JP3817094B2 - Thin film thickness measuring device - Google Patents

Description

【００１４】
光が薄膜中を透過する時の位相のずれδは、薄膜の膜厚ｄと光の波長λとに依存するので、式（１）から波長λと薄膜の透過率Ｔとの関係を求めることができる。したがって、薄膜の膜厚ｄと薄膜の屈折率ｎ′とを変化させて、式（１）から求められる波長−光強度の理論関係曲線を、波長−光強度の測定関係曲線に最も近づけ、そのときの薄膜の膜厚ｄと薄膜の屈折率ｎ′とを測定値とする。
【００１５】
【発明が解決しようとする課題】
図１８に示すエリプソメータを用いた膜厚測定装置においては、基板１０３と偏光子１０１および検光子１０２との位置関係が固定されていなければならない。このため、基板１０３の上下方向のずれ、傾斜または振動等がある場合、薄膜の膜厚の測定が不可能になる。特にサイズが数百ｍｍ角以上と大型で、かつ０．５〜１．１ｍｍ程度の薄型のガラス基板を用いた液晶表示装置の製造ラインでは、基板の大きなそり（部分傾斜）や振動などが生じる。このため、インラインで膜厚測定装置を用いるためには、部分傾斜や振動の影響を受けないように、安定した大型のステージの設置が必要になる。また、偏光子１０１、検光子１０２および基板１０３の位置関係を精度良く設置して、光軸を合わせ込む必要がある。そのため、基板１０３上の複数箇所を同時に測定するのが困難であったり、インラインで限られたスペースに組込むことが不可能である。
【００１６】
また、上述したダミー基板上に成膜を行い、その薄膜の任意の点の膜厚を測定する方法では、ダミー基板に対する成膜を行なう工程が余分に必要となり、余分な膜厚測定処理が必要となる。このため、１つの製品に対する膜厚測定箇所を減少せざるを得なくなる。よって、膜厚異常の見落としや、異常発見が遅れたりすることにより、膨大な損害が生じる場合があった。
【００１７】
また、各種電子部品では、基板と薄膜との間に配線やその他の金属膜などの微細なパターンが形成されている。その影響をある程度小さくして膜厚を測定する方法として、上述した光干渉法であるピーク・バレイ法が挙げられる。しかし、ピーク・バレイ法においては、測定した波長域内に光強度のピークまたはバレイが２つ以上存在しなければ、理論的に薄膜の膜厚測定が不可能である。また、光強度のピークまたはバレイが２つ以上存在する場合でも、ピークまたはバレイ付近の波長域において、薄膜による光吸収が起こると、光強度のピーク位置がずれる現象が起こる。このため、正確に膜厚測定ができない。
【００１８】
また、特開平５−１０７２６号公報に開示された膜厚測定法では、波長−光強度曲線の波形自体を解析しているため、光強度のピークまたはバレイが２つ以上なくても薄膜の膜厚測定が可能である。しかし、この測定法では、薄膜の吸収係数を考慮していない。そのため、測定波長域に薄膜の吸収がある場合には、薄膜の吸収がない波長域に測定波長域をシフトさせる必要がある。したがって、複数の薄膜を測定する際に、波長域の異なる多数の光源が必要となり、測定する薄膜の種類により光源を切換える機構が必要である。よって、膜厚測定装置が大型化し、コストが高くなる。
【００１９】
また、広範な波長域の光照射とそれに対する解析とが必要なため、膜厚測定に時間がかかる。さらに、透過性の基板のみを対象としているため、不透明基板であったり、配線などの遮光膜が薄膜と基板との間に形成されている場合には、薄膜の膜厚測定が困難であったり測定精度が落ちたりする。
【００２０】
さらにまた、基板、光源およびセンサの位置関係が固定されていなければならない。基板に上下方向のずれ、傾斜または振動などがある場合には、光路が振れたりする。このため、正確に膜厚を測定することが困難である。特にサイズが数百ｍｍ角以上と大型で、かつ０．５〜１．１ｍｍ程度の薄型のガラス基板を用いた液晶表示装置の製造ライン中では、基板の大きなそり（部分傾斜）や振動などが生じる。このため、インラインで膜厚測定を行なうためには、部分傾斜や振動の影響を受けないように安定した大型のステージの設置が必要になる。このため、膜厚測定装置が大型化する。しかも、基板およびセンサの位置関係を精度良くして光軸を合わせ込む必要がある。このため、基板内の複数箇所を同時に測定するのが困難であったり、センサをインラインで限られたスペースに組込むことが不可能である。
【００２１】
センサを移動させながら複数箇所の膜厚を測定することも考えられるが、光軸を高精度に維持しつつ、高速移動させるのは困難である。このため、測定時間がかかる。
【００２２】
また、特開平５−１０７２６号公報に開示された発明は、透過光を利用した測定法であるため、基板を挟んだ両側に光源とセンサとが設置される。このため、インラインで使用する際に、基板と光源またはセンサとの間の距離が近すぎる場合には、基板の振動や位置ずれにより、基板と光源またはセンサとが接触し、基板が割れたり、傷ついたりする。
【００２３】
また、透過光を利用して薄膜を測定するため、基板上に一定の面積率で反射膜が形成されている部分では、光が透過しにくいため、測定が困難であるという問題がある。
【００２４】
さらに、基板上に多層の薄膜が形成されている場合には、それぞれの薄膜の吸収係数を考慮しなければ各薄膜を正確に算出することができない。下層のガラス基板上に一定の面積率でパターン形成された凹凸の反射膜があり、かつ多層膜のそれぞれの境界面でも光の反射および屈折が行なわれる場合には、反射光と屈折光とが、複雑に分布する。このため、透過光の分布が複雑となり、薄膜の膜厚の測定が困難であるという問題がある。
【００２５】
本発明は、上述の課題を解決するためになされたもので、本発明の目的は、基板の部分的な傾斜や振動の影響を受けることなく安定に薄膜の膜厚測定ができる薄膜の膜厚測定装置を提供することである。
【００２６】
本発明の他の目的は、インラインで限られたスペースに組込むことができる薄膜の膜厚測定装置を提供することである。
【００２７】
本発明のさらに他の目的は、薄膜の種類や構造に関係になく、薄膜の膜厚測定を行なうことができる薄膜の膜厚測定装置を提供することである。
【００２８】
本発明のさらに他の目的は、高精度かつ短時間で膜厚測定ができる薄膜の膜厚測定装置を提供することである。
【００２９】
本発明のさらに他の目的は、基板上に一定の面積率で反射膜が形成されている部分であっても、高精度で薄膜の膜厚測定ができる薄膜の膜厚測定装置を提供することである。
【００３０】
本発明のさらに他の目的は、基板上に多層の薄膜が形成されている場合であっても、各層の薄膜の膜厚を高精度に測定可能な薄膜の膜厚測定装置を提供することである。
【００３１】
【課題を解決するための手段】
請求項１に記載の発明に係る薄膜の膜厚測定装置は、少なくとも約２２０ｎｍから８５０ｎｍの波長域を有する光源と、基板を局部的に支持するためのロボットハンドと、基板は、ロボットハンドにより支持されることにより数ミリの変位で垂れ下がり、傾き角が８度以下の部分を有し、光源からの光を導き、基板上に形成された薄膜に対してほぼ垂直に光を照射する照射手段と、薄膜または基板からの反射光を受光する受光手段と、受光手段で受光された反射光を波長ごとに分光する分光手段と、分光手段で分光された約２２０ｎｍから８５０ｎｍの波長域内の反射光の強度に基づいて、薄膜の膜厚を算出する算出手段とを含み、照射手段は、１つの光ファイバを含み、受光手段は、該光ファイバの周囲にそれぞれ配置され、基板からの反射光をそれぞれ受光する複数の光ファイバを含み、ロボットハンドは、照射手段と基板との間を１０ｍｍ以上１００ｍｍ以下の距離で基板を支持する。
【００３２】
薄膜の境界部分における反射光を利用して薄膜の膜厚測定を行なう。このため、ガラスなどの透明な基板であっても、シリコンなどの不透明な基板であっても、薄膜の膜厚測定ができ、広範な製品に対する薄膜の膜厚測定ができる。また、少なくとも約２２０ｎｍから８５０ｎｍの波長域に対する反射光強度に対して膜厚が測定される。このため、最大２つのランプ（ハロゲンランプおよび重水素ランプ）での膜厚測定が可能となる。また、少なくとも約２２０ｎｍから８５０ｎｍの波長域の反射光強度の解析により、液晶表示装置、半導体装置およびイメージセンサなどの多くの電子部品に一般的に使用されているＩＴＯ（indium tin oxide）膜、窒化シリコン膜、アモルファスシリコン膜およびｎ⁺型アモ
ルファスシリコン膜などの大半の単層膜やこれらの膜により構成される多層膜の膜厚測定が可能となる。このため、薄膜の種類や構造に関係になく、薄膜の膜厚測定を行なうことができるようになる。
さらに、ロボットハンドにより局部的に基板を支持するので、基板は自重により変位する。照射手段が、基板にほぼ垂直に光を照射するので、基板が自重により変位しても薄膜の膜厚を測定することができる。
さらに、照射手段は、１つの光ファイバを含み、受光手段は、該光ファイバの周囲にそれぞれ配置され、基板からの反射光をそれぞれ受光する複数の光ファイバを含むので、基板が傾いていたとしても、軸対象に光照射が行なわれ、反射光が複数の光ファイバのいずれかで受光される。このため、基板の傾きに影響されることなく薄膜の膜厚測定を行なうことができる。
この発明の他の局面による薄膜の膜厚測定装置は、少なくとも約２２０ｎｍから８５０ｎｍの波長域を有する光源と、基板を局部的に支持するためのロボットハンドと、基板は、ロボットハンドにより支持されることにより数ミリの変位で垂れ下がり、傾き角が８度以下の部分を有し、光源からの光を導き、基板上に形成された薄膜に対してほぼ垂直に光を照射する照射手段と、薄膜または基板からの反射光を受光する受光手段と、受光手段で
受光された反射光を波長ごとに分光する分光手段と、分光手段で分光された約２２０ｎｍから８５０ｎｍの波長域内の反射光の強度に基づいて、薄膜の膜厚を算出する算出手段とを含み、受光手段は、基板に対してほぼ垂直に反射された光を受光する位置に配置された１つの光ファイバを含み、照射手段は、該光ファイバの周囲にそれぞれ配置され、光源からの光を導き、基板上に形成された薄膜に対してほぼ垂直に光をそれぞれ照射する複数の光ファイバを含み、ロボットハンドは、照射手段と基板との間を１０ｍｍ以上１００ｍｍ以下の距離で基板を支持する。
このため、基板が傾いていたとしても、軸対象に複数の光ファイバより照射された光のうちのいずれかの反射光が、複数の光ファイバの中心に位置する１つの光ファイバで受光される。このため、基板の傾きに影響されることなく薄膜の膜厚測定を行なうことができる。
好ましくは、薄膜は、透明導電膜を含み、基板は、膜厚測定対象領域の面積の０％より大きく５０％以下の面積を有する反射膜がコーティングされており、算出手段は、反射膜での反射を無視して透明導電膜の膜厚を算出する。
膜厚測定対象となっている薄膜の下層に屈折率の近似した薄膜が存在していても、測定対象の薄膜の下層に反射膜を設けることにより、屈折率の近似した薄膜の影響を受けることなく、薄膜の測定を正確に行なうことができる。
また、本願発明の発明者は、着目する層の下層はすべてガラス基板などからなる透過性基板であると仮定して薄膜の膜厚測定を行なうと、薄膜の膜厚測定を正確に行なうことができることを実験的に確認した。
好ましくは、薄膜は、透明導電膜を含み、基板は、膜厚測定対象領域の面積の５０％より大きく１００％以下の面積を有する反射膜がコーティングされており、算出手段は、下層の薄膜への光透過の影響を無視して前記透明導電膜の膜厚を算出する。
本願発明の発明者は、着目する層がＩＴＯ層などの透明導電膜であり、ＩＴＯ層の下層にＴａの反射膜が形成されている場合には、ＩＴＯ層の下層に一様な反射膜があると仮定して薄膜の膜厚測定を行なうと、薄膜の膜厚測定を正確に行なうことができることを実験的に確認した。
好ましくは、反射膜は、タンタル、チタニウム、アルミニウム、クロムまたはモリブデンを主成分とする金属膜または合金膜である。
これらの材料は、半導体装置や液晶表示装置などに一般的に使用される材料である。このため、着目する薄膜の下層の反射膜として使用することにより、反射膜を新たに形成するための材料や工程が不要となる。
【００４３】
好ましくは、照射手段は、基板に対してほぼ垂直に光を照射する位置に配設され、受光手段は、基板に対してほぼ垂直に反射された光を受光する位置に配設される。
【００４４】
