JP6347354B2 - RAMO4 board - Google Patents
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Description
本発明はＲＡＭＯ４基板に関する。 The present invention relates to a RAMO 4 substrate.
ＳｃＡｌＭｇＯ４基板は、ＧａＮ等の窒化物半導体のエピタキシャル成長用基板等として用いられている（例えば、特許文献１参照）。図５は、特許文献１に記載された従来のＳｃＡｌＭｇＯ４基板の製造方法を示す例である。図５に示されるように、従来のＳｃＡｌＭｇＯ４基板は、ＳｃＡｌＭｇＯ４バルク材料を劈開することにより製造されていた。 The ScAlMgO 4 substrate is used as a substrate for epitaxial growth of a nitride semiconductor such as GaN (see, for example, Patent Document 1). FIG. 5 shows an example of a conventional method for manufacturing a ScAlMgO 4 substrate described in Patent Document 1. As shown in FIG. 5, the conventional ScAlMgO 4 substrate has been manufactured by cleaving the ScAlMgO 4 bulk material.
特許文献１に示されるように、劈開性を有するＳｃＡｌＭｇＯ４は、劈開性を利用して基板を形成しやすい反面、その劈開性が、基板の堅牢性に影響を及ぼすことがある。例えば、ＳｃＡｌＭｇＯ４基板を用いてウェハやデバイスを製造する際、基板の端部（エッジ）にチッピングや欠けが生じることがあり、歩留まりに影響を及ぼすこと等がある。そこで、より堅牢性の高い基板が要求されている。 As shown in Patent Document 1, ScAlMgO 4 having a cleaving property is easy to form a substrate using the cleaving property, but the cleaving property may affect the robustness of the substrate. For example, when a wafer or a device is manufactured using a ScAlMgO 4 substrate, chipping or chipping may occur at the edge (edge) of the substrate, which may affect the yield. Therefore, a substrate having higher robustness is required.
本開示は、一般式ＲＡＭＯ４で表される単結晶体（一般式において、Ｒは、Ｓｃ、Ｉｎ、Ｙ、およびランタノイド系元素からなる群から選択される一つまたは複数の三価の元素を表し、Ａは、Ｆｅ（ＩＩＩ）、Ｇａ、およびＡｌからなる群から選択される一つまたは複数の三価の元素を表し、Ｍは、Ｍｇ、Ｍｎ、Ｆｅ（ＩＩ）、Ｃｏ、Ｃｕ、Ｚｎ、およびＣｄからなる群から選択される一つまたは複数の二価の元素を表す）からなるＲＡＭＯ４基材部を含み、前記ＲＡＭＯ４基材部が、端部にベベル部を有する、ＲＡＭＯ４基板を提供する。 The present disclosure provides a single crystal represented by the general formula RAMO 4 (in the general formula, R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and lanthanoid elements). A represents one or more trivalent elements selected from the group consisting of Fe (III), Ga, and Al, and M represents Mg, Mn, Fe (II), Co, Cu, Zn , and includes a RAMO 4 substrate portion made of representing one or more divalent elements) selected from the group consisting of Cd, the RAMO 4 substrate portion has a bevel portion on the end portion, RAMO 4 Providing a substrate.
本開示によれば、堅牢性の高いＲＡＭＯ４基板を実現できる。 According to the present disclosure, a highly robust RAMO 4 substrate can be realized.
以下、本発明の実施の形態について、図面を参照しながら説明する。実施の形態において、ＲＡＭＯ４基板をＳｃＡｌＭｇＯ４として説明する。また、以下の実施の形態においてＳｃＡｌＭｇＯ４基板をＳｃＡｌＭｇＯ４基材部と同じ意味で用いる場合もある。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiment, the RAMO 4 substrate will be described as ScAlMgO 4 . In the following embodiments, the ScAlMgO 4 substrate may be used in the same meaning as the ScAlMgO 4 base material.
（実施の形態１）
はじめに、本開示に至った知見を説明する。ＳｃＡｌＭｇＯ４単結晶は、岩塩型構造（１１１）面的なＳｃＯ２層と、六方晶（０００１）面的なＡｌＭｇＯ２層とが交互に積層した構造となっている。六方晶（０００１）面的な２層は、ウルツ鉱型構造に比較して平面的になっており、面内の結合と比較して、上下層間の結合は、０．０３ｎｍほど長く、結合の力が弱い。このため、ＳｃＡｌＭｇＯ４単結晶は、（０００１）面で劈開することができる。この特性を利用し、劈開によってバルク材料を分断し、板状態を準備する工程（劈開工程）を行うことができる。
(Embodiment 1)
First, the knowledge that led to the present disclosure will be described. The ScAlMgO 4 single crystal has a structure in which a rock salt structure (111) -plane ScO 2 layer and a hexagonal (0001) -plane AlMgO 2 layer are alternately stacked. The hexagonal (0001) plane two layers are planar compared to the wurtzite structure, and the bond between the upper and lower layers is about 0.03 nm longer than the in-plane bond. The power is weak. For this reason, the ScAlMgO 4 single crystal can be cleaved in the (0001) plane. Utilizing this characteristic, a step of cleaving the bulk material by cleavage and preparing a plate state (cleavage step) can be performed.
しかしながら、上記のＳｃＡｌＭｇＯ４単結晶の劈開に関する性質は劈開工程を容易に実施可能とできる、すなわちＳｃＡｌＭｇＯ４インゴットから劈開を用いてＳｃＡｌＭｇＯ４基板に加工できる反面、従来の加工方法による劈開面の加工を困難にする。ＳｃＡｌＭｇＯ４バルク材料を劈開したときの劈開面（以下「エピタキシャル成長面」とも称する）の平面度測定データを図６に示す。当該データはφ４０ｍｍのＳｃＡｌＭｇＯ４基板の同一平面内で直交するＸＹ軸でレーザー反射式測長機（三鷹光器製ＮＨ−３ＭＡ）を用いて取得したデータである。図６に矢印で示すように、劈開によって形成される劈開面には５００ｎｍ以上の凹凸部が存在する。ＳｃＡｌＭｇＯ４基板を形成する際、劈開時の劈開方向の剥がし力がばらつくことで、同一原子層での劈開が起こらず、結果的に、５００ｎｍ以上の段差からなる凹凸部が生じると考えられる。 However, the above-mentioned properties relating to the cleavage of the ScAlMgO 4 single crystal make it possible to easily carry out the cleavage process, that is, it is possible to process the ScAlMgO 4 substrate from the ScAlMgO 4 ingot using the cleavage, but the processing of the cleavage plane by the conventional processing method is possible. Make it difficult. FIG. 6 shows flatness measurement data of the cleaved surface (hereinafter also referred to as “epitaxial growth surface”) when the ScAlMgO 4 bulk material is cleaved. The data is data obtained by using a laser reflection type length measuring device (NH-3MA manufactured by Mitaka Kogyo Co., Ltd.) with XY axes orthogonal to each other in the same plane of a φ40 mm ScAlMgO 4 substrate. As shown by arrows in FIG. 6, there are uneven portions of 500 nm or more on the cleavage plane formed by cleavage. When the ScAlMgO 4 substrate is formed, the peeling force in the cleavage direction at the time of cleavage varies, so that cleavage in the same atomic layer does not occur, and as a result, an uneven portion having a step of 500 nm or more is generated.
次にＳｃＡｌＭｇＯ４単結晶の（０００１）面（ＳｃＡｌＭｇＯ４基板の劈開面）へのエピタキシャル成長について説明する。エピタキシャル成長面は単一の（０００１）面（劈開面）で構成されてもよい。ただし、エピタキシャル成長面に欠陥や異物などの偶発的な結晶成長の種となる部分が存在すると、エピタキシャル成長面に例えばＭＯＣＶＤ法でＧａＮの気相成長を行う際に、偶発的な結晶成長の種にＧａ原子が集まり、局所的な不均一成長が発生することがある。 Next, the epitaxial growth of the ScAlMgO 4 single crystal on the (0001) plane (the cleavage plane of the ScAlMgO 4 substrate) will be described. The epitaxial growth surface may be constituted by a single (0001) plane (cleavage plane). However, if there is a part of the epitaxial growth surface that becomes a seed of accidental crystal growth such as a defect or a foreign substance, when performing vapor phase growth of GaN on the epitaxial growth surface, for example, by MOCVD, the seed of the accidental crystal growth is Ga. Atoms may collect and local non-uniform growth may occur.
