JP4150535B2

JP4150535B2 - Charged particle beam equipment

Info

Publication number: JP4150535B2
Application number: JP2002165053A
Authority: JP
Inventors: 英治河合
Original assignee: Jeol Ltd
Current assignee: Jeol Ltd
Priority date: 2002-06-06
Filing date: 2002-06-06
Publication date: 2008-09-17
Anticipated expiration: 2022-06-06
Also published as: JP2004014251A

Description

【０００１】
【発明の属する分野】
本発明は半導体ウエハの如き大型試料の観察に適した荷電粒子ビーム装置に関する。
【０００２】
【従来の技術】
近時、半導体ウエハ等の大型試料を観察するために、大型試料の装着及び移動の出来る大型試料室を備えた走査電子顕微鏡が使用されている。
【０００３】
図１は大型試料の観察が可能な査電子顕微鏡の概略例を示している。
【０００４】
図中１は電子銃、２は集束レンズ、３は偏向レンズ、４は対物レンズで、電子銃１からの電子ビームは集束レンズ２及び対物レンズ４により試料ホルダー５上に支持された半導体ウエハの如き試料６の上に微小に絞られる。
【０００５】
この微小に絞られた電子ビームは、中央制御装置７からの指令により走査信号を出力する走査信号発生回路８からの走査信号を受けた偏向レンズ３により、試料上の所定の範囲を走査する。
【０００６】
この様な電子ビームによる試料上の走査により発生した二次電子は二次電子検出器９により検出される。
【０００７】
二次電子検出器９で検出された試料６から二次電子信号は試料の表面形状情報を持った信号で、アンプ１０を介して中央制御装置７に送られ、該中央制御装置７の指令に基づいて、陰極線管の如き表示装置１１に試料６の二次電子像が表示される。
【０００８】
尚、１２は試料ホルダー５を載置したステージで、中央制御装置７からの移動指令を受ける駆動機構１３によりＸ，Ｙ及びＺ方向に移動出来る様に成っている。
【０００９】
図２は、図１の一部詳細図で、４０は対物レンズ４の磁極片、５０は半導体ウエハの如き試料６０を載置した試料ホルダである。尚、試料ホルダー５０は導電性材料で形成されており、対物レンズの磁極片４０と共に大地電位にある。
【００１０】
９０は二次電子検出器で、前面に導電性薄膜が蒸着されているシンチレーター９１，ライトガイド９２，光電子増倍管９３，リング状電極９４等から成り、リング状電極９４と前記導電性薄膜には直流電源（図示せず）から正の高電圧（例えば、１０ＫＶ）が印加されている。又、シンチレーター９１，ライトガイド９２，光電子増倍管９３及びリング状電極９４の周囲には、例えば、大地電位若しくは可変な電位（０〜＋１００Ｖ程度）が与えられるガイド筒９５が設けられている。
【００１１】
この様な二次電子検出器において、前記リング状電極９４と前記導電性薄膜に正の高電圧が印加されると、対物レンズの磁極極片４０や半導体試料は大地電位にあるので、シンチレーター９１の前方に正の電界が形成され、試料からの二次電子が二次電子検出器９０に捕獲される。
【００１２】
【発明が解決しようとする課題】
さて、観察すべき試料が大型の半導体ウエハの場合、半導体ウエハ上には、同一種類のパターンが描かれた極めて多くの領域（例えば、セル、チップ等）が形成されており、これらの領域を観察する場合、その都度、ステージ１２を移動させ、観察すべき領域が電子光学系の光軸Ｏ上に来るようにしている。
【００１３】
そして、光軸上に来た領域を電子ビームで走査し、領域からの二次電子を検出して二次電子像を表示装置に表示させ、観察を行っている。
【００１４】
この様な領域の表示（観察）において、半導体ウエハの中央部及び中央部近傍にある領域が表示（観察）の対象の場合と、半導体ウエハの周辺部近傍にある領域が表示（観察）の対象の場合とで、シンチレーター９１の前方に形成される電界の様子が異なる。
【００１５】
前者の場合は、凡そ、二次電子検出器９０のガイド筒９５の反光軸側の延長線に試料６０が存在する場合に相当し、その場合には、図２の破線に示す様に、対物レンズの磁極片４０と二次電子検出器９の間における等電位面間隔及び試料６０と二次電子検出器９の間における等電位面間隔が比較的等間隔に近い状態の電位分布となる。従って、試料からの二次電子は、軌跡２１に示す様に等電位面を横切って進んで来るので、効率良くシンチレーター９１に入る。
【００１６】
後者の場合は、凡そ、二次電子検出器９０のガイド筒９５の少なくとも反光軸側の延長線上に試料６０が存在しない場合に相当し、その場合、図３に示す様に、対物レンズの磁極片４０と二次電子検出器９の間における等電位面間隔は比較的等間隔であるが、試料６０と二次電子検出器９の間における等電位面が外側に大きく発散する電位分布となる。その為、試料からの二次電子がシンチレーター９１に入る効率が悪くなる。
【００１７】
この結果、本来、同一形状の領域であっても、試料の中央部及び中央部近傍にある領域の場合と、試料の周辺部近傍にある領域とで、コントラストが可成り異なる二次電子像が表示されることになってしまい、半導体ウエハの如き大型試料の観察に支障を来すことになる。
【００１８】
本発明は、この様な問題を解決する新規な荷電粒子ビーム装置を提供することを目的としたものである。
【００１９】
【課題を解決するための手段】
本発明に基づく荷電粒子ビーム装置は、試料台上に載置された試料上の所定領域を荷電粒子ビームで走査し、該走査により試料から発生した二次電子を、試料と対物レンズの間に配設された二次電子検出器で検出し、該検出した二次電子に基づいて前記走査領域の二次電子像を得るように成した荷電粒子ビーム装置において、前記試料台の周辺部に下段の面が形成される様に該試料台を二段構えに成し、その上段の面に試料を載置し、下段の面に、該下段の面と前記上段の面との段差を取り囲む様な補正電極を載置するように成し、該下段の面に載置された補正電極は、試料表面と面一となる厚さを有し、試料上の最も外側の観察領域を観察する時に、前記二次電子検出器の二次電子検出面に垂直な側面の内、反電子光学光軸側の延長線が前記補正電極の二次電子検出器側の面に交差する様に配置され、該補正電極と試料とが同電位になるようにしたことを特徴とする。
本発明に基づく荷電粒子ビーム装置は、試料台上に載置された試料上の所定領域を荷電粒子ビームで走査し、該走査により試料から発生した二次電子を、試料と対物レンズの間に配設された二次電子検出器で検出し、該検出した二次電子に基づいて前記走査領域の二次電子像を得るように成した荷電粒子ビーム装置において、試料台を二段構えに成し、上段の面に試料を載置し、下段の面に、前記試料台とは電気的に絶縁して該下段の面と前記上段の面との段差を取り囲む様な補正電極を載置するように成し、該下段の面に載置された補正電極は、試料表面と面一となる厚さを有するように成し、該補正電極に大きさがコントロール可能な負の電圧を印加することによって前記二次電子検出器の二次電子検出面前方に形成される電界を該二次電子検出器側に押しやることが出来るように成したことを特徴とする。
本発明に基づく荷電粒子ビーム装置は、試料台上に載置された試料上の所定領域を荷電粒子ビームで走査し、該走査により試料から発生した二次電子を、試料と対物レンズの間に配設された二次電子検出器で検出し、該検出した二次電子に基づいて前記走査領域の二次電子像を得るように成した荷電粒子ビーム装置において、試料台の側面に該試料台とは電気的に絶縁して該側面を取り囲む様な補正電極を取り付け、該補正電極に大きさがコントロール可能な負の電圧を印加することによって前記二次電子検出器の二次電子検出面前方に形成される電界を該二次電子検出器側に押しやることが出来るように成したことを特徴とする。
本発明の荷電粒子ビーム装置は、試料台上に載置された試料上の所定領域を荷電粒子ビームで走査し、該走査により試料から発生した二次イオンを、試料と対物レンズの間に配設された二次イオン検出器で検出し、該検出した二次イオンに基づいて前記走査領域の二次イオン像を得るように成した荷電粒子ビーム装置において、前記試料台の周辺部に下段の面が形成される様に該試料台を二段構えに成し、その上段の面に試料を載置し、その下段の面に、該下段の面と前記上段の面との段差を取り囲む様な補正電極を載置するように成し、該下段の面に載置された補正電極は、試料表面と面一となる厚さを有し、試料上の最も外側の観察領域を観察する時に、前記二次イオン検出器の二次イオン検出面に垂直な側面の内、反電子光学光軸側の延長線が前記補正電極の二次イオン検出器側の面に交差する様に配置され、該補正電極と試料とが同電位になるようにしたことを特徴とする。
【００２０】
本発明の荷電粒子ビーム装置は、試料台上に載置された試料上の所定領域を荷電粒子ビームで走査し、該走査により試料から発生した二次イオンを、試料と対物レンズの間に配設された二次イオン検出器で検出し、該検出した二次イオンに基づいて前記走査領域の二次イオン像を得るように成した荷電粒子ビーム装置において、試料台を二段構えに成し、上段の面に試料を載置し、下段の面に、前記試料台とは電気的に絶縁して該下段の面と前記上段の面との段差を取り囲む様な補正電極を載置するように成し、該下段の面に載置された補正電極は、試料表面と面一となる厚さを有するように成し、該補正電極に大きさがコントロール可能な正の電圧を印加することによって前記二次イオン検出器の二次イオン検出面前方に形成される電界を該二次イオン検出器側に押しやることが出来るように成したことを特徴する。
本発明の荷電粒子ビーム装置は、試料台上に載置された試料上の所定領域を荷電粒子ビームで走査し、該走査により試料から発生した二次イオンを、試料と対物レンズの間に配設された二次イオン検出器で検出し、該検出した二次イオンに基づいて前記走査領域の二次イオン像を得るように成した荷電粒子ビーム装置において、試料台の側面に該試料台とは電気的に絶縁して該側面を取り囲む様な補正電極を取り付け、該補正電極に大きさがコントロール可能な正の電圧を印加することによって前記二次イオン検出器の二次イオン検出面前方に形成される電界を該二次イオン検出器側に押しやることが出来るように成したことを特徴とする。
【００２１】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態を詳細に説明する。
【００２２】
図４は本発明の一例を示した走査電子顕微鏡の主要部の概略例を示している。図中、前記図２にて使用した記号と同一記号の付されたものは同一構成要素を示す。
【００２３】
図４において、５０Ａは試料ホルダーで、二段構成になっており、上段の面が試料載置面になっており、下段の面が段差を取り囲む様な形状の補正電極３１Ａの載置面になっている。
