JP4528806B2 - GaN crystal growth method - Google Patents

GaN crystal growth method Download PDF

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JP4528806B2
JP4528806B2 JP2007187081A JP2007187081A JP4528806B2 JP 4528806 B2 JP4528806 B2 JP 4528806B2 JP 2007187081 A JP2007187081 A JP 2007187081A JP 2007187081 A JP2007187081 A JP 2007187081A JP 4528806 B2 JP4528806 B2 JP 4528806B2
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伸介 藤原
浩章 吉田
龍 弘田
康二 上松
晴子 田中
勇介 森
孝友 佐々木
史朗 川村
康夫 北岡
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Sumitomo Electric Industries Ltd
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Description

本発明は、液相法によるGaN結晶の成長方法に関する。 The present invention also relates to the growth how of GaN crystal by a liquid phase method.

III族窒化物結晶は、各種半導体デバイスの基板などに広く用いられている。近年、各種半導体デバイスを効率的に製造するために、大型のIII族窒化物結晶が求められている。   Group III nitride crystals are widely used for substrates of various semiconductor devices. In recent years, in order to efficiently manufacture various semiconductor devices, a large group III nitride crystal has been demanded.

III族窒化物結晶を成長させる方法としては、HVPE(ハイドライド気相成長)法、MOCVD(有機金属化学気相堆積)法などの気相法、高圧溶液法、フラックス法などの液相法などがある。ここで、液相法は、気相法に比べて、その結晶成長において有毒なガスを使用しないため環境保護の面で優れている。   As a method for growing a group III nitride crystal, there are a gas phase method such as HVPE (hydride vapor phase epitaxy) method, MOCVD (metal organic chemical vapor deposition) method, a liquid phase method such as high pressure solution method and flux method. is there. Here, the liquid phase method is superior to the gas phase method in terms of environmental protection because no toxic gas is used in crystal growth.

かかる液相法においてIII族窒化物結晶を成長させる方法として、たとえばM. Bockowski,“Growth and Doping of GaN and AlN Single Crystals under High Nitrogen Pressure”, Cryst. Res. Technol., vol.36, (2001), 8-10, p.771-787(非特許文献1)は高圧溶液法によるGaN結晶の成長方法を開示する。また、H. Yamane, 他3名,“Preparation of GaN Single Crystals Using a Na Flux”, Chem. Mater., Vol.9, No.2, (1997), p.413-416(非特許文献2)はNaフラックス法によるGaN結晶の成長方法を開示する。また、特開2003−206198号公報(特許文献1)はNaフラックス法により板状のIII族窒化物種結晶を用いたGaN結晶の成長方法を開示する。   For example, M. Bockowski, “Growth and Doping of GaN and AlN Single Crystals under High Nitrogen Pressure”, Cryst. Res. Technol., Vol. 36, (2001) , 8-10, p. 771-787 (Non-Patent Document 1) discloses a method for growing a GaN crystal by a high-pressure solution method. H. Yamane and three others, “Preparation of GaN Single Crystals Using a Na Flux”, Chem. Mater., Vol. 9, No. 2, (1997), p. 413-416 (Non-patent Document 2) Discloses a method for growing GaN crystals by the Na flux method. Japanese Patent Laying-Open No. 2003-206198 (Patent Document 1) discloses a GaN crystal growth method using a plate-like group III nitride seed crystal by the Na flux method.

しかし、非特許文献1に開示された成長方法は、結晶成長条件が1500℃で1GPaと高温高圧であるため結晶の製造コストが高くなり、また種結晶を用いていないため大型の結晶を成長させることが困難である。また、非特許文献2に開示された成長方法では、800℃で10MPaと比較的実施しやすい結晶成長条件であるが、種結晶を用いていないため大型の結晶を成長させることが困難である。また、特許文献1に開示された成長方法は、用いられている板状の種結晶の口径が大きくないため、大型の結晶が得られていない。
特開2003−206198号公報 M. Bockowski,“Growth and Doping of GaN and AlN Single Crystals under High Nitrogen Pressure”, Cryst. Res. Technol., vol.36, (2001), 8-10, p.771-787 H. Yamane, 他3名,“Preparation of GaN Single Crystals Using a Na Flux”, Chem. Mater., Vol.9, No.2, (1997), p.413-416
However, the growth method disclosed in Non-Patent Document 1 increases the manufacturing cost of crystals because the crystal growth conditions are 1 GPa and 1 GPa at 1500 ° C., and grows large crystals because seed crystals are not used. Is difficult. The growth method disclosed in Non-Patent Document 2 is a crystal growth condition that is relatively easy to carry out at 800 ° C. and 10 MPa, but it is difficult to grow a large crystal because no seed crystal is used. Moreover, since the diameter of the plate-shaped seed crystal used in the growth method disclosed in Patent Document 1 is not large, large crystals are not obtained.
JP 2003-206198 A M. Bockowski, “Growth and Doping of GaN and AlN Single Crystals under High Nitrogen Pressure”, Cryst. Res. Technol., Vol.36, (2001), 8-10, p.771-787 H. Yamane and 3 others, “Preparation of GaN Single Crystals Using a Na Flux”, Chem. Mater., Vol.9, No.2, (1997), p.413-416

しかし、高圧溶液法、フラックス法などの液相法によるGaN結晶の成長においては、大口径の板状のGaN種結晶基板上に、基板と化学組成が同じGaN結晶をホモエピタキシャル成長させても、基板および基板上に成長させたGaN結晶に割れが発生し、大型のGaN結晶基板を得ることが困難である。 However, high pressure solution method, in the growth of I that GaN crystal in a liquid phase method such as a flux method, a plate-like GaN seed crystal substrate having a large diameter, even when the substrate and chemical composition are the same GaN crystal homoepitaxially grown Cracks occur in the substrate and the GaN crystal grown on the substrate, and it is difficult to obtain a large GaN crystal substrate.

本発明は、液相法において大型の結晶を成長させることができるGaN結晶の成長方法を提供することを目的とする。 An object of this invention is to provide the growth method of the GaN crystal which can grow a large crystal | crystallization in a liquid phase method.

かかる基板およびGaN結晶の割れの原因について詳細に検討した結果、基板およびGaN結晶の割れと基板の反りの曲率半径との間に相関があることを見出した。さらに、検討を進めることにより、液相法による基板上におけるGaN結晶のホモエピタキシャル成長において、基板の所定の結晶面の曲率半径を2m以上、好ましくは5m以上、より好ましくは10m以上とすることにより、基板および基板上に成長させたGaN結晶の割れが抑制され、大型のGaN結晶の成長が可能となることを見出した。 As a result of examining the cause of the crack of the substrate and the GaN crystal in detail, it was found that there is a correlation between the crack of the substrate and the GaN crystal and the curvature radius of the warp of the substrate. Further, by proceeding with the study, in the homoepitaxial growth of the GaN crystal on the substrate by the liquid phase method, the curvature radius of the predetermined crystal plane of the substrate is 2 m or more, preferably 5 m or more, more preferably 10 m or more, It has been found that cracking of the substrate and the GaN crystal grown on the substrate is suppressed, and a large GaN crystal can be grown.

本発明は、液相法によるGaN結晶の成長方法であって、平坦な主面を有し、全体がGaN結晶と同じ化学組成を有するGaN種結晶で形成されている自立の基板であって、主面に最も近い(hkil)面(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上である基板を準備する工程と、基板の主面に、Ga金属とアルカリ金属を含む溶媒に窒素含有ガスを溶解させた溶液を接触させて主面上にGaN結晶を成長させる工程と、を備えるGaN結晶の成長方法である。 The present invention is a method for growing a GaN crystal by a liquid phase method, which is a self-supporting substrate having a flat main surface and formed entirely of a GaN seed crystal having the same chemical composition as the GaN crystal, A substrate having a curvature radius of curvature of 2 m or more on the hkil plane closest to the main surface (where i = − (h + k), h, k, and l are integers of −9 to 9) is prepared. step and the main surface of the substrate, the growth method of a GaN crystal and a step, the growing GaN crystal by contacting a solution of a nitrogen-containing gas in a solvent containing a Ga metal and alkali metal on the main surface of It is.