そこで、上記劈開工程で得られたＳｃＡｌＭｇＯ４基板のエピタキシャル成長面を平坦に加工することが求められるが、上述のように、劈開面に生じた５００ｎｍ以上の凹凸を除去するのは容易ではない。特に、ＳｃＡｌＭｇＯ４基板の劈開面の加工時に、劈開で生じた凹凸を除去しようとしても、全体に占める平坦面の割合が大きいと、平坦面を加工する際に、一部の領域（凹凸）に加工負荷が集中しやすくなる。そして、表面ではなく、より表面から深い内部で劈開による割れが発生することがある。新しい凹凸は、割れ部分が除去されることによって形成されると考えられる。また、平坦面の割合が高い場合に、内部で劈開しないような荷重を加えただけでは、劈開工程で生じた凹凸をほとんど除去出来ない。 Therefore, it is required to process the epitaxial growth surface of the ScAlMgO 4 substrate obtained in the cleavage step flatly, but as described above, it is not easy to remove unevenness of 500 nm or more generated on the cleavage surface. In particular, even if an attempt is made to remove the unevenness caused by cleavage when processing the cleaved surface of the ScAlMgO 4 substrate, if the ratio of the flat surface to the whole is large, when processing the flat surface, some regions (unevenness) The processing load is easy to concentrate. Then, cracks due to cleavage may occur not inside the surface but inside deeper from the surface. It is thought that new unevenness | corrugation is formed by removing a crack part. Further, when the ratio of the flat surface is high, the unevenness generated in the cleavage process can hardly be removed only by applying a load that does not cleave inside.
ここで、従来の加工法で劈開面（エピタキシャル成長面）を平坦化したＳｃＡｌＭｇＯ４基板について説明する。一般的に粗研磨加工に用いられる直径２μｍサイズのダイヤモンドスラリー（砥粒）を用い、ＳｃＡｌＭｇＯ４の劈開面をラップ研磨加工した結果を図８に示す。図８は加工した面の平坦度をＸ方向に測定した結果である。図８に示されるように、当該加工を行うと、表面に５００ｎｍ以上の凹凸が発生することがわかる。ラップ研磨加工ではダイヤモンドスラリーがＳｃＡｌＭｇＯ４表面を転がることにより、転がった部分の材料を微小に除去する。しかし、単結晶ＳｃＡｌＭｇＯ４は、多数のＳｃＯ２層とＡｌＭｇＯ２層との積層体であるために、加工力のばらつきにより部分的に深い層で剥がれが発生すると考えられる。そのため、図８に示されるように、５００ｎｍ以上の凹凸が発生したと考察される。つまり、ＳｃＡｌＭｇＯ４の劈開性は、劈開現象を用いてインゴットからある厚みの基板に分断することに対しては非常に有効であるが、ミクロで見ると上述のような凹凸が発生し、外力により、劈開しやすい。そのため、劈開性が基板の表面状態や形状に影響を及ぼすといえる。 Here, the ScAlMgO 4 substrate in which the cleavage plane (epitaxial growth surface) is planarized by a conventional processing method will be described. FIG. 8 shows the result of lapping the cleaved surface of ScAlMgO 4 using a diamond slurry (abrasive grain) having a diameter of 2 μm generally used for rough polishing. FIG. 8 shows the result of measuring the flatness of the processed surface in the X direction. As shown in FIG. 8, it can be seen that when the processing is performed, irregularities of 500 nm or more are generated on the surface. In the lapping process, the diamond slurry rolls on the surface of the ScAlMgO 4 so that the material of the rolled part is removed minutely. However, since the single crystal ScAlMgO 4 is a laminate of a large number of ScO 2 layers and AlMgO 2 layers, it is considered that peeling occurs partially in a deep layer due to variations in processing force. Therefore, as shown in FIG. 8, it is considered that unevenness of 500 nm or more occurred. In other words, the cleavage property of ScAlMgO 4 is very effective for dividing the ingot into a substrate having a certain thickness by using the cleavage phenomenon. Easy to cleave. Therefore, it can be said that the cleavage property affects the surface state and shape of the substrate.
上記現象に対して、本発明者らは鋭意研究し、特殊な加工法により、ＳｃＡｌＭｇＯ４基板に、互いに段差によって分離した劈開面を形成可能であることを見出した。当該加工方法で得られるＳｃＡｌＭｇＯ４基板は、図７に示すように、エピタキシャル成長面２０２に、規則的に分布する複数の劈開面（以下、「微小平面」とも称する）２６０を有する。また、当該エピタキシャル成長面２０２は、５００ｎｍ以上の凹凸を有さない。 With respect to the above phenomenon, the present inventors have intensively studied and found that a cleaved surface separated from each other by a step can be formed on the ScAlMgO 4 substrate by a special processing method. As shown in FIG. 7, the ScAlMgO 4 substrate obtained by this processing method has a plurality of regularly cleaved surfaces (hereinafter also referred to as “microplanes”) 260 on the epitaxial growth surface 202. In addition, the epitaxial growth surface 202 does not have unevenness of 500 nm or more.
本発明者らは、具体的には、以下に詳述する加工方法（粗凹凸形成工程および微少凹凸形成工程）を見出した。これが本開示の凹凸除去工程である。具体的には、ＳｃＡｌＭｇＯ４基板のエピタキシャル成長面とする領域全面に一定の高さの凹凸形状を形成する（粗凹凸形成工程）。次いで、段階的に加圧力を小さくしていくことで、加圧力のばらつきの絶対量を小さくして内部での劈開を防止しつつ、全面に形成した一定の高さの凹凸形状を徐々に小さくする（微少凹凸形成工程）。 Specifically, the present inventors have found a processing method (a rough unevenness forming step and a fine unevenness forming step) described in detail below. This is the unevenness removing step of the present disclosure. Specifically, a concavo-convex shape having a certain height is formed over the entire region of the ScAlMgO 4 substrate as an epitaxial growth surface (rough concavo-convex forming step). Next, by gradually reducing the applied pressure, the uneven amount of the constant height formed on the entire surface is gradually reduced while decreasing the absolute amount of applied pressure variation and preventing internal cleavage. (Small unevenness forming step).
粗凹凸形成工程では、連続して表面粗さが５００ｎｍ以下である領域（以下、「平坦部」とも称する）の面積がいずれも１ｍｍ２以下となるように、エピタキシャル成長面とする領域の全面に凹凸形状を分布させる。粗凹凸形成工程で１ｍｍ２より大きい平坦部を形成してしまうと、微少凹凸形成工程において、加工負荷の集中によって内部で劈開し、５００ｎｍよりも大きい凹凸が発生するからである。また、粗凹凸形成工程で形成する複数の凹凸の凸部の高さの差は、±０．５μｍ以下の範囲に収まることが好ましい。高さのばらつきがこの範囲内に入るような、均一な高さの凹凸を全面に形成することで、微少凹凸形成工程によって徐々に凹凸の高さを低くでき、面内に均一な平坦部を形成できる。 In the rough unevenness forming step, unevenness is formed on the entire surface of the region to be the epitaxial growth surface so that the area of the region having a surface roughness of 500 nm or less (hereinafter also referred to as “flat portion”) is 1 mm 2 or less. Distribute the shape. This is because if a flat portion larger than 1 mm 2 is formed in the rough unevenness forming step, the fine unevenness forming step is cleaved inside due to the concentration of processing load, and unevenness larger than 500 nm is generated. Moreover, it is preferable that the difference in height of the convex portions of the plurality of concaves and convexes formed in the rough concave-convex forming step is within a range of ± 0.5 μm or less. By forming unevenness with a uniform height over the entire surface so that the variation in height falls within this range, the height of the unevenness can be gradually lowered by the minute unevenness forming process, and a uniform flat portion is formed in the surface. Can be formed.
具体的には、粗凹凸形成工程において、高さ５００ｎｍ以上の凹凸を、第１砥粒を用いて形成し、微少凹凸形成工程において、高さ５００ｎｍ未満の凹凸を、前記第１砥粒よりも硬度の低い第２砥粒を用いて形成する。 Specifically, in the rough unevenness forming step, the unevenness having a height of 500 nm or more is formed using the first abrasive grains, and in the fine unevenness forming process, the unevenness having a height of less than 500 nm is formed more than the first abrasive grains. It forms using the 2nd abrasive grain with low hardness.
