JP3632832B2 - Sheet resistance measurement method - Google Patents

Description

【００６４】
とみなすことができ、上記共振回路の共振条件は、式（１）において虚部＝０だから、上記インピーダンスＺは、
【００６５】
【数２】

【００６６】
となる。
【００６７】
上記式（２）で表されるインピーダンスＺは、Ｒ_２ ≠０、すなわち、金属薄膜１１ａをコイル１２ａに近づけた状態での共振回路のインピーダンス（以下、Ｚ_１ と称する）である。また、金属薄膜１１ａをコイル１２ａに近づけない状態での共振回路のインピーダンス（以下、Ｚ_０ と称する）は、式（２）においてＲ_２ ＝０を代入すればよく、
Ｚ_０ ＝Ｒ_１
となる。
【００６８】
そして、図４に示す共振回路を定電圧回路とみなせば、
Ｚ・Ｉ＝Ｅ（一定）・・・・・・（３）
の関係を満足するからすなわち、上記の方法は共振回路全体のインピーダンスＺの変化を直列回路の抵抗値の変化（抵抗Ｒｕが並列に付加された）としてとらえる方法である。
【００６９】
上記共振回路内では、式（３）に示すように、回路を流れる電流Ｉと、回路全体のインピーダンスＺとは反比例の関係にあるので、金属薄膜１１ａが近づくことにより生じたインピーダンスの変化量（ΔＺ＝Ｚ_０ −Ｚ_１ ）と上記電流の変化量（ΔＩ＝ΔＩ_０ −ΔＩ_１ ）とは反比例の関係にあることが判る。すなわち、共振回路を流れる電流の変化量ΔＩは、該共振回路のインピーダンスの変化量ΔＺとしてとらえることができる。
【００７０】
より具体的に説明すると、金属薄膜１１ａのシート抵抗測定時には、まず、金属薄膜１１ａをコイル１２ａに近づけない状態で、抵抗Ｒ_１ に流れる電流Ｉ_０ を測定し、続いて、金属薄膜１１ａをコイル１２ａに一定の測定高をおいて近づけた状態で、抵抗Ｒ_１ に流れる電流Ｉ_１ を測定する。これにより、金属薄膜１１ａが近づくことにより生じた電流の変化量ΔＩを、インピーダンスの変化量ΔＺとみなして取得することができる。なお、図４に示すＯＰアンプ検流計２３は、金属薄膜１１ａを近づける前後の電流の変化量（ΔＩ＝Ｉ_０ −Ｉ_１ ）を直接的に検出する。
【００７１】
図４に示すように、金属薄膜１１ａを近づけることにより生じる磁界の変化量は、上記共振回路（より具体的には、抵抗Ｒ_１ ）に流れる電流の変化量を生の渦電流損失分の高周波交流電流ととらえて、直接測定されることがより好ましい。しかしながら、該電流の変化が微弱な場合には、ＯＰアンプ検流計２３に代えて、抵抗Ｒ_１ に並列に電圧計を設けてもよい。
【００７２】
例えば、ＩＴＯ等の高抵抗の金属薄膜のシート抵抗を測定する場合には、抵抗Ｒ_１ に流れる電流の変化量が極めて微弱となり、一般的な電流計では正確な測定が不可能な場合がある。この場合、共振している閉路回路（上記共振回路）に流れる電流の変化量ΔＩを検出用の上記抵抗Ｒ_１ （本実施の形態では１ｋΩ）により増幅し、電圧の変化量ΔＶとして電圧計により取得すればよい。なお、ΔＶからΔＩを取得する必要がある場合には、ΔＶ＝Ｒ_１ ・ΔＩの関係を利用して算出すればよい。
【００７３】
金属薄膜１１ａのシート抵抗値は、取得された上記ΔＶまたはΔＩと、該シート抵抗値との相関関係を利用して算出される。例えば、図２に示した高周波発振回路１３ａと、検波回路１３ｂとを備えてなるアンプ１３により、図２中（Ａ）にて示す同一発振周波数ｆ_１１での電圧の変化量ΔＶを取得し、図１に示す制御装置１６において該ΔＶに基づき金属薄膜１１ａのシート抵抗値を算出した実例を以下に示す。
【００７４】
図５に示すグラフは、金属薄膜１１ａとして複数のゲート膜（ＴｉＮ／Ａｌ／Ｔｉの積層膜：各層の基準層厚は、順に、１５００Å、３０００Å、３００Å）のシート抵抗値を測定した結果を示すものである。より具体的には、４探針シート抵抗測定方法で測定して得られたシート抵抗値（グラフのｘ軸に示す４探針値）と、同じゲート膜を本発明の方法により測定して得られた上記電圧の変化量ΔＶ（同一のゲート膜に対し複数回測定を行った平均値：グラフのｙ軸に示す検出電圧ΔＶに相当）との関係から、該ゲート膜のシート抵抗値を算出した結果を示すものである。
【００７５】
制御手段１６（図１参照）は、電圧の変化量ΔＶと４探針法によるシート抵抗値との相関を、曲線近似、より具体的には対数近似して算出する。グラフ中、黒塗りの四角形で示されるのは、各４探針値に対応したゲート膜のΔＶの値であり、実線で示されるのは、両者の相関を表す対数近似曲線である。該グラフから明らかなように、各４探針値に対応したゲート膜のΔＶの値は、一つの対数近似曲線、
ｙ＝−０．５２７１Ｌｎ（ｘ）−０．２９１７
上にほぼのっていることがわかる。すなわち、本発明の方法にてΔＶを測定すれば、上記対数近似曲線のｙにこの値を代入し、シート抵抗値（４探針値）ｘを算出することができる。
【００７６】
図５に示すグラフには、本発明にかかる方法により測定されたシート抵抗値の測定誤差、すなわち、４探針値ｘを示すゲート膜に対し取得される、上記ΔＶと上記対数近似曲線上のｙ値との誤差、
〔ΔＶ−（ｙ値）〕／（ｙ値）×１００（％）
も白抜き四角形で示している。本願発明の方法によれば、測定誤差を±２．３％以内に抑えることができ、ゲート膜のシート抵抗の全数検査管理が可能となった。
【００７７】
一方、渦電流損に相当する抵抗が、直列共振回路に直列的に付加（接続）されたとみなすとは、図６に示すように、自己インダクタンスＬ１で内部抵抗ｒ１のコイル２２ａ、直列共振用のコンデンサＣ_１１、並びに、交流電源５１が直列に接続された構成の直列共振回路（Ｌ，Ｃ，Ｒ直列回路）に、渦電流損に相当する抵抗Ｒｕが直列に接続される状態を指す。より具体的には、抵抗Ｒｕがコイル２２ａに直列に接続される状態を指す。以下、図１に示したシート抵抗測定器の等価回路として図７に示す共振回路を用い、電流または電圧の検出法などにつき、さらに詳細に説明を行う。
【００７８】
上記の共振回路は、図７に示すように、コイル１２ａ、直列共振用のコンデンサＣ_１１、抵抗Ｒ_１ （便宜上、この抵抗値もＲ_１ で表す）、並びに、交流電源１４が直列に接続された構成の直列共振回路である。また、コイル１２ａは、自己インダクタンスＬと内部抵抗ｒとが直列に接続され、これにコイル浮遊容量Ｃ_１０が並列に接続されるとみなされる。さらに上記共振回路には、抵抗Ｒ_１ に流れる電流の変化量ΔＩを直接検出するＯＰアンプ検流計（電流計）２３が直列に接続されている。また、金属薄膜１１ａがコイル１２ａに近づいたときには、直列の共振回路、より具体的にはコイル１２ａに直列に渦電流損に相当する抵抗Ｒｕが接続されると考える。また、以下に数式を用いて説明するが、図７に示す共振回路は、コイル１２ａの磁界の変化量を、共振回路全体のインピーダンスの変化量としてとらえた抵抗変換法を説明する等価回路であり、上記共振回路に並列的に抵抗Ｒｕが付加されると考える（図４参照）より、単純化される。
【００７９】
すなわち、交流の角周波数をω、コンデンサＣ_１１の静電容量をＣ、ＯＰアンプ検流計２３の内部抵抗を０、上記抵抗Ｒｕの抵抗値をＲ_２ として、図７に示す回路全体のインピーダンスＺを求めると、
【００８０】
【数３】

