JP2006273684A - Method for producing group iii element oxide-based single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a group III element oxide-based single crystal in which a highly pure and large-sized single crystal can be obtained. <P>SOLUTION: A β-Ga<SB>2</SB>O<SB>3</SB>-based single crystal 8 is produced by the FZ method (floating-zone method). A melting zone 8d is formed by heating and melting a part which is in contact with a sintering material 9 composed of a β-Ga<SB>2</SB>O<SB>3</SB>-based polycrystal to which are added a β-Ga<SB>2</SB>O<SB>3</SB>-based seed crystal 7 and an additive for regulating thermal meltability in an amount depending on the outer diameter of the targeted β-Ga<SB>2</SB>O<SB>3</SB>-based single crystal 8. The single crystal 8 grows at the leading end of the seed crystal 7 by decreasing the temperature of the melting zone 8d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a group III oxide single crystal for use in a light emitting device, and more particularly to a method for producing a group III oxide single crystal from which a single crystal having high purity and high quality and a large diameter can be obtained.

The light emitting element in the ultraviolet region is particularly expected as a light source for a mercury-free fluorescent lamp, a photocatalyst that provides a clean environment, and a new generation DVD that realizes higher density recording. From such a background, GaN-based blue light emitting elements have been realized, but further light sources with shorter wavelengths are required. On the other hand, in recent years, production of a substrate using a bulk single crystal of β-Ga ₂ O ₃ has been studied as a substrate that transmits ultraviolet light.

  As a conventional single crystal growth method for producing such a substrate material, an FZ method (Floating Zone Technique) is known (see, for example, Non-Patent Document 1).

In the FZ method, a seed crystal of β-Ga ₂ O ₃ and a sintered material are contacted, and the contact portion is heated and melted to form a joint where the seed crystal and the sintered material are melted. Is a method of producing a single crystal by lowering. According to this method, since a container in contact with a single crystal is not used, there are advantages such as prevention of contamination from the container, no limitation of the use atmosphere by the container, and growth of a material that easily reacts with the container. .
M.M. Saurat, A .; Rev. Co., Rev. Int. Hautes Temper. Et Refract., 1971, p. 291

  However, in the conventional FZ method, a temperature difference between the central portion and the outer peripheral portion of the melting zone occurs as the outer diameter of the target single crystal increases.

FIG. 4 shows a melting zone 8d in a conventional method for growing a β-Ga ₂ O ₃ -based single crystal by the FZ method. When the β-Ga ₂ O ₃ sintered material 9 is melted, the temperature at the center of the melting zone 8d decreases and solidifies in a conical shape to form a solidified portion 8e, and the solidified portion 8e melts during the growth of the single crystal. It contacts the non-sintered material 9. Therefore, the rotation of the sintered material 9 and the β-Ga ₂ O ₃ single crystal 8 is not uniform. For example, the sintered material 9 vibrates in the direction of arrow A, and the crystal growth interface of the β-Ga ₂ O ₃ single crystal 8 The interface between the solidified part 8e and the melting part of the melting zone 8d becomes unstable, and the quality of the β-Ga ₂ O ₃ -based single crystal 8 is deteriorated.

FIG. 5 is a diagram showing a state in which the melting zone 8d has dripped in the conventional FZ method. If the light power of the light source is increased in order to reduce the solidified portion 8e, the temperature of the outer peripheral portion of the melting zone 8d increases, the viscosity decreases, and the heating range widens. However, there is a problem that the melting zone 8d is separated from the sintered material 9 and it becomes difficult to grow crystals. From these problems, it was difficult to produce a high-purity and large-diameter β-Ga ₂ O ₃ -based single crystal 8.

  Accordingly, an object of the present invention is to provide a method for producing a Group III oxide single crystal from which a single crystal having a large diameter and high purity and quality can be obtained.

  In order to achieve the above object, the present invention provides a group III oxide-based sintered material in which a seed crystal composed of a group III oxide-based single crystal and a target group III oxide-based single crystal are added with an additive for adjusting heat melting. The material is prepared, and the seed crystal and the group III oxide-based sintered material are brought close to each other and heated and melted to form a joint where the seed crystal and the group III oxide-based sintered material are dissolved. And providing a target Group III oxide single crystal based on the temperature drop of the junction, wherein the target Group III oxide single crystal is manufactured.

