JP4630986B2 - β-Ga2O3-based single crystal growth method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a β-Ga ₂ O ₃ single crystal growth method, and more particularly, to a β-Ga ₂ O ₃ single crystal growth method with improved cracking and twinning tendency and improved crystallinity.
[0002]
[Prior art]
Light-emitting elements in the ultraviolet region are particularly expected for the realization of mercury-free fluorescent lamps, photocatalysts that provide a clean environment, and new-generation DVDs that realize higher-density recording. Against this background, GaN-based blue light-emitting elements have been realized, but further light sources with shorter wavelengths have been demanded. In recent years, the production of β-Ga ₂ O ₃ bulk-based single crystals has been studied. Yes. FIG. 7 shows a substrate 200 formed of a conventional β-Ga ₂ O ₃ bulk single crystal.
[0003]
CZ method (Czochralski method) and FZ method (Floating Zone Technique) are known as conventional single crystal growth methods for producing such a material of the substrate 200 (see, for example, Non-Patent Document 1).
[0004]
The CZ method is performed as follows. First, an Ir crucible filled with 4N purity Ga ₂ O ₃ powder as a raw material was covered with a quartz tube, and oxygen gas 1 vol. The Ir crucible is heated by a high-frequency oscillator while flowing a mixed gas mixed in a quartz tube to dissolve the Ga ₂ O ₃ powder, thereby producing a polycrystalline dissolved solution of Ga ₂ O ₃ . Subsequently, the separately prepared β-Ga ₂ O ₃ seed crystal is brought into contact with the dissolved Ga ₂ O ₃ , and the β-Ga ₂ O ₃ seed crystal is pulled up at a speed of 1 mm / h and a crystal rotation speed of 15 rpm. _{A 2} O ₃ single crystal is produced. This method has an advantage that a β-Ga ₂ O ₃ single crystal having a large diameter can be grown.
[0005]
The FZ method is a method of growing a crystal while supporting an upper raw material, for example, a β-Ga ₂ O ₃ polycrystal melt with a lower β-Ga ₂ O ₃ seed crystal. According to this method, since the container 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.
[0006]
[Non-Patent Document 1]
M.M. Saurat, A .; Rev. Co., Rev. Int. Hautes Temper. Et Refract., 1971, p. 291
[0007]
[Problems to be solved by the invention]
However, in the conventional CZ method, it is difficult to control crystal growth due to intense evaporation of the melt components from the Ga ₂ O ₃ melt and remarkable unstable growth.
[0008]
In addition, in the FZ method, a single crystal of about 1 cm ² can be obtained depending on conditions, but due to intense evaporation from the melting zone and steep temperature gradient, twinning and cracking occur, and the large size required for the substrate High quality and high quality were difficult. Furthermore, when the substrate 200 is manufactured using a β-Ga ₂ O ₃ single crystal whose orientation is not fixed, cracking 201 is generated, so that it is very difficult to cut in a direction other than the cleavage plane (100).
[0009]
Accordingly, an object of the present invention is to provide a β-Ga ₂ O ₃ single crystal growth method that is less likely to crack even when processed into a large-sized, high-quality substrate or the like.
[0010]
[Means for Solving the Problems]
The present invention, in order to achieve the above object, prepares the _β-Ga 2 _{O 3} system seed crystal, a shaft <100> orientation from _β-Ga 2 _{O 3} system seed crystal, b-axis <010> orientation or c providing _β-Ga 2 _{O 3} single crystal growing method characterized by growing _β-Ga 2 _{O 3} system single crystal in the axial <001> orientation.
[0011]
According to this configuration, cracking and twinning tendencies are reduced, crystallinity is increased, and workability is improved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
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 by FZ method (floating zone method), and includes a quartz tube 2 and a β-Ga ₂ O ₃ seed crystal (hereinafter referred to as “seed”). Abbreviated to “crystal”.) A seed rotating unit 3 that holds and rotates 7; a material rotating unit 4 that holds and rotates a β-Ga ₂ O ₃ polycrystalline material (hereinafter abbreviated as “polycrystalline material”) 9; A heating unit 5 that heats and melts the polycrystalline material 9 and a control unit 6 that controls the seed rotating unit 3, the material rotating unit 4, and the heating unit 5 are schematically configured.
