JP4774959B2 - Method for growing AlN single crystal - Google Patents

Description

  The present invention relates to an AlN single crystal growth method and an AlN single crystal, and in particular, an AlN single crystal capable of growing a high-purity AlN single crystal and reducing variation in growth rate for each growth of the AlN single crystal. And an AlN single crystal obtained by the method.

  The present invention also relates to an AlN single crystal growth method and an AlN single crystal. In particular, when a transition metal and / or carbon is mixed in an AlN single crystal, the AlN single crystal is mixed into the AlN single crystal every time it grows. The present invention relates to an AlN single crystal growth method capable of reducing variations in the amount of transition metal and / or carbon, and an AlN single crystal obtained by the method.

  Among Group III nitride crystals, AlN (aluminum nitride) single crystal has a wide energy band gap of 6.2 eV, high thermal conductivity, and high electrical resistance, and therefore, semiconductors such as various optical devices and electronic devices. It is attracting attention as a substrate material for devices.

In general, an AlN single crystal is grown by a sublimation method. The sublimation method is performed as follows, for example. First, an AlN polycrystalline raw material and a seed crystal are placed in a growth chamber inside a crucible installed inside a reaction tube so as to face each other, and the AlN polycrystalline raw material is heated to a temperature at which the AlN polycrystalline raw material sublimes. . By this heating, the AlN polycrystalline raw material is sublimated to generate a sublimation gas. The sublimation gas comes into contact with the surface of the seed crystal set at a low temperature, and the AlN single crystal grows by crystallization of the AlN single crystal on the surface of the seed crystal. During the growth of the AlN single crystal, nitrogen gas having an appropriate pressure and flow rate is introduced into the reaction tube according to the purpose.
US Pat. No. 5,858,086 Japanese Patent Laid-Open No. 10-53495 M. Bickermann, BMEpelbaum, A. Winnacker, “Characterization of bulk AlN with low oxygen content”, Journal of Crystal Growth, 269, 2004, p.432-442 Lianghong Liu, James H. Edgar, “Transport effects in the sublimation growth of aluminum nitride”, Journal of Crystal Growth, 220, 2000, p.243-253

However, the AlN polycrystalline raw material used in the sublimation method generally contains oxygen impurities of several hundred ppm or more. This oxygen impurity is present in the form of stable Al ₂ O ₃ . Since Al ₂ O ₃ is more easily sublimated than AlN, Al ₂ O ₃ appearing on the surface of the AlN polycrystalline raw material is quickly sublimated, and oxygen gas is mixed into the gas phase atmosphere inside the growth chamber. Thus, when oxygen gas is mixed with the gas phase atmosphere inside the growth chamber, oxygen is taken into the grown AlN single crystal as an impurity. Oxygen incorporated into the AlN single crystal is not preferable because it decreases the thermal conductivity of the AlN single crystal (see, for example, Non-Patent Document 1).

  The oxygen concentration taken into the AlN single crystal is lower than the oxygen concentration in the atmospheric gas. Therefore, when oxygen is continuously supplied from the AlN polycrystalline material, the oxygen concentration of the atmospheric gas inside the growth chamber continues to increase. In other words, even if the concentration of oxygen impurities contained in the AlN polycrystalline raw material is several hundred ppm, the oxygen concentration of the atmospheric gas inside the growth chamber is on the order of magnitude as the growth of the AlN single crystal proceeds. It gets bigger.

  As the oxygen concentration of the atmospheric gas inside the growth chamber increases, the amount of oxygen taken into the AlN single crystal also increases. However, when the amount of oxygen taken into the AlN single crystal exceeds a certain critical value, oxygen does not dissolve in the AlN single crystal, but a solid phase having another crystal structure containing oxygen. Crystallize. Thus, the appearance of a crystal other than the AlN single crystal becomes the nucleus of polycrystallization of the AlN crystal, and therefore it is necessary to avoid it when growing the AlN single crystal.

  For example, in Patent Document 1, an AlN single crystal source gas discharge port is arranged in the vicinity of a seed crystal, and the gas near the crystal growth interface is discharged to increase the growth rate and improve the purity of the AlN single crystal. (See FIG. 4 of Patent Document 1). This method is a method in which a part of the raw material gas that has been transported from the raw material side to the vicinity of the crystal growth interface by diffusion (and convection) is solidified at the crystal growth interface and the remaining part is discharged to the outside, such as oxygen Can be effectively prevented from being incorporated into the AlN single crystal.

