JP3619391B2

JP3619391B2 - Thin film evaluation equipment

Info

Publication number: JP3619391B2
Application number: JP14973599A
Authority: JP
Inventors: 和浩上田; 辰巳平野
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1999-05-28
Filing date: 1999-05-28
Publication date: 2005-02-09
Anticipated expiration: 2019-05-28
Also published as: JP2000338060A

Description

【０００１】
【発明の属する技術分野】
本発明は、薄膜試料のＸ線反射率を２つ以上の波長で測定する薄膜評価装置に関する。
【０００２】
【従来の技術】
従来のＸ線反射率法を用いた薄膜評価装置の概念図を図７に示す。薄膜試料５はＺステージ付き試料支持台６に固定され、２軸回転台７のθ軸上に配置されている。また同軸の２θ軸は、２θアーム８上に配置した分光素子９とＸ線検出器１１を動かす軸となっている。Ｘ線源１で発生したＸ線は、スリット２で成形されて分光素子９で単色化される。単色化されたＸ線は、スリット４で成形されて薄膜試料５に入射し、薄膜試料５で反射されたＸ線はスリット１０で受光範囲が制限され、Ｘ線検出器１１で反射強度を測定していた。測定したＸ線反射率のプロファイルを、Ｐａｒｒａｔｔ［Ｐｈｙｓ．Ｒｅｖ．，９５（１９５４）３５９］やＮｅｖｏｔら［Ｒｅｖ．Ｐｈｙｓ．Ａｐｐｌ．，１５（１９８０）７６１］、Ｓｉｎｈａら［Ｐｈｙｓ．Ｒｅｖ．Ｂ，３８（１９８８）２２９７］が検討した反射率の理論式に従って解析することにより薄膜積層体の、膜厚、密度、界面の幅（ラフネス）が得られる。
【０００３】
また、特開昭６１−１１２９５０号公報には、Ｘ線源で発生したＸ線の光路上に分光結晶、全反射ミラー、Ｘ線検出器の順となるように配置して、測定試料をＸ線源と分光結晶の間、または分光結晶と全反射ミラーの間に設置することで、分光結晶の回折Ｘ線の高調波を除去するＸ線回折法が記載されている。
ところで、近年の半導体デバイスや磁気ヘッド素子の微細化、小型化により、素子を構成する薄膜の極薄膜化、多層膜化が進み、従来のＸ線反射率法では解析困難となってきている。そこで、異常分散を用いたＸ線反射率法が検討された。この方法は、元素のＸ線に対する原子散乱因子（ｆ）が元素の吸収端近傍の波長で大きく変化することを利用して測定精度を向上する手法である。しかし、この方法でも薄膜積層数の増大に伴い解析が困難になっている。
【０００４】
Ｘ線反射率法は、試料表面すれすれにＸ線を入射し、薄膜（表面）で反射されたＸ線強度の入射角依存性から薄膜の情報を得る方法である。入射角を試料表面に対して０．１゜〜２゜の範囲で逐次変えながら、反射Ｘ線の強度を測定するため、Ｘ線の試料表面への入射角度制御が測定精度、再現性、解析精度に大きく影響する。
【０００５】
【発明が解決しようとする課題】
試料表面とＸ線を平行にする作業（以後、軸立て作業と呼ぶ）は、（１）入射Ｘ線の強度が当初の５０％になるように試料をＸ線を遮るように移動（並進）させる工程と、（２）入射Ｘ線と試料表面の法線で構成される散乱面に垂直な軸で試料を回転し、入射Ｘ線強度が最大になる角度に調整する工程を繰り返し、最大強度が当初の５０％で、試料を回転すると強度が減少する様に試料を調整する。この方法は半割り法と呼ばれているが、Ｘ線と試料表面の平行度の精度が０．１゜程度と低い。反割りの後で、入射角／散乱角を全反射角度に移動し、反射Ｘ線強度が最大になるように試料の並進と入射角を調整することにより、入射角を０．０１゜程度の精度で軸立てすることができる。また、淡路ら［特開平７−２６０７１２号公報］は試料を回転させながら、全反射角を測定し、その角度が試料の回転によって変化しないように軸立てする方法を提案している。淡路らはこの方法を用いることにより０．００５゜の精度で軸立てができるとしている。
【０００６】
従来の薄膜評価装置は、図７に示したように、試料５の上流に分光素子９がある。このため波長を切り替える毎に、入射Ｘ線と２軸回転台７の回転中心の位置合わせ、２θの原点決め、試料の軸立ての作業が必要となる。これら作業を慎重に行ったとしても、試料へのＸ線の入射角を０．００５゜の精度で再現するのは極めて難しい。しかも、新しく決めた入射角は、前の波長のときの入射角とは一致しない。複数の波長を用いた測定では、各波長間での入射角ずれ量を０．０００５゜以下で決定する必要が有るため、従来の薄膜評価装置では高精度な測定が困難である。
また、図８に示すように、試料５とＸ線検出器１１の間に分光結晶９を配置した薄膜評価装置もある。この場合、分光素子９が試料５の下流にあるため、入射Ｘ線と２軸回転台７の回転中心の位置合わせ、試料の軸立ての作業が不要となり、各波長間の入射角のずれは無い。
【０００７】
図９は、この装置を用いて試料のＸ線反射率を繰り返し測定した場合の再現性を示す。ＣｏＫβの測定結果１３とＣｕＫβの測定結果１４を同じ図上に示してある。図９の縦軸は反射率の対数である。横軸の表記中、λは波長、θは入射角、Ａはオングストロームである。図示されたＸ線反射率のプロファイル２４〜３７は、反射率測定のため試料にＸ線が照射されていた時間が異なる。反射率測定のために試料にＸ線が照射されていた積算時間は、プロファイル２４が０時間、プロファイル２５が４時間、プロファイル２６が８時間、プロファイル２７が１０時間、プロファイル２８が１２時間、プロファイル２９が１６時間、プロファイル３０が２０時間、プロファイル３１が２４時間、プロファイル３２が２８時間、プロファイル３３が３２時間、プロファイル３４が３４時間、プロファイル３５が３６時間、プロファイル３６が３８時間、プロファイル３７が４０時間である（図は照射時間毎に測定結果を縦方向にずらして表示してある）。
