JPH09194204A - Method for manufacturing aluminum nitride and semiconductor light emitting device - Google Patents

Abstract

(57) Abstract: A method for producing a high-purity aluminum nitride film at low temperature is provided. SOLUTION: A 5N metal Al 104 is set in an ECR device, and ECR plasma is generated while introducing a nitrogen gas 109. The temperature at this time is 200 ° C. EC
Al and N are grown on the GaAs substrate by the R plasma, and the AlN film 107 can be manufactured. Like this ECR
Since high-purity metallic Al is used in the AlN film manufacturing method using plasma, a high-purity AlN film can naturally be grown, and the film can be manufactured without the need for high-temperature growth as in the MOVPE method. Is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing aluminum nitride and a semiconductor light emitting device.

[0002]

2. Description of the Related Art Aluminum nitride (hereinafter referred to as AlN) is widely used as an insulating film. Further, since bulk AlN has good thermal conductivity, it is also used for a substrate on which a semiconductor element having heat dissipation is mounted.

A conventional AlN film has been deposited on a substrate by using AlN as a target and by a sputtering method using argon ions. The temperature at this time is from room temperature to about 400 ° C. As described above, although the AlN film can be deposited at a relatively low temperature by the sputtering method, the purity of the target AlN is not high, so that the deposited AlN film is inevitable.
A highly pure film could not be obtained.

There is also a method of growing an AlN film on a sapphire substrate by the MOVPE method (Japanese Patent Laid-Open No. 2-2).
No. 29476, Japanese Patent Laid-Open No. 4-297023). In this method, trimethylaluminum gas and ammonia gas are introduced into a reaction furnace, heated to 1080 ° C., and thermally decomposed to grow an AlN film on a sapphire substrate. The grown AlN film does not contain impurities as in the sputtering method, but requires a high temperature of 1000 ° C. or higher for growth.

[0005]

As described above, the conventional Al
For the growth of the N film, there are cases in which a high-purity one cannot be obtained by the sputtering method and the grown film is damaged. Further, according to the MOVPE method, it is necessary to grow at a high temperature.

Therefore, an object of the present invention is to provide a method of manufacturing an AlN film which can be grown at a relatively low temperature and which has a high purity.

[0007]

In order to achieve the above object, the AlN film manufacturing method of the present invention uses ECR plasma. High-purity metal Al and nitrogen gas are used as the raw material.

Further, the method of manufacturing the AlN film is applied to coating of the end face of a resonator of a semiconductor light emitting device such as a semiconductor laser.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

(Embodiment 1) For growth of an AlN film, EC
R (Electron Cyclotron Resonance) plasma is used. The reaction formula is Al (metal) + N2 → AlN.

Metallic aluminum is used as a raw material of Al. The reason for this is high purity (five nine (5
N)) is easily available, and high-purity A
This is because the 1N film can be grown.

The ECR device shown in FIG. 1 is shown. The configuration of the device is the plasma generation chamber 1 in which the electromagnet coil 103 is installed.
A nitrogen gas 109 and an argon gas 110 are connected to 02. A magnetron 101 for generating plasma is connected to the plasma generation chamber 103.
Further, the thin film deposition chamber 108 is connected to the plasma generation chamber,
An Al target 104 is installed at the connecting portion. The thin film deposition chamber 108 is connected to a vacuum pump.

A 5N metallic Al 104 is set in this apparatus, and a plasma is generated in the plasma generation chamber 102 while introducing nitrogen gas (flow rate: 5000 ccm). The temperature at this time is 200 ° C. By ECR plasma, A
l and N grow on the GaAs substrate 107, and an AlN film can be manufactured. When examining the flatness of the grown AlN film,
As shown in FIG. 2, it was extremely flat. When ECR is used, the flatness (unevenness) is within about 4 nm, and this unevenness is about 25 nm in the sputtering method (FIG. 2).
(A)). The reason for this is not clear, but in the case of ECR, the directivity is strong, and it is considered that the grown film also becomes flat because Al and N fly from the vertical direction in a neat line to the substrate instead of in an oblique direction. To be

