JP3593375B2

JP3593375B2 - Micro defect detection method and device

Info

Publication number: JP3593375B2
Application number: JP01948995A
Authority: JP
Inventors: 正孝芝; 洋森岡; 和彦永山; 俊明谷内; 哲也渡辺; 良治松永; 稔野口
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1995-02-07
Filing date: 1995-02-07
Publication date: 2004-11-24
Anticipated expiration: 2019-11-24
Also published as: JPH08210989A

Description

【０００１】
【産業上の利用分野】
本発明は、半導体ウエハ、プリント基板、ＴＦＴ液晶表示装置、あるいは磁気ディスク基板等の基板上に存在する微小異物等の微小欠陥を、高速に、且つ高感度に検出する微小欠陥検出方法及びその装置に関する。
【０００２】
【従来の技術】
年々微細化あるいは複雑化する半導体ウエハ、プリント基板、ＴＦＴ液晶表示装置、あるいは磁気ディスク基板等の基板の歩留まりを確保するためには、基板上に存在する微小異物等の微小欠陥を、高速に、且つ高感度に検出することが要求されている。
【０００３】
この基板上に存在する微小異物を、高速に、且つ高感度に検出する従来技術としては、例えば、特開昭５５−１４９８２９号公報（従来技術１）、特開昭５９−６５４２８号公報（従来技術２）および特開平６−１０２１８９号公報（従来技術３）が知られている。即ち、従来技術１においては、基板上の回路パターンと微小異物の分離をするために、直線偏光レーザを浅い角度で基板上に照射し、回路パターンのエッジと微小異物から発生する散乱光を基板上方に設けた検出光学系で集光した後、検光子を通して微小異物から発生する散乱光成分のみを検出器にて抽出する方法が示されている。また、従来技術２においては、基板上の回路パターンと微小異物の分離をするために、直線偏光レーザを浅い角度で基板に照射し、回路パターンのエッジと微小異物から発生する散乱光を基板上方に設けた検出光学系で集光した後、検出光学系における基板のフーリエ変換面に設けた空間フィルタにより、規則的な回路パターン形成角度あるいは配置を有する特定の回折光成分を遮光し、微小異物から発生する散乱光成分のみを検出器にて抽出する方法が示されている。また、従来技術３においては、回路パターンの存在しない鏡面状態の上に薄膜を形成した膜付きのウエハに対してレーザビームを傾斜した方向から照射した際、前記薄膜層の厚さや屈折率の違いにより反射率が大きく変化して薄膜上に存在する異物からの散乱光強度が大きく変動することに基づいて、前記反射率が所定値以上になるように膜付きのウエハに対して照射するレーザビームの入射角度を選択して膜付きのウエハ上に存在する異物からの散乱光強度を一定にして膜付きのウエハ上に存在する異物を安定して検出する方法が示されている。
【０００４】
【発明が解決しようとする課題】
半導体ウエハ、薄膜多層基板（プリント基板）、ＴＦＴ液晶表示装置、あるいは磁気ディスク基板等の基板上には、一般的に、微細な回路パターンあるいは情報記録用の溝等の規則的あるいは不規則的なパターンが形成されており、基板上に存在する異物、異物をこれらのパターンからいかに分離して抽出できるかが重要な開発課題になってきている。
【０００５】
上記従来技術１および２においては、半導体基板上に形成された回路パターンの如く幾何学的な形状の規則性による散乱光の乱れや回折に着目して異物からの散乱光を抽出しようと試みている。しかしながら、例えば、半導体の高集積化に伴い、より微小な異物等の微小欠陥を検出しようとする場合には、これだけでは十分な性能を達成できなくなってきている。即ち、半導体基板上に絶縁膜、保護膜、レジスト膜等の薄膜が形成されており、この単層あるいは多層の薄膜が形成された半導体基板の反射率や薄膜も含め半導体基板上の表面の微小凹凸（粗さ）等の違い又は変動に影響を受けることなく半導体基板上の表面に付着したより微小な異物等の微小欠陥を検出することが必要となってきている。上記従来技術３においては、薄膜が形成された半導体ミラーウエハからの反射率が所定の値以上になるように照射するレーザビームの照射角度を制御しようとしているが、実際のパターン付の半導体基板を考えると一枚の半導体基板においても、中心部と周辺部において薄膜の膜厚等が変動してしまうと共に１つのロット内の各半導体基板の間においても前記薄膜の膜厚等の変動が生じ、しかも前記薄膜の下に存在する回路パターンの形状も場所によって異なるため、照射するレーザビームの最適な照射角度を求めにくい状況になってしまい、安定して微小異物等の微小欠陥を検出することが難しくなる課題を有するものである。
このように、従来技術においては、基板上に形成された光を透過する薄膜の膜厚等の変動による基板からの反射率の変動や基板上の表面に存在する微小凹凸による影響を受けることなく、基板上に存在する微小異物等の微小欠陥を安定して確実に検出しようとする課題について考慮されていなかった。
【０００６】
本発明の目的は、上記従来技術の課題を解決すべく、半導体ウエハ、薄膜多層基板（プリント基板）、ＴＦＴ液晶表示装置、あるいは磁気ディスク基板等の基板の如く、光を透過する薄膜が形成された基板上に存在する０．３〜０．８μｍ或いはそれ以下の微小異物等の微小欠陥を、安定した高い検出感度で、且つ高速に検出できるようにして基板の歩留まりを向上するようにした微小欠陥検出方法及びその装置を提供することにある。
【０００７】
また、本発明の他の目的は、半導体基板の如く、回路パターンが形成され、光を透過する薄膜が形成され、更に微小凹凸の表面を有する半導体基板上に存在する０．３〜０．８μｍ或いはそれ以下の微小異物等の微小欠陥を、安定した高い検出感度で、且つ高速に検出できるようにした微小欠陥検出方法及びその装置を提供することにある。
【０００８】
【課題を解決するための手段】
本発明は、上記目的を達成するために、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに可干渉性を低減した指向性を有する光を斜め方向から照射し、前記基板上の微小欠陥から生じる散乱光を検出光学系で集光して光電変換手段で受光して該光電変換手段から得られる信号により前記基板上の微小欠陥を検出することを特徴とする微小欠陥検出方法である。
また本発明は、前記微小欠陥検出方法において、前記指向性を有する光は、レーザ光であることを特徴とする。
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに空間的に可干渉性を低減した指向性を有するレーザ光を斜め方向から照射し、前記基板上の微小欠陥から生じる散乱光を検出光学系で集光して光電変換手段で受光して該光電変換手段から得られる信号により前記基板上の微小欠陥を検出することを特徴とする微小欠陥検出方法である。
【０００９】
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに時間的に可干渉性を低減した指向性を有するレーザ光を斜め方向から照射し、前記基板上の微小欠陥から生じる散乱光を検出光学系で集光して光電変換手段で受光して該光電変換手段から得られる信号により前記基板上の微小欠陥を検出することを特徴とする微小欠陥検出方法である。
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに可干渉性を低減した指向性を有する光を斜め方向から照射し、前記基板上の微小欠陥および回路パターンのエッジから生じる散乱光を検出光学系で集光して前記回路パターンのエッジから生じる散乱光を遮光する遮光手段を通して得られる散乱光を光電変換手段で受光して該光電変換手段から得られる信号により前記基板上の微小欠陥を検出することを特徴とする微小欠陥検出方法である。
また本発明は、互いに可干渉性を低減した複数の光束を、基板面上に投影したときほぼ同一方向となるように互いに異なる傾斜した入射角度で基板面上の所望の個所に実効的にほぼ同時に照射し、前記基板上の微小欠陥から生じる散乱光を検出光学系で集光して光電変換手段で受光して該光電変換手段から得られる信号により前記微小欠陥を検出することを特徴とする微小欠陥検出方法である。
【００１０】
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに可干渉性を低減した指向性を有する光を斜め方向から照射する照射光学系と、該照射光学系で照射された光によって前記基板上の微小欠陥から生じる散乱光を集光して検出する検出光学系と、該検出光学系で集光して検出される散乱光を受光して信号に変換する光電変換手段とを備え、該光電変換手段から得られる信号により前記基板上の微小欠陥を検出するように構成したことを特徴とする微小欠陥検出装置である。
また本発明は、前記微小欠陥検出装置における前記照射光学系において、指向性を有する光を出射するレーザ光源を有することを特徴とする。
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに空間的に可干渉性を低減した指向性を有するレーザ光を斜め方向から照射する照射光学系と、該照射光学系で照射された光によって前記基板上の微小欠陥から生じる散乱光を集光して検出する検出光学系と、該検出光学系で集光して検出される散乱光を受光して信号に変換する光電変換手段とを備え、該光電変換手段から得られる信号により前記基板上の微小欠陥を検出するように構成したことを特徴とする微小欠陥検出装置である。
また本発明は、前記微小欠陥検出装置における前記照射光学系において、互いの光路長を異ならしめて互いに空間的に可干渉性を低減する光学系を備えたことを特徴とする。
【００１１】
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに時間的に可干渉性を低減した指向性を有するレーザ光を斜め方向から照射する照射光学系と、該照射光学系で照射された光によって前記基板上の微小欠陥から生じる散乱光を集光して検出する検出光学系と、該検出光学系で集光して検出される散乱光を受光して信号に変換する光電変換手段とを備え、該光電変換手段から得られる信号により前記基板上の微小欠陥を検出するように構成したことを特徴とする微小欠陥検出装置である。
また本発明は、前記微小欠陥検出装置において、前記光電変換手段を、ＴＤＩセンサで構成したことを特徴とする。
また本発明は、薄膜が形成された基板から得られる反射光の強度が平均化または平滑化されるように、前記基板上の所望の箇所に対して、互いに異なる入射角度を持ち、且つ互いに可干渉性を低減した指向性を有する光を斜め方向から照射する照射光学系と、該照射光学系で照射された光によって前記基板上の微小欠陥および回路パターンのエッジから生じる散乱光を集光して検出し、前記回路パターンのエッジから生じる散乱光を遮光する遮光手段を有する検出光学系と、該検出光学系で集光して検出される散乱光を受光して信号に変換する光電変換手段とを備え、該光電変換手段から得られる信号により前記基板上の微小欠陥を検出するように構成したことを特徴とする微小欠陥検出装置である。
【００１２】