  According to this configuration, the infrared absorption characteristic of the single crystal is increased by adding the additive for adjusting the heat melting property to the Group III oxide single crystal to be manufactured (hereinafter simply referred to as “single crystal”). It is considered that the single crystal efficiently absorbs infrared rays from the light source. In addition, it is considered that the addition of a predetermined amount of the additive for adjusting the heat melting property increases the electric conductivity, and the heat conduction is improved accordingly. For this reason, the temperature difference between the central part of the sintered part of the sintered material and the outer peripheral part of the sintered material is reduced, so that the central part is difficult to solidify, and the solidified part comes into contact with the sintered material and forms a single crystal growth interface. A high-purity group III oxide single crystal can be produced without being unstable.

Ga ₂ O ₃ , Al ₂ O ₃ , In ₂ O ₃ or the like can be used as the group III oxide. Ga ₂ O ₃ in which the, alpha type from the crystalline form, beta form, gamma form, [delta] type, but the type of ε-type, etc. are present, it is stable at normal temperature and pressure beta-type Ga ₂ O ₃ ( It is preferable to use (β-Ga ₂ O ₃ ).

Further, instead of a seed crystal, β-Ga containing an oxide of an element such as gallium, indium, and aluminum whose group III oxide is the same monoclinic system as β-Ga ₂ O ₃ and whose space group belongs to C2 / m the ₂ O ₃ consisting of a solid solution Kakaru using _beta-Ga 2 _{O 3} system seed crystal made of a solid solution _beta-Ga 2 _{O 3} system single crystal may be grown. Thereby, LED which light-emits in an ultraviolet to blue wavelength range is realizable.

  Moreover, you may make it add the additive for heat-meltability adjustment in the addition amount according to the outer diameter of a group III oxide type sintered raw material.

  The additive for adjusting characteristics is preferably a group IV element, particularly Si, Sn, Zr, Hf, Ge, or an oxide thereof.

  Moreover, it is preferable to add the heat-meltability adjusting additive so that the amount of the group IV element is 0.0001 to 1% with respect to the amount of the group III element.

As the group III oxide-based sintered material, it is preferable to use a group III oxide-based powder and SiO ₂ powder mixed, cold-compressed and sintered.

Further, in order to achieve the above object, the present invention provides a seed crystal composed of a Ga ₂ O ₃ single crystal as a group III oxide single crystal and an addition for adjusting the heat melting property to the target Ga ₂ O ₃ single crystal. Preparing a Ga ₂ O ₃ based sintered material to which Si or SiO ₂ is added as a product, and bringing the seed crystal and the Ga ₂ O ₃ based sintered material close to each other and heating and melting the seed crystal and the above A group III oxide single crystal characterized by forming a joint with a Ga ₂ O ₃ based sintered material and producing the target Ga ₂ O ₃ single crystal based on a temperature drop of the joint A manufacturing method is provided.

  According to the present invention, a high-purity and high-quality large-diameter group III oxide single crystal can be obtained.

FIG. 1 shows an infrared heating single crystal manufacturing apparatus according to an embodiment of the present invention. This infrared heating single crystal manufacturing apparatus 1 manufactures a β-Ga ₂ O ₃ single crystal as a group III oxide by FZ method (floating zone method), and includes a quartz tube 2 and β-Ga ₂ O A seed rotating unit 3 that holds and rotates a _three- system seed crystal (hereinafter abbreviated as “seed crystal”) 7 and a β-Ga ₂ O ₃ -based sintered material (hereinafter abbreviated as “sintered material”) 9 are retained. A schematic configuration having a rotating material rotating unit 4, a heating unit 5 for heating and melting the sintered material 9, and a control unit 6 for controlling the seed rotating unit 3, the material rotating unit 4 and the heating unit 5. Has been.

  The seed rotating unit 3 includes a seed chuck 33 that holds the seed crystal 7, a lower rotating shaft 32 that transmits rotation to the seed chuck 33, a lower driving unit 31 that rotates the lower rotating shaft 32 in the normal direction and moves the lower rotating shaft 32 in the vertical direction. Is provided.