  However, this method has a problem that the growth rate of the AlN single crystal varies depending on the discharge efficiency of the source gas. Although the exhaust efficiency of the source gas is controlled by the size of the discharge port, etc., the controllability is not necessarily high, so there is a problem that the growth rate of the AlN single crystal varies greatly every time the AlN single crystal grows. there were. In this way, when the growth rate for each growth of the AlN single crystal varies greatly, the timing for stopping the growth of the AlN single crystal cannot be grasped, which greatly hinders the manufacturing process of the AlN single crystal.

  Further, Patent Document 2 discloses a method of growing an AlN single crystal by a sublimation method using an AlN polycrystalline raw material mixed with an oxide of a transition metal, and mixing the transition metal into the AlN single crystal. (See Example 1 of Patent Document 2). The transition metal mixed in the AlN single crystal captures oxygen in the AlN single crystal, reduces the amount of oxygen uniformly distributed in the AlN single crystal, and reduces the deterioration of the characteristics of the AlN single crystal due to the mixing of oxygen. Has an effect. Further, even when carbon is mixed in the AlN single crystal, it is considered that the same effect as that obtained when a transition metal is mixed in the AlN single crystal can be obtained.

  However, when a transition metal and / or carbon is mixed in an AlN single crystal using the method disclosed in Patent Document 2, the amount of transition metal mixed in the AlN single crystal for each growth of the AlN single crystal And / or the variation in the amount of carbon becomes large, and it is difficult to mix the transition metal and / or carbon into the AlN single crystal while controlling to a desired amount.

The present invention includes a step of installing an AlN polycrystalline raw material inside a growth chamber, a step of heating and sublimating the AlN polycrystalline raw material, and a step of growing an AlN single crystal on the surface of a seed crystal inside the growth chamber. The nitrogen partial pressure outside the growth chamber is higher than the nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material inside the growth chamber, and the gas inside and outside the growth chamber An opening capable of exchange is provided in the growth chamber to grow an AlN single crystal, and the opening is provided closer to the AlN polycrystalline material than the seed crystal and only at a position where the seed crystal is not directly seen. It is a growth method of an AlN single crystal.

  Here, in the AlN single crystal growth method of the present invention, the opening can be provided at the back of the AlN polycrystalline raw material as seen from the seed crystal.

  In the AlN single crystal growth method of the present invention, the growth chamber is composed of an AlN polycrystal raw material storage part and an AlN single crystal growth part, and the AlN polycrystal raw material storage part is larger than the AlN single crystal growth part. The volume may be large, and an opening may be provided in the AlN polycrystalline raw material container.

  In the AlN single crystal growth method of the present invention, it is preferable that 10% or more and 100% or less of the grown AlN single crystal in the AlN polycrystalline raw material is exhausted.

  ADVANTAGE OF THE INVENTION According to this invention, the growth method of the AlN single crystal which can grow a high purity AlN single crystal and can reduce the dispersion | variation in the growth rate for every growth of an AlN single crystal, and AlN obtained by the method Single crystals can be provided.

  Further, according to the present invention, when a transition metal and / or carbon is mixed in an AlN single crystal, variation in the amount of transition metal and / or carbon mixed in the AlN single crystal for each growth of the AlN single crystal is reduced. An AlN single crystal growth method that can be reduced and an AlN single crystal obtained by the method can be provided.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

  The AlN single crystal growth method of the present invention comprises a step of placing an AlN polycrystal raw material inside a growth chamber, a step of heating and sublimating the AlN polycrystal raw material, and a surface of a seed crystal inside the growth chamber. A step of growing an AlN single crystal, wherein the nitrogen partial pressure outside the growth chamber is made higher than the nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material inside the growth chamber, An opening that allows exchange of gas inside and outside is provided in the growth chamber to grow an AlN single crystal, the opening is closer to the AlN polycrystalline material than the seed crystal, and the seed crystal is not seen directly It is characterized by being provided at a position.

