JP3895194B2

JP3895194B2 - Method for detecting relative dielectric constant of porous material and foreign substance inspection apparatus

Info

Publication number: JP3895194B2
Application number: JP2002047512A
Authority: JP
Inventors: 新一鈴木; 昌幸蜂谷; 良正大島; 幸雄宇都
Original assignee: Hitachi High Technologies Corp; Hitachi Ltd
Current assignee: Hitachi Ltd; Hitachi High Tech Corp
Priority date: 2002-02-25
Filing date: 2002-02-25
Publication date: 2007-03-22
Anticipated expiration: 2022-02-25
Also published as: JP2003247940A

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体ウェーハ等の被検査物の表面に存在する異物や結晶欠陥等（以下、これらを総称して異物と称す）を検査する異物検査装置、及びそれに用いられる多孔質材料の比誘電率検出方法に関する。
【０００２】
【従来の技術】
ＬＳＩ等の配線間を絶縁する配線間絶縁材料は、比誘電率の低いことが要求される。配線間絶縁材料の比誘電率が低い程、配線間容量が小さくなり、配線遅延が抑制されてＬＳＩの高速化が図られる。特に近年、配線の微細化により隣接する配線間容量の増加が顕著になってきたことから、多層配線構造の層間絶縁膜として低誘電率膜の開発が進められている。低誘電率膜の材料としては各種の物質が検討されているが、比誘電率を低くする手段の１つとして、内部に微細な空孔を設けた多孔質膜が注目されている。
【０００３】
多孔質膜を層間絶縁膜として半導体ウェーハの表面に形成する場合、多孔質膜の比誘電率を測定するか、あるいは多孔質膜の空孔の寸法、形状、密度等を測定することによって、多孔質膜の比誘電率を管理する必要がある。多孔質膜の比誘電率を測定する場合は、測定用のＴＥＧ（テストエレメントグループ）パターンを有する半導体ウェーハを用意し、ＴＥＧパターンに誘電率測定装置の触針を接触させて測定を行う。
【０００４】
一方、従来、多孔質膜の空孔の寸法、形状等を測定する方法として、ガス吸着法、陽電子消滅法、Ｘ線散漫散乱法等が知られている。ガス吸着法は、Ｎ₂ やＡｒガス等を空孔内部に吸着させた時の質量変化から空孔の寸法を測定するものであり、膜の外部へ通じガスを吸着できる空孔のみが測定可能である。陽電子消滅法は、陽電子を照射して生成した電子−陽電子対が空孔の壁に衝突して消滅するまでの時間から空孔の寸法を測定するものであり、陽電子発生源等の比較的大きな設備が必要である。これに対し、Ｘ線散漫散乱法は、Ｘ線を照射して空孔の界面で散乱したＸ線を検出することにより空孔の寸法や形状を測定するものであり、膜の外部へ通じていない空孔も測定でき、かつ、陽電子消滅法に比べて簡易な装置及び測定方法で実施することができる。
【０００５】
多孔質膜を層間絶縁膜として半導体ウェーハの表面に形成した後、多孔質膜の表面に異物がないかどうか、異物検査装置を用いて検査が行われる。異物検査装置は、被検査物の表面にレーザー光等の検査光を照射し、被検査物からの散乱光を検出することによって、被検査物の表面の異物を検査するものである。このような異物検査装置に関するものとしては、例えば、特開平９−３０４２８９号公報に記載のものがある。
【０００６】
【発明が解決しようとする課題】
従来、多孔質膜の比誘電率を測定する場合は、測定用のＴＥＧパターンを有する半導体ウェーハを測定の都度用意する必要があった。一方、多孔質膜の空孔の寸法や形状を測定するＸ線散漫散乱法は、陽電子消滅法に比べて簡易ではあるが、Ｘ線を用いるため装置が高価となり、また安全上の取り扱いに注意が必要である。さらに、多孔質膜を形成する工程で比誘電率を管理しても、多孔質膜を形成した後、表面に異物がないかどうかを別途検査する必要がある。
【０００７】
本発明は、多孔質材料の比誘電率を簡易な方法又は装置で検出することを目的とする。
【０００８】
本発明はまた、多孔質材料を用いた被検査物の異物検査と、多孔質材料の比誘電率検出とを同時に行うことを目的とする。
【０００９】
【課題を解決するための手段】
請求項１に記載された多孔質材料の比誘電率検出方法は、多孔質材料の複数の被検査物又はそれらのサンプルの比誘電率及び散乱光強度を測定することにより、予め被検査物の比誘電率と散乱光強度との相関関係を求め、被検査物の散乱光強度を測定して、予め求めた相関関係から被検査物の比誘電率を検出するものである。
【００１０】
また、請求項３に記載された異物検査装置は、検査光を多孔質材料の被検査物へ照射する投光手段と、検査光が被検査物で散乱された散乱光を受光して散乱光強度を検出する受光手段と、受光手段で検出された散乱光強度に基づいて被検査物の表面の異物を検出する異物検出手段と、被検査物の比誘電率と散乱光強度との相関関係を記憶し、受光手段で検出された散乱光強度に基づいて被検査物の比誘電率を検出する誘電率検出手段とを備えたものである。
【００１１】