  The material rotating unit 4 moves the material chuck 43 that holds the upper end 9 a of the sintered material 9, the upper rotating shaft 42 that transmits the rotation to the material chuck 43, the upper rotating shaft 42 forward and backward, and the vertical rotation. The upper drive part 41 to be provided is provided.

  The heating unit 5 accommodates a halogen lamp 51 that heats and melts the sintered material 9 from the radial direction, condenses light emitted from the halogen lamp on a predetermined portion of the sintered material 9, and the halogen lamp 51. And a power supply unit 53 for supplying power to the device.

The quartz tube 2 accommodates a lower rotating shaft 32, a seed chuck 33, an upper rotating shaft 42, a material chuck 43, a sintered material 9, a β-Ga ₂ O ₃ system single crystal 8 and a seed crystal 7. The quartz tube 2 is sealed by being supplied with a mixed gas of oxygen gas and nitrogen gas as an inert gas.

Next, the β-Ga ₂ O ₃ -based single crystal growth method according to the present embodiment will be described with reference to FIGS. 2A to 2D show a process of growing a β-Ga ₂ O ₃ single crystal according to an embodiment of the present invention. In FIG. 2, the seed chuck 33 is omitted.

(1) Preparation of seed crystal The seed crystal 7 is, for example, a β-Ga ₂ O ₃ single crystal cut out along the cleavage plane as a group III oxide, and has, for example, a prismatic shape with a square cross section. A part of the crystal 7 is held by the seed chuck 33. The seed crystal 7 has an outer diameter of 1/5 or less or a cross-sectional area of 5 mm ² or less of the grown crystal in order to grow a good β-Ga ₂ O ₃ single crystal 8, and β-Ga ₂ O ₃ It has a strength that does not break during the growth of the system single crystal 8. In the present embodiment, the cross-sectional area is set to 1 to ² mm ² . The axial direction is an a-axis <100> orientation, a b-axis <010> orientation, or a c-axis <001> orientation (a crystallographically determined orientation). Here, the outer diameter means one side of a square, a long side of a rectangle, a diameter of a circle, or the like. The error between the axial direction and each direction is preferably within a range of plus or minus 10 °.

(2) Preparation of sintered material 9 First, the sintered material 9 is prepared as follows. That is, for example, powder of _β-Ga 2 _{O 3} polycrystalline purity 5N, thermally fusible adjustment additives _β-Ga 2 _{O 3} system to be manufactured single crystals, for example 0.0001% in the number of atoms Of Si is added. The additive for adjusting the heat melting property is not limited to Si, and other group IV elements can be used. Further, the addition amount of the additive for adjusting the heat melting property may be an amount corresponding to the outer diameter of the sintered material 9. Here, instead of adding Si alone, for example, SiO ₂ is added. Next, a β-Ga ₂ O ₃ polycrystalline powder to which SiO ₂ has been added is filled in a rubber tube (not shown) and cold compressed at 500 MPa. Then, it sinters at 1500 degreeC for 10 hours, and obtains the rod-shaped sintered raw material 9 as a sintered compact.

(3) Production of β-Ga ₂ O ₃ System Single Crystal 8 Next, as shown in FIG. 1, a part of the seed crystal 7 is held on the seed chuck 33, and the upper end portion 9a of the rod-shaped sintered material 9 is used as the material. Hold on the chuck 43. Next, as shown in FIG. 2A, the upper and lower positions of the upper rotating shaft 42 are adjusted so that the upper end 7 a of the seed crystal 7 and the lower end 9 b of the sintered material 9 are brought into contact with each other. Further, the upper and lower positions of the upper rotating shaft 42 and the lower rotating shaft 32 are adjusted so that the light from the halogen lamp 51 is focused on the upper end 7 a of the seed crystal 7 and the lower end 9 b of the sintered material 9. The atmosphere 2a of the quartz tube 2 is filled with a total pressure of 1 to 2 atmospheres of a mixed gas of nitrogen and oxygen (which changes between 100% nitrogen and 100% oxygen).