より詳細には、一定の高さの凹凸形状を加工する粗凹凸形成工程では、砥粒サイズの大きいダイヤモンド固定砥粒を用いた研削加工を行う。砥粒サイズとしては♯３００以上♯２００００以下（好ましくは＃６００）のダイヤモンド砥粒を使用する。この範囲のサイズのダイヤモンド砥粒を用いた加工によれば、加工面の凹凸の高さの差を±５μｍ以下の範囲に収められる。また、粗凹凸形成工程における加工条件は、砥石回転数５００ｍｉｎ―１以上５００００ｍｉｎ―１以下（好ましくは１８００ｍｉｎ―１）、ＳｃＡｌＭｇＯ４基板回転数１０ｍｉｎ―１以上３００ｍｉｎ―１以下（好ましくは１００ｍｉｎ―１）、加工速度０．０１μｍ／秒以上１μｍ／秒以下（好ましくは０．３μｍ／秒）、加工除去量１μｍ以上３００μｍ以下（好ましくは２０μｍ）とすることが好ましい。例えば、♯６００のダイヤモンド砥粒を用い、砥石回転数１８００ｍｉｎ―１、ＳｃＡｌＭｇＯ４基板回転数１００ｍｉｎ―１、加工速度０．３μｍ／秒、加工除去量２０μｍで加工すると、エピタキシャル成長面とする領域に１ｍｍ２以上の平坦部（凹凸の高さが５００ｎｍ以下である領域が１ｍｍ２以上連続した箇所）が生じず、規則正しい凹凸形状を形成することが出来る。 In more detail, in the rough uneven | corrugated formation process which processes the uneven | corrugated shape of fixed height, the grinding process using a diamond fixed abrasive grain with a large abrasive grain size is performed. As the abrasive grain size, diamond abrasive grains of # 300 or more and # 20000 or less (preferably # 600) are used. According to processing using diamond abrasive grains having a size in this range, the difference in height of the unevenness on the processed surface can be kept within a range of ± 5 μm or less. The processing conditions in the crude irregularities forming step, the grinding wheel rotational speed 500 min -1 or more 50000Min -1 or less (preferably 1800 min -1), ScAlMgO 4 substrate rotational speed 10min -1 or 300 min -1 or less (preferably 100 min -1) The processing speed is preferably 0.01 μm / second or more and 1 μm / second or less (preferably 0.3 μm / second), and the processing removal amount is 1 μm or more and 300 μm or less (preferably 20 μm). For example, if diamond abrasive grains of # 600 are used and processing is performed at a grinding wheel rotational speed of 1800 min −1 , ScAlMgO 4 substrate rotational speed of 100 min −1 , a processing speed of 0.3 μm / second, and a processing removal amount of 20 μm, the area to be an epitaxial growth surface is 1 mm. Two or more flat portions (a portion where a region having a height of unevenness of 500 nm or less is continuous by 1 mm 2 or more) do not occur, and a regular uneven shape can be formed.
次に粗凹凸形成工程で形成した凹凸を徐々に除去する微少凹凸形成工程を説明する。微少凹凸形成工程において、前記高さ５００ｎｍ以上の凹凸を除去しつつ、高さ５００ｎｍ未満の凹凸を、加圧力を段階的に弱めた研磨により形成する。微少凹凸形成工程では、砥粒としてコロイダルシリカを主成分とするスラリーを用い、回転数１０ｍｉｎ−１以上１０００ｍｉｎ−１以下（好ましくは６０ｍｉｎ−１）、スラリー供給量０．０２ｍｌ／分以上２ｍｌ／分以下（好ましくは０．５ｍｌ／分）、研磨パッドは不織布パッドとすることが好ましい。スラリー供給量は基板面積により量を変える。具体的には、基板面積が大きくなる程スラリー供給量を増やすことが好ましい。凹凸が多い場合、凸部に加工力が選択的に集中しやすい。そこで、加圧量は、微少凹凸形成工程の初期には１００００Ｐａ以上２００００Ｐａ以下の範囲とし、凸部が平坦になってくるにつれて５０００Ｐａ以上１００００Ｐａ未満とし、最終的には１０００Ｐａ以上５０００Ｐａ以下の範囲とすることが好ましい。このように段階的に加圧力を低減することで、内部での劈開を生じさせることなくエピタキシャル成長面とする領域から高さ５００ｎｍ以上の凹凸を除去することが出来る。 Next, the micro unevenness | corrugation formation process which removes the unevenness | corrugation formed at the rough unevenness | corrugation formation process gradually is demonstrated. In the fine unevenness forming step, the unevenness with a height of less than 500 nm is formed by polishing with gradually decreasing pressure while removing the unevenness with a height of 500 nm or more. The fine irregularities forming step, using a slurry composed mainly of colloidal silica as abrasive grains, the rotational speed 10min -1 or more 1000min -1 or less (preferably 60min -1), the slurry supply rate 0.02 ml / min to 2 ml / min In the following (preferably 0.5 ml / min), the polishing pad is preferably a non-woven pad. The amount of slurry supplied varies depending on the substrate area. Specifically, it is preferable to increase the slurry supply amount as the substrate area increases. When there are many irregularities, the processing force tends to concentrate selectively on the convex portions. Therefore, the amount of pressurization is in the range of 10,000 Pa to 20,000 Pa at the beginning of the micro unevenness forming process, and is set to 5000 Pa to less than 10,000 Pa as the convex portion becomes flat, and finally in the range of 1000 Pa to 5000 Pa. It is preferable. By reducing the applied pressure stepwise in this way, it is possible to remove unevenness having a height of 500 nm or more from the region to be the epitaxial growth surface without causing internal cleavage.
実際に、微少凹凸形成工程において、最初に加圧力を１５０００Ｐａで３分間研磨加工を行い、次に加圧力を８０００Ｐａに下げて５分間研磨加工を行い、最後に加圧力を１０００Ｐａに下げて１０分間研磨加工を行った結果を以下に示す。得られたエピタキシャル成長面の１０μｍ角の範囲について、ＡＦＭ（原子間力顕微鏡）によって表面形状測定を行ったところ、１０μｍ角の範囲において高さ５００ｎｍ以上の凹凸は無く、最大高さを示すＲｍａｘが６．４２ｎｍであった。つまり、高さ５０ｎｍ以上の凹凸も観察されなかった。なお、二乗平均平方根粗さを示すＲｑは０．１７９ｎｍであった。さらに当該エピタキシャル成長面について詳細に形状分析を行ったところ、１００μｍ２の微小な領域において、表面粗さＲａが０．１３９ｎｍであり、５０ｎｍ以上の凹凸のない極平滑面が形成できていた。ここで、得られたエピタキシャル成長面の表面粗さＲａは０．０８ｎｍ以上０．５ｎｍ以下であった。なお表面粗さＲａ等は、ＢＲＵＫＥＲ社のＤｉｍｅｎｓｉｏｎ Ｉｃｏｎで、ＩＳＯ１３５６５−１に準拠して測定した。 Actually, in the minute unevenness forming step, first, polishing is performed at 15000 Pa for 3 minutes, then the pressing force is decreased to 8000 Pa, polishing is performed for 5 minutes, and finally the pressing force is decreased to 1000 Pa for 10 minutes. The results of polishing are shown below. When the surface shape was measured with an AFM (Atomic Force Microscope) in the 10 μm square range of the obtained epitaxial growth surface, there was no unevenness with a height of 500 nm or more in the 10 μm square range, and the Rmax indicating the maximum height was 6 .42 nm. That is, irregularities with a height of 50 nm or more were not observed. In addition, Rq which shows a root mean square roughness was 0.179 nm. Further, when the shape analysis was performed in detail on the epitaxial growth surface, the surface roughness Ra was 0.139 nm in a very small region of 100 μm 2 , and an extremely smooth surface having no irregularities of 50 nm or more could be formed. Here, the surface roughness Ra of the obtained epitaxial growth surface was 0.08 nm or more and 0.5 nm or less. The surface roughness Ra and the like were measured with a Dimension Icon from BRUKER in accordance with ISO 13565-1.
以上説明したような加工方法（粗凹凸形成工程および微少凹凸形成工程）によれば、互いに段差によって分離した劈開面を含むエピタキシャル成長面を有する、ＳｃＡｌＭｇＯ４基板が準備される。 According to the processing method as described above (the rough unevenness forming step and the fine unevenness forming step), an ScAlMgO 4 substrate having an epitaxial growth surface including cleavage planes separated by steps is prepared.
上記の特殊な加工法で準備されるＳｃＡｌＭｇＯ４基板１の構造を、より具体的に説明する。図７に示すように、ＳｃＡｌＭｇＯ４基板１は、複数の微小平面２６０を有するエピタキシャル成長面２０２を具備する。図７ＡはＳｃＡｌＭｇＯ４基板の一部のエピタキシャル成長面２０２の平面図であり、図７ＢはＳｃＡｌＭｇＯ４基板の側面から見た模式図である。図７Ａに示されるように、ＳｃＡｌＭｇＯ４基板において、エピタキシャル成長面２０２は、複数の微小平面２６０から構成されている。微小平面２６０は長尺状の形状をしており、互いに平行に規則正しく並んでいる。本開示では、微小平面２６０のＸ方向の幅を微小平面幅２６１、隣接する微小平面間の段差高さを微小平面高さ２６２とする。 The structure of the ScAlMgO 4 substrate 1 prepared by the above special processing method will be described more specifically. As shown in FIG. 7, the ScAlMgO 4 substrate 1 includes an epitaxial growth surface 202 having a plurality of microplanes 260. 7A is a plan view of a portion of the epitaxial growth surface 202 of ScAlMgO 4 substrate, FIG. 7B is a schematic side view of ScAlMgO 4 substrate. As shown in FIG. 7A, in the ScAlMgO 4 substrate, the epitaxial growth surface 202 is composed of a plurality of minute planes 260. The microplanes 260 have a long shape and are regularly arranged in parallel to each other. In the present disclosure, the width in the X direction of the minute plane 260 is defined as the minute plane width 261, and the step height between adjacent minute planes is defined as the minute plane height 262.