多孔質材料の比誘電率は空孔が含まれる割合（空隙率）と相関があり、空隙率が高い程比誘電率は低くなる傾向にある。また、多孔質材料の散乱光強度は空隙率と相関があり、空隙率が高い程散乱光強度は強くなる傾向にある。従って、多孔質材料の比誘電率と散乱光強度との間には、空隙率を介して相関関係がある。本発明の比誘電率検出方法及び異物検査装置では、被検査物の散乱光強度を利用して、予め求めた比誘電率と散乱光強度との相関関係から被検査物の比誘電率を検出する。多孔質材料の比誘電率と散乱光強度との相関関係を求めた後は実際に比誘電率を測定する必要がなく、また高価で安全上の取り扱いが大変なＸ線装置等が必要ないので、多孔質材料の比誘電率を簡易な方法又は装置で検出することができる。さらに、本発明の異物検査装置では、散乱光強度に基づいて被検査物の表面の異物を検出する異物検出手段と、散乱光強度に基づいて被検査物の比誘電率を検出する誘電率検出手段とを備えることにより、多孔質材料を用いた被検査物の異物検査と多孔質材料の比誘電率検出とを同時に行うことができる。
【００１２】
請求項２に記載された多孔質材料の比誘電率検出方法は、多孔質材料の複数の被検査物又はそれらのサンプルの比誘電率、厚さ及び散乱光強度を測定することにより、予め被検査物の厚さに応じた比誘電率と散乱光強度との相関関係を求め、被検査物の厚さ情報を入力し、かつ、被検査物の散乱光強度を測定して、予め求めた相関関係から被検査物の比誘電率を検出するものである。
【００１３】
また、請求項４に記載された異物検査装置は、請求項３のものにおいて、誘電率検出手段が、被検査物の厚さに応じた比誘電率と散乱光強度との相関関係を記憶し、被検査物の厚さ情報を入力し、前記受光手段で検出された散乱光強度及び入力した厚さ情報に基づいて被検査物の比誘電率を検出するものである。
【００１４】
例えば半導体ウェーハの表面に層間絶縁膜として形成された多孔質膜のように、被検査物の多孔質材料が薄い場合、多孔質材料の厚さに応じて比誘電率と散乱光強度との相関関係が異なってくる。そこで、予め被検査物の厚さに応じた比誘電率と散乱光強度との相関関係を求めておくことによって、散乱光強度及び厚さ情報に基づいて厚さの異なる複数の被検査物の比誘電率を検出することができる。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態を添付図面に従って説明する。まず、図２は、多孔質膜を形成した半導体ウェーハの一部の断面図である。この半導体ウェーハ１０はパターン無しウェーハの例を示し、シリコンウェーハ１１の上面に層間絶縁膜として多孔質膜１２が形成されている。多孔質膜１２は、図に小円で示した空孔を多数有している。
【００１６】
図１は、本発明の一実施の形態による異物検査装置の概略構成を示す図である。異物検査装置５０は、図３に示すウェーハテーブル２及び投光系と、散乱光検出レンズ７ａ，７ｂ，７ｃ，７ｄ及び光電変換素子８ａ，８ｂ，８ｃ，８ｄを含む受光系と、アナログ処理回路５１と、誘電率検出回路５２と、異物検出回路５３とを含んで構成されている。
【００１７】
図３は、本発明の一実施の形態による異物検査装置の投光系及び受光系の概略構成を示す図である。本実施の形態は、検査光を被検査物の表面に対して斜めに照射する斜方照射投光系の例を示している。被検査物である半導体ウェーハ１０は、ウェーハテーブル２に搭載される。ウェーハテーブル２が破線矢印で示す方向に回転することにより、半導体ウェーハ１０が破線矢印で示す方向に回転して、半導体ウェーハ１０の検査領域１４が円周方向へ移動する。また、ウェーハテーブル２が図示しない移動機構によってＸ方向に移動することにより、検査領域１４が半径方向へ移動する。これにより、検査領域１４が半導体ウェーハ１０上でスパイラル状に移動し、半導体ウェーハ１０の表面全体が検査される。なお、ウェーハテーブル２は、ＸＹ移動機構を備え、検査領域１４をＸＹ方向に移動するものであってもよい。
【００１８】
異物検査装置５０の投光系は、レーザー光源３、波長板４、ビームエキスパンダ５、及び集光レンズ６を含んで構成されている。レーザー光源３は、検査光として所定の波長、例えば３６８ｎｍ，４８８ｎｍ，５３２ｎｍ等のレーザー光を発生する。レーザー光源３で発生されたレーザー光は、波長板４を通過してＰ偏光（又はＳ偏光）に偏光される。そして、ビームエキスパンダ５でビーム径が所望の大きさに拡大され、集光レンズ６によりレーザースポットとして半導体ウェーハ１０の検査領域１４へ照射される。投光系の光軸は半導体ウェーハ１０の表面に対して斜めに設定されており、図１及び図３ではレーザー光の照射角度θ１を半導体ウェーハ１０の表面を基準とした仰角で示している。
【００１９】
図４は、検査光の照射角度と多孔質膜の反射率との関係の一例を示す図である。図４は検査光がＰ偏光されたレーザー光の場合を示しており、多孔質膜の反射率は照射角度θ１に応じて変化する。そこで本実施の形態では、多孔質膜の反射率が一番低くなる照射角度、図４の例では３５度近辺の照射角度でレーザー光を半導体ウェーハ１０へ照射する。これにより、半導体ウェーハ１０の多孔質膜１２の表面で反射するレーザー光が少なくなり、多孔質膜１２の表面下へ透過するレーザー光の量が多くなる。
【００２０】
図１において、半導体ウェーハ１０へ照射されたレーザー光Ｌのうち、多孔質膜１２の表面下へ透過したレーザー光は多孔質膜１２の内部の空孔の界面で散乱されて、散乱光Ｄが多孔質膜１２の上面へ射出される。図３に示すように、半導体ウェーハ１０の上面には検査領域１４を中心とした円周方向に４組の受光系が設けられており、多孔質膜１２の上面へ射出された散乱光を受光する。受光系の散乱光検出レンズ７ａ，７ｂ，７ｃ，７ｄは、散乱光を集光して、光電変換素子８ａ，８ｂ，８ｃ，８ｄの受光面に集束させる。光電変換素子８ａ，８ｂ，８ｃ，８ｄは、例えば光電子増倍管で構成され、受光面で受光した散乱光の強度を電気信号に変換して出力する。各受光系の光軸は半導体ウェーハ１０の表面に対して斜めに設定されており、図３ではその角度θａ，θｂ，θｃ，θｄをそれぞれ半導体ウェーハ１０の表面を基準とした仰角で示している。本実施の形態は、角度θａ，θｃが小さい低角度受光系と、角度θｂ，θｄが大きい高角度受光系とを設けた例を示している。これらの受光系は、特開平９−３０４２８９号公報に開示されているものと同様である。なお、受光系は、必ずしも４組である必要はなく、これより少なくても多くてもよい。