  When the operator turns on a power switch (not shown), the control unit 6 controls each unit according to the control program and performs single crystal growth control as follows. When the heating unit 5 is turned on, the halogen lamp 51 heats the upper end 7a of the seed crystal 7 and the lower end 9b of the sintered material 9, and melts the heated portion to form the molten droplet 8c. At this time, only the seed crystal 7 is rotated.

Next, the sintered material 9 and the seed crystal 7 are melted while being rotated in the opposite direction so that the sintered material 9 and the seed crystal 7 are sufficiently adapted. When the molten droplet 8c of β-Ga ₂ O _{3 having} an appropriate size is obtained, the rotation of the sintered material 9 is stopped, and only the seed crystal 7 is rotated and sintered as shown in FIG. The material 9 and the seed crystal 7 are pulled in opposite directions to form a dash neck 8a that is thinner than the seed crystal 7.

Next, the seed crystal 7 and the sintered material 9 are heated by the halogen lamp 51 while rotating in the opposite directions at 20 rpm, and the seed crystal 7 and the sintered material 9 are moved downward relative to the halogen lamp 51. When the sintered material 9 is heated by the halogen lamp 51, the sintered material 9 is melted to form a melting zone 8d, and when the temperature drops, as shown in FIG. A β-Ga ₂ O ₃ -based single crystal 8 having a small outer diameter D is generated.

FIG. 3 is a diagram showing a melting zone 8d when a single crystal is grown using the infrared heating single crystal manufacturing apparatus according to the embodiment of the present invention. When to melt the sintered material 9 to form a melt zone 8d, the central portion becomes hardly solidified by the action of Si or SiO ₂ was added, solidified portion 8e is present at a height which does not contact the sintered material 9.

After forming a single crystal of an appropriate length, as shown in FIG. 2 (d), an upper portion of the β-Ga ₂ O ₃ single crystal 8 is taken out in order to take out the generated β-Ga ₂ O ₃ single crystal 8 The diameter of 8b is reduced.

Next, the effect of this embodiment will be described.
(Ii) When Si or SiO ₂ is added, when heated from the outside, even if the crystal has a large outer diameter, the temperature difference between the center and the outside becomes small, so that the center becomes difficult to solidify. The interface for growing the Ga ₂ O ₃ single crystal does not become unstable, and the quality of the β-Ga ₂ O ₃ single crystal 8 can be prevented from being deteriorated. It by adding Si or SiO _2, the infrared absorption characteristics of the _β-Ga 2 _{O 3} system single crystal 8 is increased, the infrared radiation from the light source _β-Ga 2 _{O 3} system single crystal 8 is efficiently It is because it is thought that it will absorb. Further, by adding Si or SiO _2, and the electrical conductivity increases, because also considered even better thermal conduction accordingly. Incidentally, the infrared absorption characteristics of the _β-Ga 2 _{O 3} system single crystal 8 is increased, evidenced by the _β-Ga 2 _{O 3} single crystal 8 is bluish.
(B) By adding Si or SiO ₂ , the balance of the viscosity and tension of the melting zone 8d, the gravity of the melted β-Ga ₂ O ₃ sintered material 9 and the like are maintained, so the molten sintered material 9 Since it is difficult to fall, a large-diameter β-Ga ₂ O ₃ -based single crystal 8 can be obtained.
(C) Since the melting point is lowered by adding Si or SiO ₂ , the β-Ga ₂ O ₃ sintered material 9 can be melted without increasing the optical power of the light source.
(D) This β-Ga ₂ O ₃ single crystal 8 is cracked and twinned by setting the a-axis <100> orientation, b-axis <010> orientation, or c-axis <001> orientation as the crystal axis. The tendency is reduced and high crystallinity is obtained.
(E) Moreover, the β-Ga ₂ O ₃ single crystal 8 can be generated with good reproducibility. Therefore, the utility value as a semiconductor substrate such as a light emitting element is also high.

As is clear from the above (a) to (c), the added Si or SiO ₂ has an effect of adjusting various properties such as thermal conductivity, viscosity, tension, melting point and the like of β-Ga ₂ O ₃ .

[Other embodiments]
In addition, this invention is not limited to said embodiment, A various deformation | transformation implementation is possible. For example, when crystal growth is performed by the FZ method with a total pressure of 2 atmospheres or more as a mixed gas of nitrogen and oxygen, generation of bubbles can be suppressed and the crystal growth process can be further stabilized.