【００８１】
となり、上記共振回路の共振条件は、式（４）において虚部＝０だから、共振回路のインピーダンスＺは、
Ｚ＝Ｒ_１ ＋Ｒ_２ ・・・・・・（５）
となる。
【００８２】
上記式（５）で表されるインピーダンスＺは、Ｒ_２ ≠０、すなわち、金属薄膜１１ａをコイル１２ａに近づけた状態でのインピーダンス（以下、Ｚ_１ と称する）である。また、金属薄膜１１ａをコイル１２ａに近づけない状態でのインピーダンス（以下、Ｚ_０ と称する）は、式（５）においてＲ_２ ＝０を代入すればよく、
Ｚ_０ ＝Ｒ_１
となる。
【００８３】
そして、図７に示す共振回路を定電圧回路とみなせば、
Ｚ・Ｉ＝Ｅ（一定）・・・・・・（６）
の関係を満足するからすなわち、上記の方法は、共振回路全体のインピーダンスの変化を直列回路の抵抗値の変化（抵抗Ｒｕが直列に付加された）としてとらえる方法である。
【００８４】
上記共振回路内では、式（６）に示すように回路を流れる電流Ｉと、回路全体のインピーダンスＺとは反比例の関係にあるので、金属薄膜１１ａが近づくことにより生じたインピーダンスの変化量（ΔＺ＝Ｚ_０ −Ｚ_１ ）と上記電流の変化量（ΔＩ＝ΔＩ_０ −ΔＩ_１ ）とは反比例の関係にあることが判る。すなわち、共振回路を流れる電流の変化量ΔＩは、該共振回路のインピーダンスの変化量ΔＺとしてとらえることができる。なお、上記共振回路を流れる電流の変化量ΔＩや、電圧の変化量ΔＶを取得する方法、並びに、４探針値との相関方法などに関しては、上記抵抗Ｒｕが共振回路に並列に接続されるとみなす場合と同様であり、説明を省略する。
【００８５】
（インダクタンス変換法）
また、本願発明にかかるシート抵抗測定方法の他の例として、渦電流損に相当する抵抗が、コイル部を含んでなる等価回路である直列共振回路に直列的、または並列的に付加されるとみなし、該コイル部における磁界の変化量をインダクタンスの変化量とみなして取得する方法（インダクタンス変換法）が挙げられる。
【００８６】
一般に、上記インダクタンス変換法とは、変位、振動、圧力などの変化量をインダクタンスの変化量に変換する方法を指す。はじめに、図８を用いて、上記インダクタンス変換法の原理について説明を行う。
【００８７】
略Ｕ字状のフェライトコア３２ｂにコイル３２ａを巻き回してなるコイル部３２のコイル端子Ａ・Ｂ間に電圧を印加すると、該コイル部３２が磁束を発生する。このとき、金属薄膜１１ａを用いて、コイル端子Ａ・Ｂ間のインダクタンスを変化させるには、一般には、金属薄膜１１ａ、または、磁束を発生しているコイル部３２を移動させて、両者の相対位置を変位させる方法が用いられる。相対位置を変位させることにより金属薄膜１１ａを貫く磁束の時間変化が生じ、電磁誘導現象による渦電流が発生する。すなわち、両者の相対位置を変位させることでコイル部３２の磁界が変化し、この変化量をコイル端子Ａ・Ｂ間のインダクタンスの変化量に変換して取得する方法である。
【００８８】
図９に示すのは、上記インダクタンス変換法が適用されたシート抵抗測定器の概略回路構成を示す説明図であり、可変式の抵抗Ｒ_１１・Ｒ_１２、インダクタンス可変式のコイルＬ_１１、センサヘッド１２（図１参照）に内蔵されたコイル１２ａ、並びに交流電源５２からなる典型的な高周波ブリッジ３３；高周波ブリッジ３３に接続された整流回路３４；整流回路３４に接続され、コイル１２ａの磁界の変化により高周波ブリッジ３３の平衡が崩されて発生する信号（電流）を、直流電流として読むマイクロアンペア計３５；より構成されている。
【００８９】
上記のシート抵抗測定器では、金属薄膜１１ａがコイル１２ａに近づくことにより、該コイル１２ａのインダクタンスが変化する。すなわち、コイル１２ａの真下に金属薄膜１１ａが位置するときと、真下に何も存在しないときとでの磁界の変化量を、コイル１２ａのインダクタンスの変化量としてとらえる。
【００９０】
そして、上記インダクタンスの変化量を、コイル１２ａのコイル端子Ａ・Ｂ間の電流（または電圧）の変化量ΔＩ（またはΔＶ）として、マイクロアンペア計３５（または、コイル１２ａに並列に接続された電圧計）で読み取る。そして、読み取られたΔＩまたはΔＶと、４探針値との相関関係から、金属薄膜１１ａのシート抵抗を算出する。
【００９１】
図９に示すシート抵抗測定器では、インダクタンス可変式のコイルＬ_１１を設け、これにより高周波ブリッジ３３の平衡を維持する（すなわち、測定前に平衡状態をつくる）べく微調整が必要だが、該高周波ブリッジ３３を使用することで、コイル１２ａをなす材料（銅など）の温度ドリフトの影響を解消することができ、安定したシート抵抗算出が可能となる。
【００９２】
また、図１０に示すのは、インダクタンス変換法が適用された他のシート抵抗測定器の概略回路構成を示す説明図であり、抵抗Ｒ_２１・Ｒ_２２、コイルＬ_１２、センサヘッド１２（図１参照）に内蔵されたコイル１２ａ、並びに交流電源５２とからなる典型的な高周波ブリッジ３３ａ；高周波ブリッジ３３ａに接続された整流回路３４；整流回路３４に接続され、コイル１２ａの磁界の変化により高周波ブリッジ３３ａの平衡が崩されて発生する信号（電流）を、直流電流として読むマイクロアンペア計３５；より構成されている。
【００９３】
上記コイルＬ_１２は、常時、基準サンプルとしての金属標準薄膜２１ａと一定の測定高を持って配されており、この状態で、シート抵抗の測定対象である金属薄膜１１ａをコイル１２ａに近づける。これにより、金属薄膜１１ａのシート抵抗値を算出することなくＮＧ判定を可能とする。すなわち、設定値どおりのインダクタンスの変化をコイル１２ａに生じさせる金属薄膜１１ａが測定に供された場合のみに高周波ブリッジ３３ａが平衡となるように、該高周波ブリッジ３３ａを駆動すれば、測定に供される各金属薄膜１１ａが所望のシート抵抗値を示すか否かを容易に判別することができる。
【００９４】
また、図１０に示すシート抵抗測定器においても、図９に示したものと同様に、コイル１２ａのコイル端子Ａ・Ｂ間の電流（または電圧）の変化量ΔＩ（またはΔＶ）をマイクロアンペア計３５（または、コイル１２ａに並列に接続された電圧計）で読み取り、４探針値との相関から金属薄膜１１ａのシート抵抗を算出してもよい。
【００９５】
図９や図１０に示した、インダクタンス変換法が適用されてなるシート抵抗測定器では、コイル１２ａの巻き数により、そのインダクタンスを大きくすることができる。そのため、シート抵抗の測定において、例えば、以下に例示する静電容量変換法ほどの高周波電力を必要とせず、数百ｋＨｚ使用程度の周波数の電力を使用可能である。
【００９６】
また、磁束を発生するコイル１２ａに金属薄膜１１ａが近づくことで生じる該磁束の微小変化が、高周波ブリッジ３３・３３ａの平衡状態を崩し出力に信号が現れる現象を利用することで、金属薄膜１１ａのシート抵抗の高精度な測定が可能となる。なお、この原理を応用したものは、例えば、ロックイン・アンプとして知られている。
【００９７】
（静電容量変換法）
また、本願発明にかかるシート抵抗測定方法のさらに他の例として、渦電流損に相当する抵抗が、コイル部を含んでなる等価回路である直列共振回路に直列的、または並列的に付加されるとみなし、該コイル部における磁界の変化量を上記直列共振回路の静電容量の変化量とみなして取得する方法（静電容量変換法）が挙げられる。
【００９８】
一般に、上記静電容量変換法とは、長さの変化や変位などの変化量を静電容量の変化量に変換して取得する方法を指し、該変化量の測定にはメガサイクル程度の高周波電力が用いられる。このような高周波電力では、上記説明の高周波ブリッジを用いる方法以外に、共振曲線上の変化を利用する静電容量変換法も用いられる。以下、図１１、図１２（ａ）・（ｂ）を用いて、上記静電容量変換法の基本原理などにつき説明を行う。
【００９９】
図１１に示すＬ，Ｃ，Ｒ直列共振回路はシート抵抗測定器の等価回路であり、交流電源５３、コイル１２ａ、並びに。コンデンサＣ_１２が直列に接続されてなる。コイル１２ａは、自己インダクタンスＬと内部抵抗ｒとが直列に接続されたコイルであり、また、コンデンサＣ_１２はその静電容量が可変式である。はじめに、コンデンサＣ_１２の静電容量を種々に変化させて該直列共振回路の共振特性を求め、印加される電圧（Ｖ）とコンデンサＣ_１２の静電容量との関係を示す共振曲線（図１２（ａ）参照）を作成する。
【０１００】
そして、上記共振曲線上で、接線の傾き（すなわち、共振曲線の変化量）が最大となる点を算出し、この点における静電容量Ｃ_０ をコンデンサＣ_１２の静電容量の初期値として、図１１に示す直列共振回路を一定の共振周波数で共振させる。この直列共振回路において、図１２（ａ）に示すΔＣ相当の静電容量の増減があれば、共振回路の電圧（Ｖ）あるいは電流は大きな変化（電圧の変化量ΔＶ）を示すので、これらを静電容量の変化量として取得することが可能となる。
【０１０１】
図１２（ａ）に示すΔＣ相当の静電容量の増加は、例えば、図１１に示す直列共振回路では、金属薄膜１１ａがコイル１２ａに近づくことで、コンデンサＣ’相当の容量が付加されるとみなされて発生する。そして、直列共振回路全体の静電容量の値の増減分を読み取り、該容量値に損失がある場合には、図１２（ｂ）に示す等価直列回路に変換して、その抵抗分（渦電流損相当の抵抗Ｒｕ）が等価回路全体の抵抗の一部として直列的に付加されたとみなし、磁界の変化量を算出する。なお、取得された磁界の変化量（容量損失相当のΔＣ）と４探針値との相関から、金属薄膜１１ａのシート抵抗が算出される点は、上記説明と同様であり記載を省略する。
【０１０２】
（周波数変換法）
また、本願発明にかかるシート抵抗測定方法のさらに他の例として、渦電流損に相当する抵抗が、コイル部を含んでなる等価回路である直列共振回路に直列的、または並列的に付加されるとみなし、該コイル部における磁界の変化量を上記直列共振回路の共振周波数の変化量とみなして取得する方法（周波数変換法）が挙げられる。以下、図１３（ａ）・（ｂ）を用いて、上記周波数変換法の基本原理などにつき説明を行う。
【０１０３】
図１３（ｂ）に示すように、自己インダクタンスＬのコイル（コイル部）１２ａ’に交流電圧を出力する駆動周波数可変式の自励式発振器（ｓｅｌｆ−ｅｘｃｉｔｅｄ ｏｓｃｉｌｌａｔｅｒ）３６を用いる。なお、自励式発振器３６に接続される直流電源は図示しない。自励式発振器３６を使用することで、金属薄膜１１ａがコイル１２ａ’に近づいた場合と、近づかない場合とでの共振周波数に変化が生じ、この差から金属薄膜１１ａのシート抵抗値を算出する。
【０１０４】
具体的には、図１３（ａ）に示すように、金属薄膜１１ａがコイル１２ａ’の磁束の影響下にないときの共振周波数をｆ_０ 、金属薄膜１１ａがコイル１２ａ’の磁束の影響下にあるとき（近づいたとき）の共振周波数ｆ_１ とし、共振周波数の変化量（Δｆ＝ｆ_０ −ｆ_１ ）をコイル１２ａ’における磁界の変化量として取得する。なお、図１３（ｂ）では、シート抵抗測定器の等価回路である直列共振回路に、渦電流損相当の抵抗Ｒｕが直列的に付加されたとみなしている。また、取得された磁界の変化量（Δｆ）と４探針値との相関から、金属薄膜１１ａのシート抵抗が算出される点は、上記説明と同様であり記載を省略する。
【０１０５】
ところで、高周波における抵抗の測定は、同調回路の直列実効抵抗および並列同調回路の共振インピーダンスの測定として行われることが多い。一般に、図１４や図１５に示すように、交流電源（発振器）５４と、Ｌ（コイルのインダクタンス），Ｃ（コンデンサＣ_１３），Ｒ（コイルの内部抵抗）直列共振回路とを疎結合にして、例えば、可変容量（コンデンサＣ_１３）、あるいは交流電源５４の周波数を変化して、直列共振回路の電流または電圧を電流計４１または電圧計４２で読むことにより、高周波における直列共振回路の実効抵抗や、並列共振インピーダンスなどを測定することができる。そして、可変容量を変化させる方法はリアクタンス変化法、また、周波数を変化させる方法は周波数変化法と一般に称されており、オフラインなど迅速性がさほど要求されないシート抵抗測定において、特に高精度な測定を実現可能とする方法である。
【０１０６】
（リアクタンス変化法）
図１４を用いてリアクタンス変化法の原理について詳細に説明する。図１４（ｂ）に示す高周波抵抗測定回路にて、容量可変式のコンデンサＣ_１３の容量を変化させて同調したときのコンデンサＣ_１３、電流計４１（または電圧計４２）の読みをそれぞれＣ_０ ，Ｉｒ（Ｅｒ）、また、離調した時のコンデンサＣ_１３、電流計４１（または電圧計４２）の読みをそれぞれＣ_１ ・Ｃ_２ ，Ｉ（Ｅ）とし、電流計の内部抵抗をＲ_Ａ 、交流電源５４の周波数をｆ（一定）とすれば、Ｌ，Ｃ，Ｒ直列共振回路の直列実効抵抗Ｒ_Ｘ は、
【０１０７】
【数４】

【０１０８】
となり、直列実効抵抗Ｒ_Ｘ を求めることができる。そして、直列実効抵抗Ｒ_Ｘ を渦電流損に相当する抵抗Ｒ_ｕ とみなして、シート抵抗算出に応用する。なお、上記直列実効抵抗Ｒ_Ｘ を求める式は、以下に示す過程により導かれる式（１３）から容易にもとめることができる。また、この場合の並列共振インピーダンスＺｒは、
【０１０９】
【数５】

【０１１０】
となる。以下、上記直列実効抵抗Ｒ_Ｘ の算出方法に関し、シート抵抗測定器の等価回路を示す図１６を参照しながらさらに詳細に説明を行う。
【０１１１】
リアクタンス変化法が適用されるシート抵抗測定器の等価回路は、例えば、図１６（ｂ）に示すように、交流電源５４、インダクタンスＬのコイル１２ａ’、内部抵抗Ｒ_Ａ の電流計４１、並びに、容量可変式のコンデンサＣ_１３が直列に接続されてなる。また、シート抵抗測定の間じゅう、金属薄膜１１ａとコイル１２ａ’とは一定の測定高を維持した状態に保たれる。すなわち、該金属薄膜１１ａがコイル１２ａ’に近づいたときに発生する渦電流損に相当する抵抗Ｒｕが、上記等価回路に直列的に付加されたとみなすことにより、シート抵抗測定時のシート抵抗測定器の等価回路を得る。なお、コイル１２ａ’の内部抵抗は０と仮定して以下の説明を行う。
【０１１２】
上記金属薄膜１１ａをコイル１２ａ’に近づけた状態のシート抵抗測定器において、コイル１２ａ’を発振させ、コンデンサＣ_１３の静電容量を調整して該コイル１２ａ’の共振特性をとると、図１６（ａ）に示すような特性グラフが得られるが、この等価回路において、電流計４１を流れる電流をＩｓ、交流電源５４の電圧をＶｏｓｃ、コンデンサＣ_１３の静電容量をＣ、該電圧の角振動数をωとすると、電流Ｉｓは、
【０１１３】
【数６】

