JPH08236867A - Nitride-based compound semiconductor light emitting device and method for manufacturing the same - Google Patents

Abstract

(57) [Summary] [Structure] After forming a groove in a sapphire substrate, a light emitting device structure including a nitride-based compound semiconductor layer is selectively crystal-grown. In addition, after forming a selective growth region mask on the substrate in which the groove is formed, a nitride compound semiconductor is crystal-grown. After these crystal growth and electrode formation, each groove is used to form a chip into each light emitting element. [Effect] The chip can be formed without damaging the crystal, and the yield is improved. Further, even when a laser resonator is manufactured by using dry etching or the like, a good resonator structure can be easily grown without damaging the crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode or a semiconductor laser device using a nitride-based compound semiconductor crystal used as a light source for display or information terminal.

[0002]

2. Description of the Related Art A nitride-based compound semiconductor grown on a sapphire substrate has a hexagonal crystal structure. Therefore, while the crystal structure of cubic GaAs or the like is easy to cleave, the cleavage of nitride compound semiconductor crystal is very difficult. Therefore, the conventional technique for manufacturing a light emitting device is, as in JP-A-5-343742, a method in which a gallium nitride-based compound semiconductor layer is stacked on a sapphire substrate and then separated into individual devices by etching and dicing. Was there. First, a protective film layer is provided on a gallium nitride-based compound semiconductor layer laminated on a sapphire substrate, and etching is performed up to the n-type semiconductor layer. After that, the sapphire substrate was etched or diced while leaving a part of the n-type semiconductor layer to separate each light emitting element.

In such a conventional technique, damage to the nitride compound semiconductor crystal becomes a problem. Further, there is a problem that it is very difficult to obtain a vertical crystal plane that becomes a cavity surface of a semiconductor laser regardless of wet and dry etching. Further, when dicing the region formed by etching, it is difficult to align the blade, and there is a problem that the yield is low.

[0004]

SUMMARY OF THE INVENTION In the present invention, first, each nitride-based compound semiconductor layer is damaged by selectively growing each light emitting device structure on a sapphire substrate in which a groove is formed in advance. It is intended to be a chip without. Secondly, the aim is to obtain vertical crystal planes. Thirdly, it is intended to simplify the manufacturing process of the nitride compound semiconductor light emitting device. Fourthly, the purpose is to fabricate a light emitting device structure made of a nitride compound semiconductor in an arbitrary shape.

[0005]

As means for solving the problem, a groove is formed in a sapphire substrate by at least wet or dry etching or dicing using a blade. After that, the nitride compound semiconductor layer is selectively crystal-grown on the substrate in which the groove is formed. In addition, after forming a selective growth region mask on the substrate in which the groove is formed, a nitride compound semiconductor is crystal-grown. Further, using the groove, each light emitting element is formed into a chip.

[0006]

By forming a groove in the sapphire substrate, the nitride-based compound semiconductor layer can be selectively crystal-grown in a region other than the groove. Further, in that region, a vertical crystal plane can be easily obtained by selective growth. In addition, since the nitride-based compound semiconductor layer is selectively grown in each region and is separated at the same time, chips can be formed by utilizing the groove without damaging the crystal and the manufacturing process is simplified. Become. Then, after forming a selective growth mask on the substrate in which the groove is formed, crystal growth is performed, so that an element structure having an arbitrary shape such as an end face non-excited structure can be manufactured.

[0007]

【Example】

(Embodiment 1) As shown in FIG. 1, a width of 100 μm and a depth of 10 μm are dry-etched on a sapphire substrate 1 having a thickness of 300 μm in each area of 800 μm in width and 500 μm in length.
The first groove 2 was formed. Next, use a dicer with a blade in the center of the groove formed by etching to obtain a width of 50 μm.
A second groove 3 having a depth of m and a depth of 100 μm was formed. afterwards,
By a metalorganic vapor phase epitaxy method, a crystal structure of a light emitting device composed of a nitride compound semiconductor layer was grown using ammonia and trimethylgallium as shown in FIG. First, n-AlN
The buffer layer 4 is grown at a temperature of 550 ° C., a thickness of 20 nm, and a temperature of 10 nm.
The n-GaN layer 5 was grown to 2.0 μm at 30 ° C.
l _{0. 1} Ga _{0. 9} the N layer 6 1.5 [mu] m, 50 nm undoped GaN layer _{7, p-Al 0. 1} Ga 0. 9 1.5μm the N layer 8
Then, the p-GaN cap layer 9 was sequentially grown to 0.5 μm.