  Moreover, you may heat with a heating coil instead of a halogen lamp. Moreover, although it demonstrated as what uses nitrogen gas as an inert gas, you may use argon instead of nitrogen gas.

  Further, the seed crystal 7 may have a rectangular cross section, and may have a columnar shape or an elliptical column shape instead of a prismatic shape.

In the present invention, the β-Ga ₂ O ₃ -based seed crystal 7, the β-Ga ₂ O ₃ -based single crystal 8, and the sintered material 9 are moved, but the sintered material 9 can also be moved by moving the heating unit 5. The β-Ga ₂ O ₃ single crystal 8 can be grown.

  Although the present invention has been described with respect to the FZ method, it can also be applied to methods for growing other single crystals such as the CZ method.

It is principal part sectional drawing which shows the infrared heating single crystal manufacturing apparatus which concerns on embodiment of this invention. (A) ~ (d) are diagrams showing the growing process of _β-Ga 2 _{O 3} single crystal according to the embodiment of the present invention. It is a diagram showing the melting zone when that is grow a β-Ga ₂ O ₃ single crystal by using an infrared heating single crystal manufacturing apparatus according to the embodiment of the present invention. Is a diagram showing the melting zone in the growth method of the conventional FZ method using β-Ga ₂ O ₃ system single crystal. It is a figure which shows the state which caused the dripping of the melting zone in the conventional FZ method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Infrared heating single crystal manufacturing apparatus, 2 ... Quartz tube, 2a ... Atmosphere, 3 ... Seed rotating part, 4 ... Material rotating part, 5 ... Heating part, 6 ... Control part, 7 ... Seed crystal, 8 ... β-Ga ₂ O ₃ single crystal, 8a ... dash neck, 8b ... upper part, 8c ... melting droplet, 8d ... melting zone, 8e ... solidified part, 8f ... drip part, 9 ... sintered material, 9a ... upper end, 9b ... lower end , 31 ... Lower drive unit, 32 ... Lower rotation shaft, 33 ... Seed chuck, 41 ... Upper drive unit, 42 ... Upper rotation shaft, 43 ... Material chuck, 51 ... Halogen lamp, 52 ... Elliptical mirror, 53 ... Power supply unit

Claims (7)

Preparing a seed crystal composed of a group III oxide single crystal and a group III oxide based sintered material obtained by adding an additive for adjusting heat melting to the target group III oxide single crystal;
Forming a joint where the seed crystal and the group III oxide-based sintered material are melted by bringing the seed crystal and the group III oxide-based sintered material close to each other and heating and melting,
A method for producing a group III oxide single crystal, comprising producing the target group III oxide single crystal based on a temperature drop of the junction.   2. The method for producing a group III oxide single crystal according to claim 1, wherein the additive for adjusting heat melting property is a group IV element.   The group III oxide single crystal according to claim 1, wherein the heat-meltability adjusting additive is added in an amount according to the outer diameter of the group III oxide sintered material. Method.   3. The method for producing a group III oxide single crystal according to claim 2, wherein the group IV element is Si, Sn, Zr, Hf, or Ge.   The Group III oxide according to claim 1, wherein the additive for adjusting heat melting property is added so that the amount of Group IV element is 0.0001 to 1% with respect to the amount of Group III element. A method for producing a single crystal. The III oxide sintered material, a mixture of Group III oxide powder and SiO ₂ powder is compressed cold, Group III oxide according to claim 1, characterized by using a material obtained by sintering A method for producing a single crystal. Group III oxide _Ga 2 _{O 3} system _Ga 2 _{O 3} to the _Ga 2 _{O 3} system single crystal seed crystal and the object made of single crystal Si was added or SiO ₂ as a heat-meltable adjustment additive as a single crystal Prepare the system sintered material,
Forming a joint between the seed crystal and the Ga ₂ O ₃ sintered material by bringing the seed crystal and the Ga ₂ O ₃ sintered material close to each other and heating and melting them;
A method for producing a group III oxide single crystal, comprising producing the target Ga ₂ O ₃ single crystal based on a temperature drop of the junction.