JP2012006794A

JP2012006794A - GROWTH METHOD OF GaN CRYSTAL

Info

Publication number: JP2012006794A
Application number: JP2010144973A
Authority: JP
Inventors: Shinsuke Fujiwara; 伸介藤原
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2010-06-25
Filing date: 2010-06-25
Publication date: 2012-01-12

Abstract

【課題】主面の面積が大きな大口径のＧａＮ結晶基板を効率よく生産するためのＧａＮ結晶の成長方法を提供する。
【解決手段】ＧａＮ種結晶基板１０１の主面１０１ｓ上に第１の気相法により第１のＧａＮ結晶１１０を成長させ、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の少なくともいずれかを加工することによりＧａＮ種結晶基板１０１の主面１０１ｓに比べて面積が小さな主面１１１ｓを有する少なくとも１つの第１のＧａＮ結晶基板１１１を得て、この第１のＧａＮ結晶基板１１１ｂを液相法により成長させることにより第１のＧａＮ結晶基板１１１ｂの主面１１１ｂｓに比べて面積が大きな主面１１２ｓを有する第２のＧａＮ結晶基板１１２を得て、この第２のＧａＮ結晶基板１１２の主面１１２ｓ上に第２の気相法により第２のＧａＮ結晶１２０の成長させる。
【選択図】図１A GaN crystal growth method for efficiently producing a large-diameter GaN crystal substrate having a large main surface area.
A first GaN crystal 110 is grown on a main surface 101s of a GaN seed crystal substrate 101 by a first vapor phase method, and at least one of the GaN seed crystal substrate 101 and the first GaN crystal 110 is processed. As a result, at least one first GaN crystal substrate 111 having a main surface 111s having a smaller area than the main surface 101s of the GaN seed crystal substrate 101 is obtained, and the first GaN crystal substrate 111b is obtained by a liquid phase method. By growing, a second GaN crystal substrate 112 having a main surface 112s having a larger area than the main surface 111bs of the first GaN crystal substrate 111b is obtained, and on the main surface 112s of the second GaN crystal substrate 112 Then, the second GaN crystal 120 is grown by the second vapor phase method.
[Selection] Figure 1

Description

本発明は、主面の面積が大きな大口径のＧａＮ結晶基板を効率よく生産するためのＧａＮ結晶の成長方法に関する。 The present invention relates to a GaN crystal growth method for efficiently producing a large-diameter GaN crystal substrate having a large principal surface area.

近年、ＬＥＤ（発光ダイオード）、ＬＤ（レーザダイオード）などの光デバイス、電子デバイスなどの半導体デバイス用の基板として、主面の面積が大きな大口径のＧａＮ結晶基板が求められている。 In recent years, a large-diameter GaN crystal substrate having a large main surface area is required as a substrate for semiconductor devices such as optical devices such as LEDs (light emitting diodes) and LD (laser diodes) and electronic devices.

このような大口径のＧａＮ結晶基板を製造するために、特開２００５−２３６２６１号公報（以下、特許文献１という。）は、下地基板上にフラックス法などの液相法により第１のＩＩＩ族窒化物結晶として第１のＧａＮ（窒化ガリウム）結晶を成長させる工程と、この第１のＧａＮ結晶上にＨＶＰＥ（ハイドライド気相成長）法などの気相法により第２のＩＩＩ族窒化物結晶として第２のＧａＮ結晶を成長させる方法を提案する。 In order to manufacture such a large-diameter GaN crystal substrate, Japanese Patent Laying-Open No. 2005-236261 (hereinafter referred to as Patent Document 1) discloses a first group III on a base substrate by a liquid phase method such as a flux method. A step of growing a first GaN (gallium nitride) crystal as a nitride crystal and a second group III nitride crystal by a vapor phase method such as HVPE (hydride vapor phase epitaxy) method on the first GaN crystal A method for growing a second GaN crystal is proposed.

特開２００５−２３６２６１号公報JP 2005-236261 A

しかしながら、ＨＶＰＥ法などの気相法により成長させた第２のＧａＮ結晶は、結晶成長とともに第２のＧａＮ結晶の外周部に結晶成長主面以外のファセットが形成される。このため、第２のＧａＮ結晶を加工して得られるＧａＮ結晶基板は、下地基板とされた第１のＧａＮ結晶に比べて、主面の面積が小さくすなわち口径が小さくなる。 However, in the second GaN crystal grown by the vapor phase method such as the HVPE method, facets other than the crystal growth main surface are formed in the outer peripheral portion of the second GaN crystal as the crystal grows. For this reason, the GaN crystal substrate obtained by processing the second GaN crystal has a smaller main surface area, that is, a smaller aperture than the first GaN crystal used as the base substrate.

すなわち、ＨＶＰＥ法などの気相法では、下地基板として用いたＧａＮ結晶基板の主面の面積以上の主面を有するＧａＮ結晶基板を再生産することが難しい。このため、主面の面積が大きな大口径のＧａＮ結晶基板を得るために、下地基板として主面の面積が大きな大口径のサファイア基板、ＧａＡｓ基板などのＧａＮと化学式が異なる基板上にＧａＮ結晶をヘテロエピタキシャル成長させる必要があり、結晶性を高めることが困難であり、生産コストも高くなっていた。 That is, in a vapor phase method such as the HVPE method, it is difficult to reproduce a GaN crystal substrate having a main surface larger than the area of the main surface of the GaN crystal substrate used as the base substrate. Therefore, in order to obtain a large-diameter GaN crystal substrate having a large main surface area, a GaN crystal is formed on a substrate having a chemical formula different from that of GaN, such as a large-diameter sapphire substrate or a GaAs substrate having a large main surface area as a base substrate. It is necessary to perform heteroepitaxial growth, it is difficult to increase crystallinity, and the production cost is high.

本発明は、上記問題点を解決して、主面の面積が大きな大口径のＧａＮ結晶基板を効率よく生産するためのＧａＮ結晶の成長方法を提供することを目的とする。 An object of the present invention is to solve the above problems and to provide a GaN crystal growth method for efficiently producing a large-diameter GaN crystal substrate having a large main surface area.

本発明は、ＧａＮ種結晶基板を準備する工程と、ＧａＮ種結晶基板の主面上に第１の気相法により第１のＧａＮ結晶を成長させる工程と、ＧａＮ種結晶基板および第１のＧａＮ結晶の少なくともいずれかを加工することによりＧａＮ種結晶基板の主面に比べて面積が小さな主面を有する少なくとも１つの第１のＧａＮ結晶基板を得る工程と、第１のＧａＮ結晶基板を液相法により成長させることにより第１のＧａＮ結晶基板の主面に比べて面積が大きな主面を有する第２のＧａＮ結晶基板を得る工程と、第２のＧａＮ結晶基板の主面上に第２の気相法により第２の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 includes a step of preparing a GaN seed crystal substrate, a step of growing a first GaN crystal on a main surface of the GaN seed crystal substrate by a first vapor phase method, a GaN seed crystal substrate and a first GaN Processing at least one of the crystals to obtain at least one first GaN crystal substrate having a main surface with a smaller area than the main surface of the GaN seed crystal substrate; and A second GaN crystal substrate having a main surface with a larger area than the main surface of the first GaN crystal substrate by growing by the method, and a second GaN crystal substrate on the main surface of the second GaN crystal substrate. And a step of growing a second GaN crystal by a vapor phase method.

本発明にかかるＧａＮ結晶の成長方法において、第２のＧａＮ結晶基板の主面の面積を、ＧａＮ種結晶基板の主面の面積以上とすることができる。さらに、第１のＧａＮ結晶基板は、第１のＧａＮ結晶の中央よりも結晶成長主面側の結晶成長後半領域から加工して得ることができる。また、第１のＧａＮ結晶基板は、ＧａＮ種結晶基板および第１のＧａＮ結晶の中央よりもＧａＮ種結晶基板側の結晶成長前半領域の少なくともいずれかから加工して得ることができる。 In the GaN crystal growth method according to the present invention, the area of the main surface of the second GaN crystal substrate can be made equal to or larger than the area of the main surface of the GaN seed crystal substrate. Furthermore, the first GaN crystal substrate can be obtained by processing from the crystal growth latter half region closer to the crystal growth main surface than the center of the first GaN crystal. In addition, the first GaN crystal substrate can be obtained by processing from at least one of the GaN seed crystal substrate and the first half region of crystal growth closer to the GaN seed crystal substrate than the center of the first GaN crystal.

本発明によれば、主面の面積が大きな大口径のＧａＮ結晶基板を効率よく生産するためのＧａＮ結晶の成長方法を提供することができる。 According to the present invention, it is possible to provide a GaN crystal growth method for efficiently producing a large-diameter GaN crystal substrate having a large main surface area.

本発明にかかるＧａＮ結晶の成長方法のある例を示す概略断面図である。It is a schematic sectional drawing which shows a certain example of the growth method of the GaN crystal concerning this invention. 本発明にかかるＧａＮ結晶の成長方法の別の例を示す概略断面図である。It is a schematic sectional drawing which shows another example of the growth method of the GaN crystal concerning this invention. 本発明にかかるＧａＮ結晶の成長方法のさらに別の例を示す概略断面図である。It is a schematic sectional drawing which shows another example of the growth method of the GaN crystal concerning this invention.

図１〜図３を参照して、本発明のある実施形態であるＧａＮ結晶の成長方法は、ＧａＮ種結晶基板１０１を準備する工程（図１（Ａ）、図２（Ａ）および図３（Ａ））と、ＧａＮ種結晶基板１０１の主面１０１ｓ上に第１の気相法により第１のＧａＮ結晶１１０を成長させる工程（図１（Ｂ）、図２（Ｂ）および図３（Ｂ））と、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の少なくともいずれかを加工することにより、ＧａＮ種結晶基板１０１の主面１０１ｓに比べて面積が小さな主面１１１ｓを有する少なくとも１つの第１のＧａＮ結晶基板１１１を得る工程（図１（Ｃ）および（Ｄ）、図２（Ｃ）および（Ｄ）、ならびに図３（Ｃ）および（Ｄ））と、第１のＧａＮ結晶基板１１１を液相法により成長させることにより、第１のＧａＮ結晶基板１１１の主面１１１ｓに比べて面積が大きな主面１１２ｓを有する第２のＧａＮ結晶基板１１２を得る工程（図１（Ｅ）、図２（Ｅ）および図３（Ｅ））と、第２のＧａＮ結晶基板１１２の主面１１２ｓ上に第２の気相法により第２のＧａＮ結晶１２０を成長させる工程（図１（Ｆ）、図２（Ｆ）および図３（Ｆ））と、を備える。かかるＧａＮ結晶の成長方法により、主面の面積が大きな大口径のＧａＮ結晶基板を効率よく生産することができる。 1 to 3, a method for growing a GaN crystal according to an embodiment of the present invention includes a step of preparing a GaN seed crystal substrate 101 (FIGS. 1A, 2A, and 3). A)) and a step of growing the first GaN crystal 110 on the main surface 101s of the GaN seed crystal substrate 101 by the first vapor phase method (FIGS. 1B, 2B, and 3B). )), And processing at least one of the GaN seed crystal substrate 101 and the first GaN crystal 110, whereby at least one first surface having a main surface 111s having a smaller area than the main surface 101s of the GaN seed crystal substrate 101 is obtained. Steps of obtaining one GaN crystal substrate 111 (FIGS. 1C and 1D, FIGS. 2C and 2D, and FIGS. 3C and 3D), and the first GaN crystal substrate 111 Is grown by the liquid phase method. A step of obtaining a second GaN crystal substrate 112 having a main surface 112s having a larger area than the main surface 111s of the GaN crystal substrate 111 (FIGS. 1E, 2E, and 3E) Step of growing second GaN crystal 120 on main surface 112s of second GaN crystal substrate 112 by the second vapor phase method (FIG. 1F, FIG. 2F, and FIG. 3F) And comprising. By such a GaN crystal growth method, a large-diameter GaN crystal substrate having a large main surface area can be efficiently produced.

