JP7161158B2 - Method for manufacturing diamond substrate layer - Google Patents

Method for manufacturing diamond substrate layer Download PDF

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JP7161158B2
JP7161158B2 JP2018527626A JP2018527626A JP7161158B2 JP 7161158 B2 JP7161158 B2 JP 7161158B2 JP 2018527626 A JP2018527626 A JP 2018527626A JP 2018527626 A JP2018527626 A JP 2018527626A JP 7161158 B2 JP7161158 B2 JP 7161158B2
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diamond substrate
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JPWO2018012529A1 (en
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英雄 會田
聖祐 金
豊 木村
友喜 川又
憲次朗 池尻
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Adamant Namiki Precision Jewel Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02Epitaxial-layer growth
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    • C30CRYSTAL GROWTH
    • C30BSINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02Elements
    • C30B29/04Diamond
    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/08Etching
    • C30B33/10Etching in solutions or melts

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Description

本発明は研削、研磨等の表面加工が行われていない単結晶ダイヤモンド基板に関する。 The present invention relates to a single-crystal diamond substrate that has not undergone surface processing such as grinding or polishing.

従来より、ダイヤモンドはその優れた特性から究極の半導体デバイスとして期待されており、一例として下地基板となるダイヤモンド基板上にn型ダイヤモンド層やp型ダイヤモンド層を積層した構成が提案されている。この様な構成について、積層されるダイヤモンドの品質は、下地基板として用いられるダイヤモンド基板の品質や表面状態に左右される。即ち、半導体デバイスを作製する下地基板には結晶品質だけではなく、下地基板の成長面となる表面について、平坦かつ加工変質層が無いことが求められる。この為、当該基板の表面加工方法として特開平01-062484号公報(以下特許文献1として記載)等に記載のエッチング及び、CMP研磨といった平坦化技術が用いられている。また、当該平坦化前の下地基板については国際公開第2015/046294号(以下特許文献2として記載)等のヘテロエピタキシャル成長を用いた大径化技術が使用されており、当該大径化による量産性の向上及びチップ単価の低下を可能としていた。 Conventionally, diamond has been expected to be the ultimate semiconductor device due to its excellent properties. As an example, a structure in which an n-type diamond layer or a p-type diamond layer is laminated on a diamond substrate serving as a base substrate has been proposed. With such a structure, the quality of the laminated diamond depends on the quality and surface condition of the diamond substrate used as the base substrate. That is, the underlying substrate for fabricating a semiconductor device is required not only to have crystal quality, but also to be flat and free of a work-affected layer with respect to the growth surface of the underlying substrate. For this reason, flattening techniques such as etching and CMP polishing described in Japanese Patent Application Laid-Open No. 01-062484 (hereinafter referred to as Patent Document 1) are used as methods for processing the surface of the substrate. In addition, regarding the underlying substrate before the planarization, a technology for increasing the diameter using heteroepitaxial growth, such as International Publication No. WO 2015/046294 (hereinafter referred to as Patent Document 2), is used, and mass production is possible due to the increase in diameter. It was possible to improve the chip unit price and reduce the chip unit price.

特開平01-062484号公報JP-A-01-062484 国際公開第2015/046294号WO2015/046294

上述した効果を有している一方で近年、特許文献2等により大径化された前記基板について、特許文献1記載の加工方法では結晶表面について気相成長に必要な高精度の表面粗さを付与することができず、当該結晶表面を用いたダイヤの気相成長に際してヒロック(Hillock:微小な突起)の発生を抑制することができないという課題を有している。加えて、他の加工方法についても、古くから宝石加工に用いられてきたレーザー切断やダイヤモンド砥粒を用いた機械研磨となる為、加工面が粗くなると共に、加工変質層を生じてしまう。 While having the above-mentioned effects, in recent years, regarding the substrate, which has been increased in diameter according to Patent Document 2, etc., the processing method described in Patent Document 1 can obtain the high-precision surface roughness necessary for vapor phase growth on the crystal surface. However, there is a problem that it is not possible to suppress the formation of hillocks (microscopic protrusions) during the vapor phase growth of diamond using the crystal surface. In addition, other processing methods, such as laser cutting and mechanical polishing using diamond abrasive grains, which have been used for jewelry processing for a long time, roughen the processed surface and produce a process-affected layer.

