JP3555114B2 - Diamond flattening method - Google Patents

Description

【０１２８】
上記表１に示したように、上述のような平坦化処理を施すことにより、上記 （１）〜（３）のすべてのダイヤモンド基板の表面粗さを非常に小さくすることができた。すなわち、本発明の平坦化処理による平坦化効果が大きいことが確認された。
【０１２９】
実施例２
実施例１において１回の平坦化処理が施された（１）〜（３）の各基板を用意した（ＳＴＥＰ４）。したがって、下記表２（ＳＴＥＰ４）に示した各基板の表面粗さは、表１（ＳＴＥＰ３）に示した各基板の表面粗さと等しいものとして、以下の処理を行った。
【０１３０】
次に、実施例１と同様に、各基板上にレジスト膜を形成した（ＳＴＥＰ５）。得られた各レジスト膜における表面粗さを測定した。得られた結果を下記表２（ＳＴＥＰ５）に示す。
【０１３１】
次に、イオン注入装置を用いて、上記（１）〜（３）の各基板上に形成されたレジスト膜表面から、Ａｒイオンを加速電圧５０ｋｅＶ、５００ｋｅＶ、１ＭｅＶ、２ＭｅＶでドーズ量にして１０^１５ｃｍ^−２でイオン注入した。
【０１３２】
イオン注入後、実施例１と同様に、レジスト膜を各基板上からすべて除去し、イオン注入により非晶質化またはグラファイト化した部分を、水素を含むガスのプラズマ中に晒して、各基板表面から除去し、ダイヤモンド表面の平坦化を行なった（ＳＴＥＰ６）。得られた各基板の表面粗さを測定した。得られた結果を下記表２（ＳＴＥＰ６）に併せて示す。
【０１３３】
【表２】

【０１３４】
上記表２に示したように、上述したような平坦化処理を２回繰返して行なうことにより、１回の平坦化処理を行なった場合に比べて、各基板の表面粗さを更に小さくすることができることが判明した。
【０１３５】
特に、本実施例においては、基板表面に２０００Åの表面粗さを有していた多結晶ダイヤモンドからなる基板に、２回の平坦化処理を行なうことにより、表面粗さを１０分の１程度まで平坦化できることが示された。すなわち、平坦化の効果が非常に大きいことが確認された。
【０１３６】
実施例３
実施例１と同様に、上記（１）〜（３）の各基板を用意し（ＳＴＥＰ１）、次いで各基板上にレジスト膜を形成した（ＳＴＥＰ２）。したがって、表３（ＳＴＥＰ１）に示した各基板の表面粗さは、表１（ＳＴＥＰ１）に示した各基板の表面粗さと等しく、また表３（ＳＴＥＰ２）に示した各基板のレジスト膜における表面粗さは、表１（ＳＴＥＰ２）に示した各基板のレジスト膜における表面粗さと等しいものとして、以下の処理を行った。
【０１３７】
次に、イオン注入装置を用いて、（１）〜（３）の各基板上に形成されたレジスト膜表面から、Ａｒイオンを加速電圧５０ｋｅＶ、５００ｋｅＶ、１ＭｅＶ、２ＭｅＶでドーズ量にして１０^１５ｃｍ^−２でイオン注入した。イオン注入後、レジスト膜を各基板上からすべて除去し、各基板の表面を露出させた。
【０１３８】
本実施例では、イオン注入によりダイヤモンドが非晶質化またはグラファイト化した部分を各基板表面から除去する際に、プラズマエッチングを使用せず、クロム酸によるウェットエッチングを行なった。
【０１３９】
上記ウェットエッチングにより、基板表面から非晶質化またはグラファイト化した部分を除去し、ダイヤモンド表面の平坦化を行なった（ＳＴＥＰ３）。得られた各基板の表面粗さを測定した。得られた結果を下記表３（ＳＴＥＰ３）に併わせて示す。
【０１４０】
【表３】

【０１４１】
表３に示したように、クロム酸によるウェットエッチングを用いて平坦化処理を行なった場合においても、イオン注入によりダイヤモンドが非晶質化またはグラファイト化した部分を基板表面から効率よく除去することができ、各基板の表面粗さを非常に小さくすることができることが確認された。
【０１４２】
実施例４
気相合成法でＳｉ基板上に形成された多結晶ダイヤモンドからなる基板のみを用いて、実施例１と同様の平坦化処理を行なった。本実施例では、注入イオンに対する金属元素添加による平坦化処理の効果を調べるため、Ａｌ、Ｗ、Ｍｏ、Ｆｅ、Ａｕがそれぞれ１０²⁰ｃｍ^-3添加され、均一に混合されたフォトレジスト剤（商品名：ＯＭＲ、東京応化社製）を使用した。
【０１４３】
実施例１と同様に、各基板上に各金属元素が添加されたレジスト剤または無添加のレジスト剤を、各々スピナーで回転塗布し、レジスト膜を形成した（ＳＴＥＰ２）。このようにして、得られたレジスト膜表面における表面粗さを測定し、すべて１００Å以下となるようにした。
【０１４４】
次に、イオン注入装置を用いて、各基板上に形成されたレジスト膜表面から、Ａｒイオンを加速電圧５０ｋｅＶ、５００ｋｅＶ、１ＭｅＶ、２ＭｅＶでドーズ量にして１０^１５ｃｍ^−２でイオン注入を行なった。イオン注入後、レジスト膜を各基板上から除去し、イオン注入により非晶質化またはグラファイト化した部分を、水素を含むガスのプラズマ中に晒して、各基板表面から除去しダイヤモンド表面の平坦化を行なった（ＳＴＥＰ３）。得られた各基板表面粗さを測定し、その結果を下記表４（ＳＴＥＰ３）に併せて示した。
【０１４５】
【表４】

【０１４６】
上記表４に示したように、金属元素が添加されたレジスト剤を用いることにより、金属元素を一切添加しないレジスト剤を用いた場合に比べて、更に基板表面粗さを小さくできることが確認された。本発明者の知見によれば、レジスト膜内に金属元素が均一に添加されることで、イオン注入するＡｒイオンに対するレジスト膜の阻止断面積と、ダイヤモンドからなる各基板の阻止断面積とがほぼ一致するためであると推定される。
【０１４７】
実施例５
実施例４と同様に、気相合成法でＳｉ基板上に形成された多結晶ダイヤモンドからなる基板を用いて、実施例１と同様の平坦化処理を行なった。
【０１４８】
ただし本実施例では、基板上にレジスト膜を形成する代わりに、ゾルーゲル法により基板上にＳｉＯ_２ 膜を形成した。
【０１４９】
また、本実施例では、金属元素添加による平坦化の効果を調べるため、Ａｌ、Ｗ、Ｍｏ、Ｆｅ、Ａｕがそれぞれ１０^２０ｃｍ^−３添加され均一に混合されたゲルを使用した。
【０１５０】
まず、各基板上に、金属元素が添加されたＳｉＯ系ゾルまたは金属元素無添加のＳｉＯ系ゾルを各々スピナーで回転塗布した。ゾルーゲル法に従い、加熱を施すことで、基板上のＳｉＯ系ゾルを固化させてＳｉＯ_２ からなるゲル層を形成した（ＳＴＥＰ２）。このようにして得られたＳｉＯ_２ 層表面における表面粗さを測定し、すべて１００Å以下になるようにした。
【０１５１】
次に、イオン注入装置を用いて、各基板上に形成されたＳｉＯ_２ 層表面から、Ａｒイオンを加速電圧５０ｋｅＶ、５００ｋｅＶ、１ＭｅＶ、２ＭｅＶでドーズ量にして１０^１５ｃｍ^−２でイオン注入した。イオン注入後、ＳｉＯ_２ 層をＨＦ処理により基板上からすべて除去し、各基板の表面を露出させた。その後、ダイヤモンドが非晶質化またはグラファイト化した部分を、水素を含むガスのプラズマ中に晒して、各基板表面から除去し、平坦化を行なった（ＳＴＥＰ３）。得られた各基板の表面粗さを測定し、その結果を下記表５（ＳＴＥＰ３）に併せて示した。
【０１５２】
【表５】

