case of forming a thin layer by a sition), it was difficult to carry out by the above-mentioned known surface unevenness forming method.

To further describe the MOCVD method, in recent years, higher output and higher response speed have been demanded, and the epitaxial film has been made thinner for that purpose. And, the technique of forming a film by MOCVD is drawing attention.

According to this MOCVD method, it becomes easy to control the film thickness or composition, and a semiconductor light emitting device having an increasingly complicated structure can be manufactured.

However, in this MOCVD method, LP
Compared with the E method, the film forming speed is very slow and the film forming time is significantly long, which is not suitable for forming a thick film.

Moreover, in the MOCVD method, the raw material actually used for film formation is only a part of it, and most of it is discarded. Therefore, thickening the film causes a significant increase in cost. It was

Therefore, the present invention has been completed in view of the above, and an object thereof is to successively laminate one conductivity type semiconductor layer and reverse conductivity type semiconductor layer by a thin film forming technique such as MOCVD method, and It is an object of the present invention to provide a method for manufacturing a high-performance semiconductor light emitting device in which the light emitting surface is a roughened surface, the effective solid angle is increased, and the light extraction efficiency is improved.

Another object of the present invention is to provide a method for manufacturing a semiconductor light emitting device with improved luminous efficiency.

[0022]

The method for manufacturing a semiconductor light emitting device of the present invention is characterized in that the light emitting surface is roughened by sequentially performing the following steps (1) to (4). (1) A gallium arsenide-based one conductivity type semiconductor layer and an opposite conductivity type semiconductor layer are sequentially stacked on a semiconductor substrate. (3) At least both the opposite conductivity type semiconductor layer and the Zn-containing layer are heated to diffuse Zn into the opposite conductivity type semiconductor layer. (4) The Zn-containing layer is removed by etching and the surface of the opposite conductivity type semiconductor layer is roughened.

Another method of manufacturing a semiconductor light emitting device according to the present invention is characterized in that the gallium arsenide-based one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer are formed by MOCVD.

Still another semiconductor light emitting device manufacturing method of the present invention is characterized in that the total film thickness of both the gallium arsenide-based one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer is 15 μm or less. .

According to the present invention, the Zn-containing layer is formed on the reverse-conductivity-type semiconductor layer as in the above structure, and the heat treatment step is performed. The surface can be roughened.

Further, since the Zn-containing layer is formed on the reverse-conductivity type semiconductor layer as in the present invention, Zn atoms are diffused in the reverse-conductivity type semiconductor layer at a high concentration during the heat treatment. As a result, Zn atoms were efficiently diffused into the semiconductor layer, and the current flowing inside was not concentrated under the electrodes, and as a result, the luminous efficiency was improved.

[0026]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings.

[Example 1] FIG. 1 is a cross-sectional view showing a film structure of a semiconductor light emitting device according to the present invention, which is not subjected to surface roughening treatment by heat treatment-etching treatment. Figure 2
FIG. 3 is a cross-sectional view showing an embodiment of a semiconductor light emitting device of the present invention, which has been subjected to surface roughening treatment by etching.

Referring to FIG. 1, the structure before roughening treatment by heating / etching will be described.

1 is a substrate, 2 is a one conductivity type semiconductor layer, 3 is a reverse conductivity type semiconductor layer, 6 is a ZnO film which is the Zn-containing layer,
Reference numeral 7 is a SiO ₂ film.

The substrate 1 is a single crystal semiconductor substrate made of gallium arsenide (GaAs), silicon (Si) or the like.

The one conductivity type semiconductor layer 2 is composed of a buffer layer 2a and an electron injection layer 2b.

The buffer layer 2a is formed to a thickness of about 0.5 to 3 μm, and the electron injection layer 2b is formed to a thickness of about 0.2 to 5 μm.

The buffer layer 2a is formed of gallium arsenide or the like, and the electron injection layer 2b is formed of aluminum gallium arsenide (G).
aAlAs) or the like.

The electron injection layer 2b contains 1 × 10 ¹⁶ to 10 ¹⁹ atoms of one conductivity type semiconductor impurity such as silicon.
/ Cm ^{3 is} contained. At this time, the electron injection layer 2b
The Al composition is expressed as (GaAs) 1-xAlx, where x is about 0.2 to 0.5.

