JP4039754B2 - Method for measuring contamination amount of semiconductor wafer and method for measuring contamination density - Google Patents

Description

α：相対関係、α_ＩＡＰ：全面試料特性、α_ＤＲＯＰ：局部試料特性
上式を実行して、前記相対関係を算出し、
前記局部試料強度（Ｉ_ＤＲＯＰ）の補正は、
（式２）

Ｉ：補正強度、α：相対関係、Ｉ_ＤＲＯＰ：局部試料強度
上式を実行して行う
ことを特徴とする。
【００１６】
また、請求項４記載の発明は、請求項１記載の発明において、
前記ウェハ汚染量決定工程（Ｓ２４）は、
前記相対関係算出工程（Ｓ２０）が算出した相対関係（α）を用いて、前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）を補正し、
該補正して得られた補正強度（Ｉ）を前記検量線作成工程（Ｓ１２）が作成した検量線に当てはめて、前記ウェハ汚染量（Ａ_{ＷＡＦＥＲ}）を決定する
ことを特徴とする。
【００１７】
また、請求項５記載の発明は、請求項４記載の発明において、
前記相対関係算出工程（Ｓ２０）は、
（式３）

α：相対関係、α_ＤＲＯＰ：局部試料特性、α_ＩＡＰ：全面試料特性
上式を実行して、前記相対関係を算出し、
前記補正強度（Ｉ）は、
（式４）

Ｉ：補正強度、α：相対関係、Ｉ_{ＷＡＦＥＲ}：ウェハ強度
上式を実行して算出する
ことを特徴とする。
【００１８】
また、請求項６記載の発明は、請求項１乃至請求項５のいずれかに記載の発明において、
前記局部汚染試料作製工程（Ｓ１０）は、
前記汚染液滴（１２）を２種類以上調製し、
該調製した各汚染液滴（１２）をそれぞれ異なる位置に滴下する
ことを特徴とする。
【００１９】
また、請求項７記載の発明は、請求項１乃至請求項６のいずれかに記載の発明において、
前記汚染液滴（１２）は、
前記第１の半導体基板（１０）の表面に存在する自然酸化膜を除去して形成された疎水面上に滴下し、
前記汚染痕（１４）は、
前記疎水面上に滴下された汚染液滴（１２）を乾燥させて形成する
ことを特徴とする。
【００２０】
また、請求項８記載の発明は、請求項１乃至請求項７のいずれかに記載の発明において、
前記局部汚染試料作製工程（Ｓ１０）は、
前記汚染物質を１ｐｇ〜１００ｎｇ含む１〜１００μｌの前記汚染液滴（１２）を滴下して、０．１〜１０ｍｍ直径の前記汚染痕（１４）を形成する
ことを特徴とする。
【００２１】
また、請求項９記載の発明は、請求項１乃至請求項８のいずれかに記載の発明において、
前記汚染物質は、
金属であり、
前記汚染液滴（１２）は、
フッ酸、超純水およびフッ酸＋過酸化水素水のグループから選択される
ことを特徴とする。
【００２２】
また、請求項１０記載の発明は、
半導体ウェハ（２６）にＸ線（３２）を照射して得られる蛍光Ｘ線（３０）を半導体検出器（２８）を用いて検出し、該半導体ウェハ（２６）の汚染密度を測定する半導体ウェハの汚染密度測定方法において、
汚染物質を含む汚染液滴（１２）を第１の半導体基板（１０）の表面に滴下して、表面に汚染痕（１４）を有する局部汚染試料（１６）を作製する局部汚染試料作製工程（Ｓ１０）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）にＸ線（３２）を照射して得られる局部試料強度（Ｉ_ＤＲＯＰ）を検出し、該局部試料強度（Ｉ_ＤＲＯＰ）と前記汚染液滴（１２）の汚染量である液滴汚染量（Ａ_ＤＲＯＰ）との対応関係を示す検量線を作成する検量線作成工程（Ｓ１２）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）と前記半導体検出器（２８）とをＸ軸方向に沿って相対的に移動させながら、Ｘ線（３２）を該Ｘ軸と平行に照射して得られるＸ軸強度分布（Ｉ（Ｘ））を測定するＸ軸強度分布測定工程（Ｓ２６）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）と前記半導体検出器（２８）とをＹ軸方向に沿って相対的に移動させながら、Ｘ線（３２）を該Ｘ軸と平行に照射して得られるＹ軸強度分布（Ｉ（Ｙ））を測定するＹ軸強度分布測定工程（Ｓ２８）と、
前記Ｘ軸強度分布測定工程（Ｓ２６）が測定したＸ軸強度分布（Ｉ（Ｘ））と、前記Ｙ軸強度分布測定工程（Ｓ２８）が測定したＹ軸強度分布（Ｉ（Ｙ））とを用いて、前記半導体検出器（２８）の有効開口面積（Ｗ）を算出する有効開口面積算出工程（Ｓ３０）と、
前記半導体ウェハ（２６）にＸ線（３２）を照射して得られるウェハ強度（Ｉ_{ＷＡＦＥＲ}）を検出するウェハ強度検出工程（Ｓ２２）と、
前記検量線作成工程（Ｓ１２）が作成した検量線と、前記有効開口面積算出工程（Ｓ３０）が算出した有効開口面積（Ｗ）と、前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）とを用いて、ウェハ汚染密度（Ｄ_{ＷＡＦＥＲ}）を決定するウェハ汚染密度決定工程（Ｓ３２）と
を具備することを特徴とする。
【００２３】
また、請求項１１記載の発明は、請求項１０記載の発明において、
前記ウェハ汚染密度決定工程（Ｓ３２）は、
前記有効開口面積算出工程（Ｓ３０）が算出した有効開口面積（Ｗ）を用いて、前記検量線作成工程（Ｓ１２）が作成した検量線の液滴汚染量（Ａ_ＤＲＯＰ）を前記汚染液滴（１２）の汚染密度を示す液滴汚染密度（Ｄ_ＤＲＯＰ）に変換し、
前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）を前記変換後の検量線に当てはめて、前記ウェハ汚染密度（Ｄ_{ＷＡＦＥＲ}）を決定する
ことを特徴とする。
【００２４】
また、請求項１２記載の発明は、請求項１１記載の発明において、
前記液滴汚染密度（Ｄ_ＤＲＯＰ）は、
（式５）

Ｄ_ＤＲＯＰ：液滴汚染密度、Ａ_ＤＲＯＰ：液滴汚染量、Ｗ：有効開口面積
上式を実行して算出する
ことを特徴とする。
【００２５】
また、請求項１３記載の発明は、請求項１０記載の発明において、
前記ウェハ汚染密度決定工程（Ｓ３２）は、
前記有効開口面積算出工程（Ｓ３０）が算出した有効開口面積（Ｗ）を用いて、前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）を補正し、
該補正して得られた補正強度（Ｉ）を前記検量線作成工程（Ｓ１２）が作成した検量線に当てはめて、前記ウェハ汚染密度（Ｄ_{ＷＡＦＥＲ}）を決定する
ことを特徴とする。
【００２６】
また、請求項１４記載の発明は、請求項１３記載の発明において、
前記補正強度（Ｉ）は、
（式６）

Ｉ：補正強度、Ｉ_{ＷＡＦＥＲ}：ウェハ強度、Ｗ：有効開口面積
上式を実行して算出する
ことを特徴とする。
【００２７】
また、請求項１５記載の発明は、請求項１０乃至請求項１４のいずれかに記載の発明において、
前記有効開口面積算出工程（Ｓ３０）は、
前記Ｘ軸強度分布測定工程（Ｓ２６）が測定したＸ軸強度分布（Ｉ（Ｘ））または前記Ｙ軸強度分布測定工程（Ｓ２８）が測定したＹ軸強度分布（Ｉ（Ｙ））のピーク値を１として、該Ｘ軸強度分布（Ｉ（Ｘ））および該Ｙ軸強度分布（Ｉ（Ｙ））を規格化し、
該規格化したＸ軸強度分布（Ｉ（Ｘ））およびＹ軸強度分布（Ｉ（Ｙ））の強度方向をＺ軸として３次元プロファイル（３４）を作成し、
該生成した３次元プロファイル（３４）の体積を算出し、
該算出して得られた体積を前記有効開口面積（Ｗ）とする
ことを特徴とする。
【００２８】
また、請求項１６記載の発明は、請求項１５記載の発明において、
前記体積の算出は、
前記３次元プロファイル（３４）の等高線を楕円で近似し、該楕円の面積を前記Ｚ軸方向に積分して行う
ことを特徴とする。
【００２９】
また、請求項１７記載の発明は、請求項１６記載の発明において、
前記体積の算出は、
（式７）

Ｖ：３次元プロファイル（３４）の体積、π：円周率、Ｆ_Ｘ（Ｚ）：等高線の横軸の長さ、Ｆ_Ｙ（Ｚ）：等高線の縦軸の長さ
上式を実行して行う
ことを特徴とする。
【００３０】
また、請求項１８記載の発明は、請求項１０乃至請求項１７のいずれかに記載の発明において、
前記局部汚染試料作製工程（Ｓ１０）は、
前記汚染液滴（１２）を２種類以上調製し、
該調製した各汚染液滴（１２）をそれぞれ異なる位置に滴下する
ことを特徴とする。
【００３１】
また、請求項１９記載の発明は、請求項１０乃至請求項１８のいずれかに記載の発明において、
前記汚染液滴（１２）は、
前記第１の半導体基板（１０）の表面に存在する自然酸化膜を除去して形成された疎水面上に滴下し、
前記汚染痕（１４）は、
前記疎水面上に滴下された汚染液滴（１２）を乾燥させて形成する
ことを特徴とする。
【００３２】
また、請求項２０記載の発明は、請求項１０乃至請求項１９のいずれかに記載の発明において、
前記局部汚染試料作製工程（Ｓ１０）は、
前記汚染物質を１ｐｇ〜１００ｎｇ含む１〜１００μｌの前記汚染液滴（１２）を滴下して、０．１〜１０ｍｍ直径の前記汚染痕（１４）を形成する
ことを特徴とする。
【００３３】
また、請求項２１記載の発明は、請求項１０乃至請求項２０のいずれかに記載の発明において、
前記汚染物質は、
金属であり、
前記汚染液滴（１２）は、
フッ酸、超純水およびフッ酸＋過酸化水素水のグループから選択される
ことを特徴とする。
【００３４】
また、請求項２２記載の発明は、
半導体ウェハ（２６）にＸ線（３２）を照射して得られる蛍光Ｘ線（３０）を半導体検出器（２８）を用いて検出し、該半導体ウェハ（２６）の汚染密度を測定する半導体ウェハの汚染密度測定方法において、
汚染物質を含む汚染液滴（１２）を第１の半導体基板（１０）の表面に滴下して、表面に汚染痕（１４）を有する局部汚染試料（１６）を作製する局部汚染試料作製工程（Ｓ１０）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）にＸ線（３２）を照射して得られる局部試料強度（Ｉ_ＤＲＯＰ）を検出し、該局部試料強度（Ｉ_ＤＲＯＰ）と前記汚染液滴（１２）の汚染量である液滴汚染量（Ａ_ＤＲＯＰ）との対応関係を示す検量線を作成する検量線作成工程（Ｓ１２）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）に、入射角（θ）を変化させながらＸ線（３２）を照射して得られる局部試料強度分布（Ｉ_ＤＲＯＰ（θ））を測定する局部試料強度分布測定工程（Ｓ１４）と、
前記汚染物質を含む汚染溶液（２０）中に第２の半導体基板（１８）を浸漬し、表面に汚染層（２２）を有する全面汚染試料（２４）を作製する全面汚染試料作製工程（Ｓ１６）と、
前記全面汚染試料作製工程（Ｓ１６）が作製した全面汚染試料（２４）に、入射角（θ）を変化させながらＸ線（３２）を照射して得られる全面試料強度分布（Ｉ_ＩＡＰ（θ））を測定する全面試料強度分布測定工程（Ｓ１８）と、
前記局部試料強度分布測定工程（Ｓ１４）が測定した局部試料強度分布（Ｉ_ＤＲＯＰ（θ））と、前記全面試料強度分布測定工程（Ｓ１８）が測定した全面試料強度分布（Ｉ_ＩＡＰ（θ））とを前記入射角（θ）の高角領域（ＲＨ）で一致させて規格化し、局部試料特性（α_ＤＲＯＰ）と全面試料特性（α_ＩＡＰ）とを求める規格化工程（Ｓ１９）と、
前記規格化工程（Ｓ１９）が求めた局部試料特性（α_ＤＲＯＰ）と全面試料特性（α_ＩＡＰ）との相対関係（α）を算出する相対関係算出工程（Ｓ２０）と、
前記半導体ウェハ（２６）にＸ線（３２）を照射して得られるウェハ強度（Ｉ_{ＷＡＦＥＲ}）を検出するウェハ強度検出工程（Ｓ２２）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）と前記半導体検出器（２８）とをＸ軸方向に沿って相対的に移動させながら、Ｘ線（３２）を該Ｘ軸と平行に照射して得られるＸ軸強度分布（Ｉ（Ｘ））を測定するＸ軸強度分布測定工程（Ｓ２６）と、
前記局部汚染試料作製工程（Ｓ１０）が作製した局部汚染試料（１６）と前記半導体検出器（２８）とをＹ軸方向に沿って相対的に移動させながら、Ｘ線（３２）を該Ｘ軸と平行に照射して得られるＹ軸強度分布（Ｉ（Ｙ））を測定するＹ軸強度分布測定工程（Ｓ２８）と、
前記Ｘ軸強度分布測定工程（Ｓ２６）が測定したＸ軸強度分布（Ｉ（Ｘ））と、前記Ｙ軸強度分布測定工程（Ｓ２８）が測定したＹ軸強度分布（Ｉ（Ｙ））とを用いて、前記半導体検出器（２８）の有効開口面積（Ｗ）を算出する有効開口面積算出工程（Ｓ３０）と、
前記検量線作成工程（Ｓ１２）が作成した検量線と、前記相対関係算出工程（Ｓ２０）が算出した相対関係（α）と、前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）と、前記有効開口面積算出工程（Ｓ３０）が算出した有効開口面積（Ｗ）とを用いて、ウェハ汚染密度（Ｄ_{ＷＡＦＥＲ}）を決定するウェハ汚染密度決定工程（Ｓ３２）と
を具備することを特徴とする。
【００３５】
また、請求項２３記載の発明は、請求項２２記載の発明において、
前記ウェハ汚染密度決定工程（Ｓ３２）は、
前記相対関係算出工程（Ｓ２０）が算出した相対関係（α）を用いて、前記検量線作成工程（Ｓ１２）が作成した検量線の局部試料強度（Ｉ_ＤＲＯＰ）を補正するとともに、前記有効開口面積算出工程（Ｓ３０）が算出した有効開口面積（Ｗ）を用いて、前記検量線の液滴汚染量（Ａ_ＤＲＯＰ）を前記汚染液滴（１２）の汚染密度を示す液滴汚染密度（Ｄ_ＤＲＯＰ）に変換し、
前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）を前記変換後の検量線に当てはめて、前記ウェハ汚染密度（Ｄ_{ＷＡＦＥＲ}）を決定する
ことを特徴とする。
【００３６】
また、請求項２４記載の発明は、請求項２３記載の発明において、
前記相対関係算出工程（Ｓ２０）は、
（式１）