【０１５３】
上記表５に示したように、基板上にゾルーゲル法に従ってＳｉＯ_２ 層を形成して平坦化処理を行なった場合にも、基板の表面粗さを非常に小さくすることができることが確認された。また、種々の金属元素が添加されたゾル剤を用いることで、基板の表面粗さをより小さくすることができることが確認された。本発明者の知見によれば、これはＳｉＯ_２ 層の阻止断面積とダイヤモンドからなる基板の阻止断面積がほぼ一致するためであると推定される。
【０１５４】
上述した、実施例４および実施例５で得られた結果に基づき、注入イオンの種や注入条件により、レジスト剤に添加する金属元素の種およびその添加量を適切に設定することで、１回の平坦化処理を施すだけでも、所望の平坦度を有する基板を実現できることが判明した。
【０１５５】
実施例６
実施例４と同様に、気相合成法でＳｉ基板上に形成された多結晶ダイヤモンドからなる基板のみを用いて、実施例１と同様の平坦化処理を行なった。
【０１５６】
ただし、本実施例では、Ａｒ、Ｎｅ、Ｈｅ、Ａｌ、Ｘｅ、Ｃｕイオンを用いてイオン注入した。
【０１５７】
実施例１と同様に、各基板上にレジスト剤を各々スピナーで回転塗布し、レジシウト膜を形成した（ＳＴＥＰ２）。このようにして得られたレジスト膜表面における表面粗さを測定し、すべて１００Å以下になるようにした。次に、イオン注入装置を用いて、各基板上に形成されたレジスト膜表面からＡｒ、Ｎｅ、Ｈｅ、Ａｌ、Ｘｅ、Ｃｕの各イオンを、それぞれ加速電圧５０ｋｅＶ、５００ｋｅＶ、１ＭｅＶ、２ＭｅＶでドーズ量にして１０¹⁵ｃｍ^-2でイオン注入を行なった。イオン注入後、レジスト膜を各基板上から除去し、イオン注入によりダイヤモンドが非晶質化またはグラファイト化した部分を、水素を含むガスのプラズマ中に晒して、各基板表面から除去し平坦化を行なった（ＳＴＥＰ３）。得られた各基板の表面粗さを測定し、その結果を下記表６（ＳＴＥＰ３）に併せて示した。
【０１５８】
【表６】