また、当該ＳｃＡｌＭｇＯ４基板１では、ＳｃＡｌＭｇＯ４基板１の主面が、微小平面（劈開面）２６０に対してオフ角θを有する。本開示において、ＳｃＡｌＭｇＯ４基板１の主面とは、ＳｃＡｌＭｇＯ４基板１を巨視的に観察したときの、ＳｃＡｌＭｇＯ４基板１のエピタキシャル成長面２０２の表面とする。本実施の形態のＳｃＡｌＭｇＯ４基板１のエピタキシャル成長面２０２の表面は、巨視的には平坦であり、ＳｃＡｌＭｇＯ４基板１の主面は、複数の微小平面（劈開面）２６０の表面側の稜線を含む平面とすることができる。一方、本実施の形態において、オフ角θとは、ＳｃＡｌＭｇＯ４基板１の主面と、互いに分離した微小平面（劈開面）２６０とが成す角度とする。すなわち、エピタキシャル成長面２０２の主面の面方位は、ＳｃＡｌＭｇＯ４の劈開面に対してθ傾いている。また、オフ角θとは、ＳｃＡｌＭｇＯ４基板１の主面とＳｃＡｌＭｇＯ４の（０００１）面とが成す角度と換言することもできる。 Further, in the ScAlMgO 4 substrate 1, the main surface of ScAlMgO 4 substrate 1, having an off-angle θ with respect to infinitesimal plane (cleavage plane) 260. In the present disclosure, and the main surface of ScAlMgO 4 substrate 1, when observing the ScAlMgO 4 substrate 1 macroscopically, the surface of the epitaxial growth surface 202 of ScAlMgO 4 substrate 1. The surface of the epitaxial growth surface 202 of the ScAlMgO 4 substrate 1 of the present embodiment is macroscopically flat, and the main surface of the ScAlMgO 4 substrate 1 includes ridge lines on the surface side of a plurality of microplanes (cleavage surfaces) 260. It can be a plane. On the other hand, in the present embodiment, the off-angle θ is an angle formed by the main surface of the ScAlMgO 4 substrate 1 and a minute plane (cleavage surface) 260 separated from each other. That is, the plane orientation of the main surface of the epitaxial growth surface 202 is inclined by θ with respect to the cleavage plane of ScAlMgO 4 . The off-angle θ can also be restated as an angle formed between the main surface of the ScAlMgO 4 substrate 1 and the (0001) plane of ScAlMgO 4 .
なお、オフ角θは、種基板となるＳｃＡｌＭｇＯ４基板１（ＳｃＡｌＭｇＯ４基材部）上にＩＩＩ族窒化物のｃ面などの極性面を成長させる場合において、種基板（ＳｃＡｌＭｇＯ４基板１）の主面と、エピタキシャル成長面のｃ面などの極性面とがなす角度でもある。ここでは、種基板の主面に対してオフ角を有する面、すなわち微小平面２６０を、ＳｃＡｌＭｇＯ４の単結晶のｃ面（極性面）として説明したが、微小平面２６０が、ＳｃＡｌＭｇＯ４の単結晶のｍ面（非極性面）である場合や、ＳｃＡｌＭｇＯ４の単結晶のａ面（半極性面）である場合においても、オフ角の位置づけは同じである。オフ角の設けられたＳｃＡｌＭｇＯ４基板１は、微視的には、図７Ｂに示すように、複数の微小平面２６０が階段状に連続する。 Note that the off-angle θ is the same as that of the seed substrate (ScAlMgO 4 substrate 1) when a polar surface such as a c-plane of group III nitride is grown on the ScAlMgO 4 substrate 1 (ScAlMgO 4 base material) serving as the seed substrate. It is also an angle formed between the main surface and a polar surface such as the c-plane of the epitaxial growth surface. Here, a surface having an off angle to the main surface of the seed substrate, i.e. a small plane 260 has been described as the c-plane of the single crystal ScAlMgO 4 (polar surface), the micro plane 260 is a single crystal of ScAlMgO 4 The position of the off-angle is the same in the case of the m-plane (nonpolar plane) and the a-plane (semipolar plane) of a single crystal of ScAlMgO 4 . As shown in FIG. 7B, the ScAlMgO 4 substrate 1 provided with the off-angle microscopically has a plurality of minute planes 260 that are continuous in a staircase pattern.
次に、ＳｃＡｌＭｇＯ４基板の端部の形状について説明する。上述のようなエピタキシャル成長面を有する、ＳｃＡｌＭｇＯ４基板では、その劈開しやすさが、基板のエッジ形状にも影響を及ぼす。エッジ形状とは、ＳｃＡｌＭｇＯ４基板の端部の形状、すなわちエピタキシャル成長面２０２より外周側の基板の形状である。本実施の形態において、当該端部は、ＳｃＡｌＭｇＯ４基板に対して角度を成すように形成されており、本開示では、当該領域をベベル部と称する。基板のエッジ形状を作りこむ目的は、ウェハやデバイス製造時のチッピング、カケの防止、エピタキシャル成長時に周辺部で異常成長が起こり環状に盛り上がるクラウンの防止などである。また、表裏の識別を目的とすることもある。しかし、ベベル部を劈開しやすい形状にした場合、劈開によりその形状が変化したり、ベベル部における劈開がエピタキシャル成長面におよび、エピタキシャル成長面の有効面積が減少する問題が発生する。従って、本開示では、下記に示す形状のベベル部を設けることで、劈開性を持つＳｃＡｌＭｇＯ４基板（ＲＡＭＯ４）基板の堅牢性を高め、その破壊を防止することを目的とする。 Next, the shape of the end portion of the ScAlMgO 4 substrate will be described. In the ScAlMgO 4 substrate having the epitaxial growth surface as described above, the ease of cleavage affects the edge shape of the substrate. The edge shape is the shape of the end portion of the ScAlMgO 4 substrate, that is, the shape of the substrate on the outer peripheral side from the epitaxial growth surface 202. In the present embodiment, the end portion is formed to form an angle with respect to the ScAlMgO 4 substrate, and in the present disclosure, the region is referred to as a bevel portion. The purpose of creating the edge shape of the substrate is to prevent chipping and chipping during the manufacture of wafers and devices, and to prevent crowns that grow abnormally at the periphery during epitaxial growth and rise in an annular shape. It may also be used to identify the front and back. However, when the bevel portion has a shape that can be easily cleaved, the shape changes due to cleavage, or the cleavage at the bevel portion extends to the epitaxial growth surface, and the effective area of the epitaxial growth surface decreases. Therefore, an object of the present disclosure is to increase the robustness of the cleaved ScAlMgO 4 substrate (RAMO 4 ) substrate and prevent its destruction by providing a bevel portion having the following shape.
図１に本開示の実施の形態１に係る、ＳｃＡｌＭｇＯ４基板１（基材部）のエピタキシャル成長面より外周に設けられたベベル部の形状を示す。ベベル部は、その表面がＳｃＡｌＭｇＯ４基板１の主面に対して角度θ１を有する第１領域と、第１領域より外周側に位置し、その表面がＳｃＡｌＭｇＯ４基板１の主面に対して角度θ２を有する第２領域と、を含む。第１領域と第２領域とでは、ベベルの角度（ＳｃＡｌＭｇＯ４基板１の主面に対する傾斜角度）が異なり、両者の境界には変局点Ａが存在する。また図１において、ｗ１はベベル領域において第１領域の始点から角度が変化する変局点Ａまでの距離であり、ｗ２は変局点Ａから第２領域の終点、すなわち基板１の側面までの距離である。より正確には、ｗ１は、ＳｃＡｌＭｇＯ４基板１の主面と平行方向における第１領域の長さであり、ｗ２は、ＳｃＡｌＭｇＯ４基板１の主面と平行方向における第２領域の長さである。 FIG. 1 shows the shape of the bevel portion provided on the outer periphery from the epitaxial growth surface of the ScAlMgO 4 substrate 1 (base material portion) according to the first embodiment of the present disclosure. Bevel, the angle the surface a first region having an angle θ1 with respect to the main surface of ScAlMgO 4 substrate 1, located on the outer peripheral side of the first region, the surface to the main surface of ScAlMgO 4 substrate 1 and a second region having θ2. The bevel angle (inclination angle with respect to the main surface of the ScAlMgO 4 substrate 1) differs between the first region and the second region, and an inflection point A exists at the boundary between them. In FIG. 1, w1 is the distance from the start point of the first region to the inflection point A where the angle changes in the bevel region, and w2 is from the inflection point A to the end point of the second region, that is, the side surface of the substrate 1. Distance. More precisely, w1 is the length of the first region in the direction parallel to the main surface of the ScAlMgO 4 substrate 1, and w2 is the length of the second region in the direction parallel to the main surface of the ScAlMgO 4 substrate 1. .
