JP2013203594A - Method for producing nitride crystal of group 13 metal in periodic table - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nitride crystal of a group 13 metal in the periodic table capable of progressing crystal growth stably for long hours by suppressing decline of growth speed of the crystal generated in a liquid phase growth method of the nitride crystal of the group 13 metal in the periodic table.SOLUTION: In a crystal growth process of a nitride crystal of a group 13 metal in the periodic table utilizing a liquid phase growth method, while progressing crystal growth by introducing gas including hydrogen-containing gas into a gas phase having a contact with a liquid phase 102, a treatment is performed in which a solution or a melt (liquid phase) 102 used for crystal growth is brought into contact with the gas phase into which gas having low elemental hydrogen concentration is introduced, and the solution or the melt subjected to the treatment is again utilized for crystal growth as the liquid phase 102 to suppress decline of crystal growth speed, and to thereby progress crystal growth stably for long hours.

Description

  The present invention relates to a method for producing a periodic table group 13 metal nitride crystal using a liquid phase growth method.

  Periodic table group 13 metal nitride semiconductors represented by GaN have a large band gap, and the transition between bands is a direct transition type. It has been put to practical use as a light emitting element on the short wavelength side. These elements are preferably manufactured using a high-quality substrate made of the same material and having a low dislocation density, and a method for producing a periodic table group 13 metal nitride crystal that can be such a substrate is popular. Has been studied. As a typical production method, a vapor phase growth method such as a halide vapor phase growth method (HVPE method) or a metal organic chemical vapor deposition method (MOCVD method) is generally known. From the viewpoint of the above, the liquid phase growth method such as the flux method is also being studied.

In the liquid phase growth method such as the flux method, it is difficult to secure a sufficient nitrogen concentration in the liquid phase because it is difficult to dissolve nitrogen in the liquid phase or the nitrogen compound as a raw material is easily decomposed. When crystal growth is performed in such an environment, there is a tendency that fine crystals are formed or N defects are easily generated in the crystal. Therefore, for example, in a crystal growth method using a gallium compound financial liquid to which an alkali metal is added, a high pressure condition is employed in order to ensure a nitrogen concentration in the liquid phase (see Patent Document 1). However, the crystal growth method that requires high-pressure conditions has problems in terms of production cost and safety.
As a technique for coping with such a problem, for example, a manufacturing method using a composite nitride containing a metal element other than a periodic table group 13 metal element such as Li ₃ GaN ₂ and a periodic table group 13 metal element has been proposed. Crystal growth can be efficiently advanced under low pressure conditions (see Patent Document 2).

JP 2005-306709 A JP 2007-084422 A

Ensure sufficient nitrogen concentration in the liquid phase by using a composite nitride containing a periodic table group 13 metal element such as Li ₃ GaN ₂ and a metal element other than the periodic table group 13 metal element as a raw material. While this is possible, new challenges are also highlighted. For example, it will be described as an example the case of growing a GaN using Li ₃ GaN ₂ as a raw material, crystal growth proceeds by the equilibrium reaction represented by the following reaction formula [1], the Li ₃ N with crystal growth It will be produced as a by-product.
Since Li ₃ N is easily dissolved in the liquid phase, the Li ₃ N concentration in the liquid phase increases with the progress of crystal growth. As is clear from the reaction formula [1], the concentration of Li ₃ N As the rate rises, the crystal growth rate gradually decreases, eventually reaching equilibrium and crystal growth stops.
In response to such a problem, the present inventors introduce a hydrogen-containing gas such as hydrogen (H ₂ ) into the gas phase in contact with the liquid phase, and dissolve the hydrogen component in the liquid phase, so that Li ₃ N and the like are dissolved. It has been found that byproducts can be hydrogenated and decomposed (for example, the decomposition reaction of Li ₃ N into lithium amide is considered to proceed by the reaction shown in the following reaction formula [2]), but hydrogen Even when the contained gas was introduced, when the crystal growth took a long time, there was an event that the crystal growth rate decreased.
That is, the present invention suppresses a decrease in crystal growth rate that occurs in the liquid phase growth method of Group 13 metal nitride crystals of the periodic table, and allows periodic crystal group 13 metal nitrides to proceed stably for a long time. It is an object to provide a method for producing a crystal.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have made hydrogen in the gas phase in contact with the liquid phase in the crystal growth process of Group 13 metal nitride crystals of the periodic table using the liquid phase growth method. In contrast to this, while introducing a gas containing a contained gas to promote crystal growth, a process of promoting a reverse reaction of the crystal growth reaction by introducing a gas having a low hydrogen-containing gas concentration into the gas phase is performed. The present inventors have found that the crystal growth can be carried out stably for a long period of time by using the solution or melt subjected to the above as a liquid phase for crystal growth again, and the present invention has been completed.

That is, the present invention is as follows.
<1> A step of producing a solution or melt containing a raw material and a solvent, and epitaxial growth of a Group 13 metal nitride crystal of the periodic table in the liquid phase in the presence of a liquid phase and a gas phase as the solution or melt. And a growth step for producing a periodic table group 13 metal nitride crystal, wherein the growth step introduces a gas so as to satisfy the following formula (1) in the vapor phase: And the reverse reaction promoting step, using the solution or melt used in the forward reaction promoting step in the reverse reaction promoting step, and using the solution or melt used in the reverse reaction promoting step in the forward reaction promoting step. A method for producing a Group 13 metal nitride crystal of the periodic table, characterized in that
C _F > C _R (1)
(In Formula (1), C _F represents the hydrogen element concentration of the gas introduced into the gas phase in the forward reaction promotion step, and C _R represents the hydrogen element concentration of the gas introduced into the gas phase in the reverse reaction promotion step. (However, C _F > 0 and C _R ≧ 0.)
<2> The gas introduced into the gas phase in the forward reaction promotion step includes a hydrogen-containing gas, and the gas introduced into the gas phase in the reverse reaction promotion step includes a nitrogen-containing gas and / or an inert gas. The manufacturing method of the periodic table group 13 nitride crystal as described in <1> which is included.
<3> The periodic table group 13 metal nitride crystal according to <1> or <2>, wherein the solution or melt contains a periodic table group 1 metal element and / or a periodic table group 2 metal element. Manufacturing method. <4> The growth process uses a composite nitride containing a periodic table group 13 metal element and a metal element other than the periodic table group 13 metal element as a raw material. <1> to <3> The manufacturing method of the periodic table group 13 metal nitride crystal in any one.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the periodic table group 13 metal nitride crystal which can advance crystal growth stably for a long time can be provided.