【０１５９】
上記表６に示したように、使用したすべての種類のイオンで、基板の表面粗さを大幅に小さくすることができ、平坦化の効果が確認された。
【０１６０】
実施例７
図９（ａ）に示すように、（１００）面の単結晶ダイヤモンド基板５１上に、４０００回転（ｒｐｍ）のスピードで、スピンオングラス５２を０．７μｍ塗布した。次いで、上記スピンオングラス５２を焼結させるため、Ｎ₂ 雰囲気中３５０℃２０分間アニールした。
【０１６１】
更に、図９（ｂ）に示すように、リアクティブエッチング装置を使い、フロンガス（ＣＦ_４ ）５０ｓｃｃｍ、１３．５６ＭＨｚのＲＦパワー３００Ｗの条件で１０分間、上記により焼結したスピンオングラス（ＳｉＯ_２ ）をエッチングした。これにより、０．４μｍスピンオングラスをエッチバックして、ダイヤモンド表面の凸部を露出させた。
【０１６２】
図９（ｃ）に示すように、このように露出させた凸部に、電子ビーム蒸着装置を用いて、鉄（Ｆｅ）を０．２μｍ蒸着した。
【０１６３】
次いで図９（ｄ）に示すように、アルゴンガス雰囲気中、１５００℃、１０秒のランプアニールを行って、上記鉄とダイヤモンド凸部とを反応させた。
【０１６４】
更に、リアクライブイオンエッチング装置を用い、アルゴン（Ａｒ）８０ｓｃｃｍ、酸素（Ｏ_２ ）２０ｓｃｃｍ、１３．５６ＭＨｚのＲＦパワー３００Ｗの条件で６０分間エッチングし、反応部分の約０．３μｍ程度を除去した。この条件では、ダイヤモンドの鉄との反応部分（凸部）では、未反応部分（凹部）に比べ、１０倍エッチング速度が速かった。更に、ＳｉＯ_２ を除去して、図９（ｅ）に示すような平滑なダイヤモンド表面を得た。このようにして得たダイヤモンド表面の平滑度を測定したところ、Ｒ_ｍａｘ で０．１μｍ以下であった。
【０１６５】
上述したように参考例によれば、ダイヤモンドの表面に該ダイヤモンドと異なる材料からなる平坦な被膜を形成した後；ドライエッチングにより、前記ダイヤモンドと被膜との双方をエッチングし得る条件下で、前記被膜およびダイヤモンド表面の凹凸を除去して、該ダイヤモンドの表面を平滑化するダイヤモンドの平坦化法が提供される。
【０１６６】
他の参考例によれば、ダイヤモンドの表面に該ダイヤモンドと異なる材料を含む液状の塗布剤を滴下し硬化させて、ダイヤモンド上に表面が球面状の被膜を形成した後；ドライエッチングにより、前記被膜とダイヤモンドとの双方をエッチングし得る条件下で、前記被膜およびダイヤモンド表面の凹凸を除去して、球面状のダイヤモンド表面を得ることを特徴とするダイヤモンドの研磨方法が提供される。
【０１６７】
【発明の効果】
本発明に係る平坦化法を用いれば、従来のスカイフ研磨等の機械研磨とは異なり、非接触で表面を平坦化することができるため、基板の材質、そり量、面積、厚み等の基板の状態に実質的に制限を受けることなく、種々のダイヤモンド表面に良好に鏡面仕上げ研磨ないし平坦化することが可能になる。
【０１６８】
上記したダイヤモンドの平坦化法または研磨方法においては、大型のドライエッチング装置を用いることによって、より大面積のダイヤモンドの平坦化ないし研磨に充分に対応することができる。
【０１６９】
このようなダイヤモンドの平坦化法または研磨方法によれば、極めて平滑性に優れたダイヤモンド表面が得られるため、従来の機械研磨によって得られるダイヤモンド表面上には不可能であったレベルの超微細加工を、該ダイヤモンド表面上に施すことが可能となる。更には、本発明によれば、従来の機械研磨に比べて研磨工程が大幅に簡略化されるため、効率的なコスト低減が可能となり、工業的にも充分利点のある平坦化法ないし研磨法を提供することができる。
【０１７０】
また、上記したダイヤモンドの研磨方法を用いれば、ダイヤモンド以外の材料では得ることができなかった波長域、すなわち紫外線域（波長２２５ｎｍ以下程度）まで光を透過でき、しかも熱伝導率が高い、高信頼性のダイヤモンドレンズを得ることが可能となる。特に、本発明の研磨方法は、マイクロレンズ形成に好適に適用することができる。
【０１７１】
更に、本発明の他の態様によれば、ダイヤモンドの表面に該ダイヤモンドと異なる材料からなる被膜を形成して、該被膜を平坦化する第１の工程と；前記被膜を介して、前記ダイヤモンドにイオン注入を行なう第２の工程と；前記被膜を除去するとともに、前記イオン注入により変質したダイヤモンド部分を、前記ダイヤモンドから除去する第３の工程とを備えるダイヤモンドの平坦化法が提供される。
【０１７２】
このようなダイヤモンドの平坦化法は、５０Å以下のより厳しい平坦度が要求される電子光学部品（特に、高出力の半導体レーザ等に使用可能なＬＳＩ用等の放熱基板）の製作に好適に応用することができる。
【０１７３】
更に、本発明の他の態様によれば、乾式法によりダイヤモンド表面を平坦化させるに際し、該ダイヤモンド表面凸部の減削速度を、該ダイヤモンド表面の凹部の減削速度より相対的に大きくするダイヤモンドの平坦化法が提供される。
【０１７４】
このようなダイヤモンド平坦化法によれば、多結晶又は単結晶ダイヤモンドからなり、平滑な表面を有する電子デバイス用の基板を提供することが可能となる。
【図面の簡単な説明】
【図１】本発明のダイヤモンド研磨方法の一態様を示す模式側面断面図である。
【図２】本発明のダイヤモンド研磨方法の他の態様を示す模式側面断面図である。
【図３】本発明のダイヤモンド研磨方法の更に他の態様を示す模式側面断面図である。
【図４】本発明のダイヤモンド研磨方法の更に他の態様を示す模式側面断面図である。
【図５】本発明のダイヤモンド平坦化方法の一態様を工程順に示す模式側面断面図である。
【図６】本発明のダイヤモンド平坦化方法の一態様を工程順に示す模式側面断面図である。
【図７】本発明のダイヤモンド平坦化方法の他の態様を工程順に示す模式側面断面図である。
【図８】本発明のダイヤモンド平坦化方法の他の態様を工程順に示す模式側面断面図である。
【図９】本発明のダイヤモンド平坦化方法の更に他の態様を示す模式側面断面図である。
【符号の説明】
１…基板、２，１０，２０，５１…ダイヤモンド、３，１１，３０…被膜、４，２０，２５…ダイヤモンド表面、１２，１４…ダイヤモンドレンズ、３５，３６…被膜表面、４０…注入イオン、４５…ダイヤモンド変質部分、５１…ダイヤモンド基板、５２…犠牲層、１００…被膜の膜厚が大きい領域、１０５…被膜の膜厚が小さい領域。[0001]
[Industrial applications]
The present invention relates to polishing or flattening of single crystal diamond or polycrystalline diamond, and more particularly to providing a diamond substrate surface applicable to cutting tools, abrasive tools, surface acoustic wave devices, semiconductor devices, large area heat sink lenses and the like. PossibleDiamond flattening methodAbout.
[0002]
[Prior art]
Diamond not only has excellent light transmittance over a wide wavelength range from infrared to ultraviolet except for a part of the infrared region, has excellent pressure resistance and is the hardest material among materials. have. Therefore, diamond is an optimal substance as an optical material that does not damage.
[0003]
In addition, diamond has the highest Young's modulus among materials, and has the property of propagating at a very high speed when a surface acoustic wave is excited. Therefore, diamond is attracting attention as a material for a high-frequency band-pass filter used for mobile communication and the like, and research is progressing.
[0004]
Further, since diamond has the largest thermal conductivity among materials, its use as a heat sink for devices such as semiconductor lasers and ICs has been studied.
[0005]
Further, application of diamond has attracted attention as a material for devices that operate stably even under severe environments such as high temperatures and radiation, and as a material for devices that can withstand high-power operations.
[0006]
The reason why diamond can operate even at high temperatures is that the band gap is as large as 5.5 eV. This indicates that the temperature range (intrinsic region) in which the carrier of the semiconductor is not controlled does not exist below 1400 ° C.
[0007]
As a method of artificially synthesizing diamond, an ultra-high pressure synthesis method has been conventionally used, but recently, a diamond crystal has been synthesized even by using a gas phase synthesis method. Accordingly, application of diamond to optical materials, semiconductor materials, and the like is further expected.
[0008]
In recent years, when diamond is used for a heat sink of a surface acoustic wave device, a semiconductor device, and various devices, a diamond having a much larger surface area and a mirror surface and a flatness which can be processed ultra-finely is conventionally used. It has come to be required.
[0009]
However, the surface of the artificial diamond obtained by the ultra-high pressure synthesis method or the gas phase synthesis method usually has considerably large irregularities of about 1000 μm. In such a case, the surface of the artificial diamond is polished. Need to be planarized.
[0010]
However, as described above, since diamond is the hardest material among materials, it is not always easy to polish and flatten diamond.
[0011]
Conventionally, a method based on mechanical processing has been used for polishing the diamond surface.
[0012]
As a method by such mechanical processing, for example, after roughing the surface of diamond having irregularities by a physical means such as a grinder, polishing using diamond abrasive grains, and further, by high-speed friction at high temperatures, the irregularities are formed. And skiff polishing in which the diamond component is dissolved to flatten the diamond surface.
[0013]
However, in the conventional polishing method, although it is possible to obtain a relatively good mirror surface, since the polishing is based on direct contact, the polishing ability is limited by the material of the substrate, the amount of warpage, the area, the thickness and the like of the substrate. Had the disadvantage of being greatly influenced by
[0014]
In addition, in order to obtain a desired smoothness in such mechanical polishing, it was necessary to control the particle size of the abrasive grains of the polishing plate. Control was difficult.
[0015]
For example, in the case of a diamond film formed on a thin-film silicon substrate, the "warp" becomes remarkable as the area of the diamond film increases, and the amount of warp may reach several tens of micrometers. In this case, if mechanical pressure is applied to the substrate by contact polishing, the substrate may be cracked. As described above, in mechanical polishing, the size of a polishing apparatus and a polishing plate, the thickness of a diamond substrate that can be polished, and the like are limited. Therefore, the diamond film that can be mechanically polished is limited to a film formed on a small-sized substrate. Therefore, mechanical polishing of a diamond film formed on a large-area substrate has been extremely difficult.
[0016]
On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 2-26900, there is a method of using a metal such as iron as an abrasive and removing a layer that has reacted with diamond. However, the problems in the contact polishing as described above remain unsolved.
[0017]
On the other hand, as disclosed in JP-A-64-68484, there is a method in which diamond is smoothed by irradiating an ion beam or the like in a non-contact manner.
[0018]
However, although the specularity is improved by this method, the smoothness thereof is remarkably inferior to that of the above-described contact polishing, and it is impossible to apply the diamond film smoothed by this method to fine processing or the like. Was.
[0019]
In Japanese Patent Application Laid-Open No. 64-62484, as an extension of the above method, an amorphous carbon film, which is a substance similar to diamond, is formed on a diamond film by a CVD (chemical vapor deposition) method and etched back. A method of etching diamond from the side of a once formed flat amorphous carbon film has been proposed. However, since the diamond surface obtained by this method has large irregularities and it is difficult to sufficiently planarize it, it is extremely difficult to apply the diamond film obtained by this method to fine processing. Furthermore, since this method requires a long time to form an amorphous carbon film (relatively thick), this method is not preferable in terms of manufacturing cost.
[0020]
As described above, in the related art, a method of flattening diamond using a diamond grindstone or diamond abrasive grains has been mainly used. In addition, Appl. Phys. Lett. ,63(1993), 622, a method of flattening the surface of a diamond film using a metal such as cerium or lanthanum and utilizing the diffusional transfer of carbon atoms from diamond to these metals. It has been known. However, the flattening by these methods requires a long processing time, or it is difficult to smooth the surface so that the unevenness of the surface becomes submicron or less.
[0021]
[Problems to be solved by the invention]
When single crystal diamond or polycrystalline diamond is to be used as a constituent material of an electronic device, the flatness of the diamond surface is usually about one tenth of the wiring length from the viewpoint of forming fine wiring or the like on the diamond. Alternatively, it is extremely preferred that the value be less than that. According to the study of the present inventors, the above-mentioned Appl. Phys. Lett. ,63(1993), 622, a flatness of only several tens of μm can be obtained. Further, the LSI design / manufacturing technique (Michitada Morisue, published by Denki Shoin, 1987) p370 includes CF as an etching gas when etching a resist layer formed on PSG (phospho-silicate glass).₄To O₂Increases the etching rate of the resist,₂Utilizing the fact that the etching rate of a resist is reduced by the addition of, a method is disclosed in which a resist and a PSG are simultaneously etched under the same etching rate to leave a flat PSG film. In the flattening process by the etching method in such a semiconductor process, the dry etching rate of the sacrificial layer (PSG in this case) and the film to be flattened can be easily made the same only by changing the gas composition. Met.
[0022]
However, when this method is applied to the flattening of the diamond film, it is difficult to make the dry etching rates of the diamond and the sacrificial layer the same, and even if the same rate is obtained, the etching rate is reduced. It has to be extremely slow. Therefore, the flattening of the diamond film has a disadvantage that a considerably long processing time is required.
[0023]
In general, it is preferable that the surface of diamond is as small as possible from the viewpoint that a fine wiring pattern or the like can be stably formed on the surface.
[0024]
Accordingly, an object of the present invention is to solve the above-mentioned conventional problems with a diamond.Flattening methodIs to provide.
[0025]
Another object of the present invention is to provide a diamond surface on which a diamond surface capable of stably forming fine wiring or the like can be provided in a short time.Flattening methodIs to provide.
[0026]
Still another object of the present invention is to provide a non-contact, mirror-finished diamond that can be subjected to mirror-finish polishing without being substantially affected by the state of the substrate such as the material of the substrate, the amount of warpage, the area, and the thickness.Flattening methodIs to provide.
[0027]
Still another object of the present invention is to provide a diamond film on which a fine processing can be performed at a low cost.Flattening methodIs to provide.
[0028]
[Means for Solving the Problems]
According to the present invention, when flattening a diamond surface by a dry method, a diamond flattening method in which the cutting speed of the diamond surface convex portion is relatively larger than the cutting speed of the concave portion of the diamond surface.Using a single crystal or polycrystalline diamond as a diamond, forming a flat sacrifice layer on the diamond, uniformly etching the sacrifice layer to expose a projection on the diamond surface, Characterized in that an impurity is attached to the substrate, annealing is performed to react the impurity with the convex portion, and then the convex portion is removed.
Is provided.
[0031]
According to the present invention, further, a first step of forming a flat film made of a material different from the diamond on the surface of the diamond,
A second step of ion-implanting diamond through the coating;
A third step of removing the coating and removing a diamond portion altered by the ion implantation from the diamond.
[0032]
In such a diamond flattening method, the above-described first to third steps may be repeated as necessary to increase the smoothness of the diamond surface.
[0033]
Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.
[0034]
(diamond)
The type of diamond that can be used in the present invention is not particularly limited. More specifically, for example, the flattening method or polishing method of the present invention may be a natural diamond, a diamond made of a bulk single crystal artificially produced by a high-pressure synthesis method, or a substrate or the like artificially produced by a gas phase synthesis method. It can be applied to flatten or polish the surface of various diamonds such as diamond made of thin film polycrystal or thin film single crystal formed thereon.
[0035]
(Coating)
In order to flatten the diamond surface, a film (or a sacrificial layer) to be formed on the diamond surface can be formed using various materials different from diamond. It can be formed by the method described above. More specifically, for example, a method in which a liquid coating material containing a material different from diamond is applied so as to fill irregularities on the diamond surface and solidified (by evaporating a solvent or the like); or a sol-state coating on the diamond surface according to a sol-gel method After coating the material, the film can be relatively easily formed and flattened (forming a flat film) by, for example, a method of converting to a gel state and solidifying to form a flat surface;
[0036]
When the above-mentioned film is formed using a liquid material, it is preferable that an appropriate amount of the liquid material is dropped on the surface of the diamond to be flattened, and spin coating is performed using a spinner or the like.
[0037]
As a material to be used for forming a film (a material different from diamond), a material that can form a relatively stable and uneven surface on the diamond surface by coating on the diamond surface is preferably used. More specifically, for example, such a material is mainly composed of an organic material containing silicon (Si), boron (B), or the like, or an inorganic material containing silicon (Si), boron (B), or the like. And the main component is.
[0038]
Examples of the material for forming a film mainly containing an inorganic material containing Si, B, and the like include an inorganic silicon compound and an inorganic boron compound. For example, when a film made of an inorganic silicon compound or an inorganic boron compound is formed according to the sol-gel method, the surface of the diamond is coated with SiO 2₂System, B₂O₃After spin-coating (rotating) a sol of a system or the like using a spinner or the like, the sol can be converted by heating or the like to form a gel layer. For example, SiO used in a semiconductor process₂A system coating solution can be easily used.
[0039]
As a film forming material mainly composed of an organic material, a relatively inexpensive polyimide material used in a semiconductor device manufacturing process or the like can be easily used, but is not limited thereto. Can be used.
[0040]
As a material mainly composed of an organic material containing Si, B and the like, a liquid photoresist such as a water-soluble colloid system, a polycinnamic acid system, a cyclized rubber system, and a quinone diazide system can be suitably used.
[0041]
(Dry etching)
In the present invention, it is most preferable to use reactive ion etching (RIE) as a dry etching method, but it is also possible to use plasma etching, ion beam etching or the like. Regardless of the type of etching used, substantially the same smoothing effect can be obtained.
[0042]
Ar, He, CF₄, CHF₃, SF₆, BCl₃, CHCl₃And the like can be used alone or in combination. If necessary, add a small amount of O to these gases.₂, N₂O, N₂May be used.
[0043]
In the present invention, conditions under which both the film and the diamond can be etched by dry etching are basically realized by suppressing the etching selectivity between the film and the diamond during the dry etching to be smaller. In the present invention, it is preferable that the etching selectivity between the film and the diamond is in the range of 1: 2 to 2: 1 and further, the etching selectivity between the film and the diamond is approximately 1: 1 (that is, the etching selectivity is approximately 1: 1). , In the range of 0.8: 1 to 1: 0.8, and more preferably in the range of 0.9: 1 to 1: 0.9).
[0044]
For example, Ar is O₂When dry etching is performed in a gas system containing₂The etching selectivity between the film and the diamond can be adjusted to approximately 1: 1 by setting the ratio of the amount added to 0 to 10%.
[0045]
(Ion implantation)
The ion implantation in the present invention can be performed according to a usual ion implantation technique.
[0046]
There is no limitation on the element used for ion implantation, and any element can be appropriately selected and used. The ion used at this time is preferably an element having a mass sufficient to destroy and alter the crystalline state of diamond and a size large enough to be deeply introduced into diamond. More specifically, for example, Ar, Ne, He, Al, Xe, Cu and the like can be preferably used.
[0047]
In the present invention, at the time of ion implantation, if necessary, the blocking cross section (E) of diamond with respect to the implanted ions and the blocking cross section (F) of the coating with respect to the implanted ions substantially coincide with each other (preferably, the ratio of the blocking cross sections) The coating may be formed so that (F / E) is 0.1 to 10, more preferably 0.9 to 1.1. More specifically, the above is preferable.
[0048]
Here, the "blocking cross section" is defined as a quotient obtained by dividing the energy lost by the interaction of the implanted ions with the substance as it passes through the coating and diamond by the number of atoms or molecules per unit volume. . As described above, when the blocking cross-section of diamond for implanted ions and the blocking cross-section of the coating for implanted ions are substantially matched, the range of the implanted ions introduced into diamond and the coating can be made equal with good reproducibility. It becomes possible.
[0049]
Adjustment of the blocking cross section of the coating against the implanted ions can be made relatively easily, for example, by adding an appropriate amount of a metal element to the material used to form the coating and mixing uniformly.
[0050]
As the metal element added for such a purpose, for example, Mg, Al, Ti, W, Mo, Au, Pt, or the like can be suitably used. The amount of the metal element to be added can be determined by computer simulation based on the material constituting the film, the type of the implanted ions, and the type of the metal element to be added.
[0051]
(Removal of coating)
When removing the film, chemical or physical etching or a chemical treatment with a release agent, HF (hydrofluoric acid) or the like according to the material constituting the film can be appropriately selected and used.
[0052]
(Removal of altered part of diamond)
Either dry etching or chemical wet etching can be used to remove the portion where the diamond has been altered. Regardless of the type of etching, substantially the same effect can be obtained.
[0053]
As the dry etching, plasma etching using a gas discharge of hydrogen, oxygen, a halogen gas, or the like can be preferably used. As wet etching, etching using chromic acid treatment or the like can be preferably used.
[0054]
(Degree of flattening or polishing)
In the flattening or polishing method of the present invention, the smoothness of the diamond surface obtained is, for example, R_MaxOr R_a(Based on JIS B0601). More specifically, for example, the R_MaxIs A (μm), and R of the diamond surface after flattening or polishing is_MaxIs B (μm), in the present invention, the B / A ratio is usually preferably 1/3 or less, more preferably 1/5 or less (particularly 1/10 or less).
[0055]
(Diamond polishing method)
An operation mechanism of one embodiment of the diamond polishing method of the present invention will be described with reference to FIG.
[0056]
In this diamond polishing method, first, as shown in FIG. 1A, a diamond film 2 synthesized on a predetermined substrate 1 (for example, a silicon substrate) is prepared. Usually, irregularities exist on the entire surface of the diamond 2. A flat film made of a material different from the diamond is formed on the surface of the diamond 2.
[0057]
As a result, as shown in FIG. 1B, the unevenness existing on the entire surface of the diamond 2 on the substrate 1 is buried by the coating 3 and is not substantially affected by the degree of the unevenness on the surface of the diamond 2. Then, a coating 3 having a flat surface is formed.
[0058]
Next, dry etching is performed under a condition in which both the film 3 and the diamond 2 can be etched in a predetermined gas atmosphere (for example, a condition where the etching selectivity between the film 3 and the diamond becomes approximately 1: 1 as described above). Etching is performed from the surface of the coating 3 having a substantially flat surface.
[0059]
As a result, while the flatness is kept high, first, the coating 3 and the irregularities on the surface of the coating 3 and the diamond 2 are removed from the substrate 1 (for example, simultaneously), and the surface of the diamond 2 is smoothed.
[0060]
As a result, as shown in FIG. 1 (c), most of the irregularities existing on the entire surface of the coating 3 and the diamond 2 are finally removed, and a flat and mirror-finished diamond surface 4 can be obtained.
[0061]
Another embodiment of the diamond polishing method of the present invention will be described with reference to FIG.
[0062]
First, as shown in FIG. 2A, a substrate made of diamond 10 is prepared. The surface of the substrate made of diamond 10 usually has irregularities. A liquid coating agent made of a material different from diamond is dropped and cured on the entire surface of the substrate made of diamond 10 to form a coating 11 having a spherical surface.
[0063]
As a result, the unevenness existing on the surface of the substrate made of diamond 10 is buried by the coating 11 and the coating 11 having a smooth surface is not substantially affected by the degree of unevenness on the surface of the substrate made of diamond 10. Is formed.
[0064]
Next, in a predetermined gas atmosphere, dry etching is performed under the condition that both the coating 11 and the diamond 10 can be etched (for example, under the condition that the etching selectivity between the coating 11 and the diamond 10 becomes almost 1: 1). Etching is performed from the spherical surface side of the coating 11.
[0065]
As a result, first, the coating 11 is further removed from (for example, simultaneously with) the surface of the substrate composed of the coating 11 and the diamond 10 from the substrate composed of the diamond 10, and a spherically polished diamond surface can be obtained. .
[0066]
As a result, as shown in FIG. 2B, a diamond lens 12 whose surface is finally polished into a spherical shape can be obtained.
[0067]
In the same manner as described above, if the back surface of the substrate made of diamond 10 is also polished as shown in FIG. 4 (a), a diamond lens having both surfaces polished as shown in FIG. 4 (b) It is also possible to obtain 14.
[0068]
One mode of the diamond flattening method of the present invention will be described with reference to FIG.
[0069]
In the mode of such a flattening method, as shown in FIG. 5A, a film 30 having a flat surface made of a material different from diamond is formed on the surface 25 of the diamond 20.
[0070]
As a result, as shown in FIG. 5B, the unevenness existing on the surface 25 of the diamond 20 is buried by the coating 30, and a flat coating surface 35 is obtained. Here, since the film 30 can be formed flat substantially without regard to the irregularities remaining on the surface 25 of the diamond 20, the film thickness of the film 30 differs for each region of the diamond 20.
[0071]
Next, as shown in FIG. 5C, ions are implanted into the diamond 20 (from the side of the coating 30) through the coating 30 having the flat surface 35. As a result, the implanted ions 40 are substantially uniformly introduced over the entire surface of the diamond 20 after passing through the coating 30.
[0072]
At this time, as shown in FIG. 6D, in the region 100 where the thickness of the coating 30 is large, the implanted ions 40 are introduced shallowly into the diamond 20. On the other hand, in the region 105 where the thickness of the coating 30 is small, Implanted ions 40 are introduced deep into diamond 20.
[0073]
As shown in FIG. 6 (e), the portion of the diamond into which the implanted ions 40 have been introduced is damaged or denatured or degraded by the ion bombardment, and becomes amorphous or graphite, for example.
[0074]
Next, the coating 30 is entirely removed from the surface 25 of the diamond 20, and the portion 45 where the diamond has been altered by ion implantation is removed. As a result, as shown in FIG. 6 (f), most of the relatively large unevenness existing on the surface 25 of the diamond 20 is removed as a portion 45 where the diamond is altered, and the smooth surface 26 is exposed.
[0075]
In such a flattening mode, if the desired flatness cannot be obtained on the surface 26 of the diamond 20 in one flattening process, the flattening process described above is repeated one or more times. Thus, the remaining small irregularities can be further flattened, and a diamond having a smoother surface can be obtained.
[0076]
In addition, in accordance with such a mode of flattening the diamond, as shown in FIG. 7A, the surface 25 of the diamond 20 is added with a trace amount of a metal element to thereby prevent the cross section of the diamond from being implanted and the coating against the implanted ion. The coating 31 may be formed so that the blocking cross-sectional area of the coating 31 substantially coincides with the coating 31 to obtain a coating 31 having a flat surface.
[0077]
As a result, as shown in FIG. 7B, the unevenness existing on the surface 25 of the diamond 20 is buried by the coating 31, and a flat coating surface 36 is obtained.
[0078]
Next, as shown in FIG. 7C, ions are implanted into the diamond 20 via the coating 31 having the flattened surface 36. As a result, the implanted ions 40 are substantially uniformly introduced into the entire surface of the diamond 20 after passing through the coating 31.
[0079]
At this time, as shown in FIG. 8D, the blocking cross-section of diamond for the implanted ions and the blocking cross-section of the coating for the implanted ions are substantially the same, so that the implanted ions 40 have the same depth from the coating surface 36. It is efficiently introduced into all areas of the diamond.
[0080]
As a result, as shown in FIG. 8E, the portion of the diamond into which the implanted ions have been introduced at the same depth from the coating surface 36 has its crystal structure destroyed by ion bombardment and changes its quality. Graphite.
[0081]
Next, the coating 31 is entirely removed from the surface of the diamond 20, and the portion 45 where the diamond has been altered by ion implantation is removed.
[0082]
As a result, as shown in FIG. 8 (f), most of the relatively large unevenness existing on the surface 25 of the diamond 20 is removed as a portion 45 where the diamond has been altered. A diamond having a very flat surface 27 can be obtained.
[0083]
Another embodiment of the flattening method of the present invention will be described with reference to FIG. 9 (numerical values in FIG. 9 show an example of the depth of the concave portion on the diamond surface). In this embodiment, when the diamond surface is flattened by the dry method, since the reduction rate of the diamond surface convex portion is relatively larger than the reduction rate of the concave portion of the diamond surface, the diamond is flattened. A diamond surface can be obtained in a short time. In other words, in this embodiment, rather than making the etching rates of different materials the same, rather, by making a positive difference in the reduction rates for the projections and depressions of the diamond surface, a relatively short It is possible to obtain a smooth diamond surface in a short time.
[0084]
In other words, in this embodiment, the projections on the diamond surface are shaved relatively quickly, and the recesses on the surface are shaved relatively slowly. (In other words, since the portion to be shaved is preferentially reduced, ) A very flat surface (eg, R_maxCan be obtained in a relatively short time. More specifically, for example, the difference between the polishing speed or the dry etching speed in sub-μm units is relatively provided between the convex portion and the concave portion on the diamond surface, so that the size of the irregularities (R_max) Can be, for example, about 0.5 μm or less.
[0085]
In this embodiment, the reduction rate (etching rate or polishing rate) of the diamond surface convex portion and the diamond surface concave portion are determined, for example, by the method of Chen et al. (Appl. Phys. Lett.,63 (5), 622 (1993)). In the present embodiment, when the reduction rate of the diamond surface convex portion is C (Å / min) and the reduction rate of the diamond surface concave portion is D (Å / min), the ratio of C / D is usually It is preferably 1.5 or more, more preferably 3.0 or more.
[0086]
Diamond is available from Appl. Phys. Lett. ,63 (5)622 (1993), it becomes brittle when it reacts with metal to form a carbide layer. On the other hand, it is known that when a substance such as boron having a property of compressively straining diamond is added to diamond, the diamond becomes harder. In this embodiment, one or more of these properties of diamond are used to planarize the diamond surface.
[0087]
In the present embodiment, as the dry method, any of a contact (or mechanical) polishing method and / or a dry etching method can be used. However, the dry method is not easily affected by the "warp" of the substrate surface to be flattened. It is preferable to use a dry etching method.
[0088]
As the sacrificial layer, it is preferable to use a film based on spin-on-glass (SOG) or tetraethoxysilane (TEOS). Here, SOG refers to liquid glass in which silicon glass is dissolved or dispersed in a solvent. SOG can be usually solidified by heat treatment at about 200 to 350 ° C. The thickness of the sacrificial layer is preferably about 0.1 to 10.0 μm.
[0089]
In this embodiment, it is preferable that the sacrificial layer is uniformly etched to expose the protrusions on the diamond surface, and then the exposed protrusions are made to adhere with impurities and, if necessary, annealed. As a result, the impurity and the convex portion react with each other to form a reaction layer having a predetermined thickness on the diamond surface to be smoothed.
[0090]
Since such a reaction layer (convex portion) is made of altered or modified diamond, the convex portion can be easily removed by etching or contact polishing.
[0091]
As the impurity, for example, a metal selected from iron, nickel, manganese, cerium, and lanthanum is preferably used. When introducing the impurities, a dry process such as ion implantation or vapor deposition may be used, or a wet process may be used.
[0092]
The above-mentioned annealing is preferably performed in a vacuum at a temperature of 500 to 2000 ° C. for 1 to 30 minutes. A reaction layer having a thickness of about 0.1 to 1 μm can be formed on the diamond surface by reacting the diamond surface protrusions and impurities based on such annealing.
[0093]
In the present embodiment, if necessary, compressive strain may be applied to the concave portion on the diamond surface to reduce the reduction rate of the concave portion. In this case, for example, it is preferable to use a sacrifice layer containing a predetermined amount of impurities as the sacrifice layer, expose the protrusions on the diamond surface and anneal the mixture, and then mix the impurities into the recesses on the diamond surface. As such an impurity, for example, boron is preferably used.
[0094]
Hereinafter, this embodiment will be specifically described with reference to FIG.
[0095]
As shown in FIG. 9A, organic SiO such as spin-on glass is used as a material for forming a sacrificial layer.₂Is used to form a sacrificial layer 52 on the surface of the diamond 51, and the diamond surface is once flattened. At this time, in the case where boron is mixed into the concave portion on the diamond surface, a film (sacrifice layer) containing a large amount of boron may be formed.
[0096]
Next, as shown in FIG. 9B, the spin-on glass 52 is etched back (reduced by etching) using a plasma etching apparatus or the like to expose the diamond convex portion on the surface of the diamond 51. Thereby, it is possible to cause a desired impurity to react only on the convex portion on the surface of the diamond 51.
[0097]
Next, as shown in FIG. 9C, an impurity 53, which is made of a transition metal or the like and reacts with diamond, is applied to the entire surface where the projections are exposed, for example, by vapor deposition or the like. As the transition metal used at this time, iron (Fe) is preferably used, but other transition metals such as Ti, Ni, Mo, and Ce can also be used.
[0098]
Next, as shown in FIG. 9D, annealing is performed in a vacuum or an atmosphere of an inert gas, if necessary, in order to promote the reaction between the diamond and the impurities. Since the reaction temperature varies depending on the impurity, the optimum temperature is determined by the type of the impurity. As a result, the diamond reacts with the impurity in the projection, and the spin-on-glass portion does not react.
[0099]
When a lamp annealing furnace is used during this annealing, the size of the reaction portion in the depth direction can be controlled (for example, between about 0.1 μm and about 1 μm). As a result, it is possible to form a reaction portion only on the very surface portion of the diamond 51.
[0100]
By performing dry etching or contact polishing on the surface of the diamond 51 to which the impurity 53 has been reacted as described above, the convex portion that has reacted with the impurity 53 is reduced quickly (at a reduction rate greater than the concave B). As shown in FIG. 9E, a single-crystal or polycrystalline diamond having a flat surface is obtained.
[0101]
The introduction of the impurities can also be performed using an ion implantation apparatus. In this case, SiO₂Since the portion of the film functions as a mask, the impurity is not implanted into the concave portions on the surface of the diamond 51. Even in the case of using ion implantation as described above, annealing may be performed as necessary to further react the impurity with diamond.
[0102]
When boron is introduced into the concave portion on the diamond surface, boron can be easily mixed as an impurity to the order of%. In addition, fracture of diamond becomes brittle fracture. According to the findings of the present inventor, in this case, it is considered that dislocation does not proceed in a state where a large amount of impurities are mixed. Therefore, a large amount of boron is contained in the sacrificial layer for flattening, and annealing is performed after flattening, so that boron can be selectively mixed into the concave portion. This makes it possible to control the reduction rate of the projections and the depressions, and to obtain a flat surface by short-time etching or polishing.
[0103]
Hereinafter, based on the present inventionReference examples andExamples will be described more specifically.
[0104]
[Reference example]
Reference Example 1
A 10 μm-thick polycrystalline diamond film formed on a 3-inch square silicon substrate was used as the substrate. When the surface roughness was examined, the average surface roughness R_aWas 2000 ° (200 nm).
[0105]
On this substrate, a coating agent (X-Si- (OH)_n) (OCD manufactured by Tokyo Ohka Co., Ltd.) was spin-coated at 2000 rpm, and then baked at 400 ° C. for 30 minutes to form a coating layer. The thickness of the obtained coating layer was 6000 °.
[0106]
The substrate was placed in a dry etching apparatus and etched using Ar gas (100%). The etching rates were all 250 ° / min, and the etching selectivity between the coating layer and diamond was 1: 1. By etching for 40 minutes, the irregularities on the coating layer and the diamond surface were etched to obtain mirror-surface diamond having an average surface roughness Ra of 100 °.
[0107]
Using the diamond substrate thus obtained, a fine pattern of resist was formed on the substrate using an ultraviolet reduction projection exposure machine, and a patterning of 0.5 μm was obtained.
[0108]
Reference Example 2
A 10 μm thick polycrystalline diamond film formed on a 3-inch square silicon substrate was used as the substrate. When the surface roughness was examined, the average surface roughness R_aWas 2000Å.
[0109]
On this substrate, a coating agent (X-Si (OH) n) (OCD manufactured by Tokyo Ohka Kabushiki Kaisha) having an inorganic silicon compound as a main component is spin-coated at 2000 rpm, and then baked at 400 ° C. for 30 minutes to perform coating. A layer was formed. The thickness of the obtained coating layer was 6000 °.
[0110]
This substrate is placed in a dry etching apparatus, and Ar (95%) + O₂(5%) Dry etching was performed using a gas system. The etching rate was 280 ° / min for diamond and 250 ° / min for the coating layer, and the etching selectivity between the coating layer and diamond was 1: 0.9. By etching the irregularities of the coating layer and the diamond layer by etching for 40 minutes, the average surface roughness R_aObtained a mirror diamond of 120 °.
[0111]
Using the diamond substrate thus obtained, a fine pattern of resist was formed on the substrate using an ultraviolet reduction projection exposure machine, and a patterning of 0.5 μm was obtained.
[0112]
Reference Example 3
A 10 μm thick polycrystalline diamond film formed on a 3-inch square silicon substrate was used as the substrate. When the surface roughness was examined, the average surface roughness R_aWas 2000Å.
[0113]
On this substrate, a polyimide containing an organic silicon compound as a main component was spin-coated at 5000 rpm, and then baked at 400 ° C. for 30 minutes to form a coating layer. The thickness of the obtained coating layer was 6000 °.
[0114]
This substrate is placed in a dry etching apparatus, and CF₄Dry etching was performed using gas. The etching rate was 200 ° / min for diamond, 250 ° / min for the coating layer made of polyimide, and the etching selectivity between the coating layer and diamond was 1: 1.25. By etching the unevenness of the coating layer and the diamond layer by etching for 50 minutes, the average surface roughness is R_aObtained a mirror diamond of 120 °.
[0115]
Using the diamond substrate thus obtained, a fine pattern of resist was formed on the substrate using an ultraviolet reduction projection exposure machine, and a patterning of 0.5 μm was obtained.
[0116]
Reference example 4
As shown in FIG. 2A, a 5 mm square diamond 10 (average surface roughness R_a= 2000Å) and a coating agent containing an inorganic silicon compound as a main component (X-Si- (OH)_n) (Manufactured by Tokyo Ohka Co., Ltd.) was dropped, and then baked at 400 ° C. for 30 minutes to form a dome-shaped coating layer 11. The maximum thickness of the obtained coating layer 11 was 6000 °.
[0117]
The diamond 10 was placed in an etching apparatus, and dry etching was performed using a mixed gas of Ar (95%) + O2 (5%). The etching rates were all 250 ° / min, and the etching selectivity between the coating layer and diamond was 1: 1. By etching a part of the surface of the coating layer 11 and the diamond 10 by etching for 40 minutes, the average surface roughness R as shown in FIG._aWas obtained, thereby obtaining a single-sided spherical diamond lens 12 of 100 °.
[0118]
Reference example 5
As shown in FIG. 3A, a 5 mm square diamond 10 (average surface roughness R_a= 2000Å) and a coating agent containing an inorganic silicon compound as a main component (X-Si- (OH)_n) Were dropped in a row, and then baked at 400 ° C. for 30 minutes to form a plurality of dome-shaped coating layers 11. The maximum thickness of the obtained coating layer 11 was 1500 °.
[0119]
The diamond 10 was placed in an etching apparatus, and dry etching was performed using a mixed gas of Ar (95%) + O2 (5%). The etching rates were all 250 ° / min, and the etching selectivity between the coating layer and diamond was 1: 1. By etching the coating layer 11 and a part of the surface of the diamond lens 10 by etching for 10 minutes, the average surface roughness R as shown in FIG._aWas obtained, thereby obtaining a single-sided spherical diamond lens 13 of 100 °.
[0120]
Reference Example 6
Reference example 4A coating agent (X-Si- (OH)) containing an inorganic silicon compound as a main component on the back surface of the single-sided spherical diamond lens 12 obtained in_n) Was dropped, and then baked at 400 ° C. for 30 minutes to form a dome-shaped coating layer 11. The maximum thickness of the obtained coating layer 11 was 6000 °.
[0121]
This substrate is placed in an etching apparatus, and Ar (95%) + O₂Dry etching was performed using a mixed gas of (5%). The etching rates were all 250 ° / min, and the etching selectivity between the coating layer and diamond was 1: 1. By etching for 40 minutes, a part of the back surface of the coating layer 11 and the diamond lens 12 is etched to obtain an average surface roughness R as shown in FIG._aWas obtained.
[0122]
【Example】
Example 1
First, the following three types of substrates made of diamond were prepared (STEP 1).
[0123]
(1) Single crystal diamond synthesized by ultra-high pressure synthesis method polished with diamond powder of # 200 (80-100 μm abrasive)
(2) Single crystal diamond synthesized by ultra-high pressure synthesis and skiff-polished
(3) Polycrystalline diamond formed on Si substrate by vapor phase synthesis
First, the surface roughness of each of the substrates (1) to (3) was measured using a surface roughness meter (for example, manufactured by DEKTAK), and the results are shown in Table 1 below (STEP 1).
[0124]
Next, an appropriate amount of a cyclized rubber-based photoresist agent (trade name: OMR, manufactured by Tokyo Ohka Co., Ltd.) was dropped on the surface of each substrate, and spin-coated with a spinner. The photoresist was dried in the air at a temperature of 110 ° C. for 30 minutes, and a photoresist film having a thickness of about 1 μm was formed (STEP 2). The surface roughness of each of the resist films thus obtained was measured using a surface roughness meter, and the results are shown in Table 1 (STEP 2).
[0125]
Next, using an ion implantation apparatus, Ar ions were implanted from the surface of the resist film formed on each of the above-mentioned substrates (1) to (3) at an acceleration voltage of 50 keV, 500 keV, 1 MeV, and 2 MeV at a dose of 10 ions.^Fifteencm^-2Was implanted. As a result, Ar ions were implanted into the concavities and convexities remaining on the surface of each substrate, and the portion was made amorphous or graphite. After the ion implantation, the resist film was completely removed from each substrate with a stripping agent.
[0126]
Next, the substrate temperature is set to 800 ° C., and the amorphized or graphitized portion is exposed to a plasma of a gas containing hydrogen to remove the amorphized or graphitized portion from each substrate surface. The diamond surface was flattened (STEP 3). The surface roughness of each of the obtained substrates was measured using a surface roughness meter. The measurement results are also shown in Table 1 below (STEP 3).
[0127]
[Table 1]