The opposite conductivity type semiconductor layer 3 is composed of a light emitting layer 3a, a cladding layer 3b and an ohmic contact layer 3c.

The light emitting layer 3a is formed to a thickness of about 0.2 to 1 μm, the cladding layer 3b is formed to a thickness of 1 to 5 μm, and the ohmic contact layer 3c is formed to a thickness of about 0.01 to 1 μm.

The light emitting layer 3a is made of aluminum gallium arsenide,
It is made of gallium arsenide or the like and contains 1 × 10 ¹⁶ to 10 ¹⁸ atoms / cm 3 of a reverse conductivity type semiconductor impurity such as zinc (Zn).
^Contain about ³

The clad layer 3b is made of aluminum arsenide (AlA) in consideration of the electron confinement effect and the light extraction effect.
The mixed crystal ratio of s) and gallium arsenide (GaAs) is made different between the two.

The cladding layer 3b contains 1 × 10 ¹⁶ to 10 ²⁰ atoms / c of a reverse conductivity type semiconductor impurity such as zinc (Zn).
Contains about m ³ .

The Al composition of the clad layer 3b is (GaAs)
When expressed by 1-xAlx, x is formed at about 0.2 to 0.5.

The ohmic contact layer 3c is made of gallium arsenide or the like, and has a reverse conductivity type semiconductor impurity such as zinc.
× 10 ¹⁹ to 10 ²⁰ atoms / cm ^{3 is} contained.

A ZnO film 6 is then deposited on the surface of the ZnO film 6 by 500 to 2000 Å.
It is formed with the thickness of. Furthermore, on the ZnO film 6, SiO ₂
The film 7 is formed to a thickness of 1000 to 2000Å.

(Method of Manufacturing Semiconductor Light Emitting Element) Next, a method of manufacturing the semiconductor light emitting element of the present invention will be described. The following steps (1) to (4) are sequentially performed. Note that the structure as shown in FIG. 1 is obtained through the steps (1) and (2).

Step (1): A gallium arsenide-based one conductivity type semiconductor layer and an opposite conductivity type semiconductor layer are sequentially laminated on a semiconductor substrate.

That is, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are sequentially formed on the single crystal substrate 1 by MOCVD.

When forming these semiconductor layers 2 and 3,
The substrate temperature is raised to 700 to 900 ° C. to form the semiconductor layers 2 and 3 having a desired thickness.

In this case, TMG ((C
H₃ )₃ Ga), TEG ((C₂ H _Five )₃ Ga), Al
Shin (AsH₃ ), TMA ((CH₃ )₃ Al), TE
A ((C₂ H_Five )₃ Al) is used to control the conductivity type.
As the gas for controlling, silane (SiH_Four ), Cele
Hydrogen fluoride (H₂ Se), DMZ ((CH₃ )₂ Zn)
Which is used and H is used as the carrier gas.₂Used by
To be

Step (2): A Zn-containing layer is formed on the opposite conductivity type semiconductor layer.

That is, the ZnO film 6 and the SiO ₂ film 7 are formed by the sputtering method or the like. At this time, the ZnO film 6 is formed to a thickness of 500 to 2000Å, and the SiO ₂ film is formed to a thickness of 1000 to 2000Å.

The ZnO layer diffuses Zn into the semiconductor layer. Instead of this ZnO layer, a Zn layer or a Z layer is formed.
It may be an nAs layer. Further, a film in which SiO ₂ is mixed with each of these layers may be used.

Step (3): At least both the opposite conductivity type semiconductor layer and the Zn-containing layer are heated.

That is, Zn is diffused into the substrate by annealing this substrate at 600 to 700 degrees for several tens of minutes.

Step (4): The Zn-containing layer and the opposite conductivity type semiconductor layer are subjected to etching treatment to roughen the surface of the opposite conductivity type semiconductor layer.

That is, the ZnO film 6 and the SiO ₂ film 7 are removed by wet etching using hydrofluoric acid or the like. With such removal, the ohmic contact layer 3c is also roughened.

Each of the above steps is a basic process of the manufacturing method of the present invention, and the semiconductor light emitting device of the present invention is obtained by passing through such processes.

Actually, the following steps are continuously performed. The semiconductor layers 2 and 3 are patterned in an island shape so that each element is separated.