本発明にかかるGaN結晶の成長方法において、曲率半径を5m以上、さらに10m以上とすることができる。また、基板の主面の面積を1cm2以上とすることができる。また、基板の主面を(0001)面、(10−10)面および(10−11)面からなる群から選ばれる1種類の面とすることができる In the GaN crystal growth method according to the present invention, the radius of curvature can be 5 m or more, and further 10 m or more . Also, the area of the main surface of the substrate may be a 1 cm 2 or more. Further, the main surface of the substrate can be one type of surface selected from the group consisting of (0001) plane, (10-10) plane, and (10-11) plane .

本発明によれば、液相法において大型のGaN結晶を成長させることができる。 According to the present invention, a large GaN crystal can be grown in a liquid phase method.

(実施形態1)
本発明にかかるIII族窒化物結晶の成長方法の一実施形態は、図1〜図3を参照して、液相法によるIII族窒化物結晶10の成長方法であって、平坦な主面1mを有し、少なくとも主面1m側にIII族窒化物結晶10と同じ化学組成を有するIII族窒化物種結晶1aを含み、主面1mに最も近い(hkil)面1n(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上である基板を準備する工程と、基板1の主1m面に、III族金属とアルカリ金属を含む溶媒3に窒素含有ガス5を溶解させた溶液を接触させて、主面1m上にIII族窒化物結晶10を成長させる工程と、を備える。
(Embodiment 1)
One embodiment of a method for growing a group III nitride crystal according to the present invention is a method for growing a group III nitride crystal 10 by a liquid phase method with reference to FIGS. And a group III nitride seed crystal 1a having the same chemical composition as that of the group III nitride crystal 10 at least on the main surface 1m side, and is closest to the main surface 1m (hkil) surface 1n (where i = − ( h + k), and h, k, and l are integers of −9 or more and 9 or less, respectively, and a step of preparing a substrate having a curvature radius of 2 m or more; Contacting a solution containing the nitrogen-containing gas 5 with the solvent 3 containing a metal to grow a group III nitride crystal 10 on the main surface 1 m.

本実施形態のIII族窒化物結晶の成長方法においては、主面1mに最も近い(hkil)面1nの反りの曲率半径が2m以上である基板1の主面1m上にIII族窒化物結晶10をホモエピタキシャル成長させることにより、基板および基板上に成長させたIII族窒化物結晶の割れが抑制され、大型の結晶が得られる。   In the method for growing a group III nitride crystal of the present embodiment, the group III nitride crystal 10 is formed on the main surface 1m of the substrate 1 whose curvature radius of curvature of the surface 1n closest to the main surface 1m (hkil) is 2 m or more. By homoepitaxially growing, cracking of the substrate and the group III nitride crystal grown on the substrate is suppressed, and a large crystal is obtained.

本実施形態のIII族窒化物結晶の成長方法に用いられる成長装置は、たとえば、図1および図2を参照して、外容器29と、外容器29の内部に配置された断熱材27と、断熱材27の内部に配置されたヒータ25と、ヒータ25の内側に配置された内容器21とを備える。この内容器21内には、その中でIII族窒化物結晶10を成長させるための結晶成長容器23が配置されている。ここで、結晶成長容器23の材料は、溶媒3および窒素含有ガス5と反応せず、機械的強度および耐熱性の高いものであれば特に制限はないが、BN(窒化ホウ素)などが好ましい。また、内容器21の材料は、機械的強度および耐熱性の高いものであれば特に制限はないが、ステンレス、耐熱鋼などが好ましい。また、外容器29の材料は、機械的強度および耐熱性の高いものであれば特に制限はないが、ステンレスなどが好ましい。また、断熱材25の材料は、機械的強度、耐熱性および断熱性の高いものであれば特に制限はないが、ステンレス、耐熱鋼などが好ましい。   The growth apparatus used in the method for growing a group III nitride crystal of the present embodiment includes, for example, an outer container 29 and a heat insulating material 27 disposed inside the outer container 29, with reference to FIGS. A heater 25 disposed inside the heat insulating material 27 and an inner container 21 disposed inside the heater 25 are provided. In the inner vessel 21, a crystal growth vessel 23 for growing the group III nitride crystal 10 is disposed. Here, the material of the crystal growth vessel 23 is not particularly limited as long as it does not react with the solvent 3 and the nitrogen-containing gas 5 and has high mechanical strength and heat resistance, but BN (boron nitride) or the like is preferable. The material of the inner container 21 is not particularly limited as long as it has high mechanical strength and heat resistance, but stainless steel, heat resistant steel, and the like are preferable. The material of the outer container 29 is not particularly limited as long as it has high mechanical strength and heat resistance, but stainless steel is preferable. The material of the heat insulating material 25 is not particularly limited as long as it has high mechanical strength, heat resistance, and heat insulating properties, but stainless steel, heat resistant steel, and the like are preferable.

また、本実施形態で用いられる成長装置は、第1の配管41によって内容器21に繋がれている窒素含有ガス供給装置31と、第2の配管43によって外容器29に繋がれている加圧用ガス供給装置33と、第3の配管45によって外容器29に繋がれている真空排気装置35とを備える。ここで、第1の配管41には、窒素含有ガス5の供給流量を調節するためのバルブ41vが設けられ、バルブ41vより窒素含有ガス供給装置31側の部分41bには第1の圧力計41pが設けられている。また、第2の配管43には、加圧用ガス7の供給流量を調節するためのバルブ43vが設けられ、バルブ43vより加圧用ガス供給装置33側の部分43bには第2の圧力計43pが設けられている。また、第3の配管45には、排気流量を調節するためのバルブ45vが設けられている。   The growth apparatus used in the present embodiment is a pressurization device connected to the outer container 29 by the nitrogen-containing gas supply device 31 connected to the inner container 21 by the first pipe 41 and the second pipe 43. A gas supply device 33 and a vacuum exhaust device 35 connected to the outer container 29 by a third pipe 45 are provided. Here, the first pipe 41 is provided with a valve 41v for adjusting the supply flow rate of the nitrogen-containing gas 5, and the first pressure gauge 41p is provided in the portion 41b on the nitrogen-containing gas supply device 31 side from the valve 41v. Is provided. The second pipe 43 is provided with a valve 43v for adjusting the supply flow rate of the pressurizing gas 7, and a second pressure gauge 43p is provided at the portion 43b on the pressurizing gas supply device 33 side from the valve 43v. Is provided. The third pipe 45 is provided with a valve 45v for adjusting the exhaust flow rate.

さらに、第1の配管41のバルブ41vより内容器21側の部分41aと第3の配管45のバルブ45vより外容器29側の部分45aとを繋ぐ第4の配管47が設けられている。この第4の配管47にはバルブ47vが設けられている。なお、図1には、参考のため、第2の配管43のバルブ43vより外容器29側の部分43a、第3の配管45のバルブ45vより真空排気装置35側の部分45bも図示した。   Furthermore, a fourth pipe 47 is provided that connects a portion 41 a closer to the inner container 21 than the valve 41 v of the first pipe 41 and a portion 45 a closer to the outer container 29 than the valve 45 v of the third pipe 45. The fourth pipe 47 is provided with a valve 47v. For reference, FIG. 1 also shows a portion 43a on the outer container 29 side from the valve 43v of the second piping 43 and a portion 45b on the vacuum exhaust device 35 side of the valve 45v of the third piping 45.