【００２４】
補正電極３１Ａは、試料ホルダー５０Ａの下段の面に載せた時に、その上面が試料表面と面一になるような厚さに、ステージを移動させて試料上の最も外側の領域が光軸Ｏ上に来た時に、ガイド筒９５の反光軸側の延長上の外側に補正電極３１Ａの可成りの部分が存在する程度の幅に形成されている。
【００２５】
半導体ウエハの周辺部近傍にある領域を観察する場合、観察すべき領域が光軸上に来るようにステージを移動させ、その状態で領域上を電子ビームで走査し、該走査により試料から発生した二次電子を二次電子検出器で検出し、検出した二次電子信号に基づいて表示装置上に試料の二次電子像を表示させる。
【００２６】
この場合、補正電極３１Ａは試料６０と同電位（大地電位）にあり、又、その上面は試料表面と面一になっており、更に、ガイド筒９５の反光軸側延長上の外側に補正電極３１Ａの可成りの部分が存在する状態になっているので、二次電子検出器９０と、試料６０及び補正電極３１Ａとの間における等電位面間隔は比較的等間隔になり、図２に示す場合と同様に、試料６０からの二次電子は、効率良くシンチレーター９１に入る。
【００２７】
図５は本発明の一例を示した走査電子顕微鏡の主要部の別の概略例を示している。
【００２８】
この例では、試料ホルダー５０Ｂの下段の面の幅が図４のものに比べ可成り小さくなっており、その上に絶縁板３２を介して載置される補正電極３１Ｂの幅もその分だけ小さくなっている。即ち、試料ホルダー５０Ｂの下段の面に段差を取り囲む様な形状の補正電極３１Ｂを載せた時に、その上面が試料表面と面一になるような厚さなっているが、ステージを移動させて試料上の最も外側の領域が光軸上に来た時に、ガイド筒９５の反光軸側延長上の外側に少なくとも補正電極３１Ｂの僅かな部分しか存在しない幅に形成されている。
【００２９】
更に、可変補正電源３３が設けられており、この補正電極３１Ｂに負の直流高電圧が印加出来る様に成っている。
【００３０】
この様な構成において、半導体ウエハの周辺部近傍にある領域を観察する場合、観察すべき領域が光軸上に来るようにステージを移動させ、その状態で領域上を電子ビームで走査し、該走査により試料から発生した二次電子を二次電子検出器で検出し、検出した二次電子信号に基づいて表示装置上に試料の二次電子像を表示させる。
【００３１】
この場合、補正電極３１Ｂの上面は試料表面と面一になっており、二次電子検出器９０のガイド筒９５の反光軸側延長上の外側に少なくとも補正電極３１Ｂの僅かな部分しか存在しない状態になっているが、補正電極３１Ｂに負の高電圧を印加することにより、補助電極３１Ｂの表面上に負の電界が形成され、二次電子検出器９０のシンチレーター９１前方の正の電界を二次電子検出器９０側に押しやることとなる。その結果、補正電極３１Ｂと二次電子検出器９の間の電位分布は外側に大きく発散せずに、二次電子検出器９０と、試料６０及び補正電極３１Ａとの間における等電位面間隔は比較的等間隔になり、図２に示す場合と同様に、試料６０からの二次電子は、効率良くシンチレーター９１に入る。
【００３２】
この様な電位分布の補正は、例えば、表示装置に表示されている試料の二次電子像のコントラストを見ながら、可変補正電源３２からの負電圧値をコントロールすることにより行っている。
【００３３】
尚、この様な補正は、電位分布を解析に基づいて行うようにしても良い。
【００３４】
又、半導体ウエハの周辺近傍の領域の二次電子像を得る場合、同じ周辺部領域であっても、中心部からの離れ具合により二次電子検出器９０と補正電極３１Ｂ間の電位分布が多少異なるので、予め、実験等で、周辺部の各領域に対する適正な補正電圧値を求めて、領域の位置と補正電圧値をテーブル化し、実際の領域の観察時、テーブルから観察すべき領域の位置に応じた補正電圧値を呼び出し、自動的に二次電子検出器９０と補正電極３１Ｂ間の電位分布を補正するようにしても良い。
【００３５】
図６は本発明の一例を示した走査電子顕微鏡の主要部の別の概略例を示している。
【００３６】
この例では、試料ホルダー５０Ｃを一段構成にし、その径を試料６０の径より小さいものとしている。そして、その試料ホルダー５０Ｃの側面に該側面を取り囲む様な円錐筒状の補正電極３１Ｃを絶縁板３４を介して取り付けており、絶縁板３４及び補正電極３１Ｃを含む試料ホルダー５０Ｃ全体の径が図５に示すものより小さくしている。
【００３７】
この場合も、可変補正電源３５が設けられており、この補正電極３１Ｃに負の直流高電圧が印加出来る様に成っている。
【００３８】
この様な構成において、半導体ウエハの周辺部近傍にある領域を観察する場合、観察すべき領域が光軸上に来るようにステージを移動させ、その状態で領域上を電子ビームで走査し、該走査により試料から発生した二次電子を二次電子検出器で検出し、検出した二次電子信号に基づいて表示装置上に試料の二次電子像を表示させる。
【００３９】
この場合、補正電極３１Ｃの上面は試料表面より少し下になっており、二次電子検出器９０のシンチレーター９１の表面と補正電極３１Ｃの側面がほぼ対向する様な状態になっているが、図５の場合と同様に、補正電極３１Ｃに可変補正電源３５から負の高電圧を印加することにより、補正電極３１Ｃの表面上に負の電界が形成され、二次電子検出器９０のシンチレーター９１前方の正の電界を二次電子検出器９０側に押しやることとなる。その結果、補正電極３１Ｃと二次電子検出器９の間の電位分布は外側に大きく発散せずに、二次電子検出器９０と、試料６０及び補正電極３１Ｃとの間における等電位面間隔は比較的等間隔になり、図２に示す場合と同様に、試料６０からの二次電子は、効率良くシンチレーター９１に入る。
【００４０】
尚、この場合には、図５の場合に比べ、より大きな負の高電圧の印加が必要になる。
【００４１】
この様な電位分布の補正は、例えば、表示装置に表示されている試料の二次電子像のコントラストを見ながら、可変補正電源３５からの負電圧値をコントロールすることにより行っている。
【００４２】
尚、この場合においても、試料周辺部近傍の領域の二次電子像を得る場合、同じ周辺部領域であっても、中心部からの離れ具合により二次電子検出器９０と補正電極３１Ｃ間の電位部分布が多少異なるので、予め、実験等で、周辺部の各領域に対する適正な補正電圧値を求めておき、領域の位置と補正電圧値をテーブル化し、実際の領域の観察時、テーブルから観察領域の位置に応じた補正電圧値を呼び出し、自動的に二次電子検出器９０と補正電極３１そ間の電位部分布を補正するようにしても良い。
【００４３】
本発明によれば、半導体ウエハの如き大型試料の二次電子像観察において、試料からの二次電子を捕獲するための二次電子検出器周辺の電位分布を、試料の周辺近傍部の領域を観察する場合についても、試料の中心部及び中心部の近傍の領域を観察する場合とほぼ同じものに出来るので、半導体ウエハの如き大型試料のどこの領域の二次電子像もほぼ同一のコントラストで得られる。
【００４４】
尚、半導体ウエハの如き試料を観察する場合、高加速の電子ビーム照射による試料の破壊を防止したり、或いは、試料に形成されたコンタクトホールからの二次電子をより効率的に検出するために試料に負の高電圧を印加することがあるが、この様な構成の走査電子顕微鏡においても本発明を使用することが出来ることはいうまでもない。
【００４５】
又、前記例では、試料台は導電性部材で形成され、大地の電位にあったが、絶縁性部材で形成された試料台を使用する場合には、試料を直接、大地電位に落とすように成す。
【００４６】
又、前記例では、走査電子顕微鏡を例に上げたが、イオンビームで試料上を走査し、二次電子像を得るように成した装置にも応用可能である。
【００４７】
又、二次電子検出器の代わりに二次イオン検出器を設け、イオンビームで試料上を走査し、該走査により二次イオン検出器で検出された二次イオンに基づいて二次イオン像を得るように成した装置にも応用可能である
【図面の簡単な説明】
【図１】大型試料の観察が可能な査電子顕微鏡の概略例を示している。
【図２】図１の一部詳細図を示している。
【図３】試料の周辺部を観察する場合を示している。
【図４】本発明の一例を示した走査電子顕微鏡の主要部の概略例を示している。
【図５】本発明の一例を示した走査電子顕微鏡の主要部の他の概略例を示している。
【図６】本発明の一例を示した走査電子顕微鏡の主要部の他の概略例を示している。
【符号の説明】
１…電子銃
２…集束レンズ
３…偏向レンズ
４…対物レンズ
５，５０，５０Ａ，５０Ｂ，５０Ｃ…試料ホルダー
６，６０…試料
７…中央制御装置
８…走査信号発生回路
９，９０…二次電子検出器
１０…アンプ
１１…表示装置
１２…ステージ
１３…駆動機構
Ｏ…電子光学系光軸
２１…軌跡
３１Ａ，３１Ｂ，３１Ｃ…補正電極
３２，３４…絶縁板
３３，３５…可変補正電源
４０…対物レンズの磁極片
９１…シンチレーター
９２…ライトガイド
９３…光電子増倍管
９４…リング状電極
９５…ガイド筒[0001]
[Field of the Invention]
The present invention relates to a charged particle beam apparatus suitable for observing a large sample such as a semiconductor wafer.
[0002]
[Prior art]
Recently, in order to observe a large sample such as a semiconductor wafer, a scanning electron microscope having a large sample chamber in which the large sample can be mounted and moved has been used.
[0003]
FIG. 1 shows a schematic example of an electron microscope capable of observing a large sample.
[0004]
In the figure, 1 is an electron gun, 2 is a focusing lens, 3 is a deflection lens, 4 is an objective lens, and an electron beam from the electron gun 1 is a semiconductor wafer supported on the sample holder 5 by the focusing lens 2 and the objective lens 4. Such a sample 6 is finely squeezed on.
[0005]