[0128]
As shown in Table 1 above, the surface roughness of all of the diamond substrates (1) to (3) could be extremely reduced by performing the above-described flattening treatment. That is, it was confirmed that the flattening effect of the flattening process of the present invention was large.
[0129]
Example 2
Example 1Each substrate of (1) to (3) subjected to one flattening process was prepared (STEP 4). Therefore, the following processing was performed on the assumption that the surface roughness of each substrate shown in Table 2 (STEP 4) was equal to the surface roughness of each substrate shown in Table 1 (STEP 3).
[0130]
next,Example 1Similarly, a resist film was formed on each substrate (STEP 5). The surface roughness of each of the obtained resist films was measured. The results obtained are shown in Table 2 below (STEP 5).
[0131]
Next, using an ion implantation apparatus, Ar ions were implanted from the surface of the resist film formed on each of the above-mentioned substrates (1) to (3) at an acceleration voltage of 50 keV, 500 keV, 1 MeV, and 2 MeV at a dose of 10 ions.^Fifteencm^-2Was implanted.
[0132]
After ion implantation,Example 1Similarly to the above, the resist film is entirely removed from each substrate, and the amorphous or graphitized portion is exposed to plasma of a gas containing hydrogen by ion implantation to remove the resist film from the surface of each substrate. Flattening was performed (STEP 6). The surface roughness of each of the obtained substrates was measured. The obtained results are also shown in Table 2 (STEP 6) below.
[0133]
[Table 2]