【０１１４】
となる。
【０１１５】
そして、図１６（ａ）の特性グラフに示すように、コイル１２ａ’が共振するときのコンデンサＣ_１３の静電容量がＣ_０ 、電流計４１を流れる電流の値（Ｉｓ）がＩｒであるとし、続いて、金属薄膜１１ａとコイル１２ａ’とを近づけたままで静電容量を変化させて、静電容量Ｃ_０ の上下Ｃ_１ ，Ｃ_２ でのＩｓが共にＩ＝Ｉｒ／√２ （実効電流値）になったとすると、Ｃ_１ ，Ｃ_２ でのＩｓが等しいので、
【０１１６】
【数７】

【０１１７】
の関係が成立する。また、コイル１２ａ’の共振が得られるＣ_０ ではリアクタンス＝０とみなされる。したがって、上記式（７）から、交流電源５４の電圧Ｖｏｓｃは、
【０１１８】
【数８】

【０１１９】
と導かれる。ここで、上記式（９）から、渦電流損に相当する抵抗Ｒｕをもとめるには、該式（９）において、
【０１２０】
【数９】

【０１２１】
と置換することにより、
【０１２２】
【数１０】

【０１２３】
続いて、式（１０）において、右辺の１を左辺に移項し、両辺の平方根をとることにより、
【０１２４】
【数１１】

【０１２５】
この結果、
【０１２６】
【数１２】

【０１２７】
の関係が導かれる。さらに、式（８）より、
【０１２８】
【数１３】

【０１２９】
このωＬを式（１２）に代入し、Ｒ_Ａ を右辺に移項することで、
【０１３０】
【数１４】

【０１３１】
が得られる。
【０１３２】
【数１５】

【０１３３】
となる。すなわち、金属薄膜１１ａとコイル１２ａ’とを一定距離に近づけた状態で、コイル１２ａ’が共振する静電容量Ｃ_０ 、並びに電流Ｉが流れる静電容量Ｃ_１ ，Ｃ_２ をもとめることにより上記抵抗Ｒｕの抵抗値を算出し、該抵抗値とシート抵抗値との相関より、金属薄膜１１ａのより精密なシート抵抗値をもとめることが実現可能となる。
【０１３４】
（周波数変化法）
次に、図１５を用いて周波数変化法の原理について詳細に説明する。図１５（ｂ）に示す高周波抵抗測定回路にて、交流電源５４を含む回路に流れる一次電流（電圧）を一定としてその周波数を変化させ、同調、すなわち共振したときの周波数（共振周波数ｆ０）における、電流計４１（または電圧計４２）の読み（２次電流（２次電圧）の大きさ）をＩｒ（Ｅｒ）、離調した時の周波数（離調周波数ｆ１，ｆ２）における、電流計４１（または電圧計４２）の読みをＩ（Ｅ）とすれば、Ｌ，Ｃ，Ｒ直列共振回路の直列実効抵抗Ｒ_Ｘ は、
【０１３５】
【数１６】