上記課題に対し、本願記載の発明では、表面に加工変質層を生じることなく、高精度かつ滑らかな表面粗さを有する単結晶ダイヤモンド基板を用いたダイヤモンド基板層の製造方法の提供を目的としている。
In view of the above problems, the object of the invention described in the present application is to provide a method for manufacturing a diamond substrate layer using a single-crystal diamond substrate having high precision and smooth surface roughness without forming a work-affected layer on the surface. .

上記目的のために本願記載の発明は、単結晶ダイヤモンド基板成長用の下地基板として、MgO単結晶,α-Al,Si,石英,白金,イリジウム,チタン酸ストロンチウム(SrTiO)の何れかを材質とし、表面粗さRaが10nm以下の面を有する下地基板を用意し、下地基板の面上にイリジウム単結晶膜を成膜し、その下地基板を成長炉内に配置し、水素、炭素を含む気体としてメタン/水素ガス流量比0.001%~30%でメタンを成長炉内に導入し、成長炉の炉内圧力を1.3×10Pa~1.3×10Paに保ち、周波数2.45GHz(±50MHz)、或いは915MHz(±50MHz)のマイクロ波を電力100W~60kW投入することによりプラズマを発生させ、そのプラズマによる加熱で温度を700℃~1300℃に保った下地基板片面上に活性種を堆積させて、イリジウム単結晶膜上に単結晶ダイヤモンド基板を30μm以上500μm以下の厚みで気相成長させ、ウェットエッチングで下地基板とイリジウム単結晶膜を除去して、単結晶ダイヤモンド基板の表面及び裏面に加工変質層がなく、裏面を表面粗さRa=10nm以下の面にし、単結晶ダイヤモンド基板の裏面側に再度気相成長を行い、ホモエピタキシャルでダイヤモンド基板層を成長させる単結晶ダイヤモンド基板を用いたダイヤモンド基板層の製造方法としたことをその技術的特徴としている。
For the above purpose, the invention described in the present application uses any of MgO single crystal, α-Al 2 O 3 , Si, quartz, platinum, iridium, strontium titanate (SrTiO 3 ) as a base substrate for growing a single crystal diamond substrate. A base substrate having a surface roughness Ra of 10 nm or less is prepared , an iridium single crystal film is formed on the surface of the base substrate, the base substrate is placed in a growth furnace, and hydrogen, As a gas containing carbon, methane is introduced into the growth furnace at a methane/hydrogen gas flow rate ratio of 0.001% to 30%, and the pressure inside the growth furnace is set to 1.3×10 3 Pa to 1.3×10 5 Pa. , and a microwave with a frequency of 2.45 GHz (±50 MHz) or 915 MHz (±50 MHz) is supplied with power of 100 W to 60 kW to generate plasma, and the temperature is kept at 700 ° C. to 1300 ° C. by heating with the plasma. An active species is deposited on one side of the base substrate, a single crystal diamond substrate is vapor-grown on the iridium single crystal film to a thickness of 30 μm or more and 500 μm or less, and the base substrate and the iridium single crystal film are removed by wet etching, The single-crystal diamond substrate has no work-affected layers on its front and back surfaces, and the back surface has a surface roughness Ra of 10 nm or less. The technical feature of the present invention is that it is a method for manufacturing a diamond substrate layer using a grown single-crystal diamond substrate.

また、本発明第2の態様記載の発明は、当該製造方法について裏面を表面粗さRa5nm以下の面にすることをその技術的特徴としている。
Further, the invention according to the second aspect of the present invention is technically characterized in that the back surface of the manufacturing method has a surface roughness Ra of 5 nm or less.