【００２１】
図１において、光電変換素子８ａ，８ｂ，８ｃ，８ｄから出力された散乱光強度を示す電気信号は、アナログ処理回路５１及び異物検出回路５３へ入力される。アナログ処理回路５１は、光電変換素子８ａ，８ｂ，８ｃ，８ｄから入力した電気信号について雑音除去やディジタル化等の前処理を行って、誘電率検出回路５２へ出力する。誘電率検出回路５２は、後述する方法によって求めた多孔質膜１２の膜厚に応じた比誘電率と散乱光強度との相関関係を計算式として記憶しており、多孔質膜１２の膜厚情報を入力して、アナログ処理回路５１の出力データと膜厚情報とから多孔質膜１２の比誘電率を計算して出力する。多孔質膜１２の膜厚情報は、多孔質膜１２を形成する工程の管理情報から得ることができる。
【００２２】
一方、多孔質膜１２の表面に異物が存在する場合、半導体ウェーハ１０へ照射されたレーザー光Ｌは多孔質膜１２の表面の異物で散乱されて、散乱光が発生する。従って、受光系の散乱光検出レンズ７ａ，７ｂ，７ｃ，７ｄ及び光電変換素子８ａ，８ｂ，８ｃ，８ｄにより検出された散乱光強度が変化する。異物検出回路５３は、光電変換素子８ａ，８ｂ，８ｃ，８ｄから入力した散乱光強度を示す電気信号に基づいて、半導体ウェーハ１０の表面の異物検出処理を行う。この異物検出処理は、例えば、特開平９−３０４２８９号公報に開示されているものが利用できる。なお、異物検出処理に必要な電気信号の前処理が比誘電率検出に必要な前処理と同じ場合、異物検出回路５３はアナログ処理回路５１の出力を入力してもよい。
【００２３】
図５は、本発明の他の実施の形態による異物検査装置の投光系及び受光系の概略構成を示す図である。本実施の形態は、検査光を被検査物の表面に対して垂直に照射する垂直照射投光系の例を示している。図３に示した実施の形態との相違は、投光系が波長板４を有さず、投光系の光軸が半導体ウェーハ１０の表面に対して垂直に設定されている点である。その他の構成は図３に示した実施の形態と同様である。本実施の形態では、偏光されていないレーザー光が半導体ウェーハ１０の表面に垂直に照射されるので、半導体ウェーハ１０の多孔質膜１２の表面下へ透過するレーザー光の量が多くなる。
【００２４】
次に、多孔質膜の膜厚に応じた比誘電率と散乱光強度との相関関係を求める方法の一例を説明する。図６（ａ）は比誘電率測定用の半導体ウェーハの一部の断面図、図６（ｂ）は膜厚及び散乱光強度測定用の半導体ウェーハの一部の断面図である。比誘電率測定用の半導体ウェーハ２０では、シリコンウェーハ２１の上面に比誘電率測定用のＴＥＧパターン２３を形成し、その上に多孔質膜２２を形成する。一方、膜厚及び散乱光強度測定用の半導体ウェーハ３０では、シリコンウェーハ３１の上面に多孔質膜３２のみを形成する。これらの多孔質膜２２，３２を同時に着工して形成することにより、多孔質膜２２，３２の膜厚ｔを同じにしたものを、各種の膜厚について作成する。
【００２５】
図７は、多孔質膜の膜厚に応じた比誘電率と散乱光強度との相関関係を求める装置の概略構成を示す図である。誘電率測定装置６０は、比誘電率測定用の半導体ウェーハ２０の２つのＴＥＧパターン２３に触針を接触させて多孔質膜２２の比誘電率を測定し、測定したデータを演算処理装置８０へ出力する。膜厚測定装置７０は、膜厚及び散乱光強度測定用の半導体ウェーハ３０の多孔質膜３２の膜厚を測定し、測定したデータを演算処理装置８０へ出力する。異物検査装置５０は、膜厚及び散乱光強度測定用の半導体ウェーハ３０の多孔質膜３２の散乱光強度を測定し、測定したデータをアナログ処理回路５１から演算処理装置８０へ出力する。演算処理装置８０は、各種の膜厚についての誘電率測定装置６０からの比誘電率のデータ、膜厚測定装置７０からの膜厚のデータ、及び異物検査装置５０からの散乱光強度のデータを入力し、これらのデータを演算処理することによって、膜厚に応じた比誘電率と散乱光強度との相関関係を示す計算式を作成する。
【００２６】
さらに、多孔質膜の膜厚に応じた比誘電率と散乱光強度との相関関係を求める方法の他の例を説明する。一般に、半導体ウェーハの異物検査装置には、図２に示したパターン無しウェーハを検査する異物検査装置と、パターン付きウェーハを検査する異物検査装置とがある。そして、パターン付きウェーハを検査する異物検査装置には、検査領域中でパターンが存在する領域を認識する機能が備えられている。このような機能を備えた異物検査装置を用いると、比誘電率測定用の半導体ウェーハ２０で散乱光強度も測定することができる。
【００２７】
図８（ａ）は比誘電率測定用の半導体ウェーハの上面図、図８（ｂ）はそのチップの上面図である。比誘電率測定用の半導体ウェーハ２０の各チップ４０には、ＴＥＧパターン２３が設けられている。パターン付きウェーハを検査する異物検査装置は、チップ４０のＴＥＧパターン２３が存在する領域を認識して、それを含む非検査領域４１を設定し、非検査領域４１については散乱光強度の測定を行わない。従って、図７で異物検査装置５０としてパターン付きウェーハを検査する異物検査装置を用い、膜厚及び散乱光強度測定用の半導体ウェーハ３０の代わりに比誘電率測定用の半導体ウェーハ２０でＴＥＧパターン２３が存在しない領域について多孔質膜の散乱光強度を測定すると、同一の半導体ウェーハで比誘電率と散乱光強度との相関関係を求めることができる。
【００２８】
以上説明した実施の形態によれば、半導体ウェーハの異物検査装置が本来備えている投光系及び受光系を利用して、半導体ウェーハの多孔質膜の比誘電率を検出することができる。
【００２９】
以上説明した実施の形態では、検査光としてレーザー光を使用していたが、白色光、紫外光等であってもよい。多孔質材料は、大気中に放置しておくと空孔に水蒸気を吸着して水分を吸収しやすい材料であり、水分吸収によって材料の特性に変化を起こすことがある。本発明において、検査光として水分による減衰が大きい波長の光を用い、散乱光強度の減衰を測定すると、多孔質材料の水分吸収量を検出することができる。これにより、例えば、半導体ウェーハの表面に多孔質膜を形成した後、多孔質膜の水分吸収量に基づいて次工程の着工可否を判断することが可能となる。