［ＧａＮ種結晶基板の準備工程］
図１（Ａ）、図２（Ａ）および図３（Ａ）を参照して、本実施形態のＧａＮ結晶の製造方法は、ＧａＮ種結晶基板１０１を準備する工程を備える。ＧａＮ種結晶基板１０１を準備する工程は、特に制限はなく、主面の面積が大きい大口径の下地基板上に気相法または液相法によりＧａＮ種結晶を成長させ、得られたＧａＮ種結晶の外周部を除去し、下地基板の主面に平行な面でスライスし、スライス面を研磨するなどの加工をすることによりＧａＮ種結晶基板１０１が得られる。 [Preparation process of GaN seed crystal substrate]
With reference to FIG. 1A, FIG. 2A, and FIG. 3A, the GaN crystal manufacturing method of this embodiment includes a step of preparing a GaN seed crystal substrate 101. The step of preparing the GaN seed crystal substrate 101 is not particularly limited, and the GaN seed crystal obtained by growing a GaN seed crystal by a vapor phase method or a liquid phase method on a large-diameter base substrate having a large main surface area. The GaN seed crystal substrate 101 is obtained by removing the outer peripheral portion of the substrate, slicing it with a plane parallel to the main surface of the base substrate, and polishing the slice surface.

ＧａＮ種結晶の成長に用いられる下地基板は、特に制限はないが、転位密度が低く結晶性の高いＧａＮ種結晶を成長させる観点から、ＧａＮ種結晶の格子定数との整合性が高い基板が好ましい。たとえば、サファイア基板、ＳｉＣ（炭化珪素）基板、ＧａＡｓ（砒化ガリウム）基板などが好ましく、ＩＩＩ族窒化物基板がより好ましく、ＧａＮ基板がさらに好ましい。また、ＧａＮ種結晶を成長させる方法は、特に制限はないが、転位密度（主面および／または主面に平行な面における平均の転位密度をいう。以下同じ。）が低く結晶性の高いＧａＮ種結晶を成長させる観点から、ＨＶＰＥ（ハイドライド気相エピタキシ）法、ＭＯＣＶＤ（有機金属化学気相堆積）法、ＭＢＥ（分子線エピタキシ）法などの気相法、フラックス法、高窒素圧溶液法などの液相法、液相法に類似した方法であるアモノサーマル法などが好適に用いられる。 The base substrate used for the growth of the GaN seed crystal is not particularly limited, but a substrate having high consistency with the lattice constant of the GaN seed crystal is preferable from the viewpoint of growing a GaN seed crystal having a low dislocation density and high crystallinity. . For example, a sapphire substrate, a SiC (silicon carbide) substrate, a GaAs (gallium arsenide) substrate, and the like are preferable, a group III nitride substrate is more preferable, and a GaN substrate is further preferable. The method for growing the GaN seed crystal is not particularly limited, but GaN having a low dislocation density (referred to as an average dislocation density in the main surface and / or a plane parallel to the main surface; hereinafter the same) and high crystallinity. From the viewpoint of growing seed crystals, gas phase methods such as HVPE (hydride vapor phase epitaxy), MOCVD (metal organic chemical vapor deposition), MBE (molecular beam epitaxy), flux method, high nitrogen pressure solution method, etc. The liquid phase method and the ammonothermal method which is a method similar to the liquid phase method are preferably used.

［第１のＧａＮ結晶を得る工程］
図１（Ｂ）、図２（Ｂ）および図３（Ｂ）を参照して、本実施形態のＧａＮ結晶の製造方法は、ＧａＮ種結晶基板１０１の主面１０１ｓ上に第１の気相法により第１のＧａＮ結晶１１０を成長させる工程を備える。かかる第１のＧａＮ結晶１１０を成長させる工程により、転位密度の低い第１のＧａＮ結晶１１０が得られる。 [Step of obtaining first GaN crystal]
With reference to FIG. 1B, FIG. 2B, and FIG. 3B, the GaN crystal manufacturing method of the present embodiment uses the first vapor phase method on the main surface 101s of the GaN seed crystal substrate 101. The step of growing the first GaN crystal 110 is performed. By the step of growing the first GaN crystal 110, the first GaN crystal 110 having a low dislocation density is obtained.

第１の気相法は、転位密度が低く結晶性の高い第１のＧａＮ結晶１１０を成長させる方法であれば特に制限はなく、ＨＶＰＥ法、ＭＯＣＶＤ法、ＭＢＥ法、昇華法などが用いられるが、結晶成長速度が高い観点からＨＶＰＥ法が好適に用いられる。ＨＶＰＥ法などの気相法で成長させた第１のＧａＮ結晶１１０は、ＧａＮ種結晶基板１０１の主面１０１ｓから遠い位置になるほど、転位密度が低くなるとともに、外周部に（１０−１１）面および（１１−２２）面の少なくともいずれかのファセット１１０ｆが形成され、外周径が小さくなる。また、第１のＧａＮ結晶１１０の外周部には（１０−１０）面のファセット１１０ｅも形成されるが、かかる（１０−１０）面にはＧａＮ多結晶が成長しやすい。 The first vapor phase method is not particularly limited as long as the first GaN crystal 110 having a low dislocation density and high crystallinity is grown, and an HVPE method, an MOCVD method, an MBE method, a sublimation method, or the like is used. From the viewpoint of high crystal growth rate, the HVPE method is preferably used. The first GaN crystal 110 grown by a vapor phase method such as the HVPE method has a lower dislocation density and a (10-11) plane on the outer periphery as the position is farther from the main surface 101s of the GaN seed crystal substrate 101. And the facet 110f of at least one of the (11-22) plane is formed, and the outer diameter is reduced. In addition, a (10-10) facet 110e is also formed on the outer periphery of the first GaN crystal 110, and GaN polycrystals are likely to grow on the (10-10) plane.

［第１のＧａＮ結晶基板を得る工程］
図１（Ｃ）、図２（Ｃ）および図３（Ｃ）を参照して、本実施形態のＧａＮ結晶の製造方法は、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の少なくともいずれかを加工することにより、ＧａＮ種結晶基板１０１の主面１０１ｓに比べて面積が小さな主面１１１ｓを有する少なくとも１つの第１のＧａＮ結晶基板１１１を得る工程を備える。 [Step of obtaining first GaN crystal substrate]
With reference to FIG. 1C, FIG. 2C, and FIG. 3C, the method of manufacturing a GaN crystal according to the present embodiment uses at least one of the GaN seed crystal substrate 101 and the first GaN crystal 110. By processing, the method includes a step of obtaining at least one first GaN crystal substrate 111 having a main surface 111s having a smaller area than the main surface 101s of the GaN seed crystal substrate 101.

上記のように、第１のＧａＮ結晶１１０は、外周部に（１０−１１）面および（１１−２２）面の少なくともいずれかのファセット１１０ｆが形成され、外周径が小さくなる。また、外周部に（１０−１０）面のファセット１１０ｅが形成されて、（１０−１０）面にＧａＮ多結晶が成長する。このため、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の少なくともいずれかから、その外周部を除去する加工をして得られる第１のＧａＮ結晶基板１１１の主面１１１ｓの面積は、ＧａＮ種結晶基板１０１の主面１０１ｓの面積より小さくなる。 As described above, in the first GaN crystal 110, the facet 110f of at least one of the (10-11) plane and the (11-22) plane is formed in the outer peripheral portion, and the outer peripheral diameter becomes small. Further, a (10-10) facet 110e is formed on the outer periphery, and a GaN polycrystal grows on the (10-10) plane. For this reason, the area of the main surface 111s of the first GaN crystal substrate 111 obtained by processing to remove the outer peripheral portion from at least one of the GaN seed crystal substrate 101 and the first GaN crystal 110 is the GaN seed. It becomes smaller than the area of the main surface 101 s of the crystal substrate 101.

ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の少なくともいずれかを少なくとも１つの第１のＧａＮ結晶基板１１１に加工する工程には、特に制限はなく、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の外周部を除去するサブ工程、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０をＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離するサブ工程、かかる分離により得られた第１のＧａＮ結晶基板１１１の分離された面を研磨するサブ工程などが含まれる。これらの外周部除去サブ工程、分離サブ工程の順序には特に制限はなく、たとえば以下の方法がある。 There is no particular limitation on the process of processing at least one of the GaN seed crystal substrate 101 and the first GaN crystal 110 into at least one first GaN crystal substrate 111, and the GaN seed crystal substrate 101 and the first GaN crystal are not limited. A sub-step of removing the outer peripheral portion of 110, a sub-step of separating the GaN seed crystal substrate 101 and the first GaN crystal 110 in a plane parallel to the main surface 101s of the GaN seed crystal substrate 101, and the first obtained by such separation A sub-process for polishing the separated surface of the GaN crystal substrate 111 is included. There is no restriction | limiting in particular in the order of these outer peripheral part removal sub processes and isolation | separation sub processes, For example, there exists the following method.

（第１のＧａＮ結晶基板への加工工程の形態１）
図１（Ｃ）を参照して、第１のＧａＮ結晶基板への加工工程のある形態は、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の外周部を除去するサブ工程と、外周部が除去されたＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０をＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離するサブ工程と、かかる分離により得られた第１のＧａＮ結晶基板１１１の分離された面を研磨するサブ工程と、を含む。本形態の加工工程により、ＧａＮ種結晶基板１０１の主面１０１ｓの面積より小さな主面１１１ｓを有する第１のＧａＮ結晶基板１１１を少なくとも１つ得ることができる。 (Form 1 of processing step to first GaN crystal substrate)
Referring to FIG. 1C, a form of the processing step to the first GaN crystal substrate includes a sub-process for removing the outer peripheral portions of the GaN seed crystal substrate 101 and the first GaN crystal 110, and The sub-step of separating the removed GaN seed crystal substrate 101 and the first GaN crystal 110 on a plane parallel to the main surface 101s of the GaN seed crystal substrate 101, and the first GaN crystal substrate 111 obtained by such separation. And a sub-step of polishing the separated surface. By the processing step of this embodiment, at least one first GaN crystal substrate 111 having a main surface 111s smaller than the area of the main surface 101s of the GaN seed crystal substrate 101 can be obtained.

本形態の加工工程において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の外周部を除去する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、外周研削、レーザー加工、コアドリル加工、放電加工などの方法が好ましい。 In the processing step of this embodiment, the method for removing the outer peripheral portions of the GaN seed crystal substrate 101 and the first GaN crystal 110 is not particularly limited, but from the viewpoint of easy processing and high processing accuracy, peripheral grinding, laser A method such as machining, core drilling, or electrical discharge machining is preferred.

また、外周部が除去されたＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０をＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、スライス、レーザー加工、放電加工などの方法が好ましい。 Further, there is no particular limitation on the method for separating the GaN seed crystal substrate 101 and the first GaN crystal 110 from which the outer peripheral portion has been removed on a plane parallel to the main surface 101s of the GaN seed crystal substrate 101, but easy processing is possible. From the viewpoint of high machining accuracy, methods such as slicing, laser machining, and electric discharge machining are preferred.

