JP3545966B2 - Multilayer thin film composition measurement method - Google Patents
Multilayer thin film composition measurement method Download PDFInfo
- Publication number
- JP3545966B2 JP3545966B2 JP13446699A JP13446699A JP3545966B2 JP 3545966 B2 JP3545966 B2 JP 3545966B2 JP 13446699 A JP13446699 A JP 13446699A JP 13446699 A JP13446699 A JP 13446699A JP 3545966 B2 JP3545966 B2 JP 3545966B2
- Authority
- JP
- Japan
- Prior art keywords
- fluorescent
- rays
- film
- intensity
- ray
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Description
【０００１】
【発明の属する技術分野】
本発明は、励起Ｘ線を試料に照射して、多層薄膜から発生する蛍光Ｘ線を検出することによって、多層薄膜の組成を測定するための多層薄膜組成測定方法に関する。
【０００２】
【従来の技術】
最近、ペロブスカイト系の金属酸化物をシリコンウエハ上に形成して、たとえばＤＲＡＭ（ダイナミックランダムアクセスメモリ）のキャパシタ用誘電体として利用する技術が実用化されつつある。金属酸化物の中でもＢＳＴ｛（Ｂａ，Ｓｒ）ＴｉＯ3 ｝は高い誘電率を示すため、小型で大きな静電容量を形成でき、ギガビット級のＤＲＡＭへの適用が検討されている。こうしたペロブスカイト系誘電体と整合性に優れた電極材料として、同じペロブスカイト系の金属酸化物の中で導電性を示すＳＲＯ（ＳｒＲｕＯ3）の採用が検討されている。
【０００３】
これらのＢＳＴおよびＳＲＯを薄膜として半導体ウエハ上に積層した場合、各薄膜の元素組成の変化が集積回路の特性に大きな影響を与える。また、多成分系金属酸化物の組成は製膜条件の変動によって変化しやすい。そのため製品の品質を安定化するには、薄膜の元素組成を正確に測定することが重要になる。
【０００４】
薄膜の組成を測定する方法として、非破壊的に検査できる蛍光Ｘ線法が有力である。蛍光Ｘ線法は、励起Ｘ線を試料に照射して、試料から発生する蛍光Ｘ線のスペクトルを解析することによって、特性Ｘ線に対応する元素を特定する方法である。
【０００５】
【発明が解決しようとする課題】
試料が基板上に形成された薄膜である場合、励起Ｘ線を照射すると、基板の組成元素および薄膜の組成元素に固有の特性Ｘ線が発生する。たとえば、単層のＢＳＴ膜がＳｉ（シリコン）基板に形成された場合、Ｓｉ基板からＳｉ特性Ｘ線が発生し、ＢＳＴ膜からＢａ（バリウム）特性Ｘ線、Ｓｒ（ストロンチウム）特性Ｘ線およびＴｉ（チタン）特性Ｘ線が発生する。この場合、共通した元素が存在しないため、各特性Ｘ線の分離は容易になる。
【０００６】
しかしながら、ＢＳＴ膜およびＳＲＯ膜から成る多層薄膜がＳｉ基板に形成された場合、Ｓｉ基板からＳｉ特性Ｘ線が発生し、ＢＳＴ膜からＢａ特性Ｘ線、Ｓｒ特性Ｘ線およびＴｉ特性Ｘ線が発生し、ＳＲＯ膜からＳｒ特性Ｘ線およびＲｕ（ルテニウム）特性Ｘ線が発生する。この場合、Ｓｒが両薄膜で共通する元素であるため、Ｓｒ特性Ｘ線がいずれの薄膜に由来するかが特定できないと、各薄膜の組成を正確に決定できない。
【０００７】
本発明の目的は、多層薄膜に共通元素が存在する場合でも、多層薄膜の組成を正確に測定できる多層薄膜組成測定方法を提供することである。
【０００８】
【課題を解決するための手段】
本発明は、互いに共通する元素ＭＢおよび共通しない元素ＭＡ、ＭＣがそれぞれ存在する上層膜および下層膜から成る多層薄膜が表面に形成された基板に向けて励起Ｘ線を照射して、多層薄膜から発生する蛍光Ｘ線を検出することによって多層薄膜の組成を測定する方法であって、
下層膜の共通元素ＭＢおよび非共通元素ＭＣの組成比Ｋｂを特定する工程と、
励起Ｘ線を入射角θL で照射し、多層薄膜から発生する共通元素ＭＢおよび非共通元素ＭＡ、ＭＣの蛍光Ｘ線の各強度を検出する工程と、
前記組成比Ｋｂに基づいて、入射角θL における下層膜由来の共通元素ＭＢおよび非共通元素ＭＣの蛍光Ｘ線の強度比ＩLbを算出する工程と、
前記強度比ＩLbに基づいて、入射角θL における蛍光Ｘ線のうち上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出する工程と、
上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度と非共通元素ＭＡの蛍光Ｘ線の強度との比ＩLtに基づいて、上層膜の共通元素ＭＢおよび非共通元素ＭＡの組成比Ｋｔを算出する工程とを含むことを特徴とする多層薄膜組成測定方法である。
【０００９】
本発明に従えば、励起Ｘ線を多層薄膜に照射した場合、上層膜の共通元素ＭＢからの蛍光Ｘ線、上層膜の非共通元素ＭＡからの蛍光Ｘ線、下層膜の共通元素ＭＢからの蛍光Ｘ線、および下層膜の非共通元素ＭＣからの蛍光Ｘ線が混合して発生する。非共通元素ＭＡ、ＭＣについてはスペクトルが異なるため単独で測定可能となるが、共通元素ＭＢは両方の薄膜に存在するため、共通元素ＭＢの蛍光Ｘ線はどちらの薄膜に由来するかは区別できない。
【００１０】
また、上層膜だけで形成された単膜試料の場合には、共通元素が存在しないため、上層膜の非共通元素ＭＡおよび共通元素ＭＢの組成比と各蛍光Ｘ線の強度比との対応関係は正確に決定できる。同様に、下層膜だけで形成された単膜試料の場合には、共通元素が存在しないため、下層膜の非共通元素ＭＣおよび共通元素ＭＢの組成比と各蛍光Ｘ線の強度比との対応関係は正確に決定できる。
【００１１】
励起Ｘ線を多層薄膜に対して低い入射角θL で照射すると、上層膜でのＸ線吸収が多くなるため、上層膜に由来する蛍光Ｘ線の強度が強くなり、上層膜に関する組成情報量が多くなる。
【００１２】
そこで、低い入射角θL で照射して、下層膜の非共通元素ＭＣからの蛍光Ｘ線の強度を検出して、予め特定しておいた下層膜の組成比Ｋｂを用いることによって、組成比と蛍光Ｘ線強度比との関係が既知であることから、下層膜の共通元素ＭＢだけに由来する蛍光Ｘ線の強度を算出できる。この算出強度分を両膜に由来する共通元素ＭＢの蛍光Ｘ線の強度から引算することによって、上層膜の共通元素ＭＢだけに由来する蛍光Ｘ線の強度を算出できる。
【００１３】
次に、算出した上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を用いて、予め特定しておいた上層膜の非共通元素ＭＡおよび共通元素ＭＢの組成比と各蛍光Ｘ線の強度比との対応関係を参照することによって、上層膜の共通元素ＭＢおよび非共通元素ＭＡの組成比Ｋｔを算出することが可能になる。
【００１４】
なお、下層膜の組成比Ｋｂを特定する方法として、a)下層膜を構成する化合物の化学的組成比をそのまま利用する、b)下層膜だけで作成した単膜試料を定量分析した結果を利用する、などが可能である。
【００１５】
また、非共通元素ＭＡ、ＭＣおよび共通元素ＭＢがそれぞれ複数存在する場合は、特定の元素に絞り込むことによって本発明を適用できる。
【００１６】
また本発明は、励起Ｘ線を入射角θH (θH＞θL)で照射し、多層薄膜から発生する共通元素ＭＢおよび非共通元素ＭＡ、ＭＣの蛍光Ｘ線の各強度を検出する工程と、
前記組成比Ｋｔに基づいて、入射角θH における上層膜由来の共通元素ＭＢおよび非共通元素ＭＡの蛍光Ｘ線の強度比ＩHtを算出する工程と、
前記強度比ＩHtに基づいて、入射角θH における蛍光Ｘ線のうち下層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出する工程と、
下層膜由来の共通元素ＭＢの蛍光Ｘ線の強度と非共通元素ＭＣの蛍光Ｘ線の強度との比ＩHbに基づいて、下層膜の共通元素ＭＢおよび非共通元素ＭＣの組成比Ｋｂを新たに算出する工程とを含むことを特徴とする。
【００１７】
本発明に従えば、入射角θL より高い入射角θH で照射して、多層薄膜から発生する共通元素ＭＢおよび非共通元素ＭＡ、ＭＣの蛍光Ｘ線の各強度を検出して、入射角θL での照射によって算出した組成比Ｋｔを用いることによって、組成比と蛍光Ｘ線強度比との関係が既知であることから、上層膜由来の共通元素ＭＢおよび非共通元素ＭＡの蛍光Ｘ線の強度比ＩHtを算出できる。この強度比ＩHtから下層膜の共通元素ＭＢだけに由来する蛍光Ｘ線の強度を算出できる。
【００１８】
次に、算出した下層膜由来の共通元素ＭＢの蛍光Ｘ線の強度と非共通元素ＭＣの蛍光Ｘ線の強度との比ＩHbを用いて、組成比と蛍光Ｘ線強度比との関係が既知であることから、下層膜の共通元素ＭＢおよび非共通元素ＭＣの組成比Ｋｂを新たに算出できる。
【００１９】
励起Ｘ線を多層薄膜に対して高い入射角θH (θH＞θL)で照射すると、上層膜でのＸ線吸収が少なくなるため、下層膜に由来する蛍光Ｘ線の強度が強くなり、下層膜に関する組成情報量が増加する。そのため、下層膜の組成比Ｋｂを測定する精度がより向上することになる。
【００２０】
こうして算出した組成比Ｋｂを新たな既定値として採用して、上述した各算出工程、すなわち入射角θL における下層膜由来の蛍光Ｘ線の強度比ＩLbを算出する工程、上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出する工程、および上層膜の組成比Ｋｔを算出する工程を繰り返すことによって、組成比Ｋｔの測定精度をより向上させることができる。得られた組成比Ｋｔは新たな既定値として採用して、上述した各算出工程、すなわち入射角θH における上層膜由来の蛍光Ｘ線の強度比ＩHtを算出する工程、入射角θH における下層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出する工程、および下層膜の組成比Ｋｂを算出する工程を繰り返すことによって、組成比Ｋｂの測定精度をより向上させることができる。また、こうした回帰計算による精度向上が可能になるため、初期値としての組成比Ｋｂの精度を緩和することができる。
【００２１】
また本発明は、上層のＢＳＴ膜および下層のＳＲＯ膜から成る多層薄膜が表面に形成されたシリコン基板に向けて励起Ｘ線を照射して、多層薄膜から発生する蛍光Ｘ線を検出することによって多層薄膜の組成を測定する方法であって、