For this etching, wet etching using a sulfuric acid / hydrogen peroxide type etching solution or CCl ₂ F ₂ is used.
It is performed by dry etching using ₂ gases. This etching step may be omitted if dicing or the like is used to separate each element.

Then, Au or the like is formed by a vapor deposition method or a sputtering method and the P-side electrode 4 is patterned, and an N-side electrode 5 is formed of AuGe or the like by a vapor deposition method or a sputtering method.

Thus, according to the semiconductor light-emitting device obtained by the manufacturing method of the present invention, the clad layer as shown in FIG. 3b becomes an uneven state.

The surface roughness after such etching treatment is, for example, Ra = about 500 Å.

By forming such a roughened surface, irregularities having various angles are formed on the light extraction surface when viewed microscopically, and the effective solid angle is increased, whereby the light extraction efficiency is improved. As a result, higher output of the semiconductor light emitting device was realized.

In the present invention, when the semiconductor layer is formed by the thin film forming technique such as MOCVD method, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are laminated after the roughening treatment by etching. The total film thickness of both is set to 15 μm or less.

With this setting, the confinement effect of the clad layer can be sufficiently obtained, and the current diffusion effect can be provided so that the current is not concentrated under the electrode.

Moreover, by setting the film thickness at the upper limit, the film forming time can be shortened within a required amount, and the manufacturing cost can be reduced.

Further, since Zn is solid-phase-diffused in the step (3), a high-concentration P-type diffusion region is formed in the periphery of the diffusion source, and the resistance is reduced.

Furthermore, due to the solid phase diffusion of Zn, the diffusion depth is shallow, and the surface roughness occurs only on the outermost surface, so that the cladding layer 3b is not affected by the etching, so that carrier injection is performed. High efficiency,
The features of the double-heterojunction structure semiconductor light-emitting device such as high output and high response speed are not impaired.

Moreover, as described above, in the conventional semiconductor light emitting device, the cladding layer and the like are each formed with a film having a thickness of several tens of μm or more by the epitaxial growth by the LPE method. Is easy to do. However, it is difficult to make the surface uneven because the film formed by MOCVD is required to be thin.
Thus, by performing heat treatment after forming the ZnO layer and the SiO ₂ film, the surface unevenness treatment can be stably performed even when the film is thin, and a high concentration P diffusion region can be formed. I was able to.

FIG. 8 shows the measurement results comparing the light emission intensities of the semiconductor light emitting device according to the present invention (Example 1) and the conventional semiconductor light emitting device (without surface irregularities).

The buffer layer 2a is a gallium arsenide layer of 0.5.
The electron injection layer 2b is formed to have a thickness of μm and has an Al composition of x =
0.3 gallium aluminum gallium arsenide was formed to a thickness of 2 μm.

The light emitting layer 3a is formed of a gallium arsenide layer with a thickness of 1 μm, the cladding layer 3b is formed of aluminum gallium arsenide with an Al composition of x = 0.3 with a thickness of 2 μm, and the ohmic contact layer 3c is a gallium arsenide layer. 0.01
It was formed to a thickness of μm.

After that, a ZnO film of 1000 Å and SiO ₂
A film was formed by using a 2000Å sputtering method, and then heat treatment was applied at 650 ° C. for 25 minutes.

After this heat treatment, if the ZnO film and the SiO ₂ film are removed with, for example, hydrofluoric acid, irregularities are formed at the interface between the ZnO film and the gallium arsenide layer. The present inventor believes that such unevenness is formed due to the mutual diffusion of ZnO and GaAs.

The P-side electrode 4 is a gold / chromium electrode having a thickness of about 1 μm, and the N-side electrode 5 is gold-germanium-.
It was made of nickel and formed to a thickness of about 1 μm.

By carrying out such a treatment, the surface roughness Ra after the film formation was about 50 Å, but the surface roughness Ra after the etching treatment could be about 500 Å.

The wafer thus produced was evaluated by measuring the emission intensity in a wafer state. As a result, the emission intensity could be increased by about 20% as shown in FIG.

Example 2 FIG. 3 is a cross-sectional view showing the film structure of the semiconductor light emitting device according to the present invention, which is before the roughening treatment by heat treatment. FIG. 4 is a cross-sectional view showing an embodiment of the semiconductor light emitting device of the present invention, which has been roughened by etching. The same members as those of the semiconductor light emitting device shown in FIGS. 1 and 2 are designated by the same reference numerals.