【０００８】
図９の横軸の範囲が０．１５〜０．２５の範囲でＸ線の照射時間が増加するに従って、Ｘ線反射率のプロファイル中に最初無かった振動構造が見えるようになってくる。このように、Ｘ線の照射時間とともに、Ｘ線反射率のプロファイルが変化している。従って、この従来方法でも薄膜の膜厚を高精度で計測するのは困難である。
【０００９】
以上述べたように、従来の薄膜評価装置では、複数の波長を用いて高精度にＸ線反射率を測定することは困難である。本発明は、このような従来技術の問題点に鑑み、Ｘ線の試料への入射角を変化させることなく波長を切り替え可能でかつ、Ｘ線の照射時間とともにＸ線反射率のプロファイルが変化することのない、高精度な薄膜評価が可能な薄膜評価装置を提供することを目的とする。
【００１０】
【課題を解決するための手段】
Ｘ線の照射時間とともにＸ線反射率のプロファイルが変化するのは、薄膜試料がＸ線照射によりダメージを受けるためと考えられる。そこで、Ｘ線の試料への入射角を変化させることなく波長を切り替え可能で、試料へのＸ線照射ダメージが小さいＸ線照射方法、Ｘ線源、試料、分光素子等の配置について検討し、本発明に至った。
【００１１】
すなわち、本発明による薄膜評価装置は、２以上の特性Ｘ線を発生するＸ線源と、θ軸と２θ軸が同軸配置された２軸回転台と、２軸回転台のθ軸に配置された試料支持台と、Ｘ線源と試料支持台の間に配置された全反射Ｘ線反射鏡と、２軸回転台の２θ軸とともに回転可能な分光素子及びＸ線検出器と、２軸回転台及び分光素子を駆動制御する制御部とを備え、全反射Ｘ線反射鏡によって反射されたＸ線源からのＸ線を試料台に保持された薄膜試料に入射させ、薄膜試料で反射されたＸ線を分光素子によって分光したのちＸ線検出器で検出し、薄膜試料のＸ線反射強度をＸ線源の２以上の特性Ｘ線の波長で測定することを特徴とする。
【００１２】
また、本発明による薄膜評価装置は、２以上の特性Ｘ線を発生するＸ線源と、θ軸と２θ軸が同軸配置された２軸回転台と、２軸回転台のθ軸に配置された試料支持台と、Ｘ線源と試料支持台の間に配置された２以上の特性Ｘ線の反射角度が同角度である多層膜Ｘ線反射鏡と、２軸回転台の２θ軸とともに回転可能な分光素子及びＸ線検出器と、２軸回転台及び分光素子を駆動制御する制御部とを備え、多層膜Ｘ線反射鏡によって反射されたＸ線源からのＸ線を試料台に保持された薄膜試料に入射させ、薄膜試料で反射されたＸ線を分光素子によって分光したのちＸ線検出器で検出し、薄膜試料のＸ線反射強度をＸ線源の２以上の特性Ｘ線の波長で測定することを特徴とする。
【００１３】
本発明の薄膜評価装置の制御部は、２軸回転台を駆動制御することによって設定されるＸ線の薄膜試料への入射角度θ、薄膜試料からの散乱角度２θの各測定点で、薄膜試料からのＸ線反射強度をＸ線源の２以上の特性Ｘ線の波長に切り替えて測定するように分光素子を駆動制御することができる。あるいは、本発明の薄膜評価装置の制御部は、Ｘ線源の１つの特性Ｘ線による薄膜試料の反射Ｘ線強度の入射角依存性を測定した後、Ｘ線源の他の特性Ｘ線による薄膜試料の反射Ｘ線強度の入射角依存性を測定するように、分光素子と２軸回転台を駆動制御することができる。
【００１４】
本発明による薄膜評価装置は、Ｘ線源と試料の間に配置した全反射Ｘ線反射鏡あるいは２以上の特性Ｘ線の反射角度が同角度である多層膜Ｘ線反射鏡を用いて、試料にダメージを与える高エネルギーのＸ線を除去している。これにより試料ダメージのない複数の特性Ｘ線を含んだ入射Ｘ線が得られる。この入射Ｘ線を試料に照射し、試料からの反射Ｘ線強度を試料とＸ線検出器の間に配置した分光素子で分光して複数の特性Ｘ線の波長で測定することで、波長を切り替えても、Ｘ線と２軸回転台の回転中心の位置合わせ、試料の軸立ての作業が不要となり、波長毎に入射角が変化することがなくなる。
【００１５】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態を説明する。
〔実施の形態１〕
図１は、本発明による薄膜評価装置の一例を示す装置構成図である。Ｘ線源１で発生したＸ線を、スリット２で幅１００μｍ、高さ１０ｍｍの短冊状に成形し、全反射Ｘ線反射鏡３に照射する。全反射Ｘ線反射鏡３には、表面を平滑に磨いたガラス板を用いた。Ｘ線の全反射Ｘ線反射鏡３への入射角を０．１５゜程度にすることにより、波長がＣｕＫβ以上の長波長の特性Ｘ線は全反射されるが、薄膜試料にダメージを与える高エネルギーのＸ線は全反射Ｘ線反射鏡３を透過あるいは全反射Ｘ線反射鏡３に吸収される。
【００１６】
図２に、全反射Ｘ線反射鏡３への入射前後におけるＸ線の波長分布を示す。図２の上方に示したのは全反射Ｘ線反射鏡３への入射前のＸ線の波長分布、下方に示したのは全反射Ｘ線反射鏡３によって全反射されたＸ線の波長分布である。図２の上下に示したＸ線波長分布を比較すると、全反射Ｘ線反射鏡３で全反射されたＸ線には、Ｘ線源１で発生した高エネルギーのＸ線が含まれていないことが分かる。
【００１７】
図１に戻り、全反射Ｘ線反射鏡３で全反射されたＸ線を、スリット４で幅１００μｍ、高さ５ｍｍに成形し、薄膜試料５に入射する。薄膜試料５で反射されたＸ線は分光素子９に入射して分光され、スリット１０で受光範囲を制限されて、Ｘ線検出器１１で受光される。薄膜試料５はＺステージ付き試料支持台６に固定され、２軸回転台７のθ軸上に配置されている。また、同軸の２θ軸は、２θアーム８上に配置した分光素子９とＸ線検出器１１を動かす軸となっている。２軸回転台７の各軸とＺステージ付き試料支持台６のＺ軸、分光素子９の駆動軸（図示せず）はパルスモータで駆動されており、その制御はドライバー／コントローラ３８を介してコンピュータ３９で行っている。またＸ線検出器１１で計測したＸ線強度は、チャンネルアナライザ（図示せず）を経由してコンピュータ３９に取り込み、その結果をＣＲＴ４０に表示する構成になっている。
【００１８】