It is a conceptual diagram of the apparatus used for the growth process which concerns on this invention.

Although the manufacturing method of the periodic table group 13 metal nitride crystal of this invention is demonstrated in detail below, unless it is contrary to the meaning of this invention, it is not limited to these content.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

<Method for Producing Periodic Table Group 13 Metal Nitride Crystal>
The production method of the periodic table group 13 metal nitride crystal of the present invention (hereinafter sometimes abbreviated as “production method of the present invention”) is “a step of producing a solution or melt containing a raw material and a solvent”. “Growth step of epitaxially growing group 13 metal nitride crystals of the periodic table in the liquid phase in the presence of a liquid phase and a gas phase that are solutions or melts (hereinafter sometimes abbreviated as“ growth step according to the present invention ”). .) ”, A method for producing a periodic table group 13 metal nitride crystal using a so-called liquid phase growth method. The growth process according to the present invention includes a positive reaction promotion process for promoting crystal growth by introducing a gas containing a hydrogen-containing gas into the gas phase in contact with the liquid phase, and a gas having a lower hydrogen element concentration than the positive reaction promotion process. The liquid phase (solution or melt) used in the reverse reaction promotion step is used, including the reverse reaction promotion step introduced into the gas phase, the liquid phase (solution or melt) used in the forward reaction promotion step used in the reverse reaction promotion step ) Is used in the forward reaction promoting step (the forward reaction promoting step and the backward reaction promoting step satisfy the condition of the following formula (1)).
C _F > C _R (1)
(In Formula (1), C _F is the hydrogen element concentration of the gas introduced into the gas phase in the forward reaction promotion step, and C _R is the hydrogen element concentration of the gas introduced into the gas phase in the reverse reaction promotion step. .)
In the present invention, the term “growth process” means a process that is epitaxially grown at any stage in the process, and is not necessarily limited to a process that is always epitaxially grown in the entire growth process. .
As described above, when GaN is grown using Li ₃ GaN ₂ or the like as a raw material, crystal growth proceeds by an equilibrium reaction represented by the reaction formula [1], and the concentration of Li ₃ N increases with crystal growth. The crystal growth rate will gradually decrease.
Such a phenomenon is not limited to the case of using Li ₃ GaN ₂ as a raw material, but a periodic table group 1 metal nitride (such as Li ₃ N) that melts back (remelts) a periodic table group 13 metal nitride crystal (
(Or periodic table Group 2 metal nitride) as a by-product is widely applied. Therefore, in order to advance the crystal growth stably for a long time, the concentration increase of these by-products is suppressed, that is, the positive reaction (Li ₃ GaN ₂ → GaN + Li ₃ N) in the reaction formula [1].
A means to promote this is needed. However, the presence of these by-products suppresses the rapid growth of the Group 13 metal nitride crystals of the periodic table, and also plays a role of suppressing the production of miscellaneous crystals and increasing the crystallinity. A technique capable of not only reducing the concentration but also precisely adjusting to an appropriate concentration is necessary to obtain a high-quality periodic table Group 13 metal nitride crystal.
In response to such a problem, the present inventors introduce a hydrogen-containing gas such as hydrogen (H ₂ ) into the gas phase in contact with the liquid phase, and dissolve the hydrogen component in the liquid phase, so that Li ₃ N and the like are dissolved. and by-products found that can be decomposed by hydrogenation (e.g., as a decomposition product of Li ₃ N with hydrogen component, lithium hydride, lithium imide, or .Li ₃ N lithium amides The decomposition reaction into lithium amide is considered to proceed by the reaction shown in the following reaction formula [2], and this reaction is also an equilibrium reaction). This operation is extremely effective (simple and precise control) as an operation for promoting the positive reaction (Li ₃ GaN ₂ → GaN + Li ₃ N, Li ₃ N + 3H ₂ + N ₂ → 3LiNH ₂ ) in the reaction formulas [1] and [2]. Is possible).
By introducing a hydrogen-containing gas, the positive reaction (Li
₃ GaN ₂ → GaN + Li ₃ N, Li ₃ N + 3H ₂ + N ₂ → 3LiNH ₂ ) can be promoted, but if the crystal growth still takes a long time, the crystal growth rate will decrease. The inventors have made clear. This is considered to be because the decomposition reaction of dissolved Li ₃ GaN ₂ (that is, the precipitation reaction of GaN) eventually slows due to an increase in the concentration of decomposition products such as Li ₃ N such as lithium imide and lithium amide.
Accordingly, the present inventors introduce a gas containing a hydrogen-containing gas into the gas phase in contact with the liquid phase to promote crystal growth (accelerate the positive reaction), while the solution or melt (liquid phase) used for crystal growth. Is brought into contact with a gas phase in which a gas having a low hydrogen element concentration is introduced to promote the reverse reaction (Li ₃ GaN ₂ ← GaN + Li ₃ N, Li ₃ N + 3H ₂ + N ₂ ← 3LiNH ₂ ) in the reaction formulas [1] and [2]. By doing so, it was found that the solution or melt (liquid phase) can be regenerated to a composition suitable for crystal growth. By using the solution or melt (liquid phase) subjected to such treatment again for crystal growth, a good crystal growth rate can be ensured for the entire crystal growth step. As is clear from the reaction formula [1], when the reverse reaction in the reaction formulas [1] and [2] is promoted, the produced GaN is melt-backed (re-dissolved). Since a large amount of crystal mass (mostly miscellaneous crystals) other than the target crystal (for example, a crystal formed on a seed crystal (seed)) is precipitated, these crystal masses are used as a GaN source. be able to. This can be said to be a preferable method from the viewpoint of the utilization efficiency of the raw material because a crystal lump other than the target crystal is reused as the raw material.
Further, “in the presence of a liquid phase that is a solution or a melt and a gas phase” means that not only a liquid phase in which crystal growth proceeds but also a gas phase in contact with the liquid phase exists.