In FIG. 3, 1 is a substrate, 2 is a one conductivity type semiconductor layer, 3 is a reverse conductivity type semiconductor layer, 6 is a ZnO layer, and 7 is S.
The iO ₂ film and 8 are diffusion masks.

The film formation of the one-conductivity-type semiconductor layer and the opposite-conductivity-type semiconductor layer is the same as that described in Example 1, but thereafter, Si is used.
A diffusion mask 8 of N or the like is formed by using a P-CVD method or the like. After that, patterning is performed using photolithography so that the diffusion mask 8 is left according to the shape of the electrode.

A ZnO film 6 is further formed thereon to 500 to 2000.
Å, the SiO ₂ film 7 is formed with a thickness of 1000 to 2000Å.

The semiconductor light emitting device of the present invention is obtained by subjecting the structure shown in FIG.
As shown in, the clad layer 3b becomes uneven.

According to such a roughening treatment, the surface roughness after the etching treatment becomes Ra = about 500Å, for example.

Thus, by forming such a roughened surface, irregularities having various angles are formed on the light extraction surface in a microscopic view, and the effective solid angle is increased, which results in light The extraction efficiency was improved, and as a result, higher output of the semiconductor light emitting device was realized.

In the present invention, when the semiconductor layer is formed by the thin film forming technique such as MOCVD method, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are laminated after the roughening treatment by etching. The total film thickness of both is set to 15 μm or less.

With this setting, the confinement effect of the cladding layer can be sufficiently obtained, and the current diffusion effect can be provided so that the current is not concentrated under the electrode.

Moreover, by setting the film thickness at the upper limit, the film formation time can be shortened within a required time, and the manufacturing cost can be reduced.

(Manufacturing Method of Semiconductor Light Emitting Element) Next, a manufacturing method of the above semiconductor light emitting element will be described.

First, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are sequentially formed on the single crystal substrate 1 by MOCVD.

When forming these semiconductor layers 2 and 3,
The substrate temperature is raised to 700 to 900 ° C. to form the semiconductor layers 2 and 3 having a desired thickness.

In this case, TMG ((C
H₃ )₃ Ga), TEG ((C₂ H _Five )₃ Ga), Al
Shin (AsH₃ ), TMA ((CH₃ )₃ Al), TE
A ((C₂ H_Five )₃ Al) is used to control the conductivity type.
As the gas for controlling, silane (SiH_Four ), Cele
Hydrogen fluoride (H₂ Se), DMZ ((CH₃ )₂ Zn)
Which is used and H is used as the carrier gas.₂Used by
To be

Thereafter, the diffusion mask 8 is replaced with SiN or the like by 10
A film having a thickness of 00 to 3000 Å is formed by using the P-CVD method or the like. Then, using photolithography, patterning is performed so as to leave a diffusion mask in conformity with the electrode shape.

Next, the ZnO layer 6 and the SiO ₂ film 7 are formed by the sputtering method or the like. At this time, Z
The nO film 6 is 500 to 2000Å, the SiO ₂ film is 1000
Form with a thickness of ~ 2000Å.

Thereafter, this substrate is annealed at 600 to 700 ° C. for several tens of minutes to diffuse Zn into the substrate and make the surface of the substrate rough.

After that, the ZnO film and the SiO ₂ film are removed by using hydrofluoric acid or the like.

Next, the semiconductor layers 2 and 3 are patterned in an island shape so that each element is separated.

For this etching, wet etching using a sulfuric acid / hydrogen peroxide type etching solution or CCl ₂ F ₂ is used.
It is performed by dry etching using ₂ gases. This etching step may be omitted if dicing or the like is used to separate each element.

Then, Au or the like is formed by a vapor deposition method or a sputtering method, the electrodes are patterned, and the back surface is made of AuG.
Similarly, e and the like are formed by vapor deposition or sputtering.

By using the solid phase diffusion of Zn as described above, a high-concentration P-type diffusion region can be formed around the diffusion source, and the resistance can be reduced. Further, since the solid phase diffusion of Zn is used, the diffusion depth is shallow, and the surface roughness is generated only on the outermost surface. Therefore, the cladding layer 3b is not affected by the etching, so that the carrier injection efficiency is improved. The features of the double heterojunction structure semiconductor light emitting device that are high, high output, and high response speed are not impaired.