  As in the conventional method disclosed in Patent Document 1, it is presumed that a high-purity AlN single crystal can be obtained by exhausting a gas containing oxygen from the vicinity of the growth interface of the AlN single crystal. The growth rate of the AlN single crystal varies greatly due to the influence of exhaust. Therefore, as a result of intensive studies by the present inventor, as in the present invention, even when the opening is provided closer to the AlN polycrystalline material than the seed crystal and at a position where the seed crystal is not directly seen, It has been found that a high-purity AlN single crystal similar to the method disclosed in Document 1 can be obtained. That is, as described above, as the growth of the AlN single crystal proceeds, the oxygen concentration near the growth interface of the AlN single crystal increases. Therefore, oxygen in the vicinity of the growth interface of the AlN single crystal diffuses to the AlN polycrystalline material side. Therefore, it is considered that the gas containing oxygen can be exhausted even when the opening is provided at the position of the present invention. Therefore, in the present invention, a high-purity AlN single crystal can be grown by exhausting a gas containing oxygen, which is an impurity, and an AlN single crystal can be grown without being affected by this exhaust. Variations in the growth rate for each growth can be reduced.

  Here, in the present invention, the growth of the AlN single crystal is achieved by increasing the nitrogen partial pressure outside the growth chamber to be higher than the nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material inside the growth chamber. Done.

  In the present invention, “the nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material inside the growth chamber” is obtained by the following formula (1) with reference to Non-Patent Document 2. it can.

P _Al (P _N2 ) ^1/2 = exp (AB / T) (1)
In formula (1), P _Al represents the partial pressure of the aluminum gas inside the growth chamber, and P _N2 represents the partial pressure of the nitrogen gas inside the growth chamber. In the formula (1), A = 27.055, B = 75788, and T is the temperature (K) of the AlN polycrystalline material inside the growth chamber. Here, since the stoichiometric composition of AlN is Al: N ₂ = 2: 1, by calculating P _N2 from the formula (1) with P _Al = 2P _N2 , “inside the growth chamber” The nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material can be obtained.

  In the present invention, the opening is provided closer to the AlN polycrystalline material than the seed crystal and at a position where the seed crystal is not seen directly. Here, in the present invention, the “position where the seed crystal is not directly seen” means that the seed crystal and the AlN polycrystalline raw material installed inside the growth chamber are assumed to pass through the opening from the outside of the growth chamber. When looking inside the growth chamber, it means a position where the seed crystal cannot be directly seen from the opening due to, for example, the physical position of the opening and / or the presence of an AlN polycrystalline raw material.

  Further, the opening can be provided by, for example, forming a hole penetrating a part of the wall surface of the growth chamber in order to exchange the gas inside and outside the growth chamber.

  In the present invention, it is preferable that 10% or more and 100% or less of the grown AlN single crystal in the AlN polycrystalline raw material is exhausted from the opening. When the mass of the AlN polycrystal raw material to be evacuated is less than 10% of the mass of the grown AlN single crystal, the effect of providing the opening tends not to be obtained sufficiently, and when it is more than 100% The amount of exhaust is too large, and even if the exhaust opening is disposed at the position defined by the present invention, the growth rate of the AlN single crystal on the seed crystal tends to decrease.

  In addition, the AlN single crystal growth method of the present invention includes a step of installing an AlN polycrystalline raw material inside a growth chamber, a step of heating and sublimating the AlN polycrystalline raw material, and a surface of a seed crystal inside the growth chamber. A step of growing an AlN single crystal on the substrate, wherein the nitrogen partial pressure outside the growth chamber is made higher than the nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material inside the growth chamber, The growth chamber is provided with an opening that enables exchange of gas inside and outside the growth chamber, and a gas generation chamber that generates a gas containing at least one selected from the group consisting of transition metals and carbon is defined as a growth chamber. In another feature, the gas generation chamber is connected to the growth chamber, and the AlN single crystal is grown while introducing the gas from the gas generation chamber into the growth chamber.