The growth process according to the present invention is characterized in that it includes a forward reaction promotion process and a reverse reaction promotion process. Hereinafter, the forward reaction promotion process and the reverse reaction promotion process will be described in detail.
The positive reaction promoting step is a step of setting conditions for the purpose of promoting the positive reaction (Li ₃ GaN ₂ → GaN + Li ₃ N, Li ₃ N + 3H ₂ + N ₂ → 3LiNH ₂ ) in the reaction formulas [1] and [2]. Specifically, this is a step of epitaxially growing a group 13 metal nitride crystal of the periodic table while introducing a gas containing a hydrogen-containing gas into the gas phase in contact with the liquid phase (hydrogen element concentration C _F ). On the other hand, the reverse reaction promotion step is the reverse reaction (Li ₃ Ga in the reaction formulas [1] and [2].
N ₂ ← GaN + Li ₃ N, Li ₃ N + 3H ₂ + N ₂ ← 3 LiNH ₂ ) is a process for setting conditions, and more specifically, the hydrogen element concentration (hydrogen element concentration C than the positive reaction promoting process). _This is a process for introducing a gas having a low _R ) into the gas phase in contact with the liquid phase.
In addition, “the growth process includes (omitted) the forward reaction promotion process and the reverse reaction promotion process” means that the forward reaction promotion process and the reverse reaction promotion are performed in the crystal growth process of epitaxially growing the group 13 metal nitride crystal of the periodic table. This means that each step may be performed a plurality of times. Furthermore, the forward reaction promoting step and the backward reaction promoting step do not have to be performed independently over time, and the forward reaction promoting step and the backward reaction promoting step may be performed in parallel.
Furthermore, "Use the solution or melt used in the forward reaction promotion step for the reverse reaction promotion step and use the solution or melt used for the reverse reaction promotion step in the forward reaction promotion step" specifically Examples such as the following (a) and (b) are included.
(A) Growth process in which forward reaction promotion process and reverse reaction promotion process are performed alternately (b) Growth process in which forward reaction promotion process and reverse reaction promotion process are simultaneously performed

As an aspect of (a), for example, after introducing a gas containing a hydrogen-containing gas into the gas phase, the crystal growth is advanced for a certain time in the liquid phase, and then introduced into the gas phase so that the hydrogen element concentration of the gas becomes low The normal reaction promotion process and the reverse reaction promotion process, such as adjusting and / or switching the gas that has been maintained for a certain period of time and adjusting and / or switching the gas so that the hydrogen element concentration is increased again to resume crystal growth. Are implemented alternately. Such an embodiment can be carried out only by adjusting and / or switching the gas to be introduced in one reaction system, and is an excellent method in terms of operability. In addition, although each implementation time of the normal reaction promotion step and the reverse reaction promotion step in such an embodiment should be appropriately set according to other conditions, the implementation time of the normal reaction promotion step is usually 0.1 hour. Above, preferably 1 hour or more, more preferably 3 hours or more, usually 100 hours or less, preferably 30 hours or less, more preferably 10 hours or less. Moreover, the implementation time of the reverse reaction promoting step is usually 1 hour or longer, preferably 10 hours or longer, more preferably 20 hours or longer, and usually 1000 hours or shorter, preferably 100 hours or shorter, more preferably 50 hours or shorter. Within the above range, it is possible to maintain a balance between the execution times of the forward reaction promoting step and the backward reaction promoting step, and it is possible to ensure a good crystallization speed as the whole growth step. Note that the growth rate in the initial stage of the positive reaction promotion step can be sufficiently high, but the growth rate tends to slow with time, and if the execution time of the positive reaction promotion step is too long, the growth efficiency is poor. Become. On the other hand, unless sufficient time is taken for the reverse reaction promotion step, the reverse reaction cannot be sufficiently advanced, and a desired growth rate cannot be obtained in the subsequent normal reaction promotion step. From such a viewpoint, the execution time of the reverse reaction promotion step is preferably longer than the execution time of the forward reaction promotion step, more preferably 2 times or more, further preferably 3 times or more, and more preferably 5 times or more. In particular, it is preferably 100 times or less, more preferably 50 times or less, further preferably 20 times or less, and particularly preferably 10 times or less.
Further, in such an aspect, when the process proceeds from the normal reaction promoting step to the reverse reaction promoting step, the target crystal, for example, the seed crystal formed by the crystal layer is lifted from the liquid phase, etc. It is preferable to take measures to prevent back (re-dissolution). Such a treatment can prevent the crystal growth from retreating and can reuse the unintended crystal lump precipitated in the liquid phase as a raw material, which is preferable from the viewpoint of the utilization efficiency of the raw material.

  As an aspect of (b), for example, a part of a solution or a melt (liquid phase) in which crystal growth has proceeded for a certain period of time is transferred to another container or chamber in which at least the gas phase is separated, where the concentration of hydrogen element is low Separate reaction system from the normal reaction promotion step and the reverse reaction promotion step, such as contacting the gas phase introducing gas for a certain period of time, returning to the vessel or chamber where crystal growth proceeds again and reusing it for crystal growth. In this case, it is possible to carry out in parallel. Such an embodiment is a positive reaction, that is, it is not necessary to stop the crystal growth, and is an excellent method from the viewpoint of the efficiency of crystal growth.

