WO2006095536A1

WO2006095536A1 - Method of growing single crystal and single crystal growing apparatus

Info

Publication number: WO2006095536A1
Application number: PCT/JP2006/302409
Authority: WO
Inventors: Katsuhiro Imai; Makoto Iwai
Original assignee: Ngk Insulators, Ltd.
Priority date: 2005-03-04
Filing date: 2006-02-07
Publication date: 2006-09-14
Also published as: JPWO2006095536A1; JP4919949B2

Abstract

Growing of a single crystal from flux (8) containing at least an alkali or alkaline earth metal is carried out by the use of crucible (25) for accommodating the flux (8), cover (20) for the crucible (25), a pressure vessel for accommodating the crucible (25) and enclosing an atmosphere and flux metal vapor absorbing material (19) disposed inside the pressure vessel and outside the crucible (25).

Description

Specification

TECHNICAL FIELD The present invention relates to a method for growing a single crystal and a single crystal growing apparatus.

The present invention relates to a method and apparatus for growing a nitride single crystal by a so-called Na flux method.

Background art

Gallium nitride thin film crystals are attracting attention as an excellent blue light-emitting device, put into practical use in light-emitting diodes, and expected as a blue-violet semiconductor laser device for optical pickups. For example, Jpn. J. Appl. Phys. Vol. 42, (2003) page L4-L6 is a method for growing a gallium nitride single crystal by the Na flux method. The pressure is 50 atmospheres, and when using a mixed gas atmosphere of 40% ammonia and 60% nitrogen, the total pressure is 5 atmospheres.

Further, for example, in Japanese Patent Laid-Open No. 2 02-02-2 9 3 6 96, the pressure is set to 10 to 100 atm using a mixed gas of nitrogen and ammonia. Also in Japanese Patent Laid-Open No. 2000-329 2400, the atmospheric pressure during the growth is 100 atm or less, and in the examples 2, 3, 5 MPa (about 20 atm, 30 atm, 50 atm) It is. In any of the conventional techniques, the growth temperatures are all 100 ° C. or lower, and in the examples, all are 85 ° C. or lower.

Aluminum nitride has a large band gap of 6.2 eV and high thermal conductivity, making it an excellent substrate material for light emitting devices in the ultraviolet region (LED, LD). Development is desired. So far, production techniques for A 1 N single crystals by the sublimation method and the HVPE method have been proposed. Also, the manufacturing method of A 1 N by the flux method (solution method) is disclosed in Japanese Patent Application Laid-Open No. 2000-3 1 1 90 09, Mat. Res. Bull. Vol. 9 (1974) 331-336. Is disclosed. In Japanese Patent Laid-Open No. 2 0 0 3-1 1 9 0 9 9, a transition metal is used as a flux. Mat. Res. Bull. Vol. 9 (1974) pp. 331-336, A 1 N single crystals are obtained from Ca ₃ N 2 and A 1 N powders.

Recently, it has been reported that high-quality bulk gallium nitride single crystals can be synthesized at low temperatures and low pressures by using Na as a catalyst (Japanese Patent Laid-Open No. 2 00 0-3 2 7 4 9 5). The raw materials are gallium and sodium azide. According to Phys. Stat. Sol. Vol.188 (2001) ρ415 · 419, Na a flux is produced from sodium azide, gallium and aluminum as raw materials. C or 80 ° C; and a pressure of about 100 to 110 atmospheres has successfully grown A 1 GaN solid solution single crystals. Disclosure of the invention

The present inventor has attempted to grow a gallium nitride single crystal and an aluminum nitride single crystal in a high temperature and high pressure region using a hot isostatic press (HIP) apparatus in comparison with the above-mentioned literature (Japanese Patent Application No. 20). 0 4— 1 0 3 0 9 3).

When crystal growth is performed by the flux method using a HIP apparatus, it is necessary to accommodate structural components such as heat and heat insulating materials (furnace materials) and movable mechanisms inside the pressure vessel. In such a high temperature and high pressure region, it has been found that they are corroded by the flux metal vapor generated from the flux in the crucible.

An object of the present invention is to provide a heater, a furnace material, and a movable mechanism using flux metal vapor generated from a flux in a crucible when a single crystal is grown using a flux containing Al force or Al force earth metal. It is to prevent corrosion of structural parts.