α：相対関係、α_ＩＡＰ：全面試料特性、α_ＤＲＯＰ：局部試料特性
上式を実行して、前記相対関係を算出し、
前記局部試料強度（Ｉ_ＤＲＯＰ）の補正は、
（式２）

Ｉ：補正強度、α：相対関係、Ｉ_ＤＲＯＰ：局部試料強度
上式を実行して行い、
前記液滴汚染密度（Ｄ_ＤＲＯＰ）は、
（式５）

Ｄ_ＤＲＯＰ：液滴汚染密度、Ａ_ＤＲＯＰ：液滴汚染量、Ｗ：有効開口面積
上式を実行して算出する
ことを特徴とする。
【００３７】
また、請求項２５記載の発明は、請求項２２記載の発明において、
前記ウェハ汚染密度決定工程（Ｓ３２）は、
前記相対関係算出工程（Ｓ２０）が算出した相対関係（α）と、前記有効開口面積算出工程（Ｓ３０）が算出した有効開口面積（Ｗ）とを用いて、前記ウェハ強度検出工程（Ｓ２２）が検出したウェハ強度（Ｉ_{ＷＡＦＥＲ}）を補正し、
該補正して得られた補正強度（Ｉ）を前記検量線作成工程（Ｓ１２）が作成した検量線に当てはめて、前記ウェハ汚染密度（Ｄ_{ＷＡＦＥＲ}）を決定する
ことを特徴とする。
【００３８】
また、請求項２６記載の発明は、請求項２５記載の発明において、
前記補正強度（Ｉ）は、
（式８）

