JP5229735B2 - Method for producing AlN crystal - Google Patents

Description

  The present invention relates to a novel method for producing AlN crystals.

  Compound semiconductor devices are used for power devices and high-luminance light-emitting devices. The characteristics required for the substrate of a power device or a high-intensity light emitting device include that the compound semiconductor and the lattice constant are matched, that the band gap is large, and that heat dissipation is good. Conventionally, a compound semiconductor device is formed by forming a buffer layer with a devised structure on a Si single crystal substrate or a sapphire substrate, and forming a compound semiconductor layer on the buffer layer.

As described above, in the conventional method, it is necessary to form a buffer layer with a devised structure between the substrate and the semiconductor layer. For this reason, the manufacturing cost was high.
On the other hand, since AlN has a large band gap in the ultraviolet region, high thermal conductivity, and good lattice constant matching with AlGaN, etc., a buffer layer is formed when AlN is used as a substrate of a compound semiconductor device. There is no need to do. However, an AlN crystal with good crystallinity could not be grown to a sufficient size.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel method for producing an AlN crystal capable of growing an AlN crystal having good crystallinity.

When the present inventors insert either Al or an element whose free energy of formation of nitride is smaller than Al into the same container and heat it in a nitrogen atmosphere to melt Al, this element is used as a catalyst for Al and It was found that nitrogen in the atmosphere reacted to produce AlN. For example, when BN is used, it is considered that AlB ₁₂ that is a compound of Al and B is first generated. And N couple | bonds with B contained in AlB ₁₂ , and AlN produces | generates by passing to Al after that.

The present invention has been made based on this finding. That is, in the method for producing an AlN crystal according to the present invention, the seed crystal is brought into contact with molten Al located under a nitrogen atmosphere,
An element having a free energy of formation of nitride smaller than Al is supplied to the interface between the seed crystal and the molten Al.
An AlN crystal is grown on the seed crystal by reacting nitrogen dissolved in the molten Al and the molten Al using the element as a catalyst.

  The element is at least one selected from the group consisting of, for example, boron, calcium, silicon, iron, molybdenum, chromium, vanadium, magnesium, manganese, indium, gallium, tantalum, hafnium, and thorium. The nitrogen atmosphere is preferably 4 atm or more. Moreover, it is preferable that the temperature of the interface between the molten Al and the seed crystal is 800 ° C. or higher. The element may be supplied to the interface between the seed crystal and the molten Al by mixing a gas of a compound containing the element in the nitrogen atmosphere and dissolving the gas in the molten Al.

  According to the present invention, an AlN crystal can be produced by a novel method.

The longitudinal cross-sectional schematic for demonstrating the structure of the AlN manufacturing apparatus used with the manufacturing method of AlN which concerns on 1st Embodiment. The longitudinal cross-sectional schematic for demonstrating the structure of the AlN manufacturing apparatus used with the manufacturing method of AlN which concerns on 2nd Embodiment.

Explanation of symbols

2 ... Molten Al
4 ... Seed crystal 10 ... Container 20 ... Heater 30 ... Seed crystal holding unit 32 ... Al supply unit 34 ... Catalytic element supply unit 50 ... Chamber 52 ... Nitrogen gas supply unit 54 ... Pump 56 ... Catalyst element-containing gas supply unit

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view for explaining the configuration of an AlN manufacturing apparatus used in an AlN manufacturing method according to the first embodiment of the present invention. This AlN manufacturing apparatus includes a container 10 that holds molten Al2, a heater 20 that heats molten Al in the container 10, a seed crystal holding unit 30 that holds a seed crystal 4, an Al supply unit 32 that supplies Al6 to the molten Al2, And a catalytic element supply unit 34 for supplying a substance (hereinafter referred to as a catalyst element-containing material) containing an element functioning as a catalyst (hereinafter referred to as a catalyst element) to molten Al. Each of these components is disposed in the chamber 50. The interior of the chamber 50 can be a nitrogen atmosphere pressurized by the nitrogen gas supply unit 52. The inside of the chamber 50 can be evacuated by a pump 54.

The catalytic element is an element whose free energy of formation of nitride is smaller than Al, and is made of, for example, boron, calcium, silicon, iron, molybdenum, chromium, vanadium, magnesium, manganese, indium, gallium, tantalum, hafnium, and thorium. At least one selected from the group. The catalyst element-containing material may be a single element, nitride (eg, BN, Si ₃ N ₄ , or Ca ₃ N ₂ ), or carbide (eg, B ₄ C). Also good.