【０１３６】
となり、直列実効抵抗Ｒ_Ｘ を求めることができる。そして、直列実効抵抗Ｒ_Ｘ を渦電流損に相当する抵抗Ｒ_ｕ とみなして、シート抵抗算出に応用する。なお、上記直列実効抵抗Ｒ_Ｘ を求める式（１４）は、上記説明の式（１３）から容易に導かれるので詳細な説明は省略する。以下、シート抵抗測定器の等価回路を示す図１７を参照しながら、本測定方法に付きさらに詳細に説明を行う。
【０１３７】
周波数変化法が適用されるシート抵抗測定器の等価回路は、例えば、図１７（ｂ）に示すように、周波数可変式の交流電源５４、インダクタンスＬのコイル１２ａ’、内部抵抗Ｒ_Ａ の電流計４１、並びに、コンデンサＣ_１３が直列に接続されてなる。また、交流電源５４と並列に電圧計５５が接続されている。
【０１３８】
金属薄膜１１ａとコイル１２ａ’とは、シート抵抗測定の間じゅう、一定の測定高を維持した状態に保たれる。すなわち、該金属薄膜１１ａがコイル１２ａ’に近づいたときに発生する渦電流損に相当する抵抗Ｒｕが、上記等価回路に直列的に付加されたとみなすことにより、シート抵抗測定時のシート抵抗測定器の等価回路を得る。なお、コイル１２ａ’の内部抵抗は０と仮定している。
【０１３９】
上記金属薄膜１１ａをコイル１２ａ’に近づけた状態のシート抵抗測定器において、コイル１２ａ’を発振させ、交流電源５４の駆動周波数を調整して該コイル１２ａ’の共振特性をとると、図１７（ａ）に示すような特性グラフが得られる。そして、該特性グラフに示すように、コイル１２ａ’が共振するときの駆動周波数がｆ０、電流計４１を流れる電流の値（Ｉｓ）がＩｒであるとし、続いて、金属薄膜１１ａとコイル１２ａ’とを近づけたままで駆動周波数を変化させて、駆動周波数ｆ０の上下ｆ１，ｆ２でのＩｓが共にＩになったとすると、上記式（１４）の関係が成立する。すなわち、金属薄膜１１ａとコイル１２ａ’とを一定距離に近づけた状態で、コイル１２ａ’が共振する駆動周波数ｆ０、並びに電流Ｉが流れる駆動周波数ｆ１，ｆ２をもとめることにより上記抵抗Ｒｕの抵抗値を算出し、該抵抗値とシート抵抗値との相関より、金属薄膜１１ａのより精密なシート抵抗値をもとめることが実現可能となる。
【０１４０】
なお、本発明にかかるシート抵抗測定方法は、図１８に示すように、金属薄膜が形成されたガラス基板１１をロボットハンド５８により製造ラインから取り出し、オフライン検査装置（シート抵抗測定器）５７内に導入して行われてもよい。オフライン検査装置５７はクリーンルーム５７ａ内を一定の温度に管理するためのＨＥＰＡ（温度が一定な気流を一定量流す温度管理装置）５６が温度制御手段として設けられており、そのＨＥＰＡ５６による一定気流下に、センサヘッド１２…を設置することで測定結果の安定性を高めることができる。さらに、ＨＥＰＡ５６を用いることにより、ガラス基板１１上の金属薄膜やセンサヘッド１２への塵埃の付着を防止できて、より安定したシート抵抗の測定が可能となる。
【０１４１】
また、本発明にかかるコイル部としては、上記説明のもの以外にも、フェライトコアなどを軸心として採用したものや、コイルを構成する金属線としてリッツ線を採用したものを用いてもよい。これらの構成によれば、測定対象である金属薄膜に対し、より強い磁力線を照射することができるので、該金属薄膜内に、そのシート抵抗値とより確実に相関がとれる大きさの渦電流を発生させることができる。すなわち、より安定したシート抵抗の測定が可能となる。なお、フェライトコアを使用する場合には、一般に温度ドリフトの影響が懸念されるが、本願発明のように、金属薄膜の形成部に後続されたロードロック室から搬出された比較的低温の金属薄膜を対象とすることで、この問題は生じない。
【０１４２】
【発明の効果】
本発明にかかるシート抵抗測定方法は、以上のように、シート抵抗の測定対象である薄膜状被測定体の形成部に後続されたロードロック室から搬出された金属薄膜の片面側に対してコイル部から磁界の磁力線を照射し、生じる渦電流損に応じた上記磁界の変化量を、該金属薄膜のシート抵抗として検出する方法である。
上記の方法によれば、渦電流損に応じた微量な磁界の変化量を安定かつ高精度に検出することができる。すなわち、該金属薄膜のシート抵抗を、安定かつ高精度に測定することが可能となるという効果を加えて奏する。
【０１４３】
本発明にかかるシート抵抗測定方法はまた、上記方法を前提として、上記第二の工程において、上記渦電流損に相当する抵抗が、上記コイル部を含んでなる直列共振回路に直列的に付加されるとみなす方法である。
【０１４４】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記第二の工程において、上記渦電流損に相当する抵抗が、上記コイル部を含んでなる直列共振回路に並列的に付加されるとみなす方法である。
【０１４５】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記磁界の変化量を、上記直列共振回路におけるインピーダンスの変化量として取得する方法である。
【０１４６】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記磁界の変化量を、上記直列共振回路におけるインダクタンスの変化量として取得する方法である。
【０１４７】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記磁界の変化量を、上記直列共振回路における静電容量の変化量として取得する方法である。
【０１４８】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記磁界の変化量を、上記直列共振回路における共振周波数の変化量として取得する方法である。
【０１４９】
上記いずれかの方法によれば、該金属薄膜に非接触でシート抵抗を測定できるので、該金属薄膜に損傷を与える虞がない。また、従来の両側式渦電流法と比較して簡素な構成で、シート抵抗を測定可能となるという効果を奏する。
【０１５０】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記渦電流損に相当する抵抗の抵抗値を、リアクタンス変化法にてもとめる方法である。
【０１５１】
本発明にかかるシート抵抗測定方法はさらに、上記の方法を前提として、上記渦電流損に相当する抵抗の抵抗値を、周波数変化法にてもとめる方法である。
【０１５２】
上記いずれかの方法によれば、例えば、オフラインなど迅速性がさほど要求されないシート抵抗測定において、特に高精度な測定を実現可能となるという効果を加えて奏する。
【図面の簡単な説明】
【図１】本発明にかかる測定方法が適用されるシート抵抗測定器の概略構成を示す説明図である。
【図２】図１に示すシート抵抗測定器の要部構成を示す説明図である。
【図３】本発明にかかる測定方法の原理の一例を説明するための説明図である。
【図４】本発明にかかる測定方法が適用されるシート抵抗測定器の等価回路の一例を示す説明図である。
【図５】本発明のシート抵抗測定方法を用い、４探針値との相関からゲート膜のシート抵抗値を算出した結果を示すグラフである。
【図６】本発明にかかる測定方法の原理の他の例を説明するための説明図である。
【図７】本発明にかかる測定方法が適用されるシート抵抗測定器の等価回路の他の例を示す説明図である。
【図８】本発明にかかる測定方法の原理のさらに他の例を説明するための説明図である。
【図９】本発明にかかる測定方法が適用されるシート抵抗測定器の等価回路のさらに他の例を示す説明図である。
【図１０】本発明にかかる測定方法が適用されるシート抵抗測定器の等価回路のさらに他の例を示す説明図である。
【図１１】本発明にかかる測定方法が適用されるシート抵抗測定器のコイル部に金属薄膜が近づいて、静電容量が付加された状態を説明する説明図である。
【図１２】（ａ）は、本発明にかかる測定方法の原理のさらに他の例を示す説明図であり、（ｂ）は、該原理が適用されるシート抵抗測定器の等価回路のー例を説明するための説明図である。
【図１３】（ａ）は、本発明にかかる測定方法の原理のさらに他の例を示す説明図であり、（ｂ）は、該原理が適用されるシート抵抗測定器の等価回路のー例を説明するための説明図である。
【図１４】（ａ）・（ｂ）は、本発明にかかる測定方法の原理のさらに他の例を示す説明図である。
【図１５】（ａ）・（ｂ）は、本発明にかかる測定方法の原理のさらに他の例を示す説明図である。
【図１６】（ａ）・（ｂ）は、図１４にて説明する原理が適用されたシート抵抗測定器の説明図であり、（ａ）は該原理を、（ｂ）は、該原理が適用されるシート抵抗測定器の等価回路のー例を示す。
【図１７】（ａ）・（ｂ）は、図１５にて説明する原理が適用されたシート抵抗測定器の説明図であり、（ａ）は該原理を、（ｂ）は、該原理が適用されるシート抵抗測定器の等価回路のー例を示す。
【図１８】本発明にかかる測定方法が適用されたシート抵抗測定器としてのオフライン検査装置の概略構成を示す斜視図である。
【図１９】電磁誘導現象を説明する説明図である。
【図２０】図２１で説明する電磁誘導現象を、本発明にかかるシート抵抗測定方法に応用した例を示す説明図である。
【図２１】従来の４探針法によるシート抵抗測定方法を示す概略斜視図である。
【図２２】従来の両側式渦電流法によるシート抵抗測定方法を示す概略構成図である。
【符号の説明】
１１ａ 金属薄膜（薄膜状被測定体）
１１ｂ 渦電流
１２ センサヘッド
１２ａ コイル（コイル部）
１２ａ’ コイル（コイル部）
１２ｂ 磁界
３０２ コイル（コイル部）
３０６ 金属薄膜（薄膜状被測定体）
３０７ 渦電流
Ｒｕ 抵抗（渦電流損に相当する抵抗）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-contact type sheet resistance measuring method for measuring the sheet resistance of a thin film-like object to be measured such as a metal film or an alloy film formed by, for example, a sputtering method or a vapor deposition method.
[0002]
[Prior art]
As a conventional sheet resistance measuring device, one using a four-probe method is known. Hereinafter, the principle of the four-probe method will be described with reference to the drawings. As shown in FIG. 21, in this method, four needle-like electrodes are used as the probe. These four needle-like electrodes are configured such that all of the tip portions can be simultaneously pressed into contact with the thin film-like object to be measured.
[0003]
For example, when the sheet resistance of the metal thin film 102 formed on the substrate 101 is measured, four electrodes are arranged on a straight line at a predetermined interval so as to be pressed against the upper surface of the metal thin film 102. In FIG. 21, the pair of electrodes disposed on the outside is referred to as probes (current probes) 103 and 103, and the pair of electrodes disposed on the inside is referred to as probes (voltage probes) 104 and 104.
[0004]
Subsequently, a constant current I is passed between the probes 103 and 103 connected to a power source (not shown), and the potential difference generated between the probes 104 and 104 is measured by a potentiometer (not shown). , Resistance (R = V / I) is obtained. The sheet resistance of the metal thin film 102 is obtained as resistivity (specific resistance: ρ) = F × R × T. T represents the thickness of the metal film 102, and F represents a correction coefficient which is a dimensionless numerical value obtained from the shape and dimensions of the metal thin film 102 and the distance between the probes.
[0005]
However, in the four-probe method described above, since a needle-shaped electrode (metal needle) is pressed against the object to be measured, for example, 1) there is a risk of causing damage to the metal thin film 102 or generation of dust. In addition, there are problems such as 2) wear of needle-like electrodes, and periodic replacement work required. Further, 3) Since the sheet resistance cannot be measured in a state where the measured object is vibrating, there are restrictions such as providing a dedicated suction stage for fixing the measured object. In this case, if space restrictions are severe, problems such as difficulty in introduction (installation) into an existing process or in-line implementation will occur.
[0006]
[Problems to be solved by the invention]
Therefore, in order to avoid the above problem, a method of measuring the sheet resistance (resistivity) of a thin film semiconductor material (thin film object to be measured) without pressing the electrodes as in the 4-probe method, that is, non-contact measurement. A law was proposed.
[0007]
In the above method, for example, a metal thin film formed on a semiconductor substrate such as a glass substrate or a wafer is positioned in a magnetic field from a coil to which high frequency power is applied, and the magnetic field and the metal thin film are electromagnetically coupled. This is a double-sided eddy current method characterized in that an eddy current is generated in the metal thin film. The generated eddy current is consumed as Joule heat, and it is non-contact by utilizing the positive correlation between the absorption of the high frequency power in the metal thin film and the conductivity (reciprocal of resistivity). The resistivity of the metal thin film is calculated.
[0008]
That is, unlike the four-probe method, the double-sided eddy current method is characterized in that the resistivity of the metal thin film can be calculated from the detection result obtained without contacting the metal thin film. Also in the final processing steps of semiconductor products such as semiconductor products and liquid crystal panels, it is possible to avoid applying contamination and force to the metal thin film and the semiconductor substrate on which the metal thin film is formed.
[0009]
A specific example of such a double-sided eddy current method is as follows. First, for example, as shown in FIG. 22, a substantially U-shape having two side portions 202 a and 202 a which are two opposing surfaces facing each other so as to have a gap (gap width) 201 of 1 to 4 mm. A high frequency power is applied to the coil 202b of the ferrite (magnetic material) core 202 of the steel.
[0010]
Subsequently, when a wafer 203 having a metal thin film is inserted into the gap 201, an eddy current is generated in the metal thin film by high frequency inductive coupling, and the generated eddy current is consumed as Joule heat. Absorption occurs in the metal film. Since this absorption and the conductivity of the metal thin film have a positive correlation with each other, the resistivity of the metal thin film on the wafer 203 is measured in a non-contact manner from the ratio of the absorption.
[0011]
In recent years, for the purpose of quality control in the manufacturing process of a semiconductor substrate, a small-sized resistance measuring instrument for sheet resistance monitoring using the double-sided eddy current method or the like has been developed. For example, Japanese Patent Application Laid-Open No. 6-69310 discloses a wafer measurement system in which a resistance measuring device is provided in parallel with the moving direction of the transfer robot of the loader unit, and the resistivity is measured by the resistance measuring device during transfer. . Regarding the resistance measuring instrument described in the above publication, there is no description that the double-sided eddy current method is used to measure the resistivity in a non-contact manner. It is presumed that a resistance measuring instrument or a non-contact type resistance measuring instrument employing the double-sided eddy current method is used.
[0012]
In the measurement system, in order to measure the resistivity of the metal thin film on the wafer, an operation flow for temporarily stopping the transfer robot or inserting or transferring the wafer into the resistance measuring instrument is provided. A method of measuring the resistivity in the middle is adopted. In other words, in the case of the double-sided eddy current method or the four-probe method, additional specifications such as 1) stopping the apparatus and 2) adding an operation flow other than transfer to the transfer robot are required. There is a negative cost with the increase of tact and the addition of software for adding operation flow other than transport.
[0013]
In addition, the introduction of the above measurement system into the existing semiconductor substrate manufacturing process is as follows: 1) the resistance measuring instrument is insufficient in sensitivity; 2) it is difficult to secure a mounting space; There are problems such as the need for a (conveying robot) and it is extremely difficult.
[0014]
Therefore, in order to solve the above problem, a single-sided eddy current type (hereinafter referred to as single-sided) measuring instrument has been proposed as another sheet resistance measuring instrument employing a non-contact measuring method. The measuring instrument is characterized in that only one side of a conductive thin film-like object to be measured is irradiated with a magnetic field line of a magnetic field from a coil to which high-frequency power is applied. An eddy current loss is detected by generating an electric current, and the material, film thickness, etc. of the object to be measured are acquired as a sheet resistance value.
[0015]
For example, Japanese Patent Laid-Open No. 5-21382 discloses an eddy current that generates eddy current in a metal thin film (sputtered film) formed by a sputtering method, detects a magnetic field line accompanying the generated eddy current, and calculates sheet resistance. A detection type measuring instrument is described.
[0016]
More specifically, the above publication discloses a system in which a sputtering apparatus and a load lock chamber are disposed adjacent to each other via a gate valve so that connection and blocking can be performed spatially. Is provided with a transport means for transporting a substrate on which a metal thin film is formed in the load lock chamber, and the sheet resistance measuring instrument, and controls the sheet resistance of the metal thin film by changing the sputtering conditions in the sputtering apparatus. Means are provided. That is, the system aims to form a uniform metal thin film by feeding back the measurement result of the sheet resistance and changing the sputtering conditions as appropriate.
[0017]
However, the above system employs a method of measuring the sheet resistance of the metal thin film immediately after film formation. Since the substrate temperature at this point is high, a large variation occurs in the measured sheet resistance value. That is, at high temperatures, it is difficult to obtain good measurement results due to the influence of expansion of the coil of the eddy current type sheet resistance measuring instrument, temperature dependence of the sheet resistance value, and the like. In addition, if the sheet resistance measuring device is installed in the load lock chamber, there is a problem that its maintainability is poor and work efficiency is low. From these problems, it is considered difficult to measure the sheet resistance value of the formed metal thin film and feed it back to the next film formation.
[0018]
USP-5,660,672 also proposes a one-side type sheet resistance measuring device, and the measuring device has a structure for efficiently converging magnetic flux by a coil wound around a coupling type ferrite or the like. It has been adopted. However, it is difficult to detect stable output voltage due to temperature drift when using ferrite etc. in the several hundred MHz region, and it should not be used when stable and highly accurate measurement is required. Have difficulty.
[0019]
The present invention has been made in order to solve the above-mentioned problems, and its purpose is, for example, in the manufacturing process of a liquid crystal panel substrate or a semiconductor substrate, to measure the sheet resistance of a thin film formed on these substrates, The present invention relates to a one-side type sheet resistance measuring method that is in contact with the thin film and can be executed with high accuracy.
[0020]
[Means for Solving the Problems]
A sheet resistance measuring method according to the present invention is a method of measuring a sheet resistance of a thin film-like object to be measured using a sensor head including a coil unit that generates a magnetic field,The thin film-like object to be measured is a metal thin film carried out from a load-lock chamber following the formation part of the thin-film-like object to be measured, and a constant amount of air current is passed through the sensor head and the metal thin film. A process of installing under an air current;the aboveMetal thin filmThe magnetic field lines of the magnetic field are irradiated from one side of the coil to the coil side,Metal thin filmThe first step of forming an eddy current due to the magnetic field and the amount of change in the magnetic field according to the eddy current loss caused by the formation of the eddy current,Metal thin filmAnd a second step of detecting the sheet resistance.
[0021]
In the sheet resistance measuring method according to the present invention, on the premise of the above method, in the second step, a resistance corresponding to the eddy current loss is added in series to a series resonance circuit including the coil section. The amount of change in the magnetic field is acquired.
[0022]
In the sheet resistance measuring method according to the present invention, on the premise of the above method, in the second step, a resistance corresponding to the eddy current loss is added in parallel to the series resonance circuit including the coil section. The amount of change in the magnetic field is acquired.
[0023]
The sheet resistance measuring method according to the present invention is further characterized in that the amount of change in the magnetic field is acquired as the amount of change in impedance in the series resonance circuit on the premise of the method described above.
[0024]
The sheet resistance measuring method according to the present invention is further characterized in that the change amount of the magnetic field is acquired as the change amount of inductance in the series resonance circuit on the premise of the above method.
[0025]
The sheet resistance measuring method according to the present invention is further characterized in that the amount of change in the magnetic field is acquired as the amount of change in capacitance in the series resonant circuit on the premise of the method described above.
[0026]
The sheet resistance measurement method according to the present invention is further characterized in that the change amount of the magnetic field is acquired as a change amount of the resonance frequency in the series resonance circuit on the premise of the above method.
[0027]
According to any of the above methods, the thin film-like object to be measuredMetal film unloaded from the load lock chamber following the formation sectionBased on the magnitude of eddy current generated by electromagnetic induction,Metal thin filmSince the sheet resistance can be measured in a non-contact manner,Metal thin filmThere is no risk of damage. Also,The metal thin filmSince it is only necessary to arrange the coil part so that the magnetic field lines of the magnetic field are irradiated only to one side of the, in a simple configuration compared with the conventional double-sided eddy current method,The metal thin filmThe sheet resistance can be measured.In addition, since the metal thin film, which is the object of sheet resistance measurement, is at a relatively low temperature compared to when it is in the formation section or load lock chamber, a small amount of magnetic field change corresponding to eddy current loss can be obtained. It can be detected stably and with high accuracy. That is, the sheet resistance of the metal thin film can be measured stably and with high accuracy.