ＳＲＯ膜のＳｒ、Ｒｕの組成比ＫSRを特定する工程と、
励起Ｘ線を低い入射角θL で照射し、多層薄膜から発生するＢａ、Ｓｒ、Ｔｉ、Ｒｕの蛍光Ｘ線ＸBa、ＸSr、ＸTi、ＸRuの各強度を検出する工程と、
前記組成比ＫSRに基づいて、入射角θL におけるＳＲＯ膜由来の蛍光Ｘ線ＸSr、ＸRuの強度比ＩLSR を算出する工程と、
前記強度比ＩLSRに基づいて、入射角θL における蛍光Ｘ線ＸSrのうちＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度を算出する工程と、
ＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度と蛍光Ｘ線ＸBa、ＸTiとの比ＩLSBTに基づいて、ＢＳＴ膜のＢａ、Ｓｒ、Ｔｉの組成比ＫBST を算出する工程とを含むことを特徴とする多層薄膜組成測定方法である。
【００２２】
本発明に従えば、励起Ｘ線を多層薄膜に照射した場合、上層のＢＳＴ膜の共通元素であるＳｒからの蛍光Ｘ線ＸSr、ＢＳＴ膜の非共通元素であるＢａ、Ｔｉからの蛍光Ｘ線ＸBa、ＸTi、下層のＳＲＯ膜の共通元素であるＳｒからの蛍光Ｘ線ＸSr、およびＳＲＯ膜の非共通元素であるＲｕからの蛍光Ｘ線ＸRuが混合して発生する。非共通元素Ｂａ、Ｔｉ、Ｒｕについてはスペクトルが異なるため単独で測定可能となるが、共通元素Ｓｒは両方の薄膜に存在するため、蛍光Ｘ線ＸSrはどちらの薄膜に由来するかは区別できない。
【００２３】
また、ＢＳＴ膜だけで形成された単膜試料の場合には、共通元素が存在しないため、ＢＳＴ膜のＢａ、Ｓｒ、Ｔｉの組成比と各蛍光Ｘ線ＸBa、ＸSr、ＸTiの強度比との対応関係は正確に決定できる。同様に、ＳＲＯ膜だけで形成された単膜試料の場合には、共通元素が存在しないため、ＳＲＯ膜のＳｒ、Ｒｕの組成比と各蛍光Ｘ線ＸSr、ＸRuの強度比との対応関係は正確に決定できる。
【００２４】
励起Ｘ線を多層薄膜に対して低い入射角θL で照射すると、上層のＢＳＴ膜でのＸ線吸収が多くなるため、ＢＳＴ膜に由来する蛍光Ｘ線の強度が強くなり、ＢＳＴ膜に関する組成情報量が多くなる。
【００２５】
そこで、低い入射角θL で照射して、ＳＲＯ膜のＲｕからの蛍光Ｘ線ＸRuの強度を検出して、予め特定しておいたＳＲＯ膜の組成比ＫSRを用いることによって、組成比と蛍光Ｘ線強度比との関係が既知であることから、ＳＲＯ膜のＳｒだけに由来する蛍光Ｘ線ＸSrの強度を算出できる。この算出強度分を両膜に由来する蛍光Ｘ線ＸSrの強度から引算することによって、ＢＳＴ膜のＳｒだけに由来する蛍光Ｘ線ＸSrの強度を算出できる。
【００２６】
次に、算出したＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度を用いて、予め特定しておいたＢＳＴ膜のＢａ、Ｓｒ、Ｔｉの組成比と各蛍光Ｘ線ＸBa、ＸSr、ＸTiの強度比との対応関係を参照することによって、ＢＳＴ膜の組成比ＫBST を算出することが可能になる。
【００２７】
なお、ＳＲＯ膜の組成比ＫSRを特定する方法として、a)ＳＲＯ化合物のＳｒ、Ｒｕの化学的組成比１：１をそのまま利用する、b)ＳＲＯ膜だけで作成した単膜試料を定量分析した結果を利用する、などが可能である。
【００２８】
また本発明は、励起Ｘ線を入射角θH (θH＞θL)で照射し、多層薄膜から発生するＢａ、Ｓｒ、Ｔｉ、Ｒｕの蛍光Ｘ線ＸBa、ＸSr、ＸTi、ＸRuの各強度を検出する工程と、
前記組成比ＫBST に基づいて、入射角θH におけるＢＳＴ膜由来の蛍光Ｘ線ＸBa、ＸSr、ＸTiの強度比ＩHBSTを算出する工程と、
前記強度比ＩHBSTに基づいて、入射角θH における蛍光Ｘ線のうちＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度を算出する工程と、
ＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度と蛍光Ｘ線ＸRuの強度との比ＩHSR に基づいて、ＳＲＯ膜のＳｒ、Ｒｕの組成比ＫSRを新たに算出する工程とを含むことを特徴とする。
【００２９】
本発明に従えば、入射角θL より高い入射角θH で照射して、多層薄膜から発生するＢａ、Ｓｒ、Ｔｉ、Ｒｕの蛍光Ｘ線ＸBa、ＸSr、ＸTi、ＸRuの各強度を検出して、入射角θL での照射によって算出した組成比ＫBST を用いることによって、組成比と蛍光Ｘ線強度比との関係が既知であることから、ＢＳＴ膜由来の蛍光Ｘ線ＸBa、ＸSr、ＸTiの強度比ＩHBSTを算出できる。この強度比ＩHBSTからＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度を算出できる。
【００３０】
次に、算出したＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度と蛍光Ｘ線ＸRuの強度との比ＩHSR を用いて、組成比と蛍光Ｘ線強度比との関係が既知であることから、ＳＲＯ膜の組成比ＫSRを新たに算出できる。
【００３１】
励起Ｘ線を多層薄膜に対して高い入射角θH (θH＞θL)で照射すると、上層のＢＳＴ膜でのＸ線吸収が少なくなるため、下層のＳＲＯ膜に由来する蛍光Ｘ線の強度が強くなり、ＳＲＯ膜に関する組成情報量が増加する。そのため、ＳＲＯ膜の組成比ＫSRを測定する精度がより向上することになる。
【００３２】
こうして算出した組成比ＫSRを新たな既定値として採用して、上述した各算出工程、すなわち入射角θL におけるＳＲＯ膜由来の蛍光Ｘ線の強度比ＩLSR を算出する工程、ＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度を算出する工程、およびＢＳＴ膜の組成比ＫBST を算出する工程を繰り返すことによって、組成比ＫBST の測定精度をより向上させることができる。得られた組成比ＫBST は新たな既定値として採用して、上述した各算出工程、すなわち入射角θH におけるＢＳＴ膜由来の蛍光Ｘ線の強度比ＩHBSTを算出する工程、入射角θH におけるＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度を算出する工程、およびＳＲＯ膜の組成比ＫSRを算出する工程を繰り返すことによって、組成比ＫSRの測定精度をより向上させることができる。また、こうした回帰計算による精度向上が可能になるため、初期値としての組成比ＫSRの精度を緩和することができる。
【００３３】
また本発明は、励起Ｘ線として単色化されたＸ線を使用することを特徴とする。
【００３４】
本発明に従えば、励起Ｘ線の入射角度が低くなるほど、上層膜におけるＸ線通過距離が長くなる。励起Ｘ線が通過して元の強度が一定値まで減衰するまでの距離を規定した実効消衰長さは、Ｘ線エネルギ（波長）および媒体を構成する元素によって変化する。そのため上層膜におけるＸ線通過距離が長くなるほど、励起Ｘ線のエネルギ分布の影響が測定誤差として現われるため、この対策として励起Ｘ線を単色化することが好ましい。
【００３５】
【発明の実施の形態】
図１は、本発明に係る蛍光Ｘ線分析装置を示す構成図である。蛍光Ｘ線分析装置は、ビーム状のＸ線を発生するＸ線源１と、Ｘ線源１からのＸ線の中から単一の特性Ｘ線を分離して単色化するための分光結晶２と、分光結晶２によって所定方向に回折したＸ線を取出すためのスリット部材３と、試料ＳＰのうち励起Ｘ線Ｘ１が照射された部分から発生する蛍光Ｘ線を検出するためのＸ線検出器４と、試料ＳＰを保持するための試料保持機構５などで構成される。試料保持機構５は、試料ＳＰの角度および３次元位置を調整することができ、これによって励起Ｘ線の入射角θおよび照射領域を変化できる。Ｘ線検出器４は、エネルギー分散型または波長分散型の検出器が用いられる。
【００３６】
本発明が適用される試料ＳＰは、非共通元素ＭＡおよび共通元素ＭＢを含む上層膜と共通元素ＭＢおよび非共通元素ＭＣを含む下層膜とから成る多層薄膜が基板の上に形成されたもので、ここでは上層のＢＳＴ膜および下層のＳＲＯ膜から成る多層薄膜が形成されたシリコンウエハを例示する。
【００３７】
次に本発明の原理について説明する。まず単層膜の組成を測定する方法について説明する。励起Ｘ線を高い入射角θで照射する場合、単層膜の各元素の蛍光Ｘ線強度は次式（１）で表される。ここで、Ｉzは元素Ｚの蛍光Ｘ線強度、ｋzは元素Ｚの装置感度係数、Ｃzは元素Ｚの含有率（質量比）、ρは膜の密度、ｔは膜の厚さである。
Ｉz＝ ｋz・Ｃz・ρ・ｔ …（１）
【００３８】
このとき単層膜が充分に薄い膜である場合、膜による励起Ｘ線の吸収および蛍光Ｘ線の吸収は無視できる。組成分析だけを目的とする場合には、他の任意の元素ＺO との相対比較によって、次式（２）のようにパラメータを減らすことができる。
Ｉz／Ｉzo ＝ （ｋz・Ｃz）／（ｋzo・Ｃzo） …（２）
【００３９】
ここで、組成Ｃzが全ての元素について既知である参照試料を用意し、全ての元素の蛍光Ｘ線強度Ｉzを測定すれば、相対的な装置感度係数を次式（３）のように求められる。ここで、Ｉz,R は参照試料中の元素Ｚの蛍光Ｘ線強度、Ｃz,R は参照試料中の元素Ｚの含有率（質量比）である。
ｋz／ｋzo ＝ （Ｉz,R・Ｃzo,R）／（Ｉzo,R・Ｃz,R） …（３）
【００４０】
こうして装置感度係数を求めておけば、未知試料についても蛍光Ｘ線強度を測定することによって、組成Ｃzは次の連立方程式（４）（５）を解くことによって求められる。
Ｃzo ／Ｃz＝ （ｋz・Ｉzo）／（ｋzo・Ｉz） …（４）
ΣＣz＝ １ （元素Ｚに関する総和＝１） …（５）
【００４１】
次に斜入射法を用いた場合には一般的に次式（６）（７）が成立する。ここで、ｄz、ｄzo は元素Ｚ、ＺO に対応する励起Ｘ線の実効消衰長さである。
Ｉz＝ ｋz・Ｃz・ρ・ｄz …（６）
Ｉzo ＝ ｋzo・Ｃzo・ρ・ｄzo …（７）
【００４２】
ｄz、ｄzo は膜による励起Ｘ線の吸収によって決定される。なお、膜による蛍光Ｘ線の吸収は無視している。上述した高角度入射法の式（２）と同様に元素Ｚ、ＺO の蛍光Ｘ線強度比は次式（８）のように求められる。
Ｉz／Ｉzo ＝ （ｋz・Ｃz・ｄz）／（ｋzo・Ｃzo・ｄzo） …（８）
【００４３】
そこで、ｄz／ｄzoの要素だけが高角度入射法と相違するが、励起Ｘ線を単色化することによって、ｄz／ｄzo＝１となって式（２）と一致する。したがって、単色化された励起Ｘ線を使用すれば、斜入射法でも高角度入射法と同様な計算式を使用することができ、算出工程の簡素化が図られる。