この薄膜評価装置は、コンピュータ３９の制御により、２軸回転台７の各軸を駆動して全反射Ｘ線反射鏡３で反射されたＸ線の薄膜試料５への入射角度をθ、薄膜試料５からの散乱角度を２θに設定した各測定点において、分光素子９をＸ線源１の２つ以上の特性Ｘ線の波長に切り替え制御して複数の波長におけるＸ線強度を測定することができる。あるいは、コンピュータ３９の制御により、Ｘ線源１の１つの特性Ｘ線がＸ線検出器１１で検出されるように分光素子９を調整して薄膜試料５で反射されたＸ線強度の入射角依存性を測定した後、Ｘ線源１の別の特性Ｘ線がＸ線検出器１１で検出されるように分光素子９を調整し直して薄膜試料５からの反射Ｘ線強度の入射角依存性を測定することを繰り返すことで、複数の特性Ｘ線の波長でＸ線強度測定を行うこともできる。
【００１９】
図１の装置により、Ｘ線源にＣｕとＣｏの複合ターゲットを用い、ＣｏＫβ及びＣｕＫβを用いて、薄膜試料へのＸ線照射の影響を調べた結果を示すのが図３である。図３には、ＣｏＫβの測定結果１３とＣｕＫβの測定結果１４を合わせて示した。なお、図３は照射時間毎に測定結果を縦方向にずらして表示してある。
Ｘ線照射時間を０時間（図３中のプロファイル１５）、４時間（プロファイル１６）、８時間（プロファイル１７）、１２時間（プロファイル１８）、１６時間（プロファイル１９）、２０時間（プロファイル２０）、２６時間（プロファイル２１）、２８時間（プロファイル２２）と増やしても、どちらの波長とも反射率の入射角依存性に変化がないことがわかる。図９との実験条件の違いは、全反射Ｘ線反射鏡３の有無である。
【００２０】
次に、測定結果を解析することにより、それぞれの波長での入射角ずれ量を求めた。その結果を表１に示す。また比較のため、図７に示した従来の薄膜評価装置を用いて、ＣｕＫβとＣｏＫβの各波長での反射率を測定し、解析結果から入射角のずれ量を求めた。この結果も表１に示す。２波長以上の反射率の解析では横軸を入射角ではなく、散乱ベクトルの大きさで表示する。散乱ベクトルの大きさ（ｑ）は、Ｘ線の入射角をθ、Ｘ線の波長λとすると、ｑ＝（４π／λ）ｓｉｎθの式で計算した。表１の入射角のずれ量は、散乱ベクトルの大きさ（ｑ）で示してある。表１の２波長間の差の欄には、ＣｕＫβの入射角のずれ量からＣｏＫβの入射角のずれ量を引いた値を示した。表中の数値の単位は１／Åである。従来技術では、波長を切り替えたときの入射角のずれ量（２波長間の差）は、入射角でおおよそ０．００１゜相当する。本発明の装置による２波長間の入射角の差は０゜であった。
以上述べたように、本発明によると、薄膜試料に対するＸ線照射ダメージの無い、高精度な多波長Ｘ線反射率測定を行うことのできる薄膜評価装置が得られる。
【００２１】
〔実施の形態２〕
図４は、本発明による薄膜検査装置の別の一例を示す装置構成図である。図４において、図１と同じ機能部分には図１と同じ符号を付して示した。本実施の形態では、Ｘ線反射鏡として、ＷとＣを組み合わせた多層膜Ｘ線反射鏡１２を用いた。多層膜Ｘ線反射鏡１２としては他にＭｏ−Ｓｉを組み合わせた物を検討した。ここでは、ＷとＣを組み合わせた多層膜Ｘ線反射鏡１２を中心に説明する。
【００２２】
図５は、多層膜Ｘ線反射鏡の断面模式図である。多層膜Ｘ線反射鏡１２は、重元素（Ｗ）と軽元素（Ｃ）の膜の膜厚と繰り返し回数で反射するＸ線の波長と反射率、回折の半値幅が決まる。本実施の形態の多層膜Ｘ線反射鏡は、最初にＣｕＫαが約４゜に回折されるＷとＣの膜厚を計算し、Ｓｉ基板上にＷとＣの膜を計算された膜厚だけ成膜する作業を３０回繰り返し、Ｗ／Ｃの膜の組み合わせを３０層成膜した。次に、ＣｕＫβが約４゜で回折されるように計算で求めたＷとＣの膜厚の組み合わせを３０層分、先に作成した多層膜の上に成膜した。これにより、ＣｕＫαが下の３０層の多層膜で４゜に反射され、上の３０層の多層膜でＣｕＫβが４゜に反射される多層膜Ｘ線反射鏡１２ができた。
【００２３】
実施の形態１と同様に、Ｘ線源１で発生したＸ線を、スリット２で１００μｍ、高さ１０ｍｍの短冊状に成形し、多層膜Ｘ線反射鏡１２に照射する。Ｘ線の多層膜Ｘ線反射鏡１２への入射角を４゜程度にすることにより、散乱角８゜の所にＣｕＫβとＣｕＫαの２つの波長のＸ線が反射される。反射されたＸ線をスリット４で幅１００μｍ、高さ５ｍｍに成形し、薄膜試料５に入射する。薄膜試料５は、Ｚステージ付き試料支持台６に固定され、２軸回転台７のθ軸上に配置されている。また同軸の２θ軸は、２θアーム８上に配置した分光素子９とＸ線検出器１１を動かす軸となっている。２軸回転台７の各軸とＺステージ付き試料支持台６のＺ軸、分光素子９の駆動軸（図示せず）はパルスモータで駆動されており、その制御はドライバー／コントローラ３８を介してコンピュータ３９で行っている。また、Ｘ線検出器１１で計測したＸ線強度はチャンネルアナライザ（図示せず）を経由してコンピュータ３９に取り込み、その結果をＣＲＴ４０に表示する構成になっている。
【００２４】
この薄膜評価装置は、コンピュータ３９の制御により、２軸回転台７の各軸を駆動して多層膜Ｘ線反射鏡１２で反射されたＸ線の薄膜試料５への入射角度をθ、薄膜試料５からの散乱角度を２θに設定した各測定点において、分光素子９をＸ線源１の２つ以上の特性Ｘ線の波長に切り替え制御して複数の波長におけるＸ線強度を測定することができる。あるいは、コンピュータ３９の制御により、Ｘ線源１の１つの特性Ｘ線がＸ線検出器１１で検出されるように分光素子９を調整して薄膜試料５で反射されたＸ線強度の入射角依存性を測定した後、Ｘ線源１の別の特性Ｘ線がＸ線検出器１１で検出されるように分光素子９を調整し直して薄膜試料５からの反射Ｘ線強度の入射角依存性を測定することを繰り返すことで、複数の特性Ｘ線の波長でＸ線強度測定を行うこともできる。
【００２５】
図６は、図４に示す装置を用いてＸ線照射の影響を調べた結果である。Ｘ線源にはＣｕとＣｏの複合ターゲットを用い、ＣｕＫβ及びＣｕＫαを用いて調べた結果が図６である。図６には、ＣｕＫβの測定結果１４とＣｕＫαの測定結果２３を合わせて示した（図６も、照射時間毎に測定結果を縦方向にずらして表示してある）。Ｘ線照射時間が０時間（プロファイル１５）、４時間（プロファイル１６）、８時間（プロファイル１７）、１２時間（プロファイル１８）、１６時間（プロファイル１９）、２０時間（プロファイル２０）、２６時間（プロファイル２１）、２８時間（プロファイル２２）と増やしても、どちらの波長とも反射率の入射角依存性に変化がないことがわかる。