上述した技術的特徴によって本願記載の発明は、気相成長のみを用いた高精度な育成表面の形成が可能となっている。即ち、従来のヘテロエピタキシャル成長させた単結晶ダイヤモンド基板の成長面は未研磨状態では粗く、従来の加工技術を用いて平坦化する必要がある為に、平坦かつ加工変質層のない面に仕上げることが不可能であった。一方、気相成長後ダイヤモンド層成長用の下地基板から分離された裏面はその育成方法上、高精度かつ滑らかな状態でダイヤモンド層の成長が可能な状態となっている。これに伴い、本願記載の単結晶ダイヤモンド基板を用いたダイヤモンド基板層の製造方法では、当該育成した育成表面を底面とし、前記下地基板から分離された裏面側に再度気相成長を行うことによって表面、裏面の両方を加工変質層のない面にすると共に、当該裏面を用いた気相成長によって研磨加工を施さなくても滑らかな表面粗さを有する単結晶ダイヤモンド基板を提供することが可能となる。より具体的には、当該裏面の状態が表面粗さRa=10nm以下の状態となるように気相成長を行った後、ウェットエッチングで下地基板を除去することで育成表面を底面とし、裏面に気相成長を行うことによって、加工変質層が無く、高精度かつ滑らかな結晶表面を有するホモエピタキシャル用単結晶ダイヤモンド基板を提供することができる。これは、ダイヤモンドに極性が無く、裏面にダイヤモンドを成長させることが可能であることによる効果となっている。また、本発明では上述した表面加工を必要としない為、表面、裏面共に加工変質層を生じることのないホモエピタキシャル用の単結晶ダイヤモンド基板を用いたダイヤモンド気相成長により、前記ヒロックのない高品質な単結晶ダイヤモンド基板を得ることができる。
The technical features described above enable the invention described in the present application to form a highly accurate growth surface using only vapor phase growth. That is, since the growth surface of a conventional heteroepitaxially grown single crystal diamond substrate is rough in an unpolished state and needs to be flattened using a conventional processing technique, it is possible to finish the surface to be flat and free of a work-affected layer. It was impossible. On the other hand, the rear surface separated from the base substrate for diamond layer growth after vapor deposition is in a state where the diamond layer can be grown in a highly accurate and smooth state due to the growth method. Along with this, in the method of manufacturing a diamond substrate layer using a single-crystal diamond substrate described in the present application, the grown surface is used as the bottom surface, and vapor phase growth is performed again on the back surface side separated from the underlying substrate. It is possible to provide a single-crystal diamond substrate that has both the front and back surfaces without a work-affected layer and that has a smooth surface roughness without polishing by means of vapor phase epitaxy using the back surface. Become. More specifically, after vapor phase epitaxy is performed so that the state of the back surface has a surface roughness Ra of 10 nm or less, the underlying substrate is removed by wet etching to make the growing surface the bottom surface and the back surface. By carrying out vapor phase epitaxy, it is possible to provide a homoepitaxial single-crystal diamond substrate having no damaged layer and a highly precise and smooth crystal surface. This is because diamond has no polarity and can be grown on the back surface. In addition, since the above-described surface processing is not required in the present invention, high quality without the hillocks is achieved by diamond vapor phase growth using a homoepitaxial single crystal diamond substrate that does not generate a work-affected layer on both the front and back surfaces. A single crystal diamond substrate can be obtained.