また本発明は、互いに可干渉性を低減した複数の指向性を有する光束を、基板面上に投影したときほぼ同一方向となるように互いに異なる傾斜した入射角度で基板面上の所望の個所に実効的にほぼ同時に照射する照射光学系と、該照射光学系によって照射された光束により前記基板上の微小欠陥から生じる散乱光を集光して検出する検出光学系と、該検出光学系で集光して検出される散乱光を受光して信号に変換する光電変換手段とを備え、該光電変換手段から得られる信号により前記基板上の微小欠陥を検出するように構成したことを特徴とする微小欠陥検出装置である。
また本発明は、互いに干渉性を有しない複数の光束を、同一方向から異なる入射角度で基板に実効的に同時に照射し、この際に基板上のパターンや異物から発生する散乱光を偏光や空間フィルタを用いたパターン散乱光の遮断手段を介し異物からの散乱光のみを抽出して検出器で検出することを特徴とする微小欠陥検出方法及びその装置である。
また本発明は、前記微小欠陥検出方法及びその装置において、前記パターン散乱光の遮断手段に偏光を用いることを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、パターン散乱光の遮断手段に空間フィルタを用いることを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、対象とする基板が半導体ウエハ、プリント基板、ＴＦＴ液晶表示装置、あるいは磁気ディスク基板等であることを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、パターン散乱光の遮断手段である空間フィルタが、短冊上のパターンを平行、等間隔に並べた形状であることを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、互いに干渉性を有しない複数の光束を、単一のレーザ光源を分割後、互いの光路長を可干渉距離以上変化させて形成することを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、お互いに干渉性を有しない複数の光束を、複数の異なるレーザを設置して形成することを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、複数の異なるレーザの波長が、検出光学系の許容色収差量を満足する範囲で用いられることを特徴とする。また本発明は、前記微小欠陥検出方法及びその装置において、互いに干渉性を有しない複数の光束を、基板面に投影したときに同一方向となるような複数の異なる入射角度で基板に実効的に同時に照射するように、単一のレーザ光源からの光を、基板から離れた位置に集光させ、微小欠陥から発生する散乱光を検出光学系で集光させてＴＤＩ（ＴｉｍｅＤｅｌａｙｅｄＩｎｔｅｇｒａｔｉｏｎ）センサによって受光して検出することを特徴とする。
【００１３】
【作用】
年々微細化あるいは複雑化するＬＳＩ用若しくはＴＦＴ液晶表示用の半導体基板、コンピュータ用薄膜多層基板、または磁気ディスク用基板において、歩留まりを確保するために、０．３〜０．８μｍの微小な異物若しくは０．３μｍより小さな極微小な異物等の微小欠陥を、高速に、且つ高感度で検出することが必要になってきた。
一方、この微小な異物等の微小欠陥を検出する対象とする基板は、スパッタリングによってＡｌ等の配線層を形成した後、またはその後露光してエッチングを施した後（レジストが残った状態）、またはその後例えばＣＶＤでＳｉＯ_２等の絶縁膜を形成した後など様々な状態が存在することになる。このように、光を透過する絶縁層、保護層若しくはレジスト層が、基板上に形成された状態で、また、スパッタリングによってＡｌ等が成膜されて表面に微小な凹凸が存在する状態で、０．３〜０．８μｍの微小な異物等の微小欠陥を、高速に、且つ高感度で検出することが必要となる。
他方、このような状態において、基板上に存在する０．３〜０．８μｍの微小な異物等の微小欠陥を、高速に、且つ高感度で検出するためには、微小欠陥の表面積が微小になるため、微小異物等の微小欠陥に照射する強度を高くして、微小欠陥の表面側及び裏面側から照射してこの微小欠陥から発生する散乱光を多くしてその強度を高くする必要がある。そのためには、基板の表面に対してエネルギー密度の高い指向性を有するレーザ光を集光させて照射し、該照射によって微小欠陥の表面側に直接照射し、且つ上記の如く絶縁膜、保護膜、レジスト膜等の薄膜を有する基板から高い反射率で反射させた高い強度の反射光を上記微小欠陥の裏面側に照射することが必要となる。
【００１４】
ところが、上記薄膜の膜厚が、基板の周辺部と中心部で異なったりする場合が多く存在し、また基板の間若しくはロットの間または工程の間においても薄膜の膜厚が変動することになる。即ち、例えば、図１１に示すように、屈折率がｎ０〜ｎ３、膜厚がｄ１〜ｄ３からなる薄膜多層構造を有する基板１を対象として、０．３〜０．８μｍの微小な異物等の微小欠陥を検出する必要がある。このような対象基板１に対して、図１１に示すように、レーザ光４０を入射角度Ｔｈａで入射すると、境界面Ａ０〜Ａ３において屈折と反射を繰り返し、いわゆる多重干渉光として出射光（微小異物３の裏側から照射される光）４１が発生する。出射光４１と入射光４０との光強度の比が基板の反射率となるが、基板１上の微小異物３にレーザ光４０が照射されたときの散乱光強度を増大させるには、この基板１からの反射率を大きくする、即ち微小異物３の裏側から照射される多重干渉光（反射光、出射光）４１を増大させることが重要である。しかし、上記薄膜の厚さが変動すると、図１３に示すように、多重干渉光の強度（反射率）も、４４で示すように大幅に変動することになる。実際、多重干渉光の強度がほぼ最大を示す薄膜の膜厚と多重干渉光の強度がほぼ最小を示す薄膜の厚さとを有することが、例えば一枚の基板において存在し、そのため、０．３〜０．８μｍの微小な異物３の検出感度に大幅な違いが生じてしまうことになる。
そこで、本発明は、前記の如く構成することにより、微小異物等の微小欠陥に影響を与える基板からの多重干渉強度を、薄膜の膜厚変動に対して平滑化又は平均化してほぼ一定にし、しかも基板上に表面に存在する微小凹凸によって発生するスペックル干渉によるランダムな高輝度成分もを平滑化してスペックル模様を消去して、０．３〜０．８μｍ若しくはそれ以下の微小異物等の微小欠陥を高速度で、且つ安定して高感度で検出することができる。
【００１５】
【実施例】
本発明の実施例について、図面を用いて具体的に説明する。
【００１６】
まず、本発明に係る微小異物等の微小欠陥を検査する検査対象について説明する。即ち、検査対象とされる半導体ウエハ等の基板１は、図１１（回路パターン２は図示せず）及び図１２に示すように例えばＳｉ基板１ａ上に回路パターン２とＳｉＯ_２等の絶縁膜、保護膜等の光を透過する薄膜１ｂが形成されている。また上記半導体ウエハ等の基板１には、レジスト膜等の光を透過する薄膜が形成されている場合もある。このように、１枚の基板１において、回路パターン２との関係で、絶縁膜、保護膜等の光を透過する薄膜１ｂの厚さが０．０１〜０．５μｍ異なると共に、製造プロセスによって周辺部と中央部との間においても０．０１〜０．１μｍ程度のバラツキが存在することになる。また半導体ウエハ内で回路パターン２の構造が異なる際にも、０．０１〜０．１μｍ程度の薄膜の厚さ変動が生じる。また半導体ウエハ等の基板１においては、多層の配線構造を有している関係で、どの段階で薄膜上又は薄膜内において微小異物等の微小欠陥３を検査するかに応じて薄膜の層数においても変動するものである。一方、回路パターン２は、スパッタリング等により基板１の全面にＡｌ等の金属薄膜が形成され、その後、露光してエッチングを施すことによって基板１ａ上に形成される。従って、金属薄膜２の表面には、０．０１〜０．２μｍ或いはこれ以下の微小凹凸が存在する。そして、本発明においては、上記基板１上に形成された薄膜上又は薄膜内に存在する微小異物等の微小欠陥３を検査するものである。ところで、上記検査対象となる基板１としては、半導体ウエハ以外の、例えば計算機等に用いられる多層薄膜基板やプリント配線基板、またＴＦＴ液晶表示装置に用いられるＴＦＴ（ＴｈｉｎＦｉｌｍＴｒａｎｓｉｓｔｏｒ）基板、また磁気ディスク基板においても、同様な現象が生じており、本発明を適用することができる。
【００１７】
図１は、本発明に係る検査対象基板上に存在する微小異物等の微小欠陥を検査する装置における第１の実施例の構成を示したものである。即ち、この実施例では、高出力の半導体レーザ発振器の発振波長が約数ｎｍの幅を持つマルチ発振状態で作動することに着目し、その可干渉距離が極めて短い（たとえば０．２６ｍｍ以下）ため、同一の半導体レーザ発振器から出た、例えば８００ｎｍ近傍の近赤外のエネルギー密度の高い指向性をもったレーザ光を、光軸方向にずらして配置した多段ミラーにより可干渉距離以上の光路長差を持たせて、非干渉の複数の光束を作る方式である。
すなわち、高出力の半導体レーザ発振器５等から出た指向性を有するレーザ光を、コリメートレンズ６でＺ軸方向に関して平行光に変換した後、円筒レンズ７、レンズ８により、Ｚ軸方向には平行光束に、Ｙ軸方向にはＣ点に半導体レーザ発振器５の光源像が結像するように整形する。半導体レーザ発振器５の光の、光源を出てＡ面にいたるまでの光路長は、どこをとっても等しく、干渉性を有するが、多段ミラー９により分割された光束は、各々、可干渉距離以上の光路差をＢ面に到るまでに持つようになり、お互いの光束は非干渉になる。ＸＺ平面内で放物線を形成し、その焦点がＣ点を結びＹ軸に平行な直線となる放物ミラー１０によりＺ軸方向に集光すると、Ｃ点において集光する入射角度Ｔ１からＴｎまでの、お互いに非干渉で、しかも基板１に対して傾斜した入射角度の異なる複数の光束を形成することができる。上記のように、基板１上のＣ点に集光させる光にレーザ光のように指向性をもたせるのは、Ｃ点において入射するエネルギー密度を高めて、Ｃ点から反射して得られる多重干渉光の強度を高めて、表面積が小さい０．３〜０．８μｍ若しくはそれ以下の微小異物からの散乱光の強度を強めるためである。また、上記多段ミラー９と放物ミラー１０とを用いて、互いに可干渉距離以上の光路差をもたせて非干渉にしてＣ点に対して傾斜した入射角度の異なる複数の光束を形成したのは、、上記多段ミラー９と放物ミラー１０とも反射形の光学素子であるため、光の照射エネルギーの減衰を最小限に抑えてＣ点に照射するエネルギー密度を高めることができる。
【００１８】
回路パターン２のエッジや０．３〜０．８μｍ若しくはそれ以下の微小異物等の微小欠陥３から発生する散乱光４は、集光レンズ１１にて集められ、そのフーリエ変換面に設けられた空間フィルタ１３により、規則的な回路パターン２からの散乱光を低減した後に、結像レンズ１２によりリニアセンサ等の検出器１４により検出される。１５は検出器１４を搭載した基板である。
図２は、図１の光学系をＺ軸上方から展開したものである。半導体レーザ発振器５等から出た指向性を有するレーザ光は、焦点距離ｆ１のコリメートレンズ６、円筒レンズ７、焦点距離ｆ２のレンズ８、多段ミラー９、放物ミラー１０を介して基板１上に傾斜した方向から照射される。高出力の半導体レーザは、点光源ではなく、線状の光源であるため、光源の長さをＷ２としたとき、次に示す（数１）式で示す関係で拡大され、基板１上に長さＷ１の線状の照明光１８を形成する。
【００１９】
【数１】