[0013]
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.
[0014]
The material rotating unit 4 moves the material chuck 43 that holds the upper end 9a of the polycrystalline 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. And an upper drive unit 41 to be operated.
[0015]
The heating unit 5 contains a halogen lamp 51 that heats and melts the polycrystalline material 9 from the radial direction, and an elliptical mirror that houses the halogen lamp 51 and collects light emitted from the halogen lamp at a predetermined portion of the polycrystalline material 9. 52 and a power supply unit 53 that supplies power to the halogen lamp 51.
[0016]
The quartz tube 2 accommodates a lower rotating shaft 32, a seed chuck 33, an upper rotating shaft 42, a material chuck 43, a polycrystalline material 9, a β-Ga ₂ O ₃ 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.
[0017]
Next, the β-Ga ₂ O ₃ single crystal growth method according to the present embodiment will be described with reference to FIGS.
[0018]
(1) Production of Seed Crystal FIG. 2 shows a front view of the seed crystal 7. The seed crystal 7 has a prismatic shape with a square cross section, and a part of the seed crystal 7 is held by the seed chuck 33. As the seed crystal 7, for example, a β-Ga ₂ O ₃ single crystal cut out along the cleavage plane is used. In order to grow a good β-Ga ₂ O ₃ single crystal, the seed crystal 7 has a diameter of 1/5 or less of the grown crystal or a cross-sectional area of 5 mm ² or less, and the β-Ga ₂ O ₃ single crystal Has strength that does not break during growth. In the present embodiment, the cross-sectional area is set to 1 to ² mm ² . The axial direction is the a-axis <100> orientation, the b-axis <010> orientation, or the c-axis <001> orientation . Here, the 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 °.
[0019]
3A to 3D show the growth process of the β-Ga ₂ O ₃ single crystal according to the embodiment of the present invention, and FIG. 4 shows the single crystal according to the embodiment of the present invention. 3 and 4, the seed chuck 33 is omitted.
[0020]
(2) Production of polycrystalline material 9 First, the polycrystalline material 9 is produced as follows. That is, a predetermined amount of 4N purity Ga ₂ O ₃ powder is filled in a rubber tube (not shown) and cold-compressed at 500 MPa. Thereafter, sintering is performed at 1500 ° C. for 10 hours to obtain a rod-like polycrystalline material 9.
[0021]
(3) Production of β-Ga ₂ O ₃ Single Crystal 8 Next, as shown in FIG. 1, a part of the seed crystal 7 is held by the seed chuck 33, and the upper end portion 9a of the rod-like polycrystalline material 9 is used as the material. Hold on the chuck 43. Next, as shown in FIG. 3A, 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 polycrystalline material 9 are brought into contact with each other. Further, the vertical positions of the upper rotary shaft 42 and the lower rotary shaft 33 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 polycrystalline 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).
[0022]
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 portion 7a of the seed crystal 7 and the lower end portion 9b of the polycrystalline material 9 to melt the heated portion, thereby forming a dissolving droplet 8c. . At this time, only the seed crystal 7 is rotated.
Next, the polycrystalline material 9 and the seed crystal 7 are melted while being rotated in the opposite direction so that the polycrystalline crystal 9 and the seed crystal 7 are sufficiently adapted. As shown in FIG. 3 (b), when a moderate β-Ga ₂ O ₃ single crystal melt 8 ′ is formed, the rotation of the polycrystalline material 9 is stopped, and only the seed crystal 7 is rotated to obtain a large amount. The crystal 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 polycrystalline material 9 are heated by the halogen lamp 51 while rotating in opposite directions at 20 rpm, and the polycrystalline material 9 is pulled upward by the upper rotating shaft 42 at a rate of 5 mm / hour. When the polycrystalline material 9 is heated by the halogen lamp 51, the polycrystalline material 9 is melted to form a melt 8 ', and when it is cooled, it is equivalent to the polycrystalline material 9 as shown in FIG. Alternatively, β-Ga ₂ O ₃ single crystal 8 having a smaller diameter is formed. After forming the appropriate length of the single crystal, as shown in FIG. 3 (d), the upper 8b of β-Ga ₂ O ₃ single crystal 8 in order to extract the β-Ga ₂ O ₃ single crystal 8 generated Reduce diameter.