照射手段および受光手段を基板に対してそれぞれほぼ垂直に設けることにより、照射手段および受光手段を一体化して既存ラインの空きスペースなどに組込むことが可能となる。また、光の入射角がほぼ直角であることより、反射光の光路ずれが少なくなる。このため、基板の振動や傾斜、基板と照射手段および受光手段との間の距離などに影響されることなく薄膜の膜厚測定が可能となる。
好ましくは、照射手段は、光源からの光を導き、基板上に形成された薄膜に対して照射する光ファイバを含み、受光手段は、基板からの反射光を受光し、受光した反射光を分光手段に導く光ファイバを含む。
光ファイバのみで照射手段および受光手段を構成できる。このため、薄膜の膜厚測定装置を小型化することができ、既存または新規であってもラインの空きスペース等を利用して容易に組込むことができる。
【００４５】
好ましくは、照射手段は、１つの光ファイバを含み、受光手段は、光ファイバの周囲にそれぞれ配置され、基板からの反射光をそれぞれ受光する複数の光ファイバを含む。
【００４６】
基板が傾いていたとしても、軸対象に光照射が行なわれ、反射光が複数の光ファイバのいずれかで受光される。このため、基板の傾きに影響されることなく薄膜の膜厚測定を行なうことができる。
【００４７】
好ましくは、受光手段は、基板に対してほぼ垂直に反射された光を受光する位置に配置された１つの光ファイバを含み、照射手段は、光ファイバの周囲にそれぞれ配置され、光源からの光を導き、基板上に形成された薄膜に対してほぼ垂直に光をそれぞれ照射する複数の光ファイバを含む。
【００４８】
基板が傾いていたとしても、軸対象に複数の光ファイバより照射された光のうちのいずれかの反射光が、複数の光ファイバの中心に位置する１つの光ファイバで受光される。このため、基板の傾きに影響されることなく薄膜の膜厚測定を行なうことができる。
【００４９】
好ましくは、１つの光ファイバおよび複数の光ファイバは同一径を有する円柱構造の光ファイバであり、複数の光ファイバは、６つの光ファイバを含む。
【００５０】
すべての光ファイバが円柱構造である。このため、外部から圧力をかけるだけで簡単に光ファイバの被膜をはがすことができる。また、１つの光ファイバの周囲に６つの光ファイバを並べるだけで照射手段および受光手段を組立てることができる。このため、最適な光ファイバの位置決めを容易に行なうことができる。
【００５１】
好ましくは、算出手段は、基板の屈折率をｎ₀、薄膜の屈折率をｎ₁、空気の屈折率をｎ₂、光の波長をλ、薄膜の吸収係数をｋ、および光の波長λにおける光の反射強度をＲとすると、分光手段で分光された反射光の強度に基づいて、式（２）〜式（７）によって薄膜の膜厚ｄを算出する。
【００５２】
【数４】

【００５３】
式（２）は薄膜の吸収係数ｋを考慮した式となっている。このため、光が吸収される波長域であっても薄膜の膜厚測定ができるなど、光源の波長域を制限することなく、高精度かつ短時間で膜厚測定ができる。よって、ラインのタクトを落とすことなく、薄膜の膜厚測定が可能となり、インラインでの使用が可能となる。
【００５４】
好ましくは、算出手段は、基板の屈折率をｎ₀、基板からｐ層目の薄膜の屈折率をｎ（ｐ）、空気の屈折率をｎ（ｐ＋１）、光の波長をλ、ｐ層目の薄膜の吸収係数をｋ（ｐ）とすると、分光手段で分光された反射光の強度に基づいて、式（８）〜式（１２）によってｐ層目の薄膜の膜厚ｄ（ｐ）を算出する。
【００５５】
【数５】

【００５６】
式（８）は、各層の薄膜の吸収係数ｋ（ｐ）を考慮した式となっている。このため、光が吸収される波長域であっても多層膜からなる薄膜の膜厚測定ができるなど、光源の波長域を制限することなく、高精度かつ短時間で膜厚測定ができる。このため、ラインのタクトを落とすことなく、薄膜の膜厚測定が可能となり、インラインでの使用が可能となる。
好ましくは、光源は、同一の筐体内に設けられた、波長域の異なる複数のランプを含む。
複数のランプを同一の筐体内に設けることにより、それぞれ個別の筐体内に設ける場合に比べ、基板へ照射する光の切換が簡単になり、光源から光を導く照射手段の構造を簡単にすることができる。このため、薄膜の膜厚測定装置を小型化することができる。
好ましくは、光源は、それぞれ異なる筐体内に設けられた、波長域の異なる複数のランプを含む。
好ましくは、複数のランプは、重水素ランプおよびハロゲンランプを含む。
好ましくは、複数のランプは、それぞれ独立に点灯可能である。
複数のランプをそれぞれ独立に点灯させることにより、ランプの点灯の組合わせを変化させ、様々な波長域を有する光を薄膜に対して照射することができる。よって、薄膜の材質に応じて適切な波長域の光を選択することにより、薄膜の膜厚測定を適切に行なうことができる。
【００６５】
【発明の実施の形態】
［実施の形態１］
図１は、本発明の実施の形態１における薄膜の膜厚測定装置の概略構成を説明するための図である。この薄膜の膜厚測定装置は、光源１と、光源１からの光を基板３上の複数箇所（ここでは２箇所）に導き、それぞれの箇所における基板３からの反射光を受光する分岐型光ファイバ２と、基板３の複数箇所に導く入射光と、基板３の複数の反射光とを選択的に遮断する光制限シャッタ４と、分岐型光ファイバ２によって導かれた反射光を波長ごとの光強度に分解する分光器５と、波長ごとの光強度を解析して薄膜の膜厚を算出する計算機６とを含む。
【００６６】
光源１には、たとえば可視光線波長域（４００〜８００ｎｍ）に近い波長域（４００〜８５０ｎｍ）を有するハロゲンランプのみを用いる。ただし、他のランプをハロゲンランプと同一の光源室内または別の光源室内に設け、同時に点灯させて使用したり、切換えて点灯させて使用してもよい。また、分光器５等の光学部品には、その波長域をカバーできる部品が使用される。
【００６７】
図２は、分岐型光ファイバ２の概略構成を説明するための図である。この分岐型光ファイバ２は、光源１からの光を基板３上に導く光ファイバ２ａと、光源１からの光を基板３上の測定点▲１▼に導き、基板３上の測定点▲１▼からの反射光を分光器５へ導く光ファイバ２ｂと、光源１からの光を基板３上の測定点▲２▼に導き、基板３上の測定点▲２▼からの反射光を分光器５へ導く光ファイバ２ｃと、基板３上の測定点▲１▼からの反射光および測定点▲２▼からの反射光を分光器５へ導く光ファイバ２ｄとを含む。
【００６８】
図３は、分岐型光ファイバ２をさらに詳細に説明するための図である。光ファイバ２ａは、２群の光ファイバ２ａａおよび２ａｂを含む。光ファイバ２ａａは、光源１からの光を基板３上の測定点▲１▼へ導く。光ファイバ２ａｂは、光源１からの光を基板３上の測定点▲２▼へ導く。
【００６９】
光ファイバ２ｂは、２群の光ファイバ２ｂａおよび２ｂｂを含む。光ファイバ２ｂａは、光源１からの光を基板３上の測定点▲１▼へ導く。光ファイバ２ｂｂは、基板３上の測定点▲１▼からの反射光を分光器５へ導く。
【００７０】
光ファイバ２ｃは、２群の光ファイバ２ｃａおよび２ｃｂを含む。光ファイバ２ｃａは、光源１からの光を基板３上の測定点▲２▼へ導く。光ファイバ２ｃｂは、基板３上の測定点▲２▼からの反射光を分光器５へ導く。
【００７１】
光ファイバ２ｄは、２群の光ファイバ２ｄａおよび２ｄｂを含む。光ファイバ２ｄａは、基板３上の測定点▲１▼からの反射光を分光器５へ導く。光ファイバ２ｄｂは、基板３上の測定点▲２▼からの反射光を分光器５へ導く。
【００７２】
図４は、光制限シャッタ４の概略構成を説明するための図である。この光制限シャッタ４は、図３に示す光ファイバ２ｂおよび２ｃのそれぞれの途中に設けられている。すなわち、光ファイバ２ａと２ｃとの接続点（光ファイバ２ｄと２ｂとの接続点）２ｘと測定点▲１▼および▲２▼との間にそれぞれ設けられている。光ファイバ２ｂの途中に設けられた光制限シャッタ４ｂは、その開閉によって基板３上の測定点▲１▼への入射光および測定点▲１▼からの反射光の通過および遮断の切換を制御する。光ファイバ２ｃの途中に設けられた光制限シャッタ４ｃは、その開閉によって基板３上の測定点▲２▼への入射光および測定点▲２▼からの反射光の通過および遮断の切換を制御する。光制限シャッタ４ｂおよび４ｃの一方を閉じ、他方を開くことによって、基板３上の測定点▲１▼および▲２▼からの反射光の一方のみを選択して分光器５に導くことが可能である。また、光制限シャッタ４ｂおよび４ｃを同時に開くことによって、基板３上の測定点▲１▼および▲２▼での膜厚の平均値を測定することも可能である。
【００７３】
図５は、計算機６が実行する膜厚測定処理の処理手順を説明するためのフローチャートである。まず、分光器５によって基板３からの反射光を波長ごとの光強度（スペクトル）に分解する（Ｓ１）。計算機６は、分光器５から波長ごとのスペクトルデータを取得し（Ｓ２）、後述する理論式を用いて薄膜の膜厚を算出する（Ｓ３）。計算機６は、求められた膜厚を計算機６の画面上に表示し、データを蓄積保存する（Ｓ４）。計算機６は、蓄積されたデータを集中制御機（図示せず）に転送する（Ｓ５）。
【００７４】
計算機６より薄膜の膜厚に関するデータを受信した集中制御機は、薄膜の膜厚が予め定められた基準値を超えた場合や、基板内での測定点間の膜厚の差が大きい場合や、ある測定点における膜厚の時間的な変化が大きい場合などに、警報を出すなどの異常発生に対する処理を行なう。
【００７５】
ここで、薄膜の膜厚解析法の一例を説明する。基板の屈折率をｎ₀、薄膜の屈折率をｎ₁、空気の屈折率をｎ₂、薄膜の吸収係数をｋ、薄膜の膜厚をｄ、光源の波長をλとすると、基板からの反射光強度Ｒは式（２）〜（７）で表すことができる。
【００７６】
光学定数ｎおよびｋは、光の波長λによって変化する値である。予め定められた複数の代表波長または波長サンプリングを行なうことにより（たとえば、４００ｎｍから８５０ｎｍまで５ｎｍ刻みでサンプリングを行なうことにより）、光学定数ｎおよびｋを変化させ、各波長λごとに、式（２）〜（７）より想定される膜厚に応じその上下限値をあらかじめ設定し、上下限値の範囲内で薄膜の膜厚ｄを求める。すべての波長における薄膜の膜厚ｄを平均することにより、薄膜の膜厚を求める。
【００７７】
光学定数ｎおよびｋが既知でない場合には、光学定数ｎおよびｋならびに薄膜の膜厚ｄを以下の▲１▼〜▲３▼のようにして求めることができる。
▲１▼ 値を求める対象である薄膜の膜厚ｄ、薄膜の屈折率ｎ₁、および薄膜の吸収係数ｋについて、初期値として大まかな数値（たとえば、想定される膜厚、代表波長における屈折率および吸収係数など）を式（２）に代入する。
▲２▼ 次に、それぞれのパラメータｄ，ｎ₁，ｋの上限値および下限値を設定する。たとえば、膜厚ｄであれば、初期値として想定する膜厚の±５０％の値を上限値および下限値として設定する。
▲３▼ パラメータｄ，ｎ₁，ｋをそれぞれの上限値および下限値の範囲内で変化させて式（２）に代入し、その結果得られる曲線が実測の波長−光強度の曲線に最も近づくように各パラメータの値を算出する。より具体的には、両曲線の光強度の差を各波長ごとに求め、測定波長域におけるその差の２乗の総和が最も小さくなるようにパラメータを変化させることで各パラメータを求めることができる。この手法によって、光学定数ｎおよびｋと薄膜の膜厚ｄとを同時に求めることが可能となる。
【００７８】
また、基板上に多層の薄膜が成膜される場合にも、上述した手法と同様にして各層の薄膜の膜厚を算出することができる。ここで、基板の屈折率をｎ（０）、基板からｐ層目の薄膜の屈折率をｎ（ｐ）、空気の屈折率をｎ（ｐ＋１）、基板からｐ層目の薄膜の吸収係数をｋ（ｐ）、基板からｐ層目の薄膜の膜厚をｄ（ｐ）、光源の波長をλとすると、基板からの反射光強度Ｒ（ｐ＋１，０）とこれらのパラメータとの間には式（８）〜（１２）に示される関係が成立つ。
【００７９】
基板から一層目の薄膜、二層目の薄膜…と順次理論式に値を代入することにより、すなわち、ｐに１，２…を順次代入することによって、薄膜が何層であってもそれぞれの薄膜の光学定数（ｎ（ｐ），ｋ（ｐ））および膜厚ｄ（ｐ）を求めることができる。ただし、光学定数の近い薄膜同士が隣接して積層されている場合には、それらの薄膜を同一層として解析が行なわれる。薄膜の数が増加するにつれパラメータ数も増加するため、演算に要する時間も増加することになる。また、薄膜の数が増加するにつれ実際の値との誤差が大きくなる。しかし、本願発明者の検討によれば、液晶表示装置においては、３層程度でもインラインで測定可能であることを確認した。