本実施形態のIII族窒化物結晶の成長方法は、図1〜図3を参照して、まず、平坦な主面を有し、少なくとも主面側にIII族窒化物結晶と同じ化学組成を有するIII族窒化物種結晶を含み、主面に最も近い(hkil)面(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上である基板を準備する工程(基板の準備工程)を備える。   With reference to FIG. 1 to FIG. 3, the growth method of the group III nitride crystal of this embodiment first has a flat main surface, and at least the main surface side has the same chemical composition as the group III nitride crystal. Curvature radius of curvature of group III nitride seed crystal and closest to main surface (hkil) (where i = − (h + k), and h, k, and l are each an integer of −9 to 9) Includes a step of preparing a substrate having a length of 2 m or more (substrate preparation step).

本実施形態において準備される基板1は、平坦な主面1mを有する。平坦な主面1mは、その主面を研削、研磨およびエッチングなどの平滑化方法から選ばれる少なくとも1つの方法により行なうことができる。主面を平坦化することにより、その主面上にIII族窒化物結晶をエピタキシャル成長させることが容易になる。   The substrate 1 prepared in the present embodiment has a flat main surface 1m. The flat main surface 1m can be formed by at least one method selected from smoothing methods such as grinding, polishing and etching. By planarizing the main surface, it becomes easy to epitaxially grow a group III nitride crystal on the main surface.

また、基板1は、少なくとも主面1m側にIII族窒化物結晶10と同じ化学組成を有するIII族窒化物種結晶1aを含む。かかる基板1は、その主面1m上にIII族窒化物結晶10をホモエピタキシャル成長させることができる。ここで、基板1としては、成長させるIII族窒化物結晶と化学組成が同じIII族窒化物種結晶を主面1m側に有するものであれば特に制限はなく、たとえば、下地基板1b上にIII族窒化物種結晶1aが形成されているテンプレート基板、全体がIII族窒化物種結晶1aで形成されている自立基板などが挙げられる。たとえば、III族窒化物結晶10としてAlxGayIn1-x-yN結晶(0≦x、0≦y、x+y≦1)をホモエピタキシャル成長させる場合には、基板1のIII族窒化物種結晶1aとしてAlxGayIn1-x-yN種結晶(0≦x、0≦y、x+y≦1)を用いる。 Substrate 1 includes group III nitride seed crystal 1a having the same chemical composition as group III nitride crystal 10 at least on the principal surface 1m side. Such a substrate 1 can homoepitaxially grow a group III nitride crystal 10 on its main surface 1 m. Here, the substrate 1 is not particularly limited as long as it has a group III nitride seed crystal having the same chemical composition as that of the group III nitride crystal to be grown on the main surface 1m side. For example, a group III is formed on the base substrate 1b. Examples include a template substrate on which the nitride seed crystal 1a is formed, and a free-standing substrate that is entirely formed of a group III nitride seed crystal 1a. For example, when an Al x Ga y In 1-xy N crystal (0 ≦ x, 0 ≦ y, x + y ≦ 1) is homoepitaxially grown as the group III nitride crystal 10, the group III nitride seed crystal 1a of the substrate 1 is used. An Al x Ga y In 1-xy N seed crystal (0 ≦ x, 0 ≦ y, x + y ≦ 1) is used.

また、基板1は、主面1mに最も近い(hkil)面(i=−(h+k)、かつ、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上である。ここで、(hkil)面とは、六方晶系における面指数である。この面においては、h,k,iおよびlの間には、h、kおよびlは互いに独立で、iはhおよびkに従属してi=−(h+k)の関係がある。また、本実施形態における(hkil)面は、h、kおよびlがそれぞれ−9以上9以下の低指数面である。また、主面1mに最も近い(hkil)面とは、主面1mに最もフィットする(hkil)面、すなわち、主面1mに最も平行に近い(hkil)面を意味する。   The substrate 1 has a curvature radius of curvature of 2 m or more on the (hkil) plane closest to the main surface 1 m (i = − (h + k), and h, k and l are integers of −9 to 9). is there. Here, the (hkil) plane is a plane index in the hexagonal system. In this aspect, between h, k, i, and l, h, k, and l are independent from each other, and i is dependent on h and k, i = − (h + k). The (hkil) plane in the present embodiment is a low index plane in which h, k, and l are -9 or more and 9 or less, respectively. Further, the (hkil) surface closest to the main surface 1m means a (hkil) surface that most closely fits the main surface 1m, that is, a surface that is closest to the main surface 1m (hkil).

本実施形態において、基板1の(hkil)面の反りの曲率半径の算出は、特に制限はないが、たとえば基板の主面1m上の十字方向に所定のピッチで設けられた測定点における(hkil)面に由来するX線回折により測定される回折角の分布から行なわれる。したがって、X線回折の対象とされる(hkil)面は、解析に容易な強度の大きいX線回折ピークが得られる観点から、i=−(h+k)、かつ、h、kおよびlはそれぞれ−5以上5以下の整数であることが好ましい。   In the present embodiment, calculation of the curvature radius of the curvature of the (hkil) surface of the substrate 1 is not particularly limited, but for example, (hkil) at a measurement point provided at a predetermined pitch in the cross direction on the main surface 1m of the substrate. ) From the distribution of diffraction angles measured by X-ray diffraction originating from the surface. Therefore, the (hkil) plane that is the object of X-ray diffraction is i = − (h + k), and h, k, and l are − from the viewpoint of obtaining a high-intensity X-ray diffraction peak that is easy to analyze. It is preferably an integer of 5 or more and 5 or less.

(hkil)面の反りの曲率半径が2m以上である基板1は、基板1の内部歪みが小さいため、基板および基板の主面上にホモエピタキシャル成長させたIII族窒化物結晶の割れを抑制することができ、大型の結晶が得られる。基板1の内部歪みが小さく基板および基板上に成長させたIII族窒化物結晶の割れをより抑制する観点から、基板1の(hkil)面1nの反りの曲率半径は、5m以上が好ましく、10m以上がより好ましい。   The substrate 1 having a curvature radius of 2 m or more on the (hkil) plane suppresses cracking of the group III nitride crystal homoepitaxially grown on the substrate and the main surface of the substrate because the internal strain of the substrate 1 is small. Large crystals can be obtained. The curvature radius of the warp of the (hkil) surface 1n of the substrate 1 is preferably 5 m or more from the viewpoint of suppressing the internal strain of the substrate 1 and suppressing the cracking of the substrate and the group III nitride crystal grown on the substrate. The above is more preferable.

また、基板1としては、成長させるIII族窒化物結晶と化学組成が同じIII族窒化物種結晶を主面1m側に有するものであれば特に制限はなく、下地基板1b上にIII族窒化物種結晶1aが形成されているテンプレート基板、全体がIII族窒化物種結晶1aで形成されている自立基板などが挙げられる。ここで、液相法による結晶成長においては、基板として全体がIII族窒化物種結晶1aで形成されている自立基板を用いても、基板および基板上に成長させたIII族窒化物結晶に発生していた割れが、本実施形態の成長方法を用いることにより抑制される。かかる観点から、本実施形態の成長方法は、基板として全体がIII族窒化物種結晶1aで形成されている自立基板を用いる場合に、その有用性が高い。   The substrate 1 is not particularly limited as long as it has a group III nitride seed crystal having the same chemical composition as the group III nitride crystal to be grown on the main surface 1m side, and the group III nitride seed crystal on the base substrate 1b. Examples thereof include a template substrate on which la is formed and a free-standing substrate entirely formed of a group III nitride seed crystal 1a. Here, in the crystal growth by the liquid phase method, even if a free-standing substrate formed entirely of the group III nitride seed crystal 1a is used as the substrate, it occurs in the group and the group III nitride crystal grown on the substrate. The crack which has been suppressed is suppressed by using the growth method of this embodiment. From this point of view, the growth method of the present embodiment is highly useful when a self-supporting substrate that is entirely formed of a group III nitride seed crystal 1a is used as the substrate.