【００３０】
以上説明した実施の形態では、誘電率検出回路５２が多孔質膜の膜厚に応じた比誘電率と散乱光強度との相関関係を計算式として記憶しており、散乱光強度と膜厚情報とから多孔質膜の比誘電率を計算していたが、多孔質膜の膜厚に応じた比誘電率と散乱光強度との相関関係をデータとして記憶しておき、散乱光強度と膜厚情報とを基に記憶した比誘電率のデータを検索するようにしてもよい。
【００３１】
以上説明した実施の形態では、半導体ウェーハ上に形成された多孔質膜を例として説明したが、本発明はこれに限らず各種の多孔質材料に適用することができる。そして、多孔質材料が所定以上の厚さで、比誘電率と散乱光強度との相関関係が被検査物の厚さによらない場合は、被検査物の厚さを考慮する必要がない。
【００３２】
【発明の効果】
本発明の多孔質材料の比誘電率測定方法及び異物検査装置によれば、多孔質材料の比誘電率と散乱光強度との相関関係を求めた後は実際に比誘電率を測定する必要がなく、また高価で安全上の取り扱いが大変なＸ線装置等が必要ないので、多孔質材料の比誘電率を簡易な方法又は装置で検出することができる。
【００３３】
また、本発明の異物検査装置によれば、多孔質材料を用いた被検査物の異物検査と、多孔質材料の比誘電率検出とを同時に行うことができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態による異物検査装置の概略構成を示す図である。
【図２】多孔質膜を形成した半導体ウェーハの一部の断面図である。
【図３】本発明の一実施の形態による異物検査装置の投光系及び受光系の概略構成を示す図である。
【図４】検査光の照射角度と多孔質膜の反射率との関係の一例を示す図である。
【図５】本発明の他の実施の形態による異物検査装置の投光系及び受光系の概略構成を示す図である。
【図６】（ａ）は比誘電率測定用の半導体ウェーハの一部の断面図、（ｂ）は膜厚及び散乱光強度測定用の半導体ウェーハの一部の断面図である。
【図７】多孔質膜の膜厚に応じた比誘電率と散乱光強度との相関関係を求める装置の概略構成を示す図である。
【図８】（ａ）は比誘電率測定用の半導体ウェーハの上面図、（ｂ）はそのチップの上面図である。
【符号の説明】
２…ウェーハテーブル、３…レーザー光源、４…波長板、５…ビームエキスパンダ、６…集光レンズ、７ａ，７ｂ，７ｃ，７ｄ…散乱光検出レンズ、８ａ，８ｂ，８ｃ，８ｄ…光電変換素子、１０，２０，３０…半導体ウェーハ、１１，２１，３１…シリコンウェーハ、１２，２２，３２…多孔質膜、１４…検査領域、２３…ＴＥＧパターン、４０…チップ、４１…非検査領域、５０…異物検査装置、５１…アナログ処理回路、５２…誘電率検出回路、５３…異物検出回路、６０…誘電率測定装置、７０…膜厚測定装置、８０…演算処理装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a foreign matter inspection apparatus for inspecting foreign matter and crystal defects (hereinafter collectively referred to as foreign matter) present on the surface of an inspection object such as a semiconductor wafer, and a relative dielectric of a porous material used therefor It relates to a rate detection method.
[0002]
[Prior art]
The inter-wiring insulating material that insulates the wiring of LSI or the like is required to have a low relative dielectric constant. The lower the relative dielectric constant of the inter-wiring insulating material, the smaller the inter-wiring capacitance, and the wiring delay is suppressed, thereby speeding up the LSI. In particular, in recent years, the increase in capacitance between adjacent wirings has become remarkable due to the miniaturization of wiring, and therefore, development of a low dielectric constant film as an interlayer insulating film of a multilayer wiring structure has been promoted. Various materials have been studied as a material for the low dielectric constant film. However, as one means for reducing the relative dielectric constant, a porous film having fine pores therein has attracted attention.