Ｉ：補正強度、α：相対関係、Ｉ_{ＷＡＦＥＲ}：ウェハ強度、有効開口面積
上式を実行して算出する
ことを特徴とする。
【００３９】
また、請求項２７記載の発明は、請求項２２乃至請求項２６のいずれかに記載の発明において、
前記局部汚染試料作製工程（Ｓ１０）は、
前記汚染液滴（１２）を２種類以上調製し、
該調製した各汚染液滴（１２）をそれぞれ異なる位置に滴下する
ことを特徴とする。
【００４０】
また、請求項２８記載の発明は、請求項２２乃至請求項２７のいずれかに記載の発明において、
前記汚染液滴（１２）は、
前記第１の半導体基板（１０）の表面に存在する自然酸化膜を除去して形成された疎水面上に滴下し、
前記汚染痕（１４）は、
前記疎水面上に滴下された汚染液滴（１２）を乾燥させて形成する
ことを特徴とする。
【００４１】
また、請求項２９記載の発明は、請求項２２乃至請求項２８のいずれかに記載の発明において、
前記局部汚染試料作製工程（Ｓ１０）は、
前記汚染物質を１ｐｇ〜１００ｎｇ含む１〜１００μｌの前記汚染液滴（１２）を滴下して、０．１〜１０ｍｍ直径の前記汚染痕（１４）を形成する
ことを特徴とする。
【００４２】
また、請求項３０記載の発明は、請求項２２乃至請求項２９のいずれかに記載の発明において、
前記汚染物質は、
金属であり、
前記汚染液滴（１２）は、
フッ酸、超純水およびフッ酸＋過酸化水素水のグループから選択される
ことを特徴とする。
【００４７】
【発明の実施の形態】
以下、本発明の実施の形態を添付図面を参照して詳細に説明する。
【００４８】
（発明の概要）
本発明の第１の特徴は、局部汚染試料および全面汚染試料をそれぞれ作製し、当該各試料のＸ線に対する入射角依存性を示す局部試料特性α_ＤＲＯＰと全面試料特性α_ＩＡＰを求め、これらの相対関係αを用いてウェハ汚染量Ａ_{ＷＡＦＥＲ}を決定することにある（図１参照）。
【００４９】
本発明の第２の特徴は、局部汚染試料のＸ線に対するＸ軸強度分布Ｉ（Ｘ）とＹ軸強度分布Ｉ（Ｙ）を測定して、半導体検出器の有効開口面積Ｗを算出し、これを用いてウェハ汚染密度Ｄ_{ＷＡＦＥＲ}を決定することにある。（図４参照）。
【００５０】
上記特徴により、局部汚染試料から作成した検量線が直接使用できるため、全反射蛍光Ｘ線装置の絶対校正が可能となる。
【００５１】
（第１の形態）
本発明の第１の形態は、局部汚染試料と全面汚染試料との相対関係を利用して半導体ウェハの汚染量を測定する発明である。
【００５２】
前述したように、従来は、全反射蛍光Ｘ線分析に適した標準試料が存在しなかったため、全反射蛍光Ｘ線分析の絶対校正を実現するには、まず、適切な標準試料を選定することが必要である。
【００５３】
本発明者らは、全反射蛍光Ｘ線分析の標準試料として、所望の汚染量が容易に得られる局部汚染試料を選定した。この局部汚染試料を使用して作成された検量線は、測定誤差が少なく、作成が容易である。
【００５４】
ここで、半導体ウェハの汚染原因となる汚染物質は、該半導体ウェハの表面に一様に付着しているため、局部汚染試料と汚染状態が異なる。従って、上記検量線を該半導体ウェハの汚染量測定に用いるには、汚染状態に起因する蛍光Ｘ線強度の差を考慮する必要がある。一般に、汚染状態に起因する蛍光Ｘ線強度の差は、Ｘ線の入射角依存性として現れる。
【００５５】
そこで、本発明者らは、局部汚染試料の入射角依存性と全面汚染試料の入射角依存性の相対関係を求め、この相関関係を利用して、上記検量線の適用を図った。
【００５６】
本発明の第１の形態は、上記観点から構成された発明であり、全反射蛍光Ｘ線分析の絶対校正を実現する技術を提供する。
【００５７】
図１は、本発明の第１の形態に係る半導体ウェハの汚染量測定方法の構成を示す工程図である。以下、同図に基づいて、この第１の形態の構成を説明する。
【００５８】
図２は、図１に示す局部汚染試料作製工程Ｓ１０が実行する局部汚染試料１６の作製動作を示す動作説明図である。以下、同図を使用して、図１に示す局部汚染試料作製工程Ｓ１０の構成を説明する。
【００５９】
局部汚染試料作製工程Ｓ１０は、汚染物質を含む汚染液滴１２を第１の半導体基板１０の表面に滴下し（同図（ａ））、該滴下した汚染液滴１２を乾燥させて汚染痕１４を形成し（同図（ｂ））、表面が局部的に汚染された局部汚染試料（以下、必要に応じて「ＤＲＯＰ」と示す）を得る。ここで、ＤＲＯＰは、ドロップレット法の略であり、局部汚染試料１６の作製手段として利用できる。
【００６０】
好ましくは、第１の半導体基板１０の表面に存在する自然酸化膜を除去して、該第１の半導体基板１０に疎水面を形成し、この疎水面上に汚染液滴１２を滴下する。自然酸化膜を除去する手段としては、ＶＰＤ（ｖａｐｏｒ ｐｈａｓｅ ｄｅｃｏｍｐｏｓｉｔｉｏｎ）等のフッ素系化合物を利用した方法が使用できる。このように、汚染液滴１２を疎水面上に滴下すると、汚染液滴１２が疎水面ではじかれるため、粒の細かい汚染痕１４を形成することができる。
【００６１】
また、汚染液滴１２の乾燥は、自然乾燥とすることが好ましく、汚染痕は、半導体検出器の検出範囲（例えば、直径２ｃｍ）に対して十分小さい大きさで形成する。例えば、汚染物質を１ｐｇ〜１００ｎｇ含む１〜１００μｌの前記汚染液滴１２を第１の半導体基板１０表面に滴下し、０．１〜１０ｍｍ直径の汚染痕１４を形成する。
【００６２】
また、好ましくは、汚染物質を金属とし、汚染液滴１２をフッ酸、超純水およびフッ酸＋過酸化水素水のグループから選択する。これらの親水性溶媒で汚染液滴１２を構成すると、該汚染液滴１２が疎水面上ではじかれ易くなり、好適な球形が得られる。
【００６３】
汚染痕１４は、同図に示すように、１つだけ形成してもよいし、異なる汚染量を有する汚染痕１４を複数形成してもよい。この場合には、濃度の異なる２種類以上の汚染液滴１２を調製し、該調製した各汚染液滴１２をそれぞれ第１の半導体基板１０上の異なる位置に滴下する。
【００６４】
このとき、各液滴は、半導体検出器の検出範囲内で重ならない位置に滴下する。好ましくは、各液滴の形状を同一とし、濃度のみが異なるように滴下する。これにより、１つの局部汚染試料から複数の蛍光Ｘ線強度が得られるため、検量線作製が容易に行える。また、この応用例として、異なる物質を含む液滴を複数滴下してもよい。
【００６５】
図３は、図１に示す検量線作成工程Ｓ１２が実行する蛍光Ｘ線強度の検出動作を示す動作説明図である。以下、同図を使用して、図１に示す検量線作成工程Ｓ１２の構成を説明する。
【００６６】
検量線作成工程Ｓ１２は、局部汚染試料１６にＸ線３２を照射して、該局部汚染試料１６から得られた蛍光Ｘ線３０を半導体検出器２８で受光して、該受光した蛍光Ｘ線３０の強度（以下、「局部試料強度Ｉ_ＤＲＯＰ」という）を検出する。この局部試料強度Ｉ_ＤＲＯＰの検出を汚染液滴１２の汚染量（以下、「液滴汚染量Ａ_ＤＲＯＰという」）を変化させながら行って、局部試料強度Ｉ_ＤＲＯＰと汚染液滴１２との対応関係を求める。
【００６７】
図４は、図１に示す検量線作成工程Ｓ１２が作成した検量線の一例を示すグラフである。同図に示すように、検量線作成工程Ｓ１２は、局部試料強度Ｉ_ＤＲＯＰを縦軸、液滴汚染量Ａ_ＤＲＯＰを横軸とする平面上にデータをプロットし、検量線を作成する。ここで、同図に示す検量線では、局部試料強度Ｉ_ＤＲＯＰの単位が＜ｃｏｕｎｔｓ＞であり、液滴汚染量Ａ_ＤＲＯＰの単位が＜ａｔｏｍｓ＞である。
【００６８】
尚、蛍光Ｘ線強度と汚染物質量との関係は、一般に比例関係となるため、該比例関係の比例係数を検量線として使用してもよい。
【００６９】
図５は、図１に示す局部試料強度分布測定工程Ｓ１４が実行する局部試料強度分布Ｉ_ＤＲＯＰ（θ）の測定動作を示す動作説明図である。以下、同図を使用して、図１に示す局部試料強度分布測定工程Ｓ１４の構成を説明する。
【００７０】
局部試料強度分布測定工程Ｓ１４は、局部汚染試料１６の表面に入射角θを変化させながらＸ線３２を照射して、該局部汚染試料１６から得られた蛍光Ｘ線３０の強度分布（以下、「局部試料強度分布Ｉ_ＤＲＯＰ（θ）」）を測定する。Ｘ線の入射角θは、アングルスキャンによって変化させることができる。このとき、入射角θを変化させる範囲には、全反射条件を満たす低角領域ＲＬと全反射条件をはずれた高角領域ＲＨとを含める。
【００７１】
図６は、図１に示す局部試料強度分布測定工程Ｓ１４が測定した局部試料強度分布Ｉ_ＤＲＯＰ（θ）の一例を示すグラフである。同図に示すように、局部試料強度分布測定工程Ｓ１４が測定した局部試料強度分布Ｉ_ＤＲＯＰ（θ）は、低角領域ＲＬにブロードな強度ピークを有し、高角領域ＲＨに入ると強度がなだらかに減少する。
【００７２】
局部試料強度分布Ｉ_ＤＲＯＰ（θ）が同図に示すような分布曲線を有するのは、局部汚染試料１６の汚染痕１４が小山形状であることに起因する。即ち、低角領域ＲＬでは、汚染痕１４が該汚染痕１４に直接入射するＸ線と、一旦、第１の半導体基板１０の表面で反射してから入射するＸ線とを吸収するため、蛍光Ｘ線の量が多くなる。一方、高角領域ＲＨでは、汚染痕１４は、第１の半導体基板１０の表面で反射してから入射するＸ線を吸収しなくなるため、蛍光Ｘ線の量が少なくなる。その結果、局部試料強度分布Ｉ_ＤＲＯＰ（θ）が同図に示すような分布曲線となる。
【００７３】
図７は、図１に示す全面汚染試料作製工程Ｓ１６が実行する全面汚染試料２４の作製動作を示す動作説明図である。以下、同図を使用して、図１に示す全面汚染試料作製工程Ｓ１６の構成を説明する。
【００７４】
全面汚染試料作製工程Ｓ１６は、汚染物質を含む汚染溶液２０中に第２の半導体基板１８を浸漬し（同図（ａ））、表面に汚染層２２を有する全面汚染試料２４（以下、必要に応じて「ＩＡＰ」と示す）を得る（同図（ｂ））。ここで、ＩＡＰ（Ｉｍｍｅｒｓｉｏｎ Ａｌｋａｌｉｎｅ ｈｙｄｒｏｇｅｎ Ｐｅｒｏｘｉｄｅ ｓｏｌｕｔｉｏｎ）は、汚染液浸漬法の略であり、全面汚染試料２４を作製する手段として利用できる。尚、汚染層２２は、同図に示すように、第２の半導体基板１８の表面にのみ形成しても、全面に形成してもよい。
【００７５】
図８は、図１に示す全面試料強度分布測定工程Ｓ１８が実行する全面試料強度分布Ｉ_ＩＡＰ（θ）の測定動作を示す動作説明図である。以下、同図を使用して、図１に示す全面試料強度分布測定工程Ｓ１８の構成を説明する。
【００７６】
全面試料強度分布測定工程Ｓ１８は、全面汚染試料２４の表面に入射角θを変化させながらＸ線３２を照射して、該全面汚染試料２４から得られた蛍光Ｘ線３０の強度分布（以下、「全面試料強度分布Ｉ_ＩＡＰ（θ）」）を測定する。Ｘ線３２の入射角θは、前述した局部試料強度分布測定工程Ｓ１４と同様にして変化させる。
【００７７】
図９は、図１に示す全面試料強度分布測定工程Ｓ１８が測定した全面試料強度分布Ｉ_ＩＡＰ（θ）の一例を示すグラフである。同図に示すように、全面試料強度分布測定工程Ｓ１８が測定した全面試料強度分布Ｉ_ＩＡＰ（θ）は、低角領域ＲＬの後半に比較的急峻な強度ピークを有し、高角領域ＲＨで減少する。
【００７８】
全面試料強度分布Ｉ_ＩＡＰ（θ）が同図に示すような分布曲線を有するのは、全面汚染試料２４の汚染層２２が平坦であることに起因する。即ち、低角領域ＲＬの前半部分では、Ｘ線の反射量が多いため、蛍光Ｘ線の量が少ないが、Ｘ線の入射角θが大きくなるにつれて、Ｘ線の反射量が少なくなり、蛍光Ｘ線の量が多くなる。そして、Ｘ線の入射角θが高角領域ＲＨに入ると、全反射条件をはずれるため、蛍光Ｘ線の量が少なくなる。その結果、局部試料強度分布Ｉ_ＤＲＯＰ（θ）が同図に示すような分布曲線となる。
【００７９】
図１０は、図１に示す規格化工程Ｓ１９が導出した局部試料特性α_ＤＲＯＰおよび全面試料特性α_ＩＡＰと、図１に示す相対関係算出工程Ｓ２０が算出した相対関係αの一例を示すグラフである。以下、同図を使用して、図１に示す規格化工程Ｓ１９と、図１に示す相対関係算出工程Ｓ２０の構成を説明する。
【００８０】
規格化工程Ｓ１９は、局部試料強度分布Ｉ_ＤＲＯＰ（θ）と全面試料強度分布Ｉ_ＩＡＰ（θ）とを高角領域ＲＨで一致させて規格化し、局部試料特性α_ＤＲＯＰと全面試料特性α_ＩＡＰとを求める。ここで、局部試料強度分布Ｉ_ＤＲＯＰ（θ）と全面試料強度分布Ｉ_ＩＡＰ（θ）とを高角領域ＲＨで一致させる理由は、以下の通りである。
【００８１】
即ち、低角領域ＲＬでは、局部汚染試料１６の汚染痕１４が第１の半導体基板１０の表面で反射したＸ線を吸収するのに対し、全面汚染試料２４の汚染層２２は、第２の半導体基板１８の表面で反射したＸ線を吸収しないため、局部試料強度Ｉ_ＤＲＯＰが全面試料強度Ｉ_ＩＡＰよりも大きくなる。
【００８２】
一方、高角領域ＲＨでは、局部汚染試料１６の汚染痕１４および全面汚染試料２４の汚染層２２のいずれも第１の半導体基板１０および第２の半導体基板１８でそれぞれ反射したＸ線を吸収しないため、局部試料強度Ｉ_ＤＲＯＰと全面試料強度Ｉ_ＩＡＰとの比が一定になると考えられる。
【００８３】
局部試料強度Ｉ_ＤＲＯＰと全面試料強度Ｉ_ＩＡＰのと比は、汚染痕１４の汚染密度と汚染層２２の汚染密度の比によって決まるため、汚染痕１４の汚染密度と汚染層２２の汚染密度との比が１になるように、例えば、局部試料強度Ｉ_ＤＲＯＰの値と全面試料強度Ｉ_ＩＡＰの値とが高角領域ＲＨで同一となるように、局部試料強度Ｉ_ＤＲＯＰと全面試料強度Ｉ_ＩＡＰを規格化すれば、局部汚染試料１６と全面汚染試料２４の相対関係を得ることができる。この規格化によって得られた曲線が同図に示す局部試料特性α_ＤＲＯＰと全面試料特性α_ＩＡＰである。
【００８４】
相対関係算出工程Ｓ２０は、同図に示すように、所定の入射角、即ち、検量線作成工程Ｓ１２で局部汚染試料１６に照射したＸ線３２の入射角における局部試料特性α_ＤＲＯＰと全面試料特性α_ＩＡＰとの比率を算出して相対関係αを求める。
【００８５】
図１１は、図１に示すウェハ強度検出工程Ｓ２２が実行するウェハ強度Ｉ_{ＷＡＦＥＲ}の検出動作を示す動作説明図である。以下、同図を使用して、図１に示すウェハ強度検出工程Ｓ２２の構成を説明する。
【００８６】
ウェハ強度検出工程Ｓ２２は、汚染量を測定したい半導体ウェハ２６にＸ線３２を照射して、該半導体ウェハ２６から得られた蛍光Ｘ線３０を半導体検出器２８で受光して、該受光した蛍光Ｘ線３０の強度（以下、「ウェハ強度Ｉ_{ＷＡＦＥＲ}」という）を検出する。ここで、半導体ウェハ２６に照射するＸ線３２の入射角は、相対関係αの算出基準とした入射角と同一とする。従って、検量線作成工程Ｓ１２が照射するＸ線の入射角と、相対関係算出工程Ｓ２０が使用するＸ線の入射角と、ウェハ強度検出工程Ｓ２２が照射するＸ線の入射角とは、同一の角度となる。この角度は、例えば、全反射蛍光Ｘ線分析で一般に用いられる０．０５°とする。
【００８７】
図１に示すウェハ汚染量決定工程Ｓ２４は、上記のようにして得られた検量線と、相対関係αと、ウェハ強度Ｉ_{ＷＡＦＥＲ}を用いて、半導体ウェハ２６の汚染量（以下、「ウェハ汚染量Ａ_{ＷＡＦＥＲ}という」）を決定する。ウェハ汚染量Ａ_{ＷＡＦＥＲ}の決定は、相対関係αを用いて検量線を補正するかまたはウェハ強度Ｉ_{ＷＡＦＥＲ}を補正することにより行う。
【００８８】
相対関係αを用いて検量線を補正する場合には、相対関係算出工程Ｓ２０は、
（式１）

α：相対関係、α_ＩＡＰ：全面試料特性、α_ＤＲＯＰ：局部試料特性
上式を実行して、相対関係αを算出する。
【００８９】
ウェハ汚染量決定工程Ｓ２４は、
（式２）

Ｉ：補正強度、α：相対関係、Ｉ_ＤＲＯＰ：局部試料強度
上式を実行して、図４に示す検量線の縦軸である局部試料強度Ｉ_ＤＲＯＰを補正強度Ｉに変換し、ウェハ強度Ｉ_{ＷＡＦＥＲ}を補正強度Ｉに当てはめて、ウェハ汚染量Ａ_{ＷＡＦＥＲ}を決定する。
【００９０】
相対関係αを用いてウェハ強度Ｉ_{ＷＡＦＥＲ}を補正する場合には、相対関係算出工程Ｓ２０は、
（式３）

α：相対関係、α_ＤＲＯＰ：局部試料特性、α_ＩＡＰ：全面試料特性
上式を実行して、相対関係αを算出する。
【００９１】
ウェハ汚染量決定工程Ｓ２４は、
（式４）