[0134]
As shown in Table 2 above, by performing the above-described flattening process twice, it is possible to further reduce the surface roughness of each substrate as compared with the case where one flattening process is performed. It turns out that you can.
[0135]
In particular, in this embodiment, the substrate made of polycrystalline diamond having a surface roughness of 2000 ° on the substrate surface is subjected to two flattening treatments to reduce the surface roughness to about 1/10. It was shown that planarization was possible. That is, it was confirmed that the flattening effect was very large.
[0136]
Example 3
Example 1Similarly to (1), each of the substrates (1) to (3) was prepared (STEP 1), and then a resist film was formed on each substrate (STEP 2). Therefore, the surface roughness of each substrate shown in Table 3 (STEP 1) is equal to the surface roughness of each substrate shown in Table 1 (STEP 1), and the surface of each substrate shown in Table 3 (STEP 2) in the resist film. The following treatment was performed on the assumption that the roughness was equal to the surface roughness of the resist film of each substrate shown in Table 1 (STEP 2).
[0137]
Next, using an ion implantation apparatus, Ar ions were formed at a dose of 10 at an acceleration voltage of 50 keV, 500 keV, 1 MeV, and 2 MeV from the surface of the resist film formed on each of the substrates (1) to (3).^Fifteencm^-2Was implanted. After the ion implantation, the resist film was completely removed from each substrate, exposing the surface of each substrate.
[0138]
In the present embodiment, wet etching with chromic acid was performed without using plasma etching when removing a portion where diamond was made amorphous or graphitized by ion implantation from the surface of each substrate.
[0139]
By the above-mentioned wet etching, the amorphous or graphitized portion was removed from the substrate surface, and the diamond surface was flattened (STEP 3). The surface roughness of each of the obtained substrates was measured. The results obtained are shown in Table 3 below (STEP 3).
[0140]
[Table 3]