The present invention provides a flat containing at least an alkali or alkaline earth metal. A method of growing a single crystal using a glass, a crucible for containing flux, a lid for the crucible, a pressure vessel for containing a crucible and filling an atmosphere containing at least nitrogen gas, And a method of growing a single crystal using a flux metal vapor absorber disposed inside a pressure vessel and outside a crucible.

Further, the present invention is an apparatus for growing a single crystal using a flux containing at least an alkali or alkaline earth metal, and contains a crucible for accommodating a flux, a lid for the crucible, and a crucible. A single crystal growth apparatus comprising a pressure vessel for filling an atmosphere containing at least nitrogen gas, and a flux metal vapor absorber disposed inside the pressure vessel and outside the crucible. It is related to.

The present inventor provides a crucible for containing a flux and provides a flux metal vapor absorber in a pressure vessel for filling an atmosphere containing at least nitrogen gas, thereby providing a gap between the crucible and the lid. We absorbed the flux metal vapor leaking from the gap and succeeded in preventing corrosion of heaters, heat insulating materials and moving parts. Thus, a single crystal can be grown using an apparatus suitable for processing at high temperature and high pressure using an alkali or alkaline earth-containing flux. Brief Description of Drawings

FIG. 1 is a cross-sectional view schematically showing a reaction vessel that can be used in an embodiment of the present invention.

FIG. 2 is a view showing a state in which the reaction vessel of FIG. 1 is set in the HIP apparatus. BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below by taking gallium nitride crystal growth by the Na flux method as an example.

In a preferred embodiment, the crucible containing the flux is housed in a pressure vessel and heated under high pressure using a hot isostatic press. At this time, the atmospheric gas containing nitrogen is compressed to a predetermined pressure and supplied into the pressure vessel, and the total pressure and the nitrogen partial pressure in the pressure vessel are controlled.

However, for example, when a gallium nitride single crystal is grown by the Na flux method using such a HIP apparatus, corrosion has occurred in the heat dissipation, drive mechanism, heat insulation of the inner wall of the pressure vessel, etc. It was confirmed that this was due to Na vapor generated from Na flux. In the present invention, in order to prevent such corrosion of each member in the pressure vessel, a sodium vapor absorbing material is installed inside the pressure vessel.

In a preferred embodiment, a reaction vessel for accommodating the crucible is provided in the pressure vessel, and a sodium vapor absorber is provided in the reaction vessel. This makes it possible to install members that are susceptible to corrosion, such as heaters and heat insulating materials, outside the reaction vessel, which is further advantageous in terms of preventing corrosion of these members. In a preferred embodiment, there is provided a discharge path forming means for guiding the vapor leaked from the opening between the crucible and the lid to contact with the sodium vapor absorber. As a result, sodium vapor leaking from the crucible can be surely guided to contact with the absorbent.

The form of the discharge path forming member is not particularly limited. For example, the discharge channel forming member can be a container without a bottom, and a crucible can be accommodated in the bottomless container so that gas can escape from the gap between the bottomless container and the bottom surface of the reaction container. In addition, the discharge channel forming member is a bottomed container, the crucible is accommodated in the bottomed container, one or more discharge paths are provided on the top or side of the bottomed container, and sodium vapor is provided at the outlet of each discharge path. Absorber can be installed. FIG. 1 is a cross-sectional view schematically showing a reaction vessel 16, a discharge passage forming member 20, a sodium vapor absorber 19 and a crucible 25 for installation in a pressure vessel according to the present invention. FIG. 2 is a diagram schematically showing a single crystal growth apparatus 1 that can be used in the present invention.

For example, when the reaction vessel 16 of FIG. 1 is accommodated in the pressure vessel 2 of the HIP (hot isostatic press) apparatus, the state schematically shown in FIG. 2 is obtained. H I P (Hot Isostatic Press) The jacket 3 is fixed in the pressure vessel 2 of the apparatus, and the reaction vessel 16 is installed in the jacket 3. The reaction vessel 16 contains a raw material containing at least sodium constituting the flux.