The positive reaction promoting step according to the present invention is characterized in that a gas having a hydrogen element concentration C _F (C _F > 0) is introduced into the gas phase in contact with the liquid phase, that is, a gas containing a hydrogen-containing gas is introduced. Although it is a process, the kind of hydrogen-containing gas introduced in this process is not particularly limited. Specific examples include hydrogen gas (H ₂ ) and ammonia gas (NH ₃ ). Among these, hydrogen gas (H ₂ ) is particularly preferable. Hydrogen gas (H ₂ ) has the advantage that it is easy to control the gas composition without being decomposed even at high temperatures. Further, the hydrogen-containing gas introduced in the positive reaction promoting step is preferably introduced into the gas phase together with a gas other than the hydrogen-containing gas, and more preferably introduced together with the nitrogen-containing gas and / or the inert gas. By introducing with a gas other than the hydrogen-containing gas, the concentration of hydrogen element (C _F ) in the introduced gas can be controlled. As gases other than hydrogen-containing gas, nitrogen gas (N ₂ ), argon gas (Ar
In particular, nitrogen gas (N ₂ ) is preferable. Nitrogen gas (N ₂ ) has an advantage that nitrogen defects in the crystal can be reduced.
On the other hand, the reverse reaction promoting step according to the present invention is a step characterized by introducing a gas having a lower hydrogen element concentration (C _R ) than the gas introduced in the forward reaction promoting step. Others are not particularly limited as long as they are lower than the reaction promoting step. Examples of the gas to be introduced include the aforementioned nitrogen-containing gas, inert gas, and mixed gas thereof, and mixed gas of these and hydrogen-containing gas. Among these, a nitrogen-containing gas, an inert gas, and a mixed gas thereof are preferable.
Furthermore, the flow rate of the gas introduced in the forward reaction promotion step and the reverse reaction promotion step should be appropriately set according to the type of gas to be introduced and other conditions, but in an amount converted to normal temperature and normal pressure, Usually 0.1 cm ³ / min or more, preferably 1 cm ³ / min or more, more preferably 10 cm ³ / min or more, usually 10000 cm ³ / min or less, preferably 5000 cm ³ / min or less, more preferably 1000 cm ³ / min It is as follows. Within the above range, a good initial crystal growth rate can be secured.

In the forward reaction promotion step and the reverse reaction promotion step according to the present invention, the hydrogen element concentration of the gas introduced into the gas phase satisfies the condition of the following formula (1), that is, the hydrogen element concentration in the reverse reaction promotion step is What is necessary is just to be lower than the hydrogen element concentration in the positive reaction promoting step, and the specific hydrogen element concentration is not particularly limited.
C _F > C _R (1)
(In Formula (1), C _F represents the hydrogen element concentration of the gas introduced into the gas phase in the forward reaction promotion step, and C _R represents the hydrogen element concentration of the gas introduced into the gas phase in the reverse reaction promotion step. (However, C _F > 0 and C _R ≧ 0.)
Further, as long as the hydrogen element concentration in the forward reaction promoting step and the hydrogen element concentration in the reverse reaction promoting step can be substantially compared, other quantitative values may be substituted. For example, the concentration of the hydrogen-containing gas in the gas to be introduced is preferable because it is easy to grasp. Specifically, when a mixed gas of ammonia gas and nitrogen gas is used as the gas to be introduced, the volume% concentration of the ammonia gas in the mixed gas becomes “the concentration of the hydrogen-containing gas in the gas to be introduced”. The volume% concentration of ammonia gas therein can be used as the “hydrogen element concentration of the introduced gas”.
The specific value of the concentration of the hydrogen-containing gas in the introduced gas in the positive reaction promoting step is usually 0.001 vol% or more, preferably 0.01 vol% or more, more preferably 0.1 vol% or more, and usually 99. It is 9 vol% or less, preferably 99 vol% or less, more preferably 90 vol% or less. On the other hand, the specific value of the concentration of the hydrogen-containing gas in the introduced gas in the reverse reaction promoting step is usually 0 vol% or more, usually 5 vol% or less, preferably 1 vol% or less, more preferably 0.1 vol% or less. is there. Within the above range, a good initial crystal growth rate can be ensured for the entire growth process.

  Hereinafter, in describing the other conditions of the growth process according to the present invention, reference is made to the conceptual diagram (FIG. 1) of the apparatus used for the growth process, but it is limited to these contents unless it is contrary to the spirit of the present invention. It is not something.

  The apparatus of FIG. 1 has a structure including a gas introduction pipe 110 and a gas exhaust pipe 106, a reaction tube 105 in which a reaction vessel 104 is installed, and an electric furnace 111 for heating the reaction tube. is there. The seed crystal 100 can be placed in the solution or melt 102 by introducing the raw material 102 and the solution or melt 102 used as a liquid phase into the reaction vessel 104 and using a seed (seed crystal) holder 108. .

[material]
The raw material used in the production method of the present invention can be appropriately set according to the target periodic table group 13 metal nitride crystal, for example, as described above Li ₃ GaN ₂ composite metal nitride, A composite metal nitride containing a metal element other than the Group 13 metal element of the periodic table and the Group 13 metal element of the periodic table is preferable. Although the specific kind of metal elements other than a periodic table group 13 metal element is not specifically limited, A periodic table group 1 metal element, a periodic table group 2 metal element, etc. are mentioned. That is, as a composite nitride containing a periodic table group 13 metal element and a metal element other than the periodic table group 13 metal element, Li ₃ GaN ₂ , Ca ₃ Ga ₂ N ₄ , Ba ₃ Ga ₂ N ₄ , Examples thereof include composite nitrides containing a periodic table group 13 metal element and a periodic table group 1 metal element and / or a periodic table group 2 metal element such as Mg ₃ GaN ₃ . In addition, the composite nitride containing a periodic table group 13 metal element and a periodic table group 1 metal element and / or a periodic table group 2 metal element is, for example, a periodic table group 13 metal nitride powder and a periodic table. Method of heating after mixing Group 1 metal and / or Group 2 metal nitride powder (for example, Li ₃ N, Ca ₃ N ₂ ) and heating (solid phase reaction); Group 13 metal element of the periodic table And an alloy containing a periodic table Group 1 metal element and / or a periodic table Group 2 metal element, and heating in a nitrogen atmosphere; For example, Li ₃ GaN ₂ can be manufactured by heat-treating a Ga—Li alloy at 600 to 800 ° C. in a nitrogen atmosphere.