This finely focused electron beam scans a predetermined range on the sample by the deflection lens 3 that receives the scanning signal from the scanning signal generation circuit 8 that outputs the scanning signal in response to a command from the central control unit 7.
[0006]
Secondary electrons generated by scanning the specimen with such an electron beam are detected by a secondary electron detector 9.
[0007]
A secondary electron signal from the sample 6 detected by the secondary electron detector 9 is a signal having the surface shape information of the sample, and is sent to the central control device 7 via the amplifier 10, and the command of the central control device 7 is received. Based on this, a secondary electron image of the sample 6 is displayed on the display device 11 such as a cathode ray tube.
[0008]
Reference numeral 12 denotes a stage on which the sample holder 5 is placed so that the stage 12 can be moved in the X, Y, and Z directions by a drive mechanism 13 that receives a movement command from the central controller 7.
[0009]
FIG. 2 is a partial detail view of FIG. 1, wherein 40 is a magnetic pole piece of the objective lens 4, and 50 is a sample holder on which a sample 60 such as a semiconductor wafer is placed. The sample holder 50 is made of a conductive material and is at ground potential together with the pole piece 40 of the objective lens.
[0010]
A secondary electron detector 90 is composed of a scintillator 91 having a conductive thin film deposited on the front surface, a light guide 92, a photomultiplier tube 93, a ring electrode 94, and the like. A positive high voltage (for example, 10 KV) is applied from a DC power source (not shown). Further, around the scintillator 91, the light guide 92, the photomultiplier tube 93, and the ring electrode 94, for example, a guide cylinder 95 to which a ground potential or a variable potential (about 0 to + 100V) is provided is provided.
[0011]
In such a secondary electron detector, when a positive high voltage is applied to the ring electrode 94 and the conductive thin film, the pole pole piece 40 of the objective lens and the semiconductor sample are at ground potential. A positive electric field is formed in front of, and secondary electrons from the sample are captured by the secondary electron detector 90.
[0012]
[Problems to be solved by the invention]
Now, when the sample to be observed is a large semiconductor wafer, an extremely large number of areas (for example, cells, chips, etc.) on which the same type of pattern is drawn are formed on the semiconductor wafer. When observing, the stage 12 is moved each time so that the region to be observed is on the optical axis O of the electron optical system.
[0013]
Then, the region on the optical axis is scanned with an electron beam, secondary electrons from the region are detected, and a secondary electron image is displayed on the display device for observation.
[0014]
In the display (observation) of such a region, the region in the central part of the semiconductor wafer and the region in the vicinity of the central portion are objects of display (observation), and the region in the vicinity of the peripheral part of the semiconductor wafer is an object of display (observation) In this case, the state of the electric field formed in front of the scintillator 91 is different.
[0015]
The former case corresponds to the case where the sample 60 exists on the extension line on the side opposite to the optical axis of the guide cylinder 95 of the secondary electron detector 90. In this case, as shown by the broken line in FIG. The potential distribution is such that the equipotential surface interval between the lens pole piece 40 and the secondary electron detector 9 and the equipotential surface interval between the sample 60 and the secondary electron detector 9 are relatively close to each other. Accordingly, the secondary electrons from the sample proceed across the equipotential surface as indicated by the locus 21 and enter the scintillator 91 efficiently.
[0016]
The latter case corresponds to a case where the sample 60 does not exist on at least the extension line of the guide tube 95 of the secondary electron detector 90 on the side opposite to the optical axis. In this case, as shown in FIG. The equipotential surface spacing between the piece 40 and the secondary electron detector 9 is relatively equidistant, but the equipotential surface between the sample 60 and the secondary electron detector 9 has a potential distribution that diverges greatly to the outside. . Therefore, the efficiency with which the secondary electrons from the sample enter the scintillator 91 is deteriorated.
[0017]
As a result, even if the region is essentially the same shape, there are secondary electron images in which the contrast is significantly different between the region near the center of the sample and the region near the center and the region near the periphery of the sample. It will be displayed, which will hinder the observation of a large sample such as a semiconductor wafer.