上述した効果に加えて、本発明第2の態様記載の発明により、前記気相成長した裏面の表面粗さを更に向上することができる。即ち、上記気相成長に於いて、一定の値までは下地基板の表面及び成長条件によって表面粗さを制御することが可能となっている。より具体的には、上記ヘテロエピタキシャル成長によって得られた単結晶ダイヤモンドを用いて単結晶ダイヤモンド基板を再度育成する際、育成条件及び育成する厚みによって表面粗さRaを一定値まで滑らかにすることができる。本発明記載の単結晶ダイヤモンド基板は、当該裏面における結晶育成段階で育成する結晶表面の粗さを5nm以下とすることによって前記裏面でホモエピタキシャル成長させる単結晶ダイヤモンドを、結晶性の良い厚膜のダイヤモンド単結晶に成長させることを可能にしている。 In addition to the effects described above, the invention according to the second aspect of the present invention can further improve the surface roughness of the vapor-grown rear surface. That is, in the vapor phase epitaxy, it is possible to control the surface roughness up to a certain value depending on the surface of the underlying substrate and growth conditions. More specifically, when the single crystal diamond substrate obtained by the heteroepitaxial growth is used to grow the single crystal diamond substrate again, the surface roughness Ra can be smoothed to a certain value depending on the growth conditions and the thickness of the growth. . The single-crystal diamond substrate according to the present invention is such that the roughness of the crystal surface grown in the crystal growth stage on the back surface is 5 nm or less, and the single-crystal diamond homoepitaxially grown on the back surface is a thick-film diamond with good crystallinity. It allows the growth of single crystals.

以上述べたように、本願請求項記載の発明を用いることによって表面に加工変質層を生じることなく、高精度かつ滑らかな表面粗さを有する単結晶ダイヤモンド基板を提供することが可能となる。 As described above, by using the invention described in the claims of the present application, it is possible to provide a single-crystal diamond substrate having high precision and smooth surface roughness without forming a work-affected layer on the surface.

本発明の最良の実施形態に於いて用いる単結晶ダイヤモンド基板の製造方法説明図。FIG. 2 is an explanatory diagram of a manufacturing method for a single-crystal diamond substrate used in the best embodiment of the present invention; 図1で製造された単結晶ダイヤモンド基板表面(a)及び裏面(b)のAFM測定画像。AFM measurement images of the front surface (a) and back surface (b) of the single crystal diamond substrate produced in FIG.

以下に、図1、図2を用いて、本発明に於ける最良の実施形態を示す。尚、図中の記号及び部品番号について、同じ部品として機能するものには共通の記号又は番号を付与している。 BEST MODE FOR CARRYING OUT THE INVENTION The best embodiment of the present invention is shown below with reference to FIGS. 1 and 2. FIG. In addition, regarding symbols and part numbers in the drawings, common symbols or numbers are given to parts that function as the same parts.

図1に本実施形態で用いる単結晶ダイヤモンド基板の製造方法説明図を、図2に同基板の基板表面(a)及び裏面(b)に於けるAFM測定画像を、それぞれ示す。尚、育成用ステージ、チャンバー及びターゲットといった育成装置については、図中での記載を省略している。 FIG. 1 shows a diagram for explaining the manufacturing method of the single-crystal diamond substrate used in this embodiment, and FIG. 2 shows AFM measurement images on the front surface (a) and back surface (b) of the same substrate. Note that growth devices such as a growth stage, a chamber, and a target are omitted from the drawing.

図1(a)~(g)から解るように、本実施形態では初めにMgO単結晶からなる下地基板1上にCVD法等を用いて単結晶ダイヤモンド層3を気相成長させており、当該ダイヤモンド層から下地基板等を分離して得られたダイヤモンド基板の裏面を成長層として用いることで、前記高精度な表面粗さを有するダイヤモンド単結晶基板を成長可能なホモエピタキシャル用ダイヤモンド単結晶基板(以下ホモエピ用基板として記載)4を得ることができた。 As can be seen from FIGS. 1(a) to 1(g), in the present embodiment, first, a single-crystal diamond layer 3 is vapor-grown on a base substrate 1 made of MgO single crystal using a CVD method or the like. A homoepitaxial diamond single crystal substrate ( 4, which will be described below as a homo-epi substrate, was obtained.