The seed crystal is, for example, an AlN crystal, and has the same hexagonal crystal structure as AlN, and the lattice constant based on the lattice constant of AlN is 65% to 135% or 150% to 250. % Or less of the material, and a crystal (for example, Si ₃ N ₄ , BN, or GaN) made of a material whose generation free energy is closer to that of AlN. When the lattice constant of the seed crystal is 65% or more and 135% or less of the lattice constant of AlN, the lattice of the seed crystal and the AlN crystal match one to one, and the lattice constant of the seed crystal is 150% or more of the lattice constant of AlN. In the case of 250% or less, the seed crystal and the AlN crystal have a one-to-two lattice match.

  Next, a method of manufacturing AlN using the AlN manufacturing apparatus of FIG. 1 will be described. First, an Al piece is inserted into the container 10. Next, after the inside of the chamber 50 is evacuated by the pump 54, the nitrogen gas is supplied into the chamber 50 by the nitrogen gas supply unit 52. Thereby, the inside of the chamber 50 becomes a nitrogen atmosphere. The pressure in the nitrogen atmosphere is preferably 4 atm or more and 30 atm or less, but may be normal pressure. Next, a predetermined amount of the catalyst element-containing material is supplied into the container 10, and the Al piece is melted using the heater 20. Thereby, molten Al 2 in which the catalytic element is dissolved is generated in the container 10. The temperature of the molten Al 2 at this time is preferably 800 ° C. or higher and 1300 ° C. or lower.

  Next, the lower surface of the seed crystal 4 is immersed in the molten Al 2 while rotating the seed crystal 4 held by the seed crystal holding unit 30. A catalytic element is located at the interface between the seed crystal 4 and the molten Al2. In this state, the catalytic element reacts with nitrogen dissolved in molten Al2 and is nitrided. As described above, the catalytic element has a smaller free energy of formation of nitride than aluminum. For this reason, the nitrogen combined with the catalytic element is transferred to the aluminum, and the aluminum is nitrided. In this way, the nitriding reaction of aluminum using the catalyst element as a catalyst proceeds, whereby an AlN crystal grows on the seed crystal 4. During the growth of the AlN crystal, the concentration of the catalytic element contained in the molten Al 2 is controlled to an optimum value by appropriately adding Al 6 and a catalytic element-containing material by the Al supply unit 32 and the catalytic element supply unit 34. Thereby, the growth of the AlN crystal in the seed crystal 4 is continued, and an AlN crystal rod is generated. Further, by adjusting the conditions, a single crystal rod of AlN can be generated.

  The temperature of the molten Al and the pressure of the nitrogen atmosphere are set to the conditions just before the AlN formation reaction occurs, and a heating means (not shown) is used to heat the temperature at the interface between the seed crystal 4 and the molten Al 2. Only the temperature at the interface may be raised.

  As described above, according to the present embodiment, an AlN crystal rod can be generated by a pulling method (CZ method). Further, by adjusting the conditions, a single crystal rod of AlN can be generated.

  FIG. 2 is a schematic vertical cross-sectional view for explaining the configuration of an AlN manufacturing apparatus used in the AlN manufacturing method according to the second embodiment of the present invention. The AlN production apparatus shown in the figure has the same configuration as the AlN production apparatus according to the first embodiment except that a catalyst element-containing gas supply unit 56 is provided instead of the catalyst element supply unit 34. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The catalyst element-containing gas supply unit 56 mixes a compound gas containing a catalyst element (for example, B ₂ H ₆ or SiH ₄ ) in a nitrogen atmosphere. By dissolving these gases in molten Al, the catalyst element is dissolved in molten Al.

The method for producing AlN according to the present embodiment relates to the first embodiment except that the catalyst element is dissolved in molten Al using the catalyst element-containing gas supply unit 56 instead of the catalyst element supply unit 34. It is the same as the manufacturing method of AlN.
According to this embodiment, the same effect as that of the first embodiment can be obtained.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

Claims (4)

Bringing the seed crystal into contact with molten Al located under a nitrogen atmosphere;
An element having a free energy of formation of nitride smaller than Al is supplied to the interface between the seed crystal and the molten Al.
By reacting nitrogen dissolved in the molten Al with the element as a catalyst and the molten Al, an AlN crystal is grown on the seed crystal ,
The elements Ru silicon, iron, molybdenum, chromium, vanadium, manganese, indium, gallium, tantalum, hafnium, and at least one Der selected from the group consisting of thorium, method of manufacturing AlN crystal. The method for producing an AlN crystal according to claim 1, wherein the nitrogen atmosphere is set to 4 atm or more. The method for producing an AlN crystal according to claim 1 or 2 , wherein a temperature at an interface between the molten Al and the seed crystal is 800 ° C or higher. The nitrogen atmosphere, is mixed gas of a compound containing the element, said by Komu dissolving the gas in the molten Al, either the seed crystal and the melt Al interface of claim 1 to 3 which supplies the elements of The method for producing an AlN crystal according to claim 1.

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