Ｉ：補正強度、α：相対関係、Ｉ_{ＷＡＦＥＲ}：ウェハ強度
上式を実行して、ウェハ強度Ｉ_{ＷＡＦＥＲ}を補正強度Ｉに変換し、該補正強度Ｉを図４に示す検量線の局部試料強度Ｉ_ＤＲＯＰに当てはめて、ウェハ汚染量Ａ_{ＷＡＦＥＲ}を決定する。
【００９２】
以上説明した本発明の第１の形態によれば、全面汚染状態での蛍光Ｘ線強度と局部汚染状態での蛍光Ｘ線強度とが関連づけられるため、局部汚染試料１６で作成した信頼性の高い検量線が使用できる。その結果、全反射蛍光Ｘ線分析の絶対校正が可能となる。
【００９３】
（第２の形態）
本発明の第２の形態は、半導体検出器の感度分布の補正に関する発明である。
【００９４】
汚染密度が同一の局部汚染試料１６と全面汚染試料２４とを全反射蛍光Ｘ線分析にかけると、局部汚染試料１６から得られた局部試料強度Ｉ_ＤＲＯＰと、全面汚染試料２４がら得られた全面試料強度Ｉ_ＩＡＰは、異なる値となる。
【００９５】
これは、全反射蛍光Ｘ線装置の半導体検出器が装置ごとに特有の感度分布を有するからである。即ち、半導体検出器の開口径は、直径約２ｃｍ程度であるが、この直径２ｃｍの開口内で蛍光Ｘ線の検出感度が変化する。例えば、典型的な半導体検出器では、開口中心で最も感度が高く、開口中心から離れるに従って感度が悪くなる。
【００９６】
上記のような感度分布により、半導体検出器の開口中心に位置する汚染痕１４から検出した局部試料強度Ｉ_ＤＲＯＰの方が半導体検出器の開口部に一様に分布する汚染層２２から検出した全面試料強度Ｉ_ＩＡＰよりも大きくなる。
【００９７】
従って、局部汚染試料１６から作成した検量線が正確であっても、半導体検出器の感度ムラが大きければ正確な汚染密度を得ることができなくなる。加えて、前述したように、半導体検出の検出感度は、個々の装置によって異なるため、半導体検出器ごとに測定した汚染密度が相違することも起こり得る。
【００９８】
そこで、本発明の第２の形態では、半導体検出器の感度分布を求めて、正確な汚染密度の測定を図っている。ここで、さらに留意すべき点は、半導体検出器の感度分布がＸ線の照射方向に影響されるという点である。
【００９９】
本発明者らは、半導体検出器の感度分布を求めるための実験を繰り返し、半導体検出器の感度分布が２次元分布を有することを発見した。従って、半導体ウェハの汚染密度を正確に測定するには、半導体検出器の２次元分布に基づく感度校正が必要である。
【０１００】
本発明の第２の形態は、上記観点から構成された発明であり、半導体検出器の感度分布を正確に求めて、全反射蛍光Ｘ線分析の絶対校正を実現する技術を提供する。
【０１０１】
図１２は、本発明の第２の形態に係る半導体ウェハの汚染密度測定方法の構成を示す工程図である。以下、同図に基づいて、本発明の第２の形態の構成を説明する。
【０１０２】
図１３は、図１２に示すＸ軸強度分布測定工程Ｓ２６が実行するＸ軸強度分布Ｉ（Ｘ）の測定動作を示す動作説明図である。以下、同図を使用して、図１２に示すＸ軸強度分布測定工程Ｓ２６の構成を説明する。
【０１０３】
Ｘ軸強度分布測定工程Ｓ２６は、局部汚染試料１６と半導体検出器２８とを同図に示すＸ軸に沿って相対的に移動させながら、Ｘ線３２を該Ｘ軸と平行に照射して、該局部汚染試料１６から得られた蛍光Ｘ線３０を半導体検出器２８で受光し、当該受光した蛍光Ｘ線３０の強度分布（以下、「Ｘ軸強度分布Ｉ（Ｘ）」という）を測定する。
【０１０４】
図１４は、図１２に示すＸ軸強度分布測定工程Ｓ２６が測定したＸ軸強度分布Ｉ（Ｘ）の一例を示すグラフである。同図に示すように、Ｘ軸強度分布Ｉ（Ｘ）は、半導体検出器２８の開口中心付近に強度ピークを有する。
【０１０５】
図１５は、図１２に示すＹ軸強度分布測定工程Ｓ２８が実行するＹ軸強度分布Ｉ（Ｙ）の測定動作を示す動作説明図である。以下、同図を使用して、図１２に示すＹ軸強度分布測定工程Ｓ２８の構成を説明する。
【０１０６】
Ｙ軸強度分布測定工程Ｓ２８は、局部汚染試料１６と半導体検出器２８とを同図に示すＹ軸に沿って相対的に移動させながら、Ｘ線３２を該Ｘ軸と平行に照射して、該局部汚染試料１６から得られた蛍光Ｘ線３０を半導体検出器２８で受光し、当該受光した蛍光Ｘ線３０の強度分布（以下、「Ｙ軸強度分布Ｉ（Ｙ）」という）を測定する。
【０１０７】
図１６は、図１２に示すＹ軸強度分布測定工程Ｓ２８が測定したＹ軸強度分布Ｉ（Ｙ）の一例を示すグラフである。同図に示すように、Ｙ軸強度分布Ｉ（Ｙ）は、Ｘ軸強度分布Ｉ（Ｘ）と同様に、半導体検出器２８の開口中心付近に強度ピークを有するが、Ｘ軸強度分布Ｉ（Ｘ）とは分布曲線の形状が異なる。
【０１０８】
図１７は、図１２に示す有効開口面積算出工程Ｓ３０がＸ軸強度分布Ｉ（Ｘ）とＹ軸強度分布Ｉ（Ｙ）を規格化した状態を示すグラフである。以下、同図を使用して、図１２に示す有効開口面積算出工程Ｓ３０の構成を説明する。
【０１０９】
有効開口面積算出工程Ｓ３０は、最適化により、Ｘ軸強度分布Ｉ（Ｘ）およびＹ軸強度分布Ｉ（Ｙ）のピークをそれぞれ求めた後、当該求めた各ピーク値を１として、Ｘ軸強度分布Ｉ（Ｘ）およびＹ軸強度分布Ｉ（Ｙ）を規格化し、同図に示すような分布曲線を得る。
【０１１０】
図１８は、図１２に示す有効開口面積算出工程Ｓ３０が作成した３次元プロファイル３４の構成を示すグラフである。同図に示すように、有効開口面積算出工程Ｓ３０は、規格化したＸ軸強度分布Ｉ（Ｘ）およびＹ軸強度分布Ｉ（Ｙ）の強度方向をＺ軸として、３次元プロファイル３４を作成する。この３次元プロファイル３４が半導体検出器２８の２次元感度分布を示し、該３次元プロファイル３４の体積が半導体検出器２８の実質的な有効面積（以下、「有効開口面積Ｗという」）となる。
【０１１１】
３次元プロファイルの体積は、一般に、２次元積分によって求めることができるが、２次元積分を行うには、メッシュ状の２次元多点測定が必要であるため、演算時間が膨大となる。
【０１１２】
そこで、３次元プロファイル３４の等高線を楕円で近似し、該楕円の面積をＺ軸方向に積分する楕円近似処理を実行することが好ましい。
【０１１３】
図１９は、図１８に示す３次元プロファイル３４の等高線の構成を示す概念図である。同図に示すように、３次元プロファイル３４の等高線Ｆ（Ｚ）は、長さＦ_Ｘ（Ｚ）の横軸および長さＦ_Ｙ（Ｚ）の縦軸から成る楕円として表すことができる。
【０１１４】
従って、楕円近似による体積の算出は、
（式７）

Ｖ：３次元プロファイル３４の体積、π：円周率、Ｆ_Ｘ（Ｚ）：等高線の横軸の長さ、Ｆ_Ｙ（Ｚ）：等高線の縦軸の長さ
上式を実行して行うことができる。
【０１１５】
有効開口面積算出工程Ｓ３０は、上記のようにして算出した３次元プロファイル３４の体積を半導体検出器２８の有効開口面積Ｗとする。
【０１１６】
図１に示すウェハ汚染密度決定工程Ｓ３２は、検量線作成工程Ｓ１２が作成した検量線と、有効開口面積算出工程Ｓ３０が算出した有効開口面積Ｗと、ウェハ強度検出工程Ｓ２２が検出したウェハ強度Ｉ_{ＷＡＦＥＲ}とを用いて、半導体ウェハ２６の汚染密度（以下、「ウェハ汚染密度Ｄ_{ＷＡＦＥＲ}」という）を決定する。ウェハ汚染密度Ｄ_{ＷＡＦＥＲ}の決定は、有効開口面積Ｗを用いて検量線を補正するかまたはウェハ強度Ｉ_{ＷＡＦＥＲ}を補正することにより行う。
【０１１７】
有効開口面積Ｗを用いて検量線を補正する場合には、ウェハ汚染密度決定工程Ｓ３２は、
（式５）

Ｄ_ＤＲＯＰ：液滴汚染密度、Ａ_ＤＲＯＰ：液滴汚染量、Ｗ：有効開口面積
上式を実行して、検量線の液滴汚染量Ａ_ＤＲＯＰを該汚染液滴１２の汚染密度（以下、「液滴汚染密度Ｄ_ＤＲＯＰ」という）に変換し、ウェハ強度Ｉ_{ＷＡＦＥＲ}を検量線の局部試料強度Ｉ_ＤＲＯＰに当てはめて、該当する液滴汚染密度Ｄ_ＤＲＯＰを取得し、該取得した液滴汚染密度Ｄ_ＤＲＯＰをウェハ汚染密度Ｄ_{ＷＡＦＥＲ}とする。
【０１１８】
有効開口面積Ｗを用いてウェハ強度Ｉ_{ＷＡＦＥＲ}を補正する場合には、ウェハ汚染密度決定工程Ｓ３２は、
（式６）

Ｉ：補正強度、Ｉ_{ＷＡＦＥＲ}：ウェハ強度、Ｗ：有効開口面積
上式を実行して、ウェハ強度Ｉ_{ＷＡＦＥＲ}を補正強度Ｉに変換し、該補正強度Ｉを図４に示す検量線の局部試料強度Ｉ_ＤＲＯＰに当てはめて、該当する液滴汚染量Ａ_ＤＲＯＰを取得し、当該取得した液滴汚染量Ａ_ＤＲＯＰをウェハ汚染密度Ｄ_{ＷＡＦＥＲ}とする。
【０１１９】
その他の構成は、前述した第１の形態と同じである。
【０１２０】
以上説明した本発明の第２の形態によれば、半導体検出器２８の２次元感度分布に基づいて、検量線またはウェハ強度Ｉ_{ＷＡＦＥＲ}が補正されるため、正確なウェハ汚染密度Ｄ_{ＷＡＦＥＲ}を得ることができる。その結果、全反射蛍光Ｘ線分析の絶対校正が可能となる。
【０１２１】
（第３の形態）
本発明の第３の形態は、Ｘ線の入射角依存性と半導体検出器の感度分布との双方を考慮して、半導体ウェハの汚染密度を測定する発明である。
【０１２２】
前述したように、局部汚染試料と全面汚染試料とでは、Ｘ線の入射角依存性および半導体検出器の感度分布が異なる。
【０１２３】
従って、真に正確な汚染密度を求めるには、Ｘ線の入射角依存性の差と半導体検出器の感度分布の差の両方を考慮して、検量線を適用することが望ましい。
【０１２４】
本発明の第３の形態は、上記観点から構成された発明であり、全反射蛍光Ｘ線分析の絶対校正を好適に実現する技術を提供する。
【０１２５】
図２０は、本発明の第３の形態に係る汚染濃度測定方法の第１の工程を示す工程図である。同図に示すように、本発明の第３の形態では、第１の形態の構成を利用して、相対関係αを算出する。
【０１２６】
図２１は、本発明の第３の形態に係る汚染濃度測定方法の第２の工程を示す工程図である。同図に示すように、本発明の第３の形態では、第２の形態の構成を利用して、有効開口面積Ｗを算出する。
【０１２７】
以下、図２０に基づいて、本発明の第３の形態の構成を説明する。
【０１２８】
ウェハ汚染密度決定工程Ｓ３２は、検量線作成工程Ｓ１２が作成した検量線と、相対関係算出工程Ｓ２０が算出した相対関係αと、ウェハ強度検出工程Ｓ２２が検出したウェハ強度Ｉ_{ＷＡＦＥＲ}と、有効開口面積算出工程Ｓ３０が算出した有効開口面積Ｗとを用いて、ウェハ汚染密度Ｄ_{ＷＡＦＥＲ}を決定する。ウェハ汚染密度Ｄ_{ＷＡＦＥＲ}の決定は、相対関係αと有効開口面積Ｗとを用いて検量線を補正するかまたはウェハ強度Ｉ_{ＷＡＦＥＲ}を補正することにより行う。
【０１２９】
相対関係α有効開口面積Ｗとを用いて検量線を補正する場合には、相対関係算出工程Ｓ２０は、
（式１）

α：相対関係、α_ＩＡＰ：全面試料特性、α_ＤＲＯＰ：局部試料特性
上式を実行して、相対関係αを算出する。
【０１３０】
ウェハ汚染密度決定工程Ｓ３２は、
（式２）