【００８０】
基板上の測定箇所は、液晶表示装置の異常を予知するためには１点でもよいが、１ｍ角以上の大きさの液晶表示装置用の基板では、薄膜の膜厚が部分的に異なる場合が多く、局所的な膜厚異常がまれに生じる。このため、１枚の基板に対して３〜５点程度の測定をすることが望ましい。
【００８１】
図６（ａ）は本実施の形態における薄膜の膜厚測定装置の設置の一例を示す側面図であり、図６（ｂ）はその平面図である。図６（ａ）に示すように、図１に示す分岐型光ファイバ２が内部に設けられたセンサユニット１０が、成膜装置内部に設けられた支柱１０ａに固定される。分岐型光ファイバ２は、支柱１０ａ内部に引きめぐらされる。センサユニット１０は、成膜装置のゲート開口部（以下、「ゲートバルブ」という。）１３の近傍に位置する基板３に対して、ほぼ垂直に光照射を行なうように取付けられている。基板３の移動中またはメンテナンス中に、基板３がセンサユニット１０に接触しないように、両者の距離は１０ｍｍ以上必要であるが、測定精度を維持するためには、約１００ｍｍ〜数１０ｍｍ以下にすることが好ましい。
【００８２】
この成膜装置は、たとえば、ＣＶＤ（Chemical Vapor Deposition）装置であって、複数枚単位で成膜を行ない、成膜した複数の基板をそれぞれトレイに納めていく。この複数の基板は、図６（ｂ）に示すアンロード室のゲートバルブ１３内部に設けられたロードロック１４内に貯えられている。基板搬送用ロボット１１は、ロードロック１４から基板を１枚ずつ取り出してロボットハンド１２上に載せて、センサユニット１０の真下に基板３が位置するように移動させる。１枚の基板中に複数の測定点がある場合には、ロボット１１は、ある測定点の測定が終了するたびに次の測定点がセンサユニット１０の真下にくるように、順次、基板３の移動を繰返す。基板３が移動するごとにセンサユニット１０は、各測定点に対する膜厚の測定を行なう。なお、図６（ｃ）に、ロボットハンド１２の形状を示す。基板３は、おおむねコの字型で支えられる場合が多く、基板３が支持される点から遠ざかるにつれ、基板３は、自身の重みにより垂れ下がる。このため、基板３は数ｍｍ程度相対位置がずれたり、多少傾いたりしている。よって、膜厚測定装置は、このようなずれや傾斜に対して測定精度を維持する必要がある。
【００８３】
次に、センサユニット１０の構造の詳細を説明する。センサユニット１０の先端には、図２および図３を参照して説明した上述の光ファイバ２ｂおよび光ファイバ２ｃが設けられている。
【００８４】
光ファイバ２ｂは、上述のように光ファイバ２ｂａおよび２ｂｂを含むが、図７に示すように光ファイバ２ｂａを６つの光ファイバより構成し、光ファイバ２ｂｂの周囲に配置させる。また、光ファイバ２ｂｂと６つの光ファイバ２ｂａとは同一径とする。このような構造にすることにより、図８を参照して、光ファイバ２ｂｂの周囲に６つの光ファイバ２ｂａを配置し、それらを治具で固定させるだけで、光ファイバ２ｂｂおよび光ファイバ２ｂａを互いに平行にすることができる。このため、光ファイバ２ｂの組立が容易になる。また、膜厚測定時に基板３が傾いていたとしても、６つの光ファイバ２ｂａのいずれかより照射された光の反射光が光ファイバ２ｂｂで受光される。このため、基板３の傾きに影響されることなく薄膜の膜厚を測定することができる。
【００８５】
光ファイバ２ｃも図７と同様に構成される。
図９〜図１１は、基板の上下方向のずれ、傾斜および振動が測定値に与える影響をそれぞれ説明するための図である。基板上には、ＧＩ層（窒化シリコン）、ｉ層（アモルファシスシリコン）およびｎ⁺層（ｎ⁺型アモルファスシリコン）の３層が成膜されているものとする。図９は、センサユニット１０と基板３との間の距離を横軸に、上述の膜厚測定装置によって測定された薄膜の膜厚を縦軸にとったグラフを示している。図９から分かるように、ＧＩ層、ｉ層およびｎ⁺層が堆積した多層構造においても、それぞれの層が距離の移動による変動をほとんど生じることなく測定されている。なお、上述のように基板３の反りによって、センサユニット１０と基板３との間の距離には、数ｍｍ程度のずれが生じているが、この影響を受けることなく薄膜の膜厚の測定が可能である。
【００８６】
図１０は、センサユニット１０に対する基板３の傾斜角を横軸に、上述の膜厚測定装置により測定された膜厚を縦軸にとったときのグラフを示している。傾斜角が３〜４°以上になると、受光される反射光は、傾斜角が０°の場合に比べ５０％以下となるが、図１０からもわかるように、ＧＩ層、ｉ層およびｎ⁺層が積層された多層構造においても、８°以下の基板３の傾きであれば（より好ましくは２°以下の基板３の傾きであれば）、比較的高精度に薄膜の膜厚を測定することができる。
【００８７】
図１１は、基板３の上下振動の影響を示したグラフである。上下の振幅４ｍｍ、振動数５Ｈｚの条件で１０秒ごとに反射光の強度を測定した。図１１のグラフは、測定時間を横軸にとり、上述の膜厚測定装置によって測定された反射光の反射強度を縦軸にとっている。図１１からもわかるように、反射強度は振動を加えても安定していることがわかる。
【００８８】
図１２に示すようなタンタル（Ｔａ）からなる反射膜を覆うように上述のＧＩ層、ｉ層およびｎ⁺層が堆積された３層構造の各層の膜厚を測定した。この時、着目する層の下層はすべてガラス基板であると仮定して、膜厚の測定が行なわれる。図１３は、反射膜が存在しない部分、反射膜が１０％程度存在する液晶表示装置の表示部内部および反射膜が５０％程度存在する液晶表示装置の表示部周辺におけるＧＩ層、ｉ層およびｎ⁺層の膜厚を示している。ＧＩ層、ｉ層およびｎ⁺層におけるバラツキは、それぞれ±２．５％，±１．３％，±１．０％程度であり、各層の膜厚の測定結果は安定している。これは、基板３に対してほぼ垂直の光を当てることにより、光の屈折の影響が低減され、反射膜のエッジ部において光の反射方向が変化してしまう影響が低減されたためである。
【００８９】
なお、上述の薄膜の膜厚を求める際に光源１として用いられるハロゲンランプは、時間が経つとともに光量および波長分布が変化する。このため、反射光強度Ｒを求める際には、定期的に光源１の照射光のスペクトルを全反射基板を用いて求め、各種パラメータを修正しておくことが好ましい。
【００９０】
なお、図１４に示すように、光ファイバ２ｂｂを６つの光ファイバより構成し、同一径の光ファイバ２ｂａの周囲に配置させて光ファイバ２ｂを構成してもよい。このような構造とすることにより、光ファイバ２ｂの組立が容易になる。また、膜厚測定時に基板３が傾いていたとしても、光ファイバ２ｂａより照射された光の反射光が６つの光ファイバ２ｂａのいずれかで受光される。このため、基板３の傾きに影響されることなく薄膜の膜厚を測定することができる。光ファイバ２ｃを同様の構成としてもよい。
【００９１】
以上のように本実施の形態にかかる薄膜の膜厚測定装置は、センサユニット１０部分の構造が極めて簡単である。このため、小型化が可能となる。
【００９２】
また、膜厚の測定を解析する際、波長−光強度曲線のみで解析が行える。このため、多層膜や多点計測においても短時間で薄膜の膜厚を測定することができる。
【００９３】
また、膜厚測定装置がコンパクトなため、製造ラインに組込みやすい。さらに、短時間で膜厚の測定が可能なため、成膜直後に膜厚を測定することができるようになり、製造中の異常発生から発見までのタイムラグを短くすることができ、不良発生による損害を最小限に食止めることができる。
【００９４】
また、膜厚のデータを蓄積保存し、そのデータを解析することによって、成膜装置または成膜材料などの寿命、成膜装置の適切なメンテナンス時期、および成膜条件変更の時期などを予測することができる。そのため、突発的なメンテナンスを回避することができ、安定した成膜装置の稼動が可能となる。
【００９５】
［実施の形態２］
本発明の実施の形態２に係る薄膜の膜厚測定装置は、実施の形態１に係る薄膜の膜厚測定装置と同様である。このため説明は繰返さない。本実施の形態では、１００ｎｍ（＝１０００Å）以下の膜厚の透明導電膜であるＩＴＯ膜の膜厚を測定する場合について説明する。液晶表示装置に一般的に用いられるＩＴＯ膜は画素電極として用いられる。図１５は、透過型の液晶表示装置の画素部の断面構造を示している。このような構造では、膜厚が薄いＩＴＯ膜の特性が反射光強度の分布として現れにくい。このため、実施の形態１で示した評価方法では、ＩＴＯ膜の膜厚測定は困難である。
【００９６】
しかし、液晶表示装置などにおいては、例えば駆動用ドライバなどを実装する端子部などでＩＴＯ膜の下層にＴａなどの反射膜が形成される場合が多い。下層にＴａなどの反射膜があると、反射光強度の分布が安定し、その部分で高精度の測定が可能となる。反射膜の面積は、総面積に対して５０％以上であるものとする。
【００９７】
図１６に実施の形態１と同様のハロゲンランプ（波長域約４００ｎｍ〜約８５０ｎｍ）からなる光源１を用いて、ＩＴＯ膜の膜厚を測定した結果を示す。横軸に生産条件における設定膜厚をとり、縦軸に膜厚測定装置での測定結果を示す。薄膜の膜厚が６０ｎｍ（＝６００Å）の場合には膜厚の測定値が安定している。ＩＴＯ膜の膜厚が６０ｎｍ以外の場合には、測定値のバラツキが大きい。このため、膜厚異常を検出することが困難になる。
【００９８】
このため、光源１として、ハロゲンランプおよび重水素ランプを用い、同一の光源室に入れ、同時点灯させた状態（波長域約２２０ｎｍ〜約８５０ｎｍ）で、ＩＴＯ膜の膜厚を測定した。その結果、図１７に示すようなグラフが得られた。このグラフからもわかるように、いずれの膜厚においても測定値のバラツキが小さく、生産条件における設定膜厚と測定値との相関性が高い。ただし、設定膜厚と測定値との間には、若干の値のずれが生じている。これは、計算速度を増すために、吸収係数ｋ（ｐ）を波長ごとに一定としたこと（ＩＴＯ層の下層に一様な反射膜があると仮定したこと）などによるものである。このため、予め、設定膜厚と測定値との関係が分かっていれば、測定値を補正することによって、正確な膜厚測定が可能となる。ただし、膜厚測定装置をインラインで使用し膜厚異常を検出する場合には、測定点における膜厚の時間的な変化のみがわかればよい。このような場合には、測定値の補正は必要なくなる。
【００９９】
以上説明したように、本実施の形態における膜厚測定装置では、ハロゲンランプおよび重水素ランプを同時点灯させた光源１を用いることにより、波長域が約２２０ｎｍ〜約８５０ｎｍの波長域の光に対する膜厚測定が行なわれる。一般に、膜厚が薄い膜を測定するには、波長の短い光を用いて膜厚測定を行なわなければならない。このため、重水素ランプを同時点灯させることにより、ハロゲンランプのみを用いた場合に比べ、正確にＩＴＯ膜の膜厚測定を行なうことができる。
【０１００】
今回開示された実施の形態はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。
【図面の簡単な説明】
【図１】 本発明の実施の形態１における薄膜の膜厚測定装置の概略構成を説明するための図である。
【図２】 分岐型光ファイバ２の概略構成を説明するための図である。
【図３】 分岐型光ファイバ２をさらに詳細に説明するための図である。
【図４】 光制限シャッタの概略構成を説明するための図である。
【図５】 本発明の実施の形態１における薄膜の膜厚測定装置の処理手順を説明するためのフローチャートである。
【図６】 本発明の実施の形態１における薄膜の膜厚測定装置の設置の一例を示す図である。
【図７】 光ファイバ２ｂの構成を示す図である。
【図８】 光ファイバ２ｂの構成を示す図である。
【図９】 センサユニットと基板との間の距離を変化させたときの薄膜の膜厚測定結果を示すグラフである。
【図１０】 センサユニットに対する基板の傾斜角を変化させたときの薄膜の膜厚測定結果を示すグラフである。
【図１１】 基板に上下振動を与えたときにセンサユニットに入射する反射光の強度の時間変化を示すグラフである。
【図１２】 Ｔａからなる反射膜を覆うようにＧＩ層、ｉ層およびｎ⁺層が堆積された３層構造を示す図である。
【図１３】 反射膜の面積比を変化させたときの薄膜の膜厚測定結果を示すグラフである。
【図１４】 光ファイバ２ｂの構成を示す図である。
【図１５】 透過型の液晶表示装置の画素部の断面構造を示す図である。