【００２０】
ここで、半導体レーザ発振器５とコリメートレンズ６との距離Ｌ３は、ｆ１と等しく（Ｌ３＝ｆ１）、また、コリメートレンズ６とレンズ８との距離Ｌ２は、ｆ１＋ｆ２と等しく（Ｌ２＝ｆ１＋ｆ２）、さらに、レンズ８と基板との距離Ｌ１は、ｆ２にほぼ等しくとることにより、半導体レーザ発振器の光源像はテレセントリックに基板１に投影され、微小異物等が存在する際に発生する散乱光は、集光レンズ１１の後に置かれた空間フィルタ１３（図１）により基板１上の回路パターン２等と十分に分離された後に、結像レンズ１２を介してリニアセンサ等の検出器１４によって検出される。
図３は空間フィルタ１３の例を示したものである。図２のような線状照明の場合、基板１上の繰り返し回路パターン２のエッジからの回折光は図４に示すような原理で形成される。ここで、Ｓ１からＳ７は実空間の情報を、Ｆ１からＦ７はフーリエ空間の情報を示している。たとえば、基板１としてメモリ素子等の半導体ウエハを考えるとき、Ｓ７に示すように半導体ウエハ上にはメモリセル２０が複数個等間隔で配置されたセル群２１が、等間隔で複数個形成されている。このようなモデルを展開すると以下のようになる。すなわち、Ｓ７はセル群パターンＳ５が、Ｓ６のシャー関数で示される等間隔で配置している。セル群パターンＳ５は無限遠に広がるセルパターンＳ３に領域限定Ｓ４を施したものである。そして、無限遠に広がるセルパターンＳ３は、Ｓ１に示す単一のセルパターン２０が、Ｓ２のシャー関数で示される等間隔で配置されたものと考えられる。次に示す（数２）式はこれを示したものである。
【００２１】
【数２】

【００２２】
さて、Ｆ１からＦ７は実空間情報Ｓ１からＳ７の各々を光学的にフーリエ変換したものである。フーリエ変換の場合、実空間でのコンボリューション、掛け算は、フーリエ空間でそれぞれ掛け算、コンボリューションに変換される。従って、Ｆ７は（数２）式を用いて次に示す（数３）式の形で表現される。
【００２３】
【数３】