また、分離により得られた第１のＧａＮ結晶基板１１１の分離された面を研磨する方法には、特に制限はないが、加工が容易で加工精度が高く大口径化への対応が容易な観点から、ＣＭＰ（化学機械的研磨）、機械研磨、光照射援用化学研磨法などの方法が好ましい。 The method for polishing the separated surface of the first GaN crystal substrate 111 obtained by the separation is not particularly limited, but it is easy to process, has high processing accuracy, and is easy to cope with a large diameter. Therefore, a method such as CMP (Chemical Mechanical Polishing), mechanical polishing, or light-assisted chemical polishing is preferred.

ここで、ＨＶＰＥ法などの気相法により成長させた第１のＧａＮ結晶１１０は、ＧａＮ種結晶基板１０１の主面１０１ｓから遠い位置になるほど、転位密度が低くなるとともに、外周部に（１０−１１）面および（１１−２２）面の少なくともいずれかのファセット１１０ｆが形成され、外周径が小さくなる。また、外周部に（１０−１０）面のファセット１１０ｅが形成されて、（１０−１０）面にＧａＮ多結晶が成長する。 Here, the dislocation density of the first GaN crystal 110 grown by the vapor phase method such as the HVPE method becomes lower as the position is farther from the main surface 101s of the GaN seed crystal substrate 101, and (10− 11) A facet 110f of at least one of the surface and the (11-22) surface is formed, and the outer diameter is reduced. Further, a (10-10) facet 110e is formed on the outer periphery, and a GaN polycrystal grows on the (10-10) plane.

このため、本形態の加工工程においては、同じ外周径で同じ面積の主面１１１ｓを有する第１のＧａＮ結晶基板１１１を複数枚同時に作製することができるが、それらの第１のＧａＮ結晶基板１１１の主面１１１ｓの面積は、ＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて、小さくなる。また、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板１０１側の結晶成長前半領域１１０ａの少なくともいずれかから加工して得られる第１のＧａＮ結晶基板１１１ａの転位密度に比べて、第１のＧａＮ結晶１１０の中央よりも結晶成長主面１１０ｇ側の結晶成長後半領域１１０ｂから加工して得られる第１のＧａＮ結晶基板１１１ｂの転位密度は低くなる。 For this reason, in the processing step of the present embodiment, a plurality of first GaN crystal substrates 111 having the same outer diameter and the same area of the main surface 111s can be manufactured simultaneously. The area of the main surface 111 s is smaller than the area of the main surface 101 s of the GaN seed crystal substrate 101. Further, the dislocation density of the first GaN crystal substrate 111a obtained by processing from at least one of the crystal growth first half regions 110a closer to the GaN seed crystal substrate 101 than the center of the GaN seed crystal substrate 101 and the first GaN crystal 110. As compared with the above, the dislocation density of the first GaN crystal substrate 111b obtained by processing from the crystal growth latter half region 110b closer to the crystal growth main surface 110g than the center of the first GaN crystal 110 is lower.

（第１のＧａＮ結晶基板への加工工程の形態２）
図２（Ｃ）を参照して、第１のＧａＮ結晶基板への加工工程の別の形態は、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０を、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板１０１側の結晶成長前半領域１１０ａと、第１のＧａＮ結晶１１０の中央よりも結晶成長主面１１０ｇ側の結晶成長後半領域１１０ｂと、に分離するサブ工程と、ＧａＮ種結晶基板１０１および結晶成長前半領域１１０ａの外周部ならびに結晶成長後半領域１１０ｂの外周部を除去するサブ工程と、外周部が除去されたＧａＮ種結晶基板１０１および結晶成長前半領域１１０ａならびに外周部が除去された結晶成長後半領域１１０ｂをそれぞれＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離するサブ工程と、かかる分離により得られた第１のＧａＮ結晶基板１１１の分離された面を研磨するサブ工程と、を含む。本形態の加工工程により、ＧａＮ種結晶基板１０１の主面１０１ｓの面積より小さな主面１１１ｓを有する第１のＧａＮ結晶基板１１１を少なくとも１つ得ることができる。 (Form 2 of processing step to first GaN crystal substrate)
Referring to FIG. 2C, another form of the processing step to the first GaN crystal substrate is that the GaN seed crystal substrate 101 and the first GaN crystal 110 are formed on the main surface 101 s of the GaN seed crystal substrate 101. In parallel planes, the crystal growth front half region 110a closer to the GaN seed crystal substrate 101 than the center of the GaN seed crystal substrate 101 and the first GaN crystal 110, and the crystal growth main surface 110g than the center of the first GaN crystal 110 A sub-process of separating the crystal growth latter half region 110b on the side, a sub-step of removing the outer periphery of the GaN seed crystal substrate 101 and the first half of crystal growth region 110a, and the outer periphery of the crystal growth latter half region 110b, and the outer periphery removed. The GaN seed crystal substrate 1, the crystal growth first half region 110 a, and the crystal growth second half region 110 b from which the outer peripheral portion has been removed are respectively represented by the GaN seed crystal substrate 1. Including a sub-step of separating a plane parallel to the first major surface 101s, and the sub-step of polishing the isolated surface of the first GaN crystal substrate 111 obtained by such separation, the. By the processing step of this embodiment, at least one first GaN crystal substrate 111 having a main surface 111s smaller than the area of the main surface 101s of the GaN seed crystal substrate 101 can be obtained.

本形態の加工工程において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０を、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の結晶成長前半領域１１０ａと第１のＧａＮ結晶１１０の結晶成長後半領域１１０ｂとに分離する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、スライス、レーザー加工、放電加工などの方法が好ましい。 In the processing step of the present embodiment, the GaN seed crystal substrate 101 and the first GaN crystal 110 are changed from the first half region 110a of the GaN seed crystal substrate 101 and the first GaN crystal 110 to the second half of the crystal growth of the first GaN crystal 110. The method for separating the region 110b is not particularly limited, but from the viewpoint of easy processing and high processing accuracy, methods such as slicing, laser processing, and electric discharge processing are preferable.

また、ＧａＮ種結晶基板１０１および結晶成長前半領域１１０ａの外周部ならび結晶成長後半領域１１０ｂの外周部を除去する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、外周研削、レーザー加工、コアドリル加工、放電加工などの方法が好ましい。 The method for removing the outer peripheral portion of the GaN seed crystal substrate 101 and the first half of the crystal growth region 110a and the outer peripheral portion of the second half of the crystal growth region 110b is not particularly limited, but from the viewpoint of easy processing and high processing accuracy, A method such as grinding, laser processing, core drilling, or electrical discharge machining is preferred.

また、外周部が除去されたＧａＮ種結晶基板１０１および結晶成長前半領域１１０ａならびに外周部が除去された結晶成長後半領域１１０ｂを、それぞれＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、スライス、レーザー加工、放電加工などの方法が好ましい。 Further, the GaN seed crystal substrate 101 and the crystal growth first half region 110a from which the outer peripheral portion has been removed and the crystal growth latter half region 110b from which the outer peripheral portion has been removed are separated by planes parallel to the main surface 101s of the GaN seed crystal substrate 101, respectively. The method is not particularly limited, but from the viewpoint of easy processing and high processing accuracy, methods such as slicing, laser processing, and electric discharge processing are preferable.

このため、本形態の加工工程においては、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板１０１側の結晶成長前半領域１１０ａの少なくともいずれかから加工して得られる第１のＧａＮ結晶基板１１１ａの転位密度に比べて、第１のＧａＮ結晶１１０の中央よりも結晶成長主面１１０ｇ側の結晶成長後半領域１１０ｂから加工して得られる第１のＧａＮ結晶基板１１１ｂの転位密度は低くなる。また、第１のＧａＮ結晶基板１１１ａの主面１１１ａｓおよび第１のＧａＮ結晶基板１１１ｂの主面１１１ｂｓの面積はいずれもＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて小さくなる。また、第１のＧａＮ結晶基板１１１ａの主面１１１ａｓの面積は、第１のＧａＮ結晶基板１１１ｂの主面１１１ｂｓの面積に比べて、大きくなる。 For this reason, in the processing step of this embodiment, the first obtained by processing from at least one of the first half regions 110a of the crystal growth on the GaN seed crystal substrate 101 side of the center of the GaN seed crystal substrate 101 and the first GaN crystal 110. Compared to the dislocation density of one GaN crystal substrate 111a, the dislocation of the first GaN crystal substrate 111b obtained by processing from the crystal growth latter region 110b on the crystal growth main surface 110g side of the center of the first GaN crystal 110. Density decreases. Further, the area of the main surface 111as of the first GaN crystal substrate 111a and the area of the main surface 111bs of the first GaN crystal substrate 111b are both smaller than the area of the main surface 101s of the GaN seed crystal substrate 101. The area of the main surface 111as of the first GaN crystal substrate 111a is larger than the area of the main surface 111bs of the first GaN crystal substrate 111b.

（第１のＧａＮ結晶基板への加工工程の形態３）
図３（Ｃ）を参照して、第１のＧａＮ結晶基板への加工工程のさらに別の形態は、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０を、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で、ＧａＮ種結晶基板１０１およびその近傍のＧａＮ種結晶基板近傍領域１１０ｃと、第１のＧａＮ結晶１１０からＧａＮ種結晶基板近傍領域１１０ｃを除いた第１のＧａＮ結晶の結晶成長領域１１０ｄと、に分離するサブ工程と、ＧａＮ種結晶基板１０１およびＧａＮ種結晶基板近傍領域１１０ｃの外周部ならびに結晶成長領域１１０ｄの外周部を除去するサブ工程と、外周部が除去されたＧａＮ種結晶基板１０１およびＧａＮ種結晶基板近傍領域１１０ｃをＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離するサブ工程と、上記少なくともいずれかの分離により得られた第１のＧａＮ結晶基板１１１の分離された面を研磨するサブ工程と、を含む。本形態の加工工程により、ＧａＮ種結晶基板１０１の主面１０１ｓの面積より小さな主面１１１ｓを有する第１のＧａＮ結晶基板１１１を少なくとも１つ得ることができる。 (Form 3 of processing step to first GaN crystal substrate)
Referring to FIG. 3C, still another form of the processing step to the first GaN crystal substrate is that the GaN seed crystal substrate 101 and the first GaN crystal 110 are replaced with the main surface 101 s of the GaN seed crystal substrate 101. GaN seed crystal substrate 101, GaN seed crystal substrate vicinity region 110c in the vicinity thereof, and crystal growth region of the first GaN crystal excluding GaN seed crystal substrate vicinity region 110c from first GaN crystal 110 110d, a sub-process for removing the outer peripheral portion of the GaN seed crystal substrate 101 and the GaN seed crystal substrate vicinity region 110c and the outer peripheral portion of the crystal growth region 110d, and a GaN seed crystal from which the outer peripheral portion has been removed. A sub-process for separating the substrate 101 and the GaN seed crystal substrate vicinity region 110c by a plane parallel to the main surface 101s of the GaN seed crystal substrate 101, and Also includes a sub-step of polishing the isolated surface of the first GaN crystal substrate 111 obtained by any of the separation. By the processing step of this embodiment, at least one first GaN crystal substrate 111 having a main surface 111s smaller than the area of the main surface 101s of the GaN seed crystal substrate 101 can be obtained.