[0003]
When forming a porous film on the surface of a semiconductor wafer as an interlayer insulating film, the porous film can be measured by measuring the relative dielectric constant of the porous film or by measuring the size, shape, density, etc. of the pores of the porous film. It is necessary to manage the relative dielectric constant of the material film. When measuring the relative dielectric constant of the porous film, a semiconductor wafer having a TEG (test element group) pattern for measurement is prepared, and measurement is performed by bringing a stylus of a dielectric constant measuring device into contact with the TEG pattern.
[0004]
On the other hand, conventionally, gas adsorption method, positron annihilation method, X-ray diffuse scattering method and the like are known as methods for measuring the size and shape of the pores of the porous film. The gas adsorption method measures the dimensions of the vacancies from the change in mass when N ₂ or Ar gas is adsorbed inside the vacancies. It is. The positron annihilation method measures the size of a hole from the time until the electron-positron pair generated by positron irradiation collides with the wall of the hole and disappears. Equipment is required. In contrast, the diffuse X-ray scattering method measures the size and shape of the holes by irradiating the X-rays and detecting the X-rays scattered at the interface of the holes, and leads to the outside of the film. It is possible to measure vacancies that are not present and can be carried out with a simpler apparatus and measurement method than the positron annihilation method.
[0005]
After the porous film is formed on the surface of the semiconductor wafer as an interlayer insulating film, it is inspected by using a foreign substance inspection apparatus for the presence of foreign substances on the surface of the porous film. The foreign matter inspection apparatus inspects the foreign matter on the surface of the inspection object by irradiating the surface of the inspection object with inspection light such as laser light and detecting scattered light from the inspection object. An example of such a foreign matter inspection apparatus is disclosed in JP-A-9-304289.
[0006]
[Problems to be solved by the invention]
Conventionally, when measuring the relative dielectric constant of a porous film, it has been necessary to prepare a semiconductor wafer having a TEG pattern for measurement for each measurement. On the other hand, the X-ray diffuse scattering method, which measures the size and shape of the pores in the porous membrane, is simpler than the positron annihilation method. is required. Furthermore, even if the relative dielectric constant is controlled in the step of forming the porous film, it is necessary to separately check whether or not there is a foreign substance on the surface after forming the porous film.
[0007]
An object of the present invention is to detect the relative dielectric constant of a porous material with a simple method or apparatus.
[0008]
Another object of the present invention is to simultaneously perform a foreign matter inspection of an inspection object using a porous material and a relative dielectric constant detection of the porous material.
[0009]
[Means for Solving the Problems]
The method for detecting the relative dielectric constant of a porous material according to claim 1 is a method of measuring the relative dielectric constant and scattered light intensity of a plurality of objects to be inspected of a porous material or samples thereof in advance. The correlation between the relative dielectric constant and the scattered light intensity is obtained, the scattered light intensity of the inspection object is measured, and the relative dielectric constant of the inspection object is detected from the previously obtained correlation.
[0010]
According to a third aspect of the present invention, there is provided a foreign object inspection apparatus that includes a light projecting unit that irradiates an inspection light onto an inspection object made of a porous material, and a scattered light received by the inspection light scattered by the inspection object. Light receiving means for detecting the intensity, foreign object detecting means for detecting foreign matter on the surface of the inspection object based on the scattered light intensity detected by the light receiving means, and a correlation between the relative permittivity of the inspection object and the scattered light intensity And a dielectric constant detecting means for detecting the relative dielectric constant of the object to be inspected based on the scattered light intensity detected by the light receiving means.
[0011]
The relative dielectric constant of the porous material has a correlation with the ratio of voids (porosity), and the higher the porosity, the lower the relative dielectric constant tends to be. Further, the scattered light intensity of the porous material has a correlation with the porosity, and the higher the porosity, the stronger the scattered light intensity tends to be. Therefore, there is a correlation between the relative dielectric constant of the porous material and the scattered light intensity through the porosity. In the relative dielectric constant detection method and the foreign matter inspection apparatus of the present invention, the relative dielectric constant of the inspection object is detected from the correlation between the relative dielectric constant and the scattered light intensity obtained in advance using the scattered light intensity of the inspection object. To do. After obtaining the correlation between the relative permittivity of the porous material and the scattered light intensity, it is not necessary to actually measure the relative permittivity, and there is no need for an expensive X-ray apparatus that is difficult to handle safely. The relative dielectric constant of the porous material can be detected by a simple method or apparatus. Furthermore, in the foreign matter inspection apparatus of the present invention, foreign matter detection means for detecting foreign matter on the surface of the inspection object based on the scattered light intensity, and dielectric constant detection for detecting the relative dielectric constant of the inspection subject based on the scattered light intensity By providing the means, it is possible to simultaneously perform the foreign substance inspection of the inspection object using the porous material and the relative dielectric constant detection of the porous material.
[0012]
The method for detecting the relative dielectric constant of a porous material according to claim 2 is a method of measuring the relative dielectric constant, thickness, and scattered light intensity of a plurality of objects to be inspected or samples of the porous material in advance. The correlation between the relative permittivity corresponding to the thickness of the inspection object and the scattered light intensity is obtained, the thickness information of the inspection object is input, and the scattered light intensity of the inspection object is measured and obtained in advance. The relative permittivity of the object to be inspected is detected from the correlation.
[0013]
According to a fourth aspect of the present invention, in the foreign substance inspection apparatus according to the third aspect, the dielectric constant detecting means stores the correlation between the relative dielectric constant according to the thickness of the object to be inspected and the scattered light intensity. The thickness information of the inspection object is input, and the relative dielectric constant of the inspection object is detected based on the scattered light intensity detected by the light receiving means and the input thickness information.