  As a raw material other than the composite nitride containing the periodic table group 13 metal element and the periodic table group 1 metal element and / or the periodic table group 2 metal element, the periodic table group 13 metal nitride itself should be used. Can do. In addition, for example, a target made of an alloy of a periodic table group 13 metal element and a periodic table group 1 metal element and / or a periodic table group 2 metal element is used to react with nitrogen plasma by a reactive sputtering method. A mixed nitride film may also be mentioned. Such a mixed nitride film is suitable when a nitride that is difficult to synthesize chemically is used.

  When the raw material is a solid under the conditions in the growth process, such a solid raw material need not be completely dissolved in the solvent. Even when a part is not dissolved but is present in the reaction vessel, the amount consumed by crystal growth is supplied to the solvent as needed. In addition, the amount of the raw material to be installed in the solvent is not particularly limited and can be appropriately set according to the purpose. %, Usually 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less. Within the above range, the efficiency for continuous production can be increased, and a space in the reaction vessel can be secured.

[solvent]
In the growth step according to the present invention, the solvent used in the liquid phase (solution or melt) is not particularly limited, but a solvent containing a metal salt as a main component is preferable. The content of the metal salt is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass or more. In particular, a molten salt obtained by melting a metal salt is preferably used as a solvent.

The type of the metal salt is not particularly limited as long as it does not inhibit crystal growth, but it is not limited to those of Group 1 metals of the periodic table such as Li, Na and K and / or Group 2 metals of the periodic table such as Mg, Ca and Sr. Listed are halides, carbonates, nitrates, sulfurides and the like. _{Specifically, LiCl, KCl, NaCl, CaCl} 2, BaCl 2, CsCl, LiBr, KBr, CsBr, LiF, KF, NaF, LiI, NaI, metal halides such as CaI _2, BaI ₂ preferably, LiCl, KCl, NaCl, CsCl, CaCl ₂ and BaCl ₂ are more preferable. The type of metal salt is not limited to one type, and a plurality of types of metal salts may be used in appropriate combination. Among these, it is more preferable to use lithium halide and a metal salt other than this together. The content of lithium halide is preferably 30% or more, more preferably 80% or more, based on the total amount of the metal salt.

Moreover, in order to increase the solubility of the composite nitride containing the periodic table group 13 metal element and the periodic table group 1 metal element and / or the periodic table group 2 metal element, for example, Li ₃ N, Ca ₃ N ₂ , M
It is preferable that a nitride of a periodic table group 1 metal element or a periodic table group 2 metal element such as g ₃ N ₂ , Sr ₃ N ₂ , or Ba ₃ N ₂ is contained in the solvent.

  Metal salts generally have a high hygroscopic property and therefore contain a large amount of moisture. Therefore, it is preferable to purify the solvent to be used in advance. Although the purification method is not particularly limited, for example, a method in which a reactive gas is blown into a solvent using an apparatus described in JP-A-2007-084422 can be mentioned. For example, when a metal salt that is solid at room temperature is used as a solvent, it is melted by heating to hydrogen chloride, hydrogen iodide, hydrogen bromide, ammonium chloride, ammonium bromide, ammonium iodide, chlorine, bromine, or iodine. Impurities such as moisture can be removed by bubbling with a reactive gas such as. It is particularly preferable to use hydrogen chloride for the molten salt of chloride.

[Seed crystal]
In the growth step according to the present invention, it is preferable to install a seed crystal in the liquid phase in order to obtain a crystal of industrially sufficient size. The seed crystal is the same type as the target periodic table group 13 metal nitride crystal such as GaN, InGaN, AlGaN, etc., metal oxides such as sapphire, ZnO, BeO, silicon-containing materials such as SiC, Si, Alternatively, GaAs or the like can be used. Considering the consistency with the periodic table group 13 metal nitride crystal grown in the present invention, the periodic table group 13 metal nitride crystal is most preferable. The shape of the seed crystal is not particularly limited, and may be a flat plate shape or a rod shape. In the case of using a rod-shaped seed crystal, it is possible to produce a bulk crystal by first growing in the seed crystal portion and then performing crystal growth in the vertical direction while also performing crystal growth in the horizontal direction. In order to efficiently grow the Group 13 metal element of the periodic table on the seed crystal, it is preferable that no miscellaneous crystal is grown or attached around the seed crystal. The miscellaneous crystal is a crystal having a small particle diameter that grows other than on the seed crystal. When the miscellaneous crystal exists in the vicinity of the seed crystal, the growth of the periodic table group 13 metal nitride component in the liquid phase and the miscellaneous crystal. Therefore, the growth rate of the group 13 metal nitride crystal of the periodic table on the seed crystal cannot be sufficiently obtained.

[Reaction vessel]
The form of the reaction vessel used for maintaining the liquid phase is not particularly limited, and can be appropriately set depending on the purpose. The material of the reaction vessel is not particularly limited as long as it does not hinder the reaction in the production method of the present invention, but the main component is a thermally and chemically stable metal, oxide, nitride, carbide or the like. It is preferable. Specifically, a metal containing a Group 4 metal element (Ti, Zr, Hf) of the periodic table is preferable, and a metal containing Ti is more preferable. The material of the reaction vessel is preferably a material rich in workability and mechanical durability, more preferably 90% by mass or more of a metal that is the Group 4 metal element, and 99% by mass or more. More preferably, a metal that is a Group 4 metal element is used. Furthermore, the surfaces of these reaction vessels are preferably made of nitrides of Group 4 metal elements of the periodic table, and it is preferable to form nitrides beforehand by a nitriding method as described later.