【図１６】 ハロゲンランプを光源として用いたときのＩＴＯ膜の膜厚測定結果を示すグラフである。
【図１７】 ハロゲンランプおよび重水素ランプを光源として用いたときのＩＴＯ膜の膜厚測定結果を示すグラフである。
【図１８】 従来のエリプソメータを用いて膜厚を測定する方法を説明するための図である。
【図１９】 膜厚の測定ができない基板の一例を示す図である。
【図２０】 従来の光干渉法の一例を説明するための図である。
【図２１】 反射光の波長と光強度との関係の一例を示す図である。
【符号の説明】
１ 光源、２ 分岐型光ファイバ、２ａ，２ｂ，２ｃ，２ｄ，２ａａ，２ａｂ，２ｂａ，２ｂｂ，２ｃａ，２ｃｂ，２ｄａ，２ｄｂ 光ファイバ、３，１０６基板、４，４ｂ，４ｃ 光制限シャッタ、５ 分光器、６ 計算機、１０ センサユニット、１０ａ 支柱、１１ ロボット、１２ ロボットハンド、１３ ゲートバルブ、１４ ロードロック、１０１ 偏光子、１０２ 検光子、１０３薄膜形成基板、１０４ 薄膜層、１０５ 配線パターン。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film thickness measuring apparatus. In particular, the present invention relates to a thin film thickness measuring apparatus for measuring the thickness of various thin films formed on a substrate such as a glass substrate or a semiconductor wafer substrate when manufacturing a liquid crystal display device or a semiconductor device.
[0002]
[Prior art]
In recent years, thin film formation techniques such as a plasma process method and a sputtering method have been widely used in the manufacture of electronic components such as semiconductor devices and liquid crystal display devices. By detecting various characteristics of the thin film formed by this thin film formation technique, various parameters for forming the thin film are derived, and various defects during the thin film formation are quickly detected.
[0003]
In particular, the thickness of the thin film affects not only the properties of the thin film, such as conductivity or insulation, but also the disconnection and short-circuit failure of the wiring film formed on the upper layer of the thin film, so the product yield and reliability It is an important management item in determining
[0004]
Conventionally, when measuring the film thickness of a thin film formed by a thin film forming apparatus, it takes a lot of time to measure the film thickness, and the measuring apparatus is also large, so measurement is mainly performed offline. It was. As a method for measuring the thickness of the thin film, various methods such as a stylus method for directly measuring a level difference of the thin film and a measurement method using an ellipsometer are used.
[0005]
FIG. 18 shows a schematic configuration of a film thickness measuring apparatus using an ellipsometer. The thin film measuring apparatus includes a polarizer 101 and an analyzer 102. The light from the light source is irradiated on the thin film forming substrate 103 which is polarized by the polarizer 101 and becomes a workpiece. The light reflected by the substrate 103 is received by the analyzer 102, and the polarization state of the reflected light is detected by the detector. The detector determines the optical constant (refractive index, extinction coefficient) of the film thickness by comparing the polarization state of the incident light and the polarization state of the reflected light.
[0006]
However, as shown in FIG. 19, when the thin film layer 104 covers the wiring pattern 105 such as metal and is formed on the substrate 106, there is a delicate unevenness in the portion, so that the film is not used in the measurement method described above. Thickness cannot be measured.
[0007]
Therefore, a specific region without the wiring pattern 105 is selected, and film formation is performed on the region, or film formation is performed on a dummy substrate without the wiring pattern, and the film thickness at an arbitrary point of the thin film is measured. Then, the film formation conditions were determined so as to eliminate the defects of the thin film on the dummy substrate, and the film formation was performed on the assumption that the same film formation was performed by applying the film formation conditions to the actual product. .
[0008]
In addition, as a measurement technique that is less affected by unevenness on the substrate, there is a technique using light interference. In this optical interference method, the film thickness of a thin film is measured by analyzing a spectral spectrum of light reflected by the substrate or transmitted through the substrate.
[0009]
An example of the optical interferometry will be described with reference to FIG. Light emitted from the light source is reflected by the substrate 103. This reflected light reflected on the surface side of the substrate 103 is composed of light (1) reflected on the surface of the thin film 104 and light (2) reflected on the surface of the main body portion 106 of the substrate 103 excluding the thin film 104. It has been done.
[0010]
FIG. 21 is a graph showing the relationship between the wavelength and the light intensity of the reflected light shown in FIG. 20 detected by the spectroscope. In this graph, the horizontal axis represents the wavelength of the reflected light, and the vertical axis represents the light intensity. The light {circle around (1)} and the light {circle around (2)} interfere with each other, and the light intensity is apparently increased or decreased with respect to the wavelength of the reflected light. Since this light interference occurs due to the optical path difference between the light (1) and the light (2), it depends on the film thickness of the thin film 104 and the irradiation angle of the light. It varies depending on the film thickness of the thin film 104. Therefore, the film thickness of the thin film 104 can be obtained by analyzing the curve shape of the wavelength-light intensity of the graph.