Install a gas cylinder (not shown) outside the pressure vessel 2. The mixed gas cylinder is filled with a mixed gas of a predetermined composition. This mixed gas is compressed by a compressor to a predetermined pressure, and is supplied into the pressure vessel 2 through the supply pipe 10 as indicated by an arrow B. . Nitrogen in this atmosphere becomes a nitrogen source, and inert gases such as argon gas suppress the evaporation of sodium. This pressure is monitored by a pressure gauge (not shown). A heater 4 is installed around the reaction vessel 16 so that the growth temperature in the crucible can be controlled. As shown in FIG. 1, the reaction vessel 16 includes a reaction vessel main body 17 and a lid 23. A circular protrusion 2 3 a is formed on the lid 2 3. The lid 2 3 is fitted to the body 1 7 to form a reaction vessel 16. A discharge path forming means 20 is installed in the space 1 8 of the reaction vessel 16. A circular protrusion 2 2 a is formed on the lid 2 2. The discharge path forming means 20 of this example is a bottomless container in which a crucible 25 is accommodated. The Na flux 8 and the substrate 7 are accommodated in the inner space 24 of the crucible 25.

In this example, the Na vapor generated from the Na flux 8 passes through the gap between the lid and the crucible 25 from the space 24 as indicated by arrow C, and between the crucible 25 and the discharge channel forming means 20. The cylindrical gap 2 8 formed on the I will give you. The Na vapor further rises as indicated by an arrow E through a gap 29 between the discharge path forming means 20 and the reaction vessel main body 17.

Here, a sodium vapor absorber 19 is installed between the reaction vessel main body 17 and the discharge path forming means 20, and the steam discharged along the discharge path forming means is indicated by an arrow F. Guided to contact with sodium vapor absorber 19. Here, after absorbing Na vapor from the exhaust gas, the gas passes through the gap 30 between the lid 2 3 and the reaction vessel body 17 as indicated by the arrow G, and is released into the pressure vessel 2 as indicated by the arrow H. .

The flux metal vapor absorber is a member having the property of absorbing one or more metal vapors among the metals constituting the flux. This absorbent material preferably has at least the ability to absorb Al-strength metal or Al-strength earth metal constituting the flux. Particularly preferably, it has the ability to absorb sodium or lithium or calcium metal. The type of the flux metal vapor absorber is not particularly limited, and may be, for example, the following.

Material: Porous material such as Ryuichi Bonn, activated carbon, silica gel, zeolite

Form: Cotton, fiber, sheet, granule

For example, the following single crystals can be suitably grown by the growth method and apparatus of the present invention.

Gallium nitride, aluminum nitride, boron nitride and their solid solutions Hereinafter, more specific single crystals and their growth procedures will be exemplified.

(Gallium nitride single crystal growth example)

Utilizing the present invention, a gallium nitride single crystal can be grown using a flux containing at least sodium metal. This flux is mixed with gallium source material. Examples of gallium source materials include gallium simple metal, Although gallium alloys and gallium compounds can be applied, gallium simple metals are also preferable in terms of handling.

This flux can contain metals other than sodium, such as lithium. The usage ratio of the gallium raw material and the flux raw material such as sodium may be appropriate, but in general, the use of an excess amount of Na is considered. Of course, this is not limiting.

In this embodiment, a gallium nitride single crystal is grown under an atmosphere of a mixed gas containing nitrogen gas under a total pressure of 300 atm or more and 20000 atm or less. By setting the total pressure to 300 atm or higher, a high-quality gallium nitride single crystal can be grown in a high temperature region of, for example, 900 ° C. or higher, and more preferably in a high temperature region of 950 ° C. or higher. It was. The reason for this is not clear, but it is presumed that nitrogen solubility increases with increasing temperature, and nitrogen dissolves efficiently in the growth solution. In addition, if the total pressure of the atmosphere is 200 atm or higher, the density of the high-pressure gas and the density of the growth solution become considerably close, which makes it difficult to hold the growth solution in the crucible.

Density of various materials (g / cm metal s§table argon sodium

80 0 ° C 1 atmosphere 0.7 5 0.0 0 03 0. 0 0 0

Four

9 2 7 ° C30 0 bar 0.0 8 0.1 1

9 2 7 ° C 1 00 0 bar 0.2 1 0.3 3

9 2 7. 0 2 00 0 Atmospheric pressure 0.3 (estimated) 0.5

(Estimated) In a preferred embodiment, the nitrogen partial pressure in the growth atmosphere is set to 100 atm or more and 2 000 atm or less. By setting the nitrogen partial pressure to 100 atm or higher, it was possible to promote the dissolution of nitrogen in the flux and grow a high-quality gallium nitride single crystal, for example, in a high temperature region of 1000 ° C or higher. From this viewpoint, it is more preferable to set the nitrogen partial pressure of the atmosphere to 200 atm or higher. Further, it is preferable that the nitrogen partial pressure is practically 1 000 atm or less.