【００２４】
Ｆ７において、正反射光成分に相当する０次回折光成分２３が強力であり、図３の空間フィルタ１３においても、中央の０次光遮光のパターン２６は太くなっている。高次の回折光に関しては、メモリセル２０の間隔に依存する成分２４（矢印あり）とメモリセル群２１の間隔に依存する成分２５（矢印なし）があり、図１の集光レンズ１１の開口数（ＮＡ（ＮｕｍｅｒｉｃａｌＡｐｅｒｔｕｒｅ））に応じてメモリセル又はメモリセル群の間隔に依存する回折光を遮光するパターン２７が設けられる。
ところで、照明光はＸＹ平面内では常にＸ軸と平行に照射されるために、図１の様に、基板１への入射角度がＴ１からＴｎへと変化しても、その回折パターンのＹ軸方向の位置に変化がなく、回折パターンは常にＸ軸に平行に移動する。従って、図３において、回折光を遮光するパターン２６、２７をＸ軸と平行な短冊状にすれば、入射角度に依存しない空間フィルタのパターンを提供することができる。
【００２５】
一方、放物ミラー１０から基板１上のＣ点に集光照射された入射角度がＴ１〜Ｔｎの多数の光束の内、１つの光束（入射光）４０を、図１１に示すように、例えば屈折率がｎ０〜ｎ３、膜厚がｄ１〜ｄ３からなる薄膜構造を有する基板１に対して入射角度Ｔｈａで入射すると、境界面Ａ０〜Ａ３において屈折と反射を繰り返し、いわゆる多重干渉光としての反射光４１が発生する。上記入射光４０と反射光４１との光強度の比が基板の反射率となる。上記薄膜上又は薄膜内に存在する表面積が小さい０．３〜０．８μｍ若しくはそれ以下の微小異物からの散乱光の強度を強めるためには、前記に説明したように、微小異物の裏側から照射される光の強度となる多重干渉光としての反射光４１の強度
、即ち上記基板の反射率（入射光４０と反射光４１との光強度の比）を高めることが必要となる。一方、この基板の反射率（多重干渉光の強度）は、図１３に示すように基板１上に形成された光を透過する薄膜の厚さに応じて周期的に変動することになる。ところで、前記に説明したように、本発明に係る検査対象の基板１においては、薄膜の変動が１枚の基板においても生じ、また基板の種類に応じて変化することになり、そのため、図１３に示すように基板の反射率（多重干渉光の強度）に変動が生じ、微小異物の裏側から照射される光の強度に変動が生じて微小異物から発生する散乱光強度にも大幅な変動が生じ、検出感度が大幅に変動することになる。
【００２６】
他方、基板１に対して、集光照射する入射角度を変えると、図１３に示す基板の反射率（多重干渉光の強度）が薄膜の厚さに対して矢印で示すように移動することになる。そこで、図１に示すように、放物ミラー１０から基板１上のＣ点に、互いに非干渉な多数の光束を、互いに異なる入射角度Ｔ１〜Ｔｎで実効的に同時に集光照射することによって、基板１上に形成された薄膜から図１４に示すように薄膜の厚さに関係なくほぼ一定の反射率をもった合成された多重干渉光（反射光）が出射され、薄膜１ｂ上に存在する微小異物３に裏面側から照射され、微小異物３から薄膜１ｂの厚さ変動に関係なく、一定の散乱光を得ることができる。また上記の如く、微小異物３の表面側から直接集光照射された多数の光束によっても散乱光を得ることができる。図１４においては、入射角度Ｔ１，Ｔｋ，Ｔｎの各々の場合における薄膜の厚さに対する基板の反射率（多重干渉光の強度）を示す。しかし、上記の如く、これらの入射角度Ｔ１，Ｔｋ，Ｔｎをもった複数の光束が基板１上のＣ点に実行的に同時に集光照射されるため、図１５に示すように薄膜１ｂの厚さがＨａ，Ｈｂの各々の場合において、各入射角度Ｔ１，Ｔｋ，Ｔｎによって微小異物から発生する散乱光が合成されて平滑化または平均化されて集光レンズ１１に入射することになり、検出器１４により薄膜の厚さの変動に関係なくほぼ一定の出力信号５０を検出することができる。なお、入射角度Ｔｎで照射された光束によって、基板１の表面で正反射した多重干渉光が、集光レンズ１１の入射瞳に入らないようにすることが必要である。
このように、一枚の基板内で薄膜の厚さに変化があっても、また基板によって層数も含めて薄膜の厚さに変化があっても、常に薄膜から微小異物に対して照射される多重干渉光の強度をほぼ一定にすることができ、その結果微小異物から発生する散乱光もほぼ一定にすることができ、０．３〜０．８μｍ若しくはそれ以下の微小異物を安定して高信頼度で検出することができる。
【００２７】
また、基板１には、前記した通り、回路パターン２等を形成するために、スパッタリングによって成膜され、表面に微小凹凸を有するＡｌ等の金属薄膜が存在する。このように表面に微小凹凸（粗さ）を有するものに、指向性をもった光（レーザ光）を照射すると上記微小凹凸によって干渉によってスペックル模様が生じ、微小異物３からの散乱光成分が埋もれてしまうことになる。しかし、前記した通り、図１に示すように、放物ミラー１０から基板１上のＣ点に、互いに非干渉な多数の光束を、互いに異なる入射角度Ｔ１〜Ｔｎで実効的に同時に集光照射されるため、基板１上において表面に微小凹凸を有する金属薄膜等が存在して
、これによりスペックル（ランダムな高輝度成分）が発生しても、入射角度がＴ１〜Ｔｎのように異なることによりランダム性の高いスペックルによる明暗が互いに打ち消し合って平滑化されて、検出器１４によって最終的に図１６に示す平均的な信号（スペックル模様が消去された信号）５１が検出され、微小異物からの散乱光の安定な検出が可能となる。
【００２８】
図５は、本発明に係る検査対象基板上に存在する微小異物等の微小欠陥を検査する装置における第２の実施例の構成を示したものである。この第２の実施例は、図１に示す第１の実施例の変形例である。ここでは、高出力の半導体レーザ発振器５等から出たレーザ光を、コリメートレンズ６でＺ軸方向に関して平行光に変換した後、円筒レンズ７、レンズ８により、Ｚ軸方向には平行光束に、Ｙ軸方向にはＣ点に半導体レーザ発振器５の光源像がテレセントリックな関係で結像するように整形する。半導体レーザ発振器発振器５の光の、光源を出てＡ面にいたるまでの光路長は、どこをとっても等しく、干渉性を有するが、多段ミラー９により分割された光束は、各々、可干渉距離以上の光路差をＢ面に到るまでに持つようになり、お互いの光束は非干渉になる。
１６はＺ（またはＸ）軸方向にのみに光を集める、特に、球面収差を押さえるために非球面レンズあるいは回折レンズで構成されるアナモルフィッククな光学系であり、ミラー１７を経た後、Ｃ点において集光する入射角度Ｔ１からＴｎまでの、お互いに非干渉で、しかも基板に対する入射角度の異なる複数の光束を形成することができる。
回路パターン２のエッジや微小異物等の微小欠陥３から発生する散乱光４は、集光レンズ１１にて集められ、そのフーリエ変換面に設けられた空間フィルタ１３により、規則的な回路パターン２からの散乱光を低減した後に、結像レンズ１２によりリニアセンサ等の検出器１４により検出される。１５は検出器１４を搭載した基板である。
なお、第１及び第２の実施例において、検出光学系内に設置された空間フィルタ１３の代わりに、またはこの空間フィルタ１３に付け加える形で、検出光学系の光路途中に検光子（偏光板等）を設け、基板１上の回路パターン２のエッジからの散乱光成分を遮断してもよい。
【００２９】
図６は、本発明に係る検査対象基板上に存在する微小異物等の微小欠陥を検査する装置における第３の実施例の構成を示したものである。即ち、互いに非干渉の光束を基板１上に照射するために、ここでは、複数の半導体レーザ発振器５ａ〜５ｅを用いている。このように、半導体レーザ発振器を別々（独立）にすることにより、各半導体レーザ発振器５ａ〜５ｅから出力されたレーザ光束は、互いに非干渉となる。半導体レーザ発振器５ａ〜５ｅの各々から出力された各レーザ光束は、各コリメートレンズ６ａ〜６ｅでＺ軸方向に関して平行光に変換した後、各円筒レンズ３０ａ〜３０ｂにより、Ｚ軸方向には平行光束に、Ｙ軸方向にはＣ点に半導体レーザ発振器５の光源像がテレセントリックな関係で結像するように整形する。
【００３０】
１６は、Ｚ（またはＸ）軸方向にのみに光を集める、特に、球面収差を押さえるために非球面レンズあるいは回折レンズで構成されるアナモルフィッククな光学系であり、ミラー１７を経た後、Ｃ点において集光する入射角度Ｔ１からＴｎまでの、互いに非干渉で、しかも基板１に対する入射角度の異なる複数の光束を形成することができる。ここで、ミラー３１は、光路を４５°折り曲げるためのものである。
回路パターン２のエッジや微小異物等の微小欠陥３から発生する散乱光４は、集光レンズ１１にて集められ、そのフーリエ変換面に設けられた空間フィルタ１３により、規則的な回路パターン２からの散乱光を低減した後に、結像レンズ１２によりリニアセンサ等の検出器１４により検出される。１５は検出器１４を搭載した基板である。
【００３１】
図７は、本発明に係る検査対象基板上に存在する微小異物等の微小欠陥を検査する装置における第４の実施例の構成を示したものである。この第４の実施例では、アルゴンレーザ、ＹＡＧレーザ、ヘリウムネオンレーザを始めとする、ほとんどすべてのレーザが使用できる。すなわち、単一のレーザ発振器３２の光を分配器３３等で複数に分割し、これを光ファイバ３４ａ〜３４ｅ等を用いて導く。この際、光ファイバの長さの違いを互いに可干渉距離以上になるように変える等して、各々の光ファイバからでてくる光が非干渉になるようにしている。光ファイバをでた光は一般に点光源として扱えるため、コリメートレンズ６ａ〜６ｅにより平行光に変えた後、Ｚ（またはＸ）軸方向にのみ１６のアナモルフィックな光学系により球面収差を押さえた形でＣ点に集光させる。
【００３２】
また、検出光学系の許容色収差性能を満足するならば、たとえばアルゴンレーザとＹＡＧレーザの組み合わせといった構成も考えられる。
図８は、本発明に係る検査対象基板上に存在する微小異物等の微小欠陥を検査する装置における第５の実施例の構成を示したものである。
第１〜第４の実施例は、レーザの発振波長という光学的な非干渉性（空間的インコヒーレント性）を用いた例であったのに対し、第５の実施例では、ＴＤＩ（ＴｉｍｅＤｅｌａｙｅｄＩｎｔｅｇｒａｔｉｏｎ）センサの特性を活かした時間的な非干渉性（時間的なインコヒーレント性）を用いている。
【００３３】
ＴＤＩセンサは、図９と図１０に示すように、ラインセンサがｎ段形成されたものである。センサから吐き出される情報量であるラインレートは、ラインセンサと同等であるが、ラインレートｄｔ毎に、蓄積された電荷がライン３６−１から３６−２・・・・・と順次転送されていき、基板１を搬送するステージ（図示せず）の送り速度を、ラインレートと同期させることにより、たとえば、微小異物３からの散乱光３７はライン３６−ｎに到るまでの長時間にわたって蓄積されることになり、高感度な検出が可能となる。このセンサでは、基本的に微小異物の像がライン３６−１から３６−ｎに到るまでの散乱光強度の総和を検出することになるが、ライン各々に到達する基板の同一地点からの散乱光は、時間的に全くインコヒーレントである。
【００３４】
そこで、図８に示すようにＴＤＩセンサ３５の共約面である基板面１から離れたところＰに半導体レーザ発振器５等の光を集光させると、ＴＤＩセンサ３５の共約面上の点Ｑ１〜Ｑ３には、照射角度ＴｂからＴａの幅広い角度で光が照射される。Ｑ１〜Ｑ３の間に存在するＴＤＩセンサ３５のライン３６の位置は各々異なり、干渉性を回避することができるために、入射角度が連続的に変化する非干渉な照明での検出と同様の性能を得ることができる。なお、６はコリメートレンズ、１６は球面収差の小さいアナモルフィックな光学素子である。
【００３５】
以上説明したように、第２〜第５の実施例においても、第１の実施例と同様な作用効果を得ることができる。
なお、非干渉な多数のレーザ光束を形成する方法としては、上記実施例以外にも、例えば、図１７に示すように、照明光路中に回転等の運動をする透明なガラス板２８を挿入してレーザ光束を変調させ、この変調した光を集光レンズ８で非干渉な多数のレーザ光束を得ることもできる。
本発明の実施例では、微小異物等の微小欠陥３からの散乱光の検出にリニアセンサを用いた例を示したが、光電子増倍管等のポイントセンサを用いる場合にも、照明光をスリット状からスポット状に変化させ、スポット走査系を付加することが必要となるものの基本的にはほぼ同一の光学系を用いることができる。
【００３６】
また、斜方照明上方検出（１１〜１４からなる検出光学系の光軸を基板１の表面に対してほぼ垂直にした場合）の光学系を対象に実施例を示したが、半導体ウエハ、プリント基板、ＴＦＴ液晶表示装置、あるいは磁気ディスク基板等、様々な対象の検査を考えた場合、斜方照明側方検出（１１〜１４からなる検出光学系の光軸を基板１の表面を基準にして照明光学系の光軸に対してほぼ直角なＹ軸方向に傾斜させた場合である。この場合も、基板１の表面からの正反射光は、集光レンズ１１に入射されない。）、あるいは斜方照明裏面検出、あるいはこれらの組み合わせも考えられる。
【００３７】
【発明の効果】
本発明によれば、半導体基板、多層薄膜基板（プリント基板）、ＴＦＴ基板または磁気ディスク基板等のように基板上に形成された光を透過する薄膜の厚さが基板間あるいは基板内で異なって基板の反射率が変化するような場合や、基板上に形成される金属薄膜等のように表面に微小凹凸（粗さ）を有する場合において、表面積の小さな０．３〜０．８μｍあるいはそれ以下の微小異物等の微小欠陥から生じる散乱光の変動を少なくし、その強度をできるだけ大きくして、上記基板上に存在する０．３〜０．８μｍあるいはそれ以下の微小欠陥を高感度で、且つ高信頼度で検出して、基板の製造工程における歩留まりを向上させることができる効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る微小欠陥検出装置における第１の実施例を示す構成図である。
【図２】図１に示す光学系をＺ軸方向から臨んで展開した照明光学系を中心とする光路展開図である。
【図３】図１に示す装置において用いられている空間フィルタの形状を示す図である。
【図４】図３に示す空間フィルタの作用を説明するための図である。
【図５】本発明に係る微小欠陥検出装置における第２の実施例を示す構成図である。
【図６】本発明に係る微小欠陥検出装置における第３の実施例を示す構成図である。
【図７】本発明に係る微小欠陥検出装置における第４の実施例を示す構成図である。
【図８】本発明に係る微小欠陥検出装置における第５の実施例を示す構成図である。
【図９】ＴＤＩセンサの動作を説明するために、ｔ＝ｔ０における状態を示す図である。
【図１０】ＴＤＩセンサの動作を説明するために、ｔ＝ｔ０＋ｄｔにおける状態を示す図である。
【図１１】薄膜構造を有する基板において生じる多重干渉について説明するための図である。
【図１２】本発明の検査対象となる基板の一例である薄膜の厚さに変化が見受けられる半導体ウエハの一部分の断面を示す図である。
【図１３】基板上に対して集光照射する光束の入射角を変えた場合の薄膜の厚さと基板の反射率（多重干渉光の強度）との関係を示す図である。
【図１４】基板上に対して各々入射角度Ｔ１，Ｔｋ，Ｔｎをもった複数の光束を実効的に同時に集光照射する場合の薄膜の厚さと基板の反射率（多重干渉光の強度）との関係を示す図である。
【図１５】図１５に示す内容を検出器で検出される検出波形で説明する図である。
【図１６】基板上に形成されたＡｌ等の金属薄膜上の微小凹凸によって生じるスペックル模様が消去されることを検出器で検出される検出波形で説明する図である。
【図１７】本発明に係る微小欠陥検出装置において第１〜第５の実施例と異なる構成を示す図である。
【符号の説明】
１…基板、１ａ…Ｓｉ基板、１ｂ…薄膜（絶縁膜、保護膜、レジスト膜）
２…回路パターン、３…微小異物（微小欠陥）、５…半導体レーザ発振器
６…コリメートレンズ、７…円筒レンズ、８…レンズ、９…多段ミラー
１０…放物ミラー、１１…集光レンズ、１２…結像レンズ
１３…空間フィルタ、１４…検出器、１６…アナモルフィッククな光学系
１７…ミラー、３５…ＴＤＩセンサ[0001]
[Industrial applications]
The present invention provides a method and a device for detecting a minute defect such as a minute foreign matter present on a substrate such as a semiconductor wafer, a printed substrate, a TFT liquid crystal display device, or a magnetic disk substrate at high speed and with high sensitivity. About.
[0002]
[Prior art]
In order to secure the yield of substrates such as semiconductor wafers, printed substrates, TFT liquid crystal display devices, and magnetic disk substrates, which are becoming finer and more complex year by year, minute defects such as minute foreign matter existing on the substrates are rapidly removed. In addition, high-sensitivity detection is required.
[0003]
Conventional techniques for detecting minute foreign substances present on the substrate at high speed and with high sensitivity include, for example, JP-A-55-149829 (Prior Art 1) and JP-A-59-65428 (Prior Art). Japanese Patent Application Laid-Open No. 6-102189 (prior art 3) is known. That is, in the prior art 1, in order to separate the circuit pattern on the substrate from the minute foreign matter, a linearly polarized laser is irradiated onto the substrate at a shallow angle to scatter light generated from the edge of the circuit pattern and the minute foreign matter. A method is shown in which only a scattered light component generated from a minute foreign substance is extracted by a detector through an analyzer after condensing by a detection optical system provided above. In the prior art 2, in order to separate the circuit pattern on the substrate from the minute foreign matter, the substrate is irradiated with a linearly polarized laser at a small angle to scatter light generated from the edge of the circuit pattern and the minute foreign matter. After the light is collected by the detection optical system provided in the optical system, a specific diffracted light component having a regular circuit pattern forming angle or arrangement is shielded by a spatial filter provided on the Fourier transform surface of the substrate in the detection optical system. A method is shown in which only a scattered light component generated from the light is extracted by a detector. Further, in the prior art 3, when a laser beam is irradiated from a tilted direction on a wafer having a thin film formed on a mirror surface where no circuit pattern exists, the difference in the thickness and the refractive index of the thin film layer may be different. A laser beam that irradiates a film-coated wafer such that the reflectance is greater than or equal to a predetermined value based on the fact that the reflectance greatly changes and the intensity of scattered light from foreign matter present on the thin film greatly varies. A method for stably detecting a foreign substance present on a film-bearing wafer by selecting an incident angle of and making the intensity of scattered light from the foreign substance present on the film-bearing wafer constant.
[0004]
[Problems to be solved by the invention]
On a substrate such as a semiconductor wafer, a thin film multilayer substrate (printed substrate), a TFT liquid crystal display device, or a magnetic disk substrate, generally, a regular or irregular pattern such as a fine circuit pattern or a groove for recording information is formed. Patterns are formed, and foreign matter existing on the substrate, and how the foreign matter can be separated and extracted from these patterns has become an important development issue.
[0005]
In the above