[Method of nitriding a member]
In addition to the reaction vessel described above, members used in the growth process, such as a stirring blade, a seed (seed crystal) holding rod, a seed (seed crystal) holding table, a baffle, a gas introduction pipe, a valve, etc., are subjected to nitriding treatment described below. It is preferable to form a strong and stable nitride on the surface in contact with the solution or melt. In order to maintain workability and mechanical durability, the nitride may be formed in the form of a nitride film.
The nitriding treatment method is not particularly limited as long as the nitride formed on the surface is stable. For example, the member of the reaction vessel is heated and held in a nitrogen atmosphere at 700 ° C. or higher, so that stable nitriding is performed on the surface of the member. A film can be formed.
Furthermore, the surface of the member can be nitrided using an alkali metal nitride or alkaline earth metal nitride as a nitriding agent at a high temperature, preferably an alkali metal halide or an alkaline earth metal halide. A stable nitride film can be formed by holding it in a mixed melt with the alkali metal nitride or alkaline earth metal nitride. In addition, the nitriding treatment can be easily performed by holding the member under the same conditions as the actual crystal growth conditions.

[Temperature, pressure and other conditions]
The temperature condition in the growth step is usually 200 ° C. or higher, preferably 400 ° C. or higher, more preferably 600 ° C. or higher, and usually 1000 ° C. or lower, preferably 850 ° C. or lower, more preferably 800 ° C. or lower.
Further, the pressure condition of the growth step is usually 10 MPa or less, preferably 3 MPa or less, more preferably 0.3 MP, because the production apparatus becomes simple and can be produced industrially advantageously.
a or less, more preferably 0.11 MPa or less, and usually 0.01 MPa or more, preferably 0.09 MPa or more.

    The growth rate of crystal growth can be adjusted by the temperature, pressure, etc., and is not particularly limited, but is usually in the range of 0.1 μm / h to 1000 μm / h, and is 1 μm / h or more. Preferably, it is 10 μm / h or more, more preferably 100 μm / h or more. In addition, the growth rate in this invention can be calculated | required by remove | dividing the thickness computed by converting the increase mass of the grown crystal | crystallization by the time which implemented the positive reaction promotion process.

  In addition, it is desirable to stir the liquid phase in order to uniformly distribute the raw material in the liquid phase. The stirring method is not particularly limited, and examples thereof include a method of rotating and stirring the seed crystal, a method of rotating and stirring the seed crystal, a method of bubbling the liquid phase with gas, and a method of stirring with a liquid feed pump.

Other conditions for the growth process according to the present invention are not particularly limited, and a technique used in a liquid phase growth method such as a flux method may be appropriately adopted and applied to the growth process of the present invention. Specifically, the temperature difference (Gradient Transport) method, the slow cooling (Slow Cooling) method, and the temperature cycle (Temperature) mainly used in the flux method.
Cycling method, crucible accelerated rotation (Accelerated Crucible)
Rotation method, top-seed solution growth method, solvent transfer method and solvent-moving floating zone method (Traveling-Solvent Floating-Zone) method and evaporation method, and any combination of these methods Method.

  The production method of the present invention includes a “process for producing a solution or melt containing a raw material and a solvent”, and this is a liquid phase solution or melt used for epitaxial growth as a pre-stage of the above-described growth process. Means the step of preparing For example, an operation of dissolving the raw material in a solvent or an operation of adjusting the melt by heating or the like when the compound serving as the solvent is solid at room temperature is also included in the step of preparing the solution or the melt. However, the solution or melt containing the raw material and the solvent does not need to be completely dissolved in the solvent, and may be a heterogeneous system in which the solid raw material is dispersed or present in the solution as a solid. Moreover, this process can be performed in the apparatus of FIG. 1 used for the growth process. For example, a solution or melt 102 can be prepared by placing a raw material and a compound serving as a solvent in the reaction vessel 104 and heating the reaction tube 105 with an electric furnace 111.

  In addition to the steps described above, the production method of the present invention may include a slicing step for slicing the obtained crystal to a desired size, a surface polishing step for polishing the surface, and the like. Specific examples of the slicing step include wire slicing and inner peripheral edge slicing, and the surface polishing step includes, for example, an operation of polishing the surface using abrasive grains such as diamond abrasive grains, CMP (chemical mechanical polishing). An operation of etching a damaged layer by RIE after mechanical polishing can be mentioned.

  The type of periodic table group 13 metal nitride crystal produced by the production method of the present invention is not particularly limited as long as it is a nitride crystal containing a periodic table group 13 metal element, but for example, GaN, AlN, InN, etc. In addition to nitrides composed of one type of periodic table group 13 metal element, mixed crystals composed of two or more types of periodic table group 13 metal elements such as GaInN and AlGaN can be cited.