[0014]
For example, when the porous material of the object to be inspected is thin, such as a porous film formed as an interlayer insulating film on the surface of a semiconductor wafer, the correlation between the relative permittivity and the scattered light intensity depending on the thickness of the porous material The relationship will be different. Therefore, by obtaining a correlation between the relative permittivity corresponding to the thickness of the object to be inspected and the scattered light intensity in advance, a plurality of objects having different thicknesses based on the scattered light intensity and the thickness information are obtained. The relative dielectric constant can be detected.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, FIG. 2 is a sectional view of a part of a semiconductor wafer on which a porous film is formed. The semiconductor wafer 10 is an example of an unpatterned wafer, and a porous film 12 is formed on the upper surface of a silicon wafer 11 as an interlayer insulating film. The porous membrane 12 has a large number of pores indicated by small circles in the figure.
[0016]
FIG. 1 is a diagram showing a schematic configuration of a foreign matter inspection apparatus according to an embodiment of the present invention. The foreign matter inspection apparatus 50 includes a wafer table 2 and a light projecting system shown in FIG. 3, a light receiving system including scattered light detection lenses 7a, 7b, 7c, and 7d and photoelectric conversion elements 8a, 8b, 8c, and 8d, and an analog processing circuit. 51, a dielectric constant detection circuit 52, and a foreign matter detection circuit 53.
[0017]
FIG. 3 is a diagram showing a schematic configuration of a light projecting system and a light receiving system of the foreign matter inspection apparatus according to the embodiment of the present invention. The present embodiment shows an example of an oblique irradiation projection system that irradiates the inspection light obliquely with respect to the surface of the inspection object. A semiconductor wafer 10 that is an object to be inspected is mounted on the wafer table 2. When the wafer table 2 rotates in the direction indicated by the broken line arrow, the semiconductor wafer 10 rotates in the direction indicated by the broken line arrow, and the inspection region 14 of the semiconductor wafer 10 moves in the circumferential direction. Further, when the wafer table 2 is moved in the X direction by a moving mechanism (not shown), the inspection region 14 is moved in the radial direction. As a result, the inspection region 14 moves spirally on the semiconductor wafer 10 and the entire surface of the semiconductor wafer 10 is inspected. The wafer table 2 may include an XY moving mechanism and move the inspection area 14 in the XY direction.
[0018]
The light projecting system of the foreign substance inspection apparatus 50 includes a laser light source 3, a wave plate 4, a beam expander 5, and a condenser lens 6. The laser light source 3 generates laser light having a predetermined wavelength, for example, 368 nm, 488 nm, 532 nm, etc. as inspection light. The laser light generated by the laser light source 3 passes through the wave plate 4 and is polarized into P-polarized light (or S-polarized light). The beam expander 5 enlarges the beam diameter to a desired size, and the condenser lens 6 irradiates the inspection region 14 of the semiconductor wafer 10 as a laser spot. The optical axis of the light projecting system is set obliquely with respect to the surface of the semiconductor wafer 10, and in FIGS. 1 and 3, the irradiation angle θ <b> 1 of the laser beam is shown as an elevation angle with respect to the surface of the semiconductor wafer 10.
[0019]
FIG. 4 is a diagram illustrating an example of the relationship between the irradiation angle of the inspection light and the reflectance of the porous film. FIG. 4 shows the case where the inspection light is P-polarized laser light, and the reflectance of the porous film changes according to the irradiation angle θ1. Therefore, in the present embodiment, the semiconductor wafer 10 is irradiated with laser light at an irradiation angle at which the reflectance of the porous film is the lowest, in the example of FIG. Thereby, the amount of laser light reflected on the surface of the porous film 12 of the semiconductor wafer 10 is reduced, and the amount of laser light transmitted below the surface of the porous film 12 is increased.
[0020]
In FIG. 1, among the laser light L irradiated to the semiconductor wafer 10, the laser light transmitted below the surface of the porous film 12 is scattered at the interface of the pores inside the porous film 12, and the scattered light D is Injected onto the upper surface of the porous membrane 12. As shown in FIG. 3, four sets of light receiving systems are provided on the upper surface of the semiconductor wafer 10 in the circumferential direction with the inspection region 14 as the center, and the scattered light emitted to the upper surface of the porous film 12 is received. To do. The scattered light detection lenses 7a, 7b, 7c and 7d of the light receiving system collect the scattered light and focus it on the light receiving surfaces of the photoelectric conversion elements 8a, 8b, 8c and 8d. The photoelectric conversion elements 8a, 8b, 8c, and 8d are configured by, for example, photomultiplier tubes, and convert the intensity of scattered light received by the light receiving surface into an electrical signal and output it. The optical axis of each light receiving system is set obliquely with respect to the surface of the semiconductor wafer 10, and in FIG. 3, the angles .theta.a, .theta.b, .theta.c, and .theta.d are shown as elevation angles with respect to the surface of the semiconductor wafer 10, respectively. . This embodiment shows an example in which a low-angle light receiving system with small angles θa and θc and a high-angle light receiving system with large angles θb and θd are provided. These light receiving systems are the same as those disclosed in JP-A-9-304289. Note that the number of light receiving systems is not necessarily four, and may be smaller or larger.
[0021]
In FIG. 1, electrical signals indicating scattered light intensity output from the photoelectric conversion elements 8 a, 8 b, 8 c, and 8 d are input to the analog processing circuit 51 and the foreign matter detection circuit 53. The analog processing circuit 51 performs preprocessing such as noise removal and digitization on the electrical signals input from the photoelectric conversion elements 8 a, 8 b, 8 c, and 8 d and outputs them to the dielectric constant detection circuit 52. The dielectric constant detection circuit 52 stores a correlation between the relative dielectric constant and the scattered light intensity corresponding to the film thickness of the porous film 12 obtained by a method described later as a calculation formula, and the film thickness of the porous film 12. Information is input, and the relative dielectric constant of the porous film 12 is calculated from the output data of the analog processing circuit 51 and the film thickness information and output. The film thickness information of the porous film 12 can be obtained from the management information of the process of forming the porous film 12.