[0141]
As shown in Table 3, even in the case where the flattening process is performed using wet etching with chromic acid, it is possible to efficiently remove the amorphous or graphitized portion of the diamond from the substrate surface by ion implantation. It was confirmed that the surface roughness of each substrate could be made very small.
[0142]
Example 4
Using only a substrate made of polycrystalline diamond formed on a Si substrate by a vapor phase synthesis method,Example 1The same flattening process was performed. In this embodiment, in order to investigate the effect of the flattening treatment by adding the metal element to the implanted ions, Al, W, Mo, Fe,²⁰cm^-3A photoresist agent (trade name: OMR, manufactured by Tokyo Ohkasha) added and uniformly mixed was used.
[0143]
Example 1Similarly to the above, a resist agent to which each metal element was added or a resist agent to which no metal element was added was spin-coated with a spinner on each substrate to form a resist film (STEP 2). The surface roughness on the surface of the resist film thus obtained was measured, and all were set to 100 ° or less.
[0144]
Next, using an ion implantation apparatus, Ar ions were implanted from the surface of the resist film formed on each substrate at a dose of 10 at an acceleration voltage of 50 keV, 500 keV, 1 MeV, and 2 MeV.^Fifteencm^-2Was used for ion implantation. After ion implantation, the resist film is removed from each substrate, and the amorphous or graphitized parts are exposed to the plasma of a gas containing hydrogen by ion implantation, and removed from each substrate surface to flatten the diamond surface. (STEP 3). The surface roughness of each of the obtained substrates was measured, and the results are shown in Table 4 (STEP 3) below.
[0145]
[Table 4]