prior arts

1 and 2, an attempt was made to extract scattered light from a foreign substance by focusing on turbulence and diffraction of scattered light due to regularity of a geometric shape such as a circuit pattern formed on a semiconductor substrate. I have. However, for example, when it is attempted to detect a minute defect such as a minute foreign substance with the high integration of a semiconductor, sufficient performance cannot be achieved by this alone. That is, a thin film such as an insulating film, a protective film, and a resist film is formed on a semiconductor substrate, and the reflectance and the thin film on the surface of the semiconductor substrate including the single-layer or multi-layer thin film are formed. It has become necessary to detect fine defects such as finer foreign substances attached to the surface of a semiconductor substrate without being affected by differences or fluctuations in irregularities (roughness) or the like. In the above prior art 3, the irradiation angle of the laser beam to be irradiated is controlled so that the reflectance from the semiconductor mirror wafer on which the thin film is formed becomes a predetermined value or more. Considering that, even in a single semiconductor substrate, the film thickness of the thin film fluctuates between the central portion and the peripheral portion, and the film thickness of the thin film fluctuates between the semiconductor substrates in one lot. Moreover, since the shape of the circuit pattern present under the thin film also varies depending on the location, it is difficult to find the optimum irradiation angle of the laser beam to be irradiated, and it is possible to stably detect minute defects such as minute foreign matter. It has a difficult task.
As described above, in the related art, without being affected by the fluctuation of the reflectance from the substrate due to the fluctuation of the film thickness of the thin film that transmits light formed on the substrate and the minute unevenness existing on the surface on the substrate. However, no consideration has been given to the problem of stably and surely detecting minute defects such as minute foreign substances present on a substrate.
[0006]
An object of the present invention is to form a thin film that transmits light, such as a substrate such as a semiconductor wafer, a thin-film multilayer substrate (printed substrate), a TFT liquid crystal display device, or a magnetic disk substrate, in order to solve the above-mentioned problems of the prior art. Micro defects such as 0.3 to 0.8 μm or less fine foreign substances present on the substrate with stable high detection sensitivity and high speed to improve the substrate yield. It is an object of the present invention to provide a defect detection method and its device.
[0007]
Further, another object of the present invention is to provide a semiconductor substrate having a circuit pattern formed thereon, a light-transmitting thin film formed thereon, and a semiconductor substrate having a fine uneven surface having a thickness of 0.3 to 0.8 μm. Another object of the present invention is to provide a small defect detection method and device capable of detecting a small defect such as a minute foreign substance having a size smaller than that at a stable and high detection sensitivity and at a high speed.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a method of manufacturing a light-emitting device, comprising: With an angle, and irradiating obliquely with light having directivity with reduced coherence with each other, scattered light generated from minute defects on the substrate is collected by the detection optical system and received by the photoelectric conversion means. A minute defect detection method characterized by detecting a minute defect on the substrate based on a signal obtained from the photoelectric conversion means.
Further, according to the present invention, in the minute defect detection method, the light having directivity is a laser beam.
In addition, the present invention has different incident angles with respect to a desired portion on the substrate, and has a space between each other so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. A laser beam having directivity with reduced coherence is radiated obliquely, scattered light generated from minute defects on the substrate is condensed by a detection optical system, and received by photoelectric conversion means and received by the photoelectric conversion means. A minute defect detection method characterized by detecting a minute defect on the substrate by a signal obtained from the means.
[0009]
In addition, the present invention has different incident angles with respect to a desired portion on the substrate, and has a different time from each other so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. A laser beam having directivity with reduced coherence is radiated obliquely, scattered light generated from minute defects on the substrate is condensed by a detection optical system, and received by photoelectric conversion means and received by the photoelectric conversion means. A minute defect detection method characterized by detecting a minute defect on the substrate by a signal obtained from the means.
In addition, the present invention has different incident angles with respect to a desired portion on the substrate and allows different angles so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. Irradiation is performed from diagonal direction with light having directivity with reduced coherence, and scattered light generated from the edges of the circuit pattern by condensing scattered light generated from minute defects on the substrate and edges of the circuit pattern by a detection optical system. A scattered light obtained through a light shielding means for shielding light from the substrate, and a minute defect on the substrate is detected by a signal obtained from the photoelectric conversion means.
In addition, the present invention provides a method in which a plurality of luminous fluxes having reduced coherence with each other are projected substantially at a desired position on a substrate surface at different incident angles different from each other so as to be substantially in the same direction when projected onto the substrate surface. Simultaneously irradiating, scattered light generated from minute defects on the substrate is collected by a detection optical system, received by photoelectric conversion means, and the minute defects are detected by a signal obtained from the photoelectric conversion means. This is a minute defect detection method.
[0010]
In addition, the present invention has different incident angles with respect to a desired portion on the substrate and allows different angles so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. An irradiation optical system that irradiates light having a directivity with reduced coherence from an oblique direction, and a detection optics that collects and detects scattered light generated from minute defects on the substrate by the light irradiated by the irradiation optical system. And a photoelectric conversion means for receiving scattered light condensed and detected by the detection optical system and converting the scattered light into a signal, and detecting a minute defect on the substrate by a signal obtained from the photoelectric conversion means. A minute defect detecting device characterized by having such a configuration.
Further, the invention is characterized in that the irradiation optical system in the minute defect detection device includes a laser light source that emits light having directivity.
In addition, the present invention has different incident angles with respect to a desired portion on the substrate, and has a space between each other so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. An irradiation optical system for irradiating a laser beam having directivity with reduced coherence from an oblique direction, and condensing scattered light generated from minute defects on the substrate by the light irradiated by the irradiation optical system. A detection optical system for detecting, and photoelectric conversion means for receiving scattered light condensed and detected by the detection optical system and converting the scattered light into a signal; A minute defect detection device configured to detect a defect.
Further, the present invention is characterized in that the irradiation optical system in the micro-defect detection device includes an optical system that makes the optical path lengths different from each other and spatially reduces coherence.
[0011]
In addition, the present invention has different incident angles with respect to a desired portion on the substrate, and has a different time from each other so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. An irradiation optical system for irradiating a laser beam having directivity with reduced coherence from an oblique direction, and condensing scattered light generated from minute defects on the substrate by the light irradiated by the irradiation optical system. A detection optical system for detecting, and photoelectric conversion means for receiving scattered light condensed and detected by the detection optical system and converting the scattered light into a signal; A minute defect detection device configured to detect a defect.
Further, the present invention is characterized in that in the minute defect detection device, the photoelectric conversion means is constituted by a TDI sensor.
In addition, the present invention has different incident angles with respect to a desired portion on the substrate and allows different angles so that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. An irradiation optical system that irradiates light having a directivity with reduced coherence from an oblique direction, and condenses scattered light generated from the edge of a microdefect and a circuit pattern on the substrate by the light irradiated by the irradiation optical system. Optical system having a light shielding means for detecting and detecting the scattered light generated from the edge of the circuit pattern, and a photoelectric conversion means for receiving the scattered light collected and detected by the detection optical system and converting the scattered light into a signal Wherein a minute defect on the substrate is detected based on a signal obtained from the photoelectric conversion means.
[0012]
Also, the present invention provides a method for projecting light beams having a plurality of directivities, each having reduced coherence, at desired positions on the substrate surface at different incident angles different from each other so as to be substantially in the same direction when projected onto the substrate surface. An irradiation optical system that effectively irradiates the light at substantially the same time; a detection optical system that collects and detects scattered light generated from minute defects on the substrate by a light beam irradiated by the irradiation optical system; Photoelectric conversion means for receiving the scattered light detected by light and converting the scattered light into a signal, wherein a minute defect on the substrate is detected by a signal obtained from the photoelectric conversion means. This is a minute defect detection device.
Further, the present invention effectively irradiates the substrate with a plurality of light beams having no coherence from each other at different incident angles from the same direction, and at this time, scattered light generated from a pattern or foreign matter on the substrate is polarized or spatially. A method and apparatus for detecting a minute defect, wherein only a scattered light from a foreign substance is extracted through a pattern scattered light blocking means using a filter and detected by a detector.
Further, according to the present invention, in the method and the apparatus for detecting a minute defect, a polarized light is used as a blocking means of the pattern scattered light. According to the present invention, in the method and the apparatus for detecting a minute defect, a spatial filter is used as means for blocking pattern scattered light. Further, the present invention is characterized in that in the method and the device for detecting a minute defect, a target substrate is a semiconductor wafer, a printed substrate, a TFT liquid crystal display device, a magnetic disk substrate, or the like. Further, according to the present invention, in the method and the apparatus for detecting a minute defect, the spatial filter, which is means for blocking the pattern scattered light, has a shape in which the patterns on the strip are arranged in parallel at equal intervals. Further, according to the present invention, in the method and the apparatus for detecting a minute defect, a plurality of light beams having no coherence are formed by dividing a single laser light source and then changing an optical path length of each other by a coherent distance or more. It is characterized by. Further, the present invention is characterized in that, in the above-described method and apparatus for detecting a minute defect, a plurality of light beams having no coherence are formed by installing a plurality of different lasers. The present invention is also characterized in that in the method and the apparatus for detecting a minute defect, the wavelengths of a plurality of different lasers are used within a range that satisfies an allowable chromatic aberration amount of the detection optical system. Further, the present invention provides the method and the apparatus for detecting a microdefect, wherein a plurality of light beams having no coherence with each other are projected onto the substrate at a plurality of different incident angles so as to be in the same direction when projected onto the substrate surface. Light from a single laser light source is condensed at a position distant from the substrate so as to be irradiated simultaneously, and scattered light generated from minute defects is condensed by a detection optical system, and the light is condensed by a TDI (Time Delayed Integration) sensor. It is characterized by receiving and detecting.
[0013]
[Action]
In a semiconductor substrate for LSI or TFT liquid crystal display, a thin film multilayer substrate for a computer, or a substrate for a magnetic disk, which is becoming finer or more complicated year by year, in order to secure a yield, fine foreign substances of 0.3 to 0.8 μm or It has become necessary to detect very small defects such as extremely small foreign substances smaller than 0.3 μm at high speed and with high sensitivity.
On the other hand, the substrate on which the minute defect such as a minute foreign substance is to be detected is formed after forming a wiring layer such as Al by sputtering, or after exposure and etching (resist remains), or Then, for example, by CVD using SiO ₂ Various states exist, for example, after forming an insulating film such as. As described above, in a state where an insulating layer, a protective layer, or a resist layer that transmits light is formed on a substrate, or in a state in which Al or the like is formed by sputtering and fine irregularities exist on the surface, 0 It is necessary to detect minute defects such as minute foreign substances having a size of 0.3 to 0.8 μm at high speed and with high sensitivity.
On the other hand, in such a state, in order to detect a minute defect such as a minute foreign substance of 0.3 to 0.8 μm existing on the substrate at high speed and with high sensitivity, the surface area of the minute defect is extremely small. Therefore, it is necessary to increase the intensity of irradiating a minute defect such as a minute foreign substance, and irradiate from the front side and the back side of the minute defect to increase the scattered light generated from the minute defect to increase the intensity. . For this purpose, a laser beam having a high directivity with a high energy density is condensed and irradiated on the surface of the substrate, and the surface is directly irradiated on the surface side of the minute defect by the irradiation. In addition, it is necessary to irradiate high intensity reflected light reflected at a high reflectance from a substrate having a thin film such as a resist film on the back surface side of the minute defect.
[0014]
However, there are many cases where the thickness of the thin film is different between the peripheral portion and the central portion of the substrate, and the thickness of the thin film varies between substrates, between lots, or even between processes. . That is, for example, as shown in FIG. 11, for a substrate 1 having a thin film multilayer structure having a refractive index of n0 to n3 and a film thickness of d1 to d3, a fine foreign substance of 0.3 to 0.8 μm is removed. It is necessary to detect minute defects. As shown in FIG. 11, when the laser beam 40 is incident on such a target substrate 1 at an incident angle Tha, refraction and reflection are repeated at the boundary surfaces A0 to A3, and the emission light (fine foreign matter) is generated as so-called multiple interference light. 3) is generated. The ratio of the light intensity between the outgoing light 41 and the incident light 40 is the reflectance of the substrate. To increase the scattered light intensity when the laser beam 40 is applied to the minute foreign matter 3 on the substrate 1, It is important to increase the reflectance from 1, that is, to increase the multiple interference light (reflected light, emitted light) 41 emitted from the back side of the minute foreign matter 3. However, when the thickness of the thin film fluctuates, the intensity (reflectance) of the multiple interference light also fluctuates greatly as shown by 44 as shown in FIG. In fact, the thickness of the thin film in which the intensity of the multiple interference light is almost maximum and the thickness of the thin film in which the intensity of the multiple interference light is almost minimum are present in, for example, one substrate. A significant difference will occur in the detection sensitivity of the minute foreign matter 3 of about 0.8 μm.
Therefore, the present invention, by configuring as described above, the multiple interference intensity from the substrate that affects minute defects such as minute foreign matter, is smoothed or averaged with respect to the variation in the film thickness of the thin film to be substantially constant, Moreover, random high-luminance components due to speckle interference generated by minute irregularities existing on the surface of the substrate are also smoothed to eliminate the speckle pattern, and fine foreign substances of 0.3 to 0.8 μm or less are removed. Micro defects can be detected at high speed and stably with high sensitivity.
[0015]
【Example】
Embodiments of the present invention will be specifically described with reference to the drawings.
[0016]
First, an inspection target for inspecting a minute defect such as a minute foreign substance according to the present invention will be described. That is, as shown in FIG. 11 (circuit pattern 2 is not shown) and FIG. 12, the circuit pattern 2 and the SiO 2 ₂ A thin film 1b that transmits light, such as an insulating film or a protective film, is formed. The substrate 1 such as the semiconductor wafer may be formed with a light-transmitting thin film such as a resist film. As described above, in one substrate 1, the thickness of the light-transmitting thin film 1b such as an insulating film and a protective film differs by 0.01 to 0.5 [mu] m in relation to the circuit pattern 2 and the peripheral portions are changed by the manufacturing process. A variation of about 0.01 to 0.1 μm exists between the portion and the central portion. Also, when the structure of the circuit pattern 2 is different in the semiconductor wafer, the thickness of the thin film varies about 0.01 to 0.1 μm. Further, since the substrate 1 such as a semiconductor wafer has a multi-layer wiring structure, the number of layers of the thin film depends on the stage at which the minute defect 3 such as a minute foreign substance is inspected on or in the thin film. Also fluctuates. On the other hand, the circuit pattern 2 is formed on the substrate 1a by forming a metal thin film of Al or the like on the entire surface of the substrate 1 by sputtering or the like, and then performing exposure and etching. Therefore, fine irregularities of 0.01 to 0.2 μm or less exist on the surface of the metal thin film 2. In the present invention, a minute defect 3 such as a minute foreign substance existing on or in the thin film formed on the substrate 1 is inspected. By the way, as the substrate 1 to be inspected, other than a semiconductor wafer, for example, a multilayer thin film substrate or a printed wiring board used for a computer or the like, a TFT (Thin Film Transistor) substrate used for a TFT liquid crystal display device, or a magnetic disk A similar phenomenon occurs in the substrate, and the present invention can be applied.
[0017]
FIG. 1 shows a configuration of a first embodiment of an apparatus for inspecting a minute defect such as a minute foreign substance present on a substrate to be inspected according to the present invention. That is, this embodiment focuses on operating in a multi-oscillation state in which the oscillation wavelength of a high-output semiconductor laser oscillator has a width of about several nm, and its coherence length is extremely short (eg, 0.26 mm or less). A laser beam emitted from the same semiconductor laser oscillator and having a directivity of, for example, near-800 nm and having a high near-infrared energy density, having an optical path length difference larger than the coherent distance by a multi-stage mirror displaced in the optical axis direction. To generate a plurality of non-interfering light beams.
That is, a laser beam having directivity emitted from the high-power semiconductor laser oscillator 5 or the like is converted into parallel light in the Z-axis direction by the collimating lens 6, and then parallelized in the Z-axis direction by the