The periodic table group 13 metal nitride crystal produced by the production method of the present invention can be used for various applications. In particular, as a substrate for manufacturing a light emitting element on a relatively short wavelength side such as an ultraviolet to blue light emitting diode or a semiconductor laser, and a light emitting element on a relatively long wavelength side of green to red, it is further used for a semiconductor device such as an electronic device. It is also useful as a substrate.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Example 1>
(1) 1.44 g of solid Li ₃ GaN ₂ having an outer diameter of 34 mm, an inner diameter of 30 mm, and a height of 200 mm
Then, 14.4 g of LiCl as a solvent was pulverized with a mortar made of tungsten carbide and then placed in the reaction vessel. Solid Li ₃ GaN ₂ having a particle size of 710 μm or more and 2 mm or less was selected and used using a sieve. Next, a tungsten seed holding rod fitted with a reaction vessel and a GaN seed was set in a quartz reaction tube, and the gas inlet and the gas exhaust port of the reaction tube were closed. All these operations were performed in an Ar box.
(2) The reaction tube was taken out from the Ar box and set in an electric furnace. After connecting the gas introduction pipe to the reaction pipe and reducing the pressure inside the introduction pipe, the gas introduction port of the reaction pipe is further opened to reduce the pressure inside the reaction pipe, and then the pressure is restored to atmospheric pressure with a hydrogen nitrogen mixed gas (hydrogen 10 vol%). The inside of the reaction tube was a hydrogen / nitrogen mixed atmosphere. Then, the gas exhaust port of the reaction tube was opened, and a hydrogen nitrogen mixed gas (hydrogen 10 vol%) was allowed to flow at a flow meter set value of 100 cm ³ / min (converted value for 20 ° C., 1 atm).
(3) Heating of the electric furnace was started, the temperature was raised in one hour until the inside of the reaction vessel reached room temperature to 750 ° C., and a molten salt obtained by melting LiCl as a salt was used as a solvent.
(4) After holding at 750 ° C. for 2 hours, the seed attached to the tip of the seed holding rod was put into the solution (melt) in the reaction vessel to start crystal growth. A GaN substrate (thickness: 315 μm, size: 5 × 10 mm plate shape) having a (20-21) plane as a main surface was used as a seed.
(5) After growing at 750 ° C. for 6 hours, the seed was pulled up from the solution, and then the flow gas was only nitrogen, and the flow meter was set at 100 cm ³ / min for 14 hours.
(6) Hydrogen / nitrogen mixed gas (hydrogen 10 vol%) with a flow meter set value of 100 cm ³ / min (2
The mixture was circulated at 0 ° C. and 1 atm) for 2 hours, and then the seed was reintroduced into the solution (melt) in the reaction vessel, and crystal growth was performed for 7 hours.
(7) After raising the seed from the solution, the flow gas was only nitrogen and the flowmeter was set at 100 cm ³ / min for 17 hours.
(8) A hydrogen-nitrogen mixed gas (hydrogen 10 vol%) is set to a flow meter set value of 100 cm ³ / min (2
Then, the seed was put into the solution (melt) in the reaction vessel and crystal growth was performed for 8.5 hours.
(9) After cooling, the seed was taken out from the reaction tube, and the salt adhering to the seed was dissolved in water. A GaN growth layer made of a GaN crystal was formed on the main surface of the seed. The seed growth time was 21.5 hours, and the growth rate of the obtained crystal layer was 25.8 μm / day.

<Example 2>
(1) Solid Li ₃ GaN ₂ 1.53 g, outer diameter 34 mm, inner diameter 30 mm, height 200 mm
Then, 15.6 g of LiCl as a solvent was pulverized with a mortar made of tungsten carbide and then put into the reaction vessel. Solid Li ₃ GaN ₂ having a particle size of 710 μm or more and 2 mm or less was selected and used using a sieve. Next, a tungsten seed holding rod fitted with a reaction vessel and a GaN seed was set in a quartz reaction tube, and the gas inlet and the gas exhaust port of the reaction tube were closed. All these operations were performed in an Ar box.
(2) The reaction tube was taken out from the Ar box and set in an electric furnace. After connecting the gas introduction pipe to the reaction pipe and reducing the pressure inside the introduction pipe, the gas introduction port of the reaction pipe is further opened to reduce the pressure inside the reaction pipe, and then the pressure is restored to atmospheric pressure with a hydrogen nitrogen mixed gas (hydrogen 10 vol%). The inside of the reaction tube was a hydrogen / nitrogen mixed atmosphere. Then, the gas exhaust port of the reaction tube was opened, and a hydrogen nitrogen mixed gas (hydrogen 10 vol%) was allowed to flow at a flow meter set value of 100 cm ³ / min (converted value for 20 ° C., 1 atm).
(3) Heating of the electric furnace was started, the temperature was raised in one hour until the inside of the reaction vessel reached room temperature to 750 ° C., and a molten salt obtained by melting LiCl as a salt was used as a solvent.
(4) After holding at 750 ° C. for 1 hour, the seed attached to the tip of the seed holding rod was put into the solution (melt) in the reaction vessel to start crystal growth. A GaN substrate (thickness: 315 μm, size: 5 × 10 mm plate shape) having a (20-21) plane as a main surface was used as a seed.
(5) After growing at 750 ° C. for 7 hours, the seed was pulled out of the solution, and then the flow gas was only nitrogen, and the flowmeter was set at 100 cm ³ / min for 21 hours.
(6) Hydrogen / nitrogen mixed gas (hydrogen 10 vol%) with a flow meter set value of 100 cm ³ / min (2
The mixture was circulated at 0 ° C. and converted to 1 atm and held for 1 hour, and then the seed was reintroduced into the solution (melt) in the reaction vessel, and crystal growth was performed for 7 hours.
(7) After raising the seed from the solution, the flow gas was only nitrogen and the flowmeter was set at 100 cm ³ / min for 21 hours.
(8) A hydrogen-nitrogen mixed gas (hydrogen 10 vol%) is set to a flow meter set value of 100 cm ³ / min (2
Then, the seed was introduced into the solution (melt) in the reaction vessel and crystal growth was performed for 7 hours.
(9) After cooling, the seed was taken out from the reaction tube, and the salt adhering to the seed was dissolved in water. A GaN growth layer made of a GaN crystal was formed on the main surface of the seed. The seed growth time was 21 hours, and the growth rate of the obtained crystal layer was 35.6 μm / day.