【００４４】
次に多層膜の組成を測定する方法について説明する。
図２は励起Ｘ線Ｘ１を低い入射角θL で入射したときの説明図であり、図３は励起Ｘ線Ｘ１を高い入射角θH(θH＞θL) で入射したときの説明図である。測定試料は上層のＢＳＴ膜および下層のＳＲＯ膜から成る多層薄膜が形成されたシリコンウエハである。
【００４５】
まず図２のように、励起Ｘ線Ｘ１の入射角θL を充分に低い角度、たとえば０．１度に設定して照射すると、上層のＢＳＴ膜からＢａ、Ｓｒ、Ｔｉの蛍光Ｘ線ＸBa、ＸSr、ＸTiが比較的強く発生し、下層のＳＲＯ膜からＳｒ、Ｒｕの蛍光Ｘ線ＸSr、ＸRuが弱く発生する。このとき、ＳｒがＢＳＴ膜およびＳＲＯ膜の両方に存在するため、検出した蛍光Ｘ線ＸSrがどちらの膜に由来するかは区別できない。
【００４６】
一般に、２層構成の薄膜にＸ線を斜入射させた場合、検出される蛍光Ｘ線強度は次式（９）〜（11）のように記述できる。ここで、Ｉ1,z、Ｉ2,zは第１層、第２層からの元素Ｚの蛍光Ｘ線強度、Ｃ1,z、Ｃ2,zは第１層、第２層の元素Ｚの含有率（質量比）、ρ1、ρ2は第１層、第２層の膜の密度、ｄ1、ｄ2は第１層、第２層での励起Ｘ線の実効消衰長さ、 Ｔ1 は第１層の励起Ｘ線の透過率である。
Ｉz＝ Ｉ1,z＋ Ｉ2,z …（９）
Ｉ1,z＝ ｋz・Ｃ1,z・ρ1・ｄ1 …（10）
Ｉ2,z＝ Ｔ1・ｋz・Ｃ2,z・ρ2・ｄ2 …（11）
【００４７】
単層膜の場合と同様に、蛍光Ｘ線量についてある元素の蛍光Ｘ線量を基準とした相対比較によって、式（10）（11）は次式（12）（13）のように簡略化できる。
Ｉ1,z／Ｉ1,z1 ＝ （ｋz・Ｃ1,z）／（ｋzo・Ｃ1,zo） …（12）
Ｉ2,z／Ｉ2,z2 ＝ （ｋz・Ｃ2,z）／（ｋzo・Ｃ2,zo） …（13）
【００４８】
次に上記式をＢＳＴ膜およびＳＲＯ膜から成る多層薄膜に適用する。
ＩBa ＝ Ｉ1,Ba …（14）
ＩSr ＝ Ｉ1,Sr ＋ Ｉ2,Sr …（15）
ＩTi ＝ Ｉ1,Ti …（16）
ＩRu ＝ Ｉ2,Ru …（17）
Ｉ1,Ba ／Ｉ1,Sr ＝ （ｋBa・Ｃ1,Ba）／（ｋSr・Ｃ1,Sr） …（18）
Ｉ1,Ti ／Ｉ1,Sr ＝ （ｋTi・Ｃ1,Ti）／（ｋSr・Ｃ1,Sr） …（19）
Ｉ2,Sr ／Ｉ2,Ru ＝ （ｋSr・Ｃ2,Sr）／（ｋRu・Ｃ2,Ru） …（20）
【００４９】
式（15）（17）（20）からＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度Ｉ1,Srが求まる。
ここで、ＩSr、ＩRuが観測量であり、ｋSr／ｋRuはＳＲＯ膜の単層膜試料を測定することによって決定できる。したがって、ＳＲＯ膜の組成比Ｃ2,Sr／Ｃ2,Ruが判れば、ＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度Ｉ2,Srが決定され、最終的にＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度Ｉ1,Srを求めることができる。
【００５１】
この計算で使用するＳＲＯ膜の組成比Ｃ2,Sr／Ｃ2,Ruとして、標準的な化学的組成比１：１を採用できる。その理由として、励起Ｘ線を低角度で入射した場合、励起Ｘ線は上層のＢＳＴ膜でほとんど吸収され、ＢＳＴ膜の励起Ｘ線の透過率Ｔ1 は極めて小さな値となり、ＢＳＴ膜由来の蛍光Ｘ線強度Ｉ1,Srに比べてＳＲＯ膜由来の蛍光Ｘ線強度Ｉ2,Srは１００分の１程度しかない。したがって、組成比Ｃ2,Sr／Ｃ2,Ruの設定値に、たとえば１０分の１の誤差が含まれていても強度Ｉ1,Srの計算結果に１０００分の１程度の誤差を及ぼすだけに過ぎない。さらに、後述するようにＳＲＯ膜の測定結果を用いて逐次的に精密化することも可能である。
【００５２】
こうして上層のＢＳＴ膜から発生する蛍光Ｘ線ＸBa、ＸSr、ＸTiの発生量が判れば、単層膜の場合と同様にＢＳＴ膜の組成を算出できる。このとき使用するｋBa／ｋSrおよびｋTi／ｋSrはＢＳＴ膜の単層膜試料を測定することによって決定できる。
【００５３】
次に下層のＳＲＯ膜の組成測定について説明する。図３のように、励起Ｘ線Ｘ１の入射角θH を充分に高い角度、たとえば２度に設定して照射すると、上層のＢＳＴ膜からＢａ、Ｓｒ、Ｔｉの蛍光Ｘ線ＸBa、ＸSr、ＸTiが発生し、下層のＳＲＯ膜からＳｒ、Ｒｕの蛍光Ｘ線ＸSr、ＸRuが入射角θL より強く発生する。このとき、ＳｒがＢＳＴ膜およびＳＲＯ膜の両方に存在するため、検出した蛍光Ｘ線ＸSrがどちらの膜に由来するかは区別できない。
【００５４】
一般に、２層構成の薄膜にＸ線を高角度で入射させた場合、検出される蛍光Ｘ線強度は式（９）〜（11）と同様に次式（22）〜（24）のように記述できる。ここで、ｔ1、ｔ2は第１層、第２層の膜厚である。また、第１層、第２層での励起Ｘ線および蛍光Ｘ線の吸収は通過距離が短いため無視できる。
Ｉz＝ Ｉ1,z＋ Ｉ2,z …（22）
Ｉ1,z＝ ｋz・Ｃ1,z・ρ1・ｔ1 …（23）
Ｉ2,z＝ ｋz・Ｃ2,z・ρ2・ｔ2 …（24）
【００５５】
単層膜の場合と同様に、蛍光Ｘ線量についてある元素の蛍光Ｘ線量を基準とした相対比較によって、式（23）（24）は次式（25）（26）のように簡略化できる。
Ｉ1,z／Ｉ1,z1 ＝ （ｋz・Ｃ1,z）／（ｋzo・Ｃ1,zo） …（25）
Ｉ2,z／Ｉ2,z2 ＝ （ｋz・Ｃ2,z）／（ｋzo・Ｃ2,zo） …（26）
【００５６】
次に上記式をＢＳＴ膜およびＳＲＯ膜から成る多層薄膜に適用する。
ＩBa ＝ Ｉ1,Ba …（27）ＩSr ＝ Ｉ1,Sr ＋ Ｉ2,Sr …（28）
ＩTi ＝ Ｉ1,Ti …（29）
ＩRu ＝ Ｉ2,Ru …（30）
Ｉ1,Ba ／Ｉ1,Sr ＝ （ｋBa・Ｃ1,Ba）／（ｋSr・Ｃ1,Sr） …（31）
Ｉ1,Ti ／Ｉ1,Sr ＝ （ｋTi・Ｃ1,Ti）／（ｋSr・Ｃ1,Sr） …（32）
Ｉ2,Sr ／Ｉ2,Ru ＝ （ｋSr・Ｃ2,Sr）／（ｋRu・Ｃ2,Ru） …（33）
【００５７】
式（31）（32）を変形するとＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度Ｉ1,Srが求まる。
【００５８】
【数１】
このような計算方法の他に、たとえば式（31）を用いて次式（36）（37）のように強度Ｉ1,Srを求めることも可能である。
Ｉ1,Ba ／Ｉ1,Sr ＝ （ｋBa・Ｃ1,Ba）／（ｋSr・Ｃ1,Sr） …（36）
Ｉ1,Sr ＝ （Ｉ1,Ba・ｋSr・Ｃ1,Sr）／（ｋBa・Ｃ1,Ba） …（37）
【００６０】
測定精度に関して、測定する蛍光Ｘ線強度の強い方が高いＳ／Ｎ比を確保できる。また蛍光Ｘ線ＸBa、ＸTiの強度を測定する際、たとえばＢａ−Ｌ特性Ｘ線とＴｉ−Ｋ特性Ｘ線を用いた場合は両者のピークが近接しているという事情がある。これらの蛍光Ｘ線強度の和をピーク分離せずに求めた場合は、どちらか一方をピーク分離して求める場合よりも格段に安定した測定が可能になる。こうした事情がある場合には、式（35）を用いる方法が好ましいことになる。
【００６１】
そこで、式（28）（35）を用いて、ＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度Ｉ2,Srが求まる。
【００６２】
【数２】
ここで、ＩSr、ＩBa、ＩTiが観測量であり、ｋBa／ｋSr、ｋTi／ｋSrはＢＳＴ膜の単層膜試料を測定することによって決定できる。したがって、ＢＳＴ膜の組成比Ｃ1,Ba：Ｃ1,Sr：Ｃ1,Tiが判れば、ＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度Ｉ1,Srが決定され、最終的にＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度Ｉ2,Srを求めることができる。
【００６４】
この計算で使用するＢＳＴ膜の組成比Ｃ1,Ba：Ｃ1,Sr：Ｃ1,Tiを特定する場合、斜入射における下層のＳＲＯ膜が寄与する割合と高角度入射における上層のＢＳＴ膜が寄与する割合とを比べると、後者の方が前者より格段に大きい。したがって、ＢＳＴ膜の組成比は、信頼性の高い数値を採用するために、励起Ｘ線Ｘ１を入射角θL で照射した斜入射法による測定データを使用して算出することが好ましい。
【００６５】
こうして下層のＳＲＯ膜から発生する蛍光Ｘ線ＸSr、ＸRuの発生量が判れば、単層膜の場合と同様にＳＲＯ膜の組成を算出できる。このとき使用するｋSr／ｋRuはＳＲＯ膜の単層膜試料を測定することによって決定できる。
【００６６】
次に算出結果の回帰計算について説明する。ＢＳＴ膜の組成を算出する際に、ＳＲＯ膜の組成比として標準的な化学的組成比を使用しても大きな誤差にならないことは上述したが、誤差は少ない方が好ましい。そのため次のような手順で回帰計算を実行することによって、ＢＳＴ膜およびＳＲＯ膜の組成の測定精度を向上できる。
【００６７】
１）ＳＲＯ膜の組成Ｃ2,zとして標準的な化学的組成比を採用する。２）斜入射蛍光Ｘ線の強度測定結果とＳＲＯ膜の組成Ｃ2,zとからＢＳＴ膜の組成Ｃ1,zを算出する。３）高角度入射蛍光Ｘ線の強度測定結果とＢＳＴ膜の組成Ｃ1,zとからＳＲＯ膜の組成Ｃ2,zを新たに算出して修正する。４）修正したＳＲＯ膜の組成Ｃ2,zを用いて手順２）を行ない、新たに算出したＢＳＴ膜の組成Ｃ1,zを用いて手順３）を行ない、必要に応じて手順２）、３）を繰り返す。
【００６８】
次に実際の測定例について説明する。下記の表は、励起Ｘ線として使用するＸ線エネルギーと、ＢＳＴ膜およびＳＲＯ膜の構成元素が発生する蛍光Ｘ線のうち測定対象になる特性Ｘ線との関係を示す。
【００６９】
【表１】
グループ１はＢａのＬI 吸収端(5996eV)より大きく、ＳｒのＫ吸収端(16108eV) より小さい励起Ｘ線である。この場合、Ｂａ−Ｌ線(4465eV,4827eV,5156eV)、Ｓｒ−Ｌ線(1806eV)、Ｔｉ−Ｋ線(4508eV,4931eV) 、Ｒｕ−Ｌ線(2558eV,2683eV) という特性Ｘ線が測定対象になる。
【００７１】
グループ２はＳｒのＫ吸収端より大きく、ＲｕのＫ吸収端(22120eV) より小さい励起Ｘ線である。この場合、Ｂａ−Ｌ線、Ｓｒ−Ｋ線(14140eV,15830eV) 、Ｔｉ−Ｋ線、Ｒｕ−Ｌ線という特性Ｘ線が測定対象になる。
【００７２】