cylindrical lenses

7 and 8. The light beam is shaped so that the light source image of the semiconductor laser oscillator 5 is formed at the point C in the Y-axis direction. The optical path length of the light of the semiconductor laser oscillator 5 from the light source to the surface A is equal everywhere and has coherence, but the light beams split by the multi-stage mirror 9 are each longer than the coherent distance. The optical path difference is maintained before reaching the surface B, and the light fluxes of the two do not interfere with each other. When a parabola is formed in the XZ plane and its focus is condensed in the Z-axis direction by the parabolic mirror 10 connecting the point C and forming a straight line parallel to the Y-axis, the light is converged at the point C from the incident angles T1 to Tn. It is possible to form a plurality of light beams having different incident angles that are not interference with each other and that are inclined with respect to the substrate 1. As described above, the reason why the light condensed at the point C on the substrate 1 is provided with directivity like a laser beam is that the energy density incident at the point C is increased, and the multiple interference obtained by reflection from the point C is obtained. This is because the intensity of light is increased to increase the intensity of scattered light from minute foreign substances having a small surface area of 0.3 to 0.8 μm or less. The multi-stage mirror 9 and the parabolic mirror 10 are used to form a plurality of luminous fluxes having different incident angles inclined with respect to the point C by making the optical path difference larger than the coherent distance to each other and making them non-interfering. Since both the multi-stage mirror 9 and the parabolic mirror 10 are reflection-type optical elements, the energy density for irradiating the point C can be increased while minimizing the attenuation of light irradiation energy.
[0018]
The scattered light 4 generated from the minute defect 3 such as the edge of the circuit pattern 2 or the minute foreign matter of 0.3 to 0.8 μm or less is collected by the condenser lens 11 and is provided in the space provided on the Fourier transform surface thereof. After the scattered light from the regular circuit pattern 2 is reduced by the filter 13, the scattered light is detected by the imaging lens 12 by the detector 14 such as a linear sensor. Reference numeral 15 denotes a substrate on which the detector 14 is mounted.
FIG. 2 shows the optical system of FIG. 1 developed from above the Z axis. Laser light having directivity emitted from the semiconductor laser oscillator 5 or the like is applied to the substrate 1 via a collimator lens 6 having a focal length f1, a cylindrical lens 7, a lens 8 having a focal length f2, a multistage mirror 9, and a parabolic mirror 10. Irradiated from an inclined direction. Since the high-power semiconductor laser is not a point light source but a linear light source, when the length of the light source is W2, it is enlarged according to the following equation (Equation 1). A linear illumination light 18 having a length W1 is formed.
[0019]
(Equation 1)

[0020]
Here, the distance L3 between the semiconductor laser oscillator 5 and the collimating lens 6 is equal to f1 (L3 = f1), the distance L2 between the collimating lens 6 and the lens 8 is equal to f1 + f2 (L2 = f1 + f2), and By setting the distance L1 between the lens 8 and the substrate substantially equal to f2, the light source image of the semiconductor laser oscillator is telecentrically projected on the substrate 1, and the scattered light generated when a minute foreign substance or the like exists is collected. After being sufficiently separated from the circuit pattern 2 and the like on the substrate 1 by a spatial filter 13 (FIG. 1) placed after the lens 11, the light is detected by a detector 14 such as a linear sensor via the imaging lens 12.
FIG. 3 shows an example of the spatial filter 13. In the case of the linear illumination as shown in FIG. 2, the diffracted light from the edge of the repetitive circuit pattern 2 on the substrate 1 is formed according to the principle shown in FIG. Here, S1 to S7 indicate information in the real space, and F1 to F7 indicate information in the Fourier space. For example, when a semiconductor wafer such as a memory element is considered as the substrate 1, a plurality of cell groups 21 in which a plurality of memory cells 20 are arranged at equal intervals are formed on the semiconductor wafer as shown in S7. I have. The expansion of such a model is as follows. That is, in S7, the cell group patterns S5 are arranged at regular intervals indicated by the shear function of S6. The cell group pattern S5 is obtained by subjecting a cell pattern S3 extending to infinity to an area limitation S4. The cell pattern S3 extending to infinity is considered to be a single cell pattern 20 shown in S1 arranged at equal intervals represented by the shear function of S2. The following (Equation 2) shows this.
[0021]
(Equation 2)

[0022]
Now, F1 to F7 are optical Fourier transforms of the real space information S1 to S7. In the case of Fourier transform, convolution and multiplication in the real space are converted into multiplication and convolution in Fourier space, respectively. Therefore, F7 is represented by the following equation (3) using the equation (2).
[0023]
(Equation 3)