【００２６】
次に、測定結果を解析することによりそれぞれの波長での入射角ずれ量を求めた。その結果を表１に示す。また実施の形態１と同様、比較のため、図７に示した従来技術の薄膜評価装置を用いて、ＣｕＫβとＣｕＫαの各波長での反射率を測定し、解析結果から入射角のずれ量を求めた。この結果も表１に示す。２波長以上の反射率の解析では横軸を入射角ではなく、散乱ベクトルの大きさで表示する。散乱ベクトルの大きさ（ｑ）はＸ線の入射角をθ、Ｘ線の波長λとすると、ｑ＝（４π／λ）ｓｉｎθの式で計算した。表１の入射角のずれ量は散乱ベクトルの大きさ（ｑ）で示してある。表１の２波長間の差の欄にはＣｕＫβの入射角のずれ量からＣｏＫβの入射角のずれ量を引いた値を示した。表中の数値の単位は１／Åである。従来技術では、波長を切り替えたときの入射角のずれ量（２波長間の差）は入射角でおおよそ０．００１５゜相当する。本発明を用いた場合の２波長間の入射角の差は０゜であった。
以上述べたように、本発明を用いれば、Ｘ線照射ダメージの無い、高精度な多波長Ｘ線反射率測定ができる薄膜評価装置を得ることができる。
【００２７】
【表１】

【００２８】
【発明の効果】
本発明によれば、Ｘ線源と薄膜試料の間に配置した全反射Ｘ線反射鏡あるいは多層膜Ｘ線反射鏡を用いて、薄膜試料にダメージを与える高エネルギーのＸ線を除去し、薄膜試料ダメージのない複数の特性Ｘ線を含んだ入射Ｘ線が得られる。この入射Ｘ線を用い、薄膜試料からの反射又は回折Ｘ線強度を薄膜試料とＸ線検出器の間に配置した分光素子で複数の特性Ｘ線の波長で測定することで、波長を切り替えても、入射角が変化しない、しかも薄膜試料へのＸ線照射ダメージの無い薄膜評価装置が得られる。
【図面の簡単な説明】
【図１】本発明による薄膜検査装置の一例の構成図。
【図２】全反射Ｘ線反射鏡への入射前後におけるＸ線の波長分布を示す図。
【図３】薄膜試料へのＸ線照射の影響を示す図。
【図４】本発明による薄膜検査装置の別の例の構成図。
【図５】多層膜Ｘ線反射鏡の断面模式図。
【図６】薄膜試料へのＸ線照射の影響を示す図。
【図７】従来の薄膜検査装置の一例の概念図。
【図８】従来の薄膜検査装置の他の例の概念図。
【図９】従来技術で発生するＸ線照射ダメージを説明する図。
【符号の説明】
１…Ｘ線源、２…スリット、３…Ｘ線全反射鏡、４…スリット、５…薄膜試料、６…Ｚステージ付き試料支持台、７…２軸回転台、８…２θアーム、９…分光素子、１０…スリット、１１…Ｘ線検出器、１２…多層膜Ｘ線反射鏡、１３…ＣｏＫβの測定結果、１４…ＣｕＫβの測定結果、３８…ドライバー／コントローラー、３９…コンピューター、４０…ＣＲＴ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film evaluation apparatus that measures the X-ray reflectivity of a thin film sample at two or more wavelengths.
[0002]
[Prior art]
A conceptual diagram of a thin film evaluation apparatus using a conventional X-ray reflectivity method is shown in FIG. The thin film sample 5 is fixed to a sample support 6 with a Z stage, and is arranged on the θ axis of the biaxial rotating table 7. The coaxial 2θ axis is an axis for moving the spectroscopic element 9 and the X-ray detector 11 arranged on the 2θ arm 8. X-rays generated by the X-ray source 1 are shaped by the slit 2 and are monochromatized by the spectroscopic element 9. The monochromatic X-ray is shaped by the slit 4 and incident on the thin film sample 5. The X-ray reflected by the thin film sample 5 is limited in the light receiving range by the slit 10, and the reflection intensity is measured by the X-ray detector 11. Was. The profile of the measured X-ray reflectivity was calculated by using Parratt [Phys. Rev. , 95 (1954) 359] and Nevot et al [Rev. Phys. Appl. , 15 (1980) 761], Sinha et al. [Phys. Rev. B, 38 (1988) 2297], the film thickness, density, and interface width (roughness) of the thin film stack can be obtained by analysis according to the theoretical formula of the reflectance studied by B, 38 (1988) 2297].