A gas other than nitrogen in the atmosphere is not limited, but an inert gas is preferable, and argon, helium, and neon are particularly preferable. The partial pressure of gases other than nitrogen is the total pressure minus the nitrogen gas partial pressure.

In a preferred embodiment, the growth temperature of the gallium nitride single crystal is 950 ° C. or higher, more preferably 1000 ° C. or higher. A high-quality gallium nitride single crystal is grown even in such a high temperature region. Is possible. In addition, it is possible to improve productivity because it can be grown at high temperatures.

There is no upper limit on the growth temperature of the gallium nitride single crystal, but since it becomes difficult for the crystal to grow if the growth temperature is too high, the temperature is preferably set to 1500 ° C or less. From this viewpoint, 1 200 ° C More preferably, it is as follows. The material of the growth substrate for epitaxial growth of gallium nitride crystals is not limited, but sapphire, A1N template, GaN template, silicon single crystal, SiC single crystal, MgO single crystal, spinel (M g A 1204) s L i a 102s L i G a 02s L a a 10 35 L a a G a 03 ₃ NdGa0 Bae Robusukai preparative composite oxide such as ₃ can be exemplified. Further, the composition formula _{_{[Ai- y (S r _ X B}} a x!) Y ] _{_{C (A 1 x _ z G}} a z) _ u · D U D 0 3 (A is a rare earth element;! D Is one or more elements selected from the group consisting of niobium and tantalum; y = 0.3-3. 9 8; x 2 0 to l; z = 0 to l; u = 0. 1 5 to 0.4 9; x + z = 0.1 to 2) cubic perovskite structure complex oxide Can be used. SCAM (ScAlMgO ₄ ) can also be used.

(A 1 N single crystal growth example)

It is confirmed that the present invention is also effective when growing an A 1 N single crystal by pressurizing a melt containing a flux containing at least aluminum and an alkaline earth in a nitrogen-containing atmosphere under specific conditions. did it. Example

(Example 1)

Using the apparatus shown in FIGS. 1 and 2, a gallium nitride single crystal film was grown on the seed crystal 7 in accordance with the procedure described with reference to FIGS.

Specifically, a yoke frame type HIP (hot isostatic pressing) device was used. In this pressure vessel 2, as shown in FIG. 1, a reaction vessel 16, a sodium vapor absorber 19, a discharge path forming means 20, a crucible 25, and a lid 2 2 were installed.

A 1 N template 7 with a diameter of 2 inches was used as a seed crystal. An A 1 N template is an A 1 N single crystal epitaxial thin film formed on a sapphire single crystal substrate. The thickness of the A 1 N thin film was 1 micron. Metal gallium and metal sodium were weighed in a glove box so that the mol ratio was 27:73, and placed in an alumina crucible 25. The crucible 25 has a cylindrical shape with a diameter of 100 mm and a height of 120 mm. An inert mixed gas having a nitrogen concentration of 50% (remaining argon) was supplied from a cylinder 12, pressurized to 40 MPa (approximately 400 atm) in a compressor, and heated to 110 ° C. The nitrogen partial pressure at this time is approximately 200 atmospheres. This gas was fed into the pressure vessel. This was maintained for 100 hours. Next, after cooling to room temperature, the weight of the crucible 25 containing the raw material, the weight of the reaction vessel main body 17 containing the crucible 25 and the weight of the lid 23 were measured. The weight of the crucible 25 was reduced by about 1%, which is thought to be due to the evaporation of metallic sodium in the flux. The weight of the reaction vessel body 1 7 (including the crucible) and the weight of the lid 2 3 were not changed. Therefore, it can be seen that the evaporated sodium was trapped by the absorbent 19. In addition, no leakage of metallic sodium outside the reaction vessel was observed, and no corrosion was observed in the heat vessel or the heat insulation inside the pressure vessel.

As a result, a GaN single crystal with a thickness of about 5 mm and a diameter of 2 inches grew.