Ｉ：補正強度、α：相対関係、Ｉ_ＤＲＯＰ：局部試料強度
上式を実行して、図４に示す検量線の縦軸である局部試料強度Ｉ_ＤＲＯＰを補正強度Ｉに変換するとともに、
（式５）

Ｄ_ＤＲＯＰ：液滴汚染密度、Ａ_ＤＲＯＰ：液滴汚染量、Ｗ：有効開口面積
上式を実行して、検量線の液滴汚染量Ａ_ＤＲＯＰを液滴汚染密度Ｄ_ＤＲＯＰに変換し、ウェハ強度Ｉ_{ＷＡＦＥＲ}を検量線の局部試料強度Ｉ_ＤＲＯＰに当てはめて、該当する液滴汚染密度Ｄ_ＤＲＯＰを取得し、該取得した液滴汚染密度Ｄ_ＤＲＯＰをウェハ汚染密度Ｄ_{ＷＡＦＥＲ}とする。
【０１３１】
相対関係αおよび有効開口面積Ｗを用いてウェハ強度Ｉ_{ＷＡＦＥＲ}を補正する場合には、相対関係算出工程Ｓ２０は、
（式３）

α：相対関係、α_ＤＲＯＰ：局部試料特性、α_ＩＡＰ：全面試料特性
上式を実行して、相対関係αを算出する。
【０１３２】
ウェハ汚染密度決定工程Ｓ３２は、
（式８）

Ｉ：補正強度、α：相対関係、Ｉ_{ＷＡＦＥＲ}：ウェハ強度、有効開口面積
上式を実行して、ウェハ強度Ｉ_{ＷＡＦＥＲ}を補正強度Ｉに変換し、該補正強度Ｉを図４に示す検量線の局部試料強度Ｉ_ＤＲＯＰに当てはめて、該当する液滴汚染量Ａ_ＤＲＯＰを取得し、当該取得した液滴汚染量Ａ_ＤＲＯＰをウェハ汚染密度Ｄ_{ＷＡＦＥＲ}とする。
【０１３３】
以上説明した本発明の第３の形態によれば、局部汚染試料１６と全面汚染試料２４のＸ線入射角依存性の差と、半導体検出器２８の感度分布の差とが両方考慮されるため、ウェハ汚染密度Ｄ_{ＷＡＦＥＲ}をより正確に求めることができる。
【実施例】
以下、本発明の一実施例を添付図面を参照して詳細に説明する。
【０１３４】
（実施例の要約）
全面汚染試料と局部汚染試料の高角における蛍光Ｘ線強度を規格化して相対関係αを求めるとともに（図１０参照）、半導体検出器のＸ軸分布とＹ軸分布を測定して該半導体検出器の有効開口面積Ｗを求め（図１７参照）、これらの値を使用して検量線または半導体検出器のカウントを適切に補正する。
【０１３５】
（好適な実施例）
まず、図２に示すような局部汚染試料を以下の手順で作製する。
【０１３６】
（１）局部汚染試料の基体となる半導体ウェハをキャリアに装填する。
【０１３７】
（２）前記キャリアをフッ化水素酸を入れたビーカーとともに密閉容器に収容し、１〜３時間程度放置する。これによって、半導体ウェハの表面に存在する自然酸化膜が分解し、該半導体ウェハに疎水面が形成される。
【０１３８】
（３）原子吸光用の標準液を希釈して１００（１〜１０００ＰＰｂ）程度の汚染液を調製し、マイクロピペットを使用して、前記疎水面に１０（１〜１００）マイクロリットル程度滴下する。
【０１３９】
（４）汚染液の濃度を変化させて、上記ステップ３を繰り返し、半導体ウェハの疎水面上に複数の汚染液を滴下する。
【０１４０】
（５）複数の汚染液が滴下された半導体ウェハをクリーンドラフト（クリーンブース）に収容し、自然乾燥させる。これにより、汚染液が乾燥して０．１〜１０ｍｍ直径の汚染痕が半導体ウェハの表面上に形成される。
【０１４１】
次に、上記手順で作製した局部汚染試料を用いて、検量線を作成する。検量線の作成は以下の手順で行う。
【０１４２】
（１）局部汚染試料の表面に形成した各汚染痕に対し、０．０５°の入射角でＸ線を照射して、該各汚染痕から得られた蛍光Ｘ線強度を検出する。
【０１４３】
（２）上記ステップで検出した蛍光Ｘ線強度を縦軸に、各汚染痕の汚染量を横軸にプロットし、図４に示すような検量線を作成する。
【０１４４】
次に、局部汚染試料のＸ線入射角依存性を測定する。局部汚染試料の入射角依存性の測定は、以下のステップで行う。
【０１４５】
（１）局部汚染試料に形成された汚染痕の直上に半導体検出器を配置し、アングルスキャンによって、０°〜０．３°の範囲でＸ線を照射しながら、発生した蛍光Ｘ線の強度を検出する。
【０１４６】
（２）上記ステップで検出した値を用いて、図６に示すようなグラフを作成し、局部試料特性α_ＤＲＯＰを求める。
【０１４７】
次に、図７に示すような全面汚染試料を以下の手順で作製する。
【０１４８】
（１）Ｘ線入射角依存性を測定した局部汚染試料の汚染痕と同一濃度の汚染溶液を調製する。
【０１４９】
（２）上記ステップで調製した汚染溶液に、全面汚染試料の基体となる半導体ウェハを浸漬する。
【０１５０】
次に、上記のようにして作製した全面汚染試料のＸ線入射角依存性を測定する。全面汚染試料の入射角依存性の測定は、以下のステップで行う。
【０１５１】
（１）全面汚染試料の直上に半導体検出器を配置し、アングルスキャンによって、０°〜０．３°の範囲でＸ線を照射しながら、発生した蛍光Ｘ線の強度を検出する。
【０１５２】
（２）上記ステップで検出した値を用いて、図９に示すようなグラフを作成し、全面試料特性α_ＩＡＰを求める。
【０１５３】
次に、局部汚染試料と全面汚染試料の相対関係αを導出する。相対関係αの導出は、以下の手順で実行する。
【０１５４】
（１）局部試料特性α_ＤＲＯＰと全面試料特性α_ＩＡＰを任意の比率で規格化し、高角領域で一致させて、図１０に示すようなグラフを作成する。
【０１５５】
（２）上記ステップで作成したグラフの入射角が０．０５°における局部試料特性α_ＤＲＯＰと全面試料特性α_ＩＡＰの比率を求めて、これを相対関係αとする。
【０１５６】
次に、半導体検出器の有効開口面積Ｗを以下の手順で求める。
【０１５７】
（１）局部汚染試料に形成された汚染痕の直上に半導体検出器を配置し、該汚染痕に０．０５°の入射角でＸ線を照射して、該各汚染痕から得られた蛍光Ｘ線強度を検出する。
【０１５８】
（２）半導体検出器または局部汚染試料をＸの照射方向と平行方向（Ｘ軸方向）に移動させながら、上記ステップを繰り返して、図１４に示すようなグラフを作成する。このときの移動範囲は、半導体検出器の開口径（例えば、２ｃｍ）を含む範囲とする。
【０１５９】
（３）半導体検出器または局部汚染試料をＸの照射方向と直行方向（Ｙ軸方向）に移動させながら、上記ステップ１を繰り返して、図１６に示すようなグラフを作成する。このときの移動範囲も、半導体検出器の開口径（例えば、２ｃｍ）を含む範囲とする。
【０１６０】
（４）ステップ２で作成したグラフと、ステップ３で作成したグラフのピークを１として規格化し、図１７に示すようなグラフを作成する。
【０１６１】
（５）上記ステップ４で作成した規格化後のグラフを３次元に展開し、図１８に示すような３次元プロファイルを作成する。
【０１６２】
（６）上記ステップ１で作成した３次元プロファイルの体積を楕円近似（式７）で算出し、その結果を半導体検出器の有効開口面積Ｗとする。
【０１６３】
次に、被検査対象となる半導体ウェハの汚染密度を以下の手順で決定する。
【０１６４】
（１）上述した手順を実行することによって得られた相対関係αを用いて、検量線の縦軸を補正する。
【０１６５】
（２）上述した手順を実行することによって得られた有効開口面積Ｗを用いて、検量線の横軸を補正する。
【０１６６】
（３）被検査対象となる半導体ウェハに０．０５°の入射角でＸ線を照射して、該半導体ウェハから得られた蛍光Ｘ線強度を検出する。
【０１６７】
（４）上記ステップ３で検出した蛍光Ｘ線強度を上記ステップ２およびステップ３で補正した検量線に当てはめて、該半導体ウェハの汚染密度を決定する。
【０１６８】
【発明の効果】
以上説明したように、本発明によれば、ウェハ汚染量の簡易かつ正確な測定に有効な半導体ウェハの汚染量測定方法および汚染密度測定方法並びに局部汚染試料の作製方法を提供することができる。
【０１６９】
また、本発明の第１の形態によれば、全面汚染状態での蛍光Ｘ線強度と局部汚染状態での蛍光Ｘ線強度とが関連づけられるため、局部汚染試料１６で作成した信頼性の高い検量線が使用できる。その結果、全反射蛍光Ｘ線分析の絶対校正が可能となる。
【０１７０】
また、本発明の第２の形態によれば、半導体検出器２８の２次元感度分布に基づいて、検量線またはウェハ強度Ｉ_{ＷＡＦＥＲ}が補正されるため、正確なウェハ汚染密度Ｄ_{ＷＡＦＥＲ}を得ることができる。その結果、全反射蛍光Ｘ線分析の絶対校正が可能となる。
【０１７１】
また、本発明の第３の形態によれば、局部汚染試料１６と全面汚染試料２４のＸ線入射角依存性の差と、半導体検出器２８の感度分布の差とが両方考慮されるため、ウェハ汚染密度Ｄ_{ＷＡＦＥＲ}をより正確に求めることができる。
【図面の簡単な説明】
【図１】本発明の第１の形態に係る半導体ウェハの汚染量測定方法の構成を示す工程図である。
【図２】図１に示す局部汚染試料作製工程Ｓ１０が実行する局部汚染試料１６の作製動作を示す動作説明図である。
【図３】図１に示す検量線作成工程Ｓ１２が実行する蛍光Ｘ線強度の検出動作を示す動作説明図である。
【図４】図１に示す検量線作成工程Ｓ１２が作成した検量線の一例を示すグラフである。
【図５】図１に示す局部試料強度分布測定工程Ｓ１４が実行する局部試料強度分布Ｉ_ＤＲＯＰ（θ）の測定動作を示す動作説明図である。
【図６】図１に示す局部試料強度分布測定工程Ｓ１４が測定した局部試料強度分布Ｉ_ＤＲＯＰ（θ）の一例を示すグラフである。
【図７】図１に示す全面汚染試料作製工程Ｓ１６が実行する全面汚染試料２４の作製動作を示す動作説明図である。
【図８】図１に示す全面試料強度分布測定工程Ｓ１８が実行する全面試料強度分布Ｉ_ＩＡＰ（θ）の測定動作を示す動作説明図である。
【図９】図１に示す全面試料強度分布測定工程Ｓ１８が測定した全面試料強度分布Ｉ_ＩＡＰ（θ）の一例を示すグラフである。
【図１０】図１に示す規格化工程Ｓ１９が導出した局部試料特性α_ＤＲＯＰおよび全面試料特性α_ＩＡＰと、図１に示す相対関係算出工程Ｓ２０が算出した相対関係αの一例を示すグラフである。
【図１１】図１に示すウェハ強度検出工程Ｓ２２が実行するウェハ強度Ｉ_{ＷＡＦＥＲ}の検出動作を示す動作説明図である。
【図１２】本発明の第２の形態に係る半導体ウェハの汚染密度測定方法の構成を示す工程図である。
【図１３】図１２に示すＸ軸強度分布測定工程Ｓ２６が実行するＸ軸強度分布Ｉ（Ｘ）の測定動作を示す動作説明図である。
【図１４】図１２に示すＸ軸強度分布測定工程Ｓ２６が測定したＸ軸強度分布Ｉ（Ｘ）の一例を示すグラフである。
【図１５】図１２に示すＹ軸強度分布測定工程Ｓ２８が実行するＹ軸強度分布Ｉ（Ｙ）の測定動作を示す動作説明図である。
【図１６】図１２に示すＹ軸強度分布測定工程Ｓ２８が測定したＹ軸強度分布Ｉ（Ｙ）の一例を示すグラフである。
【図１７】図１２に示す有効開口面積算出工程Ｓ３０がＸ軸強度分布Ｉ（Ｘ）とＹ軸強度分布Ｉ（Ｙ）を規格化した状態を示すグラフである。
【図１８】図１２に示す有効開口面積算出工程Ｓ３０が作成した３次元プロファイル３４の構成を示すグラフである。
【図１９】図１８に示す３次元プロファイル３４の等高線の構成を示す概念図である。
【図２０】本発明の第３の形態に係る汚染濃度測定方法の第１の工程を示す工程図である。
【図２１】本発明の第３の形態に係る汚染濃度測定方法の第２の工程を示す工程図である。
【符号の説明】
１０…第１の半導体基板、１２…汚染液滴、１４…汚染痕、１６…局部汚染試料、１８…第２の半導体基板、２０…汚染溶液、２２…汚染層、２４…全面汚染試料、２６…半導体ウェハ、２８…半導体検出器、３０…蛍光Ｘ線、３２…Ｘ線、３４…３次元プロファイル、Ｓ１０…局部汚染試料作製工程、Ｓ１２…検量線作成工程、Ｓ１４…局部試料強度分布測定工程、Ｓ１６…全面汚染試料作製工程、Ｓ１８…全面試料強度分布測定工程、Ｓ１９…規格化工程、Ｓ２０…相対関係算出工程、Ｓ２２…ウェハ強度検出工程、Ｓ２４…ウェハ汚染量決定工程、Ｓ２６…Ｘ軸強度分布測定工程、Ｓ２８…Ｙ軸強度分布測定工程、Ｓ３０…有効開口面積算出工程、Ｓ３２…ウェハ汚染密度決定工程、Ａ_ＤＲＯＰ…液滴汚染量、Ａ_{ＷＡＦＥＲ}…ウェハ汚染量、Ｄ_ＤＲＯＰ…液滴汚染密度、Ｄ_{ＷＡＦＥＲ}…ウェハ汚染密度、Ｉ…補正強度、Ｉ_ＤＲＯＰ…局部試料強度、Ｉ_ＤＲＯＰ（θ）…局部試料強度分布、Ｉ_ＩＡＰ…全面試料強度、Ｉ_ＩＡＰ（θ）…全面試料強度分布、Ｉ_{ＷＡＦＥＲ}…ウェハ強度、Ｉ（Ｘ）…Ｘ軸強度分布、Ｉ（Ｙ）…Ｙ軸強度分布、ＲＨ…高角領域、ＲＬ…低角領域、Ｗ…有効開口面積、α…相対関係、α_ＤＲＯＰ…局部試料特性、α_ＩＡＰ…全面試料特性、θ…入射角[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer contamination amount measuring method, a contamination density measuring method, and a locally contaminated sample preparation method, and more particularly to a semiconductor wafer contamination amount measuring method and contamination density measurement effective for simple and accurate measurement of wafer contamination amount. The present invention relates to a method and a method for producing a locally contaminated sample.
[0002]
[Prior art]
As the degree of integration of semiconductor devices increases, it is required to increase the cleaning degree of silicon wafers. As a method for inspecting the cleaning degree of a silicon wafer, a contamination amount measuring method called a VPD method (Vapor Phase Decomposition) has been conventionally performed. In this VPD method, the contamination amount of a silicon wafer is measured according to a series of procedures shown below.
[0003]
(1) A silicon wafer is housed in a sealed container and exposed to a hydrofluoric acid vapor atmosphere for a certain period of time. By this treatment, the natural oxide film formed on the surface of the silicon wafer is decomposed to form a hydrophobic surface.
[0004]
(2) An acidic droplet is dropped on the hydrophobic surface, and the dropped droplet is scanned on the surface of the silicon wafer. By this treatment, contaminants adhering to the silicon wafer are absorbed by the droplets.
[0005]
(3) The droplets after the scanning are collected, and the collected ion count is detected by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). In the case of the AAS method, the absorbance is detected instead of the ion count.
[0006]
(4) Create a calibration curve using droplets with known contaminant concentrations.
[0007]
(5) Using the calibration curve, the amount of contaminants in the droplet collected in step 4 is obtained from the detected ion count, and the contamination amount of the silicon wafer is specified based on the amount of contaminants.
[0008]
[Problems to be solved by the invention]
However, in the VPD method, since the operation is complicated, it is difficult to completely recover the contaminant from the surface of the wafer, and there is a problem that an error occurs in the measured value.
[0009]
Total reflection X-ray Fluorescence (TXRF) established to solve the above problem is a simple measurement method, but since there is no standard sample, only total reflection X-ray fluorescence analysis There was a problem that absolute calibration could not be performed. That is, when measuring the amount of contamination of a wafer by total reflection fluorescent X-ray analysis, correlation with the VPD method is necessary in the end, and the problem that an error occurs in a measured value has not been completely solved.
[0010]
On the other hand, in Japanese Patent Laid-Open No. 4-144151, the difference between local contamination due to droplets and overall contamination due to immersion is regarded as a sensitivity distribution of a semiconductor detector that is a component of a total reflection X-ray analyzer, and the sensitivity distribution is A technique for correcting a detection result by a total reflection X-ray analyzer by using it is disclosed. The technique disclosed in Japanese Patent Laid-Open No. Hei 4-144151 is considered to be very useful as a means for solving the above problems.
[0011]
However, the sensitivity distribution of the semiconductor detector varies depending on measurement conditions such as the shape of the droplet and the incident direction of X-rays. Therefore, in order to effectively implement the technique, it has been desired to develop the technique in consideration of various measurement conditions.
[0012]
Therefore, an object of the present invention is to provide a method for measuring the amount of contamination of a semiconductor wafer, a method for measuring the contamination density, and a method for preparing a local contamination sample, which are effective for simple and accurate measurement of the amount of wafer contamination.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1
A semiconductor wafer which detects fluorescent X-rays (30) obtained by irradiating a semiconductor wafer (26) with X-rays (32) using a semiconductor detector (28) and measures the amount of contamination of the semiconductor wafer (26). In the method for measuring the amount of contamination of
A locally contaminated sample preparation step (in which a contaminated droplet (12) containing a contaminant is dropped on the surface of the first semiconductor substrate (10) to produce a locally contaminated sample (16) having a contamination mark (14) on the surface ( S10)
Local sample strength (I) obtained by irradiating the locally contaminated sample (16) prepared in the locally contaminated sample preparing step (S10) with X-rays (32). _DROP ) And the local sample strength (I _DROP ) And the droplet contamination amount (A) which is the contamination amount of the contaminated droplet (12). _DROP A calibration curve creating step (S12) for creating a calibration curve showing a correspondence relationship with
Local sample intensity distribution (I) obtained by irradiating the locally contaminated sample (16) produced in the locally contaminated sample producing step (S10) with X-rays (32) while changing the incident angle (θ). _DROP (Θ)) local sample intensity distribution measuring step (S14);
Fully contaminated sample preparation step (S16) of immersing the second semiconductor substrate (18) in the contaminated solution (20) containing the contaminant to prepare a fully contaminated sample (24) having a contaminated layer (22) on the surface. When,
Whole surface sample intensity distribution (I) obtained by irradiating the whole surface contaminated sample (24) prepared in the whole surface contaminated sample preparation step (S16) with X-rays (32) while changing the incident angle (θ). _IAP (Θ)) is a whole surface sample strength distribution measuring step (S18),
The local sample strength distribution (I) measured in the local sample strength distribution measuring step (S14). _DROP (Θ)) and the whole surface sample strength distribution (I) measured in the whole surface sample strength distribution measuring step (S18). _IAP (Θ)) in the high angle region (RH) of the incident angle (θ) and normalization, and local sample characteristics (α _DROP ) And overall sample characteristics (α _IAP ) And a standardization step (S19) for obtaining
Local sample characteristics (α) obtained in the normalization step (S19) _DROP ) And overall sample characteristics (α _IAP A relative relationship calculating step (S20) for calculating a relative relationship (α) with
Wafer strength (I) obtained by irradiating the semiconductor wafer (26) with X-rays (32) _WAFER ) To detect the wafer strength (S22),
The calibration curve created by the calibration curve creation step (S12), the relative relationship (α) calculated by the relative relationship calculation step (S20), and the wafer strength (I) detected by the wafer strength detection step (S22). _WAFER ) And the amount of wafer contamination (A _WAFER Wafer contamination amount determination step (S24) for determining
It is characterized by comprising.
[0014]
The invention according to claim 2 is the invention according to claim 1,
The wafer contamination amount determination step (S24)
Using the relative relationship (α) calculated in the relative relationship calculation step (S20), the local sample strength (I of the calibration curve created in the calibration curve creation step (S12)) _DROP )
Wafer strength (I) detected by the wafer strength detection step (S22) _WAFER ) Is applied to the corrected calibration curve, and the wafer contamination amount (A _WAFER )
It is characterized by that.
[0015]
The invention according to claim 3 is the invention according to claim 2,
The relative relationship calculating step (S20)
(Formula 1)