[0003]
Japanese Patent Laid-Open No. 61-112950 discloses that a measurement sample is placed in the order of a spectral crystal, a total reflection mirror, and an X-ray detector on the optical path of X-rays generated by an X-ray source. An X-ray diffraction method is described in which the harmonics of the diffracted X-rays of the spectral crystal are removed by being placed between the radiation source and the spectral crystal or between the spectral crystal and the total reflection mirror.
By the way, with recent miniaturization and miniaturization of semiconductor devices and magnetic head elements, the thin films constituting the elements have become extremely thin and multi-layered, and it has become difficult to analyze with the conventional X-ray reflectivity method. Therefore, an X-ray reflectivity method using anomalous dispersion has been studied. This method is a technique for improving the measurement accuracy by utilizing the fact that the atomic scattering factor (f) with respect to the X-ray of the element changes greatly at the wavelength near the absorption edge of the element. However, even with this method, analysis becomes difficult as the number of thin film layers increases.
[0004]
The X-ray reflectivity method is a method for obtaining information on a thin film from incident angle dependence of the X-ray intensity reflected by the thin film (surface) when X-rays are incident on the surface of the sample. In order to measure the intensity of reflected X-rays while sequentially changing the incident angle in the range of 0.1 ° to 2 ° with respect to the sample surface, control of the incident angle of the X-rays on the sample surface provides measurement accuracy, reproducibility, and analysis. The accuracy is greatly affected.
[0005]
[Problems to be solved by the invention]
The work of making the sample surface parallel to the X-ray (hereinafter referred to as pivoting work) is as follows: (1) Move the sample so as to block the X-ray so that the intensity of the incident X-ray is 50% of the original (translation). And (2) rotating the sample about an axis perpendicular to the scattering plane composed of the incident X-ray and the normal of the sample surface, and adjusting the angle to maximize the incident X-ray intensity, Is 50% of the initial value, and the sample is adjusted so that the strength decreases when the sample is rotated. This method is called the half method, but the accuracy of the parallelism between the X-ray and the sample surface is as low as about 0.1 °. After the splitting, the incident angle / scattering angle is moved to the total reflection angle, and the translation angle and the incident angle of the sample are adjusted so that the reflected X-ray intensity is maximized. Can be erected with accuracy. Awaji et al. [Japanese Patent Laid-Open No. 7-260712] proposes a method of measuring the total reflection angle while rotating the sample and setting the angle so that the angle does not change with the rotation of the sample. Awaji et al. Use this method to set the shaft with an accuracy of 0.005 °.
[0006]
The conventional thin film evaluation apparatus has a spectroscopic element 9 upstream of the sample 5 as shown in FIG. For this reason, every time the wavelength is switched, it is necessary to align the incident X-rays with the rotation center of the two-axis rotary table 7, determine the origin of 2θ, and set up the sample. Even if these operations are performed carefully, it is extremely difficult to reproduce the X-ray incident angle on the sample with an accuracy of 0.005 °. Moreover, the newly determined incident angle does not match the incident angle at the previous wavelength. In measurement using a plurality of wavelengths, it is necessary to determine the amount of incident angle deviation between each wavelength to be 0.0005 ° or less. Therefore, it is difficult to perform highly accurate measurement with a conventional thin film evaluation apparatus.
In addition, as shown in FIG. 8, there is a thin film evaluation apparatus in which a spectral crystal 9 is disposed between the sample 5 and the X-ray detector 11. In this case, since the spectroscopic element 9 is downstream of the sample 5, it is not necessary to align the incident X-ray with the rotation center of the biaxial rotating table 7, and to perform the sample pivoting operation. No.
[0007]
FIG. 9 shows reproducibility when the X-ray reflectance of the sample is repeatedly measured using this apparatus. The measurement result 13 of CoKβ and the measurement result 14 of CuKβ are shown on the same figure. The vertical axis in FIG. 9 is the logarithm of reflectance. In the notation on the horizontal axis, λ is the wavelength, θ is the incident angle, and A is angstrom. The X-ray reflectivity profiles 24 to 37 shown in the figure are different from each other in the time when the sample was irradiated with X-rays for the reflectance measurement. The accumulated time during which the sample was irradiated with X-rays for reflectance measurement was as follows: profile 24 was 0 hour, profile 25 was 4 hours, profile 26 was 8 hours, profile 27 was 10 hours, profile 28 was 12 hours, profile 29 for 16 hours, Profile 30 for 20 hours, Profile 31 for 24 hours, Profile 32 for 28 hours, Profile 33 for 32 hours, Profile 34 for 34 hours, Profile 35 for 36 hours, Profile 36 for 38 hours, Profile 37 for 40 hours (the figure shows the measurement result shifted in the vertical direction for each irradiation time).
[0008]
As the X-ray irradiation time increases in the range of the horizontal axis in FIG. 9 in the range of 0.15 to 0.25, a vibration structure that is not present in the X-ray reflectivity profile becomes visible. Thus, the X-ray reflectivity profile changes with the X-ray irradiation time. Therefore, it is difficult to measure the thickness of the thin film with high accuracy even by this conventional method.
[0009]
As described above, with the conventional thin film evaluation apparatus, it is difficult to measure the X-ray reflectivity with high accuracy using a plurality of wavelengths. In the present invention, in view of such problems of the prior art, the wavelength can be switched without changing the incident angle of the X-ray to the sample, and the X-ray reflectance profile changes with the X-ray irradiation time. An object of the present invention is to provide a thin film evaluation apparatus capable of highly accurate thin film evaluation.
[0010]
[Means for Solving the Problems]
The X-ray reflectance profile changes with the X-ray irradiation time because the thin film sample is damaged by the X-ray irradiation. Therefore, the wavelength can be switched without changing the incident angle of the X-ray to the sample, and the arrangement of the X-ray irradiation method, the X-ray source, the sample, the spectroscopic element, etc. with a small X-ray irradiation damage to the sample is examined. The present invention has been reached.
[0011]
That is, the thin film evaluation apparatus according to the present invention is arranged on an X-ray source that generates two or more characteristic X-rays, a two-axis rotary table in which the θ axis and the 2θ axis are coaxially arranged, and the θ axis of the two-axis rotary table. Sample support table, a total reflection X-ray reflector disposed between the X-ray source and the sample support table, a spectroscopic element and an X-ray detector that can rotate with the 2θ axis of the two-axis rotary table, and two-axis rotation And a control unit for driving and controlling the spectroscopic element, the X-ray from the X-ray source reflected by the total reflection X-ray reflecting mirror is incident on the thin film sample held on the sample stage, and is reflected by the thin film sample X-rays are separated by a spectroscopic element and then detected by an X-ray detector, and the X-ray reflection intensity of the thin film sample is measured at two or more characteristic X-ray wavelengths of the X-ray source.