  As described above, when the transition metal and / or carbon is mixed in the AlN single crystal using the method disclosed in the conventional patent document 2, the AlN single crystal is mixed in every growth of the AlN single crystal. The variation of the amount of transition metal and / or carbon to be increased becomes large, and it is difficult to mix the transition metal and / or carbon into the AlN single crystal while controlling the amount of the transition metal and / or carbon to a desired amount. However, in the present invention, a gas generation chamber that generates a gas containing at least one selected from the group consisting of a transition metal and carbon is provided separately from the growth chamber, the gas generation chamber is connected to the growth chamber, Gas from the generation chamber is introduced into the growth chamber. In addition to this, growth is achieved by growing an AlN single crystal while exhausting part of the gas inside the growth chamber to the outside of the growth chamber through an opening that allows exchange of gas inside and outside the growth chamber. Controllability of the amount of transition metal and / or carbon in the chamber is remarkably improved.

  The reason for this is that the concentration of each gas inside the growth chamber depends on the local equilibrium between the surface of the AlN polycrystal raw material and the gas generation chamber, between the gas generation chamber and the growth chamber, between the growth chamber and the outside of the growth chamber. This is considered to be uniquely determined by gas transportation. Here, the connection between the growth chamber and the gas generation chamber is, for example, provided with openings for connection in a part of the growth chamber and a part of the gas generation chamber, and these openings are made of a hollow member or the like. It can be performed by a method of connecting with a connecting portion. In addition, the gas transport efficiency is determined by the size and / or shape of the opening provided in the growth chamber in order to enable the exchange of gas inside and outside the growth chamber, and the connection between the gas generation chamber and the growth chamber. Therefore, it can be controlled by appropriately setting the size and / or shape of the openings provided in the gas generation chamber and the growth chamber, respectively. Therefore, the concentration of the transition metal and / or carbon-containing gas inside the growth chamber can be set as appropriate. In addition, as a transition metal used for this invention, at least 1 sort (s) selected from the group which consists of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu can be used, for example.

  Further, in the present invention, the opening provided in the growth chamber for connection with the gas generation chamber is an opening provided in the growth chamber to enable exchange of gas inside and outside the growth chamber. It is preferable that it is in a position far from the seed crystal as compared with. In this case, the concentration of the gas containing the transition metal and / or carbon in the growth chamber tends to be suppressed from becoming too high.

  In the present invention, in order to connect the gas generation chamber and the growth chamber, the temperature of the connecting portion connecting the openings provided in the gas generation chamber and the growth chamber is set higher than the temperature of the AlN polycrystalline raw material. It is preferable to grow an AlN single crystal.

  In the present invention, the growth of the AlN single crystal may be started without previously setting a seed crystal inside the growth chamber. In this case, the growth temperature of the growth chamber is low at the initial stage of the growth start of the AlN single crystal. The crystal nucleus formed in the part is regarded as a seed crystal.

Example 1
An AlN single crystal was grown using the apparatus shown in the schematic sectional view of FIG. This apparatus includes a reaction tube 1, a graphite crucible 2 installed in the reaction tube 1, a growth chamber 3 installed in the crucible 2, and a heat insulating material 6 installed on the outer periphery of the crucible 2. And a high-frequency heating coil 7 surrounding the outer periphery of the reaction tube 1. A gas exhaust port 9 is provided at the upper part of the reaction tube 1, and a gas introduction port 8 is provided at the lower part of the reaction tube 1. In addition, a radiation thermometer 10 is installed on each of the upper and lower portions of the reaction tube 1. Furthermore, an opening 4 is provided in a part of the lower surface of the growth chamber 3, and an exhaust hole 5 is provided in a part of the side surface of the crucible 2, and the gas exhausted from the opening 4 is the growth chamber 3 and the crucible 2. After passing through a space provided between the crucible and the heat insulating material 6, it passes through the exhaust hole 5 and is discharged into the reaction tube 1 through the space provided between the crucible 2 and the heat insulating material 6. Here, the opening 4 was formed in a circular shape having a diameter of 4 mm, and its length (the thickness of the lower wall of the growth chamber 3) was 3 mm.

  An AlN single crystal having a diameter of 30 mm, a thickness of 0.25 mm and a plane orientation (0001) is installed as a seed crystal 12 on the upper surface of the growth chamber 3 of this apparatus, and the oxygen concentration is 500 ppm and the mass is 100 g on the lower surface of the growth chamber 3. The AlN polycrystalline raw material 11 was installed. At this time, the opening 4 is provided on the back of the AlN polycrystalline raw material 11 when viewed from the seed crystal 12. Therefore, the opening 4 is installed at a position closer to the AlN polycrystalline raw material 11 than the seed crystal 12, and when looking into the inside of the growth chamber 3 from the opening 4, the AlN polycrystalline raw material 11 directly connects the seed crystal 12. I couldn't see it.