以下に、詳細な説明を述べる。初めのダイヤモンド層を形成する下地基板1について、本実施形態ではMgO単結晶を使用するが、それ以外の材質としては、酸化アルミニウム(α-Al:サファイア)、Si、石英、白金、イリジウム、チタン酸ストロンチウム(SrTiO)等が挙げられる。これらのうちMgO単結晶基板と酸化アルミニウム(サファイア)単結晶基板は、熱的に極めて安定していると共に、8インチ(約203.2mm)までの直径の基板が出ているため、簡単に入手可能との理由から、前記ホモエピ用基板作成時に用いるダイヤモンド層用の基板として好ましい。A detailed description is given below. In this embodiment, MgO single crystal is used for the underlying substrate 1 on which the initial diamond layer is formed. Iridium, strontium titanate (SrTiO 3 ), and the like are included. Of these, MgO single crystal substrates and aluminum oxide (sapphire) single crystal substrates are extremely stable thermally, and substrates with a diameter of up to 8 inches (approximately 203.2 mm) are available. Because it is possible, it is preferable as a substrate for the diamond layer used when producing the homo-epitaxial substrate.

また、前記下地基板1は、少なくとも片面が鏡面研磨されたものを用いる。これは、後述するダイヤモンド層3の成長工程において、ダイヤモンド層3が鏡面研磨された面側に成長形成される事に起因する。当該鏡面研磨は、少なくとも片面でダイヤモンド層が成長可能な程度まで平滑となるように行われれば良く、目安としては表面粗さRaで10nm以下まで研磨することが好ましい。これは、Raが10nmを超えると、片成長させるダイヤモンド層の品質悪化を招いてしまう為である。尚、当該片面上にはクラックが無いものとする。また、Raの測定は、表面粗さ測定機により行うことができる。当該基板については、必要に応じて両面が鏡面研磨された基板を用いても良く、この場合何れか一方の面をダイヤモンド層の成長面として任意に利用できる。 Further, as the base substrate 1, one having at least one surface mirror-polished is used. This is because the diamond layer 3 is grown on the mirror-polished surface side in the step of growing the diamond layer 3, which will be described later. The mirror polishing should be performed so that at least one side is smooth enough to allow the diamond layer to grow, and as a guideline, polishing to a surface roughness Ra of 10 nm or less is preferable. This is because if Ra exceeds 10 nm, the quality of the single-grown diamond layer is degraded. It is assumed that there are no cracks on the one side. Moreover, the measurement of Ra can be performed with a surface roughness measuring machine. As for the substrate, if necessary, a substrate having both sides mirror-polished may be used, and in this case, either side can be arbitrarily used as the growth surface of the diamond layer.

尚、下地基板1にMgO単結晶基板を用いる場合、ダイヤモンド層の成長面として(001)面を用いることが好ましいが、(001)以外の面も使用可能である。また、ダイヤモンド層用の基板について、平面方向の形状は特に限定されず、例えば円形状や方形でも良い。また、当該基板が円形状の場合は大型化という観点から、直径2インチ(約50.8mm)以上であることが好ましく、3インチ(約76.2mm)以上であることがより好ましく、6インチ(約152.4mm)以上であることが更に好ましい。当該基板について直径の上限値は特に限定されないが、実用上の観点から8インチ以下が好ましい。本願では基板の寸法公差を考慮し、直径2インチに関しては50.8mmの2%に当たる1.0mmを減算した、直径49.8mm以上~50.8mmの範囲も2インチに該当すると定義する。 When an MgO single crystal substrate is used as the base substrate 1, it is preferable to use the (001) plane as the growth plane of the diamond layer, but planes other than the (001) plane can also be used. Further, the shape of the substrate for the diamond layer in the planar direction is not particularly limited, and may be, for example, circular or rectangular. In addition, when the substrate is circular, the diameter is preferably 2 inches (about 50.8 mm) or more, more preferably 3 inches (about 76.2 mm) or more, and 6 inches from the viewpoint of increasing the size. (about 152.4 mm) or more is more preferable. Although the upper limit of the diameter of the substrate is not particularly limited, it is preferably 8 inches or less from a practical viewpoint. In the present application, considering the dimensional tolerance of substrates, the range of 49.8 mm or more to 50.8 mm in diameter is defined as 2 inches by subtracting 1.0 mm, which is 2% of 50.8 mm, from 2 inches in diameter.

