JP5182758B2 - Method and apparatus for producing nitride single crystal - Google Patents

Description

  The present invention relates to a method for producing a single crystal such as aluminum nitride (AlN), and more particularly to a method and apparatus for producing a nitride single crystal that achieves a long and large diameter aluminum nitride.

Aluminum nitride semiconductors are expected as deep ultraviolet laser diodes and high-efficiency, high-frequency electronic devices. As a substrate for growing this semiconductor, an aluminum nitride single crystal is optimal, and therefore, development of aluminum nitride single crystal is under development.
A feature of the aluminum nitride single crystal is that it has a very high thermal conductivity of 290 Wm ⁻¹ K ⁻¹ , which is very advantageous for dissipating heat generated during device operation.

The aluminum nitride single crystal is produced by the flux method in the solution method, the metal-organic vapor phase epitaxy (MOVPE) in the vapor phase method, the hydride vapor deposition method (Hydride Vapor Phase Epitaxy, HVPE) and sublimation methods. Among these, the sublimation method is a powerful method for producing a bulk crystal because the growth rate is generally high. This sublimation method is a method of producing a single crystal by sublimating aluminum nitride as a raw material and recondensing it in a temperature range lower than the sublimation temperature.
In particular, the present application relates to a sublimation method (an improved Rayleigh method) using a seed substrate.

FIG. 2 shows a conventional nitride production apparatus 1 that makes it possible to produce a nitride single crystal by a sublimation method using a seed substrate.
A conventional nitride manufacturing apparatus 1 includes a growth vessel 2, a raw material vessel 14 disposed on the inner bottom of the growth vessel 2, and a susceptor 3 attached to the upper portion of the growth vessel 2. A raw material 22 such as aluminum nitride powder is accommodated in the bottom of the raw material container 14.
A seed substrate 23 is attached to the lower surface of the susceptor 3 so as to face the raw material 22. A heating means 7 by a resistance heating method for heating the raw material 22, the susceptor 3, and the seed substrate 23 disposed inside the growth container 2 is provided along the outer periphery of the growth container 2 main body. The growth vessel 2 and the heating means 7 are surrounded by a chamber 8. A gas introducing portion 5 such as nitrogen gas and a pressure adjusting valve 6 are formed in the ceiling portion of the chamber 8 so that the inside of the chamber 8 can be adjusted to a predetermined gas pressure.

When producing a nitride single crystal, first, a carry-in port (not shown) provided in the chamber 8 is opened, the raw material 22 is set at the bottom of the raw material container 14, the carry-in port is closed, and the chamber 8 is sealed. Next, the inside of the chamber 8 is evacuated by the pressure regulating valve 6, and then a process gas such as nitrogen gas is introduced into the growth vessel 2 by the gas introduction unit 5 to adjust the pressure.
And the raw material 22 and susceptor in the growth container 2 main body are used using the heating means 7 so that the lower part of the raw material container 14 in which the raw material 22 is arranged is higher in temperature than the susceptor 3 in which the seed substrate 23 is arranged. 3. The seed substrate 23 is heated. The raw material 22 sublimated by heating and decomposed and vaporized grows as a nitride single crystal 24 by crystal growth on the seed substrate 23 in a nitrogen gas atmosphere.

As a method for producing an aluminum nitride single crystal by an improved Rayleigh method, Patent Document 1 discloses that a mixed powder of nitride and oxide is lower than the sublimation temperature of nitride by utilizing the reaction of nitride and oxide. A method is described in which vaporization is performed by heating at a temperature, and a nitride single crystal is grown on the substrate in this nitrogen atmosphere.
Patent Document 2 describes a method in which a silicon carbide (SiC) single crystal is used as a seed substrate and an aluminum nitride single crystal is grown thereon.
In Non-Patent Document 1, an aluminum nitride single crystal is grown on a SiC substrate to a single crystal length of 200 to 400 nm by MOCVD, and grown at a growth rate of 10 to 30 μm / h in the first stage. Thereafter, a method is described in which the temperature is increased at the second stage to grow at a growth rate of 70 μm / h.
Japanese Patent Laid-Open No. 10-53495 JP-T-2002-527343 Journal of Crystal Growth 281 (2005) 68-74

  However, in the above-described conventional method for producing an aluminum nitride single crystal by the sublimation method, the raw material container 14 is filled with the raw material 22 and the single crystal is grown by the batch method. In this case, since the size of the grown crystal is determined by the amount of raw material to be filled, there is a limit to increasing the diameter and length of the crystal. In order to produce a large-diameter crystal, it has been necessary to repeatedly perform crystal growth by a batch method, so that there has been a problem that much labor is required.