Thus, AlN using ECR plasma
Since high-purity metal Al is used in the film production, not only can a high-purity AlN film be grown, but MOVPE
Since it does not require growth at a high temperature as in the method, it does not require a high temperature apparatus and does not use a reaction gas (TMA or the like), so that there is no intermediate product such as an Al compound. FIG.
As described above, when the growth temperature is in the range of 0 ° C. to 600 ° C., a high quality film having sufficient purity and flatness can be obtained. 550-
In the range of 600 ° C, the adhesion to the substrate is slightly reduced,
In the range of 0 ° C to 550 ° C, the adhesion to the substrate was good and the stress applied to the substrate was small. Further, since it is ECR, it is low in damage, and the activation rate of nitrogen plasma is high, so that the growth rate is not small and the AlN film can be efficiently grown.

FIG. 2 (b) shows a summary of these characteristics.
Shown in In the case of ECR, the purity of the deposited film is about 6N. Energy during deposition is 10 to 20e
A small amount of V causes little damage to the deposited film. There is no damage to the thin film due to charge-up, the surface roughness is small, and the flatness is excellent.

(Embodiment 2) An embodiment in which the AlN film described in Embodiment 1 is applied to coating of the end face of a semiconductor laser will be described.

FIG. 4 shows an ECR device similar to that shown in FIG.
Here, a semiconductor laser bar (a state before being cut into each laser chip) is used as a sample. In this apparatus, a semiconductor laser cut out from the wafer into a bar state is installed. AlN is formed on the end face of the laser under the conditions described in the first embodiment.
The film is grown at 77 nm.

FIG. 5 shows a cross-sectional view of a laser having an AlN film grown on the front end face (laser emission face side) of the semiconductor laser. On the AlN film, a SiON film is deposited with a thickness of 101, 6 nm. This is because the front side reflectance is adjusted by the SiON film. Here, the reflectance is set to 10% by depositing a SiON film.

When the end face is covered with the AlN film in this way, the end face of the laser is not oxidized and the operating current of the laser can be prevented from increasing. Moreover, since the AlN film has high thermal conductivity and excellent heat dissipation, an operating current can be prevented.
Further, even during the growth, the laser end face is hardly damaged, and the optical output is not deteriorated by the damage. Therefore, a highly reliable semiconductor laser can be obtained.

The further grown AlN film is flat and the reflectance at the end face of the laser can be accurately controlled.
FIG. 6 shows the reflectance of the laser with respect to the film thickness of AlN. According to this, it can be seen that the reflectivity greatly varies depending on the AlN film, but since the AlN film is flat and the film thickness is excellently controlled, the reflectivity can be easily adjusted.

Metal Al and nitrogen gas were used for growth of the AlN film, but by further adding oxygen gas, an AlN film most suitable for coating the end face can be manufactured. The added oxygen gas is 1 against the nitrogen gas (5000 ccm).
It is 50 ccm of / 100. This reaction formula is
+ Nitrogen gas + Oxygen gas → AlNO film. The AlN film thus grown contains oxygen. This membrane is
The "warp" with respect to the GaAs substrate is reduced. That is, as shown in FIG. 7, the warp was large when oxygen was absent, and therefore the stress exerted on the substrate was large. However, by adding oxygen, the warp is reduced and the stress applied to the substrate can be relieved considerably. it can.

Finally, the operating current of the semiconductor laser is compared between the case where the AlN film is deposited on the end face of the semiconductor laser by magnetron sputtering and the case where the AlN film is deposited by ECR as in this embodiment. There is. It can be seen that the ECR method as in this embodiment causes less increase in operating current with time and has higher reliability.

(Embodiment 3) A described in Embodiment 1
As an application of the AlN film formed by the manufacturing method of 1N,
A hologram unit in which a semiconductor laser and a light receiving element are integrally formed will be described.

A configuration perspective view of this hologram unit is shown in FIG. A laser chip 902 is arranged on a silicon substrate 901, and a laser chip 902, photodiodes 903a and 903b for detecting an optical signal, a micro mirror 904 for reflecting laser light from the laser chip, and a photodiode for monitoring laser output. 905 is integrally configured. As a result, the size and thickness are reduced. In this way, the laser unit forms the concave portion on the silicon substrate 901 and arranges the semiconductor laser chip 902 in the concave portion. The light emitted from the laser 902 is
A micro mirror 904 formed on the silicon substrate 901 and having an angle of 45 degrees with respect to the surface of the silicon substrate.
Is emitted upward. The micro mirror 904 is formed by utilizing the (111) plane of silicon. (11
This is because the surface 1) is easily obtained by anisotropic etching and is a chemically stable surface, so that it is easy to obtain an optically flat surface.