  While introducing 100 sccm of nitrogen gas from the gas inlet 8 into the reaction tube 1, the gas was discharged from the gas exhaust port 9, and the pressure inside the reaction tube 1 was maintained at 700 torr. Then, the upper surface of the crucible 2 is heated by the high frequency heating coil 7 to 2100 ° C. and the lower surface of the crucible 2 is 2000 ° C. to sublimate the AlN polycrystal raw material 11 and held at that temperature for 1 hour. The position of the crucible 2 and the heating power were adjusted so that the upper surface was 2000 ° C. and the lower surface of the crucible 2 was 2100 ° C., and the growth of the AlN single crystal on the surface of the seed crystal 12 was started. Here, the temperatures of the upper surface and the lower surface of the crucible 2 were measured by the radiation thermometer 10, respectively.

Then, after 100 hours had elapsed from the start of growth of the AlN single crystal, it was cooled to room temperature, and the AlN single crystal was taken out from the growth chamber 3. Here, from the formula P _Al (P _N2 ) ^1/2 = exp (AB / T), the stoichiometric composition of AlN when the temperature of the AlN polycrystalline material 11 inside the growth chamber 3 is 2100 ° C. When the partial pressure of nitrogen is calculated, P _N2 = 0.024 atm and the pressure outside the growth chamber 3 becomes 700 torr (= 0.92 atm), so that AlN at the temperature of the AlN polycrystalline raw material 11 inside the growth chamber 3 becomes AlN. It was confirmed that the AlN single crystal was grown in a state where the nitrogen partial pressure outside the growth chamber 3 was higher than the nitrogen partial pressure of the stoichiometric composition.

  In Example 1, the reduction amount of the AlN polycrystalline raw material 11 was 72 g, and the mass of the AlN single crystal grown on the surface of the seed crystal was 54 g. From this, it was found that the mass of the gas exhausted from the inside of the growth chamber 3 was 18 g. Further, the AlN single crystal grown in Example 1 was cut out, and the oxygen concentration at the center of the AlN single crystal was measured by secondary ion mass spectrometry (SIMS), and found to be 150 ppm.

(Comparative Example 1)
An AlN single crystal was grown under the same conditions as in Example 1 except that the apparatus shown in the schematic cross-sectional view of FIG. 3 was used. Here, the opening 4 of the apparatus shown in FIG. 3 was installed on both sides of the seed crystal 12. Therefore, in Comparative Example 1, the opening 4 is installed at a position closer to the seed crystal 12 than the AlN polycrystalline raw material 11. The openings 4 were each formed in a circular shape having a diameter of 2 mm, and the length of each opening 4 (the thickness of the upper wall of the growth chamber 3) was 3 mm.

  In Comparative Example 1, the reduction amount of the AlN polycrystalline raw material 11 was 70 g, and the mass of the AlN single crystal grown on the surface of the seed crystal was 49 g. From this, it was found that the mass of the gas exhausted from the inside of the growth chamber 3 was 21 g. Moreover, when the AlN single crystal grown in Comparative Example 1 was cut out and the oxygen concentration at the center of the AlN single crystal was measured by the same method as in Example 1, it was 140 ppm. Therefore, it was confirmed that the amount of oxygen taken into the AlN single crystal was hardly changed between Comparative Example 1 and Example 1.

(Example 2)
In order to investigate the variation in the growth rate for each growth of the AlN single crystal, an AlN single crystal is grown five times under the same conditions as in Example 1 using the apparatus shown in FIG. 1, and the growth rate of each AlN single crystal is determined. Examined. The results are shown in Table 1. The members such as the crucible 2 and the growth chamber 3 installed inside the reaction tube 1 shown in FIG. 1 were exchanged for every growth of the AlN single crystal.

  As shown in Table 1, the average growth rate of the AlN single crystal in Example 2 was 0.516 (g / h), and the dispersion was 0.003344.