グループ３はＲｕのＫ吸収端より大きい励起Ｘ線である。この場合、Ｂａ−Ｌ線、Ｓｒ−Ｋ線、Ｔｉ−Ｋ線、Ｒｕ−Ｋ線(19233eV,21646eV) という特性Ｘ線が測定対象になる。
【００７３】
上層のＢＳＴ膜を主に測定する斜入射の場合は、Ｂａ−Ｌ線およびＴｉ−Ｋ線をなるべく精度良く測定する必要があるため、励起Ｘ線エネルギーが高いグループ２、グループ３と比べて蛍光Ｘ線の強度が大きくなるグループ１の測定系が好ましいことになる。
【００７４】
下層のＳＲＯ膜を主に測定する高角度入射の場合は、基板のＳｉ−Ｋ(1739eV)が非常に強く検出されてしまい、エネルギー分散式のＸ線検出器４を使用している場合、Ｓｒ−Ｌ線(1806eV)の検出が困難になる。その対策として、Ｓｒ−Ｌ線とは別のＳｒ−Ｋ線を測定対象としたグループ２、グループ３の測定系が好ましいことになる。
【００７５】
したがって、図１に示すような蛍光Ｘ線分析装置において、斜入射用と高角度入射用とで別々のＸ線源１を切替える構成を採用する場合、グループ１とグループ３（またはグループ２）との組合せが好ましい。一方、斜入射用と高角度入射用とで同じＸ線源１を共用する場合は、グループ２の測定系が好ましい。
【００７６】
図４は、Ｂａ蛍光Ｘ線とＴｉ蛍光Ｘ線のエネルギー分布を示すグラフである。Ｂａ−Ｌ線（4465eV,4827eV,5156eV）とＴｉ−Ｋ線（4508eV,4931eV）とは互いに接近している。そのため両者が同時に発生すると、図４の実線グラフのようにピーク位置情報が埋もれてしまう可能性がある。この場合、1)高度なグラフ解析計算を用いて測定データを２つのカーブに分離する、2)Ｂａ蛍光Ｘ線とＴｉ蛍光Ｘ線との合成量をそのまま１つのパラメータとして取扱う、などの手法によってＳｒ蛍光Ｘ線との相対比較を行なうことができる。
【００７７】
【発明の効果】
以上詳説したように本発明によれば、励起Ｘ線を入射角θL で照射したときの共通元素ＭＢおよび非共通元素ＭＡ、ＭＣの蛍光Ｘ線の各強度を検出し、予め設定された下層膜の組成比Ｋｂに基づいて、入射角θL における下層膜由来の共通元素ＭＢおよび非共通元素ＭＣの蛍光Ｘ線の強度比ＩLbを算出でき、さらに強度比ＩLbに基づいて、入射角θL における蛍光Ｘ線のうち上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出することによって、上層膜の組成比Ｋｔを算出できる。したがって、多層薄膜に共通元素が存在する場合でも、多層薄膜の組成を正確に測定できる。
【００７８】
また本発明によれば、上層のＢＳＴ膜および下層のＳＲＯ膜から成る多層薄膜が表面に形成されたシリコン基板についても、同様な手法によって、多層薄膜の組成を正確に測定できる。
【図面の簡単な説明】
【図１】本発明に係る蛍光Ｘ線分析装置を示す構成図である。
【図２】励起Ｘ線Ｘ１を低い入射角θL で入射したときの説明図である。
【図３】励起Ｘ線Ｘ１を高い入射角θH(θH＞θL) で入射したときの説明図である。
【図４】Ｂａ蛍光Ｘ線とＴｉ蛍光Ｘ線のエネルギー分布を示すグラフである。
【符号の説明】
１ Ｘ線源
２ 分光結晶
３ スリット部材
４ Ｘ線検出器
５ 試料保持機構[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multilayer thin film composition measuring method for measuring the composition of a multilayer thin film by irradiating a sample with excitation X-rays and detecting fluorescent X-rays generated from the multilayer thin film.
[0002]
[Prior art]
Recently, a technique of forming a perovskite-based metal oxide on a silicon wafer and using it as a dielectric for a capacitor of, for example, a DRAM (Dynamic Random Access Memory) has been put into practical use. Among metal oxides, BST ｛(Ba, Sr) TiO Three Since｝ has a high dielectric constant, it can be formed small and large in capacitance, and its application to gigabit-class DRAMs is being studied. As an electrode material having excellent compatibility with such a perovskite-based dielectric, SRO (SrRuO) having conductivity among the same perovskite-based metal oxides is used. Three ) Is being considered.
[0003]
When these BST and SRO are stacked as a thin film on a semiconductor wafer, a change in the element composition of each thin film greatly affects the characteristics of the integrated circuit. Further, the composition of the multi-component metal oxide is likely to change due to fluctuations in film forming conditions. Therefore, in order to stabilize product quality, it is important to accurately measure the element composition of a thin film.
[0004]
As a method for measuring the composition of a thin film, a fluorescent X-ray method capable of nondestructively inspecting is effective. The fluorescent X-ray method is a method of irradiating a sample with excitation X-rays and analyzing a spectrum of the fluorescent X-ray generated from the sample, thereby specifying an element corresponding to the characteristic X-ray.
[0005]
[Problems to be solved by the invention]
When the sample is a thin film formed on a substrate, irradiation with excitation X-rays generates characteristic X-rays specific to the constituent elements of the substrate and the thin film. For example, when a single-layer BST film is formed on a Si (silicon) substrate, Si characteristic X-rays are generated from the Si substrate, and Ba (barium) characteristic X-rays, Sr (strontium) characteristic X-rays, and Ti (Titanium) characteristic X-rays are generated. In this case, since there is no common element, separation of each characteristic X-ray becomes easy.
[0006]
However, when a multilayer thin film composed of a BST film and an SRO film is formed on a Si substrate, Si characteristic X-rays are generated from the Si substrate, and Ba characteristic X-rays, Sr characteristic X-rays, and Ti characteristic X-rays are generated from the BST film. Then, Sr characteristic X-rays and Ru (ruthenium) characteristic X-rays are generated from the SRO film. In this case, since Sr is an element common to both thin films, the composition of each thin film cannot be accurately determined unless it is possible to specify which thin film the Sr characteristic X-ray originates from.
[0007]
An object of the present invention is to provide a multilayer thin film composition measuring method capable of accurately measuring the composition of a multilayer thin film even when a common element is present in the multilayer thin film.