[0146]
As shown in Table 4 above, it was confirmed that the use of the resist agent to which the metal element was added could further reduce the substrate surface roughness as compared to the case where the resist agent to which no metal element was added was used. . According to the findings of the present inventor, the uniform addition of the metal element in the resist film makes the blocking cross section of the resist film against Ar ions to be implanted substantially equal to the blocking cross section of each substrate made of diamond. It is presumed that they match.
[0147]
Example 5
Example 4Similarly, using a substrate made of polycrystalline diamond formed on a Si substrate by a vapor phase synthesis method,Example 1The same flattening process was performed.
[0148]
However, in the present embodiment, instead of forming a resist film on the substrate, SiO 2 is formed on the substrate by a sol-gel method.₂A film was formed.
[0149]
Further, in the present embodiment, Al, W, Mo, Fe, and Au were set to 10²⁰cm^-3The added and homogeneously mixed gel was used.
[0150]
First, an SiO-based sol to which a metal element was added or a SiO-based sol to which no metal element was added was spin-coated on each substrate by a spinner. By heating according to the sol-gel method, the SiO-based sol on the substrate is solidified and₂(STEP 2). The SiO thus obtained₂The surface roughness on the surface of the layer was measured and all were set to 100 ° or less.
[0151]
Next, using an ion implantation apparatus, the SiO 2 formed on each substrate was₂From the surface of the layer, Ar ions are dosed at an acceleration voltage of 50 keV, 500 keV, 1 MeV, and 2 MeV to a dose of 10^Fifteencm^-2Was implanted. After ion implantation, SiO₂The layers were all removed from above the substrates by HF treatment, exposing the surface of each substrate. Thereafter, the portion where the diamond was made amorphous or graphitized was exposed to a plasma of a gas containing hydrogen, removed from the surface of each substrate, and planarized (STEP 3). The surface roughness of each of the obtained substrates was measured, and the results are shown in Table 5 (STEP 3) below.
[0152]
[Table 5]

[0153]
As shown in Table 5 above, SiO 2 was deposited on the substrate according to the sol-gel method.₂It was confirmed that the surface roughness of the substrate can be extremely reduced even when the layer is formed and the flattening process is performed. It was also confirmed that the use of sols to which various metal elements were added could further reduce the surface roughness of the substrate. According to the inventor's knowledge, this is a SiO 2₂It is presumed that this is because the blocking cross section of the layer and the blocking cross section of the substrate made of diamond almost match.
[0154]
As mentioned above,Example 4andExample 5Based on the results obtained in step 2, by appropriately setting the type of the metal element to be added to the resist agent and the amount of the metal element to be added to the resist agent according to the type of the ion to be implanted and the implantation conditions, it is possible to perform a single planarization process. It has been found that a substrate having a flatness can be realized.
[0155]
Example 6
Example 4Similarly, using only a substrate made of polycrystalline diamond formed on a Si substrate by a vapor phase synthesis method,Example 1The same flattening process was performed.
[0156]
However, in this example, ion implantation was performed using Ar, Ne, He, Al, Xe, and Cu ions.
[0157]
Example 1Similarly to the above, a resist material was spin-coated on each substrate with a spinner to form a resist film (STEP 2). The surface roughness on the surface of the resist film thus obtained was measured, and all were set to 100 ° or less. Next, using an ion implantation apparatus, doses of Ar, Ne, He, Al, Xe, and Cu ions were respectively accelerated from the surface of the resist film formed on each substrate at an acceleration voltage of 50 keV, 500 keV, 1 MeV, and 2 MeV. Then 10¹⁵cm^-2Was used for ion implantation. After the ion implantation, the resist film is removed from each substrate, and the portion where the diamond is made amorphous or graphitized by the ion implantation is exposed to a plasma of a gas containing hydrogen to remove from the surface of each substrate and planarize. Performed (STEP 3). The surface roughness of each of the obtained substrates was measured, and the results are shown in Table 6 (STEP 3) below.
[0158]
[Table 6]