[0018]
An object of the present invention is to provide a novel charged particle beam apparatus that solves such problems.
[0019]
[Means for Solving the Problems]
A charged particle beam apparatus according to the present invention scans a predetermined area on a sample placed on a sample stage with a charged particle beam, and transfers secondary electrons generated from the sample between the sample and the objective lens. In a charged particle beam apparatus that is detected by a secondary electron detector disposed and obtains a secondary electron image of the scanning region based on the detected secondary electrons , a lower stage is provided at the periphery of the sample stage. form the sample stage so as to face is formed on the twofold of, placing a sample on a surface of the upper, the lower surface, like surrounds a step between the surface and the upper surface of the lower stage The correction electrode placed on the lower surface has a thickness that is flush with the sample surface, and is used for observing the outermost observation area on the sample. Of the side surface perpendicular to the secondary electron detection surface of the secondary electron detector, the extension line on the anti-electron optical axis side is the front. It is arranged so as to intersect the plane of the secondary electron detector side of the correction electrode, and the correction electrode and the sample, characterized in that set to be the same potential.
A charged particle beam apparatus according to the present invention scans a predetermined area on a sample placed on a sample stage with a charged particle beam, and transfers secondary electrons generated from the sample between the sample and the objective lens. In a charged particle beam apparatus that detects a secondary electron image of the scanning region based on the detected secondary electrons and detects a secondary electron image based on the detected secondary electrons, the sample stage is configured in two stages. A sample is placed on the upper surface, and a correction electrode is placed on the lower surface so as to surround the step between the lower surface and the upper surface while being electrically insulated from the sample table. The correction electrode placed on the lower surface has a thickness that is flush with the sample surface, and a negative voltage whose size is controllable is applied to the correction electrode. the secondary of the electric field formed in the secondary electron detection surface in front of the secondary electron detector by Characterized in that form to be able to push the child detector side.
A charged particle beam apparatus according to the present invention scans a predetermined area on a sample placed on a sample stage with a charged particle beam, and transfers secondary electrons generated from the sample between the sample and the objective lens. In a charged particle beam apparatus that is detected by a secondary electron detector disposed and obtains a secondary electron image of the scanning region based on the detected secondary electrons, the sample stage is provided on a side surface of the sample stage. A correction electrode that is electrically insulated from and surrounds the side surface is attached, and a negative voltage whose size is controllable is applied to the correction electrode, whereby the secondary electron detection surface of the secondary electron detector is in front. The electric field formed in ( 2) can be pushed toward the secondary electron detector.
The charged particle beam apparatus of the present invention scans a predetermined region on a sample placed on a sample stage with a charged particle beam, and distributes secondary ions generated from the sample between the sample and the objective lens. In a charged particle beam apparatus which is detected by a secondary ion detector provided and obtains a secondary ion image of the scanning region based on the detected secondary ions , a lower stage is provided at the periphery of the sample stage. form the sample stage so as to face is formed on the twofold, placing the sample on the surface of the upper, on the surface of the lower, like surrounds a step between the surface and the upper surface of the lower stage The correction electrode placed on the lower surface has a thickness that is flush with the sample surface, and is used for observing the outermost observation area on the sample. , Of the side surface perpendicular to the secondary ion detection surface of the secondary ion detector, on the anti-electron optical optical axis side It is arranged so that the long line intersects the surface of the secondary ion detector side of the correction electrode, and the correction electrode and the sample, characterized in that set to be the same potential.