In particular, when the sheet resistance of a high-resistance metal thin film such as ITO is measured, the generated eddy current loss becomes extremely fine, so that the advantage of using the above method is extremely great.
[0028]
The sheet resistance measuring method according to the present invention is further characterized in that the resistance value corresponding to the eddy current loss is determined by the reactance change method based on the above method.
[0029]
The sheet resistance measuring method according to the present invention is further characterized in that the resistance value corresponding to the eddy current loss is determined by the frequency change method on the premise of the above method.
[0030]
According to any one of the above methods, it is possible to realize particularly high-precision measurement in sheet resistance measurement that does not require much quickness such as offline.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited thereby.
[0035]
The sheet resistance measuring method according to the present invention is as follows: 1) A magnetic field line is applied to only one side of a thin film-like object to be measured from the coil portion that generates a magnetic field, and the thin film-like object to be measured is subjected to the magnetic field. A first step of forming an eddy current; and 2) a second step of detecting the amount of change in the magnetic field according to the eddy current loss caused by the formation of the eddy current as a sheet resistance of the thin film-like object to be measured; Is a method comprising.
[0036]
The principle is as follows. First, as shown in FIG. 19, when a coil 302 to which an alternating current from an alternating current generator 301 is applied is brought close to the coil 303, a voltage is generated in the coil 303 due to an electromagnetic induction phenomenon. It is known that an alternating current (inductive current) flows through the meter 304 and the load resistor 305.
[0037]
In the same manner, instead of the coil 303, as shown in FIG. 20, a coil (coil portion) 302 to which an AC voltage is applied to a metal thin film (thin film-like object to be measured) 306 as a conductive object to be measured. , An eddy current 307 is generated in the metal thin film 306. Then, due to the generation of the eddy current 307, the resonance state of the closed circuit (closed circuit) is destroyed, and the magnetic field generated by the coil 302 in the closed circuit is changed, and the impedance of the coil 302 (the resistance of the DC circuit is changed). Or the like) changes according to the amount of change in the magnetic field. The present invention uses this principle to measure the sheet resistance of a thin film-like object to be measured. The magnitude of the generated eddy current 307 is determined by the distance to the metal thin film 306 as a measurement target and the material and size of the metal thin film 306.
[0038]
According to the above method, unlike the conventional four-probe method, the sheet resistance can be measured in a non-contact manner on the thin film-like object to be measured based on the magnitude of the eddy current generated by the electromagnetic induction action. There is no risk of damaging the measured object. In addition, the coil portion only needs to be arranged so that only one side of the thin film-like object to be measured is irradiated with the magnetic field lines, so that it can be implemented with a simpler configuration than the conventional double-sided eddy current method. Become. Therefore, for example, in the process of forming a thin film on a liquid crystal panel substrate or a semiconductor substrate, or in a downstream manufacturing process, it involves changing the existing manufacturing flow, and (temporarily) stopping the manufacturing line of the apparatus / transport robot, etc. In addition, it is possible to carry out in-line film quality inspection of a thin film-like object to be measured without reducing the apparatus throughput.
[0039]
In the method of the present invention, in the second step, the resistance corresponding to the eddy current loss is considered to be added in series or in parallel to the series resonance circuit including the coil portion. This is a method for acquiring the amount of change in the magnetic field.
[0040]
The amount of change in the magnetic field is exemplified below, but in the series resonant circuit, 1) the amount of change in impedance, 2) the amount of change in inductance, 3) the amount of change in capacitance, and 4) the amount of resonance frequency. It is possible to obtain the change amount. That is, due to the change in the magnetic field of the coil portion, the resonance state of the series resonance circuit is destroyed and a signal appears at the output. This is read as representing the sheet resistance of the thin film object to be measured, and the sheet resistance value is calculated from the correlation with the 4-probe value.
[0041]
Moreover, it is more preferable that the sheet resistance measuring method according to the present invention is performed on a thin film-like object to be measured carried out from a load-lock chamber following the formation part of the thin-film-like object. For example, when the method of the present invention is executed on the production line, the thin film-like object to be measured is inlined downstream from the load lock chamber following the film formation chamber (formation section: sputtering apparatus chamber, etc.). It is more preferable. Further, the sheet resistance measuring method according to the present invention may be applied off-line, and in this case as well, in the same way as in-line, the sheet resistance measuring method is carried out from the load lock chamber following the film forming chamber of the thin film object to be measured. More preferably, the thin film-like object to be measured is taken out of the production line and measured.
[0042]
This is because the thin film-like object to be measured is in a very high temperature state immediately after formation in the film forming chamber or the load lock chamber following the film forming chamber. This is because it may be difficult to obtain a good measurement result under the influence of the temperature dependency of the resistance and the like. As described above, when the sheet resistance measurement is performed on a thin film-like object to be measured (generally formed on a substrate) carried out of the load lock chamber, the thin film-like object to be measured is formed into a film. It is in a relatively low temperature state compared to when it is in a room or a load lock room, and it is possible to detect a small amount of magnetic field change caused by eddy current loss stably and with high accuracy. In particular, when the sheet resistance of a high-resistance metal thin film such as ITO is measured, the generated eddy current loss becomes extremely fine, so the advantage is extremely great.
[0043]
Needless to say, the “load lock chamber following the film formation chamber” refers to a load lock chamber directly connected to the downstream side of the film formation chamber. Further, for example, in the film forming chamber or the load lock chamber following the film forming chamber, for example, if the temperature can be kept constant with a temperature fluctuation range within ± 1 ° C., the method of the present invention is applied. Thus, it is possible to measure the sheet resistance of the thin film-like object to be measured.
[0044]
Hereinafter, with reference to FIG. 1 and FIG. 2, the structure of the sheet resistance measuring instrument in which the above-described measuring method is adopted will be described, and the measuring method according to the present invention will be described in more detail.
[0045]
As shown in FIG. 1, the sheet resistance measuring device is a device for measuring the sheet resistance of a metal thin film (thin film-like object) 11 a formed on the surface of a glass substrate (substrate) 11. A sensor head 12 having a built-in coil (coil part) 12a for generation is provided. The coil 12a has a coreless cylindrical shape. Further, an amplifier (sheet) that includes a high-frequency AC oscillation circuit (see FIG. 2) 13a that supplies high-frequency power to the coil 12a, and that converts a detection signal (signal voltage) obtained by the sensor head 12 into a DC voltage value and outputs it. Resistance detection means) 13 and an AC power supply 14 for supplying power to the amplifier 13.
[0046]
At the time of sheet resistance measurement, the glass substrate 11 is supported by a support / conveying means (not shown) so that the formation surface of the metal thin film 11a is the upper surface and is positioned horizontally above the sensor head 12 with a predetermined measurement height. It is brought in. The sensor head 12 generates the magnetic field 12b toward the glass substrate 11, that is, the center line of the magnetic force line of the magnetic field 12b is orthogonal to the metal thin film 11a. The magnetic field 12b and the metal thin film 11a As a result, an eddy current (see FIG. 2) 11b is generated in the metal thin film 11a. Since the generated eddy current 11b is consumed as Joule heat, power loss (eddy current loss) occurs. The amount of change in the magnetic field of the coil 12a in accordance with the eddy current loss is reduced in the coil 12a. The sensor head 12 acquires the difference between the supplied high-frequency power and the high-frequency power returned from the coil 12a, and outputs it as a detection signal (signal voltage) to the amplifier 13.
[0047]
More specifically, as shown in FIG. 2, the amplifier 13 separates a high-frequency AC oscillation circuit 13a connected to the coil 12a and a necessary signal wave (voltage value) from a modulation wave from the high-frequency AC oscillation circuit 13a. And a detection circuit 13b.
[0048]
When high frequency power is supplied from the high frequency AC oscillation circuit 13a, the coil 12a generates a magnetic field 12b toward the metal thin film 11a, and generates an eddy current 11b in the metal thin film 11a. At this time, the eddy current 11b generated in the metal thin film 11a is lost as Joule heat, and the high-frequency power input to the high-frequency AC oscillation circuit 13a through the coil 12a changes.
[0049]
That is, in the high-frequency AC oscillation circuit 13a, the high-frequency power output to the coil 12a and the high-frequency power returned from the coil 12a change due to the generation of the eddy current 11b. The magnitude of the eddy current 11b is determined by the distance between the metal thin film 11a and the sensor head 12 to be measured for the sheet resistance value, the size of the sensor head 12, the material and thickness of the metal thin film 11a, and the like. The detected value of the high frequency power detected in correlation with the magnitude of the eddy current 11b changes.
[0050]
The change in the high frequency power is input from the high frequency AC oscillation circuit 13a to the detection circuit 13b as a modulation wave, and the detection circuit 13b separates the signal wave from the modulation wave. This signal wave is converted into a DC voltage value and is output to the A / D converter 15 as a voltage signal as shown in FIG.
[0051]
The method for forming the eddy current in the metal thin film 11a is not particularly limited, and the electromagnetic induction effect may be introduced by changing the relationship between the metal thin film 11a and the magnetic flux (that is, the magnetic field) linked to the metal thin film 11a. . For example, 1) without changing the metal thin film 11a, the intensity of the magnetic flux linked to the metal thin film 11a is changed, or 2) the intensity of the magnetic flux linked to the metal thin film 11a is kept constant and the metal thin film 11a is changed. Move it. For example, the glass substrate 11 on which the metal thin film 11a is formed may be carried directly under the coil 12a and carried out from there while generating a constant magnetic flux from the coil 12a.
[0052]
The sensor head 12 is provided only on one surface of the glass substrate 11 (that is, the metal thin film 11a), that is, so as to face one surface. At this time, the metal thin film 11a formation surface of the glass substrate 11 may be a facing surface of the sensor head 12, or may be a back surface as shown in FIG.
[0053]
Although not shown, an amplifier circuit is provided in the vicinity of the sensor head 12, thereby amplifying the high-frequency power output from the high-frequency AC oscillation circuit 13a of the amplifier 13 and inputting it to the coil 12a. More preferably, the signal voltage (detection signal) from the sensor head 12) is amplified and output to the amplifier 13.
[0054]
For example, the amplifier 13 converts the detection signal from the sensor head 12 into a one-to-one amplified signal using an operational amplifier, converts the amplified signal into a DC voltage effective value as a detection result, and converts the converted DC voltage value to A / D Output to the converter 15.
[0055]
The A / D converter 15 converts the voltage value (analog signal) from the amplifier 13 into a digital signal, and outputs the digital signal (A / D conversion value) to a control device 16 such as a microcomputer. The control device 16 calculates the sheet resistance value of the metal thin film 11a based on the digital signal from the A / D converter 15, and stores the sheet resistance value in a memory. The control device 16 is provided with a monitor 16a that displays the sheet resistance value of the metal thin film 11a. That is, only by monitoring the monitor 16a of the control device 16, the monitor can find an abnormality in the sheet resistance value of the metal thin film 11a. Needless to say, it is more preferable to configure the control device 16 so that an error signal is generated regardless of the presence or absence of a monitor when a sheet resistance value outside the range of the reference value is detected.
[0056]
When the sheet resistance value is calculated based on the digital signal from the A / D converter 15 in the control device 16, for example, the four-probe value calculated according to the film forming condition of the metal thin film 11a The detected voltage change may be converted into a sheet resistance value based on the sheet resistance correlation line obtained from the above correlation.
[0057]
Note that the glass substrate 11 on which the metal thin film 11a having an abnormal sheet resistance value is formed may be removed from the production line. In addition, when abnormality is continuously found in the sheet resistance values of the plurality of metal thin films 11a, it is considered that the film forming conditions of the metal thin film 11a are abnormal. Therefore, the film formation process located upstream of the sheet resistance measurement process may be controlled based on the obtained abnormal value data.
[0058]
Hereinafter, each measurement principle employed in the sheet resistance measurement method according to the present invention will be described in detail.
[0059]
More specifically, one of the sheet resistance measuring methods according to the present invention is a sheet in which the resistance corresponding to the eddy current loss caused by the formation of the eddy current 11b in the metal thin film 11a includes the coil 12a. This is a method of obtaining the amount of change in the magnetic field in the coil 12a, assuming that the resistance is measured in series or in parallel with a series resonance circuit that is an equivalent circuit of the resistance measuring instrument. That is, this is a resistance replacement method in which the eddy current loss is replaced with an additional resistor, and the current or voltage flowing through the series resonant circuit, which is a closed circuit, is detected.
[0060]
Assuming that the resistance corresponding to the eddy current loss is added (connected) in parallel to the series resonance circuit, for example, as shown in FIG. 3, the coil 22a having the self-inductance L1 and the internal resistance r1 is connected to the series resonance circuit. Capacitor C₁₁In addition, a resistance Ru corresponding to eddy current loss is connected in parallel to a series resonance circuit (L, C, R series resonance circuit) having a configuration in which an AC power supply 51 is connected in series. More specifically, this indicates a state where the resistor Ru is connected to the coil 22a in parallel. Hereinafter, the resonance circuit shown in FIG. 4 will be used as an equivalent circuit of the sheet resistance measuring device shown in FIG. 1, and a method for detecting current or voltage will be described in more detail.
[0061]
As shown in FIG. 4, the resonance circuit includes a coil 12a and a series resonance capacitor C.₁₁, Resistance R₁(For convenience, this resistance value is also R₁And a series resonant circuit having a configuration in which the AC power supply 14 is connected in series. The coil 12a has a self-inductance L and an internal resistance r connected in series, and a coil stray capacitance C₁₀Are considered to be connected in parallel. Furthermore, the resonance circuit has a resistance R₁Is connected in series with an OP amplifier galvanometer (ammeter) 23 that directly detects a change amount ΔI of the current flowing through the. Further, when the metal thin film 11a approaches the coil 12a, it is considered that a resistor Ru corresponding to an eddy current loss is connected in parallel with the series resonance circuit, more specifically, the coil 12a. The resonance circuit shown in FIG. 4 is an equivalent circuit for explaining a resistance conversion method in which the amount of change in the magnetic field of the coil 12a is regarded as the amount of change in the impedance of the entire resonance circuit. .
[0062]
That is, the angular frequency of AC is ω and the capacitor C₁₁Is the capacitance of C, the internal resistance of the OP amplifier galvanometer 23 is 0, and the resistance value of the resistor Ru is R₂As the impedance Z of the entire circuit shown in FIG.
[0063]
[Expression 1]