The method for producing an aluminum nitride single crystal of the present invention includes:
A method for producing a nitride single crystal by a sublimation method in which a nitride single crystal is grown by sublimating a raw material and re-condensing nitride vapor in a growth vessel,
A raw material sublimation vessel in communication with the growth vessel;
A feeder provided on the upper surface of the raw material sublimation container;
A raw material hopper provided on the upper surface of the feeder and storing the raw material;
Continuously supplying the raw material from the feeder to the raw material sublimation container;
Sublimating the raw material in the raw material sublimation container to generate nitride vapor;
Transporting the nitride vapor into the growth vessel;
The nitride single crystal is continuously grown in the growth portion of the growth vessel.

  The nitride is preferably aluminum nitride.

  It is preferable that the raw material hopper includes a gas introduction part and a pressure adjusting valve, and controls the pressure in the raw material hopper to be equal to the pressure in the growth vessel.

The apparatus for producing a nitride single crystal of the present invention comprises:
A growth vessel,
A raw material sublimation vessel in communication with the growth vessel;
A feeder provided on the upper surface of the raw material sublimation container;
A raw material hopper provided on the upper surface of the feeder and storing raw materials;
By continuously supplying the raw material from the feeder to the raw material sublimation container and transporting the nitride vapor sublimated in the raw material sublimation container into the growth container, continuously in the growth part of the growth container. A nitride single crystal can be grown.

  The raw material hopper of the nitride single crystal production apparatus preferably includes a gas introduction part and a pressure regulating valve, and controls the pressure in the raw material hopper to be equal to the pressure in the growth vessel.

The nitride single crystal manufacturing apparatus according to the present invention is provided with a raw material sublimation container communicating with the growth container in addition to the growth container, and a feeder and a raw material hopper for supplying the raw material to the raw material sublimation container.
According to the apparatus of the present invention configured as described above, the raw material is continuously supplied from the feeder to the raw material sublimation container, and the nitride vapor sublimated in the raw material sublimation container is transported to the growth container to grow the growth container. A nitride single crystal is continuously grown on the part. Therefore, it is possible to perform stable crystal growth for a long time, and it is easy to increase the length and diameter of the aluminum nitride single crystal.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of an apparatus for producing an aluminum nitride single crystal according to the present invention. In FIG. 1, the same elements as those of the conventional apparatus shown in FIG.

The nitride single crystal manufacturing apparatus 1 of the present embodiment includes a growth vessel 2, a raw material sublimation vessel 11 communicating with the growth vessel 2, a raw material hopper 12 containing the raw material 21, and the raw material 21 from the raw material hopper 12. A feeder 13 to be supplied and a shutter 12B provided below the feeder 13 are provided. The raw material sublimation container 11 is connected laterally to the side wall of the growth container 2 via a connecting portion (flange) 11A.
A susceptor 3 is disposed in the upper center (ceiling) of the growth vessel 2, and a nitride single crystal 24 is grown on a seed substrate 23 attached to the lower surface of the susceptor 3. The susceptor 3 is a plate made of graphite or the like, and the seed substrate 23 for crystal growth is, for example, a 6H—SiC or aluminum nitride single crystal plate having a diameter of 25 mm.

  The growth vessel 2 is provided with a heating means 7 by a resistance heating method for heating the susceptor 3 and the seed substrate 23 arranged inside the growth vessel 2. Similarly, the raw material sublimation container 11 is provided with a heating means 18 by a resistance heating method for heating the raw material 22 arranged inside the raw material sublimation container 11. Such heating means 7 and 18 are not particularly limited, and conventionally known ones can be used. For example, carbon, tungsten, or the like can be used as the heater material. The growth container 2, the raw material sublimation container 11, and the heating means 7 and 18 are surrounded by the chamber 8.

A gas introducing portion 15 such as nitrogen gas and a pressure adjusting valve 16 are provided on the upper side of the raw material hopper 12 so that the internal pressure of the raw material hopper 12 can be controlled to be equal to the internal pressure of the chamber 8. . The bottom part of the raw material hopper 12 is connected to the upper part of the raw material sublimation container 11 through a connecting part (flange) 12A.
Inside the raw material sublimation container 11, a raw material container 14 having an opening 14 a at the top is arranged, and the raw material 21 supplied from the feeder 13 is received by the raw material container 14.
An introduction part 4 such as nitrogen gas is formed at the bottom of the growth container 2, and a gas introduction part 17 such as nitrogen gas is formed at the tip of the raw material sublimation container 11. A gas introduction part 5 and a pressure regulating valve 6 are provided. Thus, the inside of the chamber 8 can be individually adjusted to a predetermined gas pressure.