[0020]
The charged particle beam apparatus of the present invention scans a predetermined region on a sample placed on a sample stage with a charged particle beam, and distributes secondary ions generated from the sample between the sample and the objective lens. In a charged particle beam apparatus which is detected by a secondary ion detector provided and obtains a secondary ion image of the scanning region based on the detected secondary ions, the sample stage is configured in two stages. The sample is placed on the upper surface, and the correction electrode is placed on the lower surface so as to surround the step between the lower surface and the upper surface while being electrically insulated from the sample table. The correction electrode placed on the lower surface has a thickness that is flush with the sample surface, and a positive voltage whose size can be controlled is applied to the correction electrode. the electric field formed at the secondary ion detection surface in front of the secondary ion detector by To characterized in that form to be able to push the secondary ion detector side.
The charged particle beam apparatus of the present invention scans a predetermined region on a sample placed on a sample stage with a charged particle beam, and distributes secondary ions generated from the sample between the sample and the objective lens. In a charged particle beam apparatus that is detected by a secondary ion detector provided and obtains a secondary ion image of the scanning region based on the detected secondary ions, the sample stage and Is electrically insulated and a correction electrode surrounding the side surface is attached, and a positive voltage whose size is controllable is applied to the correction electrode, so that the secondary ion detector is in front of the secondary ion detection surface. The electric field to be formed can be pushed toward the secondary ion detector.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 4 shows a schematic example of the main part of a scanning electron microscope showing an example of the present invention. In the figure, the same reference numerals as those used in FIG. 2 denote the same components.
[0023]
In FIG. 4, reference numeral 50A denotes a sample holder having a two-stage configuration, with the upper surface serving as the sample mounting surface, and the lower surface serving as the mounting surface of the correction electrode 31A having a shape surrounding the step. It has become.
[0024]
When the correction electrode 31A is placed on the lower surface of the sample holder 50A, the stage is moved so that its upper surface is flush with the sample surface, and the outermost region on the sample is on the optical axis O. , The guide tube 95 is formed to have such a width that a significant portion of the correction electrode 31A exists outside the extension of the guide tube 95 on the side opposite to the optical axis.
[0025]
When observing a region in the vicinity of the periphery of the semiconductor wafer, the stage is moved so that the region to be observed is on the optical axis, and the region is scanned with an electron beam in that state. Secondary electrons are detected by a secondary electron detector, and a secondary electron image of the sample is displayed on the display device based on the detected secondary electron signal.
[0026]
In this case, the correction electrode 31A is at the same potential (ground potential) as the sample 60, and the upper surface thereof is flush with the sample surface. Since a considerable portion of 31A exists, equipotential surface intervals between the secondary electron detector 90, the sample 60, and the correction electrode 31A are relatively equal, as shown in FIG. As in the case, secondary electrons from the sample 60 enter the scintillator 91 efficiently.
[0027]
FIG. 5 shows another schematic example of the main part of a scanning electron microscope showing an example of the present invention.
[0028]
In this example, the width of the lower surface of the sample holder 50B is considerably smaller than that of FIG. 4, and the width of the correction electrode 31B placed thereon via the insulating plate 32 is also reduced accordingly. It has become. That is, when the correction electrode 31B having a shape surrounding the step is placed on the lower surface of the sample holder 50B, the thickness is such that the upper surface thereof is flush with the sample surface, but the sample is moved by moving the stage. When the uppermost outer region is on the optical axis, the guide tube 95 is formed to have a width where at least a small portion of the correction electrode 31B exists on the outer side of the guide tube 95 on the side opposite to the optical axis.