[0012]
The thin film evaluation apparatus according to the present invention is disposed on an X-ray source that generates two or more characteristic X-rays, a two-axis rotary table in which the θ axis and the 2θ axis are coaxially arranged, and the θ axis of the two-axis rotary table. Rotating together with the sample support table, the multilayer X-ray reflector having the same reflection angle of two or more characteristic X-rays arranged between the X-ray source and the sample support table and the 2θ axis of the two-axis rotary table A spectroscopic element and X-ray detector, a two-axis rotary table, and a control unit that drives and controls the spectroscopic element are provided, and the X-ray from the X-ray source reflected by the multilayer X-ray reflecting mirror is held on the sample stage. The X-ray reflected by the thin film sample is dispersed by a spectroscopic element and detected by an X-ray detector, and the X-ray reflection intensity of the thin film sample is measured by two or more characteristic X-rays of the X-ray source. It is measured by wavelength.
[0013]
The control unit of the thin film evaluation apparatus of the present invention is a thin film sample at each measurement point of the incident angle θ of X-rays to the thin film sample and the scattering angle 2θ from the thin film sample set by driving and controlling the biaxial rotating table. The spectroscopic element can be driven and controlled so that the X-ray reflection intensity from the X-ray source is switched to two or more characteristic X-ray wavelengths of the X-ray source. Alternatively, the control unit of the thin film evaluation apparatus of the present invention measures the incident angle dependence of the reflected X-ray intensity of the thin film sample by one characteristic X-ray of the X-ray source, and then uses another characteristic X-ray of the X-ray source. The spectroscopic element and the biaxial rotating table can be driven and controlled so as to measure the incident angle dependence of the reflected X-ray intensity of the thin film sample.
[0014]
A thin film evaluation apparatus according to the present invention uses a total reflection X-ray reflection mirror disposed between an X-ray source and a sample or a multilayer X-ray reflection mirror in which two or more characteristic X-rays have the same reflection angle. High-energy X-rays that cause damage are removed. Thereby, incident X-rays including a plurality of characteristic X-rays without sample damage are obtained. By irradiating the sample with this incident X-ray, the reflected X-ray intensity from the sample is dispersed with a spectroscopic element disposed between the sample and the X-ray detector, and measured at a plurality of characteristic X-ray wavelengths. Even if the switching is performed, it is not necessary to align the X-ray and the rotation center of the two-axis rotary table and to set the sample, and the incident angle does not change for each wavelength.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[Embodiment 1]
FIG. 1 is an apparatus configuration diagram showing an example of a thin film evaluation apparatus according to the present invention. X-rays generated by the X-ray source 1 are formed into a strip shape having a width of 100 μm and a height of 10 mm by the slit 2 and irradiated to the total reflection X-ray reflecting mirror 3. As the total reflection X-ray reflecting mirror 3, a glass plate whose surface was polished smoothly was used. By setting the incident angle of the X-ray to the total reflection X-ray reflecting mirror 3 to about 0.15 °, characteristic X-rays having a long wavelength of CuKβ or more are totally reflected, but the damage to the thin film sample is high. The energy X-rays are transmitted through the total reflection X-ray reflection mirror 3 or absorbed by the total reflection X-ray reflection mirror 3.
[0016]
FIG. 2 shows the wavelength distribution of X-rays before and after incidence on the total reflection X-ray reflecting mirror 3. The upper part of FIG. 2 shows the wavelength distribution of the X-rays before entering the total reflection X-ray reflection mirror 3, and the lower part shows the wavelength distribution of the X-rays totally reflected by the total reflection X-ray reflection mirror 3. It is. Comparing the X-ray wavelength distributions shown in the upper and lower parts of FIG. 2, the X-rays totally reflected by the total reflection X-ray reflecting mirror 3 do not contain high-energy X-rays generated by the X-ray source 1. I understand.
[0017]
Returning to FIG. 1, the X-rays totally reflected by the total reflection X-ray reflecting mirror 3 are formed into a width of 100 μm and a height of 5 mm by the slit 4 and enter the thin film sample 5. The X-ray reflected by the thin film sample 5 enters the spectroscopic element 9 and is dispersed, and the light receiving range is limited by the slit 10 and is received by the X-ray detector 11. The thin film sample 5 is fixed to a sample support 6 with a Z stage, and is arranged on the θ axis of the biaxial rotating table 7. The coaxial 2θ axis is an axis for moving the spectroscopic element 9 and the X-ray detector 11 arranged on the 2θ arm 8. Each axis of the biaxial rotating table 7, the Z axis of the sample support 6 with a Z stage, and the drive shaft (not shown) of the spectroscopic element 9 are driven by a pulse motor, and the control is performed via a driver / controller 38. This is done by computer 39. The X-ray intensity measured by the X-ray detector 11 is taken into the computer 39 via a channel analyzer (not shown), and the result is displayed on the CRT 40.
[0018]
In this thin film evaluation apparatus, under the control of the computer 39, each axis of the biaxial rotary table 7 is driven and the incident angle of the X-rays reflected by the total reflection X-ray reflecting mirror 3 on the thin film sample 5 is set to θ. The X-ray intensity at a plurality of wavelengths can be measured by switching the spectral element 9 to two or more characteristic X-ray wavelengths of the X-ray source 1 at each measurement point where the scattering angle from 5 is set to 2θ. it can. Alternatively, the incident angle of the X-ray intensity reflected by the thin film sample 5 by adjusting the spectroscopic element 9 so that one characteristic X-ray of the X-ray source 1 is detected by the X-ray detector 11 under the control of the computer 39. After measuring the dependency, the spectroscopic element 9 is readjusted so that another characteristic X-ray of the X-ray source 1 is detected by the X-ray detector 11, and the incident X-ray intensity of the reflected X-ray intensity from the thin film sample 5 is adjusted. By repeating the measurement of the X-ray intensity, the X-ray intensity can be measured at a plurality of characteristic X-ray wavelengths.