また、図１において、θはＳｃＡｌＭｇＯ４基板１のオフ角を示す。オフ角は、上述したように、ＳｃＡｌＭｇＯ４基板１の主面と、エピタキシャル成長面におけるＳｃＡｌＭｇＯ４の劈開面とが成す角度である。一方、θ１はＳｃＡｌＭｇＯ４基板１の主面と、第１領域の表面とが成す角度であり、θ２はＳｃＡｌＭｇＯ４基板１の主面と、第２領域の表面とが成す角度である。より正確には、ベベル部の各領域とＳｃＡｌＭｇＯ４基板１の主面とがなす角度（θ１およびθ２）は、主面に平行な面とベベル部の各領域の表面とが成す角である。ベベル部における各領域の角度は、ＳｃＡｌＭｇＯ４基板の断面形状等から導き出すことができる。 In FIG. 1, θ represents the off angle of the ScAlMgO 4 substrate 1. As described above, the off-angle is an angle formed between the main surface of the ScAlMgO 4 substrate 1 and the cleavage plane of ScAlMgO 4 on the epitaxial growth surface. On the other hand, θ1 is an angle formed by the main surface of the ScAlMgO 4 substrate 1 and the surface of the first region, and θ2 is an angle formed by the main surface of the ScAlMgO 4 substrate 1 and the surface of the second region. More precisely, the angle (θ1 and θ2) formed by each region of the bevel portion and the main surface of the ScAlMgO 4 substrate 1 is an angle formed by a surface parallel to the main surface and the surface of each region of the bevel portion. The angle of each region in the bevel portion can be derived from the cross-sectional shape of the ScAlMgO 4 substrate.
本実施の形態のように、ＳｃＡｌＭｇＯ４基板１の主面がオフ角θを有する場合、ベベル部は、主面に対する角度がオフ角θより小さい角度θ１である第１領域と、主面に対する角度がオフ角θより大きい角度θ２である第２領域とを有することが好ましい。すなわち、θ、θ１、およびθ２がθ＜θ＜θ２の関係を満たすことが望ましい。ベベル部に、このような第１領域および第２領域が形成されていると、ベベル部における劈開の発生をより防止することが可能であり、ＳｃＡｌＭｇＯ４基板の堅牢性を改善することができる。以下、その理由を説明する。 When the main surface of the ScAlMgO 4 substrate 1 has the off-angle θ as in the present embodiment, the bevel portion includes the first region whose angle θ1 is smaller than the off-angle θ and the angle with respect to the main surface. And the second region having an angle θ2 larger than the off-angle θ. That is, it is desirable that θ, θ1, and θ2 satisfy the relationship θ <θ <θ2. When such a first region and a second region are formed in the bevel portion, it is possible to further prevent cleavage from occurring in the bevel portion, and to improve the robustness of the ScAlMgO 4 substrate. The reason will be described below.
まず、オフ角θが１４ｄｅｇ以上であり、ベベル部の形状が、変局点Ａ（角度の変わる点）を有さない直線状である場合について、図２を用いて説明する。図２Ａはベベル部の表面とＳｃＡｌＭｇＯ４基板１の主面とが成す角度がオフ角θよりも大きい場合である。この場合、ベベル部の表面へ荷重が加えられると、ＳｃＡｌＭｇＯ４は非常に劈開されやすいため、ベベル部の内周側の領域（図２Ａにおける領域Ｂ）において、ベベル部の表面（以下「ベベル面」とも称する）が劈開方向に破壊されることがある。一方、図２Ｂはベベル部の表面と、ＳｃＡｌＭｇＯ４基板１の主面とが成す角度が、オフ角θよりも小さい場合である。この場合、ベベル面へ荷重が加えられると、ベベル部の外周側の領域（図２Ｂにおける領域Ｃ）において、劈開方向にベベル面が破壊されることがある。 First, the case where the off-angle θ is 14 degrees or more and the bevel shape is a straight line having no inflection point A (a point where the angle changes) will be described with reference to FIG. FIG. 2A shows a case where the angle formed by the surface of the bevel portion and the main surface of the ScAlMgO 4 substrate 1 is larger than the off angle θ. In this case, when a load is applied to the surface of the bevel portion, ScAlMgO 4 is very easily cleaved. Therefore, in the region on the inner peripheral side of the bevel portion (region B in FIG. 2A), the surface of the bevel portion (hereinafter “bevel surface”). May also be broken in the cleavage direction. On the other hand, FIG. 2B shows a case where the angle formed by the surface of the bevel portion and the main surface of the ScAlMgO 4 substrate 1 is smaller than the off-angle θ. In this case, when a load is applied to the bevel surface, the bevel surface may be broken in the cleavage direction in the region on the outer peripheral side of the bevel portion (region C in FIG. 2B).
次に、図３を用いて、ベベル部の形成時に生じる負荷と、ベベル部の劈開のし易さとを説明する。図３Ａは、形成するベベル部の表面が、ＳｃＡｌＭｇＯ４基板１の主面と角度θ２を成す場合に、ベベル面の形成時に生じる負荷を説明するための図である。ここでθ２は、オフ角θより大きいものとする。ベベル部は、後述のように、研磨砥石や研磨テープ等で形成されるが、いずれの方法においても、ベベル部を形成するための面には、図３Ａに示すように水平方向に加工負荷Ｆが加わる。そして、ベベル面にはＦ・ｃｏｓθ２の力が加わる。また、ベベル面に加わる力の劈開方向の分力Ｆ１は、下記（１）式で表すことができる。
Ｆ１＝Ｆ・ｃｏｓθ２・ｃｏｓ（θ２−θ） ・・・（１）
つまり、劈開方向が最も劈開しやすいと考えた場合、形成するベベル面の劈開面に対する角度が離れるほど、劈開し難くなる。すなわち、θ２が大きくなるほど、上記（１）式におけるＦ１が小さくなり、劈開し難くなるといえる。この劈開のし難さは、剪断応力と同様の特性と考えた場合、ｓｉｎ（２×（４５ｄｅｇ−（θ２−θ））となる。従って劈開のしやすさは、下記（２）式で表すことができる。
劈開のしやすさ＝ｃｏｓθ２・ｃｏｓ（θ２−θ）・ｓｉｎ（２×（４５ｄｅｇ−（θ２−θ））） ・・・（２）
Next, with reference to FIG. 3, a description will be given of the load generated when the bevel portion is formed and the ease of cleavage of the bevel portion. FIG. 3A is a diagram for explaining a load generated when forming the bevel surface when the surface of the bevel portion to be formed forms an angle θ2 with the main surface of the ScAlMgO 4 substrate 1. Here, θ2 is assumed to be larger than the off-angle θ. As will be described later, the bevel portion is formed with a polishing grindstone, a polishing tape, or the like, but in any method, the surface for forming the bevel portion has a processing load F in the horizontal direction as shown in FIG. 3A. Will be added. A force of F · cos θ2 is applied to the bevel surface. Further, the component force F1 in the cleavage direction of the force applied to the bevel surface can be expressed by the following equation (1).
F1 = F · cos θ2 · cos (θ2−θ) (1)
That is, when it is considered that the cleavage direction is most likely to be cleaved, the more the angle of the formed bevel surface with respect to the cleaved surface is, the more difficult it is to cleave. In other words, it can be said that as θ2 increases, F1 in the above equation (1) decreases and it becomes difficult to cleave. The difficulty of cleavage is sin (2 × (45 deg− (θ2−θ)) when considered to be the same characteristics as shear stress. Therefore, the ease of cleavage is expressed by the following equation (2). be able to.