なお、本形態の加工工程におけるＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃは、形態２の加工工程におけるＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の結晶成長前半領域１１０ａに含まれる領域である。 Note that the GaN seed crystal substrate vicinity region 110c of the GaN seed crystal substrate 101 and the first GaN crystal 110 in the processing step of the present embodiment is the crystal of the GaN seed crystal substrate 101 and the first GaN crystal 110 in the processing step of the second embodiment. This is a region included in the first growth region 110a.

本形態の加工工程において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０を、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃと第１のＧａＮ結晶１１０の結晶成長領域１１０ｄとに分離する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、スライス、レーザー加工、放電加工などの方法が好ましい。 In the processing step of this embodiment, the GaN seed crystal substrate 101 and the first GaN crystal 110 are converted into the GaN seed crystal substrate 101 and the first GaN crystal 110 near the GaN seed crystal substrate region 110c and the first GaN crystal 110 crystal. The method for separating the growth region 110d is not particularly limited, but from the viewpoint of easy processing and high processing accuracy, methods such as slicing, laser processing, and electric discharge processing are preferable.

また、ＧａＮ種結晶基板１０１およびＧａＮ種結晶基板近傍領域１１０ｃの外周部ならび結晶成長領域１１０ｄの外周部を除去する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、外周研削、レーザー加工、コアドリル加工、放電加工などの方法が好ましい。 Further, the method for removing the outer peripheral portion of the GaN seed crystal substrate 101 and the GaN seed crystal substrate vicinity region 110c and the outer peripheral portion of the crystal growth region 110d is not particularly limited, but from the viewpoint of easy processing and high processing accuracy, A method such as peripheral grinding, laser machining, core drilling, or electric discharge machining is preferred.

また、外周部が除去された結晶成長領域１１０ｄを、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面で分離する方法には、特に制限はないが、加工が容易で加工精度が高い観点から、スライス、レーザー加工、放電加工などの方法が好ましい。 Further, there is no particular limitation on the method for separating the crystal growth region 110d from which the outer peripheral portion has been removed by a plane parallel to the main surface 101s of the GaN seed crystal substrate 101, but from the viewpoint of easy processing and high processing accuracy. A method such as slicing, laser processing, and electric discharge machining is preferable.

また、上記の少なくともいずれかの分離により得られた第１のＧａＮ結晶基板１１１の分離された面を研磨する方法には、特に制限はないが、加工が容易で加工精度が高く大口径化への対応が容易な観点から、ＣＭＰ（化学機械的研磨）、機械研磨、光照射援用化学研磨法などの方法が好ましい。 There is no particular limitation on the method for polishing the separated surface of the first GaN crystal substrate 111 obtained by at least one of the above separations, but the processing is easy, the processing accuracy is high, and the diameter is increased. From the viewpoint of easy handling of the above, methods such as CMP (Chemical Mechanical Polishing), mechanical polishing, and light-assisted chemical polishing are preferable.

このため、本形態の加工工程においては、ＧａＮ種結晶基板１０１およびＧａＮ種結晶基板近傍領域１１０ｃから加工により得られる第１のＧａＮ結晶基板１１１ｃの転位密度に比べて、第１のＧａＮ結晶１１０の結晶成長領域１１０ｄから加工して得られる第１のＧａＮ結晶基板１１１ｄの転位密度は低くなる。また、第１のＧａＮ結晶基板１１１ｃの主面１１１ｃｓおよび第１のＧａＮ結晶基板１１１ｄの主面１１１ｄｓの面積はいずれもＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて小さくなる。また、第１のＧａＮ結晶基板１１１ｃの主面１１１ｃｓの面積は、第１のＧａＮ結晶基板１１１ｄの主面１１１ｄｓの面積に比べて、大きくなる。 For this reason, in the processing step of this embodiment, the dislocation density of the first GaN crystal 110 is compared with the dislocation density of the first GaN crystal substrate 111c obtained by processing from the GaN seed crystal substrate 101 and the GaN seed crystal substrate vicinity region 110c. The dislocation density of the first GaN crystal substrate 111d obtained by processing from the crystal growth region 110d is low. Further, the area of the main surface 111cs of the first GaN crystal substrate 111c and the area of the main surface 111ds of the first GaN crystal substrate 111d are both smaller than the area of the main surface 101s of the GaN seed crystal substrate 101. The area of the main surface 111cs of the first GaN crystal substrate 111c is larger than the area of the main surface 111ds of the first GaN crystal substrate 111d.

このようにして、少なくとも１つの第１のＧａＮ結晶基板１１１が得られる。こうして得られる第１のＧａＮ結晶基板１１１の主面１１１ｓの面積は、上記の加工工程の形態１〜形態３のいずれの場合においても、ＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて小さくなる。このため、第１のＧａＮ結晶基板上に気相法によりさらに成長させた次のＧａＮ結晶から加工により得られる次のＧａＮ結晶基板は、その主面の面積が第１のＧａＮ結晶基板の主面の面積よりさらに小さくなる。すなわち、得られたＧａＮ結晶基板をそのまま用いてその主面上に気相法により次のＧａＮ結晶を成長させ、ＧａＮ結晶基板およびその主面上に成長させた次のＧａＮ結晶を加工して次のＧａＮ結晶基板を生産するＧａＮ結晶基板の再生産を繰り返すと、得られるＧａＮ結晶基板はその主面の面積が低減する。 In this way, at least one first GaN crystal substrate 111 is obtained. The area of the main surface 111s of the first GaN crystal substrate 111 thus obtained is smaller than the area of the main surface 101s of the GaN seed crystal substrate 101 in any of the first to third processing steps. Become. Therefore, the area of the main surface of the next GaN crystal substrate obtained by processing from the next GaN crystal further grown on the first GaN crystal substrate by the vapor phase method is the main surface of the first GaN crystal substrate. It becomes smaller than the area. That is, using the obtained GaN crystal substrate as it is, the next GaN crystal is grown on the main surface by a vapor phase method, and the next GaN crystal grown on the GaN crystal substrate and the main surface is processed to the next. When the reproduction of the GaN crystal substrate for producing the GaN crystal substrate is repeated, the area of the main surface of the obtained GaN crystal substrate is reduced.

上記のようなＧａＮ結晶基板の再生産において、得られるＧａＮ結晶基板の主面の面積が低減するのを防止するためには、上記の第１のＧａＮ結晶基板の主面の面積を増大させて、主面の面積を増大させたＧａＮ結晶基板の主面上に次のＧａＮ結晶を成長させる必要がある。 In the reproduction of the GaN crystal substrate as described above, in order to prevent the area of the main surface of the obtained GaN crystal substrate from being reduced, the area of the main surface of the first GaN crystal substrate is increased. Then, it is necessary to grow the next GaN crystal on the main surface of the GaN crystal substrate with the area of the main surface increased.

［第２のＧａＮ結晶基板を得る工程］
図１（Ｃ）〜（Ｅ）、図２（Ｃ）〜（Ｅ）、および図３（Ｃ）〜（Ｅ）を参照して、本実施形態のＧａＮ結晶の製造方法は、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃを液相法により成長させることにより、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓに比べて面積が大きな主面１１２ｓを有する第２のＧａＮ結晶基板１１２を得る工程を備える。 [Step of obtaining second GaN crystal substrate]
Referring to FIGS. 1 (C) to (E), FIGS. 2 (C) to (E), and FIGS. 3 (C) to (E), the method for producing a GaN crystal of this embodiment includes the first GaN. By growing the crystal substrates 111, 111a, 111b, and 111c by a liquid phase method, the main surface has a larger area than the main surfaces 111s, 111as, 111bs, and 111cs of the first GaN crystal substrates 111, 111a, 111b, and 111c. A step of obtaining a second GaN crystal substrate 112 having 112s.

第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃを液相法により成長させることにより、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓに垂直な方向の結晶成長速度に比べて、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓに平行な方向の結晶成長速度を高くすることができる。このため、第１のＧａＮ結晶基板の主面の面積を増大させて、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓに比べて面積が大きな主面１１２ｓを有する第２のＧａＮ結晶基板１１２が得られる。 By growing the first GaN crystal substrates 111, 111a, 111b, and 111c by the liquid phase method, the direction perpendicular to the main surfaces 111s, 111as, 111bs, and 111cs of the first GaN crystal substrates 111, 111a, 111b, and 111c The crystal growth rate in the direction parallel to the main surfaces 111s, 111as, 111bs, 111cs of the first GaN crystal substrates 111, 111a, 111b, 111c can be made higher than the crystal growth rate of. Therefore, the main surface of the first GaN crystal substrate is increased, and the main surface has a larger area than the main surfaces 111s, 111as, 111bs, 111cs of the first GaN crystal substrates 111, 111a, 111b, 111c. A second GaN crystal substrate 112 having 112s is obtained.

第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃを成長させる液相法は、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓに垂直な方向の結晶成長速度に比べて、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓに平行な方向の結晶成長速度が高いものであれば特に制限はないが、転位密度が低く結晶性の高いＧａＮ結晶を成長させる観点から、フラックス法、高窒素圧溶液法などが好ましい。また、同様の観点から、液相法に類似した方法であるアモノサーマル法なども好適である。 The liquid phase method for growing the first GaN crystal substrates 111, 111a, 111b, 111c is a crystal in a direction perpendicular to the main surfaces 111s, 111as, 111bs, 111cs of the first GaN crystal substrates 111, 111a, 111b, 111c. There is no particular limitation as long as the crystal growth rate in the direction parallel to the main surfaces 111s, 111as, 111bs, and 111cs of the first GaN crystal substrates 111, 111a, 111b, and 111c is higher than the growth rate. From the viewpoint of growing a GaN crystal having a low density and high crystallinity, a flux method, a high nitrogen pressure solution method, and the like are preferable. From the same viewpoint, an ammonothermal method, which is a method similar to the liquid phase method, is also suitable.

ここで、第１のＧａＮ結晶基板１１１の主面１１１ｓに平行な方向の結晶成長速度を高める観点から、上記のフラックス法において、フラックスは、Ｎａ、Ｌｉ、またはＮａおよびＬｉの混合フラックスなどが好ましく、結晶成長温度は８００℃以上９００℃以下が好ましく、窒素原料ガス圧力は１ＭＰａ以上１０ＭＰａ以下が好ましい。また、同様の観点から、上記の高窒素圧溶液法において、結晶成長温度は１０００℃以上１２００℃以下が好ましく、窒素原料ガス圧力は５０ＭＰａ以上２００ＭＰａ以下が好ましい。 Here, from the viewpoint of increasing the crystal growth rate in the direction parallel to the main surface 111s of the first GaN crystal substrate 111, in the above flux method, the flux is preferably Na, Li, or a mixed flux of Na and Li. The crystal growth temperature is preferably 800 ° C. or higher and 900 ° C. or lower, and the nitrogen source gas pressure is preferably 1 MPa or higher and 10 MPa or lower. From the same viewpoint, in the above high nitrogen pressure solution method, the crystal growth temperature is preferably 1000 ° C. or higher and 1200 ° C. or lower, and the nitrogen source gas pressure is preferably 50 MPa or higher and 200 MPa or lower.

さらに、上記第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃの主面１１１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓの面積以上の主面１１２ｓを有する第２のＧａＮ結晶基板１１２を再生産させることができる観点から、第１のＧａＮ結晶基板１１１，１１１ａ，１１１ｂ，１１１ｃを成長させた第２のＧａＮ結晶基板１１２の主面１１２ｓの面積は、ＧａＮ種結晶基板１０１の主面１０１ｓの面積以上であることが好ましい。 Further, the second GaN crystal substrate 112 having a main surface 112s having an area larger than the area of the main surfaces 111s, 111as, 111bs, and 111cs of the first GaN crystal substrates 111, 111a, 111b, and 111c can be reproduced. Therefore, the area of the main surface 112s of the second GaN crystal substrate 112 on which the first GaN crystal substrates 111, 111a, 111b, and 111c are grown may be equal to or larger than the area of the main surface 101s of the GaN seed crystal substrate 101. preferable.