Further, by making the surface uneven, unevenness having various angles is formed on the light extraction surface in a microscopic view, thereby increasing the effective solid angle and improving the light extraction efficiency. As a result, it is possible to realize higher output of the semiconductor light emitting device.

As described above, in the conventional semiconductor light emitting device, the cladding layer and the like are each formed with a film of several tens of μm or more by being epitaxially grown by the LPE method, so that the surface is roughened. Is easy.

However, it is difficult to make the surface uneven because the film formed by the MOCVD method is required to be thin.
By performing heat treatment after forming the ZnO layer or the SiO ₂ film in this way, surface unevenness treatment can be stably performed even when the film is thin, and a high concentration P diffusion region can be formed. I was able to.

Further, with such a structure, the current mainly flows through the Zn diffusion layer, so that the current can be prevented from being concentrated under the electrode.

FIG. 8 shows the measurement results comparing the light emission intensities of the semiconductor light emitting device according to the present invention (Example 2) and the conventional semiconductor light emitting device.

The buffer layer 2a is a gallium arsenide layer having a thickness of 0.5.
The electron injection layer 2b is formed to have a thickness of μm and has an Al composition of x =
0.3 gallium aluminum gallium arsenide was formed to a thickness of 2 μm.

The light emitting layer 3a is formed of a gallium arsenide layer with a thickness of 1 μm, the cladding layer 3b is formed of aluminum gallium arsenide with an Al composition of x = 0.3 with a thickness of 2 μm, and the ohmic contact layer 3c is formed with a gallium arsenide layer. 0.01
It was formed to a thickness of μm.

Thereafter, a diffusion prevention SiN film is added to 2000 Å,
A ZnO film was formed by 1000 Å and a SiO ₂ film was formed by 2000 Å sputtering method, and thereafter, heat treatment was applied at 650 ° C. for 25 minutes.

The P-side electrode 4 is a gold / chromium electrode having a thickness of 1 μm.
The N-side electrode 5 was made of gold-germanium-nickel and had a thickness of about 1 μm.

By carrying out such a treatment, the surface roughness Ra after the film formation was about 50 Å, but the surface roughness Ra after the etching treatment was about 500 Å.

The wafer thus produced was evaluated by measuring the emission intensity in a wafer state. As a result, the emission intensity could be increased by about 20% as shown in FIG.

Example 3 FIG. 5 is a cross-sectional view showing a film structure of a semiconductor light emitting device according to the present invention, which is before roughening treatment by heat treatment. FIG. 6 is a cross-sectional view showing an embodiment of the semiconductor light emitting device of the present invention, which is subjected to a surface roughening treatment by etching. The same members as those of the semiconductor light emitting device shown in FIGS. 1 to 4 are designated by the same reference numerals.

In FIG. 5, 1 is a substrate, 2 is a one conductivity type semiconductor layer, 3 is a reverse conductivity type semiconductor layer, 6 is a ZnO layer, and 7 is S.
The iO ₂ film and 8 are diffusion masks.

The film formation of the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer is the same as that described in 1.

Thereafter, the diffusion mask 8 made of SiN or the like is set to P-
The film is formed by using the CVD method or the like. Then, using photolithography, patterning is performed so as to leave a diffusion mask in conformity with the electrode shape.

A ZnO film having a thickness of 500 to 2000Å,
An SiO ₂ film is formed with a thickness of 1000 to 2000Å.

The semiconductor light emitting device of the present invention is obtained by subjecting the structure shown in FIG.
As shown in, the clad layer 3b becomes uneven.

Such a surface roughening treatment will be described in detail by a manufacturing method described later, but the surface roughness after the etching treatment is Ra = about 500Å, for example.

Thus, by forming such a roughened surface, microscopically, irregularities having various angles are formed on the light extraction surface, so that the effective three-dimensional angle becomes large. The extraction efficiency was improved, and as a result, higher output of the semiconductor light emitting device was realized.

In the present invention, when the semiconductor layer is formed by a thin film forming technique such as MOCVD, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are laminated after the roughening treatment by etching. The total film thickness of both is set to 15 μm or less.

With this setting, the confinement effect of the cladding layer can be sufficiently obtained, and the effect of current diffusion can be provided so that the current is not concentrated under the electrode.

Moreover, by setting the film thickness at the upper limit, the film formation time can be shortened within a required time, and the manufacturing cost can be reduced.