However, when the silicon (100) plane is used, the (111) plane forms an angle of 54 degrees with the (100) plane, so that the (110) plane is oriented in the <110> direction by 9 degrees.
By using a substrate inclined at an angle of 45 degrees, an angle of 45 degrees can be obtained. The angle of the surface facing the micromirror is 63 degrees, and a monitoring photodiode 905 for monitoring the light output from the laser chip is formed on this surface.

The surface of the micro mirror 904 is flat silicon, but it does not absorb laser light, and in order to improve the light utilization efficiency, a metal such as gold, which has high reflection efficiency and does not absorb laser light, is deposited. It is preferable to reduce the loss of light.

As described above, by using the laser unit, the optical disc can be made smaller and thinner, and also in manufacturing, the laser chip is formed in the concave portion on the surface of the silicon substrate where the photodiode and the micromirror are formed. Therefore, the process can be simplified and the yield can be increased.

FIG. 1 is a sectional view of the laser unit taken along the line ab.
0 is shown. Although not shown in FIG. 9, FIG.
As described above, the AlN film is formed under the laser chip (semiconductor laser 1002) by the method of the first embodiment. The AlN film is formed on the silicon substrate 1001 as shown in FIG. Further, as shown in FIG. 6C, instead of forming only the AlN film on the silicon substrate, the AlN film 1003 and the Al film may be alternately laminated. The following effects can be obtained by forming an AlN film under the semiconductor laser and using this AlN film as a heat radiator.

When the AlN film or the AlN / Al laminated film is not used as a heat radiator, that is, when the semiconductor laser is directly mounted on the silicon substrate, the thermal resistance is 70 ° C./W, which is large. Too long, wavelength 63 of AlGaInP system
A red laser in the 0 to 680 nm band cannot be mounted. This is because the laser chip will not immediately oscillate due to thermal resistance even after mounting.

On the other hand, when an AlN film is formed on a silicon substrate and a laser chip is mounted on this film, that is, when the AlN film is used as a radiator, the thermal resistance is 35 ° C./W. , Half of the case of mounting directly on a silicon substrate. As a result, AlGaInP-based 630-680 nm
With a band, especially a 650 nm band red laser, it was possible to secure reliability at 80 ° C. and 5 mW.

AlN is excellent in heat dissipation and has a thermal conductivity of about 200 W / m · K. However, in order to maintain a high thermal conductivity, it is necessary to avoid mixing of impurities. In particular, if oxygen is mixed in, the thermal conductivity will be significantly reduced. Embodiment 1
Since the ECR film forming apparatus can use metal Al of high purity (5 to 6 N) as a raw material, it has a great advantage when used as a heat radiator in a hologram unit. Further, it is very different from ordinary magnetron sputtering in that a dense film can be formed by the ECR film forming apparatus. This is because the denseness of the film also greatly affects the thermal conductivity.

(Fourth Embodiment) In the third embodiment, an AlN film is formed on a silicon substrate to serve as a heat radiator to enhance the heat radiation performance of the laser. An embodiment of a unit using a so-called liquid cooling method in which the inside of the unit is filled with an insulating liquid and cooled in order to further improve the cooling property will be described with reference to FIG.

The hologram unit is mounted on a package 1100 made of plastic or the like, and the laser 1
The hologram element 1105 is placed on the exit surface side of 102.
Hologram element 1105 and plastic package 11
In the space between 00, a fluorocarbon liquid 1104
Fill. Here, C4F10 was used. The fluorocarbon-based liquid has a small absorption of light in the wavelength band of the AlGaInP-based red laser, is inert, incombustible, and insulative, and is suitable as a cooling liquid.

By this method, the heat generated by driving the semiconductor laser can be efficiently dissipated, and the deterioration of the characteristics of the semiconductor laser, especially the deterioration of reliability can be prevented.

As described above, when the AlN heat radiator and the liquid cooling are used at the same time, the heat radiation effect of the semiconductor laser is further enhanced, which is very effective in increasing the laser output.