[0064]
Since the resonance condition of the resonance circuit is imaginary part = 0 in the equation (1), the impedance Z is
[0065]
[Expression 2]

[0066]
It becomes.
[0067]
The impedance Z represented by the above formula (2) is R₂≠ 0, that is, the impedance of the resonant circuit in a state where the metal thin film 11a is close to the coil 12a (hereinafter, Z₁Called). Further, the impedance of the resonance circuit (hereinafter referred to as Z) when the metal thin film 11a is not brought close to the coil 12a.₀In the formula (2)₂= 0 is substituted,
Z₀= R₁
It becomes.
[0068]
And if the resonant circuit shown in FIG. 4 is regarded as a constant voltage circuit,
Z · I = E (constant) · · · (3)
That is, the above method is a method of capturing the change in the impedance Z of the entire resonance circuit as a change in the resistance value of the series circuit (a resistance Ru is added in parallel).
[0069]
In the resonance circuit, as shown in the equation (3), since the current I flowing through the circuit and the impedance Z of the entire circuit are in an inversely proportional relationship, the amount of impedance change caused by the approach of the metal thin film 11a ( ΔZ = Z₀-Z₁) And the amount of change in current (ΔI = ΔI)₀-ΔI₁) Is in an inversely proportional relationship. That is, the change amount ΔI of the current flowing through the resonance circuit can be regarded as the change amount ΔZ of the impedance of the resonance circuit.
[0070]
More specifically, when measuring the sheet resistance of the metal thin film 11a, the resistance R is first set in a state where the metal thin film 11a is not brought close to the coil 12a.₁Current I flowing through₀Then, in the state where the metal thin film 11a is brought close to the coil 12a with a certain measurement height, the resistance R₁Current I flowing through₁Measure. As a result, the amount of change ΔI in current caused by the approach of the metal thin film 11a can be obtained as the amount of change ΔZ in impedance. Note that the OP amplifier galvanometer 23 shown in FIG. 4 has a current change amount (ΔI = I) before and after the metal thin film 11a is approached.₀-I₁) Directly.
[0071]
As shown in FIG. 4, the amount of change in the magnetic field generated by bringing the metal thin film 11a closer is the resonance circuit (more specifically, the resistance R₁It is more preferable to directly measure the amount of change in the current flowing in (3) as a high-frequency alternating current corresponding to the raw eddy current loss. However, when the change in the current is weak, instead of the OP amplifier galvanometer 23, the resistance R₁A voltmeter may be provided in parallel.
[0072]
For example, when measuring the sheet resistance of a high-resistance metal thin film such as ITO, the resistance R₁The amount of change in the current flowing through the circuit becomes extremely weak, and accurate measurement may not be possible with a general ammeter. In this case, the amount of change ΔI of the current flowing through the resonant closed circuit (the resonance circuit) is determined as the resistance R for detection.₁(1 kΩ in this embodiment) is amplified and obtained as a voltage change ΔV by a voltmeter. If ΔI needs to be obtained from ΔV, ΔV = R₁-What is necessary is just to calculate using the relationship of (DELTA) I.
[0073]
The sheet resistance value of the metal thin film 11a is calculated using the correlation between the obtained ΔV or ΔI and the sheet resistance value. For example, the amplifier 13 having the high-frequency oscillation circuit 13a and the detection circuit 13b shown in FIG.₁₁An example is shown below in which the voltage change amount ΔV is obtained and the sheet resistance value of the metal thin film 11a is calculated based on the ΔV in the control device 16 shown in FIG.
[0074]
The graph shown in FIG. 5 shows the results of measuring the sheet resistance values of a plurality of gate films (TiN / Al / Ti laminated film: the standard layer thickness of each layer is 1500 mm, 3000 mm, 300 mm) as the metal thin film 11a. Is. More specifically, the same gate film as the sheet resistance value (four probe values shown on the x-axis of the graph) obtained by the four-probe sheet resistance measurement method is measured by the method of the present invention. The sheet resistance value of the gate film is calculated from the relationship with the obtained voltage change amount ΔV (average value obtained by measuring the same gate film a plurality of times: equivalent to the detected voltage ΔV shown on the y-axis of the graph). The results are shown.
[0075]
The control means 16 (see FIG. 1) calculates the correlation between the voltage change amount ΔV and the sheet resistance value by the four-probe method by curve approximation, more specifically logarithmic approximation. In the graph, black squares indicate the values of ΔV of the gate film corresponding to the four probe values, and solid lines indicate logarithmic approximation curves representing the correlation between the two. As is apparent from the graph, the value of ΔV of the gate film corresponding to each of the four probe values is one logarithmic approximate curve,
y = −0.5271Ln (x) −0.2917
You can see that it is almost on the top. That is, if ΔV is measured by the method of the present invention, this value can be substituted for y of the logarithmic approximation curve to calculate the sheet resistance value (4 probe value) x.
[0076]
The graph shown in FIG. 5 shows the measurement error of the sheet resistance value measured by the method according to the present invention, that is, the ΔV and the logarithmic approximation curve obtained for the gate film indicating the 4-probe value x. error from y value,
[ΔV− (y value)] / (y value) × 100 (%)
Is also indicated by a white square. According to the method of the present invention, the measurement error can be suppressed within ± 2.3%, and the total inspection management of the sheet resistance of the gate film becomes possible.
[0077]
On the other hand, assuming that the resistance corresponding to the eddy current loss is added (connected) in series to the series resonance circuit, as shown in FIG. 6, the coil 22a having the internal resistance r1 with the self-inductance L1 is connected to the series resonance circuit. Capacitor C₁₁In addition, a resistance Ru corresponding to eddy current loss is connected in series to a series resonance circuit (L, C, R series circuit) having a configuration in which an AC power supply 51 is connected in series. More specifically, this indicates a state in which the resistor Ru is connected to the coil 22a in series. Hereinafter, the resonance circuit shown in FIG. 7 will be used as an equivalent circuit of the sheet resistance measuring device shown in FIG. 1, and a method for detecting current or voltage will be described in more detail.
[0078]
As shown in FIG. 7, the resonance circuit includes a coil 12a and a capacitor C for series resonance.₁₁, Resistance R₁(For convenience, this resistance value is also R₁And a series resonant circuit having a configuration in which the AC power supply 14 is connected in series. The coil 12a has a self-inductance L and an internal resistance r connected in series, and a coil stray capacitance C₁₀Are considered to be connected in parallel. Furthermore, the resonance circuit has a resistance R₁Is connected in series with an OP amplifier galvanometer (ammeter) 23 that directly detects a change amount ΔI of the current flowing through the. Further, when the metal thin film 11a approaches the coil 12a, it is considered that a resistor Ru corresponding to eddy current loss is connected in series with the series resonance circuit, more specifically, the coil 12a. The resonance circuit shown in FIG. 7 is an equivalent circuit for explaining a resistance conversion method in which the amount of change in the magnetic field of the coil 12a is regarded as the amount of change in the impedance of the entire resonance circuit. This is simplified by considering that the resistor Ru is added in parallel to the resonant circuit (see FIG. 4).
[0079]
That is, the angular frequency of AC is ω and the capacitor C₁₁Is the capacitance of C, the internal resistance of the OP amplifier galvanometer 23 is 0, and the resistance value of the resistor Ru is R₂As the impedance Z of the entire circuit shown in FIG.
[0080]
[Equation 3]