[0022]
On the other hand, when a foreign substance exists on the surface of the porous film 12, the laser beam L irradiated to the semiconductor wafer 10 is scattered by the foreign substance on the surface of the porous film 12, and scattered light is generated. Therefore, the scattered light intensity detected by the scattered light detection lenses 7a, 7b, 7c, 7d and the photoelectric conversion elements 8a, 8b, 8c, 8d of the light receiving system changes. The foreign matter detection circuit 53 performs foreign matter detection processing on the surface of the semiconductor wafer 10 based on an electrical signal indicating the scattered light intensity input from the photoelectric conversion elements 8a, 8b, 8c, and 8d. As this foreign matter detection processing, for example, the one disclosed in Japanese Patent Laid-Open No. 9-304289 can be used. When the preprocessing of the electrical signal necessary for the foreign object detection process is the same as the preprocess necessary for the relative dielectric constant detection, the foreign object detection circuit 53 may input the output of the analog processing circuit 51.
[0023]
FIG. 5 is a diagram showing a schematic configuration of a light projecting system and a light receiving system of a foreign object inspection apparatus according to another embodiment of the present invention. The present embodiment shows an example of a vertical irradiation projection system that irradiates inspection light perpendicularly to the surface of an object to be inspected. The difference from the embodiment shown in FIG. 3 is that the light projecting system does not have the wave plate 4, and the optical axis of the light projecting system is set perpendicular to the surface of the semiconductor wafer 10. Other configurations are the same as those of the embodiment shown in FIG. In the present embodiment, since the unpolarized laser light is irradiated perpendicularly to the surface of the semiconductor wafer 10, the amount of laser light transmitted below the surface of the porous film 12 of the semiconductor wafer 10 increases.
[0024]
Next, an example of a method for obtaining the correlation between the relative dielectric constant corresponding to the film thickness of the porous film and the scattered light intensity will be described. FIG. 6A is a sectional view of a part of a semiconductor wafer for measuring relative permittivity, and FIG. 6B is a sectional view of a part of the semiconductor wafer for measuring film thickness and scattered light intensity. In the semiconductor wafer 20 for measuring the relative dielectric constant, the TEG pattern 23 for measuring the relative dielectric constant is formed on the upper surface of the silicon wafer 21, and the porous film 22 is formed thereon. On the other hand, in the semiconductor wafer 30 for measuring the film thickness and scattered light intensity, only the porous film 32 is formed on the upper surface of the silicon wafer 31. By forming these porous films 22 and 32 simultaneously and forming them, the same film thickness t of the porous films 22 and 32 is created for various film thicknesses.
[0025]
FIG. 7 is a diagram showing a schematic configuration of an apparatus for obtaining the correlation between the relative dielectric constant and the scattered light intensity according to the thickness of the porous film. The dielectric constant measuring device 60 measures the relative dielectric constant of the porous film 22 by bringing the stylus into contact with the two TEG patterns 23 of the semiconductor wafer 20 for measuring the relative dielectric constant, and sends the measured data to the arithmetic processing unit 80. Output. The film thickness measuring device 70 measures the film thickness and the film thickness of the porous film 32 of the semiconductor wafer 30 for measuring scattered light intensity, and outputs the measured data to the arithmetic processing device 80. The foreign matter inspection device 50 measures the scattered light intensity of the porous film 32 of the semiconductor wafer 30 for measuring the film thickness and scattered light intensity, and outputs the measured data from the analog processing circuit 51 to the arithmetic processing device 80. The arithmetic processing unit 80 uses the relative dielectric constant data from the dielectric constant measuring device 60, the film thickness data from the film thickness measuring device 70, and the scattered light intensity data from the foreign matter inspection device 50 for various film thicknesses. By inputting and calculating these data, a calculation formula showing the correlation between the relative permittivity corresponding to the film thickness and the scattered light intensity is created.
[0026]
Furthermore, another example of a method for obtaining the correlation between the relative dielectric constant corresponding to the film thickness of the porous film and the scattered light intensity will be described. 2. Description of the Related Art Generally, semiconductor wafer foreign matter inspection apparatuses include a foreign matter inspection apparatus that inspects a non-patterned wafer shown in FIG. 2 and a foreign matter inspection apparatus that inspects a patterned wafer. A foreign matter inspection apparatus that inspects a wafer with a pattern has a function of recognizing a region where a pattern exists in the inspection region. If a foreign substance inspection apparatus having such a function is used, the scattered light intensity can also be measured with the semiconductor wafer 20 for measuring the relative dielectric constant.
[0027]
FIG. 8A is a top view of a semiconductor wafer for measuring relative permittivity, and FIG. 8B is a top view of the chip. A TEG pattern 23 is provided on each chip 40 of the semiconductor wafer 20 for measuring the relative dielectric constant. The foreign matter inspection apparatus for inspecting a wafer with a pattern recognizes an area where the TEG pattern 23 of the chip 40 is present, sets a non-inspection area 41 including the area, and measures the scattered light intensity for the non-inspection area 41. Absent. Accordingly, in FIG. 7, a foreign substance inspection apparatus for inspecting a patterned wafer is used as the foreign substance inspection apparatus 50, and the TEG pattern 23 is used in the semiconductor wafer 20 for measuring the relative dielectric constant instead of the semiconductor wafer 30 for measuring the film thickness and scattered light intensity. When the scattered light intensity of the porous film is measured in a region where no exists, the correlation between the relative dielectric constant and the scattered light intensity can be obtained from the same semiconductor wafer.
[0028]
According to the embodiment described above, the relative permittivity of the porous film of the semiconductor wafer can be detected by using the light projecting system and the light receiving system that are originally provided in the semiconductor wafer foreign matter inspection apparatus.