また、基板1の主面1mの面積は、特に制限はないが、1cm2以上であることが好ましく、10cm2以上であることがより好ましい。従来の液相法による結晶成長においては、基板の主面の面積が大きくなるほど基板および成長させた結晶が割れやすくなるのに対し、本実施形態の成長方法による結晶成長においては、主面の面積が大きくても基板および基板上に成長させた結晶の割れが抑制される。かかる点から、本実施形態の成長方法は、基板の主面の面積が大きくなるほど、その有用性が高い。 The area of the main surface 1m of the substrate 1 is not particularly limited, but is preferably 1 cm 2 or more, and more preferably 10 cm 2 or more. In crystal growth by the conventional liquid phase method, as the area of the main surface of the substrate increases, the substrate and the grown crystal are more likely to break, whereas in crystal growth by the growth method of the present embodiment, the area of the main surface. Even if it is large, cracks of the substrate and the crystal grown on the substrate are suppressed. From this point, the growth method of the present embodiment is more useful as the area of the main surface of the substrate increases.

また、基板1の主面1mは、特に制限はないが、(0001)面、(10−10)面および(10−11)面からなる群から選ばれる1種類の面であることが好ましい。液相法によるIII族窒化物結晶の成長においては、(0001)面、(10−10)面および(10−11)面が安定な結晶成長面であり、この面から大きく離れると、結晶成長面に凹凸が形成され、結晶欠陥が導入され、結晶が割れやすくなる。   Further, the main surface 1m of the substrate 1 is not particularly limited, but is preferably one type of surface selected from the group consisting of a (0001) plane, a (10-10) plane, and a (10-11) plane. In the growth of group III nitride crystals by the liquid phase method, the (0001) plane, the (10-10) plane, and the (10-11) plane are stable crystal growth planes. Irregularities are formed on the surface, crystal defects are introduced, and the crystal is easily broken.

本実施形態で準備される基板1は、平坦な主面1mを有し、少なくとも主面1m側にIII族窒化物結晶10と同じ化学組成を有するIII族窒化物種結晶1aを含み、主面1mに最も近い(hkil)面(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上であるものであれば特に制限はない。また、基板1のIII族窒化物種結晶1aは、HVPE法、MOCVD法などの気相法、溶液法、フラックス法などの液相法など、どのような方法によって成長されたものであってもよい。   The substrate 1 prepared in the present embodiment has a flat main surface 1m, includes a group III nitride seed crystal 1a having the same chemical composition as the group III nitride crystal 10 on at least the main surface 1m side, and includes a main surface 1m. Especially when the curvature radius of the curvature of the hkil plane closest to (where i = − (h + k), h, k and l are integers of −9 to 9) is 2 m or more. There is no limit. The group III nitride seed crystal 1a of the substrate 1 may be grown by any method such as a vapor phase method such as HVPE method or MOCVD method, a liquid phase method such as solution method or flux method. .

すなわち、基板の準備工程とは、どのようにして形成された基板であっても、液相法によりIII族窒化物結晶を成長させるための基板として、平坦な主面1mを有し、少なくとも主面1m側にIII族窒化物結晶10と同じ化学組成を有するIII族窒化物種結晶1aを含み、主面1mに最も近い(hkil)面(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上である基板1を選択する点に意義がある。   In other words, the substrate preparation step is a substrate for growing a group III nitride crystal by a liquid phase method, regardless of how the substrate is formed. A group III nitride seed crystal 1a having the same chemical composition as the group III nitride crystal 10 on the surface 1m side, the (hkil) plane closest to the main surface 1m (where i = − (h + k), h, It is significant that k and l are each selected from the substrate 1 having a curvature radius of curvature of 2 m or more.

本実施形態のIII族窒化物結晶の成長方法は、図1〜3を参照して、次に、基板1の主面にIII族金属とアルカリ金属を含む溶媒3に窒素含有ガス5を溶解させた溶液を接触させて、主面1m上にIII族窒化物結晶10を成長させる工程(III族窒化物結晶の成長工程)を備える。   1 to 3, next, a nitrogen-containing gas 5 is dissolved in a solvent 3 containing a group III metal and an alkali metal on the main surface of the substrate 1. And a step of growing the group III nitride crystal 10 on the main surface 1 m (group III nitride crystal growth step).

本実施形態におけるIII族窒化物結晶の成長工程においては、III族金属とアルカリ金属を含む溶媒3が用いられる。このようなIII族金属およびアルカリ金属を含む溶媒3を用いると、III族金属を含み不純物濃度(たとえば溶媒全体に対して1モル%未満の濃度)以上にはアルカリ金属を含まない溶媒を用いる場合に比べて、III族窒化物結晶の成長温度、成長圧力を低減させ、結晶成長速度を高めることができる。これは、溶媒3に含まれているアルカリ金属が、溶媒3への窒素含有物5の溶解を促進させるためと考えられる。   In the growth process of the group III nitride crystal in the present embodiment, a solvent 3 containing a group III metal and an alkali metal is used. When such a solvent 3 containing a group III metal and an alkali metal is used, a solvent containing a group III metal and containing no alkali metal at an impurity concentration (for example, a concentration of less than 1 mol% with respect to the whole solvent) is used. As compared with the above, it is possible to reduce the growth temperature and growth pressure of the group III nitride crystal and increase the crystal growth rate. This is presumably because the alkali metal contained in the solvent 3 promotes the dissolution of the nitrogen-containing material 5 in the solvent 3.

溶媒3に含まれるIII族金属MIIIとアルカリ金属MAとのモル比は、III族窒化物結晶の成長温度、成長圧力を低減させ、結晶成長速度を高めることができる範囲であれば特に制限はなく、MIII:MA=90:10〜10:90が好ましく、MIII:MA=50:50〜20:80がより好ましい。MIII:MA=90:10よりIII族金属MIIIのモル比が大きくても、MIII:MA=10:90よりアルカリ金属MAのモル比が大きくても、結晶成長速度が低下する。 The molar ratio of the Group III metal M III an alkali metal M A contained in the solvent 3, the growth temperature of the group III nitride crystal, to reduce the growth pressure, particularly as long as the can increase the crystal growth rate limit rather, M III: M A = 90 : 10~10: 90 are preferred, M III: M A = 50 : 50~20: 80 is more preferred. Even if the molar ratio of the group III metal M III is larger than M III : M A = 90: 10 or the molar ratio of the alkali metal M A is larger than M III : M A = 10: 90, the crystal growth rate decreases. To do.

かかるIII族窒化物結晶の成長工程は、たとえば、以下の複数のサブ工程によって行なわれる。まず、結晶成長容器23の底にその平坦な主面1mを上に向けて基板1が配置される(基板配置サブ工程)。結晶成長容器23には、特に制限はないが、耐熱性の観点から、BN(窒化ホウ素)製の坩堝などが好ましく用いられる。基板1は、少なくとも主面1m側にIII族窒化物結晶10と同じ化学組成を有するIII族窒化物種結晶1aを含む。   Such a group III nitride crystal growth step is performed, for example, by the following plurality of sub-steps. First, the substrate 1 is placed on the bottom of the crystal growth vessel 23 with the flat main surface 1m facing upward (substrate placement sub-step). Although there is no restriction | limiting in particular in the crystal growth container 23, From a heat resistant viewpoint, the crucible made from BN (boron nitride) etc. are used preferably. Substrate 1 includes a group III nitride seed crystal 1a having the same chemical composition as group III nitride crystal 10 at least on the principal surface 1m side.