[0081]
Since the resonance condition of the resonance circuit is imaginary part = 0 in the equation (4), the impedance Z of the resonance circuit is
Z = R₁+ R₂(5)
It becomes.
[0082]
The impedance Z represented by the above formula (5) is R₂≠ 0, that is, the impedance (hereinafter referred to as Z) when the metal thin film 11a is close to the coil 12a.₁Called). In addition, the impedance (hereinafter, Z₀In the formula (5).₂= 0 is substituted,
Z₀= R₁
It becomes.
[0083]
If the resonant circuit shown in FIG. 7 is regarded as a constant voltage circuit,
Z · I = E (constant) · · · (6)
That is, the above method is a method of capturing the change in the impedance of the entire resonance circuit as a change in the resistance value of the series circuit (a resistance Ru is added in series).
[0084]
In the resonance circuit, since the current I flowing through the circuit and the impedance Z of the entire circuit are in inverse proportion as shown in the equation (6), the amount of impedance change (ΔZ generated by the approach of the metal thin film 11a) = Z₀-Z₁) And the amount of change in current (ΔI = ΔI)₀-ΔI₁) Is in an inversely proportional relationship. That is, the change amount ΔI of the current flowing through the resonance circuit can be regarded as the change amount ΔZ of the impedance of the resonance circuit. The resistance Ru is connected in parallel to the resonance circuit with respect to a method of obtaining the change amount ΔI of the current flowing through the resonance circuit, the voltage change amount ΔV, and the correlation method with the four probe values. This is the same as the case where it is regarded as “No.”, and the description is omitted.
[0085]
(Inductance conversion method)
As another example of the sheet resistance measuring method according to the present invention, when a resistance corresponding to eddy current loss is added in series or in parallel to a series resonance circuit that is an equivalent circuit including a coil portion. There is a method (inductance conversion method) in which the amount of change in the magnetic field in the coil portion is regarded as the amount of change in inductance (inductance conversion method).
[0086]
In general, the inductance conversion method refers to a method of converting a change amount such as displacement, vibration, and pressure into an inductance change amount. First, the principle of the inductance conversion method will be described with reference to FIG.
[0087]
When a voltage is applied between coil terminals A and B of a coil part 32 formed by winding a coil 32a around a substantially U-shaped ferrite core 32b, the coil part 32 generates a magnetic flux. At this time, in order to change the inductance between the coil terminals A and B using the metal thin film 11a, generally, the metal thin film 11a or the coil part 32 generating the magnetic flux is moved, and the relative relationship between the two is obtained. A method of displacing the position is used. By displacing the relative position, a time change of the magnetic flux penetrating the metal thin film 11a occurs, and an eddy current due to an electromagnetic induction phenomenon is generated. In other words, the magnetic field of the coil portion 32 is changed by displacing the relative position between the two, and this change is converted into an inductance change between the coil terminals A and B.
[0088]
FIG. 9 is an explanatory diagram showing a schematic circuit configuration of a sheet resistance measuring device to which the inductance conversion method is applied, and a variable resistance R₁₁・ R₁₂, Inductance variable coil L₁₁The coil 12a built in the sensor head 12 (see FIG. 1) and a typical high-frequency bridge 33 comprising an AC power source 52; a rectifier circuit 34 connected to the high-frequency bridge 33; a rectifier circuit 34 connected to the coil 12a A microampere meter 35 that reads a signal (current) generated by the balance of the high-frequency bridge 33 being lost due to a change in the magnetic field as a direct current.
[0089]
In the sheet resistance measuring instrument described above, the inductance of the coil 12a changes as the metal thin film 11a approaches the coil 12a. That is, the amount of change in the magnetic field between when the metal thin film 11a is located directly under the coil 12a and when there is nothing directly under the coil 12a is taken as the amount of change in the inductance of the coil 12a.
[0090]
Then, the amount of change in the inductance is defined as the amount of change ΔI (or ΔV) in the current (or voltage) between the coil terminals A and B of the coil 12a, and the microampere meter 35 (or the voltage connected in parallel to the coil 12a). Read in total). Then, the sheet resistance of the metal thin film 11a is calculated from the correlation between the read ΔI or ΔV and the 4-probe value.
[0091]
In the sheet resistance measuring instrument shown in FIG. 9, a variable inductance type coil L₁₁Thus, fine adjustment is necessary to maintain the balance of the high-frequency bridge 33 (that is, to create an equilibrium state before measurement). However, by using the high-frequency bridge 33, a material (copper or the like) forming the coil 12a is used. The effect of temperature drift can be eliminated, and stable sheet resistance can be calculated.
[0092]
FIG. 10 is an explanatory diagram showing a schematic circuit configuration of another sheet resistance measuring device to which the inductance conversion method is applied, and a resistance R₂₁・ R₂₂, Coil L₁₂A typical high-frequency bridge 33a composed of a coil 12a built in the sensor head 12 (see FIG. 1) and an AC power source 52; a rectifier circuit 34 connected to the high-frequency bridge 33a; a coil 12a connected to the rectifier circuit 34 A microampere meter 35 that reads a signal (current) generated as the balance of the high-frequency bridge 33 a is lost due to the change in the magnetic field as a direct current.
[0093]
Coil L₁₂Is always arranged with a certain measurement height with the metal standard thin film 21a as a reference sample, and in this state, the metal thin film 11a, which is a sheet resistance measurement object, is brought close to the coil 12a. Thereby, NG determination is enabled without calculating the sheet resistance value of the metal thin film 11a. That is, if the high-frequency bridge 33a is driven so that the high-frequency bridge 33a is balanced only when the metal thin film 11a that causes the coil 12a to change the inductance according to the set value is used for the measurement, it is used for the measurement. It is possible to easily determine whether each metal thin film 11a exhibits a desired sheet resistance value.
[0094]
Further, in the sheet resistance measuring instrument shown in FIG. 10 as well, as shown in FIG. 9, the change amount ΔI (or ΔV) of the current (or voltage) between the coil terminals A and B of the coil 12a is measured with a microampere meter. The sheet resistance of the metal thin film 11a may be calculated from the correlation with the 4-probe value by reading with 35 (or a voltmeter connected in parallel to the coil 12a).
[0095]
In the sheet resistance measuring instrument to which the inductance conversion method shown in FIGS. 9 and 10 is applied, the inductance can be increased by the number of turns of the coil 12a. Therefore, in the measurement of the sheet resistance, for example, high frequency power as in the capacitance conversion method exemplified below is not required, and power with a frequency of about several hundred kHz can be used.
[0096]
Further, by utilizing a phenomenon in which a minute change in the magnetic flux generated when the metal thin film 11a approaches the coil 12a that generates the magnetic flux breaks the equilibrium state of the high-frequency bridges 33 and 33a and a signal appears in the output. Sheet resistance can be measured with high accuracy. An application of this principle is known as a lock-in amplifier, for example.
[0097]
(Capacitance conversion method)
As still another example of the sheet resistance measuring method according to the present invention, a resistance corresponding to eddy current loss is added in series or in parallel to a series resonance circuit which is an equivalent circuit including a coil section. And a method (capacitance conversion method) in which the amount of change in the magnetic field in the coil portion is regarded as the amount of change in the capacitance of the series resonance circuit (capacitance conversion method).
[0098]
In general, the capacitance conversion method refers to a method of obtaining by converting a change amount such as a change in length or displacement into a change amount of capacitance, and the change amount is measured by a high frequency of about megacycle. Electric power is used. For such high-frequency power, in addition to the above-described method using the high-frequency bridge, a capacitance conversion method using a change on the resonance curve is also used. Hereinafter, the basic principle of the capacitance conversion method will be described with reference to FIGS. 11 and 12A and 12B.
[0099]
The L, C, R series resonance circuit shown in FIG. 11 is an equivalent circuit of a sheet resistance measuring device, and includes an AC power supply 53, a coil 12a, and the like. Capacitor C₁₂Are connected in series. The coil 12a is a coil in which a self-inductance L and an internal resistance r are connected in series, and a capacitor C₁₂Has a variable capacitance. First, capacitor C₁₂The resonance characteristics of the series resonance circuit are obtained by varying the capacitance of the capacitor, and the applied voltage (V) and the capacitor C₁₂A resonance curve (see FIG. 12 (a)) showing the relationship with the electrostatic capacity is created.
[0100]
A point at which the slope of the tangent line (that is, the amount of change in the resonance curve) is maximum is calculated on the resonance curve, and the capacitance C at this point is calculated.₀Capacitor C₁₂As an initial value of the electrostatic capacity, the series resonance circuit shown in FIG. 11 is resonated at a constant resonance frequency. In this series resonant circuit, if the capacitance corresponding to ΔC shown in FIG. 12A increases or decreases, the voltage (V) or current of the resonant circuit shows a large change (voltage change ΔV). It can be acquired as the amount of change in capacitance.
[0101]
The increase in capacitance equivalent to ΔC shown in FIG. 12A is, for example, in the series resonance circuit shown in FIG. 11 when the metal thin film 11a approaches the coil 12a and a capacitance equivalent to the capacitor C ′ is added. Generated by being regarded. Then, the increase / decrease of the capacitance value of the entire series resonance circuit is read, and if there is a loss in the capacitance value, it is converted into the equivalent series circuit shown in FIG. It is assumed that the resistance equivalent to loss (Ru) is added in series as part of the resistance of the entire equivalent circuit, and the amount of change in the magnetic field is calculated. The point that the sheet resistance of the metal thin film 11a is calculated from the correlation between the obtained magnetic field change amount (ΔC corresponding to the capacity loss) and the 4-probe value is the same as the above description, and the description is omitted.
[0102]
(Frequency conversion method)
As still another example of the sheet resistance measuring method according to the present invention, a resistance corresponding to eddy current loss is added in series or in parallel to a series resonance circuit which is an equivalent circuit including a coil section. The amount of change in the magnetic field in the coil section is regarded as the amount of change in the resonance frequency of the series resonance circuit (frequency conversion method). Hereinafter, the basic principle of the frequency conversion method will be described with reference to FIGS. 13 (a) and 13 (b).
[0103]
As shown in FIG. 13B, a variable drive frequency self-excited oscillator (self-excited oscillator) 36 that outputs an AC voltage is used for a coil (coil portion) 12 a ′ having a self-inductance L. Note that a DC power source connected to the self-excited oscillator 36 is not shown. By using the self-excited oscillator 36, a change occurs in the resonance frequency when the metal thin film 11a approaches the coil 12a 'and when the metal thin film 11a does not approach the coil 12a', and the sheet resistance value of the metal thin film 11a is calculated from this difference.
[0104]
Specifically, as shown in FIG. 13A, the resonance frequency when the metal thin film 11a is not under the influence of the magnetic flux of the coil 12a 'is f.₀When the metal thin film 11a is under the influence of the magnetic flux of the coil 12a '(when approaching), the resonance frequency f₁And the amount of change in resonance frequency (Δf = f₀-F₁) Is obtained as the amount of change in the magnetic field in the coil 12a '. In FIG. 13B, it is assumed that a resistance Ru corresponding to eddy current loss is added in series to a series resonance circuit which is an equivalent circuit of the sheet resistance measuring device. The point that the sheet resistance of the metal thin film 11a is calculated from the correlation between the obtained magnetic field change amount (Δf) and the 4-probe value is the same as described above, and the description is omitted.
[0105]
By the way, the measurement of resistance at high frequency is often performed as measurement of the series effective resistance of the tuning circuit and the resonance impedance of the parallel tuning circuit. In general, as shown in FIGS. 14 and 15, an AC power supply (oscillator) 54, L (coil inductance), C (capacitor C)₁₃), R (internal resistance of the coil) series resonance circuit and loosely coupled, for example, variable capacitance (capacitor C₁₃), Or by changing the frequency of the AC power supply 54 and reading the current or voltage of the series resonance circuit with the ammeter 41 or the voltmeter 42, the effective resistance of the series resonance circuit at high frequency, the parallel resonance impedance, and the like are measured. be able to. The method of changing the variable capacitance is generally called the reactance change method, and the method of changing the frequency is generally called the frequency change method. In sheet resistance measurement that does not require much quickness such as off-line, particularly high accuracy measurement is performed. This is a method that can be realized.
[0106]
(Reactance change method)
The principle of the reactance changing method will be described in detail with reference to FIG. In the high frequency resistance measurement circuit shown in FIG.₁₃Capacitor C when tuning by changing the capacitance of₁₃, Read the ammeter 41 (or voltmeter 42)₀, Ir (Er), and capacitor C when detuned₁₃, Read the ammeter 41 (or voltmeter 42)₁・ C₂, I (E), and the internal resistance of the ammeter is R_AIf the frequency of the AC power supply 54 is f (constant), the series effective resistance R of the L, C, R series resonance circuit_XIs
[0107]
[Expression 4]

[0108]
And series effective resistance R_XCan be requested. And series effective resistance R_XResistance R corresponding to eddy current loss_uThis is applied to the sheet resistance calculation. The series effective resistance R_XCan be easily obtained from the equation (13) derived by the following process. In this case, the parallel resonance impedance Zr is
[0109]
[Equation 5]

[0110]
It becomes. Hereinafter, the series effective resistance R_XThe calculation method will be described in more detail with reference to FIG. 16 showing an equivalent circuit of the sheet resistance measuring device.
[0111]
An equivalent circuit of a sheet resistance measuring device to which the reactance change method is applied is, for example, as shown in FIG. 16B, an AC power supply 54, a coil 12a 'of inductance L, and an internal resistance R._ACurrent meter 41 and variable capacitance type capacitor C₁₃Are connected in series. During the sheet resistance measurement, the metal thin film 11a and the coil 12a 'are maintained in a state where a constant measurement height is maintained. That is, by assuming that a resistance Ru corresponding to an eddy current loss generated when the metal thin film 11a approaches the coil 12a ′ is added in series to the equivalent circuit, a sheet resistance measuring instrument at the time of measuring the sheet resistance is obtained. The equivalent circuit is obtained. The following description will be made assuming that the internal resistance of the coil 12a 'is zero.
[0112]
In the sheet resistance measuring instrument in a state where the metal thin film 11a is close to the coil 12a ', the coil 12a' is oscillated and the capacitor C₁₃When the resonance characteristic of the coil 12a ′ is adjusted by adjusting the capacitance of the coil 12a ′, a characteristic graph as shown in FIG. 16A is obtained. In this equivalent circuit, the current flowing through the ammeter 41 is expressed as Is and AC. The voltage of the power supply 54 is Vosc and the capacitor C₁₃If the electrostatic capacity of C is C and the angular frequency of the voltage is ω, the current Is is
[0113]
[Formula 6]

[0114]
It becomes.
[0115]
Then, as shown in the characteristic graph of FIG. 16A, the capacitor C when the coil 12a 'resonates.₁₃Capacitance is C₀Assuming that the value (Is) of the current flowing through the ammeter 41 is Ir, the capacitance is changed while keeping the metal thin film 11a and the coil 12a 'close to each other, and the capacitance C₀Up and down C₁, C₂If Is in both becomes I = Ir / √2 (effective current value), C₁, C₂Is equal in
[0116]
[Expression 7]

[0117]
The relationship is established. Further, the resonance of the coil 12a 'can be obtained.₀In this case, it is considered that reactance = 0. Therefore, from the above equation (7), the voltage Vosc of the AC power supply 54 is
[0118]
[Equation 8]

[0119]
It is guided. Here, in order to obtain the resistance Ru corresponding to the eddy current loss from the above equation (9), in the equation (9),
[0120]
[Equation 9]

[0121]
By replacing
[0122]
[Expression 10]

[0123]
Subsequently, in equation (10), by shifting 1 on the right side to the left side and taking the square root of both sides,
[0124]
## EQU11 ##

[0125]
As a result,
[0126]
[Expression 12]

[0127]
The relationship is guided. Furthermore, from equation (8):
[0128]
[Formula 13]

[0129]
Substituting this ωL into equation (12), R_AIs transferred to the right side,
[0130]
[Expression 14]

[0131]
Is obtained.
[0132]
[Expression 15]