上記下地基板1について円形の場合に於けるサイズを規定する一方、当該基板が方形の場合は大型化という観点から、50mm×50mm以上であることが好ましく、75mm×75mm以上であることがより好ましい。また、寸法の上限値は実用上の観点から、200mm×200mm以下が好ましい。従って、ダイヤモンド層用の基板は、少なくとも20cmの表面積を有する。更に、大型化という観点から、1297cmまでの表面積を有することが、より好ましい。While the size of the underlying substrate 1 is specified in the case of a circular shape, the size of the base substrate 1 is preferably 50 mm×50 mm or more, more preferably 75 mm×75 mm or more, from the viewpoint of increasing the size of the square substrate. . Moreover, the upper limit of the dimension is preferably 200 mm×200 mm or less from a practical viewpoint. The substrate for the diamond layer therefore has a surface area of at least 20 cm 2 . Furthermore, from the viewpoint of increasing the size, it is more preferable to have a surface area of up to 1297 cm 2 .

また、前記下地基板1の厚みは、3.0mm以下であることが好ましく、1.5mm以下であることがより好ましく、1.0mm以下であることが更に好ましい。厚みの下限値は特に限定されないが、剛性を確保する観点から0.05mm以上であることが好ましく、0.4mm以上であることがより好ましい。尚、平面方向の形状が円形状で、直径50mm以上150mm以下のときは当該厚みが0.3mm以上、直径が150mmを超えるときは、厚みが0.6mm以上あることが、それぞれ好ましい。 The thickness of the base substrate 1 is preferably 3.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less. Although the lower limit of the thickness is not particularly limited, it is preferably 0.05 mm or more, more preferably 0.4 mm or more, from the viewpoint of ensuring rigidity. When the shape in the planar direction is circular and the diameter is 50 mm or more and 150 mm or less, the thickness is preferably 0.3 mm or more, and when the diameter exceeds 150 mm, the thickness is preferably 0.6 mm or more.

尚、本実施形態では、下処理として下地基板1の面上に、イリジウム(Ir)単結晶膜2を成膜し、当該Ir単結晶膜上にダイヤモンド層を成長形成している。 In this embodiment, the iridium (Ir) single crystal film 2 is formed on the surface of the underlying substrate 1 as a pretreatment, and the diamond layer is grown on the Ir single crystal film.

次に、片面にダイヤモンド単結晶から成るダイヤモンド層3を成長させて形成する。ダイヤモンド層の成長方法は特に限定されず、公知の方法が利用できる。成長方法の具体例としては、パルスレーザ蒸着(PLD:Pulsed Laser Deposition)法や、化学気相蒸着法(CVD:Chemical Vapor Deposition)法等の気相成長法がある。 Next, a diamond layer 3 made of a diamond single crystal is grown on one side to form it. A method for growing the diamond layer is not particularly limited, and a known method can be used. Specific examples of growth methods include vapor deposition methods such as a pulsed laser deposition (PLD) method and a chemical vapor deposition (CVD) method.

前記CVD法を用いる場合、CVD成長炉内にダイヤモンド層用の基板を配置し、当該基板片面上にCVDダイヤモンド単結晶を成長させる。成長方法は、直流プラズマ法、熱フィラメント法、燃焼炎法、アークジェット法等が利用可能であるが、不純物の混入が少ない高品質なダイヤモンドを得るためにはマイクロ波プラズマ法が好ましい。 When using the CVD method, a substrate for a diamond layer is placed in a CVD growth furnace, and a CVD diamond single crystal is grown on one side of the substrate. As a growth method, a direct current plasma method, a hot filament method, a combustion flame method, an arc jet method, or the like can be used, but a microwave plasma method is preferable in order to obtain high-quality diamond with less contamination.