[0029]
Further, a variable correction power source 33 is provided so that a negative DC high voltage can be applied to the correction electrode 31B.
[0030]
In such a configuration, when observing a region near the periphery of the semiconductor wafer, the stage is moved so that the region to be observed is on the optical axis, and in that state, the region is scanned with an electron beam, Secondary electrons generated from the sample by scanning are detected by a secondary electron detector, and a secondary electron image of the sample is displayed on the display device based on the detected secondary electron signal.
[0031]
In this case, the upper surface of the correction electrode 31B is flush with the sample surface, and there is at least a small portion of the correction electrode 31B outside the extension of the guide tube 95 of the secondary electron detector 90 on the side opposite to the optical axis. However, when a negative high voltage is applied to the correction electrode 31B, a negative electric field is formed on the surface of the auxiliary electrode 31B, and the positive electric field in front of the scintillator 91 of the secondary electron detector 90 is reduced to two. It will be pushed to the secondary electron detector 90 side. As a result, the potential distribution between the correction electrode 31B and the secondary electron detector 9 does not diverge greatly outward, and the equipotential surface spacing between the secondary electron detector 90, the sample 60, and the correction electrode 31A is The secondary electrons from the sample 60 enter the scintillator 91 efficiently as in the case shown in FIG.
[0032]
Such correction of the potential distribution is performed, for example, by controlling the negative voltage value from the variable correction power supply 32 while observing the contrast of the secondary electron image of the sample displayed on the display device.
[0033]
Such correction may be performed based on the analysis of the potential distribution.
[0034]
Further, when obtaining a secondary electron image of a region in the vicinity of the periphery of the semiconductor wafer, the potential distribution between the secondary electron detector 90 and the correction electrode 31B is somewhat different depending on the distance from the center even in the same peripheral region. Since it is different, obtain an appropriate correction voltage value for each area in the peripheral part by experiment etc. in advance, tabulate the position of the area and the correction voltage value, and when observing the actual area, position of the area to be observed from the table It is also possible to call a correction voltage value according to the above and automatically correct the potential distribution between the secondary electron detector 90 and the correction electrode 31B.
[0035]
FIG. 6 shows another schematic example of the main part of a scanning electron microscope showing an example of the present invention.
[0036]
In this example, the sample holder 50C has a one-stage configuration, and the diameter thereof is smaller than the diameter of the sample 60. A conical cylindrical correction electrode 31C surrounding the side surface is attached to the side surface of the sample holder 50C via an insulating plate 34, and the diameter of the entire sample holder 50C including the insulating plate 34 and the correction electrode 31C is illustrated. 5 is smaller than that shown in FIG.
[0037]
Also in this case, a variable correction power source 35 is provided so that a negative DC high voltage can be applied to the correction electrode 31C.
[0038]
In such a configuration, when observing a region near the periphery of the semiconductor wafer, the stage is moved so that the region to be observed is on the optical axis, and in that state, the region is scanned with an electron beam, Secondary electrons generated from the sample by scanning are detected by a secondary electron detector, and a secondary electron image of the sample is displayed on the display device based on the detected secondary electron signal.
[0039]