[0133]
It becomes. That is, the electrostatic capacitance C at which the coil 12a 'resonates in a state where the metal thin film 11a and the coil 12a' are close to a certain distance.₀, And the capacitance C through which the current I flows₁, C₂By calculating the resistance value, the resistance value of the resistor Ru is calculated, and it is possible to obtain a more precise sheet resistance value of the metal thin film 11a from the correlation between the resistance value and the sheet resistance value.
[0134]
(Frequency change method)
Next, the principle of the frequency change method will be described in detail with reference to FIG. In the high-frequency resistance measurement circuit shown in FIG. 15B, the frequency is changed by keeping the primary current (voltage) flowing in the circuit including the AC power supply 54 constant, and is tuned, that is, at the frequency at the time of resonance (resonance frequency f0). The ammeter 41 (or voltmeter 42) reading (secondary current (secondary voltage) magnitude) Ir (Er), and the frequency when detuned (detuned frequency f1, f2) ammeter 41 (Or the voltmeter 42) is I (E), the series effective resistance R of the L, C, R series resonance circuit_XIs
[0135]
[Expression 16]

[0136]
And series effective resistance R_XCan be requested. And series effective resistance R_XResistance R corresponding to eddy current loss_uThis is applied to the sheet resistance calculation. The series effective resistance R_XSince the equation (14) for obtaining is easily derived from the equation (13) described above, a detailed description thereof will be omitted. Hereinafter, this measurement method will be described in more detail with reference to FIG. 17 showing an equivalent circuit of the sheet resistance measuring instrument.
[0137]
An equivalent circuit of the sheet resistance measuring device to which the frequency change method is applied is, for example, as shown in FIG. 17B, a frequency variable AC power supply 54, a coil 12a 'of inductance L, and an internal resistance R._ACurrent meter 41 and capacitor C₁₃Are connected in series. A voltmeter 55 is connected in parallel with the AC power supply 54.
[0138]
The metal thin film 11a and the coil 12a 'are maintained at a constant measurement height throughout the sheet resistance measurement. That is, by assuming that a resistance Ru corresponding to an eddy current loss generated when the metal thin film 11a approaches the coil 12a ′ is added in series to the equivalent circuit, a sheet resistance measuring instrument at the time of measuring the sheet resistance is obtained. The equivalent circuit is obtained. Note that the internal resistance of the coil 12a 'is assumed to be zero.
[0139]
In the sheet resistance measuring instrument in a state where the metal thin film 11a is close to the coil 12a ′, the coil 12a ′ is oscillated and the drive frequency of the AC power supply 54 is adjusted to obtain the resonance characteristics of the coil 12a ′. A characteristic graph as shown in a) is obtained. As shown in the characteristic graph, it is assumed that the drive frequency when the coil 12a ′ resonates is f0, and the current value (Is) flowing through the ammeter 41 is Ir, and then the metal thin film 11a and the coil 12a ′. If the drive frequency is changed while the two are close to each other, and the Is at the upper and lower f1, f2 of the drive frequency f0 becomes I, the relationship of the above equation (14) is established. That is, in a state where the metal thin film 11a and the coil 12a ′ are close to a certain distance, the resistance value of the resistor Ru is determined by determining the driving frequency f0 at which the coil 12a ′ resonates and the driving frequencies f1 and f2 through which the current I flows. It is possible to obtain a more accurate sheet resistance value of the metal thin film 11a from the calculated and correlation between the resistance value and the sheet resistance value.
[0140]
In the sheet resistance measuring method according to the present invention, as shown in FIG. 18, the glass substrate 11 on which the metal thin film is formed is taken out from the production line by the robot hand 58 and is stored in the offline inspection apparatus (sheet resistance measuring instrument) 57. It may be carried out by introducing. The offline inspection device 57 is provided with a HEPA (temperature management device for flowing a constant amount of airflow at a constant temperature) 56 as temperature control means for managing the inside of the clean room 57 a at a constant temperature. The stability of the measurement results can be increased by installing the sensor heads 12. Further, by using the HEPA 56, it is possible to prevent dust from adhering to the metal thin film on the glass substrate 11 and the sensor head 12, and to measure the sheet resistance more stably.
[0141]
Moreover, as a coil part concerning this invention, you may use what employ | adopted the ferrite core etc. as an axial center other than the thing of the said description, and what employ | adopted the litz wire as a metal wire which comprises a coil. According to these configurations, the metal thin film to be measured can be irradiated with stronger lines of magnetic force, and therefore, an eddy current having a magnitude that can be more reliably correlated with the sheet resistance value in the metal thin film. Can be generated. That is, it is possible to measure the sheet resistance more stably. When using a ferrite core, there is a general concern about the effect of temperature drift, but as in the present invention, a relatively low-temperature metal thin film carried out from a load lock chamber following the metal thin film formation portion. By targeting, this problem does not occur.
[0142]
【The invention's effect】
As described above, the sheet resistance measuring method according to the present invention is a thin film-shaped object to be measured for sheet resistance.Metal film unloaded from the load lock chamber following the formation sectionIrradiate the magnetic field lines of magnetic field from the coil part to one side of the above, the amount of change in the magnetic field according to the eddy current loss that occurs,The metal thin filmThis is a method of detecting the sheet resistance.
According to the above method, it is possible to detect a minute change amount of the magnetic field according to the eddy current loss stably and with high accuracy. That is, the sheet resistance of the metal thin film can be measured stably and with high accuracy.
[0143]
In the sheet resistance measuring method according to the present invention, on the premise of the above method, in the second step, a resistance corresponding to the eddy current loss is added in series to a series resonance circuit including the coil section. It is a method to consider that.
[0144]
In the sheet resistance measuring method according to the present invention, on the premise of the above method, in the second step, a resistance corresponding to the eddy current loss is added in parallel to the series resonance circuit including the coil section. It is a method that is considered to be done.
[0145]
The sheet resistance measuring method according to the present invention is a method for acquiring the amount of change in the magnetic field as the amount of change in impedance in the series resonant circuit, based on the above method.
[0146]
The sheet resistance measuring method according to the present invention is a method for obtaining the amount of change in the magnetic field as the amount of change in inductance in the series resonant circuit, based on the above method.
[0147]
The sheet resistance measuring method according to the present invention is a method for acquiring the amount of change in the magnetic field as the amount of change in capacitance in the series resonant circuit, based on the above method.
[0148]
The sheet resistance measurement method according to the present invention is a method for obtaining the change amount of the magnetic field as the change amount of the resonance frequency in the series resonance circuit on the premise of the above method.
[0149]
According to one of the above methods,The metal thin filmSince the sheet resistance can be measured in a non-contact manner,Metal thin filmThere is no risk of damage. In addition, the sheet resistance can be measured with a simple configuration as compared with the conventional double-sided eddy current method.
[0150]
The sheet resistance measuring method according to the present invention is further a method for obtaining the resistance value of the resistance corresponding to the eddy current loss by the reactance change method on the premise of the above method.
[0151]
The sheet resistance measuring method according to the present invention is a method for determining the resistance value of the resistance corresponding to the eddy current loss by the frequency change method on the premise of the above method.
[0152]
According to any of the above methods, for example, in sheet resistance measurement that does not require much quickness such as offline, an effect that it is possible to realize particularly high-precision measurement is achieved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a sheet resistance measuring device to which a measuring method according to the present invention is applied.
FIG. 2 is an explanatory diagram showing a main configuration of the sheet resistance measuring device shown in FIG.
FIG. 3 is an explanatory diagram for explaining an example of the principle of a measurement method according to the present invention.
FIG. 4 is an explanatory diagram showing an example of an equivalent circuit of a sheet resistance measuring device to which the measuring method according to the present invention is applied.
FIG. 5 is a graph showing the result of calculating the sheet resistance value of the gate film from the correlation with the four probe values using the sheet resistance measuring method of the present invention.
FIG. 6 is an explanatory diagram for explaining another example of the principle of the measuring method according to the present invention.
FIG. 7 is an explanatory diagram showing another example of an equivalent circuit of a sheet resistance measuring device to which the measuring method according to the present invention is applied.
FIG. 8 is an explanatory diagram for explaining still another example of the principle of the measurement method according to the present invention.
FIG. 9 is an explanatory view showing still another example of an equivalent circuit of a sheet resistance measuring device to which the measuring method according to the present invention is applied.
FIG. 10 is an explanatory view showing still another example of an equivalent circuit of a sheet resistance measuring device to which the measuring method according to the present invention is applied.
FIG. 11 is an explanatory diagram for explaining a state in which a metal thin film approaches a coil portion of a sheet resistance measuring device to which the measurement method according to the present invention is applied and a capacitance is added.
12A is an explanatory view showing still another example of the principle of the measurement method according to the present invention, and FIG. 12B is an example of an equivalent circuit of a sheet resistance measuring device to which the principle is applied. It is explanatory drawing for demonstrating.
13A is an explanatory view showing still another example of the principle of the measuring method according to the present invention, and FIG. 13B is an example of an equivalent circuit of a sheet resistance measuring device to which the principle is applied. It is explanatory drawing for demonstrating.
14A and 14B are explanatory views showing still another example of the principle of the measuring method according to the present invention.
FIGS. 15A and 15B are explanatory views showing still another example of the principle of the measuring method according to the present invention. FIGS.
FIGS. 16A and 16B are explanatory views of a sheet resistance measuring device to which the principle described in FIG. 14 is applied, in which FIG. 16A shows the principle and FIG. 16B shows the principle; An example of the equivalent circuit of the applied sheet resistance measuring device is shown.
FIGS. 17A and 17B are explanatory views of a sheet resistance measuring device to which the principle described in FIG. 15 is applied. FIG. 17A shows the principle, and FIG. 17B shows the principle. An example of an equivalent circuit of the applied sheet resistance measuring device is shown.
FIG. 18 is a perspective view showing a schematic configuration of an off-line inspection apparatus as a sheet resistance measuring device to which the measuring method according to the present invention is applied.
FIG. 19 is an explanatory diagram illustrating an electromagnetic induction phenomenon.
20 is an explanatory view showing an example in which the electromagnetic induction phenomenon described in FIG. 21 is applied to the sheet resistance measuring method according to the present invention.
FIG. 21 is a schematic perspective view showing a sheet resistance measuring method by a conventional four-probe method.
FIG. 22 is a schematic configuration diagram showing a sheet resistance measuring method by a conventional double-sided eddy current method.
[Explanation of symbols]
11a Metal thin film (Thin film object)
11b Eddy current
12 Sensor head
12a Coil (Coil part)
12a 'coil (coil part)
12b magnetic field
302 Coil (Coil part)
306 Metal thin film (Thin film object)
307 Eddy current
Ru resistance (resistance equivalent to eddy current loss)

Claims (9)

Using a sensor head comprising a coil section that generates a magnetic field, a method for measuring the sheet resistance of a thin film-like object to be measured,
The thin film-like object to be measured is a metal thin film carried out from the load lock chamber following the formation part of the thin film-like object to be measured, and
A step of installing the sensor head and the metal thin film under an airflow in which an airflow having a constant temperature flows in a certain amount;
To one side of the metal thin film is irradiated with magnetic field lines of the magnetic field from the coil portion, a first step of forming an eddy current due to the magnetic field to the metal thin film,
And a second step of detecting, as a sheet resistance of the metal thin film , a change amount of the magnetic field according to an eddy current loss caused by the formation of the eddy current. In the second step, it is considered that a resistance corresponding to the eddy current loss is added in series to a series resonance circuit including the coil section, and the change amount of the magnetic field is obtained. The sheet resistance measuring method according to claim 1. In the second step, it is assumed that a resistance corresponding to the eddy current loss is added in parallel to a series resonance circuit including the coil unit, and the amount of change in the magnetic field is acquired. The sheet resistance measuring method according to claim 1. The sheet resistance measurement method according to claim 2, wherein the amount of change in the magnetic field is acquired as an amount of change in impedance in the series resonance circuit. 4. The sheet resistance measuring method according to claim 2, wherein the amount of change in the magnetic field is acquired as an amount of change in inductance in the series resonance circuit. The sheet resistance measurement method according to claim 2, wherein the change amount of the magnetic field is acquired as a change amount of capacitance in the series resonance circuit. The sheet resistance measurement method according to claim 2, wherein the change amount of the magnetic field is acquired as a change amount of a resonance frequency in the series resonance circuit. 4. The sheet resistance measuring method according to claim 2, wherein the resistance value of the resistance corresponding to the eddy current loss is determined by a reactance change method. 4. The sheet resistance measuring method according to claim 2, wherein the resistance value of the resistance corresponding to the eddy current loss is determined by a frequency change method.

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