[0011]
As a technique for analyzing a wavelength-light intensity relationship curve as shown in FIG. 21, there is a technique called a peak-valley method. In this method, the wavelength at which the light intensity reaches a peak (points a and b in FIG. 21) in the wavelength-light intensity relationship curve is obtained, and the film thickness of the thin film is obtained from the relational expression.
[0012]
Japanese Patent Laid-Open No. 5-10726 discloses an invention of a film thickness measuring method using transmitted light as a film thickness measuring method using a wavelength-light intensity relationship curve. In this measurement method, a light source and a sensor are used to obtain a wavelength-light intensity relationship curve of light transmitted through a transparent substrate. In addition, instead of simply determining the wavelength at which the light intensity reaches a peak as in the peak-valley method, the thin film is formed so that the relationship curve is closest to the wavelength-light intensity theoretical relationship curve obtained from the theoretical formula described later. The film thickness is measured by changing the thickness and the refractive index. T is the transmittance of the thin film, n 'is the refractive index of the thin film, n'₀Is the refractive index of air, n '₁Is the refractive index of the transparent substrate, r₀Amplitude reflectance when light is incident on the thin film from the air, r₁Is the amplitude reflectivity when light is incident on the transparent substrate from the thin film, δ is the phase shift when the light travels through the thin film, δ₀Phase shift when light is incident on the thin film from the air, δ₁Is a phase shift when light is incident on the transparent substrate from the thin film, the following relationship is established.
[0013]
[Equation 3]

[0014]
Since the phase shift δ when light is transmitted through the thin film depends on the film thickness d of the thin film and the wavelength λ of the light, the relationship between the wavelength λ and the transmittance T of the thin film is obtained from equation (1). Can do. Therefore, by changing the thin film thickness d and the thin film refractive index n ′, the wavelength-light intensity theoretical relationship curve obtained from the equation (1) is closest to the wavelength-light intensity measurement relationship curve, The thickness d of the thin film and the refractive index n ′ of the thin film are measured values.
[0015]
[Problems to be solved by the invention]
In the film thickness measuring apparatus using the ellipsometer shown in FIG. 18, the positional relationship between the substrate 103, the polarizer 101, and the analyzer 102 must be fixed. For this reason, when there is vertical displacement, inclination or vibration of the substrate 103, the film thickness of the thin film cannot be measured. In particular, in a production line of a liquid crystal display device using a large glass substrate of several hundred mm square or more and a thin glass substrate of about 0.5 to 1.1 mm, a large warp (partial tilt) or vibration of the substrate occurs. . For this reason, in order to use the film thickness measuring device in-line, it is necessary to install a stable large stage so as not to be affected by partial inclination or vibration. Further, it is necessary to set the positional relationship among the polarizer 101, the analyzer 102, and the substrate 103 with high accuracy and to align the optical axes. For this reason, it is difficult to measure a plurality of locations on the substrate 103 at the same time, or it is impossible to incorporate in a limited space in-line.
[0016]
Further, in the method of forming a film on the dummy substrate described above and measuring the film thickness at an arbitrary point of the thin film, an extra film forming process is required on the dummy substrate, and an extra film thickness measurement process is required. It becomes. For this reason, the film thickness measurement location for one product must be reduced. Therefore, an enormous amount of damage may occur due to oversight of the film thickness abnormality or delay in finding the abnormality.
[0017]
Further, in various electronic components, a fine pattern such as wiring or other metal film is formed between the substrate and the thin film. As a method for measuring the film thickness by reducing the influence to some extent, the peak-valley method, which is the optical interference method described above, can be mentioned. However, in the peak-valley method, it is theoretically impossible to measure the thickness of a thin film unless there are two or more light intensity peaks or valleys in the measured wavelength range. Even when there are two or more light intensity peaks or valleys, if light absorption by the thin film occurs in the wavelength region near the peaks or valleys, a phenomenon occurs in which the peak position of the light intensity shifts. For this reason, the film thickness cannot be measured accurately.
[0018]
Further, in the film thickness measurement method disclosed in Japanese Patent Laid-Open No. 5-10726, since the waveform of the wavelength-light intensity curve itself is analyzed, a thin film can be obtained without two or more light intensity peaks or valleys. Thickness measurement is possible. However, this measurement method does not consider the absorption coefficient of the thin film. For this reason, when there is absorption of a thin film in the measurement wavelength range, it is necessary to shift the measurement wavelength range to a wavelength range where there is no absorption of the thin film. Therefore, when measuring a plurality of thin films, a large number of light sources having different wavelength ranges are required, and a mechanism for switching the light sources depending on the type of thin film to be measured is required. Therefore, the film thickness measuring device is increased in size and the cost is increased.
[0019]
In addition, it takes time to measure the film thickness because light irradiation in a wide wavelength range and analysis thereof are necessary. Furthermore, since only a transmissive substrate is targeted, it is difficult to measure the thickness of a thin film when it is an opaque substrate or when a light-shielding film such as wiring is formed between the thin film and the substrate. Measurement accuracy may be reduced.
[0020]
Furthermore, the positional relationship among the substrate, the light source, and the sensor must be fixed. If the substrate has vertical displacement, inclination, vibration, etc., the optical path may be shaken. For this reason, it is difficult to accurately measure the film thickness. In particular, in a production line of a liquid crystal display device using a large glass substrate of several hundred mm square or more and a thin glass substrate of about 0.5 to 1.1 mm, there is a large warp (partial inclination) or vibration of the substrate. Arise. For this reason, in order to measure the film thickness in-line, it is necessary to install a stable large stage so as not to be affected by partial inclination or vibration. For this reason, a film thickness measuring apparatus enlarges. In addition, it is necessary to align the optical axis with high accuracy in the positional relationship between the substrate and the sensor. For this reason, it is difficult to measure a plurality of locations in the substrate at the same time, or it is impossible to incorporate the sensor in a limited space in-line.
[0021]
Although it is conceivable to measure the film thickness at a plurality of locations while moving the sensor, it is difficult to move the sensor at high speed while maintaining the optical axis with high accuracy. For this reason, measurement time is required.
[0022]
Further, since the invention disclosed in Japanese Patent Laid-Open No. 5-10726 is a measurement method using transmitted light, a light source and a sensor are installed on both sides of the substrate. For this reason, when the distance between the substrate and the light source or sensor is too short when used in-line, the substrate and the light source or sensor come into contact with each other due to vibration or displacement of the substrate. I get hurt.
[0023]
In addition, since the thin film is measured using transmitted light, there is a problem that the measurement is difficult because the light is hardly transmitted in the portion where the reflective film is formed on the substrate with a constant area ratio.
[0024]
Further, when a multilayer thin film is formed on the substrate, each thin film cannot be accurately calculated unless the absorption coefficient of each thin film is taken into consideration. When there is an uneven reflective film patterned at a constant area ratio on the lower glass substrate and light is reflected and refracted at each boundary surface of the multilayer film, the reflected light and the refracted light are It is distributed in a complicated manner. For this reason, there is a problem that the distribution of transmitted light is complicated and it is difficult to measure the thickness of the thin film.
[0025]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thin film thickness capable of stably measuring a thin film thickness without being affected by partial tilt or vibration of the substrate. It is to provide a measuring device.
[0026]
Another object of the present invention is to provide a thin film thickness measuring apparatus that can be incorporated in a limited space in-line.
[0027]
Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring a thin film thickness regardless of the type and structure of the thin film.
[0028]
Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring a film thickness with high accuracy and in a short time.
[0029]
Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring a thin film thickness with high accuracy even in a portion where a reflective film is formed with a constant area ratio on a substrate. It is.
[0030]
Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring the thin film thickness of each layer with high accuracy even when a multilayer thin film is formed on a substrate. is there.
[0031]
[Means for Solving the Problems]
  A thin film thickness measuring apparatus according to claim 1 is a light source having a wavelength range of at least about 220 nm to 850 nm, a robot hand for locally supporting a substrate, and the substrate is supported by the robot hand. To be doneSag with displacement of several millimeters,A part with an inclination angle of 8 degrees or lessThe irradiation means for guiding the light from the light source and irradiating the light almost perpendicularly to the thin film formed on the substrate, the light receiving means for receiving the reflected light from the thin film or the substrate, and the light receiving means Including a spectroscopic unit that splits the reflected light for each wavelength, and a calculation unit that calculates the film thickness of the thin film based on the intensity of the reflected light in the wavelength range of about 220 nm to 850 nm that is split by the spectroscopic unit. MeansOne optical fiber is included, the light receiving means is disposed around each of the optical fibers, and includes a plurality of optical fibers that respectively receive reflected light from the substrate. The robot hand has a distance of 10 mm between the irradiation means and the substrate. The substrate is supported at a distance of 100 mm or less.
[0032]
  The film thickness of the thin film is measured using the reflected light at the boundary portion of the thin film. For this reason, even if it is a transparent substrate such as glass or an opaque substrate such as silicon, the thin film thickness can be measured, and the thin film thickness can be measured for a wide range of products. Further, the film thickness is measured with respect to the intensity of reflected light with respect to a wavelength range of at least about 220 nm to 850 nm. For this reason, the film thickness can be measured with a maximum of two lamps (halogen lamp and deuterium lamp). In addition, by analyzing the intensity of reflected light in a wavelength range of at least about 220 nm to 850 nm, an ITO (indium tin oxide) film or nitride generally used in many electronic components such as liquid crystal display devices, semiconductor devices, and image sensors. Silicon film, amorphous silicon film and n⁺Type Ammo
It is possible to measure the film thickness of most single-layer films such as Rufus silicon films and multilayer films composed of these films. Therefore, the film thickness of the thin film can be measured regardless of the type and structure of the thin film.
  Furthermore, since the substrate is supported locally by the robot hand, the substrate is displaced by its own weight. Since the irradiation means irradiates light almost perpendicularly to the substrate, the film thickness of the thin film can be measured even if the substrate is displaced by its own weight.
  Further, the irradiating means includes one optical fiber, and the light receiving means includes a plurality of optical fibers that are respectively disposed around the optical fiber and receive reflected light from the substrate, so that the substrate is inclined. In addition, light irradiation is performed on the axial object, and the reflected light is received by one of the plurality of optical fibers. For this reason, the film thickness of the thin film can be measured without being affected by the tilt of the substrate.
  A thin film thickness measuring apparatus according to another aspect of the present invention includes a light source having a wavelength range of at least about 220 nm to 850 nm, a robot hand for locally supporting a substrate, and the substrate supported by the robot hand. An irradiating means that has a portion that hangs down with a displacement of several millimeters and has an inclination angle of 8 degrees or less, guides light from the light source, and irradiates light almost perpendicularly to the thin film formed on the substrate; Or a light receiving means for receiving reflected light from the substrate and a light receiving means.
Spectroscopic means for spectrally separating the received reflected light for each wavelength, and calculation means for calculating the film thickness of the thin film based on the intensity of the reflected light in the wavelength range of about 220 nm to 850 nm spectrally dispersed by the spectroscopic means, The light receiving means includes one optical fiber disposed at a position for receiving light reflected substantially perpendicular to the substrate, and the irradiation means is disposed around each of the optical fibers to guide light from the light source. The robot hand includes a plurality of optical fibers that irradiate light substantially perpendicularly to the thin film formed on the substrate, and the robot hand supports the substrate at a distance of 10 mm to 100 mm between the irradiation means and the substrate.