当該マイクロ波プラズマCVDによるダイヤモンド層のエピタキシャル成長では、原料ガスとして水素、炭素を含む気体を使用する。水素、炭素を含む気体としてメタン/水素ガス流量比0.001%~30%でメタンを成長炉内に導入する。炉内圧力は約1.3×10Pa~1.3×10Paに保ち、周波数2.45GHz(±50MHz)、或いは915MHz(±50MHz)のマイクロ波を電力100W~60kW投入することによりプラズマを発生させる。そのプラズマによる加熱で温度を700℃~1300℃に保った基板片面上に活性種を堆積させて、CVDダイヤモンドを成長させる。ダイヤモンド層の厚みは30μm以上500μm以下の厚みで成長することが好ましい。
In the epitaxial growth of the diamond layer by the microwave plasma CVD, a gas containing hydrogen and carbon is used as a raw material gas. As a gas containing hydrogen and carbon, methane is introduced into the growth furnace at a methane/hydrogen gas flow rate ratio of 0.001% to 30%. The pressure in the furnace is maintained at about 1.3×10 3 Pa to 1.3×10 5 Pa, and the microwave frequency of 2.45 GHz (±50 MHz) or 915 MHz (±50 MHz) is supplied with power of 100 W to 60 kW. Generate plasma. Active species are deposited on one side of the substrate, which is kept at a temperature of 700° C. to 1300° C. by heating with the plasma, to grow CVD diamond. The thickness of the diamond layer is preferably 30 μm or more and 500 μm or less.

上記ダイヤモンド層3を形成後、下地基板1を分離する。本実施形態では、硝酸等を用いたウェットエッチングによって下地基板1を除去すると共に、残ったIr膜2について半田と合金化後、同様の方法で除去している。 After forming the diamond layer 3, the underlying substrate 1 is separated. In this embodiment, the underlying substrate 1 is removed by wet etching using nitric acid or the like, and the remaining Ir film 2 is removed by the same method after being alloyed with solder.

上記述べた方法によって製造された図1記載のホモエピ用基板4について、本実施形態では育成された表面Oを底面とし裏面Uに再度上記ダイヤモンド基板層の気相成長を行った。(図1中(e)参照)尚、当該成長の条件は前記ダイヤモンド基板層の気相成長時と同条件を用いている。当該再度の気相成長により、本実施形態では同一材質上へのホモエピタキシャル成長によって高品質な単結晶ダイヤモンド基板を得ることができた。
1 manufactured by the above-described method, the grown surface O was used as the bottom surface, and the back surface U was subjected to vapor phase epitaxy of the diamond substrate layer again in this embodiment. (Refer to (e) in FIG. 1) The conditions for the growth are the same as those for the vapor phase growth of the diamond substrate layer. By the second vapor phase epitaxy, a high-quality single crystal diamond substrate could be obtained by homoepitaxial growth on the same material in the present embodiment.

図2に本実施形態で得られたホモエピ用基板4の表面AFM測定画像を示す。ここで、図2(a)が上記表面Oの結晶表面、(b)が裏面Uの育成用結晶表面であり、表面の表面粗さRa=19.1nm、裏面の表面粗さRa=4.0nmとなっている。図2から解るように、本実施形態で得られたホモエピ用基板は、表面よりも裏面の表面粗さが滑らかに形成されている。これは、上記下地基板の表面が分離した裏面の結晶表面に影響している為で、透過型電子顕微鏡を用いた当該裏面の観察により、加工に起因する原子の乱れ、即ち加工変質層が無いことを確認することができた。 FIG. 2 shows a surface AFM measurement image of the homo-epi substrate 4 obtained in this embodiment. Here, FIG. 2(a) is the crystal surface of the surface O, and FIG. 2(b) is the crystal surface for growth of the back surface U. 0 nm. As can be seen from FIG. 2, the homo-epitaxial substrate obtained in this embodiment has a smoother surface roughness on the back surface than on the front surface. This is because the surface of the underlying substrate affects the crystal surface on the separated back surface. Observation of the back surface using a transmission electron microscope shows that there is no atomic disturbance due to processing, that is, there is no process-affected layer. I was able to confirm that.