[0023]
(4) Production of Substrate FIG. 5 shows a substrate formed from the β-Ga ₂ O ₃ single crystal 8. When the β-Ga ₂ O ₃ single crystal 8 is grown in the b-axis <010> orientation, the cleavage of the (100) plane becomes strong, so that the plane perpendicular to the plane parallel to the (100) plane The substrate 60 is manufactured by cutting. When the crystal is grown in the a-axis <100> orientation and the c-axis <001> orientation, the cleaving properties of the (100) plane and (001) are weakened, so that the workability of all the faces is improved, as described above. There is no limit on the cut surface.
[0024]
FIG. 6 shows a unit cell of a β-Ga ₂ O ₃ single crystal. In the β-Ga ₂ O ₃ single crystal, 8 Ga atoms and 12 O atoms are shown as Ga (1), Ga (2), O (1), O (2), O (3). In the figure, a, b, and c indicate the a-axis <100> orientation, the b-axis <010> orientation, and the c-axis <001> orientation, respectively.
[0025]
Next, the effect of this embodiment will be described.
(A) Since the crystal is grown in a predetermined direction, a large β-Ga ₂ O ₃ single crystal 8 having a diameter of 1 cm or more can be obtained.
(B) This β-Ga ₂ O ₃ single crystal 8 has a tendency of cracking and twinning by using the a-axis <100> orientation, the b-axis <010> orientation, or the c-axis <001> orientation as the crystal axis. Decreases and high crystallinity is obtained.
(C) In addition, such crystals can be generated with good reproducibility. Therefore, the utility value as a substrate of a semiconductor or the like is high.
In addition, this invention is not limited to said embodiment, A various deformation | transformation implementation is possible.
For example, instead of the _β-Ga 2 _{O 3} seed crystal 7, _β-Ga 2 _{O 3} and the same monoclinic system, _β-Ga 2 _{O 3} of gallium space group belongs to C2 / m, indium, aluminum, tin One or more elements selected from the group consisting of germanium, nickel, copper, zinc, zirconium, niobium, molybdenum, titanium, vanadium, chromium, manganese, iron, cobalt, hafnium, tantalum, tungsten, silicon and magnesium oxide _β-Ga 2 _{O 3} consisting of a solid solution _β-Ga 2 _{O 3} system seed crystal comprising _β-Ga 2 _{O 3} system single crystal of a solid solution may be grown to Kakaru with including. Thereby, LED which light-emits in an ultraviolet to blue wavelength range is realizable.
Further, when the FZ method is performed with a total pressure of 2 atm 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.
[0026]
Further, when the single crystal 8 needs to be pulled upward, the lower rotating shaft 32 may be lowered. Further, instead of moving the halogen lamp 51, the lower rotating shaft 32 and the upper rotating shaft 42 may be moved to heat them. You may heat with a heating coil instead of a halogen lamp.
Although the present invention has been described as using nitrogen gas as an inert gas, argon may be used 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 addition to the FZ method, the present invention can also be applied to other crystal growth methods such as an EFG method (a shape-controlled crystal growth method using a Czochralski method which is a pulling method).
[0027]
【The invention's effect】
As described above, according to the present invention, the β-Ga ₂ O ₃ single crystal is grown in a predetermined direction, so that cracking and twinning tendency are reduced, and β-Ga ₂ O having high crystallinity is obtained. _{A three-} system single crystal can be obtained.
In addition, a substrate obtained by processing such a β-Ga ₂ O ₃ single crystal having high crystallinity has a high yield and is highly usable as a substrate for a semiconductor or the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an infrared heating single crystal manufacturing apparatus according to an embodiment of the present invention.
FIG. 2 is a front view of a β-Ga ₂ O ₃ seed crystal according to an embodiment of the present invention.
FIGS. 3A to 3D show a growth process of a β-Ga ₂ O ₃ single crystal according to an embodiment of the present invention.
FIG. 4 is a diagram showing a single crystal product according to an embodiment of the present invention.
FIG. 5 is a diagram showing a β-Ga ₂ O ₃ single crystal substrate according to an embodiment of the present invention.
FIG. 6 is a diagram showing an atomic arrangement of a β-Ga ₂ O ₃ single crystal according to an embodiment of the present invention.