[0008]
[Means for Solving the Problems]
The present invention is directed to irradiating excited X-rays to a substrate on which a multilayer thin film composed of an upper layer film and a lower layer film in which a common element MB and non-common elements MA and MC are present, respectively, is formed from the multilayer thin film. A method for measuring the composition of a multilayer thin film by detecting generated fluorescent X-rays,
Specifying a composition ratio Kb of the common element MB and the non-common element MC of the lower film;
Irradiating the excitation X-rays at an incident angle θL and detecting each intensity of the fluorescent X-rays of the common element MB and the non-common elements MA and MC generated from the multilayer thin film;
Calculating an intensity ratio ILb of fluorescent X-rays of the common element MB and the non-common element MC derived from the lower layer at the incident angle θL based on the composition ratio Kb;
Calculating the intensity of the fluorescent X-rays of the common element MB derived from the upper layer film among the fluorescent X-rays at the incident angle θL based on the intensity ratio ILb;
The composition ratio Kt of the common element MB and the non-common element MA of the upper layer film is calculated based on the ratio ILt between the intensity of the fluorescent X-ray of the common element MB derived from the upper layer film and the intensity of the fluorescent X-ray of the non-common element MA. And a step of measuring the composition of the multilayer thin film.
[0009]
According to the present invention, when the excitation X-rays are irradiated on the multilayer thin film, the fluorescent X-rays from the common element MB in the upper film, the fluorescent X-rays from the non-common element MA in the upper film, and the fluorescent X-rays from the common element MB in the lower film. The fluorescent X-rays and the fluorescent X-rays from the non-common element MC of the lower film are mixed and generated. Since the spectra of the non-common elements MA and MC are different, they can be measured independently, but since the common element MB is present in both thin films, it cannot be distinguished from which thin film the fluorescent X-rays of the common element MB are derived from. .
[0010]
Further, in the case of a single film sample formed only of the upper layer film, since there is no common element, the correspondence relationship between the composition ratio of the non-common element MA and the common element MB of the upper layer film and the intensity ratio of each fluorescent X-ray. Can be determined exactly. Similarly, in the case of a single film sample formed only of the lower film, since there is no common element, the correspondence between the composition ratio of the non-common element MC and the common element MB in the lower film and the intensity ratio of each fluorescent X-ray is shown. Relationships can be determined accurately.
[0011]
When the excitation X-rays are irradiated on the multilayer thin film at a low incident angle θL, the X-ray absorption in the upper film increases, so that the intensity of the fluorescent X-rays derived from the upper film increases, and the composition information amount on the upper film decreases. More.
[0012]
Therefore, by irradiating at a low incident angle θL, detecting the intensity of the fluorescent X-ray from the non-common element MC of the lower layer film, and using the composition ratio Kb of the lower layer film specified in advance, the composition ratio and Since the relationship with the fluorescent X-ray intensity ratio is known, the fluorescent X-ray intensity derived only from the common element MB of the lower layer film can be calculated. By subtracting the calculated intensity from the intensity of the fluorescent X-ray of the common element MB derived from both films, the intensity of the fluorescent X-ray derived only from the common element MB of the upper layer film can be calculated.
[0013]
Next, using the calculated intensity of the fluorescent X-rays of the common element MB derived from the upper layer film, the composition ratio of the non-common element MA and the common element MB of the upper layer film previously specified and the intensity ratio of each fluorescent X-ray The composition ratio Kt of the common element MB and the non-common element MA in the upper layer film can be calculated by referring to the correspondence relationship between the common element MB and the non-common element MA.
[0014]
As a method for specifying the composition ratio Kb of the lower film, a) the chemical composition ratio of the compound constituting the lower film is used as it is, and b) the result of quantitative analysis of a single film sample prepared only with the lower film is used. And so on.
[0015]
When a plurality of non-common elements MA and MC and a plurality of common elements MB are present, the present invention can be applied by narrowing down to specific elements.
[0016]
Further, the present invention provides a step of irradiating the excitation X-rays at an incident angle θH (θH> θL) and detecting each intensity of the fluorescent X-rays of the common element MB and the non-common elements MA and MC generated from the multilayer thin film,
Calculating an intensity ratio IHt of the fluorescent X-rays of the common element MB and the non-common element MA derived from the upper layer film at the incident angle θH based on the composition ratio Kt;
Calculating the intensity of the fluorescent X-rays of the common element MB derived from the lower layer out of the fluorescent X-rays at the incident angle θH based on the intensity ratio IHt;
Based on the ratio IHb between the intensity of the fluorescent X-ray of the common element MB derived from the lower layer film and the intensity of the fluorescent X-ray of the non-common element MC, the composition ratio Kb of the common element MB and the non-common element MC of the lower layer film is newly set. And a calculating step.
[0017]
According to the present invention, irradiation is performed at an incident angle θH higher than the incident angle θL, and the intensities of the fluorescent X-rays of the common element MB and the non-common elements MA and MC generated from the multilayer thin film are detected. Since the relationship between the composition ratio and the fluorescent X-ray intensity ratio is known by using the composition ratio Kt calculated by the irradiation of, the intensity ratio of the fluorescent X-rays of the common element MB and the non-common element MA derived from the upper layer film IHt can be calculated. From the intensity ratio IHt, the intensity of fluorescent X-rays derived only from the common element MB of the lower layer film can be calculated.
[0018]
Next, the relationship between the composition ratio and the fluorescent X-ray intensity ratio is known using the calculated ratio IHb of the intensity of the fluorescent X-ray of the common element MB derived from the lower layer film and the intensity of the fluorescent X-ray of the non-common element MC. Therefore, the composition ratio Kb of the common element MB and the non-common element MC of the lower film can be newly calculated.
[0019]
When the excitation X-rays are irradiated to the multilayer thin film at a high incident angle θH (θH> θL), the X-ray absorption in the upper film is reduced, so that the intensity of the fluorescent X-rays derived from the lower film is increased and the lower film is The amount of composition information about Therefore, the accuracy of measuring the composition ratio Kb of the lower layer film is further improved.
[0020]
The composition ratio Kb thus calculated is adopted as a new default value, and the above-described calculation steps, that is, the step of calculating the intensity ratio ILb of the fluorescent X-rays derived from the lower film at the incident angle θL, the common element MB derived from the upper film By repeating the step of calculating the intensity of the fluorescent X-ray and the step of calculating the composition ratio Kt of the upper layer film, the measurement accuracy of the composition ratio Kt can be further improved. The obtained composition ratio Kt is adopted as a new default value, and the above-described calculation steps, that is, a step of calculating the intensity ratio IHt of the fluorescent X-ray derived from the upper layer film at the incident angle θH, and the step of calculating the lower layer film at the incident angle θH By repeating the step of calculating the intensity of the fluorescent X-ray of the common element MB and the step of calculating the composition ratio Kb of the lower layer film, the measurement accuracy of the composition ratio Kb can be further improved. Further, since the accuracy can be improved by such regression calculation, the accuracy of the composition ratio Kb as an initial value can be relaxed.
[0021]
The present invention also provides a method of irradiating excitation X-rays to a silicon substrate having a multilayer thin film composed of an upper BST film and a lower SRO film formed on a surface thereof, and detecting fluorescent X-rays generated from the multilayer thin film. A method for measuring the composition of a multilayer thin film,
A step of specifying the composition ratio KSR of Sr and Ru of the SRO film;
Irradiating the excitation X-ray at a low incident angle θL, and detecting each intensity of fluorescent X-rays XBa, XSr, XTi, XRu of Ba, Sr, Ti, and Ru generated from the multilayer thin film;
Calculating an intensity ratio ILSR of the fluorescent X-rays XSr and XRu derived from the SRO film at an incident angle θL based on the composition ratio KSR;
Calculating the intensity of the fluorescent X-ray XSr derived from the BST film among the fluorescent X-rays XSr at the incident angle θL based on the intensity ratio ILSR;
Calculating a composition ratio KBST of Ba, Sr, and Ti of the BST film based on the intensity of the fluorescent X-rays XSr derived from the BST film and the ratio ILSBT of the fluorescent X-rays XBa and XTi. This is a thin film composition measuring method.
[0022]
According to the present invention, when the excitation X-ray is irradiated on the multilayer thin film, the fluorescent X-ray XSr from Sr, which is a common element of the upper BST film, and the fluorescent X-ray from Ba and Ti, which are non-common elements of the BST film. XBa, XTi, X-ray fluorescence XSr from Sr which is a common element of the underlying SRO film, and X-ray fluorescence XRu from Ru which is a non-common element of the SRO film are mixed and generated. Since the non-common elements Ba, Ti, and Ru have different spectra, they can be measured independently. However, since the common element Sr is present in both thin films, it cannot be distinguished from which thin film the fluorescent X-ray XSr originates.
[0023]
In the case of a single film sample formed only of the BST film, since there is no common element, the composition ratio of Ba, Sr, and Ti in the BST film and the intensity ratio of each of the fluorescent X-rays XBa, XSr, and XTi are determined. The correspondence can be determined accurately. Similarly, in the case of a single film sample formed only of the SRO film, since there is no common element, the correspondence between the composition ratio of Sr and Ru of the SRO film and the intensity ratio of each of the fluorescent X-rays XSr and XRu is Can be determined accurately.
[0024]
When the excitation X-rays are irradiated to the multilayer thin film at a low incident angle θL, the X-ray absorption in the upper BST film increases, so that the intensity of the fluorescent X-rays derived from the BST film increases, and the composition information on the BST film The amount increases.
[0025]
Therefore, by irradiating at a low incident angle θL, detecting the intensity of the fluorescent X-ray XRu from Ru of the SRO film, and using the composition ratio KSR of the SRO film specified in advance, the composition ratio and the fluorescent X Since the relationship with the line intensity ratio is known, the intensity of the fluorescent X-ray XSr derived only from Sr of the SRO film can be calculated. By subtracting the calculated intensity from the intensity of the fluorescent X-rays XSr derived from both films, the intensity of the fluorescent X-rays XSr derived only from the Sr of the BST film can be calculated.
[0026]
Next, using the calculated intensity of the fluorescent X-ray XSr derived from the BST film, the composition ratio of Ba, Sr, and Ti of the BST film specified in advance and the intensity ratio of each fluorescent X-ray XBa, XSr, and XTi were determined. By referring to the correspondence, the composition ratio KBST of the BST film can be calculated.
[0027]
In addition, as a method of specifying the composition ratio KSR of the SRO film, a) a chemical composition ratio of Sr and Ru of the SRO compound of 1: 1 was used as it is, and b) a single film sample prepared only with the SRO film was quantitatively analyzed. It is possible to use the result.