以上述べたように、本願実施形態記載のホモエピ用基板を用いることで、表面に加工変質層を生じることなく、高精度かつ滑らかな表面粗さを有する単結晶ダイヤモンド基板を提供することができる。 As described above, by using the homo-epitaxial substrate according to the embodiments of the present application, it is possible to provide a single-crystal diamond substrate having high precision and smooth surface roughness without forming a work-affected layer on the surface.

1 下地基板
2 Ir層
3 ダイヤモンド基板層
4 ホモエピタキシャル成長用単結晶ダイヤモンド基板
O 表面
U 裏面
REFERENCE SIGNS LIST 1 base substrate 2 Ir layer 3 diamond substrate layer 4 single crystal diamond substrate for homoepitaxial growth O surface U back surface

Claims (2)

単結晶ダイヤモンド基板成長用の下地基板として、MgO単結晶,α-Al,Si,石英,白金,イリジウム,チタン酸ストロンチウム(SrTiO)の何れかを材質とし、表面粗さRaが10nm以下の面を有する前記下地基板を用意し、
前記下地基板の前記面上にイリジウム単結晶膜を成膜し、
前記下地基板を成長炉内に配置し、
水素、炭素を含む気体としてメタン/水素ガス流量比0.001%~30%でメタンを前記成長炉内に導入し、
前記成長炉の炉内圧力を1.3×10Pa~1.3×10Paに保ち、
周波数2.45GHz(±50MHz)、或いは915MHz(±50MHz)のマイクロ波を電力100W~60kW投入することによりプラズマを発生させ、
前記プラズマによる加熱で温度を700℃~1300℃に保った前記下地基板片面上に活性種を堆積させて、
前記イリジウム単結晶膜上に単結晶ダイヤモンド基板を30μm以上500μm以下の厚みで気相成長させ、
ウェットエッチングで前記下地基板と前記イリジウム単結晶膜を除去して、前記単結晶ダイヤモンド基板の表面及び裏面に加工変質層がなく、前記裏面を表面粗さRa=10nm以下の面にし、
前記単結晶ダイヤモンド基板の前記裏面側に再度気相成長を行い、ホモエピタキシャルでダイヤモンド基板層を成長させる前記単結晶ダイヤモンド基板を用いたダイヤモンド基板層の製造方法。
A base substrate for growth of a single crystal diamond substrate is made of any one of MgO single crystal, α-Al 2 O 3 , Si, quartz, platinum, iridium, and strontium titanate (SrTiO 3 ), and has a surface roughness Ra of 10 nm. preparing the base substrate having the following surfaces;
forming an iridium single crystal film on the surface of the underlying substrate;
placing the underlying substrate in a growth furnace;
introducing methane as a gas containing hydrogen and carbon into the growth furnace at a methane/hydrogen gas flow rate ratio of 0.001% to 30%;
keeping the pressure in the growth furnace at 1.3×10 3 Pa to 1.3×10 5 Pa,
Plasma is generated by applying microwaves with a frequency of 2.45 GHz (±50 MHz) or 915 MHz (±50 MHz) with power of 100 W to 60 kW,
Depositing active species on one side of the base substrate which is kept at a temperature of 700° C. to 1300° C. by heating with the plasma,
vapor-growing a single-crystal diamond substrate to a thickness of 30 μm or more and 500 μm or less on the iridium single-crystal film;
removing the base substrate and the iridium single-crystal film by wet etching to make the front and back surfaces of the single-crystal diamond substrate free from work-affected layers and to make the back surface have a surface roughness Ra of 10 nm or less;
A method for producing a diamond substrate layer using the single crystal diamond substrate, wherein vapor phase epitaxy is performed again on the back side of the single crystal diamond substrate to grow the diamond substrate layer homoepitaxially.
前記裏面を表面粗さ Ra=5nm以下の面にする、請求項1記載のダイヤモンド基板層の製造方法。 Surface roughness of the back surface Ra=5 nm or lessto faceA method for producing a diamond substrate layer according to claim 1.
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