  For this reason, even if the substrate is tilted, any reflected light of the light irradiated from the plurality of optical fibers to the axis target is received by one optical fiber located at the center of the plurality of optical fibers. . For this reason, the film thickness of the thin film can be measured without being affected by the tilt of the substrate.
  Preferably, the thin film includes a transparent conductive film, and the substrate is coated with a reflective film having an area that is greater than 0% and less than or equal to 50% of the area of the film thickness measurement target region. The film thickness of the transparent conductive film is calculated ignoring reflection.
  Even if a thin film with an approximate refractive index is present in the lower layer of the thin film whose thickness is to be measured, the reflective film is provided under the thin film to be measured to be affected by the thin film with an approximate refractive index. In addition, the thin film can be measured accurately.
  In addition, when the inventor of the present invention performs film thickness measurement on the assumption that the lower layer of the target layer is a transparent substrate made of a glass substrate or the like, the film thickness of the thin film can be accurately measured. It was confirmed experimentally that it was possible.
  Preferably, the thin film includes a transparent conductive film, and the substrate is coated with a reflective film having an area that is greater than 50% and less than or equal to 100% of the area of the film thickness measurement target region. The film thickness of the transparent conductive film is calculated ignoring the effect of light transmission.
  The inventor of the present invention is that the target layer is a transparent conductive film such as an ITO layer, and when a Ta reflective film is formed under the ITO layer, a uniform reflective film is formed under the ITO layer. It was experimentally confirmed that the film thickness measurement of the thin film can be performed accurately when the film thickness measurement is performed assuming that there is.
  GoodPreferably, the reflective film is a metal film or alloy film containing tantalum, titanium, aluminum, chromium, or molybdenum as a main component.
  These materials are materials generally used for semiconductor devices and liquid crystal display devices. For this reason, by using it as a reflective film below the target thin film, a material or a process for newly forming the reflective film becomes unnecessary.
[0043]
  Preferably,The irradiating means is disposed at a position where light is irradiated substantially perpendicularly to the substrate, and the light receiving means is disposed at a position where light reflected substantially perpendicularly to the substrate is received.
[0044]
  By providing the irradiating means and the light receiving means substantially perpendicularly to the substrate, the irradiating means and the light receiving means can be integrated into an empty space of an existing line. Further, since the incident angle of light is almost a right angle, the optical path shift of the reflected light is reduced. For this reason, the film thickness of the thin film can be measured without being affected by the vibration and inclination of the substrate, the distance between the substrate and the irradiation means and the light receiving means, and the like.
  Preferably, the irradiating means includes an optical fiber that guides light from the light source and irradiates the thin film formed on the substrate, and the light receiving means receives the reflected light from the substrate and splits the received reflected light. Including an optical fiber leading to the means.
  The irradiating means and the light receiving means can be constituted only by the optical fiber. For this reason, the film thickness measuring apparatus of a thin film can be reduced in size, and even if it is existing or new, it can be easily incorporated using the empty space of a line.
[0045]
  Preferably,The irradiating means includes one optical fiber, and the light receiving means includes a plurality of optical fibers that are respectively disposed around the optical fiber and receive reflected light from the substrate.
[0046]
Even if the substrate is tilted, light is irradiated to the axis target, and the reflected light is received by one of the plurality of optical fibers. For this reason, the film thickness of the thin film can be measured without being affected by the tilt of the substrate.
[0047]
  PreferablyThe light receiving means includes one optical fiber disposed at a position for receiving light reflected substantially perpendicular to the substrate, and the irradiating means is respectively disposed around the optical fiber and guides light from the light source. And a plurality of optical fibers that respectively irradiate light substantially perpendicularly to the thin film formed on the substrate.
[0048]
Even if the substrate is tilted, any reflected light of the light irradiated from the plurality of optical fibers to the axis target is received by one optical fiber positioned at the center of the plurality of optical fibers. For this reason, the film thickness of the thin film can be measured without being affected by the tilt of the substrate.
[0049]
  PreferablyOne optical fiber and a plurality of optical fibers are cylindrical optical fibers having the same diameter, and the plurality of optical fibers includes six optical fibers.
[0050]
All optical fibers have a cylindrical structure. Therefore, the optical fiber coating can be easily peeled off simply by applying pressure from the outside. Moreover, the irradiation means and the light receiving means can be assembled by simply arranging six optical fibers around one optical fiber. For this reason, the optimal optical fiber positioning can be easily performed.
[0051]
  PreferablyThe calculating means calculates the refractive index of the substrate n₀, The refractive index of the thin film n₁, The refractive index of air is n₂, Where λ is the wavelength of light, k is the absorption coefficient of the thin film, and R is the reflection intensity of the light at the wavelength λ of the light, the equations (2) to ( The film thickness d of the thin film is calculated according to 7).
[0052]
[Expression 4]

[0053]
Expression (2) is an expression considering the absorption coefficient k of the thin film. Therefore, the film thickness can be measured with high accuracy and in a short time without limiting the wavelength range of the light source, such as being able to measure the film thickness of the thin film even in the wavelength range where light is absorbed. Therefore, the film thickness of the thin film can be measured without dropping the line tact and can be used in-line.
[0054]
  PreferablyThe calculating means calculates the refractive index of the substrate n₀When the refractive index of the p-th layer thin film from the substrate is n (p), the refractive index of air is n (p + 1), the wavelength of light is λ, and the absorption coefficient of the p-th layer thin film is k (p), Based on the intensity of the reflected light dispersed by the means, the film thickness d (p) of the p-th thin film is calculated by Expressions (8) to (12).
[0055]
[Equation 5]

[0056]
  Expression (8) is an expression considering the absorption coefficient k (p) of the thin film of each layer. Therefore, the film thickness can be measured with high accuracy and in a short time without limiting the wavelength range of the light source, such as being able to measure the film thickness of a thin film made of a multilayer film even in the wavelength range where light is absorbed. For this reason, it is possible to measure the film thickness of the thin film without reducing the tact of the line, and it is possible to use it in-line.
  Preferably, the light source includes a plurality of lamps provided in the same casing and having different wavelength ranges.
By providing multiple lamps in the same housing, it is easier to switch the light to be radiated to the substrate and to simplify the structure of the irradiating means that guides the light from the light source compared to the case where each lamp is installed in an individual housing. Can do. For this reason, the thin film thickness measuring apparatus can be reduced in size.
  Preferably, the light source includes a plurality of lamps provided in different housings and having different wavelength ranges.
  Preferably, the plurality of lamps includes a deuterium lamp and a halogen lamp.
  Preferably, the plurality of lamps can be lit independently.
  By lighting each of the plurality of lamps independently, it is possible to change the combination of lamp lighting and to irradiate the thin film with light having various wavelength ranges. Therefore, the film thickness of the thin film can be appropriately measured by selecting light in an appropriate wavelength region according to the material of the thin film.
[0065]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
FIG. 1 is a diagram for explaining a schematic configuration of a thin film thickness measuring apparatus according to Embodiment 1 of the present invention. This thin film thickness measuring apparatus is a light source 1 and branched light that guides light from the light source 1 to a plurality of locations (here, two locations) on the substrate 3 and receives reflected light from the substrate 3 at each location. The reflected light guided by the optical fiber 2, the incident light guided to a plurality of locations on the substrate 3, and the light limiting shutter 4 that selectively blocks the plurality of reflected light on the substrate 3, and the branched optical fiber 2 for each wavelength. It includes a spectroscope 5 that decomposes into light intensity and a calculator 6 that analyzes the light intensity for each wavelength and calculates the film thickness of the thin film.
[0066]
For the light source 1, for example, only a halogen lamp having a wavelength region (400 to 850 nm) close to the visible light wavelength region (400 to 800 nm) is used. However, another lamp may be provided in the same light source room as that of the halogen lamp or in another light source room, and the lamps may be turned on at the same time or may be switched on and used. In addition, as the optical component such as the spectroscope 5, a component capable of covering the wavelength range is used.
[0067]
FIG. 2 is a diagram for explaining a schematic configuration of the branched optical fiber 2. The branched optical fiber 2 includes an optical fiber 2a that guides light from the light source 1 onto the substrate 3, a light from the light source 1 that leads to the measurement point (1) on the substrate 3, and a measurement point (1) on the substrate 3. The optical fiber 2b for guiding the reflected light from ▼ to the spectroscope 5 and the light from the light source 1 are guided to the measuring point (2) on the substrate 3, and the reflected light from the measuring point (2) on the substrate 3 is spectroscope. And an optical fiber 2d for guiding the reflected light from the measurement point (1) on the substrate 3 and the reflected light from the measurement point (2) to the spectrometer 5.
[0068]
FIG. 3 is a diagram for explaining the branched optical fiber 2 in more detail. The optical fiber 2a includes two groups of optical fibers 2aa and 2ab. The optical fiber 2aa guides the light from the light source 1 to the measurement point (1) on the substrate 3. The optical fiber 2ab guides the light from the light source 1 to the measurement point (2) on the substrate 3.
[0069]
The optical fiber 2b includes two groups of optical fibers 2ba and 2bb. The optical fiber 2ba guides the light from the light source 1 to the measurement point (1) on the substrate 3. The optical fiber 2bb guides the reflected light from the measurement point (1) on the substrate 3 to the spectroscope 5.
[0070]
The optical fiber 2c includes two groups of optical fibers 2ca and 2cb. The optical fiber 2ca guides the light from the light source 1 to the measurement point (2) on the substrate 3. The optical fiber 2 cb guides the reflected light from the measurement point (2) on the substrate 3 to the spectrometer 5.
[0071]
The optical fiber 2d includes two groups of optical fibers 2da and 2db. The optical fiber 2da guides the reflected light from the measurement point (1) on the substrate 3 to the spectroscope 5. The optical fiber 2db guides the reflected light from the measurement point (2) on the substrate 3 to the spectroscope 5.
[0072]
FIG. 4 is a diagram for explaining a schematic configuration of the light limiting shutter 4. The light limiting shutter 4 is provided in the middle of each of the optical fibers 2b and 2c shown in FIG. That is, it is provided between the connection point (connection point between the optical fibers 2d and 2b) 2x between the optical fibers 2a and 2c and the measurement points (1) and (2). The light limiting shutter 4b provided in the middle of the optical fiber 2b controls switching between passing and blocking of incident light to the measurement point {circle around (1)} on the substrate 3 and reflected light from the measurement point {circle around (1)} by opening and closing thereof. . The light limiting shutter 4c provided in the middle of the optical fiber 2c controls switching between passing and blocking of incident light to the measurement point (2) on the substrate 3 and reflected light from the measurement point (2) by opening and closing. . By closing one of the light limiting shutters 4b and 4c and opening the other, only one of the reflected light from the measurement points (1) and (2) on the substrate 3 can be selected and guided to the spectroscope 5. is there. Further, by simultaneously opening the light limiting shutters 4b and 4c, it is possible to measure the average value of the film thickness at the measurement points (1) and (2) on the substrate 3.