(Example 3)
Using the apparatus shown in the schematic cross-sectional view of FIG. 2, an AlN single crystal was grown five times in the same manner as in Example 2 except that an AlN polycrystalline material 11 having a mass of 250 g was used. The growth rate was examined. The results are shown in Table 1.

  In the apparatus shown in FIG. 2, the growth chamber 3 is composed of an AlN polycrystal raw material storage unit 3a and an AlN single crystal growth unit 3b, and the AlN polycrystal raw material storage unit 3a is larger in volume than the AlN single crystal growth unit 3b. Was set larger. Moreover, the opening part 4 was provided in the both sides | surfaces of the AlN polycrystal raw material accommodating part 3a. Therefore, the opening 4 is located closer to the AlN polycrystalline raw material 11 than the seed crystal 12, and even when the inside of the growth chamber 3 is viewed from the outside of the growth chamber 3 through the opening 4, the opening 4 is physically present. The seed crystal 12 could not be seen directly depending on the position. The openings 4 were each formed in a circular shape having a diameter of 2 mm, and the length of each opening 4 (thickness of the side wall of the growth chamber 3) was 2 mm.

  As shown in Table 1, the average growth rate of the AlN single crystal in Example 3 was 0.564 (g / h), and the dispersion was 0.001264.

(Comparative Example 2)
The AlN single crystal was grown five times in the same manner as in Example 2 except that the apparatus shown in FIG. 3 was used, and the growth rate of each AlN single crystal was examined. The results are shown in Table 1.

  As shown in Table 1, the average growth rate of the AlN single crystal in Comparative Example 2 was 0.456 (g / h), and the dispersion was 0.010384. Therefore, in Comparative Example 2, since the dispersion is larger than in Example 2 and Example 3, it was confirmed that the variation in the growth rate for each growth of the AlN single crystal was increased.

Example 4
By changing the diameter of the opening 4 of the apparatus shown in FIG. 1, the amount of gas exhausted was variously adjusted to grow an AlN single crystal. Then, for each growth of the AlN single crystal, the growth rate and oxygen concentration of the AlN single crystal were investigated. The results are shown in Table 2. Here, the diameter of the opening 4 was changed every time the AlN single crystal was grown. The growth conditions of the AlN single crystal were the same as those in Example 1 in all growths, and the oxygen concentration in the AlN single crystal was investigated by the same method as in Example 1. In Table 2, the displacement (%) value was calculated by the following equation (2).
Displacement (%) = 100 × (Reduction in mass of AlN polycrystal raw material−Mass of grown AlN single crystal) / (Mass of grown AlN single crystal) (2)

  As shown in Table 2, when less than 10% of the mass of the grown AlN single crystal is exhausted among the AlN polycrystalline raw materials, the oxygen concentration in the AlN single crystal tends to increase, and the grown AlN When more than 100% of the mass of the single crystal was exhausted, the oxygen concentration in the AlN single crystal decreased somewhat, but the growth rate of the AlN single crystal tended to decrease greatly. Further, it was found that, when the AlN polycrystal raw material exhausted 10% or more and 100% or less of the mass of the grown AlN single crystal, a high purity AlN single crystal having a low oxygen concentration can be grown at a high growth rate. .

(Example 5)
An AlN single crystal was grown five times using the apparatus shown in the schematic cross-sectional view of FIG. The apparatus shown in FIG. 4 is characterized in that a gas generation chamber 13 is provided below the growth chamber 3 separately from the growth chamber 3 and connected to the growth chamber 3.

  Here, in the apparatus shown in FIG. 4, an opening 15 a for connecting to the gas generation chamber 13 is provided on the lower surface of the growth chamber 3, and an opening for connecting to the growth chamber 3 on the upper surface of the gas generation chamber 13. 15b is provided. The opening 15a and the opening 15b are connected to each other by a connecting portion 14 including a wall surface of a hollow portion of a plate-like member constituting the lower surface of the growth chamber 3 and the upper surface of the gas generation chamber 13. In addition, carbon 16 is installed inside the gas generation chamber 13, and the gas generation chamber 13 is heated by using the high-frequency heating coil 7, whereby a gas containing carbon from the gas generation chamber 13 to the inside of the growth chamber 3. An AlN single crystal was grown on the surface of the seed crystal 12 while introducing. Here, in the AlN single crystal, the temperature of the connecting portion 14 that connects the opening 15 a provided in the growth chamber 3 and the opening 15 b provided in the gas generation chamber 13 is higher than the temperature of the AlN polycrystalline raw material 11. It was grown in the state.