[0019]
FIG. 3 shows the result of investigating the influence of X-ray irradiation on a thin film sample using the composite target of Cu and Co as the X-ray source and CoKβ and CuKβ. In FIG. 3, the measurement result 13 of CoKβ and the measurement result 14 of CuKβ are shown together. In FIG. 3, the measurement results are displayed while being shifted in the vertical direction for each irradiation time.
X-ray irradiation time is 0 hour (profile 15 in FIG. 3), 4 hours (profile 16), 8 hours (profile 17), 12 hours (profile 18), 16 hours (profile 19), 20 hours (profile 20). It can be seen that there is no change in the incident angle dependence of the reflectance at any wavelength even when the time is increased to 26 hours (profile 21) and 28 hours (profile 22). The difference in experimental conditions from FIG. 9 is the presence or absence of the total reflection X-ray reflecting mirror 3.
[0020]
Next, by analyzing the measurement results, the amount of incident angle deviation at each wavelength was determined. The results are shown in Table 1. For comparison, the reflectance at each wavelength of CuKβ and CoKβ was measured using the conventional thin film evaluation apparatus shown in FIG. 7, and the amount of deviation of the incident angle was obtained from the analysis result. The results are also shown in Table 1. In the analysis of the reflectance of two or more wavelengths, the horizontal axis is displayed not by the incident angle but by the size of the scattering vector. The magnitude (q) of the scattering vector was calculated by the equation q = (4π / λ) sin θ where the incident angle of X-ray is θ and the wavelength of X-ray is λ. The incident angle deviation in Table 1 is indicated by the magnitude (q) of the scattering vector. In the column of the difference between the two wavelengths in Table 1, a value obtained by subtracting the deviation amount of the incident angle of CoKβ from the deviation amount of the incident angle of CuKβ is shown. The unit of numerical values in the table is 1 / Å. In the prior art, the incident angle shift amount (difference between two wavelengths) when the wavelength is switched corresponds to approximately 0.001 ° in terms of the incident angle. The difference in incident angle between the two wavelengths with the apparatus of the present invention was 0 °.
As described above, according to the present invention, a thin film evaluation apparatus capable of performing highly accurate multi-wavelength X-ray reflectivity measurement without X-ray irradiation damage to a thin film sample is obtained.
[0021]
[Embodiment 2]
FIG. 4 is an apparatus configuration diagram showing another example of the thin film inspection apparatus according to the present invention. 4, the same functional parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the present embodiment, a multilayer X-ray reflector 12 combining W and C is used as the X-ray reflector. As the multilayer film X-ray reflecting mirror 12, a combination of Mo-Si was examined. Here, the multilayer X-ray reflecting mirror 12 combining W and C will be mainly described.
[0022]
FIG. 5 is a schematic cross-sectional view of a multilayer X-ray reflecting mirror. The multilayer X-ray reflecting mirror 12 determines the wavelength of X-rays reflected by the film thickness of the heavy element (W) and light element (C) films, the number of repetitions, the reflectance, and the half width of diffraction. In the multilayer X-ray reflecting mirror of the present embodiment, first, the film thickness of W and C at which CuKα is diffracted by about 4 ° is calculated, and the film of W and C is calculated on the Si substrate by the calculated film thickness. The film forming operation was repeated 30 times to form 30 layers of W / C film combinations. Next, 30 combinations of W and C film thicknesses obtained by calculation so that CuKβ was diffracted at about 4 ° were formed on the previously prepared multilayer film. As a result, the multilayer X-ray reflecting mirror 12 in which CuKα is reflected by 4 ° by the lower 30-layer multilayer film and CuKβ is reflected by 4 ° by the upper 30-layer multilayer film is formed.
[0023]
Similar to the first embodiment, X-rays generated by the X-ray source 1 are formed into a strip shape of 100 μm and a height of 10 mm by the slit 2 and irradiated to the multilayer X-ray reflecting mirror 12. By setting the incident angle of the X-rays to the multilayer X-ray reflecting mirror 12 to about 4 °, X-rays having two wavelengths of CuKβ and CuKα are reflected at a scattering angle of 8 °. The reflected X-ray is shaped into a width of 100 μm and a height of 5 mm by the slit 4 and enters the thin film sample 5. The thin film sample 5 is fixed to a sample support base 6 with a Z stage, and is disposed on the θ axis of the biaxial rotating base 7. The coaxial 2θ axis is an axis for moving the spectroscopic element 9 and the X-ray detector 11 arranged on the 2θ arm 8. Each axis of the biaxial rotating table 7, the Z axis of the sample support 6 with a Z stage, and the drive shaft (not shown) of the spectroscopic element 9 are driven by a pulse motor, and the control is performed via a driver / controller 38. This is done by computer 39. The X-ray intensity measured by the X-ray detector 11 is taken into the computer 39 via a channel analyzer (not shown) and the result is displayed on the CRT 40.
[0024]
In this thin film evaluation apparatus, under the control of the computer 39, each axis of the biaxial rotary table 7 is driven and the incident angle of the X-rays reflected by the multilayer X-ray reflecting mirror 12 on the thin film sample 5 is θ, and the thin film sample The X-ray intensity at a plurality of wavelengths can be measured by switching the spectral element 9 to two or more characteristic X-ray wavelengths of the X-ray source 1 at each measurement point where the scattering angle from 5 is set to 2θ. it can. Alternatively, the incident angle of the X-ray intensity reflected by the thin film sample 5 by adjusting the spectroscopic element 9 so that one characteristic X-ray of the X-ray source 1 is detected by the X-ray detector 11 under the control of the computer 39. After measuring the dependency, the spectroscopic element 9 is readjusted so that another characteristic X-ray of the X-ray source 1 is detected by the X-ray detector 11, and the incident X-ray intensity of the reflected X-ray intensity from the thin film sample 5 is adjusted. By repeating the measurement of the X-ray intensity, the X-ray intensity can be measured at a plurality of characteristic X-ray wavelengths.
[0025]
FIG. 6 shows the results of examining the influence of X-ray irradiation using the apparatus shown in FIG. FIG. 6 shows the result of investigation using CuKβ and CuKα using a composite target of Cu and Co as the X-ray source. FIG. 6 shows the measurement result 14 of CuKβ and the measurement result 23 of CuKα together (FIG. 6 also shows the measurement result shifted in the vertical direction for each irradiation time). X-ray irradiation time is 0 hour (profile 15), 4 hours (profile 16), 8 hours (profile 17), 12 hours (profile 18), 16 hours (profile 19), 20 hours (profile 20), 26 hours ( It can be seen that there is no change in the incident angle dependence of the reflectivity for both wavelengths even when the profile 21) and 28 hours (profile 22) are increased.