Ease of cleavage = cos θ2 · cos (θ2−θ) · sin (2 × (45 deg− (θ2−θ))) (2)
一方、図３Ｂに示す図はθがθ１より大きい場合のベベル形状である。ベベルを加工する面には、図３Ｂに示すように水平方向に加工負荷Ｆが加わる。ベベル形状の面にはＦ・ｃｏｓθ１の力が加わる。このベベル形状の面に加わる力の劈開方向の分力Ｆ２は、下記（３）式で表すことができる。
Ｆ２＝Ｆ・ｃｏｓθ１・ｃｏｓ（θ−θ１） ・・・（３）
劈開方向が最も劈開しやすいと考えた場合、形成するベベル面の劈開面に対する角度が離れるほど劈開し難くなる。この劈開のし難さは、剪断応力と同様の特性と考えた場合、ｓｉｎ（２×（４５ｄｅｇ−（θ−θ１）））となる。従って劈開のしやすさは、下記（４）式で表すことができる。
劈開のしやすさ＝ｃｏｓθ１・ｃｏｓ（θ−θ１）・ｓｉｎ（２×（４５ｄｅｇ−（θ−θ１））） ・・・（４）
On the other hand, the diagram shown in FIG. 3B shows a bevel shape when θ is larger than θ1. As shown in FIG. 3B, a processing load F is applied to the surface on which the bevel is processed in the horizontal direction. A force of F · cos θ1 is applied to the bevel-shaped surface. The component force F2 in the cleavage direction of the force applied to the bevel-shaped surface can be expressed by the following equation (3).
F2 = F · cos θ1 · cos (θ−θ1) (3)
When it is considered that the cleavage direction is most likely to be cleaved, the cleavage becomes difficult as the angle of the formed bevel surface with respect to the cleavage surface increases. The difficulty of cleaving is sin (2 × (45 deg− (θ−θ1))) when considering the same characteristics as the shear stress. Therefore, the ease of cleavage can be expressed by the following equation (4).
Ease of cleavage = cos θ1 · cos (θ−θ1) · sin (2 × (45 deg− (θ−θ1))) (4)
ここで、図３Ｃおよび図３Ｄは、劈開のしやすさを示す図であり、上記（３）式および（４）式に基づいて作製した図である。図３Ｃは、オフ角θを３０ｄｅｇとしたときの図であり、図３Ｄは、オフ角θを１４ｄｅｇとしたときの図である。また、これらの図では、値が大きい程、ベベル部において、劈開が生じやすいことを表す。 Here, FIG. 3C and FIG. 3D are diagrams showing the easiness of cleavage, and are diagrams based on the above formulas (3) and (4). 3C is a diagram when the off angle θ is 30 deg, and FIG. 3D is a diagram when the off angle θ is 14 deg. In these figures, the larger the value, the easier the cleavage occurs at the bevel portion.
図３Ｃおよび図３Ｄを参照すると、θ１は小さいほど、θ２は大きいほど、ベベル部において劈開が生じ難くなる。つまり、ベベル部に前述の第１領域（ＳｃＡｌＭｇＯ４基板１の主面に対して角度θ１を有する領域）と、前述の第１領域（ＳｃＡｌＭｇＯ４基板１の主面に対して角度θ２を有する領域）とを形成し、角度θ１およびθ２を適切に設定することで、劈開し難いベベル部を有し、強度を確保したＳｃＡｌＭｇＯ４基板を実現できる。 Referring to FIGS. 3C and 3D, the smaller θ1 is and the larger θ2 is, the less likely it is to cleave at the bevel portion. That is, the first region (region having an angle θ1 with respect to the main surface of the ScAlMgO 4 substrate 1) and the first region (region having an angle θ2 with respect to the main surface of the ScAlMgO 4 substrate 1) in the bevel portion. ) And appropriately setting the angles θ1 and θ2, it is possible to realize a ScAlMgO 4 substrate having a bevel portion that is difficult to cleave and ensuring strength.
ここで、図３Ｃおよび図３Ｄでは、オフ角θ（３０ｄｅｇまたは１４ｄｅｇ）における劈開のしやすさに対して、劈開しやすさが１０％低減した場合の角度をθ１よびθ２として設定している。具体的には、図３Ｃの態様では、θ１を１３ｄｅｇ、θ２を３７ｄｅｇと設定できる。一方、図３Ｄでは、θ１を１ｄｅｇ、θ２を２３ｄｅｇと設定できる。なお、本実施の形態では、オフ角θ（３０ｄｅｇまたは１４ｄｅｇ）における劈開のしやすさを基準に、当該基準値から劈開しやすさが１０％低減するときの角度を、θ１またはθ２とする例を示したが、ベベル部を形成する工程以降に、ベベル部に加わる力に基づき、θ１およびθ２は決定することができる。ベベル部の形成工程以降に、ベベル部に加わる力としては、研磨工程において、研磨パッドからベベル部にかかる力や、基板搬送時にベベル部にかかる力などがある。そこで、これらの力の大きさを勘案して、θ１およびθ２を決定することができる。 Here, in FIGS. 3C and 3D, the angles when the ease of cleavage is reduced by 10% with respect to the ease of cleavage at the off angle θ (30 deg or 14 deg) are set as θ1 and θ2. Specifically, in the aspect of FIG. 3C, θ1 can be set to 13 degrees and θ2 can be set to 37 degrees. On the other hand, in FIG. 3D, θ1 can be set to 1 deg and θ2 can be set to 23 deg. In the present embodiment, an example in which the angle at which the ease of cleavage from the reference value is reduced by 10% from the reference value is θ1 or θ2 with reference to the ease of cleavage at the off angle θ (30 deg or 14 deg). However, θ1 and θ2 can be determined based on the force applied to the bevel after the step of forming the bevel. The force applied to the bevel after the bevel formation process includes a force applied from the polishing pad to the bevel in the polishing process, and a force applied to the bevel during transport of the substrate. Therefore, θ1 and θ2 can be determined in consideration of the magnitude of these forces.
一方、オフ角θと、劈開しやすさとの関係について、説明する。ＳｃＡｌＭｇＯ４基板１のオフ角と、ＳｃＡｌＭｇＯ４基板１の主面に平行方向にかかる力（以下、「剪断力」とも称する）との関係を測定した。まず、図９に示すように、ＳｃＡｌＭｇＯ４基板１上にφ２ｍｍ、長さ４ｍｍのアルミ製のリベット５１を、シアノアクリレートを主成分とする接着剤５２で接着した。そして、ＳｃＡｌＭｇＯ４基板１の主面と平行にリベット５１に荷重を付加し、リベット５１が剥離したときの荷重を測定し、ＳｃＡｌＭｇＯ４基板１の劈開しやすさを評価した。ＳｃＡｌＭｇＯ４基板１の主面と劈開面とがなす角度（オフ角）θが０ｄｅｇ、５ｄｅｇ、１０ｄｅｇ、４５ｄｅｇである基板について、それぞれ測定を行なった結果を図１０に示す。図１０に示すように、オフ角θが大きい程、リベット５１が剥離するまでの力、すなわち剪断力が大きくなり、オフ角θが大きい程、劈開し難くなるといえる。なお、接着剤５２は、リベット５１と接着剤５２との界面で剥離してしまうことや、接着剤５２とＳｃＡｌＭｇＯ４基板１との界面で剥がれてしまうことがないよう、十分接着力が強いものを用いた。 On the other hand, the relationship between the off angle θ and the ease of cleavage will be described. And off-angle of ScAlMgO 4 substrate 1, the force exerted in a direction parallel to the main surface of ScAlMgO 4 substrate 1 (hereinafter, also referred to as "shear force") was measured the relation between the. First, as shown in FIG. 9, an aluminum rivet 51 having a diameter of 2 mm and a length of 4 mm was adhered on a ScAlMgO 4 substrate 1 with an adhesive 52 mainly composed of cyanoacrylate. Then, a load was applied to the rivet 51 in parallel with the main surface of the ScAlMgO 4 substrate 1, the load when the rivet 51 was peeled was measured, and the ease of cleavage of the ScAlMgO 4 substrate 1 was evaluated. FIG. 10 shows the results of measurements performed on the substrates having an angle (off angle) θ between the main surface of the ScAlMgO 4 substrate 1 and the cleavage plane of 0 deg, 5 deg, 10 deg, and 45 deg. As shown in FIG. 10, it can be said that the larger the off angle θ, the greater the force until the rivet 51 peels, that is, the shearing force, and the greater the off angle θ, the more difficult it is to cleave. The adhesive 52 has a sufficiently strong adhesive strength so that it does not peel off at the interface between the rivet 51 and the adhesive 52 or peel off at the interface between the adhesive 52 and the ScAlMgO 4 substrate 1. Was used.