[0028]
Further, the present invention irradiates the excitation X-ray at an incident angle θH (θH> θL) and detects each intensity of fluorescent X-rays XBa, XSr, XTi and XRu of Ba, Sr, Ti and Ru generated from the multilayer thin film. Process and
Calculating the intensity ratio IHBST of the fluorescent X-rays XBa, XSr, and XTi derived from the BST film at the incident angle θH based on the composition ratio KBST;
Calculating the intensity of the fluorescent X-ray XSr derived from the SRO film among the fluorescent X-rays at the incident angle θH based on the intensity ratio IHBST;
A step of newly calculating the composition ratio KSR of Sr and Ru of the SRO film based on the ratio IHSR of the intensity of the fluorescent X-ray XSr and the intensity of the fluorescent X-ray XRu derived from the SRO film.
[0029]
According to the present invention, by irradiating at an incident angle θH higher than the incident angle θL, each intensity of the fluorescent X-rays XBa, XSr, XTi and XRu of Ba, Sr, Ti and Ru generated from the multilayer thin film is detected, Since the relationship between the composition ratio and the fluorescent X-ray intensity ratio is known by using the composition ratio KBST calculated by irradiation at the incident angle θL, the intensity ratio of the fluorescent X-rays XBa, XSr, and XTi derived from the BST film is known. IHBST can be calculated. From the intensity ratio IHBST, the intensity of the fluorescent X-ray XSr derived from the SRO film can be calculated.
[0030]
Next, since the relationship between the composition ratio and the fluorescent X-ray intensity ratio is known using the calculated ratio IHSR between the intensity of the fluorescent X-ray XSr derived from the SRO film and the intensity of the fluorescent X-ray XRu, the SRO film Can be newly calculated.
[0031]
When the excitation X-rays are irradiated on the multilayer thin film at a high incident angle θH (θH> θL), the X-ray absorption in the upper BST film is reduced, and the intensity of the fluorescent X-rays derived from the lower SRO film is increased. Thus, the amount of composition information on the SRO film increases. Therefore, the accuracy of measuring the composition ratio KSR of the SRO film is further improved.
[0032]
The composition ratio KSR calculated in this manner is adopted as a new default value, and the above-described calculation steps, that is, the step of calculating the intensity ratio ILSR of the fluorescent X-rays derived from the SRO film at the incident angle θL, the fluorescent X-rays derived from the BST film By repeating the step of calculating the intensity of XSr and the step of calculating the composition ratio KBST of the BST film, the measurement accuracy of the composition ratio KBST can be further improved. The obtained composition ratio KBST is adopted as a new predetermined value, and the above-mentioned calculation steps, that is, the step of calculating the intensity ratio IHBST of the fluorescent X-rays derived from the BST film at the incident angle θH, the step of calculating the intensity ratio of the SRO film at the incident angle θH By repeating the step of calculating the intensity of the fluorescent X-ray XSr and the step of calculating the composition ratio KSR of the SRO film, the measurement accuracy of the composition ratio KSR can be further improved. In addition, since the accuracy can be improved by such regression calculation, the accuracy of the composition ratio KSR as an initial value can be relaxed.
[0033]
Further, the present invention is characterized in that monochromatic X-rays are used as the excitation X-rays.
[0034]
According to the present invention, the lower the incident angle of the excitation X-ray, the longer the X-ray passage distance in the upper layer film. The effective extinction length, which defines the distance until the original intensity attenuates to a certain value after the excitation X-rays pass, varies depending on the X-ray energy (wavelength) and the elements constituting the medium. Therefore, as the X-ray passing distance in the upper film becomes longer, the influence of the energy distribution of the excited X-rays appears as a measurement error. Therefore, it is preferable to make the excited X-rays monochromatic as a countermeasure.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a configuration diagram showing an X-ray fluorescence analyzer according to the present invention. An X-ray fluorescence analyzer includes an
[0036]
The sample SP to which the present invention is applied is a sample in which a multilayer thin film including an upper film containing the non-common element MA and the common element MB and a lower film containing the common element MB and the non-common element MC is formed on a substrate. Here, a silicon wafer on which a multilayer thin film including an upper BST film and a lower SRO film is formed is exemplified.
[0037]
Next, the principle of the present invention will be described. First, a method for measuring the composition of the single-layer film will be described. When the excitation X-ray is irradiated at a high incident angle θ, the fluorescent X-ray intensity of each element of the single-layer film is represented by the following equation (1). Here, Iz is the fluorescent X-ray intensity of the element Z, kz is the device sensitivity coefficient of the element Z, Cz is the content (mass ratio) of the element Z, ρ is the density of the film, and t is the thickness of the film.
Iz = kz · Cz · ρ · t (1)
[0038]
At this time, if the single-layer film is sufficiently thin, the absorption of the excitation X-rays and the absorption of the fluorescent X-rays by the film can be ignored. When only the composition analysis is intended, the parameters can be reduced as in the following equation (2) by relative comparison with any other element ZO.
Iz / Izo = (kz · Cz) / (kzo · Czo) (2)
[0039]
Here, if a reference sample whose composition Cz is known for all elements is prepared and the fluorescent X-ray intensities Iz of all elements are measured, the relative apparatus sensitivity coefficient can be obtained as in the following equation (3). . Here, Iz, R is the fluorescent X-ray intensity of element Z in the reference sample, and Cz, R is the content (mass ratio) of element Z in the reference sample.
kz / kzo = (Iz, R · Cz, R) / (Izo, R · Cz, R) (3)
[0040]
If the apparatus sensitivity coefficient is determined in this way, the composition Cz can be determined by solving the following simultaneous equations (4) and (5) by measuring the fluorescent X-ray intensity also for the unknown sample.
Czo / Cz = (kz · Izo) / (kzo · Iz) (4)
ΣCz = 1 (total for element Z = 1) (5)
[0041]
Next, when the oblique incidence method is used, the following equations (6) and (7) generally hold. Here, dz and dzo are the effective extinction lengths of the excited X-rays corresponding to the elements Z and ZO.
Iz = kz · Cz · ρ · dz (6)
Izo = kzo ・ Czo ・ ρ ・ dzo ... (7)
[0042]
dz and dzo are determined by the absorption of excited X-rays by the film. Note that the absorption of fluorescent X-rays by the film is ignored. Similarly to the above-mentioned formula (2) of the high angle incidence method, the fluorescent X-ray intensity ratio of the elements Z and ZO can be obtained as in the following formula (8).
Iz / Izo = (kz.Cz.dz) / (kzo.Czo.dzo) (8)
[0043]
Therefore, only the element of dz / dzo differs from the high-angle incidence method, but by making the excitation X-ray monochromatic, dz / dzo = 1, which agrees with the equation (2). Therefore, if monochromatic excitation X-rays are used, the same calculation formula as in the high-angle incidence method can be used in the oblique incidence method, and the calculation process can be simplified.
[0044]
Next, a method for measuring the composition of the multilayer film will be described.
FIG. 2 is an explanatory diagram when the excitation X-ray X1 is incident at a low incident angle θL, and FIG. 3 is an explanatory diagram when the excitation X-ray X1 is incident at a high incident angle θH (θH> θL). The measurement sample is a silicon wafer on which a multilayer thin film including an upper BST film and a lower SRO film is formed.
[0045]
First, as shown in FIG. 2, when the incident angle .theta.L of the excitation X-ray X1 is set to a sufficiently low angle, for example, 0.1 degree, the X-rays XBa, XSr of Ba, Sr, and Ti are emitted from the upper BST film. , XTi are generated relatively strongly, and fluorescent S-rays XSr and XRu of Sr and Ru are generated weakly from the lower SRO film. At this time, since Sr exists in both the BST film and the SRO film, it cannot be distinguished from which film the detected fluorescent X-ray XSr is derived.
[0046]
Generally, when X-rays are obliquely incident on a two-layered thin film, the intensity of the detected fluorescent X-rays can be described as in the following equations (9) to (11). Here, I1, z, I2, z are the fluorescent X-ray intensities of the element Z from the first layer and the second layer, and C1, z, C2, z are the contents of the element Z in the first and second layers ( Mass ratio), ρ1 and ρ2 are the densities of the first and second layers, d1 and d2 are the effective extinction lengths of the excited X-rays in the first and second layers, and T1 is the excitation of the first layer. X-ray transmittance.
Iz = I1, z + I2, z (9)
I1, z = kz · C1, z · ρ1 · d1 (10)
I2, z = T1 ・ zzC2, z ・ ρ22d2 (11)
[0047]
As in the case of the single layer film, the expressions (10) and (11) can be simplified as the following expressions (12) and (13) by the relative comparison of the fluorescent X-ray dose with the fluorescent X-ray dose of a certain element.
I1, z / I1, z1 = (kz.C1, z) / (kzo.C1, zo) (12)
I2, z / I2, z2 = (kz.C2, z) / (kzo.C2, zo) (13)
[0048]
Next, the above equation is applied to a multilayer thin film including a BST film and an SRO film.
IBa = I1, Ba ... (14)
ISr = I1, Sr + I2, Sr (15)
Iti = I1, Ti ... (16)
IRu = I2, Ru (17)
I1, Ba / I1, Sr = (kBa.C1, Ba) / (kSr.C1, Sr) (18)
I1, Ti / I1, Sr = (kTi.C1, Ti) / (kSr.C1, Sr) (19)
I2, Sr / I2, Ru = (kSr.C2, Sr) / (kRu.C2, Ru) (20)
[0049]
From the equations (15), (17) and (20), the intensity I1, Sr of the fluorescent X-ray XSr derived from the BST film is obtained.
Here, ISr and IRu are observation quantities, and kSr / kRu can be determined by measuring a single-layer SRO film sample. Therefore, if the composition ratio C2, Sr / C2, Ru of the SRO film is known, the intensity I2, Sr of the fluorescent X-ray XSr derived from the SRO film is determined, and finally the intensity I1, S1 of the fluorescent X-ray XSr derived from the BST film. Sr can be obtained.
[0051]
As the composition ratio C2, Sr / C2, Ru of the SRO film used in this calculation, a standard chemical composition ratio of 1: 1 can be adopted. The reason is that, when the excited X-ray is incident at a low angle, the excited X-ray is almost absorbed by the upper BST film, the transmittance X1 of the excited X-ray of the BST film becomes extremely small, and the fluorescent X Compared to the line intensity I1, Sr, the fluorescent X-ray intensity I2, Sr derived from the SRO film is only about 1/100. Therefore, even if the set value of the composition ratio C2, Sr / C2, Ru contains, for example, an error of one tenth, the calculation result of the intensity I1, Sr only gives an error of about one thousandth. . Further, as will be described later, it is also possible to sequentially refine using the measurement results of the SRO film.