ここで、図１（Ｃ）および（Ｄ）を参照して、第１のＧａＮ結晶基板１１１が、上記加工工程の形態１〜形態３において、それぞれ第１のＧａＮ結晶１１０の中央よりも結晶成長主面側の結晶成長後半領域１１０ｂから加工して得られる場合は、そのＧａＮ結晶基板１１１ｂの主面１１１ｂｓの面積は、ＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて、相当に小さくなっている。したがって、このような第１のＧａＮ結晶基板１１１ｂは、ＧａＮ種結晶基板１０１に比べて転位密度が低いが、ＧａＮ種結晶基板の主面の面積以上の主面を有する第２のＧａＮ結晶基板を得るためには第１のＧａＮ結晶基板を液相法により相当成長させる必要がある。 Here, referring to FIGS. 1C and 1D, the first GaN crystal substrate 111 grows more than the center of the first GaN crystal 110 in the first to third processing steps. When obtained by processing from the crystal growth latter half region 110b on the main surface side, the area of the main surface 111bs of the GaN crystal substrate 111b is considerably smaller than the area of the main surface 101s of the GaN seed crystal substrate 101. ing. Therefore, such a first GaN crystal substrate 111b has a dislocation density lower than that of the GaN seed crystal substrate 101, but a second GaN crystal substrate having a main surface larger than the area of the main surface of the GaN seed crystal substrate. In order to obtain this, it is necessary to grow the first GaN crystal substrate considerably by the liquid phase method.

また、図２（Ｃ）および（Ｄ）を参照して、第１のＧａＮ結晶基板１１１が、上記加工工程の形態２において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板側の結晶成長前半領域１１０ａの少なくともいずれかから加工して得られる場合は、ＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて、少し小さくなっている。したがって、このような第１のＧａＮ結晶基板１１１ａは、ＧａＮ種結晶基板１０１に比べて転位密度は同じまたは僅かに低い程度であるが、ＧａＮ種結晶基板の主面の面積以上の主面を有する第２のＧａＮ結晶基板を得るためには第１のＧａＮ結晶基板を液相法により少し成長させれば足りる。 2 (C) and 2 (D), the first GaN crystal substrate 111 is more GaN than the center of the GaN seed crystal substrate 101 and the first GaN crystal 110 in the second embodiment of the processing step. When obtained by processing from at least one of the crystal growth first half regions 110a on the seed crystal substrate side, it is slightly smaller than the area of the main surface 101s of the GaN seed crystal substrate 101. Therefore, such a first GaN crystal substrate 111a has a main surface that is equal to or slightly lower in dislocation density than the GaN seed crystal substrate 101, but has a main surface larger than the area of the main surface of the GaN seed crystal substrate. In order to obtain the second GaN crystal substrate, it is sufficient to grow the first GaN crystal substrate slightly by the liquid phase method.

また、図３（Ｃ）および（Ｄ）を参照して、第１のＧａＮ結晶基板１１１が、上記加工工程の形態３において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃから加工して得られる場合は、ＧａＮ種結晶基板１０１の主面１０１ｓの面積に比べて、少し小さくなっている。したがって、このような第１のＧａＮ結晶基板１１１ｃは、ＧａＮ種結晶基板１０１に比べて転位密度は同程度であるが、ＧａＮ種結晶基板の主面の面積以上の主面を有する第２のＧａＮ結晶基板を得るためには第１のＧａＮ結晶基板を液相法により少し成長させれば足りる。 3C and 3D, the first GaN crystal substrate 111 is the GaN seed crystal substrate of the GaN seed crystal substrate 101 and the first GaN crystal 110 in Embodiment 3 of the processing step. When obtained by processing from the neighboring region 110c, it is slightly smaller than the area of the main surface 101s of the GaN seed crystal substrate 101. Therefore, the first GaN crystal substrate 111c has the same dislocation density as that of the GaN seed crystal substrate 101, but the second GaN having a main surface larger than the area of the main surface of the GaN seed crystal substrate. In order to obtain a crystal substrate, it is sufficient to grow the first GaN crystal substrate slightly by the liquid phase method.

［第２のＧａＮ結晶を成長させる工程］
図１（Ｆ）、図２（Ｆ）および図３（Ｆ）を参照して、本実施形態のＧａＮ結晶の製造方法は、第２のＧａＮ結晶基板１１２の主面１１２ｓ上に第２の気相法により第２のＧａＮ結晶１２０を成長させる工程を備える。第２のＧａＮ結晶基板１１２は、その主面１１２ｓの面積が、第１のＧａＮ結晶基板１１１の主面１１１ｓの面積より大きく、好ましくはＧａＮ種結晶基板１０１の主面１０１ｓの面積以上である。このため、第２のＧａＮ結晶基板１１２の主面１１２ｓ上に第２の気相法により成長させた第２のＧａＮ結晶１２０から加工された次のＧａＮ結晶基板（第３のＧａＮ結晶基板という。以下同じ。）を、その主面の面積の低減を抑制して、生産することができる。このようにして、ＧａＮ結晶基板を、その主面の面積の低減を抑制して、再生産することができる。 [Step of growing second GaN crystal]
With reference to FIGS. 1F, 2F, and 3F, the GaN crystal manufacturing method according to the present embodiment has a second gas on the main surface 112s of the second GaN crystal substrate 112. A step of growing the second GaN crystal 120 by a phase method. The area of the main surface 112 s of the second GaN crystal substrate 112 is larger than the area of the main surface 111 s of the first GaN crystal substrate 111, and preferably larger than the area of the main surface 101 s of the GaN seed crystal substrate 101. Therefore, the next GaN crystal substrate (referred to as a third GaN crystal substrate) processed from the second GaN crystal 120 grown by the second vapor phase method on the main surface 112s of the second GaN crystal substrate 112. The same shall apply hereinafter) can be produced while suppressing the reduction of the area of the main surface. In this way, the GaN crystal substrate can be reproduced while suppressing the reduction of the area of the main surface.

第２の気相法は、転位密度が低く結晶性の高い第２のＧａＮ結晶１２０を成長させる方法であれば特に制限はなく、ＨＶＰＥ法、ＭＯＣＶＤ法、ＭＢＥ法、昇華法などが用いられるが、結晶成長速度が高い観点からＨＶＰＥ法が好適に用いられる。なお、ＨＶＰＥ法などの気相法で成長させた第２のＧａＮ結晶１２０は、ＧａＮ種結晶基板１０１の主面１０１ｓから遠い位置になるほど、転位密度が低くなるとともに、外周部に（１０−１１）面および（１１−２２）面の少なくともいずれかのファセット１１０ｆが形成され、外周径が小さくなる。また、第１のＧａＮ結晶１１０の外周部には（１０−１０）面のファセット１１０ｅも形成されるが、かかる（１０−１０）面にはＧａＮ多結晶が成長しやすい。すなわち、第２の気相法も、上記の点については、第１の気相法と同様である。 The second vapor phase method is not particularly limited as long as the second GaN crystal 120 having low dislocation density and high crystallinity is grown, and HVPE method, MOCVD method, MBE method, sublimation method and the like are used. From the viewpoint of high crystal growth rate, the HVPE method is preferably used. Note that the dislocation density of the second GaN crystal 120 grown by a vapor phase method such as the HVPE method becomes lower as the position is farther from the main surface 101s of the GaN seed crystal substrate 101, and at the outer periphery (10-11). ) Face and / or (11-22) facet 110f is formed, and the outer diameter is reduced. In addition, a (10-10) facet 110e is also formed on the outer periphery of the first GaN crystal 110, and GaN polycrystals are likely to grow on the (10-10) plane. That is, the second gas phase method is the same as the first gas phase method in terms of the above points.

ここで、図１（Ｄ）〜（Ｆ）を参照して、上記加工工程の形態１〜形態３において、それぞれ第１のＧａＮ結晶１１０の中央よりも結晶成長主面側の結晶成長後半領域１１０ｂから加工して得られた第１のＧａＮ結晶基板１１１ｂを液相法により成長させた第２のＧａＮ結晶基板１１２は、ＧａＮ種結晶基板１０１に比べて転位密度が低くなる。このため、かかる第２のＧａＮ結晶基板１１２を用いて、第２のＧａＮ結晶１２０を成長させることにより、転位密度の低いＧａＮ結晶基板を再生産することができる。 Here, with reference to FIGS. 1D to 1F, in the first to third processing steps, the crystal growth latter half region 110b on the crystal growth main surface side from the center of the first GaN crystal 110, respectively. The second GaN crystal substrate 112 obtained by growing the first GaN crystal substrate 111b obtained by processing from the above by the liquid phase method has a dislocation density lower than that of the GaN seed crystal substrate 101. For this reason, a GaN crystal substrate with a low dislocation density can be reproduced by growing the second GaN crystal 120 using the second GaN crystal substrate 112.

また、図２（Ｄ）〜（Ｆ）を参照して、上記加工工程の形態２において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板側の結晶成長前半領域１１０ａから加工して得られた第１のＧａＮ結晶基板１１１ａを液相法により成長させた第２のＧａＮ結晶基板１１２は、ＧａＮ種結晶基板１０１の密度と同じまたは僅かに低い転位密度である。このため、かかる第２のＧａＮ結晶基板１１２を用いて、第２のＧａＮ結晶１２０を成長させることにより、転位密度が同じまたは僅かに低いＧａＮ結晶基板を再生産することができる。 2D to 2F, in the second embodiment of the processing step, the first half region of the crystal growth on the GaN seed crystal substrate side from the center of the GaN seed crystal substrate 101 and the first GaN crystal 110. The second GaN crystal substrate 112 obtained by growing the first GaN crystal substrate 111a obtained by processing from 110a by the liquid phase method has a dislocation density that is the same as or slightly lower than the density of the GaN seed crystal substrate 101. Therefore, by growing the second GaN crystal 120 using the second GaN crystal substrate 112, a GaN crystal substrate having the same or slightly lower dislocation density can be reproduced.

また、図３（Ｄ）〜（Ｆ）を参照して、上記加工工程の形態３において、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃから加工して得られた第１のＧａＮ結晶基板１１１ａを液相法により成長させた第２のＧａＮ結晶基板１１２は、ＧａＮ種結晶基板１０１の密度と同等の転位密度である。このため、かかる第２のＧａＮ結晶基板１１２を用いて、第２のＧａＮ結晶１２０を成長させることにより、転位密度が同等のＧａＮ結晶基板を再生産することができる。 3D to 3F, in the third embodiment of the processing step, the GaN seed crystal substrate 101 and the first GaN crystal 110 are processed from the GaN seed crystal substrate vicinity region 110c. The second GaN crystal substrate 112 obtained by growing the first GaN crystal substrate 111 a by the liquid phase method has a dislocation density equivalent to the density of the GaN seed crystal substrate 101. Therefore, by growing the second GaN crystal 120 using the second GaN crystal substrate 112, a GaN crystal substrate having the same dislocation density can be reproduced.