Next, the manufacturing method of the aluminum nitride single crystal 24 using the manufacturing apparatus 1 of the present invention will be described.
First, the inlet 12a provided in the raw material hopper 12 is opened, and the raw material 21 such as aluminum nitride powder is accommodated in the raw material hopper 12, and then the inlet 12a is closed to seal the raw material hopper 12.
Next, the shutter 12 </ b> B is opened, and the raw material 21 is supplied from the feeder 13 to the raw material container 14. Next, the inside of the chamber 8 is evacuated from a vacuum pump connected to the pressure regulating valve 6, and then a process gas such as nitrogen gas is supplied from the gas introduction parts 4, 5, 17 to the internal space of the growth vessel 2 and the raw material sublimation vessel 11. To adjust the pressure. The pressure here can be set to 1 to 1000 Torr, more preferably 10 to 760 Torr.
The raw material container 14 (raw material part) in which the raw material 22 is arranged is heated using the heating means 7 and 18 so that the temperature of the raw material container 14 (raw material part) is higher than that of the susceptor 3 (growth part) in which the seed substrate 23 is arranged. The susceptor 3 and the seed substrate 23 are heated. Here, the temperature of a raw material part can be set to 1800-2500 degreeC, More preferably, it can be set to 2000-2400 degreeC. Moreover, the temperature of a growth part can be set to 1700-2400 degreeC, More preferably, it can be set to 1800-2300 degreeC.

  During heating, the gas in the growth vessel 2 is exhausted from the pressure regulating valve 6 on the upper surface of the chamber 8, and the gas is supplied from the gas introduction parts 4, 5, 17 into the growth vessel 2 and the raw material sublimation vessel 11. As a result, the gas pressure and flow rate in the growth vessel 2 and the raw material sublimation vessel 11 are appropriately adjusted. The gas introduction part 15 and the pressure adjusting valve 16 provided in the raw material hopper 12 control the pressure in the chamber 8 and the internal pressure of the raw material hopper 12 equally.

  The raw material vapor that has been sublimated by heating and decomposed and vaporized is transported to the growth vessel 2 communicating with the raw material sublimation vessel 11. The transportation is performed by the gas introduced from the gas introduction unit 17. The transported raw material vapor grows as an aluminum nitride single crystal 24 under a nitrogen gas atmosphere on the seed substrate 23 disposed on the lower surface of the susceptor 3 disposed on the growth vessel 2. In the present invention, during the crystal growth, in order to control the crystallization speed of the crystal growth on the seed substrate 23, temperature control is performed to optimize the temperature of the susceptor 3 and the sublimation speed of the sublimation gas sublimated from the raw material 22. .

In the present invention, during this time, the raw material 22 can be appropriately supplied by the feeder 13 as appropriate.
Further, during the production of the nitride single crystal 24, the raw material hopper 12 is replenished by closing the shutter 12B between the raw material hopper 12 and the raw material sublimation vessel 11 and opening the carry-in port 12a. can do. The internal pressure of the raw material container 2 and the raw material sublimation container 11 is not affected by opening the carry-in port 12a after closing the shutter 12B. When supplying the replenished raw material 21 with the feeder 13, the inside of the raw material hopper 12 is individually evacuated and then the shutter 12B is opened, so that the raw material 21 is supplied without affecting the vacuum state of the raw material sublimation container 11. Since it can be supplied to the container 14, semi-permanently stable crystal growth is possible.
By the above method, the raw material 21 accommodated in the raw material hopper 12 is continuously supplied to the raw material container 14, and the aluminum nitride single crystal 24 grown on the deposition surface of the seed substrate 23 can be continuously grown semipermanently. Become.

  An aluminum nitride single crystal 24 was produced on one surface of the seed substrate 23 using the apparatus having the configuration shown in FIG. Table 1 below shows the experimental conditions and experimental results for this production.

  Under these experimental conditions, Examples 1 to 4 are examples according to the continuous method of the present application. Comparative Examples 1 to 4 are examples using the conventional apparatus shown in FIG.

<Example 1>
An aluminum nitride single crystal is produced under the conditions of Example 1 shown in Table 1 while using 6H-SiC with a diameter of 25 mm as a seed substrate and continuously supplying the raw material quantitatively using the manufacturing apparatus shown in FIG. This was taken as Example 1. The experiment time was 300 hours.
<Example 2>
Example 2 was performed in the same manner as in Example 1 except that an aluminum nitride single crystal was produced under the conditions of Example 2 shown in Table 1.
<Example 3>
Example 3 was performed in the same manner as in Example 1 except that an aluminum nitride single crystal was produced under the conditions of Example 3 shown in Table 1. As the seed substrate, aluminum nitride having a diameter of 25 mm was used. The experiment time was 100 hours.
<Example 4>
Example 4 was performed in the same manner as in Example 3 except that an aluminum nitride single crystal was produced under the conditions of Example 4 shown in Table 1.