α: Relative relationship, α _IAP : Whole surface sample characteristics, α _DROP : Local sample characteristics
Execute the above formula to calculate the relative relationship,
The local sample strength (I _DROP )
(Formula 2)

I: correction intensity, α: relative relationship, I _DROP : Local sample strength
Execute the above formula
It is characterized by that.
[0016]
The invention according to claim 4 is the invention according to claim 1,
The wafer contamination amount determination step (S24)
The wafer strength (I) detected by the wafer strength detection step (S22) using the relative relationship (α) calculated by the relative relationship calculation step (S20). _WAFER )
The corrected intensity (I) obtained by the correction is applied to the calibration curve created in the calibration curve creating step (S12), and the wafer contamination amount (A _WAFER )
It is characterized by that.
[0017]
The invention according to claim 5 is the invention according to claim 4,
The relative relationship calculating step (S20)
(Formula 3)

α: Relative relationship, α _DROP : Local sample characteristics, α _IAP : Whole surface sample characteristics
Execute the above formula to calculate the relative relationship,
The corrected intensity (I) is
(Formula 4)

I: correction intensity, α: relative relationship, I _WAFER : Wafer strength
Calculate by executing the above formula
It is characterized by that.
[0018]
The invention according to claim 6 is the invention according to any one of claims 1 to 5,
The locally contaminated sample preparation step (S10)
Preparing two or more of the contaminated droplets (12),
The prepared contaminated droplets (12) are dropped at different positions.
It is characterized by that.
[0019]
The invention according to claim 7 is the invention according to any one of claims 1 to 6,
The contaminated droplet (12)
Dropping on the hydrophobic surface formed by removing the natural oxide film present on the surface of the first semiconductor substrate (10),
The contamination mark (14)
Contaminated droplets (12) dropped on the hydrophobic surface are formed by drying.
It is characterized by that.
[0020]
The invention according to claim 8 is the invention according to any one of claims 1 to 7,
The locally contaminated sample preparation step (S10)
1 to 100 μl of the contamination droplet (12) containing 1 pg to 100 ng of the contaminant is dropped to form the contamination mark (14) having a diameter of 0.1 to 10 mm.
It is characterized by that.
[0021]
The invention according to claim 9 is the invention according to any one of claims 1 to 8,
The contaminant is
Metal,
The contaminated droplet (12)
Selected from the group of hydrofluoric acid, ultrapure water and hydrofluoric acid + hydrogen peroxide water
It is characterized by that.
[0022]
The invention according to claim 10
A semiconductor wafer that detects fluorescent X-rays (30) obtained by irradiating the semiconductor wafer (26) with X-rays (32) using a semiconductor detector (28) and measures the contamination density of the semiconductor wafer (26). In the contamination density measurement method of
A locally contaminated sample preparation step (in which a contaminated droplet (12) containing a contaminant is dropped on the surface of the first semiconductor substrate (10) to produce a locally contaminated sample (16) having a contamination mark (14) on the surface ( S10)
Local sample strength (I) obtained by irradiating the locally contaminated sample (16) prepared in the locally contaminated sample preparing step (S10) with X-rays (32). _DROP ) And the local sample strength (I _DROP ) And the droplet contamination amount (A) which is the contamination amount of the contaminated droplet (12). _DROP A calibration curve creating step (S12) for creating a calibration curve showing a correspondence relationship with
While relatively moving the locally contaminated sample (16) and the semiconductor detector (28) prepared in the locally contaminated sample preparing step (S10) along the X-axis direction, the X-ray (32) is moved to the X-axis. An X-axis intensity distribution measuring step (S26) for measuring an X-axis intensity distribution (I (X)) obtained by irradiation in parallel with
While relatively moving the locally contaminated sample (16) and the semiconductor detector (28) prepared in the locally contaminated sample preparing step (S10) along the Y-axis direction, the X-ray (32) is moved to the X-axis. Y-axis intensity distribution measuring step (S28) for measuring the Y-axis intensity distribution (I (Y)) obtained by irradiation in parallel with
The X-axis intensity distribution (I (X)) measured by the X-axis intensity distribution measuring step (S26) and the Y-axis intensity distribution (I (Y)) measured by the Y-axis intensity distribution measuring step (S28). Using an effective opening area calculating step (S30) for calculating an effective opening area (W) of the semiconductor detector (28);
Wafer strength (I) obtained by irradiating the semiconductor wafer (26) with X-rays (32) _WAFER ) To detect the wafer strength (S22),
The calibration curve created in the calibration curve creation step (S12), the effective aperture area (W) calculated in the effective aperture area calculation step (S30), and the wafer strength (I) detected in the wafer strength detection step (S22) _WAFER ) And wafer contamination density (D _WAFER Wafer contamination density determination step (S32) for determining
It is characterized by comprising.
[0023]
The invention according to claim 11 is the invention according to claim 10,
The wafer contamination density determination step (S32)
Using the effective opening area (W) calculated by the effective opening area calculating step (S30), the droplet contamination amount (A of the calibration curve created by the calibration curve creating step (S12)) _DROP ) Is a droplet contamination density (D) indicating the contamination density of the contamination droplet (12). _DROP ),
Wafer strength (I) detected by the wafer strength detection step (S22) _WAFER ) Is applied to the converted calibration curve, and the wafer contamination density (D _WAFER )
It is characterized by that.
[0024]
The invention according to claim 12 is the invention according to claim 11,
The droplet contamination density (D _DROP )
(Formula 5)