In this case, the upper surface of the correction electrode 31C is slightly lower than the sample surface, and the surface of the scintillator 91 of the secondary electron detector 90 and the side surface of the correction electrode 31C are substantially opposed to each other. 5, by applying a negative high voltage from the variable correction power supply 35 to the correction electrode 31C, a negative electric field is formed on the surface of the correction electrode 31C, and the front of the scintillator 91 of the secondary electron detector 90 This positive electric field is pushed to the secondary electron detector 90 side. As a result, the potential distribution between the correction electrode 31C and the secondary electron detector 9 does not diverge greatly outward, and the equipotential surface spacing between the secondary electron detector 90, the sample 60, and the correction electrode 31C is The secondary electrons from the sample 60 enter the scintillator 91 efficiently as in the case shown in FIG.
[0040]
In this case, it is necessary to apply a larger negative high voltage than in the case of FIG.
[0041]
Such potential distribution correction is performed, for example, by controlling the negative voltage value from the variable correction power supply 35 while observing the contrast of the secondary electron image of the sample displayed on the display device.
[0042]
Even in this case, when obtaining a secondary electron image of the region in the vicinity of the peripheral portion of the sample, the secondary electron detector 90 and the correction electrode 31C are separated even from the central portion even in the same peripheral region. Since the potential portion distribution is slightly different, an appropriate correction voltage value for each region in the peripheral portion is obtained in advance through experiments or the like, and the position of the region and the correction voltage value are tabulated. A correction voltage value corresponding to the position of the observation region may be called to automatically correct the potential distribution between the secondary electron detector 90 and the correction electrode 31.
[0043]
According to the present invention, in observation of a secondary electron image of a large sample such as a semiconductor wafer, the potential distribution around the secondary electron detector for capturing secondary electrons from the sample is expressed in the region near the periphery of the sample. The observation can be made to be almost the same as the case of observing the central portion of the sample and the region near the central portion, so the secondary electron image of any region of a large sample such as a semiconductor wafer has almost the same contrast. can get.
[0044]
When observing a sample such as a semiconductor wafer, in order to prevent destruction of the sample due to high-acceleration electron beam irradiation or to detect secondary electrons from a contact hole formed in the sample more efficiently. Although a negative high voltage may be applied to the sample, it goes without saying that the present invention can also be used in a scanning electron microscope having such a configuration.
[0045]
In the above example, the sample stage is formed of a conductive member and is at a ground potential. However, when using a sample stage formed of an insulating member, the sample should be dropped directly to the ground potential. Make it.
[0046]
In the above example, the scanning electron microscope is taken as an example, but the present invention can also be applied to an apparatus that scans a sample with an ion beam to obtain a secondary electron image.
[0047]
In addition, a secondary ion detector is provided in place of the secondary electron detector, the sample is scanned with an ion beam, and a secondary ion image is obtained based on the secondary ions detected by the secondary ion detector. It can also be applied to equipment that has been made to obtain [Brief description of the drawings]
FIG. 1 shows a schematic example of an electron microscope capable of observing a large sample.
FIG. 2 shows a partial detail view of FIG.
FIG. 3 shows a case where a peripheral portion of a sample is observed.
FIG. 4 shows a schematic example of a main part of a scanning electron microscope showing an example of the present invention.
FIG. 5 shows another schematic example of the main part of a scanning electron microscope showing an example of the present invention.
FIG. 6 shows another schematic example of the main part of a scanning electron microscope showing an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... Condensing lens 3 ... Deflection lens 4 ... Objective lens 5, 50, 50A, 50B, 50C ... Sample holder 6, 60 ... Sample 7 ... Central controller 8 ... Scan signal generation circuit 9, 90 ... Secondary Electron detector 10 ... Amplifier 11 ... Display device 12 ... Stage 13 ... Drive mechanism O ... Electronic optical system optical axis 21 ... Tracks 31A, 31B, 31C ... Correction electrodes 32, 34 ... Insulating plates 33, 35 ... Variable correction power supply 40 ... Magnetic pole piece 91 of objective lens ... Scintillator 92 ... Light guide 93 ... Photomultiplier tube 94 ... Ring electrode 95 ... Guide cylinder