次に、基板1が配置された結晶成長容器23内にIII族金属とアルカリ金属を含む溶媒3を入れる(溶媒配置サブ工程)。この溶媒3は室温(約25℃)中では固体であるが、後の加熱により液化する。III族金属とアルカリ金属を含む溶媒3には、制限はないが、純度の高いIII族窒化物結晶を成長させる観点から、III族金属およびアルカリ金属のそれぞれの純度が高いものが好ましい。たとえば、高純度のGaN結晶を成長させるためには、高純度の金属Gaと高純度の金属Naを用いることが好ましい。この場合、金属Gaの純度は、99質量%以上が好ましく、99.999質量%以上がより好ましい。金属Naの純度は、99質量%以上が好ましく、99.999質量%以上がより好ましい。ここで、III族金属とアルカリ金属を含む溶媒3の量は、特に制限はないが、液化した溶媒3(融液)の深さが基板1の主面1mから1mm以上50mm以下であることが好ましい。かかる深さが1mmより小さいと溶媒3(融液)の表面張力のため基板の全面を溶媒3(融液)が覆わない恐れがあり、50mmより大きいと溶媒3(融液)の液面からの窒素の供給が不足してしまうためである。   Next, the solvent 3 containing a group III metal and an alkali metal is placed in the crystal growth vessel 23 on which the substrate 1 is placed (solvent placement sub-step). This solvent 3 is solid at room temperature (about 25 ° C.), but is liquefied by subsequent heating. Although there is no restriction | limiting in the solvent 3 containing a group III metal and an alkali metal, From a viewpoint of growing a group III nitride crystal with high purity, the thing with high purity of each of a group III metal and an alkali metal is preferable. For example, in order to grow a high purity GaN crystal, it is preferable to use a high purity metal Ga and a high purity metal Na. In this case, the purity of the metal Ga is preferably 99% by mass or more, and more preferably 99.999% by mass or more. The purity of the metal Na is preferably 99% by mass or more, and more preferably 99.999% by mass or more. Here, the amount of the solvent 3 containing the group III metal and the alkali metal is not particularly limited, but the depth of the liquefied solvent 3 (melt) may be 1 mm or more and 50 mm or less from the main surface 1 m of the substrate 1. preferable. If the depth is less than 1 mm, the surface of the substrate may not be covered with the solvent 3 (melt) due to the surface tension of the solvent 3 (melt). If the depth is greater than 50 mm, the surface of the solvent 3 (melt) may not be covered. This is because the supply of nitrogen is insufficient.

次に、III金属とアルカリ金属を含む溶媒3および基板1が収容された結晶成長容器23を内容器21内に配置する(結晶成長容器配置サブ工程)。図1および図2においては、たとえば、5つの結晶成長容器23が配置されている。内容器21に複数の結晶成長容器23を配置することにより、同時に複数のIII族窒化物結晶10の成長が可能となる。   Next, the crystal growth vessel 23 containing the solvent 3 containing III metal and alkali metal and the substrate 1 is placed in the inner vessel 21 (crystal growth vessel placement sub-step). In FIG. 1 and FIG. 2, for example, five crystal growth vessels 23 are arranged. By disposing a plurality of crystal growth vessels 23 in the inner vessel 21, a plurality of group III nitride crystals 10 can be grown simultaneously.

次に、真空排気装置35を用いて、内容器21および外容器29の内部を真空排気する(真空排気サブ工程)。内容器21および外容器29の内部の不純物を除去するためである。このとき、バルブ41vおよび43vは閉じられており、バルブ47vおよび45vは開かれている。真空排気後の内容器21および外容器29の真空度は、特に制限はないが、残留不純物を低減する観点から、1Pa以下が好ましい。   Next, the inside of the inner container 21 and the outer container 29 is evacuated using the evacuation apparatus 35 (evacuation sub-process). This is for removing impurities inside the inner container 21 and the outer container 29. At this time, the valves 41v and 43v are closed, and the valves 47v and 45v are opened. The degree of vacuum of the inner container 21 and the outer container 29 after evacuation is not particularly limited, but is preferably 1 Pa or less from the viewpoint of reducing residual impurities.

次に、内容器21および外容器29内に、それぞれの容器の内圧が0.5MPa以上5MPa以下となるようにそれぞれ窒素含有ガス5および加圧用ガス7を供給する(窒素含有ガス供給サブ工程)。このとき、内容器21内に供給される窒素含有ガス5は、特に制限はないが、純度の高いIII族窒化物結晶を成長させる観点から、窒素の純度が高いことが好ましい。かかる観点から、窒素含有ガス5は、純度が99.999モル%以上の窒素ガスが好ましい。一方、外容器29に供給される加圧用ガス7は、外容器29内の圧力維持のために用いられIII族窒化物結晶の成長に用いられるものではないため、窒素含有ガスでなくともよい。ただし、外容器29内にはヒータ25が配置されているため、加圧用ガス7には、ヒータ25により反応を起こさない不活性ガス、たとえば窒素ガス、アルゴンガスなどが好ましく用いられる。   Next, the nitrogen-containing gas 5 and the pressurizing gas 7 are supplied into the inner container 21 and the outer container 29 so that the internal pressure of each container is 0.5 MPa or more and 5 MPa or less (nitrogen-containing gas supply sub-process). . At this time, the nitrogen-containing gas 5 supplied into the inner vessel 21 is not particularly limited, but it is preferable that the purity of nitrogen is high from the viewpoint of growing a high-purity group III nitride crystal. From this viewpoint, the nitrogen-containing gas 5 is preferably nitrogen gas having a purity of 99.999 mol% or more. On the other hand, the pressurizing gas 7 supplied to the outer container 29 is not used for growing a group III nitride crystal because it is used for maintaining the pressure in the outer container 29 and is not necessarily a nitrogen-containing gas. However, since the heater 25 is disposed in the outer container 29, an inert gas that does not react with the heater 25, such as nitrogen gas or argon gas, is preferably used for the pressurizing gas 7.

次に、ヒータ25を用いて、内容器21および外容器29の内部を加熱して、内容器21内部全体の温度を700℃以上900℃以下にする(加熱サブ工程)。かかる加熱により、内容器21に配置されたIII族金属とアルカリ金属を含む溶媒3は固体から液体(融液)となり、基板1の主面1mを覆い、この溶媒3(融液)に窒素含有ガス5が溶解する。このようにして、基板1の主面1mに、III族金属とアルカリ金属を含む溶媒3に窒素含有ガス5を溶解させた溶液を接触させることができる。ここで、ヒータ25は、内容器21および外容器29の内部の加熱に適したものであれば特に制限はないが、内容器および外容器の内部の温度分布の制御が容易な観点から、抵抗加熱方式のものが好ましく用いられる。   Next, the inside of the inner container 21 and the outer container 29 is heated using the heater 25, and the temperature inside the inner container 21 is set to 700 ° C. or higher and 900 ° C. or lower (heating sub-step). By such heating, the solvent 3 containing the group III metal and the alkali metal disposed in the inner container 21 changes from a solid to a liquid (melt), covers the main surface 1m of the substrate 1, and contains nitrogen in the solvent 3 (melt). Gas 5 dissolves. In this manner, a solution obtained by dissolving the nitrogen-containing gas 5 in the solvent 3 containing a group III metal and an alkali metal can be brought into contact with the main surface 1 m of the substrate 1. Here, the heater 25 is not particularly limited as long as it is suitable for heating the inside of the inner container 21 and the outer container 29. However, from the viewpoint of easy control of the temperature distribution inside the inner container and the outer container, the heater 25 is resistant. A heating system is preferably used.