D _DROP : Droplet contamination density, A _DROP : Amount of droplet contamination, W: Effective opening area
Calculate by executing the above formula
It is characterized by that.
[0025]
Further, the invention of claim 13 is the invention of claim 10,
The wafer contamination density determination step (S32)
Using the effective opening area (W) calculated in the effective opening area calculating step (S30), the wafer intensity (I) detected in the wafer intensity detecting step (S22). _WAFER )
The correction intensity (I) obtained by the correction is applied to the calibration curve created in the calibration curve creation step (S12), and the wafer contamination density (D _WAFER )
It is characterized by that.
[0026]
The invention according to claim 14 is the invention according to claim 13,
The corrected intensity (I) is
(Formula 6)

I: correction intensity, I _WAFER : Wafer strength, W: Effective opening area
Calculate by executing the above formula
It is characterized by that.
[0027]
The invention according to claim 15 is the invention according to any one of claims 10 to 14,
The effective opening area calculating step (S30)
The peak value of the X-axis intensity distribution (I (X)) measured by the X-axis intensity distribution measuring step (S26) or the Y-axis intensity distribution (I (Y)) measured by the Y-axis intensity distribution measuring step (S28). , The X-axis intensity distribution (I (X)) and the Y-axis intensity distribution (I (Y)) are normalized,
Creating a three-dimensional profile (34) with the intensity directions of the normalized X-axis intensity distribution (I (X)) and Y-axis intensity distribution (I (Y)) as the Z-axis,
Calculating the volume of the generated three-dimensional profile (34);
The calculated volume is defined as the effective opening area (W).
It is characterized by that.
[0028]
The invention described in claim 16 is the invention described in claim 15,
The calculation of the volume is
The contour line of the three-dimensional profile (34) is approximated by an ellipse, and the area of the ellipse is integrated in the Z-axis direction.
It is characterized by that.
[0029]
The invention described in claim 17 is the invention described in claim 16,
The calculation of the volume is
(Formula 7)

V: Volume of the three-dimensional profile (34), π: Circumference ratio, F _X (Z): Length of horizontal axis of contour line, F _Y (Z): Length of contour line vertical axis
Execute the above formula
It is characterized by that.
[0030]
The invention according to claim 18 is the invention according to any one of claims 10 to 17,
The locally contaminated sample preparation step (S10)
Preparing two or more of the contaminated droplets (12),
The prepared contaminated droplets (12) are dropped at different positions.
It is characterized by that.
[0031]
The invention according to claim 19 is the invention according to any one of claims 10 to 18,
The contaminated droplet (12)
Dropping on the hydrophobic surface formed by removing the natural oxide film present on the surface of the first semiconductor substrate (10),
The contamination mark (14)
Contaminated droplets (12) dropped on the hydrophobic surface are formed by drying.
It is characterized by that.
[0032]
The invention according to claim 20 is the invention according to any one of claims 10 to 19,
The locally contaminated sample preparation step (S10)
1 to 100 μl of the contamination droplet (12) containing 1 pg to 100 ng of the contaminant is dropped to form the contamination mark (14) having a diameter of 0.1 to 10 mm.
It is characterized by that.
[0033]
The invention according to claim 21 is the invention according to any one of claims 10 to 20,
The contaminant is
Metal,
The contaminated droplet (12)
Selected from the group of hydrofluoric acid, ultrapure water and hydrofluoric acid + hydrogen peroxide water
It is characterized by that.
[0034]
The invention as set forth in claim 22
A semiconductor wafer that detects fluorescent X-rays (30) obtained by irradiating the semiconductor wafer (26) with X-rays (32) using a semiconductor detector (28) and measures the contamination density of the semiconductor wafer (26). In the contamination density measurement method of
A locally contaminated sample preparation step (in which a contaminated droplet (12) containing a contaminant is dropped on the surface of the first semiconductor substrate (10) to produce a locally contaminated sample (16) having a contamination mark (14) on the surface ( S10)
Local sample strength (I) obtained by irradiating the locally contaminated sample (16) prepared in the locally contaminated sample preparing step (S10) with X-rays (32). _DROP ) And the local sample strength (I _DROP ) And the droplet contamination amount (A) which is the contamination amount of the contaminated droplet (12). _DROP A calibration curve creating step (S12) for creating a calibration curve showing a correspondence relationship with
Local sample intensity distribution (I) obtained by irradiating the locally contaminated sample (16) produced in the locally contaminated sample producing step (S10) with X-rays (32) while changing the incident angle (θ). _DROP (Θ)) local sample intensity distribution measuring step (S14);
Fully contaminated sample preparation step (S16) of immersing the second semiconductor substrate (18) in the contaminated solution (20) containing the contaminant to prepare a fully contaminated sample (24) having a contaminated layer (22) on the surface. When,
Whole surface sample intensity distribution (I) obtained by irradiating the whole surface contaminated sample (24) prepared in the whole surface contaminated sample preparation step (S16) with X-rays (32) while changing the incident angle (θ). _IAP (Θ)) is a whole surface sample strength distribution measuring step (S18),
The local sample strength distribution (I) measured in the local sample strength distribution measuring step (S14). _DROP (Θ)) and the whole surface sample strength distribution (I) measured in the whole surface sample strength distribution measuring step (S18). _IAP (Θ)) in the high angle region (RH) of the incident angle (θ) and normalization, and local sample characteristics (α _DROP ) And overall sample characteristics (α _IAP ) And a standardization step (S19) for obtaining
Local sample characteristics (α) obtained in the normalization step (S19) _DROP ) And overall sample characteristics (α _IAP A relative relationship calculating step (S20) for calculating a relative relationship (α) with
Wafer strength (I) obtained by irradiating the semiconductor wafer (26) with X-rays (32) _WAFER ) To detect the wafer strength (S22),
While relatively moving the locally contaminated sample (16) and the semiconductor detector (28) prepared in the locally contaminated sample preparing step (S10) along the X-axis direction, the X-ray (32) is moved to the X-axis. An X-axis intensity distribution measuring step (S26) for measuring an X-axis intensity distribution (I (X)) obtained by irradiation in parallel with
While relatively moving the locally contaminated sample (16) and the semiconductor detector (28) prepared in the locally contaminated sample preparing step (S10) along the Y-axis direction, the X-ray (32) is moved to the X-axis. Y-axis intensity distribution measuring step (S28) for measuring the Y-axis intensity distribution (I (Y)) obtained by irradiation in parallel with
The X-axis intensity distribution (I (X)) measured by the X-axis intensity distribution measuring step (S26) and the Y-axis intensity distribution (I (Y)) measured by the Y-axis intensity distribution measuring step (S28). Using an effective opening area calculating step (S30) for calculating an effective opening area (W) of the semiconductor detector (28);
The calibration curve created by the calibration curve creation step (S12), the relative relationship (α) calculated by the relative relationship calculation step (S20), and the wafer strength (I) detected by the wafer strength detection step (S22). _WAFER ) And the effective opening area (W) calculated in the effective opening area calculating step (S30), the wafer contamination density (D _WAFER Wafer contamination density determination step (S32) for determining
It is characterized by comprising.
[0035]
The invention according to claim 23 is the invention according to claim 22,
The wafer contamination density determination step (S32)
Using the relative relationship (α) calculated in the relative relationship calculation step (S20), the local sample strength (I of the calibration curve created in the calibration curve creation step (S12)) _DROP ) And using the effective opening area (W) calculated in the effective opening area calculating step (S30), the droplet contamination amount (A _DROP ) Is a droplet contamination density (D) indicating the contamination density of the contamination droplet (12). _DROP ),
Wafer strength (I) detected by the wafer strength detection step (S22) _WAFER ) Is applied to the converted calibration curve, and the wafer contamination density (D _WAFER )
It is characterized by that.
[0036]
The invention described in claim 24 is the invention described in claim 23,
The relative relationship calculating step (S20)
(Formula 1)

α: Relative relationship, α _IAP : Whole surface sample characteristics, α _DROP : Local sample characteristics
Execute the above formula to calculate the relative relationship,
The local sample strength (I _DROP )
(Formula 2)

I: correction intensity, α: relative relationship, I _DROP : Local sample strength
Run the above formula,
The droplet contamination density (D _DROP )
(Formula 5)

D _DROP : Droplet contamination density, A _DROP : Amount of droplet contamination, W: Effective opening area
Calculate by executing the above formula
It is characterized by that.
[0037]
The invention described in claim 25 is the invention described in claim 22,
The wafer contamination density determination step (S32)
Using the relative relationship (α) calculated by the relative relationship calculating step (S20) and the effective opening area (W) calculated by the effective opening area calculating step (S30), the wafer strength detecting step (S22) is performed. Detected wafer strength (I _WAFER )
The correction intensity (I) obtained by the correction is applied to the calibration curve created in the calibration curve creation step (S12), and the wafer contamination density (D _WAFER )
It is characterized by that.
[0038]
The invention described in claim 26 is the invention described in claim 25,
The corrected intensity (I) is
(Formula 8)