[0052]
If the amount of generated fluorescent X-rays XBa, XSr, and XTi generated from the upper BST film is known, the composition of the BST film can be calculated in the same manner as in the case of the single-layer film. The kBa / kSr and kTi / kSr used at this time can be determined by measuring a single-layer film sample of the BST film.
[0053]
Next, measurement of the composition of the lower SRO film will be described. As shown in FIG. 3, when the incident angle θH of the excitation X-ray X1 is set at a sufficiently high angle, for example, 2 degrees, the fluorescent X-rays XBa, XSr, and XTi of Ba, Sr, and Ti are emitted from the upper BST film. Then, fluorescent X-rays XSr and XRu of Sr and Ru are generated from the lower SRO film more strongly than the incident angle θL. At this time, since Sr exists in both the BST film and the SRO film, it cannot be distinguished from which film the detected fluorescent X-ray XSr is derived.
[0054]
In general, when X-rays are incident on a thin film having a two-layer structure at a high angle, the intensity of the detected fluorescent X-rays is expressed by the following equations (22) to (24) in the same manner as the equations (9) to (11). Can be described. Here, t1 and t2 are the thicknesses of the first layer and the second layer. Further, the absorption of the excited X-rays and the fluorescent X-rays in the first layer and the second layer can be neglected because the passing distance is short.
Iz = I1, z + I2, z (22)
I1, z = kz · C1, z · ρ1 · t1 (23)
I2, z = kz · C2, z · ρ2 · t2 (24)
[0055]
As in the case of the single-layer film, the expressions (23) and (24) can be simplified to the following expressions (25) and (26) by relative comparison of the fluorescent X-ray dose with the fluorescent X-ray dose of a certain element.
I1, z / I1, z1 = (kz.C1, z) / (kzo.C1, zo) (25)
I2, z / I2, z2 = (kz.C2, z) / (kzo.C2, zo) (26)
[0056]
Next, the above equation is applied to a multilayer thin film including a BST film and an SRO film.
IBa = I1, Ba ... (27) ISr = I1, Sr + I2, Sr ... (28)
Iti = I1, Ti ... (29)
IRu = I2, Ru (30)
I1, Ba / I1, Sr = (kBa.C1, Ba) / (kSr.C1, Sr) (31)
I1, Ti / I1, Sr = (kTi · C1, Ti) / (kSr · C1, Sr) (32)
I2, Sr / I2, Ru = (kSr · C2, Sr) / (kRu · C2, Ru) (33)
[0057]
By transforming the equations (31) and (32), the intensity I1, Sr of the fluorescent X-ray XSr derived from the BST film is obtained.
[0058]
(Equation 1)
In addition to such a calculation method, it is also possible to obtain the intensities I1, Sr as in the following equations (36) and (37) using, for example, equation (31).
I1, Ba / I1, Sr = (kBa.C1, Ba) / (kSr.C1, Sr) (36)
I1, Sr = (I1, Ba.kSr.C1, Sr) / (kBa.C1, Ba) (37)
[0060]
Regarding the measurement accuracy, the higher the intensity of the fluorescent X-ray to be measured, the higher the S / N ratio. When measuring the intensity of fluorescent X-rays XBa and XTi, for example, when Ba-L characteristic X-rays and Ti-K characteristic X-rays are used, there is a situation that both peaks are close to each other. When the sum of these fluorescent X-ray intensities is obtained without separating the peaks, much more stable measurement can be performed than when either one is obtained by separating the peaks. In such a situation, the method using equation (35) is preferable.
[0061]
Therefore, the intensities I2, Sr of the fluorescent X-ray XSr derived from the SRO film are obtained by using the equations (28) and (35).
[0062]
(Equation 2)
Here, ISr, IBa, and ITi are observation quantities, and kBa / kSr and kTi / kSr can be determined by measuring a single-layer film sample of the BST film. Therefore, if the composition ratio C1, Ba: C1, Sr: C1, Ti of the BST film is known, the intensity I1, Sr of the fluorescent X-ray XSr derived from the BST film is determined, and finally the fluorescent X-ray XSr derived from the SRO film. Can be obtained.
[0064]
When the composition ratio C1, Ba: C1, Sr: C1, Ti of the BST film used in this calculation is specified, the ratio of the lower SRO film at oblique incidence and the ratio of the upper BST film at high angle incidence. When compared with the latter, the latter is much larger than the former. Therefore, the composition ratio of the BST film is preferably calculated using oblique incidence data obtained by irradiating the excitation X-ray X1 at the incident angle θL in order to adopt a highly reliable numerical value.
[0065]
If the amount of the fluorescent X-rays XSr and XRu generated from the lower SRO film is known, the composition of the SRO film can be calculated in the same manner as in the case of the single-layer film. The kSr / kRu used at this time can be determined by measuring a single-layer film sample of the SRO film.
[0066]
Next, the regression calculation of the calculation result will be described. As described above, when calculating the composition of the BST film, a large error is not caused even if a standard chemical composition ratio is used as the composition ratio of the SRO film. However, it is preferable that the error be small. Therefore, by executing the regression calculation in the following procedure, the measurement accuracy of the composition of the BST film and the SRO film can be improved.
[0067]
1) A standard chemical composition ratio is adopted as the composition C2, z of the SRO film. 2) The composition C1, z of the BST film is calculated from the intensity measurement result of the obliquely incident X-ray fluorescence and the composition C2, z of the SRO film. 3) The composition C2, z of the SRO film is newly calculated and corrected from the intensity measurement result of the high-angle incident X-ray fluorescence and the composition C1, z of the BST film. 4) Perform procedure 2) using the modified composition C2, z of the SRO film, perform procedure 3) using the newly calculated composition C1, z of the BST film, and perform procedures 2) and 3) as necessary. repeat.
[0068]
Next, an actual measurement example will be described. The following table shows the relationship between the X-ray energy used as the excitation X-ray and the characteristic X-ray to be measured among the fluorescent X-rays generated by the constituent elements of the BST film and the SRO film.
[0069]
[Table 1]
[0071]
[0072]
Group 3 is excited X-rays larger than the Ru K-absorption edge. In this case, characteristic X-rays such as Ba-L line, Sr-K line, Ti-K line, and Ru-K line (19233 eV, 21646 eV) are measured.
[0073]
In the case of oblique incidence where the upper BST film is mainly measured, it is necessary to measure the Ba-L line and the Ti-K line as accurately as possible. The measurement system of
[0074]
In the case of high-angle incidence mainly measuring the lower SRO film, Si-K (1739 eV) of the substrate is detected very strongly, and when the energy dispersive X-ray detector 4 is used, Sr -It becomes difficult to detect the L line (1806 eV). As a countermeasure, it is preferable to use the measurement systems of
[0075]
Therefore, in the X-ray fluorescence analyzer as shown in FIG. 1, when adopting a configuration in which
[0076]
FIG. 4 is a graph showing the energy distribution of Ba fluorescent X-rays and Ti fluorescent X-rays. The Ba-L line (4465 eV, 4827 eV, 5156 eV) and the Ti-K line (4508 eV, 4931 eV) are close to each other. Therefore, if both occur at the same time, the peak position information may be buried as shown by the solid line graph in FIG. In this case, 1) the measurement data is separated into two curves by using advanced graph analysis calculation, 2) the combined amount of Ba fluorescent X-ray and Ti fluorescent X-ray is treated as one parameter as it is, and the like. Relative comparison with Sr fluorescent X-rays can be performed.
[0077]
【The invention's effect】
As described in detail above, according to the present invention, the intensity of the fluorescent X-rays of the common element MB and the non-common elements MA and MC when the excitation X-ray is irradiated at the incident angle θL is detected, and the predetermined lower layer film is detected. Based on the composition ratio Kb, the intensity ratio ILb of the fluorescent X-rays of the common element MB and the non-common element MC derived from the lower film at the incident angle θL can be calculated. Further, based on the intensity ratio ILb, the fluorescent X-ray at the incident angle θL can be calculated. By calculating the intensity of the fluorescent X-ray of the common element MB derived from the upper layer film among the lines, the composition ratio Kt of the upper layer film can be calculated. Therefore, even when a common element exists in the multilayer thin film, the composition of the multilayer thin film can be accurately measured.
[0078]
Further, according to the present invention, the composition of a multilayer thin film can be accurately measured by a similar method for a silicon substrate having a multilayer thin film composed of an upper BST film and a lower SRO film formed on the surface.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an X-ray fluorescence analyzer according to the present invention.
FIG. 2 is an explanatory diagram when an excitation X-ray X1 is incident at a low incident angle θL.
FIG. 3 is an explanatory diagram when an excitation X-ray X1 is incident at a high incident angle θH (θH> θL).
FIG. 4 is a graph showing energy distributions of Ba fluorescent X-rays and Ti fluorescent X-rays.
[Explanation of symbols]
1 X-ray source
2 Spectral crystal
3 Slit member
4 X-ray detector
5 Sample holding mechanism
Claims (5)
下層膜の共通元素ＭＢおよび非共通元素ＭＣの組成比Ｋｂを特定する工程と、
励起Ｘ線を入射角θL で照射し、多層薄膜から発生する共通元素ＭＢおよび非共通元素ＭＡ、ＭＣの蛍光Ｘ線の各強度を検出する工程と、
前記組成比Ｋｂに基づいて、入射角θL における下層膜由来の共通元素ＭＢおよび非共通元素ＭＣの蛍光Ｘ線の強度比ＩLbを算出する工程と、
前記強度比ＩLbに基づいて、入射角θL における蛍光Ｘ線のうち上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出する工程と、
上層膜由来の共通元素ＭＢの蛍光Ｘ線の強度と非共通元素ＭＡの蛍光Ｘ線の強度との比ＩLtに基づいて、上層膜の共通元素ＭＢおよび非共通元素ＭＡの組成比Ｋｔを算出する工程とを含むことを特徴とする多層薄膜組成測定方法。Excited X-rays are directed to a substrate on which a multilayer thin film composed of an upper layer film and a lower layer film, in which an element MB common to each other and elements MA and MC not present are present, is formed. A method for measuring the composition of a multilayer thin film by detecting a line,
Specifying a composition ratio Kb of the common element MB and the non-common element MC of the lower film;
Irradiating the excitation X-rays at an incident angle θL and detecting each intensity of the fluorescent X-rays of the common element MB and the non-common elements MA and MC generated from the multilayer thin film;
Calculating an intensity ratio ILb of fluorescent X-rays of the common element MB and the non-common element MC derived from the lower layer at the incident angle θL based on the composition ratio Kb;
Calculating the intensity of the fluorescent X-rays of the common element MB derived from the upper layer film among the fluorescent X-rays at the incident angle θL based on the intensity ratio ILb;
The composition ratio Kt of the common element MB and the non-common element MA of the upper layer film is calculated based on the ratio ILt between the intensity of the fluorescent X-ray of the common element MB derived from the upper layer film and the intensity of the fluorescent X-ray of the non-common element MA. And measuring the composition of the multilayer thin film.