  In addition, in the apparatus shown in FIG. 4, the opening 15 a provided in the growth chamber 3 for connection to the gas generation chamber 13 includes an opening 4 that enables exchange of gas inside and outside the growth chamber 3. Compared to the seed crystal 12, it was far from the seed crystal 12.

  Also here, the opening 4 is closer to the AlN polycrystalline material 11 than the seed crystal 12, and even when the inside of the growth chamber 3 is viewed from the outside of the growth chamber 3 through the opening 4, The seed crystal 12 could not be seen directly depending on the physical position. The openings 4 were each formed in a circular shape having a diameter of 2 mm, and the length of each opening 4 (thickness of the side wall of the growth chamber 3) was 2 mm.

  Except for the above, an AlN single crystal was grown by the same method and the same conditions as in Example 1.

  Then, when the carbon concentration in each grown AlN single crystal was measured by an inert gas melting-infrared detection method, all the carbon concentrations were in the range of 250 ± 50 ppm, and AlN for each growth of the AlN single crystal. It was confirmed that the carbon concentration in the single crystal was small and the amount of carbon in the AlN single crystal was well controlled.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The AlN single crystal obtained by the AlN single crystal growth method of the present invention includes, for example, a light emitting device (light emitting diode, laser diode, etc.), an electronic device (rectifier, bipolar transistor, field effect transistor, HEMT (high electron mobility transistor)). Etc.), semiconductor sensors (temperature sensors, pressure sensors, radiation sensors, visible-ultraviolet light detectors, etc.), SAW (surface acoustic wave) devices, acceleration sensors, MEMS (micromachine) parts, piezoelectric vibrators, resonators or piezoelectric actuators It can be used as a substrate.

It is typical sectional drawing of a preferable example of the apparatus used for the growth method of the AlN single crystal of this invention. It is typical sectional drawing of another preferable example of the apparatus used for the growth method of the AlN single crystal of this invention. It is typical sectional drawing of the apparatus used for the growth method of the conventional AlN single crystal. FIG. 6 is a schematic cross-sectional view of still another preferred example of an apparatus used in the AlN single crystal growth method of the present invention.

Explanation of symbols

  1 reaction tube, 2 crucible, 3 growth chamber, 3a AlN polycrystal raw material container, 3b AlN single crystal growth part, 4 opening, 5 exhaust hole, 6 heat insulating material, 7 high frequency heating coil, 8 gas inlet, 9 gas Exhaust port, 10 radiation thermometer, 11 AlN polycrystal raw material, 12 seed crystals, 13 gas generation chamber, 14 connecting part, 15a, 15b opening, 16 carbon.

Claims (4)

A step of installing an AlN polycrystalline raw material inside the growth chamber, a step of heating and sublimating the AlN polycrystalline raw material, a step of growing an AlN single crystal on the surface of a seed crystal inside the growth chamber, Including
Exchange of the gas inside and outside the growth chamber by making the nitrogen partial pressure outside the growth chamber higher than the nitrogen partial pressure of the stoichiometric composition of AlN at the temperature of the AlN polycrystalline raw material inside the growth chamber. An opening for enabling the growth is provided in the growth chamber to grow an AlN single crystal,
The method of growing an AlN single crystal, wherein the opening is provided closer to the AlN polycrystal raw material than the seed crystal and only at a position where the seed crystal is not directly seen.   2. The method for growing an AlN single crystal according to claim 1, wherein the opening is provided on a back portion of the AlN polycrystalline raw material when viewed from the seed crystal. The growth chamber is composed of an AlN polycrystal raw material storage part and an AlN single crystal growth part,
The AlN polycrystalline raw material container has a larger volume than the AlN single crystal growth part,
The method for growing an AlN single crystal according to claim 1, wherein the opening is provided in the AlN polycrystalline raw material container.   4. The method for growing an AlN single crystal according to claim 1, wherein a mass of 10% to 100% of the grown AlN single crystal is exhausted from the AlN polycrystalline raw material. 5.

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