[0024]
In F7, the 0th-order diffracted light component 23 corresponding to the specularly reflected light component is strong, and also in the spatial filter 13 in FIG. 3, the central 0th-order light blocking pattern 26 is thick. The high-order diffracted light includes a component 24 (with an arrow) that depends on the interval between the memory cells 20 and a component 25 (without an arrow) that depends on the interval between the memory cell groups 21. A pattern 27 is provided to block diffracted light depending on the number of memory cells or memory cell groups in accordance with the number (NA (Numerical Aperture)).
By the way, since the illumination light is always irradiated in the XY plane in parallel with the X axis, even if the incident angle on the substrate 1 changes from T1 to Tn as shown in FIG. There is no change in the position in the direction, and the diffraction pattern always moves parallel to the X axis. Therefore, in FIG. 3, if the

patterns

26 and 27 for shielding the diffracted light are formed into strips parallel to the X axis, it is possible to provide a spatial filter pattern independent of the incident angle.
[0025]
On the other hand, as shown in FIG. 11, one light beam (incident light) 40 among a large number of light beams having an incident angle of T1 to Tn which are condensed and irradiated from the parabolic mirror 10 to a point C on the substrate 1 is, for example, as shown in FIG. When the light is incident on the substrate 1 having a thin film structure having a refractive index of n0 to n3 and a film thickness of d1 to d3 at an incident angle Tha, refraction and reflection are repeated at the boundary surfaces A0 to A3, and reflection as so-called multiple interference light is performed. Light 41 is generated. The ratio of the light intensity between the incident light 40 and the reflected light 41 is the reflectance of the substrate. In order to increase the intensity of scattered light from a small foreign substance having a small surface area of 0.3 to 0.8 μm or less on or in the thin film, as described above, irradiation is performed from the back side of the small foreign substance. The intensity of the reflected light 41 as the multiple interference light which is the intensity of the light to be reflected
That is, it is necessary to increase the reflectance of the substrate (the ratio of the light intensity between the incident light 40 and the reflected light 41). On the other hand, the reflectivity of the substrate (the intensity of the multiple interference light) periodically varies according to the thickness of the light transmitting thin film formed on the substrate 1 as shown in FIG. By the way, as described above, in the substrate 1 to be inspected according to the present invention, the variation of the thin film also occurs in one substrate and changes according to the type of the substrate. As shown in (1), the reflectance of the substrate (the intensity of the multiple interference light) fluctuates, and the intensity of the light irradiated from the back side of the fine foreign material fluctuates, and the scattered light intensity generated from the fine foreign material also fluctuates greatly. As a result, the detection sensitivity fluctuates greatly.
[0026]
On the other hand, when the incident angle for converging and irradiating the substrate 1 is changed, the reflectance (intensity of the multiple interference light) of the substrate shown in FIG. 13 moves as indicated by the arrow with respect to the thickness of the thin film. Become. Therefore, as shown in FIG. 1, a large number of light beams that do not interfere with each other are condensed and emitted from the parabolic mirror 10 to the point C on the substrate 1 at different incident angles T1 to Tn effectively and simultaneously. As shown in FIG. 14, synthesized multiple interference light (reflected light) having a substantially constant reflectance is emitted from the thin film formed on the substrate 1 as shown in FIG. 14, and is present on the thin film 1b. Irradiation is performed on the minute foreign matter 3 from the back side, and a constant scattered light can be obtained from the minute foreign matter 3 irrespective of the variation in the thickness of the thin film 1b. Further, as described above, scattered light can also be obtained by a large number of light beams directly condensed and irradiated from the surface side of the minute foreign matter 3. FIG. 14 shows the reflectance (intensity of multiple interference light) of the substrate with respect to the thickness of the thin film at each of the incident angles T1, Tk, and Tn. However, as described above, since a plurality of light beams having these incident angles T1, Tk, and Tn are simultaneously focused and irradiated on the point C on the substrate 1, the thickness of the thin film 1b is reduced as shown in FIG. In each case of Ha and Hb, the scattered light generated from the minute foreign matter is synthesized according to each of the incident angles T1, Tk, and Tn, smoothed or averaged, and is incident on the condenser lens 11. The detector 14 can detect a substantially constant output signal 50 irrespective of the variation in the thickness of the thin film. Note that it is necessary to prevent the multiple interference light regularly reflected on the surface of the substrate 1 from entering the entrance pupil of the condenser lens 11 by the light beam irradiated at the incident angle Tn.
In this way, even if the thickness of the thin film changes within a single substrate, or the thickness of the thin film including the number of layers changes depending on the substrate, the thin film is always irradiated to the minute foreign matter. The intensity of the multiple interference light can be made substantially constant, and as a result, the scattered light generated from the minute foreign matter can be made substantially constant, and the minute foreign matter of 0.3 to 0.8 μm or less can be stably formed. It can be detected with high reliability.
[0027]
Further, as described above, the substrate 1 includes a metal thin film such as Al which is formed by sputtering and has fine irregularities on the surface in order to form the circuit pattern 2 and the like. When light (laser light) having directivity is applied to a surface having fine irregularities (roughness) on the surface, a speckle pattern is generated by interference due to the minute irregularities, and a scattered light component from the minute foreign matter 3 is reduced. You will be buried. However, as described above, as shown in FIG. 1, a large number of non-interfering light beams are condensed and irradiated from the parabolic mirror 10 to the point C on the substrate 1 at different incident angles T1 to Tn effectively and simultaneously. Therefore, a metal thin film or the like having fine irregularities on its surface exists on the substrate 1.
Therefore, even if speckles (random high luminance components) are generated, the incident angles are different as T1 to Tn, so that the bright and dark due to the speckles with high randomness cancel each other out and are smoothed. Finally, the average signal (signal from which the speckle pattern has been eliminated) 51 shown in FIG. 16 is detected by 14, and stable detection of scattered light from minute foreign matter becomes possible.
[0028]
FIG. 5 shows the configuration of a second embodiment of the apparatus for inspecting a minute defect such as a minute foreign substance present on a substrate to be inspected according to the present invention. This second embodiment is a modification of the first embodiment shown in FIG. Here, the laser light emitted from the high-output semiconductor laser oscillator 5 or the like is converted into parallel light in the Z-axis direction by the collimating lens 6, and then converted into a parallel light beam in the Z-axis direction by the