（実施例１）
１．ＧａＮ種結晶基板の準備
図１（Ａ）を参照して、直径が５５ｍｍで（０００１）面の主面１０１ｓを有し、転位密度（主面における平均の転位密度をいう。以下同じ。）が５×１０⁵ｃｍ^-2で厚さが４００μｍのＧａＮ種結晶基板１０１を準備した。ここで、結晶基板の主面の面方位はＸ線回折により同定し、転位密度はＣＬ（カソードルミネッセンス）により測定した。かかるＧａＮ種結晶基板１０１は、下地基板であるＧａＡｓ基板の（１１１）主面上に、ＨＶＰＥ法により成長させたＧａＮ種結晶を、下地基板の主面に平行な面でスライスして、スライス面を鏡面研磨して得られた。 Example 1
1. Preparation of GaN Seed Crystal Substrate Referring to FIG. 1A, the main surface 101s has a diameter of 55 mm and a (0001) plane, and has a dislocation density (an average dislocation density on the main surface; the same applies hereinafter). A GaN seed crystal substrate 101 having a thickness of 5 × 10 ⁵ cm ⁻² and a thickness of 400 μm was prepared. Here, the plane orientation of the main surface of the crystal substrate was identified by X-ray diffraction, and the dislocation density was measured by CL (cathode luminescence). The GaN seed crystal substrate 101 is obtained by slicing a GaN seed crystal grown by the HVPE method on a (111) main surface of a GaAs substrate that is a base substrate, in a plane parallel to the main surface of the base substrate. Was obtained by mirror polishing.

２．第１のＧａＮ結晶の成長
図１（Ｂ）を参照して、ＧａＮ種結晶基板１０１の主面１０１ｓ上に、ＨＶＰＥ法により、結晶成長温度１１００℃、結晶成長速度３００μｍ／ｈｒで、厚さ５ｍｍの第１のＧａＮ結晶１１０を成長させた。得られた第１のＧａＮ結晶１１０は、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な（０００１）面の結晶成長主面１１０ｇと、結晶成長主面１１０ｇの外周に繋がる（１０−１１）面および（１１−２２）面のファセット１１０ｆと、ファセット１１０ｆの外周に繋がる（１０−１０）面のファセット１１０ｅを有していた。また、ファセット１１０ｅには、ＧａＮ多結晶が成長していた。 2. Growth of First GaN Crystal Referring to FIG. 1B, on the main surface 101s of the GaN seed crystal substrate 101, the crystal growth temperature is 1100 ° C., the crystal growth rate is 300 μm / hr, and the thickness is 5 mm by the HVPE method. The first GaN crystal 110 was grown. The obtained first GaN crystal 110 has a (0001) crystal growth main surface 110g parallel to the main surface 101s of the GaN seed crystal substrate 101 and a (10-11) plane connected to the outer periphery of the crystal growth main surface 110g. And (11-22) facet 110f and (10-10) facet 110e connected to the outer periphery of facet 110f. In addition, GaN polycrystals were grown on the facet 110e.

３．第１のＧａＮ結晶基板の作製
図１（Ｃ）を参照して、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０を、それらの外周部を研削により除去して、直径５０ｍｍの円筒形状に加工した後、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面でスライスして、厚さが５００μｍの第１のＧａＮ結晶基板１１１を６枚得た。これらの第１のＧａＮ結晶基板１１１のスライス面を鏡面研磨して、直径が５０ｍｍで厚さが４００μｍの第１のＧａＮ結晶基板１１１を６枚得た。こうして得られた第１のＧａＮ結晶基板１１１は、以下のＧａＮ結晶基板の再生産用のＧａＮ結晶基板を除き、製品として供される。 3. Production of First GaN Crystal Substrate Referring to FIG. 1 (C), GaN seed crystal substrate 101 and first GaN crystal 110 are removed by grinding their outer peripheral portions and processed into a cylindrical shape with a diameter of 50 mm. After that, the first GaN crystal substrate 111 having a thickness of 500 μm was obtained by slicing with a plane parallel to the main surface 101 s of the GaN seed crystal substrate 101. The sliced surfaces of these first GaN crystal substrates 111 were mirror-polished to obtain six first GaN crystal substrates 111 having a diameter of 50 mm and a thickness of 400 μm. The first GaN crystal substrate 111 thus obtained is provided as a product, except for the following GaN crystal substrate for reproduction of GaN crystal substrates.

４．第２のＧａＮ結晶基板の作製
図１（Ｃ）〜（Ｅ）を参照して、上記６枚の第１のＧａＮ結晶基板１１１の内、ＧａＮ種結晶基板１０１側から６枚目の第１のＧａＮ結晶基板１１１ｂ（かかる第１のＧａＮ結晶基板１１１ｂは、第１のＧａＮ結晶１１０の中央よりも結晶成長主面１１０ｇ側の結晶成長後半領域１１０ｂから上記３．のように作製されたもの）を、Ｎａフラックス法により、Ｇａ：Ｎａのモル比が１：３．７のＧａ−Ｎａ融液を用いて、窒素ガス圧力３．０３９ＭＰａ（３０気圧）、結晶成長温度８５０℃で、第１のＧａＮ結晶基板１１１ｂの主面１１１ｓに方向な方向の結晶成長速度が４０μｍ／ｈｒ、垂直な方向の結晶成長速度が８μｍ／ｈｒで、２００時間成長させることにより、主面の直径を５８ｍｍに増大させた。 4). Fabrication of Second GaN Crystal Substrate Referring to FIGS. 1C to 1E, among the six first GaN crystal substrates 111, the first first GaN crystal substrate 101 from the GaN seed crystal substrate 101 side. A GaN crystal substrate 111b (the first GaN crystal substrate 111b is manufactured as described in 3. above from the crystal growth latter half region 110b closer to the crystal growth main surface 110g than the center of the first GaN crystal 110). The first GaN is grown by Na flux method using a Ga—Na melt with a Ga: Na molar ratio of 1: 3.7 at a nitrogen gas pressure of 3.039 MPa (30 atm) and a crystal growth temperature of 850 ° C. The crystal growth rate in the direction perpendicular to the main surface 111s of the crystal substrate 111b is 40 μm / hr, the crystal growth rate in the direction perpendicular to the crystal growth rate is 8 μm / hr, and the diameter of the main surface is increased to 58 mm by growing for 200 hours. .

次いで、その外周部および主面を研削して、主面上のフラックス成長領域を全て除去した。フラックス法で高速成長させると、Ｃ面上に成長したフラックス成長領域は結晶性が悪化しやすいので、これを除去することが好ましい。 Subsequently, the outer peripheral part and the main surface were ground, and all the flux growth regions on the main surface were removed. When high-speed growth is performed by the flux method, the crystal growth of the flux growth region grown on the C-plane is likely to deteriorate, so it is preferable to remove this.

さらに、主面を鏡面研磨して、主面１１２ｓの直径が５５ｍｍで厚さが３５０μｍの第２のＧａＮ結晶基板１１２を得た。この第２のＧａＮ結晶基板１１２は、ＣＬ（カソードルミネッセンス）法により測定したところ、転位密度が２×１０⁵ｃｍ^-2であり、ＧａＮ種結晶基板の転位密度（５×１０⁵ｃｍ^-2）に比べて、低くなった。フラックス法による横方向成長領域（主面に平行な方向に成長した結晶の領域をいう、以下同じ。）の転位密度は１×１０⁵ｃｍ^-2〜２×１０⁵ｃｍ^-2と種結晶基板の転位密度より若干低くなった。 Further, the main surface was mirror-polished to obtain a second GaN crystal substrate 112 having a main surface 112s having a diameter of 55 mm and a thickness of 350 μm. The second GaN crystal substrate 112 has a dislocation density of 2 × 10 ⁵ cm ^{−2 as} measured by the CL (cathode luminescence) method, and the dislocation density (5 × 10 ⁵ cm ⁻² ) of the GaN seed crystal substrate. Compared to The dislocation density of the laterally grown region by the flux method (referred to as the crystal region grown in the direction parallel to the main surface, hereinafter the same) is 1 × 10 ⁵ cm ⁻² to 2 × 10 ⁵ cm ^{−2, which} is a seed crystal substrate The dislocation density was slightly lower.

５．第２のＧａＮ結晶の成長
図１（Ｆ）を参照して、第２のＧａＮ結晶基板１１２の主面１１２ｓ上にＨＶＰＥ法により、結晶成長温度１１００℃、結晶成長速度３００μｍ／ｈｒで、厚さ５ｍｍの第２のＧａＮ結晶１２０を成長させた。かかる第２のＧａＮ結晶１２０は、上記の第１のＧａＮ結晶１１０と同様の形状および大きさを有していた。ここで、第２のＧａＮ結晶１２０は第２のＧａＮ結晶基板１１２上にＨＶＰＥ法により成長されたものであり、第１のＧａＮ結晶１１０はＧａＮ種結晶基板１０１上にＨＶＰＥ法に成長されたものであり、第２のＧａＮ結晶基板１１２の転位密度（２×１０⁵ｃｍ^-2）はＧａＮ種結晶基板１０１の転位密度（５×１０⁵ｃｍ^-2）に比べて低いことから、第２のＧａＮ結晶の転位密度は第１のＧａＮ結晶の転位密度に比べて低くなる。したがって、第２のＧａＮ結晶を基板に加工することにより、転位密度の低いＧａＮ結晶基板を再生産することができる。 5. Growth of Second GaN Crystal Referring to FIG. 1 (F), the thickness of the main surface 112s of the second GaN crystal substrate 112 is increased by the HVPE method at a crystal growth temperature of 1100 ° C. and a crystal growth rate of 300 μm / hr. A 5 mm second GaN crystal 120 was grown. The second GaN crystal 120 had the same shape and size as the first GaN crystal 110 described above. Here, the second GaN crystal 120 is grown on the second GaN crystal substrate 112 by the HVPE method, and the first GaN crystal 110 is grown on the GaN seed crystal substrate 101 by the HVPE method. Since the dislocation density (2 × 10 ⁵ cm ⁻² ) of the second GaN crystal substrate 112 is lower than the dislocation density (5 × 10 ⁵ cm ⁻² ) of the GaN seed crystal substrate 101, The dislocation density of the GaN crystal is lower than the dislocation density of the first GaN crystal. Therefore, a GaN crystal substrate having a low dislocation density can be reproduced by processing the second GaN crystal into a substrate.

（実施例２）
１．ＧａＮ種結晶基板の準備
図２（Ａ）を参照して、実施例１と同様にして、直径が５５ｍｍで（０００１）面の主面１０１ｓを有し、転位密度が５×１０⁵ｃｍ^-2で厚さが４００μｍのＧａＮ種結晶基板１０１を準備した。 (Example 2)
1. Preparation of GaN Seed Crystal Substrate Referring to FIG. 2A, in the same manner as in Example 1, the main surface 101s has a diameter of 55 mm and a (0001) plane, and the dislocation density is 5 × 10 ⁵ cm ^−2. A GaN seed crystal substrate 101 having a thickness of 400 μm was prepared.

２．第１のＧａＮ結晶の成長
図２（Ｂ）を参照して、実施例１と同様にして、厚さ５ｍｍの第１のＧａＮ結晶１１０を成長させた。得られた第１のＧａＮ結晶１１０は、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な（０００１）面の結晶成長主面１１０ｇと、結晶成長主面１１０ｇの外周に繋がる（１０−１１）面および（１１−２２）面のファセット１１０ｆと、ファセット１１０ｆの外周に繋がる（１０−１０）面のファセット１１０ｅを有していた。また、ファセット１１０ｅには、ＧａＮ多結晶が成長していた。 2. Growth of First GaN Crystal With reference to FIG. 2B, a first GaN crystal 110 having a thickness of 5 mm was grown in the same manner as in Example 1. The obtained first GaN crystal 110 has a (0001) crystal growth main surface 110g parallel to the main surface 101s of the GaN seed crystal substrate 101 and a (10-11) plane connected to the outer periphery of the crystal growth main surface 110g. And (11-22) facet 110f and (10-10) facet 110e connected to the outer periphery of facet 110f. In addition, GaN polycrystals were grown on the facet 110e.