<Comparative Example 1>
1) Put 1.44 g of solid Li ₃ GaN _{2 in} a reaction vessel made of titanium (Ti) having an outer diameter of 34 mm, an inner diameter of 30 mm, and a height of 200 mm, and then pulverize LiCl 14.4 g as a solvent in a tungsten carbide mortar. After that, it was put in a reaction vessel. Solid Li ₃ GaN ₂ having a particle size of 710 μm or more and 2 mm or less was selected and used using a sieve. Next, a tungsten seed holding rod fitted with a reaction vessel and a GaN seed was set in a quartz reaction tube, and the gas inlet and the gas exhaust port of the reaction tube were closed. All these operations were performed in an Ar box.
(2) The reaction tube was taken out from the Ar box and set in an electric furnace. After connecting the gas introduction pipe to the reaction pipe and reducing the pressure inside the introduction pipe, the gas introduction port of the reaction pipe is further opened to reduce the pressure inside the reaction pipe, and then the pressure is restored to atmospheric pressure with a hydrogen nitrogen mixed gas (hydrogen 10 vol%). The inside of the reaction tube was a hydrogen / nitrogen mixed atmosphere. Then, the gas exhaust port of the reaction tube was opened, and a hydrogen nitrogen mixed gas (hydrogen 10 vol%) was allowed to flow at a flow meter set value of 100 cm ³ / min (converted value for 20 ° C., 1 atm).
(3) Heating of the electric furnace was started, the temperature was raised in one hour until the inside of the reaction vessel reached room temperature to 750 ° C., and a molten salt obtained by melting LiCl as a salt was used as a solvent.
(4) After holding at 750 ° C. for 2 hours, the seed attached to the tip of the seed holding rod was put into the solution (melt) in the reaction vessel, and crystal growth was carried out for 20 hours. A GaN substrate (thickness: 315 μm, size: 5 × 10 mm plate shape) having a (20-21) plane as a main surface was used as a seed.
(5) After cooling, the seed was taken out from the reaction tube, and the salt adhering to the seed was dissolved in water. A GaN growth layer made of a GaN crystal was formed on the main surface of the seed. The growth rate of the obtained crystal layer was 18.8 to 22.4 μm / day.

<Comparative example 2>
1) Put 1.44 g of solid Li ₃ GaN _{2 in} a reaction vessel made of titanium (Ti) having an outer diameter of 34 mm, an inner diameter of 30 mm, and a height of 200 mm, and then pulverize LiCl 14.4 g as a solvent in a tungsten carbide mortar. After that, it was put in a reaction vessel. Solid Li ₃ GaN ₂ having a particle size of 710 μm or more and 2 mm or less was selected and used using a sieve. Next, a tungsten seed holding rod fitted with a reaction vessel and a GaN seed was set in a quartz reaction tube, and the gas inlet and the gas exhaust port of the reaction tube were closed. All these operations were performed in an Ar box.
(2) The reaction tube was taken out from the Ar box and set in an electric furnace. After connecting the gas introduction pipe to the reaction pipe and reducing the pressure inside the introduction pipe, the gas introduction port of the reaction pipe is further opened to reduce the pressure inside the reaction pipe, and then the pressure is restored to atmospheric pressure with a hydrogen nitrogen mixed gas (hydrogen 10 vol%). The inside of the reaction tube was a hydrogen / nitrogen mixed atmosphere. Then, the gas exhaust port of the reaction tube was opened, and a hydrogen nitrogen mixed gas (hydrogen 10 vol%) was allowed to flow at a flow meter set value of 100 cm ³ / min (converted value for 20 ° C., 1 atm).
(3) Heating of the electric furnace was started, the temperature was raised in one hour until the inside of the reaction vessel reached room temperature to 750 ° C., and a molten salt obtained by melting LiCl as a salt was used as a solvent.
(4) After holding at 750 ° C. for 15 hours, the seed attached to the tip of the seed holding rod was put into the solution (melt) in the reaction vessel, and crystal growth was carried out for 7 hours. A GaN substrate (thickness: 315 μm, size: 5 × 10 mm plate shape) having a (20-21) plane as a main surface was used as a seed. (5) After cooling, the seed was taken out from the reaction tube, and the salt adhering to the seed was dissolved in water. A GaN growth layer made of a GaN crystal was formed on the main surface of the seed. The growth rate of the obtained crystal layer was 13.4 μm / day.

  From the results of Table 1, it is clear that by including not only the normal reaction promoting step but also the reverse reaction promoting step, it is possible to suppress a decrease in the crystal growth rate and to proceed with the crystal growth stably for a long time.

100 seed crystals (GaN)
101 Raw material (Li ₃ GaN ₂ )
102 Liquid phase (solution or melt LiCl)
103 Wire 104 Reaction vessel 105 Reaction tube 106 Gas exhaust tube 107 Control valve 108 Seed (seed crystal) holder 109 Control valve 110 Gas introduction tube 111 Electric furnace

Claims (4)

A step of producing a solution or melt containing a raw material and a solvent, and a growth step of epitaxially growing a group 13 metal nitride crystal of the periodic table in the liquid phase in the presence of a liquid phase and a gas phase as the solution or melt. A method for producing a periodic table group 13 metal nitride crystal comprising:
The growth step includes a forward reaction promoting step and a reverse reaction promoting step of introducing gas so as to satisfy the condition of the following formula (1) in the gas phase:
The solution or melt used in the forward reaction promotion step is used in the reverse reaction promotion step, and the solution or melt used in the reverse reaction promotion step is used in the forward reaction promotion step. A method for producing a Group 13 metal nitride crystal of the periodic table.
C _F > C _R (1)
(In Formula (1), C _F represents the hydrogen element concentration of the gas introduced into the gas phase in the forward reaction promotion step, and C _R represents the hydrogen element concentration of the gas introduced into the gas phase in the reverse reaction promotion step. (However, C _F > 0 and C _R ≧ 0.)   The gas introduced into the gas phase in the forward reaction promoting step includes a hydrogen-containing gas, and the gas introduced into the gas phase in the reverse reaction promoting step includes a nitrogen-containing gas and / or an inert gas. The manufacturing method of the periodic table group 13 nitride crystal of Claim 1.   The manufacturing method of the periodic table group 13 metal nitride crystal | crystallization of Claim 1 or 2 whose said solution or melt contains a periodic table group 1 metal element and / or a periodic table group 2 metal element.   4. The method according to claim 1, wherein the growth step uses, as a raw material, a composite nitride containing a periodic table group 13 metal element and a metal element other than the periodic table group 13 metal element. 5. The manufacturing method of the periodic table group 13 metal nitride crystal of description.