加熱サブ工程中は、内容器21にさらに窒素含有ガス5を供給して、内容器21の内圧が外容器22の内圧に比べて0.01MPa以上0.1MPa以下の範囲で大きくなるようにする。すなわち、0.01MPa≦{(内容器の内圧)−(外容器の内圧)}≦0.1MPaとなるようにする。外容器29内の加圧用ガス7が内容器21内に混入するのを防止して、外容器29内の窒素の純度を高く維持するためである。   During the heating sub-process, the nitrogen-containing gas 5 is further supplied to the inner container 21 so that the inner pressure of the inner container 21 becomes larger in the range of 0.01 MPa to 0.1 MPa than the inner pressure of the outer container 22. . That is, 0.01 MPa ≦ {(inner pressure of inner container) − (inner pressure of outer container)} ≦ 0.1 MPa. This is because the pressurizing gas 7 in the outer container 29 is prevented from being mixed into the inner container 21 and the purity of nitrogen in the outer container 29 is kept high.

次に、内容器21への窒素含有ガス5の供給量および加熱量を調節して、内容器21内部全体の温度を700℃以上900℃以下に維持したまま内容器21の内圧を0.5MPa以上5MPa以下として、基板1の主面10m上にIII族窒化物結晶10を所定時間成長させる(結晶成長サブ工程)。このとき、外容器29への加圧用ガス7の供給量を調節して、外容器29の内圧を内容器21の内圧に比べて0.01MPa以上0.1MPa以下の範囲で小さくなるようにする。すなわち、結晶成長時においても加熱時と同様に、0.01MPa≦{(内容器の内圧)−(外容器の内圧)}≦0.1MPaとなるようにする。   Next, the supply amount and heating amount of the nitrogen-containing gas 5 to the inner container 21 are adjusted, and the inner pressure of the inner container 21 is set to 0.5 MPa while maintaining the temperature inside the inner container 21 at 700 ° C. or more and 900 ° C. or less. The group III nitride crystal 10 is grown on the main surface 10m of the substrate 1 for a predetermined time at a pressure of 5 MPa or less (crystal growth sub-step). At this time, the supply amount of the pressurizing gas 7 to the outer container 29 is adjusted so that the inner pressure of the outer container 29 becomes smaller than the inner pressure of the inner container 21 in the range of 0.01 MPa to 0.1 MPa. . That is, during the crystal growth, as in the heating, 0.01 MPa ≦ {(internal pressure of the inner container) − (internal pressure of the outer container)} ≦ 0.1 MPa.

次に、0.01MPa≦{(内容器の内圧)−(外容器の内圧)}≦0.1MPaの関係を維持しながら、内容器21および外容器29のそれぞれの内部を冷却および減圧下して、内容器21の結晶成長容器27から基板1上に成長したIII族窒化物結晶10を取り出す(結晶取り出しサブ工程)。   Next, while maintaining the relationship of 0.01 MPa ≦ {(inner pressure of inner container) − (inner pressure of outer container)} ≦ 0.1 MPa, the inside of each of inner container 21 and outer container 29 is cooled and reduced in pressure. Then, the group III nitride crystal 10 grown on the substrate 1 is taken out from the crystal growth vessel 27 of the inner vessel 21 (crystal removal sub-step).

(実施形態2)
本発明にかかるIII族窒化物結晶の一実施形態は、図3を参照して、実施形態1の成長方法により得られる。本実施形態のIII族窒化物結晶10は、実施形態1の方法により成長されたものであるため、大型の結晶となる。また、純度の高いIII族金属および窒素含有ガスを結晶原料として用いることにより、純度の高いIII族窒化物結晶となる。
(Embodiment 2)
One embodiment of a Group III nitride crystal according to the present invention is obtained by the growth method of Embodiment 1 with reference to FIG. Since the group III nitride crystal 10 of this embodiment is grown by the method of Embodiment 1, it becomes a large crystal. Further, by using a high-purity group III metal and a nitrogen-containing gas as a crystal raw material, a high-purity group III nitride crystal is obtained.

1.基板の準備
基板1として、HVPE法で作製した主面1mが研磨された平坦な(0001)Ga面で直径が2インチ(50.8mm)で厚さ350μmの自立性のGaN基板を多数準備した。いずれのGaN基板においても、その主面の中央部は、X線回折による測定結果から、(0001)面に対するオフ角が0.5°以下であった。かかる多数のGaN基板から、(0001)面の反りの曲率半径が1m以上2m未満のGaN基板、曲率半径が2m以上5m未満のGaN基板、曲率半径が5m以上10m未満のGaN基板、曲率半径が10m以上のGaN基板をそれぞれ10枚ずつ選別した。
1. Preparation of Substrate As a substrate 1, a number of self-supporting GaN substrates having a flat (0001) Ga surface with a polished main surface of 1 m and a diameter of 2 inches (50.8 mm) and a thickness of 350 μm prepared by the HVPE method were prepared. . In any GaN substrate, the central portion of the main surface has an off angle of 0.5 ° or less with respect to the (0001) plane from the measurement result by X-ray diffraction. From such a large number of GaN substrates, a GaN substrate having a curvature radius of (0001) plane of 1 m or more and less than 2 m, a GaN substrate having a curvature radius of 2 m or more and less than 5 m, a GaN substrate having a curvature radius of 5 m or more and less than 10 m, and a curvature radius of Ten GaN substrates each having a length of 10 m or more were selected.

ここで、GaN基板の(0001)面の曲率半径の測定は、基板の十字方向に5mmのピッチでX線回折による回折角の測定を行ない、その回折角の分布から曲率半径を算出した。ここで、1つの基板について十字の2方向から2つの曲率半径の値が算出されるが、それらの平均値をその基板の曲率半径とした。なお、曲率半径が算出された多数のGaN基板において、各基板の2つの曲率半径の数値に大きな差はなく、各基板の(0001)面はお椀状の形状をしていた。   Here, the measurement of the radius of curvature of the (0001) plane of the GaN substrate was performed by measuring the diffraction angle by X-ray diffraction at a pitch of 5 mm in the cross direction of the substrate, and calculating the radius of curvature from the distribution of the diffraction angles. Here, the values of two radii of curvature are calculated from two directions of the cross for one substrate, and the average value thereof is taken as the radius of curvature of the substrate. In many GaN substrates for which the curvature radii were calculated, there was no significant difference in the numerical values of the two curvature radii of each substrate, and the (0001) plane of each substrate had a bowl-like shape.

以下において、(0001)面の反りの曲率半径が1m以上2m未満のGaN基板を用いてGaN結晶を成長させる例を比較例1といい、曲率半径が2m以上5m未満のGaN基板を用いてGaN結晶を成長させる例を実施例1といい、曲率半径が5m以上10m未満のGaN基板を用いてGaN結晶を成長させる例を実施例3といい、曲率半径が10m以上のGaN基板を用いてGaN結晶を成長させる例を実施例4という。   Hereinafter, an example in which a GaN crystal is grown using a GaN substrate having a curvature radius of curvature of (0001) plane of 1 m or more and less than 2 m is referred to as Comparative Example 1, and a GaN substrate having a curvature radius of 2 m or more and less than 5 m is used. An example of growing a crystal is referred to as Example 1, and an example of growing a GaN crystal using a GaN substrate having a curvature radius of 5 m or more and less than 10 m is referred to as Example 3, and using a GaN substrate having a curvature radius of 10 m or more, GaN An example of growing crystals is referred to as Example 4.