以上のような発明者の鋭意検討の結果、オフ角θとベベル部の第１領域の角度θ１および第２領域の角度θ２の好ましい関係が見出された。すなわち、オフ角θは、０．０９ｄｅｇ以上かつ４５ｄｅｇ以下であり、θ１は０ｄｅｇ超かつθｄｅｇ未満であり、かつθ２はθ超かつθ＋４５ｄｅｇ未満であることが特に好ましい。 As a result of the intensive studies by the inventors as described above, a preferable relationship between the off angle θ, the angle θ1 of the first region of the bevel portion, and the angle θ2 of the second region has been found. That is, it is particularly preferable that the off-angle θ is 0.09 deg or more and 45 deg or less, θ1 is more than 0 deg and less than θ deg, and θ2 is more than θ and less than θ + 45 deg.
なお、ＳｃＡｌＭｇＯ４基板のエピタキシャル成長面を用いてエピタキシャル成長させる場合、ベベル部を有さない基板では、図１１に示すように、エピタキシャル成長膜５３の周辺部で異常成長が起こり、環状に盛り上がる、エッジクラウンと呼ばれる現象が発生することがある。また、フォトレジスト塗布の際にも同様にフォトレジスト５４の周辺部で異常堆積が発生することがある。ベベル部を形成する目的は、前述したように外力を受けた際の劈開を防ぐだけでなく、エッジクラウンの防止にもある。そこで、ベベル部に第１領域および第２領域を設ける場合、エッジクラウンの影響を考慮して、各領域のＳｃＡｌＭｇＯ４基板の主面に平行方向の長さ（図１において、ｗ１およびｗ２で表される長さ）を決めることが好ましい。具体的には、ベベル部の第１領域側、すなわちＳｃＡｌＭｇＯ４基板の内周側では、エッジクラウンの傾斜が緩くなりやすく、ベベル部の第２領域側、すなわちＳｃＡｌＭｇＯ４基板の外周側では、傾斜が急になりやすい。そこで、これらを考慮すると、上述のように図１に示すベベル部における第１領域とＳｃＡｌＭｇＯ４基板の主面とが成す角度θ１より、第２領域とＳｃＡｌＭｇＯ４基板の主面とが成す角度θ２を急に設定することが好ましい。また、第１領域のＳｃＡｌＭｇＯ４基板の主面と平行方向の長さｗ１は、０．１ｍｍ以上かつ５ｍｍ以下であることが好ましく、第２領域のＳｃＡｌＭｇＯ４基板の主面と平行方向の長さｗ２は０．１ｍｍ以上かつ５ｍｍ以下であることが好ましい。なお、ベベル部に生じるエッジクラウンの形状は、エピタキシャル成長工程の条件や、フォトレジスト塗布の条件により異なる。したがって、エッジクラウンの形状に合わせて、ｗ１＜ｗ２、ｗ１＝ｗ２、ｗ１＞ｗ２のいずれかの条件を選択することができる。 When epitaxial growth is performed using the epitaxial growth surface of the ScAlMgO 4 substrate, an abnormal growth occurs in the peripheral portion of the epitaxial growth film 53 on the substrate without the bevel portion, and the edge crown The phenomenon called may occur. Similarly, abnormal deposition may occur in the peripheral portion of the photoresist 54 when the photoresist is applied. The purpose of forming the bevel portion is not only to prevent cleavage when an external force is applied as described above, but also to prevent edge crown. Therefore, when the first region and the second region are provided in the bevel portion, the length in the direction parallel to the main surface of the ScAlMgO 4 substrate in each region (indicated by w1 and w2 in FIG. 1) is taken into consideration. It is preferable to determine the length). Specifically, the first region side of the bevel portion, that is, ScAlMgO 4 inner peripheral side of the substrate, tends loose inclined edge crown, the second region side of the bevel portion, i.e. on the outer peripheral side of ScAlMgO 4 substrate, slope Tends to be sudden. Therefore, considering these, as described above, the angle θ2 formed between the second region and the main surface of the ScAlMgO 4 substrate from the angle θ1 formed between the first region and the main surface of the ScAlMgO 4 substrate in the bevel portion shown in FIG. Is preferably set suddenly. Further, the length w1 in the direction parallel to the main surface of the ScAlMgO 4 substrate in the first region is preferably 0.1 mm or more and 5 mm or less, and the length in the direction parallel to the main surface of the ScAlMgO 4 substrate in the second region. w2 is preferably 0.1 mm or more and 5 mm or less. Note that the shape of the edge crown generated in the bevel portion differs depending on the conditions of the epitaxial growth process and the conditions of the photoresist application. Therefore, any of the conditions of w1 <w2, w1 = w2, and w1> w2 can be selected according to the shape of the edge crown.
上記では、第１領域と第２領域との間に変局点Ａを有するベベル部を説明したが、エピタキシャル成長面とベベル部の第１領域との境界部分や、ベベル部の第１領域と第２領域との境界部分に、研削・研磨・面取りを施し、これらがなめらかに連続性を保つ形状となるようにしてもよい。 In the above description, the bevel portion having the inflection point A between the first region and the second region has been described. However, the boundary portion between the epitaxial growth surface and the first region of the bevel portion, the first region of the bevel portion, and the first region. Grinding, polishing, and chamfering may be performed on the boundary portion between the two regions so that they have a shape that maintains smoothness.
また、ＳｃＡｌＭｇＯ４基板は、裏面（エピタキシャル成長面と反対面）にもベベル部を有してもよい。この場合、表面（エピタキシャル成長面）側と同様の課題が発生する場合には、裏面側のベベル部の形状を、図１に示すベベル部と同様の形状としてもよい。裏面にベベル部を設けることにより、チッピング、カケの防止はもちろん、表裏の識別や、ピンセットを用いて基板をハンドリングする場合のし易さに有効に働く。 Further, the ScAlMgO 4 substrate may have a bevel portion on the back surface (the surface opposite to the epitaxial growth surface). In this case, when a problem similar to that on the front surface (epitaxial growth surface) side occurs, the shape of the bevel portion on the back surface side may be the same shape as the bevel portion shown in FIG. By providing a bevel portion on the back surface, chipping and chipping can be prevented, as well as front and back identification and ease of handling a substrate using tweezers.
次に、上記のような形状を有するベベル部を形成する方法について説明する。ベベル部は、例えば、回転砥石を使用して研摩する方法や、研摩テープを使用して研摩する方法により形成することができる。砥石を使用するベベル研摩方法では、回転するウェハに、回転する砥石を接触させ、ウェハまたは砥石をベベル形状に合わせて高さや角度を変えながら接触させる。砥石を接触させる角度や、高さ、回転数などはＮＣ（数値演算）装置により任意に設定し、プログラム動作により任意に動作可能であるため、所望の形状にベベル部を形成することができる。また、研摩テープを使用するベベル研磨装置は、研磨テープをウェハのベベル部に押し当てる圧力と研磨角度の制御が可能な研磨ヘッドと，研磨テープの送り出し・巻き取り機構部で構成され、ベベルの形状に合わせて研磨ヘッド角度を任意にプログラミングすることが可能である。これにより種々の形状が存在するベベルに対して確実な研磨を可能とし、目的の形状を実現できる。ただし、上述の通り、ＳｃＡｌＭｇＯ４基板は、高い劈開性を有する。このため、ベベル部も、エピタキシャル成長面と同様の方法、すなわち本開示の特殊な加工方法で形成することが好ましい。 Next, a method for forming the bevel portion having the above shape will be described. The bevel portion can be formed by, for example, a method of polishing using a rotating grindstone or a method of polishing using a polishing tape. In the bevel polishing method using a grindstone, the rotating grindstone is brought into contact with the rotating wafer, and the wafer or grindstone is brought into contact with the bevel shape while changing the height and angle. The angle at which the grindstone is brought into contact with, the height, the number of rotations, and the like are arbitrarily set by an NC (numerical calculation) device and can be arbitrarily operated by a program operation, so that the bevel portion can be formed in a desired shape. Also, a bevel polishing apparatus using an abrasive tape is composed of a polishing head capable of controlling the pressure and polishing angle for pressing the polishing tape against the wafer bevel, and a polishing tape feed / rewind mechanism. It is possible to arbitrarily program the polishing head angle according to the shape. Accordingly, it is possible to reliably polish a bevel having various shapes, and to realize a target shape. However, as described above, the ScAlMgO 4 substrate has a high cleavage property. For this reason, it is preferable that the bevel portion is also formed by the same method as the epitaxial growth surface, that is, the special processing method of the present disclosure.