[0159]
As shown in the above Table 6, the surface roughness of the substrate could be significantly reduced with all types of ions used, and the effect of flattening was confirmed.
[0160]
Example 7
As shown in FIG. 9A, a spin-on glass 52 was applied to a (100) plane single-crystal diamond substrate 51 at a speed of 4000 rotations (rpm) at a thickness of 0.7 μm. Next, in order to sinter the spin-on glass 52, N_TwoAnnealing was performed at 350 ° C. for 20 minutes in an atmosphere.
[0161]
Further, as shown in FIG. 9 (b), using a reactive etching apparatus, CFC gas (CF₄) Spin-on-glass (SiO 2) sintered as above under the conditions of 50 sccm, 13.56 MHz RF power 300 W for 10 minutes.₂) Was etched. As a result, the 0.4 μm spin-on glass was etched back to expose the projection on the diamond surface.
[0162]
As shown in FIG. 9C, 0.2 μm of iron (Fe) was vapor-deposited on the projections thus exposed using an electron beam vapor deposition apparatus.
[0163]
Next, as shown in FIG. 9D, lamp annealing was performed at 1500 ° C. for 10 seconds in an argon gas atmosphere to react the iron with the diamond projections.
[0164]
Further, using a reactive ion etching apparatus, argon (Ar) 80 sccm, oxygen (O₂) Etching was performed for 60 minutes under the conditions of RF power of 300 W at 20 sccm and 13.56 MHz to remove about 0.3 μm of a reaction portion. Under these conditions, the etching rate of the diamond-reacted portion (convex portion) with iron was 10 times faster than the unreacted portion (concave portion). Furthermore, SiO₂Was removed to obtain a smooth diamond surface as shown in FIG. When the smoothness of the diamond surface thus obtained was measured, R_maxWas 0.1 μm or less.
[0165]
As mentioned aboveReference exampleAccording to the method, after forming a flat film made of a material different from the diamond on the surface of the diamond; unevenness of the film and the diamond surface is reduced under a condition that both the diamond and the film can be etched by dry etching. A method of planarizing diamond is provided which removes and smoothes the surface of the diamond.
[0166]
otherReference exampleAccording to the method, after a liquid coating agent containing a material different from the diamond is dropped and cured on the surface of the diamond to form a film having a spherical surface on the diamond; A method for polishing a diamond, characterized in that a surface of the diamond is removed by removing the unevenness of the film and the surface of the diamond under conditions where both can be etched.
[0167]
【The invention's effect】
According to the present inventionUnlike the conventional mechanical polishing such as skiff polishing, the surface can be flattened in a non-contact manner by using the flattening method, so that the material of the substrate, the amount of warpage, the area, the thickness of the substrate, etc. are substantially changed. It is possible to satisfactorily mirror-polish or flatten the surface of various diamonds without any limitation.
[0168]
In the above-described diamond flattening method or polishing method, by using a large-sized dry etching apparatus, it is possible to sufficiently cope with flattening or polishing of a diamond having a larger area.
[0169]
According to such a diamond flattening method or polishing method, a diamond surface with extremely excellent smoothness can be obtained, so that ultra-fine processing at a level impossible on a diamond surface obtained by conventional mechanical polishing is impossible. Can be applied on the diamond surface. Further, according to the present invention, the polishing process is greatly simplified as compared with the conventional mechanical polishing, so that the cost can be efficiently reduced, and a flattening method or a polishing method which has industrially sufficient advantages. Can be provided.
[0170]
Further, by using the above-described diamond polishing method, light can be transmitted in a wavelength range that could not be obtained with materials other than diamond, that is, in an ultraviolet range (wavelength of about 225 nm or less), and has high thermal conductivity and high reliability. It is possible to obtain a diamond lens having a good quality. In particular, the polishing method of the present invention can be suitably applied to microlens formation.
[0171]
Further, according to another aspect of the present invention, a first step of forming a coating made of a material different from that of the diamond on the surface of the diamond and flattening the coating; There is provided a diamond flattening method comprising: a second step of performing ion implantation; and a third step of removing, from the diamond, the diamond portion altered by the ion implantation while removing the coating.
[0172]
Such a flattening method for diamond is suitably applied to the manufacture of electronic optical components (especially, heat dissipation substrates for LSIs and the like that can be used for high-power semiconductor lasers) requiring a stricter flatness of 50 ° or less. can do.
[0173]
Further, according to another aspect of the present invention, when the diamond surface is flattened by a dry method, the diamond cutting speed of the diamond surface convex portion is relatively larger than the diamond cutting portion of the diamond surface. Is provided.
[0174]
According to such a diamond flattening method, it is possible to provide a substrate for an electronic device made of polycrystalline or single-crystal diamond and having a smooth surface.
[Brief description of the drawings]
FIG. 1 is a schematic side sectional view showing one embodiment of the diamond polishing method of the present invention.
FIG. 2 is a schematic side sectional view showing another embodiment of the diamond polishing method of the present invention.
FIG. 3 is a schematic side sectional view showing still another embodiment of the diamond polishing method of the present invention.
FIG. 4 is a schematic side sectional view showing still another embodiment of the diamond polishing method of the present invention.
FIG. 5 is a schematic side sectional view showing one embodiment of the diamond flattening method of the present invention in the order of steps.
FIG. 6 is a schematic side cross-sectional view showing one embodiment of the diamond flattening method of the present invention in the order of steps.
FIG. 7 is a schematic side sectional view showing another embodiment of the diamond flattening method of the present invention in the order of steps.
FIG. 8 is a schematic side sectional view showing another embodiment of the diamond flattening method of the present invention in the order of steps.
FIG. 9 is a schematic side sectional view showing still another embodiment of the diamond flattening method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate, 2,10,20,51 ... Diamond, 3,11,30 ... Coating, 4,20,25 ... Diamond surface, 12,14 ... Diamond lens, 35,36 ... Coating surface, 40 ... Implanted ion, 45: diamond-altered portion, 51: diamond substrate, 52: sacrificial layer, 100: region with a large film thickness, 105: region with a small film thickness.

Claims (12)

When flattening the diamond surface by a dry method, a diamond flattening method in which the reduction rate of the diamond surface convex portion is relatively larger than the reduction rate of the concave portion of the diamond surface ,
A single-crystal or polycrystalline diamond is used as the diamond, a flat sacrificial layer is formed on the diamond, the sacrificial layer is uniformly etched to expose a convex portion on the diamond surface, and impurities are added to the exposed convex portion. A method of flattening diamond, comprising: adhering, annealing, and reacting the impurity with a convex portion, and then removing the convex portion. 2. The method according to claim 1 , wherein a film based on spin-on-glass or tetraethoxysilane (TEOS) is used as the sacrificial layer, and the thickness of the sacrificial layer is 0.1 to 1.0 [mu] m. As the impurity, a metal selected from iron, nickel, manganese, cerium, or lanthanum is used, and annealed in a vacuum at a temperature of 500 to 2000 ° C. for 1 to 30 minutes to cause the diamond surface convex portion to react with the impurity. 2. The method according to claim 1, wherein a reaction layer having a thickness of 0.1 to 1 [mu] m is formed on the diamond surface. A film with a thickness of 0.1 to 1.0 μm based on spin-on-glass or tetraethoxysilane (TEOS) is used as the sacrificial layer , and the impurity is selected from iron, nickel, manganese, cerium, or lanthanum. A reaction layer having a thickness of 0.1 to 1 μm is formed on the diamond surface by using a metal and annealing in a vacuum at a temperature of 500 to 2000 ° C. for 1 to 30 minutes to cause the diamond surface convex portion to react with the impurity. The method of claim 1 wherein the diamond is flattened. The method of claim 1 , wherein a reduction rate of the concave portion is reduced by applying compressive strain to the concave portion on the diamond surface. Using a sacrifice layer containing a predetermined amount of impurities as the sacrifice layer, annealing the sacrifice layer so that the projections on the diamond surface are exposed, and annealing the sacrifice layer to mix the impurities into the depressions on the diamond surface. Item 6. The method for flattening diamond according to Item 5 . 7. The method according to claim 6, wherein boron is used as an impurity contained in the sacrificial layer . A first step of forming a flat film made of a material different from the diamond on the surface of the diamond;
A second step of ion-implanting diamond through the coating;
A third step of removing the coating and removing a diamond portion altered by the ion implantation from the diamond. The method of claim 8 , wherein after the third step, the first step, the second step, and the third step are further sequentially and repeatedly performed. 9. The method according to claim 8 , wherein the coating is made of a resist mainly composed of an organic material. The method according to claim 8 , wherein the coating is a coating formed using a sol-gel method. 9. The diamond planarization according to claim 8 , wherein, in the ion implantation, the coating is formed such that a blocking cross section of the diamond with respect to the implanted ions is substantially equal to a blocking cross section of the coating with respect to the implanted ions. Law.

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