Claims

A predetermined region on the sample placed on the sample stage is scanned with a charged particle beam, and secondary electrons generated from the sample by the scanning are detected by a secondary electron detector disposed between the sample and the objective lens. detected, a charged particle beam apparatus which forms so as to obtain a secondary electron image of the scanning area based on the secondary electrons the detected, the sample as the lower surface is formed in the peripheral portion of the sample stage base to form a twofold, placing the sample on the surface of the upper, on the surface of the lower, to place the correction electrode such as to surround a level difference between the surface and the upper surface of the lower stage The correction electrode placed on the lower surface has a thickness that is flush with the surface of the sample. When the outermost observation region on the sample is observed, the correction electrode is placed on the second surface of the secondary electron detector. Of the side surfaces perpendicular to the secondary electron detection surface, the extension line on the anti-electron optical axis side is the surface of the correction electrode on the secondary electron detector side It is arranged so as to intersect the charged particle beam device and the correction electrode and the sample was set to the same potential.

A predetermined region on the sample placed on the sample stage is scanned with a charged particle beam, and secondary electrons generated from the sample by the scanning are detected by a secondary electron detector disposed between the sample and the objective lens. In a charged particle beam apparatus configured to detect and obtain a secondary electron image of the scanning region based on the detected secondary electrons, the sample stage is formed in two stages, and the sample is placed on the upper surface And a correction electrode that is electrically insulated from the sample stage and surrounds the step between the lower surface and the upper surface is placed on the lower surface. The mounted correction electrode has a thickness that is flush with the surface of the sample. By applying a negative voltage whose size is controllable to the correction electrode, the correction electrode is fixed to the secondary electrode of the secondary electron detector. the electric field formed in the front next electron detection surface can push into the secondary electron detector side The charged particle beam device that form in.

A predetermined region on the sample placed on the sample stage is scanned with a charged particle beam, and secondary electrons generated from the sample by the scanning are detected by a secondary electron detector disposed between the sample and the objective lens. In a charged particle beam apparatus configured to detect and obtain a secondary electron image of the scanning region based on the detected secondary electrons, the side surface of the sample table is electrically insulated from the sample table and the side surface Install the like correction electrodes surrounding a, the correction electrode size is controllable negative voltage field the secondary electrons formed in the front secondary electron detection surface of the secondary electron detector by applying a A charged particle beam device that can be pushed to the detector side.

A correction voltage for obtaining a secondary electron image having substantially the same contrast regardless of the observation position in the sample is obtained in advance for each region position and tabulated, and the table is used to observe the secondary electron image of the region. The charged particle beam apparatus according to claim 2 or 3, wherein a correction voltage value corresponding to an observation region position is called and applied to a correction electrode.

A predetermined region on the sample placed on the sample stage is scanned with a charged particle beam, and secondary ions generated from the sample by the scanning are detected by a secondary ion detector disposed between the sample and the objective lens. detected, a charged particle beam apparatus which forms so as to obtain a secondary ion image of the scanning area based on the detected secondary ions, the sample as the lower surface is formed in the peripheral portion of the sample stage base to form a twofold, placing the sample on the surface of the upper, on the surface of the lower, to place the correction electrode such as to surround a level difference between the surface and the upper surface of the lower stage The correction electrode placed on the lower surface has a thickness that is flush with the surface of the sample. When the outermost observation region on the sample is observed, the correction electrode is placed on the second surface of the secondary ion detector. Of the side surface perpendicular to the secondary ion detection surface, the extension line on the anti-electron optical axis side is the secondary ion of the correction electrode. It is arranged so as to intersect the plane of the detector side, a charged particle beam device and the correction electrode and the sample was set to the same potential.

A predetermined region on the sample placed on the sample stage is scanned with a charged particle beam, and secondary ions generated from the sample by the scanning are detected by a secondary ion detector disposed between the sample and the objective lens. In a charged particle beam apparatus configured to detect and obtain a secondary ion image of the scanning region based on the detected secondary ions, the sample stage is formed in two stages, and the sample is placed on the upper surface. And a correction electrode that is electrically insulated from the sample stage and surrounds the step between the lower surface and the upper surface is placed on the lower surface. The mounted correction electrode has a thickness that is flush with the surface of the sample. By applying a positive voltage whose size can be controlled to the correction electrode, It forces the electric field formed in the following ion detection surface forward to the secondary ion detector side Doo is a charged particle beam device that forms as possible.

A predetermined region on the sample placed on the sample stage is scanned with a charged particle beam, and secondary ions generated from the sample by the scanning are detected by a secondary ion detector disposed between the sample and the objective lens. In a charged particle beam apparatus configured to detect and obtain a secondary ion image of the scanning region based on the detected secondary ions, the side surface of the sample table is electrically insulated from the sample table and the side surface A correction electrode that surrounds the secondary ion detector is applied, and a positive voltage whose size can be controlled is applied to the correction electrode, whereby an electric field formed in front of the secondary ion detection surface of the secondary ion detector is A charged particle beam device that can be pushed to the detector side.

A correction voltage for obtaining a secondary ion image having substantially the same contrast regardless of the observation position in the sample is obtained in advance for each area position and tabulated, and the table is used to observe the secondary ion image of the area. The charged particle beam apparatus according to claim 6 or 7, wherein a correction voltage value corresponding to an observation region position is called and applied to a correction electrode.

The charged particle beam apparatus according to claim 1, wherein the sample is a semiconductor wafer.