(Comparative Example 1)

In Example 1, a comparative experiment was performed except for the sodium vapor absorber 19. However, the same as above except that the sodium vapor absorber 19 was omitted.

After cooling to room temperature, the weight of the crucible 25 containing the raw material, the weight of the reaction vessel main body 17 with the crucible 25 contained, and the weight of the lid 23 were measured. The weight of the crucible was reduced by about 1%, which may be due to evaporation of metallic sodium in the flux. The weight of the reaction vessel body 17 (including the crucible) was also reduced by 1%. Therefore, it was confirmed that the sodium evaporated from the crucible leaked into the space outside the reaction vessel 17. In addition, when the heat inside the pressure vessel and the heat insulating material were checked, some corrosion was observed.

(Example 2)

A 1 N single crystal was grown in the same manner as in Example 1. In this example, the flux material containing A 1 and Ca was weighed in a globe box. The weighed raw material was filled into an alumina crucible 25. As a seed crystal, A 1 N template 7 (1 m thick aluminum nitride on sapphire single crystal wafer) Nyum thin film (epitaxially grown) was used. Nitrogen-alkane mixed gas (nitrogen 10%) was used as an atmosphere and maintained at a predetermined temperature and pressure for 100 hours.

Next, after cooling to room temperature, the weight of the crucible 25 containing the raw material, the weight of the reaction vessel main body 17 containing the crucible 25, and the weight of the lid 23 were measured. The weight of the crucible 25 was reduced by about 0.1%. The weight of the reaction vessel body 1 7 (including the crucible) and the weight of the lid 2 3 were not changed. In addition, no corrosion was observed on the heater or insulation in the pressure vessel.

As a result, it was confirmed that an aluminum nitride single crystal with a thickness of about 1 mm grew on the A 1 N template.

The amount of flux evaporated from the crucible is considered to be determined by the vapor pressure at the growth temperature. Table 2 shows the vapor pressures of sodium, lithium, and calcium, which are representative flux materials, compared with the vapor pressures of aluminum and gallium. Table 2 '

Source: Metal Handbook

Na Li Ca Al Ga

1000 ° C 2.6 0.1 0.005 2 X 10- 7 substantially 0

1100. C 5.1 0.2 0.02 No data No data

1200 ° C 9 0.5 0.05 1.4 X 10— ⁵ 1.5 X 10— ⁴

Claims

The scope of the claims

1. A method of growing a single crystal using a flux containing at least Al-strength or Al-strength earth metal,

A crucible for containing the flux;

The lid for this robot,

A pressure vessel for containing the crucible and filling an atmosphere containing at least nitrogen gas; and

A method for growing a single crystal, comprising using a flux metal vapor absorbent disposed in the pressure vessel and outside the crucible, to grow the single crystal.

2. The method according to claim 1, wherein a reaction vessel provided in the pressure vessel and containing the crucible is used, and the flux metal vapor absorber is provided in the reaction vessel.

3. The discharge path forming means for guiding the vapor leaking from the opening between the crucible and the lid to contact with the flux metal vapor absorber is used. Or the method according to 2.

4. The method according to any one of claims 1 to 3, wherein the single crystal is a nitride single crystal.

5. The nitride single crystal is grown under an atmosphere of a mixed gas containing nitrogen gas under a total pressure of not less than 300 atm and not more than 200 atm. the method of.

6. The method according to any one of claims 1 to 5, wherein the single crystal is grown using a hot isostatic pressing apparatus.

7. Raised by the method according to any one of claims 1-6. A single crystal characterized by being formed.

8. An apparatus for growing a single crystal using a flux containing at least Al or Li earth metal,

A crucible for containing the flux,

This crucible lid,

Flux metal, vapor absorber disposed in the pressure vessel and outside the crucible

An apparatus for growing a single crystal, comprising:

9. The reaction vessel according to claim 8, further comprising a reaction vessel provided in the pressure vessel and containing the crucible, wherein the flux metal vapor absorber is provided in the reaction vessel. apparatus.

10. Equipped with a discharge path forming means for guiding the steam leaking from the opening between the crucible and the lid to contact with the flux metal vapor absorber. Item 8 or 9 device.

11. The apparatus according to any one of claims 8 to 10, wherein the single crystal is a nitride single crystal.

12. A device according to any one of claims 8 to 11, further comprising a hot isostatic pressing mechanism for heating and pressurization.