[0026]
Next, the incident angle deviation amount at each wavelength was obtained by analyzing the measurement result. The results are shown in Table 1. Similarly to the first embodiment, for comparison, the reflectance at each wavelength of CuKβ and CuKα is measured using the conventional thin film evaluation apparatus shown in FIG. Asked. The results are also shown in Table 1. In the analysis of the reflectance of two or more wavelengths, the horizontal axis is displayed not by the incident angle but by the size of the scattering vector. The magnitude (q) of the scattering vector was calculated by the equation q = (4π / λ) sin θ, where θ is the incident angle of X-rays and X is the wavelength λ. The amount of deviation of the incident angle in Table 1 is indicated by the magnitude (q) of the scattering vector. The column of the difference between the two wavelengths in Table 1 shows a value obtained by subtracting the deviation amount of the CoKβ incident angle from the deviation amount of the incident angle of CuKβ. The unit of numerical values in the table is 1 / Å. In the prior art, the incident angle shift amount (difference between two wavelengths) when the wavelength is switched corresponds to approximately 0.0015 ° in terms of the incident angle. The difference in incident angle between the two wavelengths when using the present invention was 0 °.
As described above, by using the present invention, it is possible to obtain a thin film evaluation apparatus capable of highly accurate multi-wavelength X-ray reflectivity measurement without X-ray irradiation damage.
[0027]
[Table 1]

[0028]
【The invention's effect】
According to the present invention, high-energy X-rays that damage a thin film sample are removed using a total reflection X-ray reflecting mirror or a multilayer X-ray reflecting mirror disposed between the X-ray source and the thin film sample, and the thin film Incident X-rays including a plurality of characteristic X-rays without sample damage can be obtained. Using this incident X-ray, the reflection or diffracted X-ray intensity from the thin film sample is measured at a plurality of characteristic X-ray wavelengths with a spectroscopic element arranged between the thin film sample and the X-ray detector, thereby switching the wavelength. However, a thin film evaluation apparatus in which the incident angle does not change and there is no X-ray irradiation damage to the thin film sample can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an example of a thin film inspection apparatus according to the present invention.
FIG. 2 is a view showing the wavelength distribution of X-rays before and after incidence on a total reflection X-ray reflecting mirror.
FIG. 3 is a diagram showing the influence of X-ray irradiation on a thin film sample.
FIG. 4 is a configuration diagram of another example of a thin film inspection apparatus according to the present invention.
FIG. 5 is a schematic sectional view of a multilayer X-ray reflecting mirror.
FIG. 6 is a diagram showing the influence of X-ray irradiation on a thin film sample.
FIG. 7 is a conceptual diagram of an example of a conventional thin film inspection apparatus.
FIG. 8 is a conceptual diagram of another example of a conventional thin film inspection apparatus.
FIG. 9 is a diagram for explaining X-ray irradiation damage that occurs in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray source, 2 ... Slit, 3 ... X-ray total reflection mirror, 4 ... Slit, 5 ... Thin film sample, 6 ... Sample support stand with Z stage, 7 ... Two-axis rotary table, 8 ... 2 (theta) arm, 9 ... Spectroscopic element, 10 ... slit, 11 ... X-ray detector, 12 ... multilayer X-ray reflector, 13 ... CoKβ measurement result, 14 ... CuKβ measurement result, 38 ... driver / controller, 39 ... computer, 40 ... CRT

Claims

An X-ray source that generates two or more characteristic X-rays, a two-axis rotary base in which the θ-axis and the 2θ-axis are coaxially arranged, a sample support base arranged on the θ-axis of the two-axis rotary base, and the X-ray A total reflection X-ray reflecting mirror disposed between a source and the sample support, a spectroscopic element and an X-ray detector which can be rotated together with the 2θ axis of the biaxial rotary table, the biaxial rotary table and the spectroscopic element And a control unit for controlling the drive,
The X-ray from the X-ray source reflected by the total reflection X-ray reflecting mirror is incident on a thin film sample held on the sample stage, and the X-ray reflected by the thin film sample is spectrally separated by the spectroscopic element. A thin film evaluation apparatus characterized by detecting with an X-ray detector and measuring the X-ray reflection intensity of a thin film sample at two or more characteristic X-ray wavelengths of the X-ray source.

An X-ray source that generates two or more characteristic X-rays, a two-axis rotary base in which the θ-axis and the 2θ-axis are coaxially arranged, a sample support base arranged on the θ-axis of the two-axis rotary base, and the X-ray A multilayer X-ray reflector having a reflection angle of two or more characteristic X-rays disposed between a source and the sample support, the spectroscopic element rotatable with the 2θ axis of the two-axis rotary table, and an X-ray A line detector, and a control unit that drives and controls the two-axis rotary table and the spectroscopic element,
X-rays from the X-ray source reflected by the multilayer X-ray reflecting mirror are made incident on a thin film sample held on the sample stage, and the X-rays reflected by the thin film sample are spectrally separated by the spectroscopic element. A thin film evaluation apparatus characterized by detecting with an X-ray detector and measuring the X-ray reflection intensity of a thin film sample at two or more characteristic X-ray wavelengths of the X-ray source.

3. The thin film evaluation apparatus according to claim 1, wherein the control unit includes an incident angle θ of an X-ray set to the thin film sample and a scattering angle 2θ from the thin film sample set by driving and controlling the two-axis rotary table. A thin-film evaluation apparatus that drives and controls the spectroscopic element so as to switch and measure the X-ray reflection intensity from the thin-film sample at two or more characteristic X-ray wavelengths of the X-ray source at each measurement point.

3. The thin film evaluation apparatus according to claim 1, wherein the control unit measures the incident angle dependence of the reflected X-ray intensity of the thin film sample by one characteristic X-ray of the X-ray source, and then determines the X-ray source. A thin-film evaluation apparatus that drives and controls the spectroscopic element and the biaxial rotating table so as to measure the incident angle dependence of the reflected X-ray intensity of a thin-film sample by other characteristic X-rays.