（実施の形態２）
図４に本開示の実施の形態２に係る、ＳｃＡｌＭｇＯ４基板のベベル部の形状を示す。本開示の実施の形態２のＳｃＡｌＭｇＯ４基板１のベベル部は、その表面とＳｃＡｌＭｇＯ４基板１との主面とが成す角度がオフ角θより小さくなる領域、すなわち実施の形態の第１領域に相当する領域が極単区間または近似的には無く、その表面とＳｃＡｌＭｇＯ４基板１との主面とが成す角度がオフ角θより大きくなる領域、すなわち実施の形態の第２領域に相当する領域を主に有する。当該ベベル部では、その表面とＳｃＡｌＭｇＯ４基板１との主面とが成す角度が、θ２１からθ２ｎまで角度が大きくなるように設定されている。つまり、ベベル部の表面とＳｃＡｌＭｇＯ４基板１との主面とが成す角度が段階的に変化している。θ２ｎにおけるｎは、ベベル部表面とＳｃＡｌＭｇＯ４基板１との主面とが成す角度の変化回数、すなわちベベル部の形成時に設定する２以上の自然数であり、ｎを増やすと、ベベル部が滑らかな形状となる。
(Embodiment 2)
FIG. 4 shows the shape of the bevel portion of the ScAlMgO 4 substrate according to the second embodiment of the present disclosure. The bevel portion of the ScAlMgO 4 substrate 1 according to the second embodiment of the present disclosure is in a region where the angle formed between the surface and the main surface of the ScAlMgO 4 substrate 1 is smaller than the off-angle θ, that is, the first region of the embodiment. There is no corresponding region or an approximate region, and the region formed by the surface and the main surface of the ScAlMgO 4 substrate 1 is larger than the off-angle θ, that is, the region corresponding to the second region of the embodiment. It has mainly. In the bevel portion, the angle formed between the surface and the main surface of the ScAlMgO 4 substrate 1 is set so that the angle increases from θ21 to θ2n. That is, the angle formed by the surface of the bevel portion and the main surface of the ScAlMgO 4 substrate 1 changes stepwise. n in θ2n is the number of changes in the angle formed by the surface of the bevel portion and the main surface of the ScAlMgO 4 substrate 1, that is, a natural number of 2 or more set when forming the bevel portion. It becomes a shape.
なお、実施の形態２では実施の形態１の第２領域に相当する領域の角度が、２つ以上の角度となるように設定したが、実施の形態１の第１領域に相当する領域の角度が、２つ以上の角度となるように設定してもよい。また、これらの領域において、角度の変化する境界部分に更に研削・研磨・面取りを施し、なめらかに連続性を保つ形状にするようにしてもよい。 In the second embodiment, the angle of the region corresponding to the second region of the first embodiment is set to be two or more angles, but the angle of the region corresponding to the first region of the first embodiment is set. May be set to have two or more angles. In these regions, the boundary portion where the angle changes may be further ground, polished, and chamfered to form a shape that maintains smoothness.
（他の実施形態）
なお、上述の実施の形態１及び２では、一般式ＲＡＭＯ４で表される単結晶体からなる基板のうち、ＳｃＡｌＭｇＯ４の単結晶体から得られる基板について説明したが、本開示は、これに限定されない。具体的には、本開示の基板は、一般式ＲＡＭＯ４で表されるほぼ単一結晶材料から構成される。上記一般式において、Ｒは、Ｓｃ、Ｉｎ、Ｙ、およびランタノイド系元素（原子番号６７−７１）から選択される一つまたは複数の三価の元素を表し、Ａは、Ｆｅ（ＩＩＩ）、Ｇａ、およびＡｌから選択される一つまたは複数の三価の元素を表し、ＭはＭｇ、Ｍｎ、Ｆｅ（ＩＩ），Ｃｏ，Ｃｕ，Ｚｎ，Ｃｄから選択される一つまたは複数の二価の元素を表す。なお、ほぼ単一結晶材料とは、エピタキシャル成長面を構成するＲＡＭＯ４が９０ａｔｍ％以上含まれ、かつ、任意の結晶軸に注目したとき、エピタキシャル成長面のどの部分においてもその向きが同一であるような結晶質固体をいう。ただし、局所的に結晶軸の向きが変わっているものや、局所的な格子欠陥が含まれるものも、単結晶として扱う。なお、Ｏは酸素である。ただし、上記の通り、ＲはＳｃ、ＡはＡｌ、ＭはＭｇとするのが望ましい。
(Other embodiments)
In the first and second embodiments described above, the substrate obtained from the single crystal of ScAlMgO 4 has been described among the substrates formed of the single crystal represented by the general formula RAMO 4. It is not limited. Specifically, the substrate of the present disclosure is composed of a substantially single crystal material represented by the general formula RAMO 4 . In the above general formula, R represents one or more trivalent elements selected from Sc, In, Y, and a lanthanoid element (atomic number 67-71), and A represents Fe (III), Ga And one or more trivalent elements selected from Al, and M is one or more divalent elements selected from Mg, Mn, Fe (II), Co, Cu, Zn, Cd Represents. Note that the almost single crystal material includes 90 atm% or more of RAMO 4 constituting the epitaxial growth surface, and when attention is paid to an arbitrary crystal axis, the orientation is the same in any part of the epitaxial growth surface. A crystalline solid. However, those in which the orientation of the crystal axis is locally changed and those containing local lattice defects are also treated as single crystals. O is oxygen. However, as described above, it is desirable that R is Sc, A is Al, and M is Mg.
基板上へＭＯＣＶＣ気相成長時でＬＥＤ発光層を成長されＬＥＤ素子を製造するにあたり、本開示に係る基板を利用することで、生産歩留まりを向上させながら、ＬＥＤ素子として発光ムラが発生することを抑制し、さらには輝度の低下を防ぐことが出来る。 When manufacturing an LED device by growing an LED light-emitting layer on a substrate during MOCVC vapor phase growth, using the substrate according to the present disclosure improves the production yield and causes uneven light emission as the LED device. It is possible to suppress and further prevent a decrease in luminance.
１ ＳｃＡｌＭｇＯ４基板
５１ リベット
５２ 接着剤
５３ エピタキシャル成長膜
５４ フォトレジスト
２０２ エピタキシャル成長面
２６０ 微小平面
２６１ 微小平面幅
２６２ 微小平面高さ
1 ScAlMgO 4 Substrate 51 Rivet 52 Adhesive 53 Epitaxial Growth Film 54 Photoresist 202 Epitaxial Growth Surface 260 Minute Plane 261 Minute Plane Width 262 Minute Plane Height
Claims (5)
前記ＲＡＭＯ４基材部は、端部にベベル部を有し、
前記ＲＡＭＯ ４ 基材部の主面は、前記単結晶体の劈開面に対してオフ角θを有し、
前記ベベル部は、前記主面に対して角度θ１を有する第１領域と、前記第１領域より外周側に形成され、かつ前記主面に対して角度θ２を有する第２領域とを含み、
θ、θ１、およびθ２が、θ１＜θ＜θ２の関係を満たす、ＲＡＭＯ４基板。 A single crystal represented by the general formula RAMO 4 (in the general formula, R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and lanthanoid elements; Represents one or more trivalent elements selected from the group consisting of Fe, (III), Ga, and Al, and M represents Mg, Mn, Fe (II), Co, Cu, Zn, and Cd. Comprising a RAMO 4 substrate portion comprising one or more divalent elements selected from the group consisting of:
The RAMO 4 substrate unit may have a bevel portion on the end portion,
The main surface of the RAMO 4 base material portion has an off angle θ with respect to the cleavage plane of the single crystal,
The bevel portion includes a first region having an angle θ1 with respect to the main surface, and a second region having an angle θ2 with respect to the main surface and formed on the outer peripheral side of the first region,
A RAMO 4 substrate in which θ, θ1, and θ2 satisfy the relationship of θ1 <θ <θ2 .
θおよびθ２が、θ２＜θ＋４５ｄｅｇを満たす、
請求項１に記載のＲＡＭＯ４基板。 θ satisfies 0.09 deg ≦ θ ≦ 45 deg, and
θ and θ2 satisfy θ2 <θ + 45 deg.
The RAMO 4 substrate according to claim 1 .
前記第２領域の前記主面と平行方向の長さをｗ２としたとき、
ｗ１は０．１ｍｍ以上かつ５ｍｍ以下であり、かつｗ２は０．１ｍｍ以上かつ５ｍｍ以下である、
請求項１または２に記載のＲＡＭＯ４基板。 The length of the first region in the direction parallel to the main surface is w1,
When the length in the direction parallel to the main surface of the second region is w2,
w1 is 0.1 mm or more and 5 mm or less, and w2 is 0.1 mm or more and 5 mm or less.
The RAMO 4 substrate according to claim 1 or 2 .
請求項１〜４のいずれか一項に記載のＲＡＭＯ４基板。 The single crystal is composed of ScAlMgO 4 .
The RAMO 4 substrate according to any one of claims 1 to 4 .
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