前記組成比Ｋｔに基づいて、入射角θH における上層膜由来の共通元素ＭＢおよび非共通元素ＭＡの蛍光Ｘ線の強度比ＩHtを算出する工程と、
前記強度比ＩHtに基づいて、入射角θH における蛍光Ｘ線のうち下層膜由来の共通元素ＭＢの蛍光Ｘ線の強度を算出する工程と、
下層膜由来の共通元素ＭＢの蛍光Ｘ線の強度と非共通元素ＭＣの蛍光Ｘ線の強度との比ＩHbに基づいて、下層膜の共通元素ＭＢおよび非共通元素ＭＣの組成比Ｋｂを新たに算出する工程とを含むことを特徴とする請求項１記載の多層薄膜組成測定方法。Irradiating excitation X-rays at an incident angle θH (θH> θL), and detecting each intensity of fluorescent X-rays of the common element MB and the non-common elements MA and MC generated from the multilayer thin film;
Calculating an intensity ratio IHt of the fluorescent X-rays of the common element MB and the non-common element MA derived from the upper layer film at the incident angle θH based on the composition ratio Kt;
Calculating the intensity of the fluorescent X-rays of the common element MB derived from the lower layer out of the fluorescent X-rays at the incident angle θH based on the intensity ratio IHt;
Based on the ratio IHb between the intensity of the fluorescent X-rays of the common element MB derived from the lower film and the intensity of the fluorescent X-rays of the non-common element MC, the composition ratio Kb of the common element MB and the non-common element MC of the lower film is newly set. 2. The method for measuring the composition of a multilayer thin film according to claim 1, comprising a step of calculating.
ＳＲＯ膜のＳｒ、Ｒｕの組成比ＫSRを特定する工程と、
励起Ｘ線を低い入射角θL で照射し、多層薄膜から発生するＢａ、Ｓｒ、Ｔｉ、Ｒｕの蛍光Ｘ線ＸBa、ＸSr、ＸTi、ＸRuの各強度を検出する工程と、
前記組成比ＫSRに基づいて、入射角θL におけるＳＲＯ膜由来の蛍光Ｘ線ＸSr、ＸRuの強度比ＩLSR を算出する工程と、
前記強度比ＩLSRに基づいて、入射角θL における蛍光Ｘ線ＸSrのうちＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度を算出する工程と、
ＢＳＴ膜由来の蛍光Ｘ線ＸSrの強度と蛍光Ｘ線ＸBa、ＸTiとの比ＩLSBTに基づいて、ＢＳＴ膜のＢａ、Ｓｒ、Ｔｉの組成比ＫBST を算出する工程とを含むことを特徴とする多層薄膜組成測定方法。The composition of the multilayer thin film is determined by irradiating excitation X-rays to a silicon substrate on which a multilayer thin film composed of an upper BST film and a lower SRO film is formed, and detecting fluorescent X-rays generated from the multilayer thin film. A method of measuring,
A step of specifying the composition ratio KSR of Sr and Ru of the SRO film;
Irradiating the excitation X-ray at a low incident angle θL, and detecting each intensity of fluorescent X-rays XBa, XSr, XTi, XRu of Ba, Sr, Ti, and Ru generated from the multilayer thin film;
Calculating an intensity ratio ILSR of the fluorescent X-rays XSr and XRu derived from the SRO film at an incident angle θL based on the composition ratio KSR;
Calculating the intensity of the fluorescent X-ray XSr derived from the BST film among the fluorescent X-rays XSr at the incident angle θL based on the intensity ratio ILSR;
Calculating a composition ratio KBST of Ba, Sr and Ti of the BST film based on the ratio of the intensity of the fluorescent X-rays XSr derived from the BST film and the ratio of the fluorescent X-rays XBa and XTi to the ILSBT. Thin film composition measurement method.
前記組成比ＫBST に基づいて、入射角θH におけるＢＳＴ膜由来の蛍光Ｘ線ＸBa、ＸSr、ＸTiの強度比ＩHBSTを算出する工程と、
前記強度比ＩHBSTに基づいて、入射角θH における蛍光Ｘ線のうちＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度を算出する工程と、
ＳＲＯ膜由来の蛍光Ｘ線ＸSrの強度と蛍光Ｘ線ＸRuの強度との比ＩHSR に基づいて、ＳＲＯ膜のＳｒ、Ｒｕの組成比ＫSRを新たに算出する工程とを含むことを特徴とする請求項３記載の多層薄膜組成測定方法。Irradiating the excitation X-rays at an incident angle θH (θH> θL), and detecting the respective intensities of the fluorescent X-rays XBa, XSr, XTi, XRu of Ba, Sr, Ti, and Ru generated from the multilayer thin film;
Calculating the intensity ratio IHBST of the fluorescent X-rays XBa, XSr, and XTi derived from the BST film at the incident angle θH based on the composition ratio KBST;
Calculating the intensity of the fluorescent X-ray XSr derived from the SRO film among the fluorescent X-rays at the incident angle θH based on the intensity ratio IHBST;
A step of newly calculating a composition ratio KSR of Sr and Ru of the SRO film based on a ratio IHSR between the intensity of the fluorescent X-ray XSr and the intensity of the fluorescent X-ray XRu derived from the SRO film. Item 4. The method for measuring the composition of a multilayer thin film according to Item 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13446699A JP3545966B2 (en) | 1999-05-14 | 1999-05-14 | Multilayer thin film composition measurement method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13446699A JP3545966B2 (en) | 1999-05-14 | 1999-05-14 | Multilayer thin film composition measurement method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000321223A JP2000321223A (en) | 2000-11-24 |
| JP3545966B2 true JP3545966B2 (en) | 2004-07-21 |
Family
ID=15128991
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13446699A Expired - Fee Related JP3545966B2 (en) | 1999-05-14 | 1999-05-14 | Multilayer thin film composition measurement method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3545966B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4734224B2 (en) * | 2006-12-18 | 2011-07-27 | 本田技研工業株式会社 | Buffer layer thickness measurement method |
| WO2012008513A1 (en) * | 2010-07-15 | 2012-01-19 | 株式会社堀場製作所 | Fluorescent x-ray detection method and fluorescent x-ray detection device |
| JP6605345B2 (en) * | 2016-02-01 | 2019-11-13 | スタンレー電気株式会社 | Method for calculating the ratio of elements constituting the laminate |
-
1999
- 1999-05-14 JP JP13446699A patent/JP3545966B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000321223A (en) | 2000-11-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10030971B2 (en) | Measurement system and method for measuring in thin films | |
| KR20160111483A (en) | Methods and systems for measuring periodic structures using multi-angle x-ray reflectance scatterometry (xrs) | |
| EP3134712B1 (en) | Silicon germanium thickness and composition determination using combined xps and xrf technologies | |
| WO2001023873A1 (en) | X-ray microanalyzer for thin films | |
| Diebold et al. | Characterization and production metrology of thin transistor gate oxide films | |
| US11029148B2 (en) | Feed-forward of multi-layer and multi-process information using XPS and XRF technologies | |
| JP3908472B2 (en) | Film thickness measuring method and level difference measuring method | |
| JP2005062188A (en) | Thickness measuring apparatus and thickness measuring method | |
| EP3845893B1 (en) | System and method applicable for measuring thickness of ultrathin film on substrate | |
| McBriarty et al. | Crystal phase distribution and ferroelectricity in ultrathin HfO2–ZrO2 bilayers | |
| TW202314237A (en) | System and method using x-rays for depth-resolving metrology and analysis | |
| JP3545966B2 (en) | Multilayer thin film composition measurement method | |
| WO2012153462A1 (en) | Method for determining film thickness of soi layer of soi wafer | |
| TWI329736B (en) | X-ray scattering with a polychromatic source | |
| US20060280285A1 (en) | Fluorescent X-ray spectroscopic apparatus | |
| Banyay et al. | Cross characterization of ultrathin interlayers in HfO2 high-k stacks by angle resolved x-ray photoelectron spectroscopy, medium energy ion scattering, and grazing incidence extreme ultraviolet reflectometry | |
| US11852467B2 (en) | Method and system for monitoring deposition process | |
| Franquet et al. | Thickness and composition measurements of nanoelectronics multilayer thin films by energy dispersive spectroscopy (EDS) | |
| Leng et al. | Combined beam profile reflectometry, beam profile ellipsometry and ultraviolet-visible spectrophotometry for the characterization of ultrathin oxide-nitride-oxide films on silicon | |
| JPH06222019A (en) | Nondestructive quantitative analysis of multilayer thin film | |
| JP2004093436A (en) | Analysis method for thin-film multi-layer structure by using spectral ellipsometer | |
| JPH05209847A (en) | Fluorescent x-ray spectroscopy method and apparatus | |
| JPH1140635A (en) | Method for evaluating layer thickness of semiconductor multilayered film | |
| JP3950074B2 (en) | Thickness measuring method and thickness measuring apparatus | |
| JP2000077494A (en) | Manufacture of semiconductor integrated circuit device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20040316 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20040409 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| S303 | Written request for registration of pledge or change of pledge |
Free format text: JAPANESE INTERMEDIATE CODE: R316303 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080416 Year of fee payment: 4 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313111 |
|
| S803 | Written request for registration of cancellation of provisional registration |
Free format text: JAPANESE INTERMEDIATE CODE: R316803 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080416 Year of fee payment: 4 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080416 Year of fee payment: 4 |
|
| R360 | Written notification for declining of transfer of rights |
Free format text: JAPANESE INTERMEDIATE CODE: R360 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080416 Year of fee payment: 4 |
|
| R360 | Written notification for declining of transfer of rights |
Free format text: JAPANESE INTERMEDIATE CODE: R360 |
|
| R371 | Transfer withdrawn |
Free format text: JAPANESE INTERMEDIATE CODE: R371 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090416 Year of fee payment: 5 |
|
| S803 | Written request for registration of cancellation of provisional registration |
Free format text: JAPANESE INTERMEDIATE CODE: R316803 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090416 Year of fee payment: 5 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090416 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100416 Year of fee payment: 6 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313113 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100416 Year of fee payment: 6 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110416 Year of fee payment: 7 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110416 Year of fee payment: 7 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120416 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130416 Year of fee payment: 9 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130416 Year of fee payment: 9 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140416 Year of fee payment: 10 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| LAPS | Cancellation because of no payment of annual fees |