(Method for Manufacturing Semiconductor Light Emitting Element) Next, a method for manufacturing the semiconductor light emitting element of the present invention will be described. First, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are sequentially formed on the single crystal substrate 1 by MOCVD or the like.

When these semiconductor layers 2 and 3 are formed,
The substrate temperature is raised to 700 to 900 ° C. to form the semiconductor layers 2 and 3 having a desired thickness.

In this case, TMG ((C
H₃ )₃ Ga), TEG ((C₂ H _Five )₃ Ga), Al
Shin (AsH₃ ), TMA ((CH₃ )₃ Al), TE
A ((C₂ H_Five )₃ Al) is used to control the conductivity type.
As the gas for controlling, silane (SiH_Four ), Cele
Hydrogen fluoride (H₂ Se), DMZ ((CH₃ )₂ Zn)
Which is used and H is used as the carrier gas.₂Used by
To be

Thereafter, the diffusion mask is made of SiN, etc.
A film having a thickness of up to 3000 Å is formed by the P-CVD method or the like. Then, using photolithography, patterning is performed so as to leave a diffusion mask in conformity with the electrode shape.

Next, a ZnO layer and a SiO ₂ film are formed by the sputtering method or the like. At this time, ZnO
The film is 500 ~ 2000Å, the SiO ₂ film is 1000 ~ 20
It is formed with a thickness of 00Å. Here, ZnO is for diffusing Zn, and may be Zn or ZnAs. Further, it may be a film in which SiO ₂ is mixed in each.
When a mixed film of SiO ₂ is used, if the ratio of SiO ₂ is large, it becomes difficult for the surface to become uneven, so the ratio of Zn is made large.

Then, this substrate is annealed at 600 to 700 ° C. for several tens of minutes to diffuse Zn into the substrate and make the surface of the substrate rough.

After that, using photolithography, only the portions in contact with the electrodes are etched to remove other Zn.
The O film and the SiO ₂ film are used as a passivation film without being removed.

Next, the semiconductor layers 2 and 3 are patterned in an island shape so that each element is separated.

For this etching, wet etching using a sulfuric acid / hydrogen peroxide type etching solution or CCl ₂ F ₂ is used.
It is performed by dry etching using ₂ gases. This etching step may be omitted if dicing or the like is used to separate each element.

Then, Au or the like is formed by a vapor deposition method or a sputtering method, the electrodes are patterned, and the back surface is made of AuG.
Similarly, e and the like are formed by vapor deposition or sputtering.

By using the solid phase diffusion of Zn as described above, a high-concentration P-type diffusion region can be formed around the diffusion source, and the resistance can be reduced. Further, since the solid phase diffusion of Zn is used, the diffusion depth is shallow, and the surface roughness is generated only on the outermost surface. Therefore, the cladding layer 3b is not affected by the etching, so that the carrier injection efficiency is improved. The features of the double heterojunction structure semiconductor light emitting device that are high, high output, and high response speed are not impaired.

Further, by making the surface uneven, unevenness having various angles is formed on the light extraction surface in a microscopic view, so that the effective solid angle is increased and the light extraction efficiency is improved. As a result, higher output of the semiconductor light emitting device can be realized.

As described above, in the conventional semiconductor light emitting device, the cladding layer and the like are each formed with a film having a thickness of several tens of μm or more by the epitaxial growth by the LPE method, so that the surface is roughened. Is easy.

However, since the film formed by the MOCVD method is required to be thin, it is difficult to make the surface uneven.
By performing heat treatment after forming the ZnO layer or the SiO ₂ film in this way, surface unevenness treatment can be stably performed even when the film is thin, and a high concentration P diffusion region can be formed. I was able to.

Further, with such a structure, the current mainly flows through the Zn diffusion layer, so that the current can be prevented from being concentrated under the electrode.

FIG. 8 shows the measurement results comparing the light emission intensities of the semiconductor light emitting device according to the present invention (Example 3) and the conventional semiconductor light emitting device.

The buffer layer 2a is a gallium arsenide layer having a thickness of 0.5.
The electron injection layer 2b is formed to have a thickness of μm and has an Al composition of x =
0.3 gallium aluminum gallium arsenide was formed to a thickness of 2 μm.