Finally, the thermal conductivity of the material is described as a reference value. Si ・ ・ ・ 120W / m ・ K, AlN ・ ・ ・ 2
00 (270 depending on the literature), Al2O3 ... 25, GaAs ... 5
4, SiO2 ・ ・ ・ 1, SiC ・ ・ ・ 270.

[0037]

As described above, according to the present invention, an AlN film having a relatively low temperature, high purity and high flatness can be easily grown.

When this AlN film is used for the end face of a semiconductor laser, oxidation of the end face is prevented and the heat dissipation characteristics are good, so that a highly reliable semiconductor laser with a small operating current can be realized.

Further, an AlN film is used as a heat radiator on a silicon substrate to enhance the heat radiation performance of a laser having poor heat radiation characteristics, thereby suppressing an increase in the threshold current of the laser and realizing high light output. Is. Furthermore, liquid cooling can enhance this effect.

[Brief description of the drawings]

FIG. 1 is a structural sectional view of an ECR device.

FIG. 2 is a sectional view of an AlN film grown on a GaAs substrate by the ECR method.

FIG. 3 is a characteristic diagram showing the relationship between the deposition temperature of ECR method and the refractive index.

FIG. 4 E when a semiconductor laser is installed in an ECR device
Illustration of CR device

FIG. 5 is a structural perspective view in the cavity direction of a semiconductor laser in which an AlN film is grown on an end face.

FIG. 6 is a characteristic diagram illustrating the relationship between the film thickness of an AlN film grown on the end surface and the reflectance of a semiconductor laser.

FIG. 7 is a characteristic diagram showing the relationship between the amount of oxygen added and stress.

FIG. 8 is a characteristic diagram showing an operating current of a semiconductor laser whose end face is coated by using ECR.

FIG. 9 is a configuration perspective view of a hologram unit according to a third embodiment.

FIG. 10 is a configuration cross-sectional view of a hologram unit according to a third embodiment.

FIG. 11 is a cross-sectional view of the configuration of a hologram unit that is cooled by liquid

[Explanation of symbols]

 100 semiconductor laser 101 magnetron 102 plasma generation chamber 103 electromagnet coil 104 Al target 105 RF power supply 106 ECR plasma 107 sample 108 thin film deposition chamber 109 nitrogen gas 110 argon gas

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhito Kumabuchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (15)

[Claims] 1. A method for producing an aluminum nitride, wherein an AlN film is produced by ECR plasma using metal Al and nitrogen gas. 2. The method for producing aluminum nitride according to claim 1, wherein oxygen is added. 3. The method for producing aluminum nitride according to claim 1, wherein the reaction temperature is 0 ° C. to 600 ° C. 4. The method for producing aluminum nitride according to claim 1, wherein the reaction temperature is 0 ° C. to 500 ° C. 5. The method for producing aluminum nitride according to claim 1, wherein Al having a purity of 5N or higher is used. 6. A semiconductor light emitting device having an aluminum nitride film on an end face of a resonator. 7. The semiconductor light emitting device according to claim 6, wherein the aluminum nitride film is grown by an ECR method. 8. The semiconductor light emitting device according to claim 7, wherein oxygen is added to the aluminum nitride film. 9. The semiconductor light emitting device according to claim 6, wherein an aluminum nitride film is formed on a light emitting end face. 10. The semiconductor light emitting device according to claim 6, wherein a silicon oxide film is formed on the AlN film. 11. The semiconductor light emitting device according to claim 6, wherein Al having a purity of 5N or higher is used. 12. A semiconductor light emitting device comprising a substrate, a semiconductor light emitting element provided in a recess of the substrate, and an AlN film formed immediately below the semiconductor light emitting element in the recess. 13. The semiconductor light emitting device according to claim 12, wherein the semiconductor light emitting element is a semiconductor laser, and its emission wavelength is in the 630 to 680 nm band. 14. The semiconductor light emitting device according to claim 12, wherein a film having a laminated structure of an AlN film and an Al film is used. 15. A semiconductor light emitting device, comprising: the semiconductor light emitting device according to claim 12, 13 or 14; and a package that houses the light emitting device, wherein the package is sealed with a cooling liquid.