[0073]
FIG. 5 is a flowchart for explaining the processing procedure of the film thickness measurement processing executed by the computer 6. First, the spectroscope 5 decomposes the reflected light from the substrate 3 into light intensity (spectrum) for each wavelength (S1). The calculator 6 acquires spectral data for each wavelength from the spectroscope 5 (S2), and calculates the thickness of the thin film using a theoretical formula described later (S3). The calculator 6 displays the obtained film thickness on the screen of the calculator 6 and accumulates and stores the data (S4). The computer 6 transfers the accumulated data to a central controller (not shown) (S5).
[0074]
The centralized controller that has received the data on the film thickness of the thin film from the computer 6 is used when the film thickness of the thin film exceeds a predetermined reference value or when the difference in film thickness between measurement points in the substrate is large. When the change in the film thickness over time at a certain measurement point is large, a process for occurrence of an abnormality such as an alarm is performed.
[0075]
Here, an example of the thin film thickness analysis method will be described. Let n be the refractive index of the substrate₀, The refractive index of the thin film n₁, The refractive index of air is n₂When the absorption coefficient of the thin film is k, the film thickness of the thin film is d, and the wavelength of the light source is λ, the reflected light intensity R from the substrate can be expressed by equations (2) to (7).
[0076]
The optical constants n and k are values that change depending on the wavelength λ of light. By performing a plurality of predetermined representative wavelengths or wavelength sampling (for example, by sampling in steps of 5 nm from 400 nm to 850 nm), the optical constants n and k are changed, and for each wavelength λ, the equation (2 ) To (7), the upper and lower limit values are set in advance according to the assumed film thickness, and the film thickness d of the thin film is determined within the range of the upper and lower limit values. The film thickness d of the thin film is obtained by averaging the film thickness d of the thin film at all wavelengths.
[0077]
When the optical constants n and k are not known, the optical constants n and k and the film thickness d of the thin film can be obtained as follows (1) to (3).
(1) Thin film thickness d and thin film refractive index n whose values are to be obtained₁For the absorption coefficient k of the thin film, rough values (for example, assumed film thickness, refractive index and absorption coefficient at the representative wavelength, etc.) are substituted into Equation (2) as initial values.
(2) Next, each parameter d, n₁, K are set. For example, if the film thickness is d, a value of ± 50% of the assumed film thickness is set as the upper limit value and the lower limit value.
(3) Parameters d and n₁, K are changed within the range of the upper limit value and the lower limit value, and are substituted into Equation (2), and the value of each parameter is calculated so that the resulting curve is closest to the actually measured wavelength-light intensity curve To do. More specifically, the difference between the light intensities of the two curves is obtained for each wavelength, and each parameter can be obtained by changing the parameter so that the sum of the squares of the differences in the measurement wavelength region is minimized. . By this method, the optical constants n and k and the film thickness d of the thin film can be obtained simultaneously.
[0078]
Also, when a multilayer thin film is formed on the substrate, the film thickness of each layer can be calculated in the same manner as described above. Here, the refractive index of the substrate is n (0), the refractive index of the thin film of the p-th layer from the substrate is n (p), the refractive index of air is n (p + 1), and the absorption coefficient of the thin film of the p-th layer from the substrate is When k (p), the thickness of the thin film in the p-th layer from the substrate is d (p), and the wavelength of the light source is λ, the reflected light intensity R (p + 1, 0) from the substrate and these parameters are The relationships represented by equations (8) to (12) are established.
[0079]
By sequentially substituting values into the theoretical formula from the substrate to the first thin film, the second thin film, and so on, that is, by sequentially substituting 1, 2,. The optical constants (n (p), k (p)) and film thickness d (p) of the thin film can be obtained. However, when thin films having similar optical constants are laminated adjacent to each other, the analysis is performed with these thin films as the same layer. Since the number of parameters increases as the number of thin films increases, the time required for the calculation also increases. Also, the error from the actual value increases as the number of thin films increases. However, according to the study of the present inventor, it was confirmed that in a liquid crystal display device, even about three layers can be measured in-line.
[0080]
The number of measurement points on the substrate may be one in order to predict an abnormality of the liquid crystal display device. However, in a substrate for a liquid crystal display device having a size of 1 m square or more, the thickness of the thin film may be partially different. Many local abnormalities of film thickness occur rarely. For this reason, it is desirable to measure about 3 to 5 points on one substrate.
[0081]
FIG. 6A is a side view showing an example of installation of the thin film thickness measuring apparatus in the present embodiment, and FIG. 6B is a plan view thereof. As shown in FIG. 6A, the sensor unit 10 in which the branched optical fiber 2 shown in FIG. 1 is provided is fixed to a column 10a provided in the film forming apparatus. The branched optical fiber 2 is drawn around inside the column 10a. The sensor unit 10 is attached so as to irradiate light substantially perpendicularly to the substrate 3 located in the vicinity of the gate opening (hereinafter referred to as “gate valve”) 13 of the film forming apparatus. The distance between the substrates 3 is required to be 10 mm or more so that the substrate 3 does not come into contact with the sensor unit 10 during the movement or maintenance of the substrate 3. However, in order to maintain the measurement accuracy, the distance is about 100 mm to several tens of mm or less. It is preferable.
[0082]
This film forming apparatus is, for example, a CVD (Chemical Vapor Deposition) apparatus, which forms a film in units of a plurality of sheets, and stores the plurality of formed films in a tray. The plurality of substrates are stored in a load lock 14 provided in the gate valve 13 of the unload chamber shown in FIG. The substrate transport robot 11 takes out the substrates one by one from the load lock 14 and places them on the robot hand 12 so that the substrate 3 is positioned directly below the sensor unit 10. When there are a plurality of measurement points on one substrate, the robot 11 sequentially turns the substrate 3 on the substrate 3 so that the next measurement point is directly below the sensor unit 10 every time measurement of a certain measurement point is completed. Repeat the move. Each time the substrate 3 moves, the sensor unit 10 measures the film thickness at each measurement point. FIG. 6C shows the shape of the robot hand 12. In many cases, the substrate 3 is generally supported by a U-shape, and as the substrate 3 moves away from the point at which the substrate 3 is supported, the substrate 3 hangs down due to its own weight. For this reason, the relative position of the substrate 3 is shifted by several millimeters or is slightly inclined. Therefore, it is necessary for the film thickness measuring device to maintain measurement accuracy with respect to such deviation and inclination.
[0083]
Next, details of the structure of the sensor unit 10 will be described. At the tip of the sensor unit 10, the above-described optical fiber 2b and optical fiber 2c described with reference to FIGS. 2 and 3 are provided.
[0084]
The optical fiber 2b includes the optical fibers 2ba and 2bb as described above. As shown in FIG. 7, the optical fiber 2ba includes six optical fibers and is arranged around the optical fiber 2bb. The optical fiber 2bb and the six optical fibers 2ba have the same diameter. With such a structure, referring to FIG. 8, by arranging six optical fibers 2ba around the optical fiber 2bb and fixing them with a jig, the optical fibers 2bb and 2ba can be connected to each other. Can be parallel. For this reason, the assembly of the optical fiber 2b becomes easy. Even if the substrate 3 is tilted at the time of measuring the film thickness, the reflected light of the light irradiated from one of the six optical fibers 2ba is received by the optical fiber 2bb. For this reason, the film thickness of the thin film can be measured without being affected by the inclination of the substrate 3.
[0085]
The optical fiber 2c is configured similarly to FIG.
FIGS. 9 to 11 are diagrams for explaining the influence of the vertical displacement, inclination, and vibration of the substrate on the measured values. On the substrate, a GI layer (silicon nitride), an i layer (amorphous silicon) and n⁺Layer (n⁺It is assumed that three layers of type amorphous silicon) are formed. FIG. 9 shows a graph in which the distance between the sensor unit 10 and the substrate 3 is plotted on the horizontal axis, and the film thickness of the thin film measured by the above-described film thickness measuring apparatus is plotted on the vertical axis. As can be seen from FIG. 9, the GI layer, i layer and n⁺Even in a multilayer structure in which layers are deposited, each layer is measured with little variation due to distance shift. As described above, the distance between the sensor unit 10 and the substrate 3 is shifted by several millimeters due to the warpage of the substrate 3, but the thickness of the thin film can be measured without being affected by this. Is possible.
[0086]
FIG. 10 shows a graph when the horizontal axis represents the inclination angle of the substrate 3 with respect to the sensor unit 10 and the vertical axis represents the film thickness measured by the above-described film thickness measuring apparatus. When the tilt angle is 3 to 4 ° or more, the received reflected light is 50% or less compared to the case where the tilt angle is 0 °, but as can be seen from FIG. 10, the GI layer, i layer, and n⁺Even in a multi-layer structure in which layers are stacked, if the inclination of the substrate 3 is 8 ° or less (more preferably, if the inclination of the substrate 3 is 2 ° or less), the film thickness of the thin film is measured with relatively high accuracy. be able to.
[0087]
FIG. 11 is a graph showing the influence of vertical vibration of the substrate 3. The intensity of the reflected light was measured every 10 seconds under conditions of an upper and lower amplitude of 4 mm and a frequency of 5 Hz. In the graph of FIG. 11, the horizontal axis represents the measurement time, and the vertical axis represents the reflection intensity of the reflected light measured by the above-described film thickness measuring apparatus. As can be seen from FIG. 11, the reflection intensity is stable even when vibration is applied.
[0088]
The above-described GI layer, i layer, and n so as to cover the reflective film made of tantalum (Ta) as shown in FIG.⁺The film thickness of each layer having a three-layer structure in which the layers were deposited was measured. At this time, the film thickness is measured on the assumption that all layers below the target layer are glass substrates. FIG. 13 shows a GI layer, an i layer, and an n layer in a portion where there is no reflective film, the inside of the display portion of the liquid crystal display device where the reflective film is about 10%, and the periphery of the display portion of the liquid crystal display device where the reflective film is about 50%.⁺The film thickness of the layer is shown. GI layer, i layer and n⁺The variations in the layers are about ± 2.5%, ± 1.3%, and ± 1.0%, respectively, and the measurement results of the film thickness of each layer are stable. This is because the influence of light refraction is reduced by applying light substantially perpendicular to the substrate 3, and the influence of changing the light reflection direction at the edge portion of the reflective film is reduced.
[0089]
In addition, as for the halogen lamp used as the light source 1 when calculating | requiring the film thickness of the above-mentioned thin film, light quantity and wavelength distribution change with time. For this reason, when obtaining the reflected light intensity R, it is preferable to periodically obtain the spectrum of the irradiation light of the light source 1 using a total reflection substrate and correct various parameters.
[0090]
As shown in FIG. 14, the optical fiber 2bb may be constituted by six optical fibers and arranged around the optical fiber 2ba having the same diameter. With such a structure, assembly of the optical fiber 2b is facilitated. Further, even if the substrate 3 is tilted during the film thickness measurement, the reflected light of the light irradiated from the optical fiber 2ba is received by one of the six optical fibers 2ba. For this reason, the film thickness of the thin film can be measured without being affected by the inclination of the substrate 3. The optical fiber 2c may have the same configuration.