The light emitting layer 3a is a gallium arsenide layer having a thickness of 1 μm, the clad layer 3b is aluminum gallium arsenide having an Al composition of x = 0.3 having a thickness of 2 μm, and the ohmic contact layer 3c is a gallium arsenide layer. 0.01
It was formed to a thickness of μm.

Thereafter, a diffusion preventing SiN film is added to 2000 Å,
A ZnO film was formed by 1000 Å and a SiO ₂ film was formed by 2000 Å sputtering method, and thereafter, heat treatment was applied at 650 ° C. for 25 minutes.

The P-side electrode 4 is a gold / chromium electrode having a thickness of 1 μm.
The N-side electrode 5 was made of gold-germanium-nickel and had a thickness of about 1 μm.

By carrying out such a treatment, the surface roughness Ra after the film formation was about 50 Å, but the surface roughness Ra after the etching treatment was about 500 Å.

The wafer thus produced was evaluated by measuring the emission intensity in a wafer state. As a result, as shown in FIG. 8, the emission intensity could be increased by about 30%.

[0142]

As described above, according to the semiconductor light emitting device of the present invention, the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer are sequentially formed on the semiconductor substrate so that the total film thickness of both is 15 μm or less. Further, the reverse conductivity type semiconductor layer was formed by sequentially stacking a light emitting layer and a cladding layer, forming a film containing Zn on the upper surface, and then adding heat treatment to form a roughened surface. As a result, the effective solid angle can be increased and the light extraction efficiency can be increased, whereby a high performance semiconductor light emitting device can be provided.

Further, according to the present invention, during the solid phase diffusion of Zn, the surface is roughened by utilizing the phenomenon that the surface is roughened by using a diffusion source having a high Zn content. By increasing the angle and increasing the light extraction efficiency, a high-performance semiconductor light emitting device could be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a film structure of a semiconductor light emitting device before roughening treatment by heat treatment according to the present invention.

FIG. 2 is a cross-sectional view showing a film structure of a semiconductor light emitting device which has been subjected to a surface roughening treatment by a heat treatment according to the present invention.

FIG. 3 is a cross-sectional view showing a film structure of another semiconductor light emitting device before roughening treatment by heat treatment according to the present invention.

FIG. 4 is a cross-sectional view showing a film structure of another semiconductor light emitting device which has been subjected to a surface roughening treatment by a heat treatment according to the present invention.

FIG. 5 is a cross-sectional view showing a film structure of still another semiconductor light emitting device before the roughening treatment by the heat treatment according to the present invention is performed.

FIG. 6 is a cross-sectional view showing a film structure of still another semiconductor light emitting device which has been subjected to a surface roughening treatment by a heat treatment according to the present invention.

FIG. 7 is a cross-sectional view showing a conventional semiconductor light emitting device.

FIG. 8 is an evaluation diagram showing the emission intensity of a semiconductor light emitting device.

[Explanation of symbols]

1, 11 ... Semiconductor substrate 2, 12 ... One conductivity type semiconductor layer 3, 13 ... Reverse conductivity type semiconductor layer 4, 14 ... P-side electrode 5, 15 ... N-side electrode 6. ..Zn diffusion source (ZnO) 7 ... Cap film (SiO ₂ ) 8 ... Diffusion prevention film 2a ... Buffer layer 2b ... Electron injection layer 3a ... Light emitting layer 3b ... Clad layer 3c ... Ohmic contact layer

Claims (3)

[Claims] 1. A method for manufacturing a semiconductor light emitting device, characterized in that a light emitting surface is roughened by sequentially performing the following steps (1) to (4). (1) A gallium arsenide-based one conductivity type semiconductor layer and an opposite conductivity type semiconductor layer are sequentially stacked on a semiconductor substrate. (2) A Zn-containing layer is formed on the opposite conductivity type semiconductor layer. (3) At least both the opposite conductivity type semiconductor layer and the Zn-containing layer are heated to diffuse Zn into the opposite conductivity type semiconductor layer. (4) The Zn-containing layer is removed by etching and the surface of the opposite conductivity type semiconductor layer is roughened. 2. A method of manufacturing a semiconductor light emitting device according to claim 1, wherein the gallium arsenide-based one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer are formed by MOCVD. 3. The method of manufacturing a semiconductor light emitting device according to claim 2, wherein the total thickness of both the gallium arsenide-based one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer is 15 μm or less.