３．第１のＧａＮ結晶基板の作製
図２（Ｃ）を参照して、第１のＧａＮ結晶１１０をその中央を含むＧａＮ種結晶基板１０１の主面１０１ｓに平行な面でスライスして、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の結晶成長前半領域１１０ａと、第１のＧａＮ結晶１１０の結晶成長後半領域１１０ｂとに分離した。 3. Fabrication of First GaN Crystal Substrate With reference to FIG. 2C, the first GaN crystal 110 is sliced along a plane parallel to the main surface 101s of the GaN seed crystal substrate 101 including the center thereof, and a GaN seed crystal is obtained. The substrate 101 and the first GaN crystal 110 were separated into a first growth region 110 a of the first GaN crystal 110 and a second growth region 110 b of the first GaN crystal 110.

次いで、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の結晶成長前半領域１１０ａを、それらの外周部を研削により除去して、直径５４ｍｍの円筒形状に加工した後、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面でスライスして、厚さが５００μｍの第１のＧａＮ結晶基板１１１ａを複数枚得た。これらの第１のＧａＮ結晶基板１１１ａのスライス面を鏡面研磨した。こうして、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の結晶成長前半領域１１０ａから直径が５４ｍｍで厚さが４００μｍの第１のＧａＮ結晶基板１１１ａを複数枚得た。 Next, after the crystal growth first half region 110a of the GaN seed crystal substrate 101 and the first GaN crystal 110 is removed by grinding the outer peripheral portion thereof into a cylindrical shape having a diameter of 54 mm, A plurality of first GaN crystal substrates 111a having a thickness of 500 μm were obtained by slicing along a plane parallel to the plane 101s. The slice surfaces of the first GaN crystal substrate 111a were mirror-polished. In this way, a plurality of first GaN crystal substrates 111a having a diameter of 54 mm and a thickness of 400 μm were obtained from the GaN seed crystal substrate 101 and the first half region 110a of the first GaN crystal 110.

また、第１のＧａＮ結晶１１０の結晶成長後半領域１１０ｂを、その外周部を研削により除去して、直径５０ｍｍの円筒形状に加工した後、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面でスライスして、厚さが５００μｍの第１のＧａＮ結晶基板１１１ｂを複数枚得た。これらの第１のＧａＮ結晶基板１１１ｂのスライス面を鏡面研磨した。こうして、第１のＧａＮ結晶１１０の結晶成長後半領域１１０ｂから直径５０ｍｍで厚さが４００μｍの第１のＧａＮ結晶基板１１１ｂを、それぞれ複数枚得た。こうして得られた第１のＧａＮ結晶基板１１１は、以下のＧａＮ結晶基板の再生産用のＧａＮ結晶基板を除き、製品として供される。 Further, after the outer peripheral portion of the first growth region 110b of the first GaN crystal 110 is removed by grinding and processed into a cylindrical shape with a diameter of 50 mm, the first GaN crystal 110 is processed in a plane parallel to the main surface 101s of the GaN seed crystal substrate 101. A plurality of first GaN crystal substrates 111b having a thickness of 500 μm were obtained by slicing. The sliced surfaces of these first GaN crystal substrates 111b were mirror-polished. In this way, a plurality of first GaN crystal substrates 111b each having a diameter of 50 mm and a thickness of 400 μm were obtained from the crystal growth latter half region 110b of the first GaN crystal 110. The first GaN crystal substrate 111 thus obtained is provided as a product, except for the following GaN crystal substrate for reproduction of GaN crystal substrates.

４．第２のＧａＮ結晶基板の作製
図２（Ｃ）〜（Ｅ）を参照して、上記複数の第１のＧａＮ結晶基板１１１の内、ＧａＮ種結晶基板１０１を含む第１のＧａＮ結晶基板１１１ａ（かかる第１のＧａＮ結晶基板１１１ａは、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板１０１側の結晶成長前半領域１１０ａから上記３．のように作製されたもの）を、Ｎａフラックス法により、Ｇａ：Ｎａのモル比が１：３．７のＧａ−Ｎａ融液を用いて、窒素ガス圧力３．０３９ＭＰａ（３０気圧）、結晶成長温度８５０℃で、第１のＧａＮ結晶基板１１１ａの主面１１１ａｓに方向な方向の結晶成長速度が４０μｍ／ｈｒ、垂直な方向の結晶成長速度が８μｍ／ｈｒで、１００時間成長させることにより、主面の直径を５８ｍｍに増大させた。 4). Production of Second GaN Crystal Substrate Referring to FIGS. 2C to 2E, a first GaN crystal substrate 111a (including a GaN seed crystal substrate 101 among the plurality of first GaN crystal substrates 111). The first GaN crystal substrate 111a is produced as described in 3. above from the crystal growth first half region 110a closer to the GaN seed crystal substrate 101 than the center of the GaN seed crystal substrate 101 and the first GaN crystal 110. Using a Ga-Na melt with a Ga: Na molar ratio of 1: 3.7, a Na gas method, a nitrogen gas pressure of 3.039 MPa (30 atm), a crystal growth temperature of 850 ° C., The crystal growth rate in the direction perpendicular to the main surface 111as of the GaN crystal substrate 111a is 40 μm / hr and the crystal growth rate in the vertical direction is 8 μm / hr. It was increased to 8mm.

次いで、外周部および主面を研削して、主面上のフラックス成長領域を全て除去した。フラックス法で高速成長させると、Ｃ面上に成長したフラックス成長領域は結晶性が悪化しやすいので、これを除去することが好ましい。 Next, the outer peripheral portion and the main surface were ground to remove all the flux growth regions on the main surface. When high-speed growth is performed by the flux method, the crystal growth of the flux growth region grown on the C-plane is likely to deteriorate, so it is preferable to remove this.

さらに主面を鏡面研磨して、主面１１２ｓの直径が５５ｍｍで厚さが３５０μｍの第２のＧａＮ結晶基板１１２を得た。この第２のＧａＮ結晶基板１１２は、ＣＬ（カソードルミネッセンス）法により測定したところ、転位密度が５×１０⁵ｃｍ^-2であり、ＧａＮ種結晶基板の転位密度（５×１０⁵ｃｍ^-2）と同様であった。フラックス法による横方向成長領域の転位密度は３×１０⁵ｃｍ^-2〜５×１０⁵ｃｍ^-2と種結晶基板の転位密度より若干低くなった。 Further, the main surface was mirror-polished to obtain a second GaN crystal substrate 112 having a main surface 112s having a diameter of 55 mm and a thickness of 350 μm. The second GaN crystal substrate 112 has a dislocation density of 5 × 10 ⁵ cm ^{−2 as} measured by the CL (cathode luminescence) method, and the dislocation density (5 × 10 ⁵ cm ⁻² ) of the GaN seed crystal substrate. It was the same. The dislocation density in the lateral growth region by the flux method was 3 × 10 ⁵ cm ^{−2 to} 5 × 10 ⁵ cm ⁻² , which was slightly lower than the dislocation density of the seed crystal substrate.

５．第２のＧａＮ結晶の成長
図２（Ｆ）を参照して、第２のＧａＮ結晶基板１１２の主面１１２ｓ上にＨＶＰＥ法により、実施例１と同様にして、厚さ５ｍｍの第２のＧａＮ結晶１２０を成長させた。かかる第２のＧａＮ結晶１２０は、上記の第１のＧａＮ結晶１１０と同様の形状および大きさを有していた。ここで、第２のＧａＮ結晶１２０は第２のＧａＮ結晶基板１１２上にＨＶＰＥ法により成長されたものであり、第１のＧａＮ結晶１１０はＧａＮ種結晶基板１０１上にＨＶＰＥ法に成長されたものであり、第２のＧａＮ結晶基板１１２の転位密度（５×１０⁵ｃｍ^-2）はＧａＮ種結晶基板１０１の転位密度（５×１０⁵ｃｍ^-2）と同様であるから、第２のＧａＮ結晶の転位密度は第１のＧａＮ結晶の転位密度と同じ程度となる。したがって、第２のＧａＮ結晶を基板に加工することにより、同程度の転位密度を有するＧａＮ結晶基板を再生産することができる。 5. Growth of Second GaN Crystal Referring to FIG. 2F, the second GaN having a thickness of 5 mm is formed on the main surface 112s of the second GaN crystal substrate 112 by the HVPE method in the same manner as in the first embodiment. Crystal 120 was grown. The second GaN crystal 120 had the same shape and size as the first GaN crystal 110 described above. Here, the second GaN crystal 120 is grown on the second GaN crystal substrate 112 by the HVPE method, and the first GaN crystal 110 is grown on the GaN seed crystal substrate 101 by the HVPE method. , and the because the dislocation density of the second GaN crystal substrate ^{^{112 (5 × 10 5 cm -2}} ) is the same as the dislocation density of the GaN seed crystal substrate ^{^{101 (5 × 10 5 cm -2}} ), a second GaN The dislocation density of the crystal is about the same as the dislocation density of the first GaN crystal. Therefore, by processing the second GaN crystal into a substrate, a GaN crystal substrate having a similar dislocation density can be reproduced.

（実施例３）
１．ＧａＮ種結晶基板の準備
図３（Ａ）を参照して、実施例１と同様にして、直径が５５ｍｍで（０００１）面の主面１０１ｓを有し、ＣＬ（カソードルミネッセンス）法により測定した転位密度が５×１０⁵ｃｍ^-2で厚さが４００μｍのＧａＮ種結晶基板１０１を準備した。 (Example 3)
1. Preparation of GaN Seed Crystal Substrate Referring to FIG. 3A, dislocations having a diameter of 55 mm and having a (0001) principal surface 101 s as measured in Example 1 and measured by the CL (cathode luminescence) method A GaN seed crystal substrate 101 having a density of 5 × 10 ⁵ cm ⁻² and a thickness of 400 μm was prepared.

２．第１のＧａＮ結晶の成長
図３（Ｂ）を参照して、実施例１と同様にして、厚さ５ｍｍの第１のＧａＮ結晶１１０を成長させた。得られた第１のＧａＮ結晶１１０は、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な（０００１）面の結晶成長主面１１０ｇと、結晶成長主面１１０ｇの外周に繋がる（１０−１１）面および（１１−２２）面のファセット１１０ｆと、ファセット１１０ｆの外周に繋がる（１０−１０）面のファセット１１０ｅを有していた。また、ファセット１１０ｅには、ＧａＮ多結晶が成長していた。 2. Growth of First GaN Crystal With reference to FIG. 3B, a first GaN crystal 110 having a thickness of 5 mm was grown in the same manner as in Example 1. The obtained first GaN crystal 110 has a (0001) crystal growth main surface 110g parallel to the main surface 101s of the GaN seed crystal substrate 101 and a (10-11) plane connected to the outer periphery of the crystal growth main surface 110g. And (11-22) facet 110f and (10-10) facet 110e connected to the outer periphery of facet 110f. In addition, GaN polycrystals were grown on the facet 110e.