A device structure composed of a nitride-based compound semiconductor layer having grooves formed in a substrate has a width of 800 μm and a length of 50.
They are independent of each other in the area of 0 μm. The crystal plane in that region grew to be almost vertical due to the formation of the groove. After that, the n-GaN layer 5 is partially formed by vapor phase growth of the SiO ₂ film, photolithography and dry etching.
Etching was performed as follows. Then, a mask was again formed by vapor phase growth of SiO ₂ film and photolithography, and p and n electrodes 10 and 11 were formed by electron beam evaporation as shown in FIG.

Finally, the sapphire substrate was polished to 100 μm and cleaved using the grooves formed before crystal growth to make chips. In this case, since the sapphire substrate has a hexagonal structure and has no cleavage, a good crystal plane cannot be obtained on the substrate, but the nitride-based compound semiconductor layer grows selectively and independently in the region formed by the groove. Therefore, when chips were formed, they could be separated without damaging the crystal plane.

In this light emitting device, a current of 25 mA flows at an applied voltage of 4 V, and blue spontaneous emission light is emitted. The light emission at that time was about 370 nm. Such a blue light emitting diode element was satisfactorily manufactured without damaging the nitride compound semiconductor crystal. As a result, the reliability and yield of the device are improved.

Further, a light emitting device structure in which chips were formed without electrodes was photoexcited using a nitrogen laser having a wavelength of 337 nm. The narrowing of the emission spectrum starts from around 150 kW / cm ^{2 at the} photoexcitation density of 170 kW / cm ^2.
Then, stimulated emission light with a very narrow spectrum was observed, confirming laser oscillation. This is because the crystal plane in contact with the groove is substantially vertical and a good resonator surface is formed by crystal growth on the substrate in which the groove is formed. In this example, the groove was formed by dry etching and dicer, but there is no problem if it is formed by forming the groove deep only by dry etching, and a similar light emitting element can be obtained.

(Embodiment 2) As shown in FIG.
800 μm in width and 5 in length on 0 μm sapphire C-plane substrate 1
For each area of 00 μm, the width is 5 with the dicer using the blade.
The groove 3 having a depth of 0 μm and a depth of 100 μm was formed. afterwards,
A selective growth region mask 12 as shown in FIG. 5 was formed in a region of 800 μm in width and 500 μm in length surrounded by the groove by vapor phase growth of SiO ₂ film and photolithography.

Then, a light emitting device structure made of a nitride compound semiconductor similar to that of Example 1 was selectively grown as shown in FIG. 6 using a mask. First, the p-AlN buffer layer 12 is grown at a growth temperature of 550 ° C. to 20 nm and a temperature of 1030 ° C.
The aN layer 13 was 2.0μm _{growth, p-Al 0. 1 Ga} 0. 9 N
The layer 14 is 1.5 μm thick and the undoped GaN layer 15 is 50 n thick.
_{m, n-Al 0. 1} Ga 0. 9 the N layer 16 1.5 [mu] m and n
The GaN cap layer 17 was sequentially grown to 0.5 μm. The crystal plane of the mask region was obtained by selective growth to obtain a nearly vertical crystal plane.

After that, as in Example 1, the p-GaN layer 13 was etched halfway as shown in FIG. 7 by vapor phase growth of the SiO ₂ film, photolithography and dry etching. Then, a mask was again formed by vapor phase growth of SiO ₂ film and photolithography, and n and p electrodes 11 and 10 were formed by electron beam evaporation as shown in FIG.