<Comparative Example 1>
An aluminum nitride single crystal was produced under the conditions of Comparative Example 1 shown in Table 1 using 6H—SiC having a diameter of 25 mm as a seed substrate and using the manufacturing apparatus shown in FIG. . The experiment time was 100 hours.
<Comparative example 2>
Comparative Example 2 was performed in the same manner as Comparative Example 1 except that an aluminum nitride single crystal was produced under the conditions of Comparative Example 2 shown in Table 1.
<Comparative Example 3>
Comparative Example 3 was made in the same manner as Comparative Example 1 except that an aluminum nitride single crystal was produced under the conditions of Comparative Example 3 shown in Table 1. As the seed substrate, aluminum nitride having a diameter of 25 mm was used. The experiment time was 15 hours.
<Comparative example 4>
Comparative Example 4 was made in the same manner as Comparative Example 3 except that an aluminum nitride single crystal was produced under the conditions of Comparative Example 4 shown in Table 1.

  In Examples 1 and 2, for 300 hours, and in Examples 3 and 4, while continuously feeding the raw materials contained in the raw material hopper, if necessary, the raw materials are added to the raw material hopper. However, a growth experiment was conducted. As a result, it was possible to produce a bulk aluminum nitride single crystal stably for a long time. The aluminum nitride single crystal achieved a diameter expansion of 5 mm or more with respect to the seed substrate.

  In Comparative Examples 1 to 4, growth experiments were performed using the apparatus shown in FIG. The raw material was filled with 500 g. The experiment time in the comparative example is the time until the remaining 50 g of the raw material used as a guide for stopping the experiment is cut. Under either condition, the diameter of the seed substrate could not be increased by 5 mm or more. In order to realize an enlargement of the diameter exceeding 5 mm, a plurality of experiments are required, and it takes a lot of time and labor for the setting of the experiment and the temperature lowering process, which is not efficient.

  As described above, in the growth of aluminum nitride by the sublimation method, by using the apparatus shown in FIG. 1, the raw material inside the raw material hopper is continuously supplied quantitatively from the feeder to perform stable crystal growth for a long time. I was able to. Therefore, it is easy to increase the length and diameter of the aluminum nitride single crystal.

It is the schematic block diagram which showed typically the manufacturing apparatus of the nitride single crystal of 1st Embodiment which concerns on this invention. It is the schematic block diagram which showed typically an example of the manufacturing apparatus of the conventional nitride single crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus of nitride single crystal, 2 ... Growth container, 3 ... Susceptor, 4 ... Gas introduction part, 5 ... Gas introduction part, 6 ... Pressure control valve, 7 ... Heating apparatus, 8 ... Chamber, 11 ... Raw material sublimation Container, 11A: Connecting portion, 12: Raw material hopper, 12a: Loading port, 12A ... Connecting portion, 12B ... Shutter, 13 ... Feeder, 14 ... Raw material container, 14a ... Opening portion, 15 ... Gas introducing portion, 16 ... Pressure adjustment Valve: 17 ... Gas introduction part, 18 ... Heating device, 19 ... Gas introduction part, 21, 22 ... Raw material, 23 ... Seed substrate, 24 ... Nitride single crystal.

Claims (5)

A method for producing a nitride single crystal by a sublimation method in which a nitride single crystal is grown by sublimating a raw material and re-condensing nitride vapor in a growth vessel,
A raw material sublimation vessel in communication with the growth vessel;
A feeder provided on the upper surface of the raw material sublimation container;
A raw material hopper provided on the upper surface of the feeder and storing the raw material;
Continuously supplying the raw material from the feeder to the raw material sublimation container;
Sublimating the raw material in the raw material sublimation container to generate nitride vapor;
Transporting the nitride vapor into the growth vessel;
And a nitride single crystal is continuously grown in the growth part of the growth vessel.   The method for producing a nitride single crystal according to claim 1, wherein the nitride is aluminum nitride.   The nitride single crystal according to claim 1 or 2, wherein the raw material hopper includes a gas introduction part and a pressure adjusting valve, and controls the pressure in the raw material hopper to be equal to the pressure in the growth vessel. Production method. A growth vessel,
A raw material sublimation vessel in communication with the growth vessel;
A feeder provided on the upper surface of the raw material sublimation container;
A raw material hopper provided on the upper surface of the feeder and storing raw materials;
By continuously supplying the raw material from the feeder to the raw material sublimation container and transporting the nitride vapor sublimated in the raw material sublimation container into the growth container, continuously in the growth part of the growth container. An apparatus for producing a nitride single crystal, wherein the nitride single crystal can be grown. The apparatus for producing a nitride single crystal according to claim 4 , wherein the raw material hopper includes a gas introduction part and a pressure adjusting valve, and controls the pressure in the raw material hopper to be equal to the pressure in the growth vessel. .

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