2.GaN結晶の成長
図3を参照して、上記各GaN基板(基板1)を、その平坦な主面1mを上に向けて、内径60mmで深さ20mmのBN製坩堝(結晶成長容器23)の底に配置した。次に、GaN基板(基板1)が配置されたBN製坩堝(結晶成長容器23)内に、15gの純度99.9999質量%の金属Gaと11gの純度99.9999質量%の金属Na(溶媒3)を入れた。この金属Gaおよび金属Na(溶媒3)は室温(約25℃)中では固体であるが、後の加熱により液化して金属Ga(III族金属MIII)と金属Na(アルカリ金属MA)のモル比がMIII:MA=31:69の金属Ga−Na融液となり、この金属Ga−Na融液(溶媒3)の表面からGaN基板(基板1)の主面1mまでの深さが5mmとなった。
2. 3. Growth of GaN Crystal Referring to FIG. 3, each GaN substrate (substrate 1) is placed in a BN crucible (crystal growth vessel 23) having an inner diameter of 60 mm and a depth of 20 mm with the flat main surface 1 m facing upward. Placed on the bottom. Next, in a BN crucible (crystal growth vessel 23) on which a GaN substrate (substrate 1) is placed, 15 g of 99.9999% by mass of metal Ga and 11g of 99% by mass of metal Na (solvent) 3) was added. The metal Ga and metal Na (solvent 3) are solid at room temperature (about 25 ° C.), but are liquefied by subsequent heating to form metal Ga (group III metal M III ) and metal Na (alkali metal M A ). A metal Ga—Na melt with a molar ratio of M III : M A = 31: 69 is obtained, and the depth from the surface of this metal Ga—Na melt (solvent 3) to the main surface 1m of the GaN substrate (substrate 1) is It became 5 mm.

次に、GaN基板(基板1)ならびに金属Ga−Na融液(溶媒3)が収容されたBN製坩堝(結晶成長容器23)を5段にして内容器21内に配置した。   Next, a BN crucible (crystal growth vessel 23) containing a GaN substrate (substrate 1) and a metal Ga—Na melt (solvent 3) was placed in the inner vessel 21 in five stages.

次に、真空ポンプ(真空排気装置35)を用いて、内容器21および外容器29の内部を真空排気した。真空排気後の内容器21および外容器29の真空度は、1×10-3Paであった。 Next, the inside of the inner container 21 and the outer container 29 was evacuated using a vacuum pump (evacuation apparatus 35). The degree of vacuum of the inner container 21 and the outer container 29 after evacuation was 1 × 10 −3 Pa.

次に、内容器21および外容器29内に、それぞれの容器の内圧が1MPaとなるようにそれぞれ窒素含有ガス5および加圧用ガス7を供給した。このとき、内容器21内に供給される窒素含有ガス5には、純度が99.99999モル%の高純度の窒素ガスを用いた。一方、外容器29に供給される加圧用ガス7には、純度が99.9999モル%の窒素ガスを用いた。   Next, the nitrogen-containing gas 5 and the pressurizing gas 7 were supplied into the inner container 21 and the outer container 29 so that the inner pressure of each container was 1 MPa. At this time, high purity nitrogen gas having a purity of 99.99999 mol% was used as the nitrogen-containing gas 5 supplied into the inner vessel 21. On the other hand, nitrogen gas having a purity of 99.9999 mol% was used as the pressurizing gas 7 supplied to the outer container 29.

次に、抵抗加熱方式のヒータ25を用いて、内容器21および外容器29の内部を加熱して、内容器21内部全体の温度を800±5℃にした。かかる加熱により、内容器21に配置された金属Gaおよび金属Na(溶媒3)は液化して、GaN基板(基板1)の主面1mを覆い、この液化した金属Gaおよび金属Naすなわち金属Ga−Na融液(溶媒3)に高純度の窒素ガス(窒素含有ガス5)が溶解する。このようにして、GaN基板(基板1)の主面1mに、金属Ga−Na融液(溶媒3)に高純度の窒素ガス(窒素含有ガス5)を溶解させた溶液を接触させることができた。加熱中は、内容器21にさらに高純度の窒素ガス(窒素含有ガス5)を供給して、内容器21の内圧が外容器22の内圧に比べて0.01MPa以上0.1MPa以下の範囲で大きくなるようにした。すなわち、0.01MPa≦{(内容器の内圧)−(外容器の内圧)}≦0.1MPaとなるようにした。   Next, the inside of the inner container 21 and the outer container 29 was heated using a resistance heating type heater 25, and the temperature inside the inner container 21 was set to 800 ± 5 ° C. By such heating, the metal Ga and metal Na (solvent 3) disposed in the inner container 21 are liquefied to cover the main surface 1m of the GaN substrate (substrate 1), and the liquefied metal Ga and metal Na, that is, metal Ga— High purity nitrogen gas (nitrogen-containing gas 5) is dissolved in the Na melt (solvent 3). In this way, the main surface 1m of the GaN substrate (substrate 1) can be brought into contact with a solution obtained by dissolving high purity nitrogen gas (nitrogen-containing gas 5) in a metal Ga—Na melt (solvent 3). It was. During heating, nitrogen gas of higher purity (nitrogen-containing gas 5) is supplied to the inner container 21 so that the inner pressure of the inner container 21 is in the range of 0.01 MPa or more and 0.1 MPa or less compared to the inner pressure of the outer container 22. I tried to get bigger. That is, 0.01 MPa ≦ {(internal pressure of the inner container) − (internal pressure of the outer container)} ≦ 0.1 MPa.

次に、内容器21への窒素含有ガス5の供給量および加熱量を調節して、内容器21内部全体の温度を800±5℃に維持したまま内容器21の内圧を3MPaとして、GaN基板(基板1)の主面10m上にGaN結晶(III族窒化物結晶10)を100時間成長させた。このとき、外容器29への窒素ガス(加圧用ガス7)の供給量を調節して、外容器29の内圧を内容器21の内圧に比べて0.01MPa以上0.1MPa以下の範囲で小さくなるようにした。すなわち、結晶成長時においても加熱時と同様に、0.01MPa≦{(内容器の内圧)−(外容器の内圧)}≦0.1MPaとなるようにした。   Next, the supply amount and heating amount of the nitrogen-containing gas 5 to the inner container 21 are adjusted, and the internal pressure of the inner container 21 is set to 3 MPa while maintaining the temperature inside the inner container 21 at 800 ± 5 ° C. A GaN crystal (Group III nitride crystal 10) was grown on the main surface 10m of (Substrate 1) for 100 hours. At this time, the supply amount of nitrogen gas (pressurizing gas 7) to the outer container 29 is adjusted so that the internal pressure of the outer container 29 is smaller than the internal pressure of the inner container 21 in the range of 0.01 MPa to 0.1 MPa. It was made to become. That is, during the crystal growth, as in the heating, 0.01 MPa ≦ {(inner pressure in the inner container) − (inner pressure in the outer container)} ≦ 0.1 MPa.

次に、0.01MPa≦{(内容器の内圧)−(外容器の内圧)}≦0.1MPaの関係を維持しながら、内容器21および外容器29のそれぞれの内部を冷却および減圧下して、30℃に冷却された内容器21のBN製坩堝(結晶成長容器27)の金属Ga−Na融液(溶媒3)からGaN基板(基板1)上に成長したGaN結晶(III族窒化物結晶10)をピンセットで取り出した。得られたGaN結晶の厚さは、850μm〜1050μmであった。   Next, while maintaining the relationship of 0.01 MPa ≦ {(inner pressure of inner container) − (inner pressure of outer container)} ≦ 0.1 MPa, the inside of each of inner container 21 and outer container 29 is cooled and reduced in pressure. The GaN crystal (Group III nitride) grown on the GaN substrate (substrate 1) from the metal Ga—Na melt (solvent 3) in the BN crucible (crystal growth vessel 27) of the inner vessel 21 cooled to 30 ° C. Crystal 10) was removed with tweezers. The thickness of the obtained GaN crystal was 850 μm to 1050 μm.