FIG. 7 is a view showing a conventional single crystal substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Infrared heating single crystal manufacturing apparatus 2 Quartz tube 2a Atmosphere 3 Seed rotation part 4 Material rotation part 5 Heating part 6 Control part 7 Seed crystal 8 β-Ga ₂ O ₃ single crystal 8a Dash neck 8b Single crystal upper part 8c Melting droplet 8 'Melt 9 Polycrystalline material 9a Polycrystalline material upper 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 60, 200 Substrate 201 cracking

Claims (14)

A β-Ga ₂ O ₃ based seed crystal is prepared,
A β-Ga ₂ O ₃ based single crystal is grown from the β-Ga ₂ O ₃ based seed crystal in the a-axis <100> orientation, the b-axis <010> orientation, or the c-axis <001> orientation. A β-Ga ₂ O ₃ -based single crystal growth method. The a-axis <100> azimuth, the b-axis <010> azimuth, or the c-axis <001> azimuth is an azimuth within a range of plus or minus 10 degrees with respect to each azimuth. Item 6. The β-Ga ₂ O ₃ -based single crystal growth method according to Item 1 . The _beta-Ga 2 Growth of _{O 3} system single crystal, _β-Ga 2 _{O 3} single crystal growing method according to claim 1, wherein the by FZ method. The β-Ga ₂ O ₃ single crystal according to claim 3, wherein a diameter of the β-Ga ₂ O ₃ polycrystalline raw material rod used in the FZ method is equal to or larger than a diameter of the grown crystal. Growth method. 2. The β-Ga according to claim 1, wherein the growth of the β-Ga ₂ O ₃ single crystal is performed in an atmosphere of a mixed gas of O ₂ and an inert gas at a total pressure of 1 to 2 atm. ₂ O ₃ single crystal growth method. The β-Ga ₂ O ₃ system the growth of a single crystal, according to claim 1, wherein beta-Ga ₂ that the total pressure is equal to or carried out in an atmosphere of a mixed gas of inert gas and O ₂ of more than 2 atm O ₃ single crystal growth method. The β-Ga ₂ O ₃ -based single crystal growth method according to claim 1, wherein the β-Ga ₂ O ₃ -based seed crystal is a single crystal. The β-Ga ₂ O ₃ -based seed crystal is grown in the a-axis <100> orientation, the b-axis <010> orientation, or the c-axis <001> orientation. -ga ₂ O ₃ single crystal growing method. The a-axis <100> azimuth, the b-axis <010> azimuth, or the c-axis <001> azimuth is an azimuth within a range of plus or minus 10 degrees with respect to each azimuth. Item 9. The β-Ga ₂ O ₃ -based single crystal growth method according to Item 8. The β-Ga ₂ O ₃ -based seed crystal has a diameter that is 1/5 or less of a grown crystal, and has a strength that does not break during the growth of the β-Ga ₂ O ₃ -based single crystal. The β-Ga ₂ O ₃ -based single crystal growth method according to claim 1. The β-Ga ₂ O ₃ -based seed crystal has a cross-sectional area of 5 mm ² or less, and has a strength that does not break during the growth of the β-Ga ₂ O ₃ -based single crystal. The β-Ga ₂ O ₃ -based single crystal growth method described. 2. The β-Ga ₂ O ₃ seed crystal includes the same monoclinic system as β-Ga ₂ O ₃ and a β-Ga ₂ O ₃ solid solution whose space group belongs to C2 / m. The β-Ga ₂ O ₃ -based single crystal growth method described. The β-Ga ₂ O ₃ single crystal includes the same monoclinic system as β-Ga ₂ O ₃ and a β-Ga ₂ O ₃ solid solution whose space group belongs to C2 / m. The β-Ga ₂ O ₃ -based single crystal growth method described. The β-Ga ₂ O ₃ solid solution is gallium, indium, aluminum, tin, germanium, nickel, copper, zinc, zirconium, niobium, molybdenum, titanium, vanadium, chromium, manganese, iron, cobalt, hafnium, tantalum, tungsten, The β-Ga ₂ O ₃ -based single crystal growth method according to claim 12 or 13, comprising an oxide of one or more elements selected from the group consisting of silicon and magnesium.

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