[0029]
In the embodiment described above, laser light is used as inspection light, but white light, ultraviolet light, or the like may be used. A porous material is a material that easily absorbs moisture by adsorbing water vapor into the pores when left in the atmosphere, and the characteristics of the material may change due to moisture absorption. In the present invention, when light having a wavelength that is largely attenuated by moisture is used as inspection light and the attenuation of scattered light intensity is measured, the moisture absorption amount of the porous material can be detected. Thereby, for example, after forming the porous film on the surface of the semiconductor wafer, it is possible to determine whether or not the next process can be started based on the water absorption amount of the porous film.
[0030]
In the embodiment described above, the dielectric constant detection circuit 52 stores the correlation between the relative dielectric constant according to the film thickness of the porous film and the scattered light intensity as a calculation formula, and the scattered light intensity and film thickness information. The relative permittivity of the porous film was calculated from the above, but the correlation between the relative permittivity corresponding to the thickness of the porous film and the scattered light intensity was stored as data, and the scattered light intensity and the film thickness were stored. You may make it search the data of the dielectric constant memorize | stored based on information.
[0031]
In the embodiment described above, the porous film formed on the semiconductor wafer has been described as an example. However, the present invention is not limited to this and can be applied to various porous materials. When the porous material has a predetermined thickness or more and the correlation between the relative dielectric constant and the scattered light intensity does not depend on the thickness of the inspection object, it is not necessary to consider the thickness of the inspection object.
[0032]
【The invention's effect】
According to the method for measuring the relative permittivity of the porous material and the foreign matter inspection apparatus of the present invention, after obtaining the correlation between the relative permittivity of the porous material and the scattered light intensity, it is necessary to actually measure the relative permittivity. In addition, an X-ray apparatus or the like that is expensive and difficult to handle safely is not required, so that the relative dielectric constant of the porous material can be detected by a simple method or apparatus.
[0033]
In addition, according to the foreign matter inspection apparatus of the present invention, foreign matter inspection of an inspection object using a porous material and relative dielectric constant detection of the porous material can be performed simultaneously.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a foreign substance inspection apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a part of a semiconductor wafer on which a porous film is formed.
FIG. 3 is a diagram showing a schematic configuration of a light projecting system and a light receiving system of a foreign matter inspection apparatus according to an embodiment of the present invention.
FIG. 4 is a diagram showing an example of the relationship between the irradiation angle of inspection light and the reflectance of a porous film.
FIG. 5 is a diagram showing a schematic configuration of a light projecting system and a light receiving system of a foreign object inspection apparatus according to another embodiment of the present invention.
6A is a cross-sectional view of a part of a semiconductor wafer for measuring relative permittivity, and FIG. 6B is a cross-sectional view of a part of the semiconductor wafer for measuring film thickness and scattered light intensity.
FIG. 7 is a diagram showing a schematic configuration of an apparatus for obtaining a correlation between a relative dielectric constant and a scattered light intensity according to the thickness of a porous film.
8A is a top view of a semiconductor wafer for measuring a relative dielectric constant, and FIG. 8B is a top view of the chip.
[Explanation of symbols]
2 ... Wafer table, 3 ... Laser light source, 4 ... Wave plate, 5 ... Beam expander, 6 ... Condensing lens, 7a, 7b, 7c, 7d ... Scattered light detection lens, 8a, 8b, 8c, 8d ... Photoelectric conversion Element 10, 20, 30 ... Semiconductor wafer, 11, 21, 31 ... Silicon wafer, 12, 22, 32 ... Porous film, 14 ... Inspection area, 23 ... TEG pattern, 40 ... Chip, 41 ... Non-inspection area, DESCRIPTION OF SYMBOLS 50 ... Foreign substance inspection apparatus, 51 ... Analog processing circuit, 52 ... Dielectric constant detection circuit, 53 ... Foreign substance detection circuit, 60 ... Dielectric constant measuring apparatus, 70 ... Film thickness measuring apparatus, 80 ... Arithmetic processing apparatus

Claims

By measuring the relative permittivity and scattered light intensity of a plurality of objects to be inspected of a porous material or their samples, the correlation between the relative permittivity of the object to be inspected and the scattered light intensity is obtained in advance.
A method for detecting a relative dielectric constant of a porous material, comprising: measuring a scattered light intensity of an object to be inspected, and detecting a relative dielectric constant of the object to be inspected from a correlation obtained in advance.

Correlation between the relative permittivity and scattered light intensity corresponding to the thickness of the test object in advance by measuring the relative permittivity, thickness and scattered light intensity of a plurality of test objects or samples of the porous material Seeking a relationship
A porous material characterized by inputting thickness information of an inspection object and measuring a scattered light intensity of the inspection object and detecting a relative dielectric constant of the inspection object from a previously obtained correlation Specific permittivity detection method.

A light projecting means for irradiating the inspection object of the porous material with the inspection light;
A light receiving means for receiving the scattered light scattered by the inspection object and detecting the scattered light intensity;
Foreign matter detection means for detecting foreign matter on the surface of the inspection object based on the scattered light intensity detected by the light receiving means,
A dielectric constant detecting means for storing a correlation between the relative dielectric constant of the object to be inspected and the scattered light intensity and detecting the relative dielectric constant of the object to be inspected based on the scattered light intensity detected by the light receiving means; Foreign matter inspection apparatus characterized by the above.

The dielectric constant detection means stores the correlation between the relative dielectric constant according to the thickness of the inspection object and the scattered light intensity, inputs the thickness information of the inspection object, and detects the scattering detected by the light receiving means. 4. The foreign matter inspection apparatus according to claim 3, wherein the relative dielectric constant of the object to be inspected is detected based on the light intensity and the inputted thickness information.