[0091]
As described above, in the thin film thickness measuring apparatus according to the present embodiment, the structure of the sensor unit 10 is extremely simple. For this reason, size reduction is possible.
[0092]
Further, when analyzing the measurement of the film thickness, the analysis can be performed only with the wavelength-light intensity curve. For this reason, the film thickness of a thin film can be measured in a short time even in a multilayer film or multipoint measurement.
[0093]
In addition, since the film thickness measuring device is compact, it can be easily incorporated into the production line. Furthermore, since the film thickness can be measured in a short time, the film thickness can be measured immediately after the film formation, and the time lag from the occurrence of abnormality during manufacturing to the discovery can be shortened. Damage can be minimized.
[0094]
In addition, by accumulating and storing film thickness data and analyzing the data, it is possible to predict the lifetime of the film forming apparatus or film forming material, the appropriate maintenance time for the film forming apparatus, the time for changing the film forming conditions, etc. be able to. Therefore, sudden maintenance can be avoided, and the stable film forming apparatus can be operated.
[0095]
[Embodiment 2]
The thin film thickness measuring apparatus according to the second embodiment of the present invention is the same as the thin film thickness measuring apparatus according to the first embodiment. Therefore, the description will not be repeated. In this embodiment, a case where the thickness of an ITO film which is a transparent conductive film having a thickness of 100 nm (= 1000 mm) or less is measured will be described. An ITO film generally used in a liquid crystal display device is used as a pixel electrode. FIG. 15 shows a cross-sectional structure of a pixel portion of a transmissive liquid crystal display device. In such a structure, the characteristics of the thin ITO film are less likely to appear as the distribution of reflected light intensity. For this reason, it is difficult to measure the thickness of the ITO film by the evaluation method shown in the first embodiment.
[0096]
However, in a liquid crystal display device or the like, a reflective film such as Ta is often formed below the ITO film, for example, at a terminal portion on which a driver for driving is mounted. When there is a reflective film such as Ta in the lower layer, the distribution of reflected light intensity is stabilized, and high-precision measurement is possible at that portion. The area of the reflective film is 50% or more with respect to the total area.
[0097]
FIG. 16 shows the result of measuring the thickness of the ITO film using the light source 1 composed of the same halogen lamp (wavelength range of about 400 nm to about 850 nm) as in the first embodiment. The horizontal axis represents the set film thickness under production conditions, and the vertical axis represents the measurement result with the film thickness measuring device. When the thickness of the thin film is 60 nm (= 600 mm), the measured value of the thickness is stable. When the thickness of the ITO film is other than 60 nm, the variation in the measured value is large. For this reason, it becomes difficult to detect a film thickness abnormality.
[0098]
For this reason, a halogen lamp and a deuterium lamp were used as the light source 1, and the film thickness of the ITO film was measured in a state where the lamps were placed in the same light source chamber and were turned on simultaneously (wavelength range of about 220 nm to about 850 nm). As a result, a graph as shown in FIG. 17 was obtained. As can be seen from this graph, the variation in the measured value is small in any film thickness, and the correlation between the set film thickness and the measured value in the production conditions is high. However, there is a slight difference between the set film thickness and the measured value. This is due to the fact that the absorption coefficient k (p) is constant for each wavelength in order to increase the calculation speed (it is assumed that there is a uniform reflective film below the ITO layer). For this reason, if the relationship between the set film thickness and the measured value is known in advance, the film thickness can be accurately measured by correcting the measured value. However, when a film thickness measuring apparatus is used in-line to detect a film thickness abnormality, it is only necessary to know the temporal change in the film thickness at the measurement point. In such a case, correction of the measurement value is not necessary.
[0099]
As described above, in the film thickness measurement apparatus according to the present embodiment, the film for light in the wavelength range of about 220 nm to about 850 nm is used by using the light source 1 in which the halogen lamp and the deuterium lamp are simultaneously turned on. A thickness measurement is performed. In general, in order to measure a thin film, the film thickness must be measured using light having a short wavelength. Therefore, by simultaneously lighting the deuterium lamp, it is possible to accurately measure the thickness of the ITO film as compared with the case where only the halogen lamp is used.
[0100]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a schematic configuration of a thin film thickness measuring apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a schematic configuration of a branched optical fiber 2;
FIG. 3 is a diagram for explaining the branched optical fiber 2 in more detail.
FIG. 4 is a diagram for explaining a schematic configuration of a light limiting shutter.
FIG. 5 is a flowchart for explaining a processing procedure of the thin film thickness measuring apparatus according to the first embodiment of the present invention.
FIG. 6 is a diagram showing an example of installation of a thin film thickness measuring apparatus according to Embodiment 1 of the present invention.
FIG. 7 is a diagram showing a configuration of an optical fiber 2b.
FIG. 8 is a diagram showing a configuration of an optical fiber 2b.
FIG. 9 is a graph showing the film thickness measurement result when the distance between the sensor unit and the substrate is changed.
FIG. 10 is a graph showing a measurement result of a thin film thickness when the tilt angle of the substrate with respect to the sensor unit is changed.
FIG. 11 is a graph showing a temporal change in intensity of reflected light incident on a sensor unit when vertical vibration is applied to a substrate.
FIG. 12 shows a GI layer, an i layer, and an n layer so as to cover a reflective film made of Ta.⁺It is a figure which shows the 3 layer structure in which the layer was deposited.
FIG. 13 is a graph showing the measurement results of the thickness of the thin film when the area ratio of the reflective film is changed.
FIG. 14 is a diagram showing a configuration of an optical fiber 2b.
FIG. 15 is a diagram showing a cross-sectional structure of a pixel portion of a transmissive liquid crystal display device.
FIG. 16 is a graph showing the results of measuring the thickness of an ITO film when a halogen lamp is used as a light source.
FIG. 17 is a graph showing the measurement results of the thickness of an ITO film when a halogen lamp and a deuterium lamp are used as a light source.
FIG. 18 is a diagram for explaining a method of measuring a film thickness using a conventional ellipsometer.
FIG. 19 is a diagram showing an example of a substrate on which film thickness cannot be measured.
FIG. 20 is a diagram for explaining an example of a conventional optical interference method.
FIG. 21 is a diagram showing an example of the relationship between the wavelength of reflected light and the light intensity.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light source, 2 branch type optical fiber, 2a, 2b, 2c, 2d, 2aa, 2ab, 2ba, 2bb, 2ca, 2cb, 2da, 2db Optical fiber, 3,106 substrate, 4, 4b, 4c Optical limiting shutter, 5 Spectroscope, 6 computer, 10 sensor unit, 10a support, 11 robot, 12 robot hand, 13 gate valve, 14 load lock, 101 polarizer, 102 analyzer, 103 thin film forming substrate, 104 thin film layer, 105 wiring pattern.

Claims (12)

A light source having a wavelength range of at least about 220 nm to 850 nm;
A robot hand for supporting the substrate locally;
The substrate hangs down with a displacement of several millimeters by being supported by the robot hand, and has a portion whose inclination angle is 8 degrees or less,
Irradiating means for guiding light from the light source and irradiating light substantially perpendicularly to a thin film formed on the substrate;
A light receiving means for receiving reflected light from the thin film or the substrate;
Spectroscopic means for spectrally separating the reflected light received by the light receiving means for each wavelength;
Calculation means for calculating the film thickness of the thin film based on the intensity of the reflected light in a wavelength range of about 220 nm to 850 nm spectrally separated by the spectroscopic means,
The irradiating means includes one optical fiber,
The light receiving means includes a plurality of optical fibers that are respectively disposed around the optical fiber and receive reflected light from the substrate,
The robot hand is a thin film thickness measuring device that supports the substrate at a distance of 10 mm to 100 mm between the irradiation means and the substrate. A light source having a wavelength range of at least about 220 nm to 850 nm;
A robot hand for supporting the substrate locally;
The substrate hangs down with a displacement of several millimeters by being supported by the robot hand, and has a portion whose inclination angle is 8 degrees or less,
Irradiating means for guiding light from the light source and irradiating light substantially perpendicularly to a thin film formed on the substrate;
A light receiving means for receiving reflected light from the thin film or the substrate;
Spectroscopic means for spectrally separating the reflected light received by the light receiving means for each wavelength;
Calculation means for calculating the film thickness of the thin film based on the intensity of the reflected light in a wavelength range of about 220 nm to 850 nm spectrally separated by the spectroscopic means,
The light receiving means includes one optical fiber arranged at a position for receiving light reflected substantially perpendicular to the substrate,
The irradiating means includes a plurality of optical fibers disposed around the optical fiber, respectively, for guiding light from the light source and irradiating light substantially perpendicularly to a thin film formed on the substrate,
The robot hand is a thin film thickness measuring device that supports the substrate at a distance of 10 mm to 100 mm between the irradiation means and the substrate. The thin film includes a transparent conductive film,
The substrate is coated with a reflective film having an area that is greater than 0% and less than or equal to 50% of the area of the film thickness measurement target area.
The thin film thickness measuring apparatus according to claim 1, wherein the calculating unit calculates the film thickness of the transparent conductive film ignoring reflection on the reflective film. The thin film includes a transparent conductive film,
The substrate is coated with a reflective film having an area greater than 50% and less than or equal to 100% of the area of the film thickness measurement target area,
3. The thin film thickness measuring apparatus according to claim 1, wherein the calculating means calculates the film thickness of the transparent conductive film ignoring the influence of light transmission on the lower layer thin film. The reflective film is tantalum, titanium, aluminum, a metal film or an alloy film mainly composed of chromium or molybdenum, the film thickness measuring device of the thin film according to claim 3 or 4. The one optical fiber and the plurality of optical fibers are cylindrical optical fibers having the same diameter,
The thin film thickness measuring apparatus according to claim 1, wherein the plurality of optical fibers includes six optical fibers. The calculating means has a refractive index of the substrate n ₀ , a refractive index of the thin film n ₁ , a refractive index of air n ₂ , a wavelength of light λ, an absorption coefficient k of the thin film, and a wavelength of the light. When the reflection intensity of light at λ and R, based on the intensity of the spectrally separated the reflected light by the spectroscopic means, and calculates the thickness d of the thin film by the following equation, according to any one of claims 1 to 6 Thin film thickness measuring device.

The calculating means has a refractive index of the substrate n ₀ , a refractive index of the p-th thin film from the substrate n (p), an air refractive index n (p + 1), a light wavelength λ, and the p layer When the absorption coefficient of the thin film of the eye is k (p), the film thickness d (p) of the thin film of the p-th layer is calculated by the following formula based on the intensity of the reflected light dispersed by the spectroscopic means. The thin film thickness measuring apparatus according to any one of claims 1 to 7 .

The light source, the same case provided in the body, including a plurality of different lamps wavelength ranges, the film thickness measuring device of the thin film according to any one of claims 1-8. The light source provided on different housing each include a plurality of different lamps wavelength ranges, the film thickness measuring device of the thin film according to any one of claims 1-9. The thin film thickness measuring apparatus according to claim 9 or 10 , wherein the plurality of lamps include a deuterium lamp and a halogen lamp. Wherein the plurality of lamps can be lit independently, the film thickness measuring device of the thin film according to any one of claims 9-11.

Images