３．第１のＧａＮ結晶基板の作製
図３（Ｃ）を参照して、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０を、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面でスライスして、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃを含む厚さ５００μｍの領域と、第１のＧａＮ結晶１１０からＧａＮ種結晶基板近傍領域１１０ｃを除いた第１のＧａＮ結晶の結晶成長領域１１０ｄと、に分離した。 3. Production of First GaN Crystal Substrate Referring to FIG. 3C, GaN seed crystal substrate 101 and first GaN crystal 110 are sliced along a plane parallel to main surface 101s of GaN seed crystal substrate 101, A region having a thickness of 500 μm including the GaN seed crystal substrate vicinity region 110c of the GaN seed crystal substrate 101 and the first GaN crystal 110, and the first GaN obtained by removing the GaN seed crystal substrate vicinity region 110c from the first GaN crystal 110. The crystal was separated into a crystal growth region 110d.

次いで、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃを含む厚さ５００μｍの領域を、その外周部を研削により除去した後、スライス面を研磨して、主面１１１ｃｓの直径が５４ｍｍで厚さが４００μｍの第１のＧａＮ結晶基板１１１ｃを得た。 Next, after removing the outer peripheral portion of the GaN seed crystal substrate 101 and the first GaN crystal 110 including the GaN seed crystal substrate vicinity region 110c having a thickness of 500 μm by grinding, the slice surface is polished to obtain the main surface A first GaN crystal substrate 111c having a diameter of 111 cs of 54 mm and a thickness of 400 μm was obtained.

また、第１のＧａＮ結晶１１０の結晶成長領域１１０ｄを、その外周部を研削により除去して直径５０ｍｍの円筒形状に加工した後、ＧａＮ種結晶基板１０１の主面１０１ｓに平行な面でスライスして、厚さが５００μｍの第１のＧａＮ結晶基板１１１ｄを複数枚得た。それらの第１のＧａＮ結晶基板１１１ｄのスライス面を鏡面研磨して、主面１１１ｄｓの直径が５０ｍｍで厚さが４００μｍの第１のＧａＮ結晶基板１１１ｄを複数枚得た。こうして得られた第１のＧａＮ結晶基板１１１は、以下のＧａＮ結晶基板の再生産用のＧａＮ結晶基板を除き、製品として供される。 The crystal growth region 110d of the first GaN crystal 110 is removed by grinding the outer peripheral portion thereof into a cylindrical shape with a diameter of 50 mm, and then sliced in a plane parallel to the main surface 101s of the GaN seed crystal substrate 101. Thus, a plurality of first GaN crystal substrates 111d having a thickness of 500 μm were obtained. The slice surfaces of the first GaN crystal substrate 111d were mirror-polished to obtain a plurality of first GaN crystal substrates 111d having a main surface 111ds diameter of 50 mm and a thickness of 400 μm. The first GaN crystal substrate 111 thus obtained is provided as a product, except for the following GaN crystal substrate for reproduction of GaN crystal substrates.

４．第２のＧａＮ結晶基板の作製
図３（Ｃ）〜（Ｅ）を参照して、上記複数の第１のＧａＮ結晶基板１１１の内、ＧａＮ種結晶基板１０１を含む第１のＧａＮ結晶基板１１１ｃ（かかる第１のＧａＮ結晶基板１１１ｃは、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃを含む厚さ５００μｍの領域から上記３．のように作製されたものである。ここで、ＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０のＧａＮ種結晶基板近傍領域１１０ｃを含む厚さ５００μｍの領域は、図２（Ｃ）のＧａＮ種結晶基板１０１および第１のＧａＮ結晶１１０の中央よりもＧａＮ種結晶基板１０１側の結晶成長前半領域１１０ａ内に含まれる。）を、Ｎａフラックス法により、Ｇａ：Ｎａのモル比が１：３．７のＧａ−Ｎａ融液を用いて、窒素ガス圧力３．０３９ＭＰａ（３０気圧）、結晶成長温度８５０℃で、第１のＧａＮ結晶基板１１１ａの主面１１１ａｓに方向な方向の結晶成長速度が４０μｍ／ｈｒ、垂直な方向の結晶成長速度が８μｍ／ｈｒで、１００時間成長させることにより、主面の直径を５８ｍｍに増大させた。次いで、外周部および主面を研削して、主面上のフラックス成長領域を全て除去した。フラックス法で高速成長させると、Ｃ面上に成長したフラックス成長領域は結晶性が悪化しやすいので、これを除去することが好ましい。 4). Fabrication of Second GaN Crystal Substrate With reference to FIGS. 3C to 3E, a first GaN crystal substrate 111c (including a GaN seed crystal substrate 101 among the plurality of first GaN crystal substrates 111). The first GaN crystal substrate 111c is manufactured as described in 3. above from a region having a thickness of 500 μm including the GaN seed crystal substrate vicinity region 110c of the GaN seed crystal substrate 101 and the first GaN crystal 110. Here, the 500 μm thick region including the GaN seed crystal substrate vicinity region 110c of the GaN seed crystal substrate 101 and the first GaN crystal 110 is the GaN seed crystal substrate 101 and the first GaN crystal of FIG. In the crystal growth first half region 110a closer to the GaN seed crystal substrate 101 than the center of 110.), the molar ratio of Ga: Na is 1: 3.7 by the Na flux method. Using a Ga—Na melt, the crystal growth rate in the direction toward the main surface 111as of the first GaN crystal substrate 111a is 40 μm / hr at a nitrogen gas pressure of 3.039 MPa (30 atm), a crystal growth temperature of 850 ° C. The diameter of the main surface was increased to 58 mm by growing for 100 hours at a crystal growth rate of 8 μm / hr in the vertical direction. Next, the outer peripheral portion and the main surface were ground to remove all the flux growth regions on the main surface. When high-speed growth is performed by the flux method, the crystal growth of the flux growth region grown on the C-plane is likely to deteriorate, so it is preferable to remove this.

さらに、主面を鏡面研磨して、主面１１２ｓの直径が５５ｍｍで厚さが３５０μｍの第２のＧａＮ結晶基板１１２を得た。この第２のＧａＮ結晶基板１１２は、ＣＬ（カソードルミネッセンス）法により測定したところ、転位密度が５×１０⁵ｃｍ^-2であり、ＧａＮ種結晶基板の転位密度（５×１０⁵ｃｍ^-2）と同様であった。フラックス法による横方向成長領域の転位密度は３×１０⁵ｃｍ^-2〜５×１０⁵ｃｍ^-2と種結晶基板の転位密度より若干低くなった。 Further, the main surface was mirror-polished to obtain a second GaN crystal substrate 112 having a main surface 112s having a diameter of 55 mm and a thickness of 350 μm. The second GaN crystal substrate 112 has a dislocation density of 5 × 10 ⁵ cm ^{−2 as} measured by the CL (cathode luminescence) method, and the dislocation density (5 × 10 ⁵ cm ⁻² ) of the GaN seed crystal substrate. It was the same. The dislocation density in the lateral growth region by the flux method was 3 × 10 ⁵ cm ^{−2 to} 5 × 10 ⁵ cm ⁻² , which was slightly lower than the dislocation density of the seed crystal substrate.

５．第２のＧａＮ結晶の成長
図３（Ｆ）を参照して、第２のＧａＮ結晶基板１１２の主面１１２ｓ上にＨＶＰＥ法により、実施例１と同様にして、厚さ５ｍｍの第２のＧａＮ結晶１２０を成長させた。かかる第２のＧａＮ結晶１２０は、上記の第１のＧａＮ結晶と同様の形状および大きさを有していた。ここで、第２のＧａＮ結晶１２０は第２のＧａＮ結晶基板１１２上にＨＶＰＥ法により成長されたものであり、第１のＧａＮ結晶１１０はＧａＮ種結晶基板１０１上にＨＶＰＥ法に成長されたものであり、第２のＧａＮ結晶基板１１２の転位密度（５×１０⁵ｃｍ^-2）はＧａＮ種結晶基板１０１の転位密度（５×１０⁵ｃｍ^-2）と同様であるから、第２のＧａＮ結晶の転位密度は第１のＧａＮ結晶の転位密度と同じ程度となる。したがって、第２のＧａＮ結晶を基板に加工することにより、同程度の転位密度を有するＧａＮ結晶基板を再生産することができる。 5. Growth of Second GaN Crystal Referring to FIG. 3F, the second GaN having a thickness of 5 mm is formed on the main surface 112s of the second GaN crystal substrate 112 by the HVPE method in the same manner as in the first embodiment. Crystal 120 was grown. The second GaN crystal 120 had the same shape and size as the first GaN crystal. Here, the second GaN crystal 120 is grown on the second GaN crystal substrate 112 by the HVPE method, and the first GaN crystal 110 is grown on the GaN seed crystal substrate 101 by the HVPE method. , and the because the dislocation density of the second GaN crystal substrate ^{^{112 (5 × 10 5 cm -2}} ) is the same as the dislocation density of the GaN seed crystal substrate ^{^{101 (5 × 10 5 cm -2}} ), a second GaN The dislocation density of the crystal is about the same as the dislocation density of the first GaN crystal. Therefore, by processing the second GaN crystal into a substrate, a GaN crystal substrate having a similar dislocation density can be reproduced.

今回開示された実施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.

１０１ＧａＮ種結晶基板、１０１ｓ，１１１ａｓ，１１１ｂｓ，１１１ｃｓ，１１１ｄｓ，１１１ｓ，１１２ｓ主面、１１０第１のＧａＮ結晶、１１０ａ結晶成長前半領域、１１０ｂ結晶成長後半領域、１１０ｃＧａＮ種結晶基板近傍領域、１１０ｄ結晶成長領域、１１０ｅ，１１０ｆファセット、１１０ｇ結晶成長主面、１１１，１１１ａ，１１１ｂ，１１１ｃ，１１１ｄ第１のＧａＮ結晶基板、１１２第２のＧａＮ結晶基板、１２０第２のＧａＮ結晶。 101 GaN seed crystal substrate, 101s, 111as, 111bs, 111cs, 111ds, 111s, 112s main surface, 110 first GaN crystal, 110a crystal growth first half region, 110b crystal growth latter half region, 110c GaN seed crystal substrate vicinity region, 110d Crystal growth region, 110e, 110f facet, 110g Crystal growth main surface, 111, 111a, 111b, 111c, 111d First GaN crystal substrate, 112 Second GaN crystal substrate, 120 Second GaN crystal.

Claims

Preparing a GaN seed crystal substrate;
Growing a first GaN crystal on the main surface of the GaN seed crystal substrate by a first vapor phase method;
By processing at least one of the GaN seed crystal substrate and the first GaN crystal, at least one first GaN crystal substrate having a principal surface having a smaller area than the principal surface of the GaN seed crystal substrate is obtained. Obtaining a step;
Obtaining a second GaN crystal substrate having a main surface having a larger area than the main surface of the first GaN crystal substrate by growing the first GaN crystal substrate by a liquid phase method;
And a step of growing a second GaN crystal on the main surface of the second GaN crystal substrate by a second vapor phase method.

The GaN crystal growth method according to claim 1, wherein an area of the main surface of the second GaN crystal substrate is equal to or larger than an area of the main surface of the GaN seed crystal substrate.

3. The method for growing a GaN crystal according to claim 1, wherein the first GaN crystal substrate is obtained by processing a crystal growth latter half region closer to the crystal growth main surface than the center of the first GaN crystal. .

The first GaN crystal substrate is obtained by processing from at least one of the GaN seed crystal substrate and the first half region of crystal growth closer to the GaN seed crystal substrate than the center of the first GaN crystal. The method for growing a GaN crystal according to claim 2.