Finally, the sapphire substrate was polished to 100 μm and cleaved using the grooves formed before crystal growth to make chips. In the case of this element structure, since the crystal in the region forming the p-electrode is selectively grown, carriers hardly flow into the region near the vertical crystal plane in contact with the groove serving as the resonator. It has a structure with no end face excitation.

In this light emitting device, a current of 30 mA flows at an applied voltage of 4 V, and the wavelength is about 370 nm as in the first embodiment.
However, when the emission pattern is seen from the back surface of the sapphire substrate, no emission is observed in the region near the vertical crystal plane, and it is thought that the injected carriers are difficult to flow to that region. . In this way, by forming the mask of the selective growth region and selectively growing the crystal of the region where the p-electrode is formed, an end face non-excitation type laser structure can be realized. When the light-emitting device structure without this electrode was made into a chip and photoexcitation was performed using a nitrogen laser having a wavelength of 337 nm, narrowing of the emission spectrum started from around the photoexcitation density of 150 kW / cm ² as in Example 1. , its spectrum at 170kW / cm ² is observed a very narrow relaxation light was confirmed laser oscillation.

[0017]

According to the present invention, when a light emitting diode or a semiconductor laser made of a nitride-based compound semiconductor is manufactured, a crystal is selectively grown on a sapphire substrate in which a groove is formed in advance to form a crystal. Chips can be formed without damaging them, and reliability and yield can be improved. Also,
As a result of being able to obtain a nearly vertical crystal plane by selective growth using a groove, it is difficult to cleave, so that it is difficult to obtain a vertical crystal plane that becomes a resonator of a semiconductor laser. In a semiconductor, a good resonator structure can be easily manufactured without damaging the crystal.

[Brief description of drawings]

FIG. 1 is a perspective view of a sapphire substrate having first and second grooves formed therein.

FIG. 2 is a perspective view of a substrate on which a nitride-based compound semiconductor layer is crystal-grown after forming a groove.

FIG. 3 is a perspective view of a nitride-based light emitting device after dry etching.

FIG. 4 is a perspective view of a nitride-based light emitting device after formation of p and n electrodes.

FIG. 5 is a perspective view of a sapphire substrate on which a selective growth region mask is formed after forming a groove.

FIG. 6 is a perspective view of a nitride-based light emitting device grown on a sapphire substrate on which a selective growth region mask is formed.

FIG. 7 is a perspective view of a nitride-based light emitting device after dry etching.

FIG. 8 is a perspective view of a nitride-based light emitting device after formation of p and n electrodes.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sapphire substrate, 2 ... 1st groove | channel formed by dry etching, 3 ... 2nd groove | channel formed with the dicer using a blade, 4 ... n-AlN buffer layer, 5 ... n-Ga
N _{layer, 6 ... n-Al 0.} 1 Ga 0. 9 N layer, 7 ... undoped G
aN _{layer, 8 ... p-Al 0.} 1 Ga 0. 9 N layer, 9 ... p-GaN
layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Akamatsu 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Minoru Minagawa 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory

Claims (5)

[Claims] 1. A step of forming a groove in a sapphire substrate, a step of selectively crystallizing a nitride-based compound semiconductor light-emitting device on the grooved substrate, and using the groove to form individual light-emitting devices. A method for manufacturing a nitride-based compound semiconductor light-emitting device, comprising the step of separating. 2. The method for manufacturing a nitride-based compound semiconductor light emitting device according to claim 1, wherein the groove is formed by at least one of wet etching, dry etching and dicing. 3. The method for manufacturing a nitride-based compound semiconductor light emitting device according to claim 1, wherein the groove is formed with a plurality of different depths. 4. The nitride-based device according to claim 1, which is formed by forming a selective growth region mask on the grooved sapphire substrate and then crystal-growing a device structure including a nitride-based compound semiconductor layer. Compound semiconductor light emitting device. 5. The light emitting device according to claim 1, wherein the light emitting element is made of at least InN, GaN, GaInN, and the confinement layer is at least AlN, AlGaN, AlInN, AlGa.
A nitride-based compound semiconductor light emitting device made of InN.