比較例1の10枚のGaN基板(反りの曲率半径が1m以上2m未満)上にそれぞれ成長させたGaN結晶は、10枚中全てが割れていた。これに対して、実施例1の10枚のGaN基板(反りの曲率半径が2m以上5m未満)上にそれぞれ成長させたGaN結晶は、10枚中割れていたのは6枚であった。また、実施例2の10枚のGaN基板(反りの曲率半径が5m以上10m未満)上にそれぞれ成長させたGaN結晶は、10枚中割れていたのは2枚であった。また、実施例3の10枚のGaN基板(反りの曲率半径が10m以上)上にそれぞれ成長させたGaN結晶は、10枚中割れていたものは無かった。結果を表1にまとめた。   All of the GaN crystals grown on the 10 GaN substrates of Comparative Example 1 (the curvature radius of warpage is 1 m or more and less than 2 m) were cracked. On the other hand, GaN crystals grown on 10 GaN substrates of Example 1 (the curvature radius of warpage was 2 m or more and less than 5 m) were cracked in 10 out of 6 sheets. In addition, GaN crystals grown on 10 GaN substrates of Example 2 (the curvature radius of warpage was 5 m or more and less than 10 m) were cracked in 10 pieces, and two pieces. In addition, none of the GaN crystals grown on each of the 10 GaN substrates of Example 3 (the curvature radius of warpage was 10 m or more) was cracked in 10 pieces. The results are summarized in Table 1.

Figure 0004528806
Figure 0004528806

表1から明らかなように、液相法によるIII族窒化物結晶の成長において、主面に最も近い(hkil)面(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上、好ましくは5m以上、より好ましくは10m以上の基板を用いることにより、その基板およびその基板上に成長させたIII族窒化物結晶の割れが抑制され、大型のIII族窒化物結晶が得られることがわかった。   As apparent from Table 1, in the growth of the group III nitride crystal by the liquid phase method, the (hkil) plane closest to the main surface (where i = − (h + k), where h, k, and l are −9 or more and an integer of 9 or less) using a substrate having a curvature radius of warpage of 2 m or more, preferably 5 m or more, more preferably 10 m or more, the substrate and the group III nitride crystal grown on the substrate It was found that cracking was suppressed and a large group III nitride crystal was obtained.

今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記した説明でなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内のすべての変更が含まれることが意図される。   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.

本発明にかかる成長方法により得られたIII族窒化物結晶は、発光ダイオード、レーザダイオードなどの発光素子、整流器、バイポーラトランジスタ、電界効果トランジスタ、HEMT(高電子移動度トランジスタ)などの電子素子、温度センサ、圧力センサ、放射線センサ、可視−紫外光検出などの半導体センサ、SAWデバイス(表面弾性波素子)、振動子、共振子、発振器、MEMS(微小電子機械システム)部品、圧電アクチュエータなどのデバイス用の基板などに用いられる。   Group III nitride crystals obtained by the growth method according to the present invention include light-emitting elements such as light-emitting diodes and laser diodes, electronic elements such as rectifiers, bipolar transistors, field-effect transistors, and HEMTs (high electron mobility transistors), temperature For sensors, pressure sensors, radiation sensors, semiconductor sensors such as visible-ultraviolet light detection, SAW devices (surface acoustic wave elements), vibrators, resonators, oscillators, MEMS (microelectromechanical system) components, piezoelectric actuators, etc. It is used for the substrate.

本発明にかかるIII族窒化物結晶の成長方法および成長装置の一実施形態を示す概略断面図である。It is a schematic sectional drawing which shows one Embodiment of the growth method and growth apparatus of the group III nitride crystal concerning this invention. 図1のII部分を拡大した概略断面図である。It is the schematic sectional drawing to which the II part of FIG. 1 was expanded. 図2のIII部分を拡大した概略断面図である。It is the schematic sectional drawing to which the III part of FIG. 2 was expanded.

符号の説明Explanation of symbols

1 基板、1a III族窒化種物結晶、1b 下地基板、1m 主面、1n (hkil)面、3 溶媒、5 窒素含有ガス、7 加圧用ガス、10 III族窒化物結晶、21 内容器、23 結晶成長容器、25 ヒータ、27 断熱材、29 外容器、31 窒素含有ガス供給装置、33 加圧用ガス供給装置、35 真空排気装置、41 第1の配管、41a,43a バルブより内容器側の部分、41b バルブより窒素含有ガス供給装置側の部分、41p,43p 圧力計、41v,43v,45v,47v バルブ、43 第2の配管、43b バルブより加圧用ガス供給装置側の部分、45 第3の配管、45a バルブより外容器側の部分、45b バルブより真空排気装置側の部分、47 第4の配管。   DESCRIPTION OF SYMBOLS 1 Substrate, 1a Group III nitride seed crystal, 1b Base substrate, 1m main surface, 1n (hkil) surface, 3 solvent, 5 nitrogen-containing gas, 7 gas for pressurization, 10 Group III nitride crystal, 21 inner vessel, 23 Crystal growth vessel, 25 heater, 27 heat insulating material, 29 outer vessel, 31 nitrogen-containing gas supply device, 33 gas supply device for pressurization, 35 vacuum exhaust device, 41 first pipe, 41a, 43a portion closer to inner vessel than valve 41b, nitrogen-containing gas supply device side, 41p, 43p pressure gauge, 41v, 43v, 45v, 47v valve, 43 second piping, 43b valve, pressurization gas supply device side, 45 third Piping, part on the outer container side from the 45a valve, part on the vacuum exhaust device side from the 45b valve, 47 fourth piping.

Claims (5)

液相法によるGaN結晶の成長方法であって、
平坦な主面を有し、全体が前記GaN結晶と同じ化学組成を有するGaN種結晶で形成される自立の基板であって、前記主面に最も近い(hkil)面(ここで、i=−(h+k)であり、h、kおよびlはそれぞれ−9以上9以下の整数)の反りの曲率半径が2m以上である基板を準備する工程と、
前記基板の前記主面に、Ga金属とアルカリ金属を含む溶媒に窒素含有ガスを溶解させた溶液を接触させて、前記主面上に前記GaN結晶を成長させる工程と、を備えるGaN結晶の成長方法。
A method for growing a GaN crystal by a liquid phase method,
Has a flat main surface, a substrate free standing formed of GaN seed crystal whole has the same chemical composition as the GaN crystal, the nearest (hkil) plane to the principal plane (here, i = - (H + k), and h, k, and l are integers of −9 or more and 9 or less, respectively, and a step of preparing a substrate having a curvature radius of 2 m or more;
On the main surface of the substrate, by contacting a solution of a nitrogen-containing gas in a solvent containing a Ga metal and alkali metal, growth of GaN crystal and a step of growing said GaN crystal on the main surface Method.
前記曲率半径が5m以上である請求項1に記載のGaN結晶の成長方法。 The method for growing a GaN crystal according to claim 1, wherein the radius of curvature is 5 m or more. 前記曲率半径が10m以上である請求項1に記載のGaN結晶の成長方法。 The method for growing a GaN crystal according to claim 1, wherein the radius of curvature is 10 m or more. 前記主面の面積が1cm2以上である請求項1から請求項までのいずれかに記載のGaN結晶の成長方法。 The method for growing a GaN crystal according to any one of claims 1 to 3, wherein an area of the main surface is 1 cm 2 or more. 前記主面は、(0001)面、(10−10)面および(10−11)面からなる群から選ばれる1種類の面である請求項1から請求項までのいずれかに記載のGaN結晶の成長方法。 The main surface is (0001) plane, GaN according to claim 1 which is one type of a surface selected from the group of (10-10) plane and (10-11) plane to claim 4 Crystal growth method.
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