cylindrical lenses

7 and 8. The light source image of the semiconductor laser oscillator 5 is shaped at a point C in the Y-axis direction in a telecentric relationship. The optical path length of the light of the semiconductor laser oscillator 5 from the light source to the surface A is equal everywhere and has coherence, but the luminous fluxes divided by the multistage mirror 9 are each longer than the coherent distance. Are reached before reaching the B-plane, and the light beams of each other become non-interfering.
Reference numeral 16 denotes an anamorphic optical system that collects light only in the Z (or X) axis direction, in particular, includes an aspherical lens or a diffractive lens to suppress spherical aberration. It is possible to form a plurality of luminous fluxes from the incident angles T1 to Tn that converge at the point C, which do not interfere with each other and have different incident angles with respect to the substrate.
The scattered light 4 generated from the edge 3 of the circuit pattern 2 or the minute defect 3 such as a minute foreign matter is collected by the condenser lens 11 and is converted from the regular circuit pattern 2 by the spatial filter 13 provided on the Fourier transform plane. Is reduced by the imaging lens 12 and detected by the detector 14 such as a linear sensor. Reference numeral 15 denotes a substrate on which the detector 14 is mounted.
In the first and second embodiments, an analyzer (such as a polarizing plate) is provided in the optical path of the detection optical system instead of or in addition to the spatial filter 13 provided in the detection optical system. ) May be provided to block the scattered light component from the edge of the circuit pattern 2 on the substrate 1.
[0029]
FIG. 6 shows the configuration of a third embodiment of the apparatus for inspecting a minute defect such as a minute foreign substance present on a substrate to be inspected according to the present invention. That is, a plurality of semiconductor laser oscillators 5a to 5e are used here to irradiate the substrate 1 with light beams that do not interfere with each other. As described above, by using the semiconductor laser oscillators separately (independently), the laser beams output from the semiconductor laser oscillators 5a to 5e do not interfere with each other. Each of the laser light beams output from each of the semiconductor laser oscillators 5a to 5e is converted into parallel light in the Z-axis direction by each of the collimating lenses 6a to 6e, and then parallel light beams in the Z-axis direction by the cylindrical lenses 30a to 30b. Then, the light source image of the semiconductor laser oscillator 5 is shaped so as to form a telecentric relationship at the point C in the Y-axis direction.
[0030]
Reference numeral 16 denotes an anamorphic optical system that collects light only in the Z (or X) axis direction, and in particular, includes an aspherical lens or a diffractive lens to suppress spherical aberration. , C, a plurality of luminous fluxes from the incident angles T1 to Tn that do not interfere with each other and have different incident angles to the substrate 1 can be formed. Here, the mirror 31 is for bending the optical path by 45 °.
The scattered light 4 generated from the edge 3 of the circuit pattern 2 or the minute defect 3 such as a minute foreign matter is collected by the condenser lens 11 and is converted from the regular circuit pattern 2 by the spatial filter 13 provided on the Fourier transform plane. Is reduced by the imaging lens 12 and detected by the detector 14 such as a linear sensor. Reference numeral 15 denotes a substrate on which the detector 14 is mounted.
[0031]
FIG. 7 shows the configuration of a fourth embodiment of the apparatus for inspecting a minute defect such as a minute foreign substance present on an inspection target substrate according to the present invention. In the fourth embodiment, almost all lasers including an argon laser, a YAG laser, and a helium neon laser can be used. That is, the light of the single laser oscillator 32 is divided into a plurality of parts by the distributor 33 and the like, and the light is guided using the optical fibers 34a to 34e. At this time, the light coming from each optical fiber is made non-interfering by changing the length of the optical fibers so as to be longer than the coherent distance. Since the light emitted from the optical fiber can be generally treated as a point light source, it is converted into parallel light by the collimating lenses 6a to 6e, and then the spherical aberration is suppressed by the 16 anamorphic optical system only in the Z (or X) axis direction. Focus on point C in shape.
[0032]
If the permissible chromatic aberration performance of the detection optical system is satisfied, for example, a configuration in which an argon laser and a YAG laser are combined is also conceivable.
FIG. 8 shows the configuration of a fifth embodiment of the apparatus for inspecting a minute defect such as a minute foreign substance present on an inspection target substrate according to the present invention.
In the first to fourth embodiments, the optical incoherence (spatial incoherence) of the laser oscillation wavelength is used, whereas in the fifth embodiment, TDI (Time Delayed) is used. (Integration) Temporal incoherence (temporal incoherence) utilizing characteristics of a sensor is used.
[0033]
As shown in FIGS. 9 and 10, the TDI sensor has a line sensor formed in n stages. The line rate, which is the amount of information discharged from the sensor, is equivalent to that of the line sensor, but the accumulated charges are sequentially transferred to the lines 36-1 to 36-2,. By synchronizing the feed speed of a stage (not shown) for transporting the substrate 1 with the line rate, for example, the scattered light 37 from the minute foreign matter 3 is accumulated for a long time until reaching the line 36-n. As a result, highly sensitive detection becomes possible. This sensor basically detects the sum of the scattered light intensities from the image of the minute foreign matter to the line 36-1 to the line 36-n. Light is completely incoherent in time.
[0034]
Therefore, as shown in FIG. 8, when light from the semiconductor laser oscillator 5 or the like is condensed on P at a distance from the substrate surface 1 which is a common plane of the TDI sensor 35, a point Q1 on the common plane of the TDI sensor 35 is obtained. Light is irradiated to Q3 at a wide angle from the irradiation angle Tb to Ta. The position of the line 36 of the TDI sensor 35 existing between Q1 to Q3 is different, and coherence can be avoided, so that the same performance as detection in non-coherent illumination where the incident angle changes continuously. Can be obtained. Reference numeral 6 denotes a collimating lens, and 16 denotes an anamorphic optical element having a small spherical aberration.
[0035]
As described above, also in the second to fifth embodiments, the same operation and effect as those of the first embodiment can be obtained.
As a method of forming a large number of non-interfering laser light beams, besides the above embodiment, for example, as shown in FIG. The modulated laser beam can be modulated by the condenser lens 8 to obtain a large number of laser beams without interference.
In the embodiment of the present invention, the example in which the linear sensor is used to detect the scattered light from the minute defect 3 such as the minute foreign matter is shown. However, even when the point sensor such as the photomultiplier tube is used, the illumination light is slit. Although it is necessary to change the shape from spot to spot and add a spot scanning system, basically the same optical system can be used.
[0036]
Further, the embodiment has been described for an optical system for oblique illumination upward detection (when the optical axis of the detection optical system composed of 11 to 14 is substantially perpendicular to the surface of the substrate 1). Considering inspection of various objects such as a substrate, a TFT liquid crystal display device, or a magnetic disk substrate, oblique illumination side detection (the optical axis of a detection optical system including 11 to 14 is referred to the surface of the substrate 1 as a reference. This is a case where the light is inclined in the Y-axis direction substantially perpendicular to the optical axis of the illumination optical system.In this case also, the specularly reflected light from the surface of the substrate 1 is not incident on the condenser lens 11.) Side illumination backside detection, or a combination thereof, is also conceivable.
[0037]
【The invention's effect】
According to the present invention, the thickness of a light-transmitting thin film formed on a substrate such as a semiconductor substrate, a multilayer thin film substrate (printed substrate), a TFT substrate or a magnetic disk substrate differs between the substrates or within the substrate. When the reflectivity of the substrate changes, or when the surface has minute irregularities (roughness) such as a metal thin film formed on the substrate, the surface area is small, 0.3 to 0.8 μm or less. The fluctuation of the scattered light generated from minute defects such as minute foreign matters is reduced, the intensity is increased as much as possible, and the minute defects of 0.3 to 0.8 μm or less existing on the substrate are detected with high sensitivity, and It is possible to detect with high reliability and to improve the yield in the substrate manufacturing process.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of a minute defect detection device according to the present invention.
FIG. 2 is an optical path development diagram centered on an illumination optical system developed by facing the optical system shown in FIG. 1 from the Z-axis direction.
FIG. 3 is a diagram showing a shape of a spatial filter used in the device shown in FIG.
FIG. 4 is a diagram for explaining the operation of the spatial filter shown in FIG.
FIG. 5 is a configuration diagram showing a second embodiment of the minute defect detection device according to the present invention.
FIG. 6 is a configuration diagram showing a third embodiment of the minute defect detection device according to the present invention.
FIG. 7 is a configuration diagram showing a fourth embodiment of the minute defect detection device according to the present invention.
FIG. 8 is a configuration diagram showing a fifth embodiment of the minute defect detection device according to the present invention.
FIG. 9 is a diagram illustrating a state at t = t0 for explaining the operation of the TDI sensor.
FIG. 10 is a diagram illustrating a state at t = t0 + dt for explaining the operation of the TDI sensor.
FIG. 11 is a diagram for describing multiple interference generated in a substrate having a thin film structure.
FIG. 12 is a diagram showing a cross section of a part of a semiconductor wafer in which a change in thickness of a thin film, which is an example of a substrate to be inspected according to the present invention, is observed.
FIG. 13 is a diagram showing the relationship between the thickness of a thin film and the reflectance (intensity of multiple interference light) of a thin film when the incident angle of a light beam condensed and irradiated on a substrate is changed.
FIG. 14 shows the thickness of the thin film and the reflectivity of the substrate (intensity of multiple interference light) when a plurality of light beams having incident angles T1, Tk, and Tn are respectively effectively condensed and irradiated onto the substrate. FIG.
FIG. 15 is a diagram for explaining the contents shown in FIG. 15 with a detection waveform detected by a detector.
FIG. 16 is a diagram illustrating that a speckle pattern caused by minute irregularities on a metal thin film of Al or the like formed on a substrate is erased, using a detection waveform detected by a detector.
FIG. 17 is a view showing a configuration different from the first to fifth embodiments in the minute defect detection device according to the present invention.
[Explanation of symbols]
Reference Signs List 1 ... substrate, 1a ... Si substrate, 1b ... thin film (insulating film, protective film, resist film)
2 ... Circuit pattern, 3 ... Small foreign matter (small defect), 5 ... Semiconductor laser oscillator
6: Collimating lens, 7: Cylindrical lens, 8: Lens, 9: Multistage mirror
10: parabolic mirror, 11: condenser lens, 12: imaging lens
13 spatial filter, 14 detector, 16 anamorphic optical system
17 ... Mirror, 35 ... TDI sensor

Claims

By splitting the beam emitted from the light source and making the optical path lengths different from each other, a plurality of spatially incoherent luminous fluxes are obtained, and the obtained luminous fluxes are incident at different angles with respect to a desired position on the substrate. Irradiation in oblique direction, reflected and scattered light generated from minute defects on the substrate by the irradiation is collected by a detection optical system, received by a photoelectric conversion unit, and received by a photoelectric conversion unit. minute defect detecting method and detecting the minute defects.

The method according to claim 1 , wherein the light source is a laser light source .

A plurality of mutually incoherent luminous fluxes are illuminated substantially simultaneously at desired locations on the substrate surface at mutually different inclined incident angles so as to be substantially in the same direction when projected onto the substrate surface. The reflection scattered light generated from the edge of the circuit pattern and the minute defect on the substrate is condensed by the detection optical system, and the reflected scattered light generated from the edge of the circuit pattern is shielded by the light shielding means, and is obtained by passing through the light shielding means. A minute defect detection method, comprising: receiving reflected scattered light by a photoelectric conversion unit; and detecting a minute defect on the substrate by a signal obtained from the photoelectric conversion unit.

While transporting the substrate on which the thin film is formed in the transport direction, the laser beam emitted from the laser oscillator is applied to the substrate from the oblique direction in the transport direction at a wide angle from the irradiation angle Tb to the irradiation angle Ta from above the substrate to the back side. The light is focused and irradiated at a predetermined distance from the substrate, and reflected and scattered light generated by the irradiation at a wide angle from the edge of the circuit pattern and the minute defect on the substrate conveyed in the conveyance direction is collected by a detection optical system. The reflected scattered light generated from the edge of the circuit pattern is shielded by the light shielding means, and the reflected scattered light obtained through the light shielding means is accumulated in the transport direction by the TDI sensor and received and received from the TDI sensor. A minute defect detection method, wherein a minute defect on the substrate is detected by an obtained signal.

An optical system for splitting a beam emitted from a light source to obtain a plurality of spatially incoherent luminous fluxes by making the optical path lengths different from each other, and a plurality of luminous fluxes obtained by the optical system is applied to a desired portion on a substrate. An irradiation optical system for irradiating obliquely at different incident angles with respect to
A detection optical system that collects reflected scattered light generated from minute defects on the substrate irradiated by the irradiation optical system and receives the reflected scattered light by photoelectric conversion means,
A minute defect on the substrate, which is detected by a signal obtained from a photoelectric conversion unit of the detection optical system .

The micro defect detecting device according to claim 5, wherein the light source of the irradiation optical system is a laser light source .

An optical system that obtains a plurality of spatially incoherent laser beams by making the optical path lengths different from each other, and the substrate is formed such that the intensity of reflected light obtained from the substrate on which the thin film is formed is averaged or smoothed. for the desired location of the upper, an irradiation optical system for irradiating a different incidence angles plurality of laser beams of mutually spatially incoherent obtained in the optical system from an oblique direction I lifting,
A detection optical system for condensing reflected scattered light generated from the edge of a microdefect and a circuit pattern by the plurality of laser beams irradiated by the irradiation optical system,
Light shielding means for shielding reflected scattered light generated from the edge of the circuit pattern among reflected scattered light collected by the detection optical system,
A photoelectric conversion unit that receives reflected scattered light obtained through the light shielding unit and converts the reflected scattered light into a signal,
A micro-defect detecting device, wherein a micro-defect on the substrate is detected by a signal obtained from the photoelectric conversion means.

A plurality of mutually incoherent light beams, an irradiation optical system that effectively irradiates a desired portion on the substrate surface almost simultaneously at different incident angles different from each other so as to be substantially the same direction when projected on the substrate surface,
A detection optical system for condensing reflected scattered light generated from the edge of the microdefect and circuit pattern by the plurality of light beams irradiated by the irradiation optical system,
Light shielding means for shielding reflected scattered light generated from the edge of the circuit pattern among reflected scattered light collected by the detection optical system,
A photoelectric conversion unit that receives reflected scattered light obtained through the light shielding unit and converts the reflected scattered light into a signal,
A micro-defect detecting device, wherein a micro-defect on the substrate is detected by a signal obtained from the photoelectric conversion means.

While transporting the substrate on which the thin film is formed in the transport direction, the laser beam emitted from the laser oscillator is applied to the substrate from the oblique direction in the transport direction at a wide angle from the irradiation angle Tb to the irradiation angle Ta from above the substrate to the back side. An irradiation optical system for converging and irradiating a position at a predetermined distance to the
A detection optical system for condensing reflected scattered light generated by irradiation of a wide angle by the irradiation optical system from the edge of the microdefect and the circuit pattern transferred on the substrate in the transfer direction,
Light-shielding means for shielding the reflected scattered light generated from the edge of the circuit pattern by condensing with the detection optical system,
A TDI sensor that accumulates reflected scattered light obtained through the light shielding means in the transport direction, receives the light, and converts the light into a signal;
A minute defect detecting device, wherein a minute defect on the substrate is detected by a signal obtained from the TDI sensor.

10. The micro defect detecting device according to claim 7, wherein the light shielding unit is formed by a spatial filter.