I: correction intensity, α: relative relationship, I _WAFER : Wafer strength, effective opening area
Calculate by executing the above formula
It is characterized by that.
[0039]
The invention according to claim 27 is the invention according to any one of claims 22 to 26,
The locally contaminated sample preparation step (S10)
Preparing two or more of the contaminated droplets (12),
The prepared contaminated droplets (12) are dropped at different positions.
It is characterized by that.
[0040]
The invention according to claim 28 is the invention according to any one of claims 22 to 27,
The contaminated droplet (12)
Dropping on the hydrophobic surface formed by removing the natural oxide film present on the surface of the first semiconductor substrate (10),
The contamination mark (14)
Contaminated droplets (12) dropped on the hydrophobic surface are formed by drying.
It is characterized by that.
[0041]
The invention according to claim 29 is the invention according to any one of claims 22 to 28,
The locally contaminated sample preparation step (S10)
1 to 100 μl of the contamination droplet (12) containing 1 pg to 100 ng of the contaminant is dropped to form the contamination mark (14) having a diameter of 0.1 to 10 mm.
It is characterized by that.
[0042]
The invention according to claim 30 is the invention according to any one of claims 22 to 29,
The contaminant is
Metal,
The contaminated droplet (12)
Selected from the group of hydrofluoric acid, ultrapure water and hydrofluoric acid + hydrogen peroxide water
It is characterized by that.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0048]
(Summary of Invention)
The first feature of the present invention is that a locally contaminated sample and a whole surface contaminated sample are prepared, respectively, and the local sample characteristic α indicating the incident angle dependence of each sample with respect to X-rays. _DROP And overall sample characteristics α _IAP And using these relative relationships α, the wafer contamination amount A _WAFER Is determined (see FIG. 1).
[0049]
The second feature of the present invention is to measure the X-axis intensity distribution I (X) and the Y-axis intensity distribution I (Y) with respect to the X-ray of the locally contaminated sample to calculate the effective opening area W of the semiconductor detector, Using this, wafer contamination density D _WAFER Is to decide. (See FIG. 4).
[0050]
Due to the above feature, since a calibration curve created from a locally contaminated sample can be used directly, absolute calibration of the total reflection fluorescent X-ray apparatus becomes possible.
[0051]
(First form)
The first embodiment of the present invention is an invention for measuring the amount of contamination of a semiconductor wafer by utilizing the relative relationship between a locally contaminated sample and a whole surface contaminated sample.
[0052]
As mentioned above, there was no standard sample suitable for total reflection X-ray fluorescence analysis in the past, so to realize absolute calibration of total reflection X-ray fluorescence analysis, first select an appropriate standard sample. is required.
[0053]
The present inventors selected a locally contaminated sample from which a desired amount of contamination can be easily obtained as a standard sample for total reflection X-ray fluorescence analysis. A calibration curve created using this locally contaminated sample has few measurement errors and is easy to create.
[0054]
Here, the contaminants that cause contamination of the semiconductor wafer are uniformly attached to the surface of the semiconductor wafer, so that the contamination state differs from the locally contaminated sample. Therefore, in order to use the calibration curve for measuring the amount of contamination of the semiconductor wafer, it is necessary to take into account the difference in fluorescent X-ray intensity caused by the contamination state. In general, a difference in fluorescent X-ray intensity due to a contamination state appears as an incident angle dependency of X-rays.
[0055]
Therefore, the present inventors obtained the relative relationship between the incident angle dependency of the locally contaminated sample and the incident angle dependency of the whole surface contaminated sample, and applied the calibration curve using this correlation.
[0056]
The first embodiment of the present invention is an invention configured from the above viewpoint, and provides a technique for realizing absolute calibration of total reflection X-ray fluorescence analysis.
[0057]
FIG. 1 is a process diagram showing a configuration of a semiconductor wafer contamination amount measuring method according to the first embodiment of the present invention. Hereinafter, the configuration of the first embodiment will be described with reference to FIG.
[0058]
FIG. 2 is an operation explanatory diagram showing a production operation of the locally contaminated sample 16 executed in the locally contaminated sample producing step S10 shown in FIG. Hereinafter, the configuration of the locally contaminated sample preparation step S10 shown in FIG. 1 will be described with reference to FIG.
[0059]
In the locally contaminated sample preparation step S10, a contaminated droplet 12 containing a contaminant is dropped onto the surface of the first semiconductor substrate 10 (FIG. 1A), and the dropped contaminated droplet 12 is dried to cause a contamination mark 14. To form a locally contaminated sample (hereinafter referred to as “DROP” as necessary) having a locally contaminated surface. Here, DROP is an abbreviation for the droplet method, and can be used as a means for producing the locally contaminated sample 16.
[0060]
Preferably, the natural oxide film existing on the surface of the first semiconductor substrate 10 is removed, a hydrophobic surface is formed on the first semiconductor substrate 10, and the contaminated droplet 12 is dropped on the hydrophobic surface. As a means for removing the natural oxide film, a method using a fluorine-based compound such as VPD (vapor phase decomposition) can be used. As described above, when the contaminated droplet 12 is dropped on the hydrophobic surface, the contaminated droplet 12 is repelled on the hydrophobic surface, so that a fine contamination mark 14 can be formed.
[0061]
Moreover, it is preferable that the drying of the contaminated droplet 12 is natural drying, and the contamination mark is formed with a sufficiently small size with respect to the detection range (for example, 2 cm in diameter) of the semiconductor detector. For example, 1 to 100 μl of the contaminated droplet 12 containing 1 pg to 100 ng of the contaminant is dropped on the surface of the first semiconductor substrate 10 to form a contamination mark 14 having a diameter of 0.1 to 10 mm.
[0062]
Preferably, the contaminant is metal, and the contaminated droplet 12 is selected from the group of hydrofluoric acid, ultrapure water and hydrofluoric acid + hydrogen peroxide water. When the contaminated droplet 12 is composed of these hydrophilic solvents, the contaminated droplet 12 is easily repelled on the hydrophobic surface, and a suitable spherical shape is obtained.
[0063]
As shown in the figure, only one contamination mark 14 may be formed, or a plurality of contamination marks 14 having different contamination amounts may be formed. In this case, two or more types of contaminated droplets 12 having different concentrations are prepared, and the prepared contaminated droplets 12 are dropped at different positions on the first semiconductor substrate 10.
[0064]
At this time, each droplet is dropped at a position that does not overlap within the detection range of the semiconductor detector. Preferably, the droplets are dropped so that the shapes of the droplets are the same and only the concentrations are different. Thereby, a plurality of fluorescent X-ray intensities can be obtained from one locally contaminated sample, so that a calibration curve can be easily prepared. As an application example, a plurality of droplets containing different substances may be dropped.
[0065]
FIG. 3 is an operation explanatory diagram showing a fluorescent X-ray intensity detection operation executed by the calibration curve creation step S12 shown in FIG. Hereinafter, the configuration of the calibration curve creation step S12 shown in FIG. 1 will be described with reference to FIG.
[0066]
In the calibration curve creating step S12, the locally contaminated sample 16 is irradiated with X-rays 32, the fluorescent X-rays 30 obtained from the locally contaminated sample 16 are received by the semiconductor detector 28, and the received fluorescent X-rays 30 are received. Strength (hereinafter referred to as “local sample strength I _DROP "). This local sample strength I _DROP Detection of the contamination amount of the contaminated droplet 12 (hereinafter referred to as “droplet contamination amount A”). _DROP ”) While changing the local sample strength I _DROP And the corresponding relationship between the contaminated droplets 12 are obtained.
[0067]
FIG. 4 is a graph showing an example of a calibration curve created by the calibration curve creation step S12 shown in FIG. As shown in the figure, the calibration curve creation step S12 includes the local sample strength I. _DROP The vertical axis, droplet contamination amount A _DROP Plot the data on a plane with x as the horizontal axis to create a calibration curve. Here, in the calibration curve shown in FIG. _DROP The unit of <counts> is droplet contamination amount A _DROP The unit of is <atoms>.
[0068]
Since the relationship between the fluorescent X-ray intensity and the amount of pollutants is generally proportional, the proportional coefficient of the proportional relationship may be used as a calibration curve.
[0069]
FIG. 5 shows the local sample intensity distribution I executed by the local sample intensity distribution measuring step S14 shown in FIG. _DROP It is operation | movement explanatory drawing which shows the measurement operation | movement of ((theta)). Hereinafter, the configuration of the local sample strength distribution measurement step S14 shown in FIG. 1 will be described with reference to FIG.
[0070]
In the local sample intensity distribution measuring step S14, the surface of the locally contaminated sample 16 is irradiated with X-rays 32 while changing the incident angle θ, and the intensity distribution of the fluorescent X-rays 30 obtained from the locally contaminated sample 16 (hereinafter, referred to as “intensity distribution”). "Local sample strength distribution I _DROP (Θ) ”) is measured. The incident angle θ of X-rays can be changed by angle scanning. At this time, the range in which the incident angle θ is changed includes a low angle region RL that satisfies the total reflection condition and a high angle region RH that does not satisfy the total reflection condition.
[0071]
6 shows the local sample strength distribution I measured in the local sample strength distribution measuring step S14 shown in FIG. _DROP It is a graph which shows an example of ((theta)). As shown in the figure, the local sample strength distribution I measured in the local sample strength distribution measuring step S14. _DROP (Θ) has a broad intensity peak in the low-angle region RL, and the intensity gradually decreases when entering the high-angle region RH.
[0072]
Local sample strength distribution I _DROP The reason why (θ) has a distribution curve as shown in the figure is that the contamination mark 14 of the locally contaminated sample 16 has a small mountain shape. That is, in the low-angle region RL, the contamination mark 14 absorbs X-rays that are directly incident on the contamination marks 14 and X-rays that are once reflected from the surface of the first semiconductor substrate 10 and then enter the fluorescent region. The amount of X-rays increases. On the other hand, in the high-angle region RH, the contamination scar 14 does not absorb the X-rays incident after being reflected from the surface of the first semiconductor substrate 10, so that the amount of fluorescent X-rays is reduced. As a result, local sample strength distribution I _DROP (Θ) is a distribution curve as shown in FIG.
[0073]
FIG. 7 is an operation explanatory diagram showing an operation for producing the entire surface contamination sample 24 executed in the entire surface contamination sample preparation step S16 shown in FIG. Hereinafter, the configuration of the entire contamination sample preparation step S16 shown in FIG. 1 will be described with reference to FIG.
[0074]
In the whole surface contamination sample preparation step S16, the second semiconductor substrate 18 is immersed in a contamination solution 20 containing a contaminant (FIG. 5A), and a whole surface contamination sample 24 having a contamination layer 22 on the surface (hereinafter, necessary). (Shown as “IAP” in response) (FIG. 5B). Here, IAP (Immersion Alkaline Hydrogen Peroxide Solution) is an abbreviation of the contamination liquid immersion method, and can be used as a means for producing the entire contamination sample 24. As shown in the figure, the contamination layer 22 may be formed only on the surface of the second semiconductor substrate 18 or on the entire surface.
[0075]
FIG. 8 shows the entire surface sample intensity distribution I executed by the entire surface sample intensity distribution measuring step S18 shown in FIG. _IAP It is operation | movement explanatory drawing which shows the measurement operation | movement of ((theta)). Hereinafter, the configuration of the entire surface sample strength distribution measuring step S18 shown in FIG. 1 will be described with reference to FIG.
[0076]
In the whole surface sample intensity distribution measuring step S18, the surface of the whole surface contaminated sample 24 is irradiated with the X-rays 32 while changing the incident angle θ, and the intensity distribution of the fluorescent X-rays 30 obtained from the whole surface contaminated sample 24 (hereinafter referred to as the following). "Whole surface specimen strength distribution I _IAP (Θ) ”) is measured. The incident angle θ of the X-ray 32 is changed in the same manner as in the local sample intensity distribution measurement step S14 described above.
[0077]
9 shows the entire surface sample intensity distribution I measured in the entire surface sample intensity distribution measuring step S18 shown in FIG. _IAP It is a graph which shows an example of ((theta)). As shown in the figure, the entire surface sample intensity distribution I measured in the entire surface sample intensity distribution measuring step S18. _IAP (Θ) has a relatively steep intensity peak in the latter half of the low angle region RL and decreases in the high angle region RH.
[0078]
Whole surface sample intensity distribution I _IAP The reason why (θ) has a distribution curve as shown in the figure is that the contamination layer 22 of the entire surface contamination sample 24 is flat. That is, in the first half portion of the low-angle region RL, the amount of X-ray reflection is large, so the amount of fluorescent X-ray is small. However, as the X-ray incident angle θ increases, the amount of X-ray reflection decreases. The amount of X-rays increases. When the incident angle θ of X-rays enters the high-angle region RH, the total reflection condition is removed, and the amount of fluorescent X-rays decreases. As a result, local sample strength distribution I _DROP (Θ) is a distribution curve as shown in FIG.
[0079]
FIG. 10 shows local sample characteristics α derived by the normalization step S19 shown in FIG. _DROP And overall sample characteristics α _IAP And a graph showing an example of the relative relationship α calculated by the relative relationship calculation step S20 shown in FIG. Hereinafter, the configuration of the normalization step S19 shown in FIG. 1 and the relative relationship calculation step S20 shown in FIG. 1 will be described with reference to FIG.
[0080]
The normalization step S19 is a local sample strength distribution I. _DROP (Θ) and whole surface sample strength distribution I _IAP (Θ) is made to coincide with the high angle region RH and normalized to obtain local sample characteristics α _DROP And overall sample characteristics α _IAP And ask. Here, local sample strength distribution I _DROP (Θ) and whole surface sample strength distribution I _IAP The reason why (θ) matches with the high angle region RH is as follows.
[0081]
That is, in the low-angle region RL, the contamination mark 14 of the locally contaminated sample 16 absorbs X-rays reflected by the surface of the first semiconductor substrate 10, whereas the contaminated layer 22 of the entire surface contaminated sample 24 Since the X-ray reflected from the surface of the semiconductor substrate 18 is not absorbed, the local sample intensity I _DROP Is the overall sample strength I _IAP Bigger than.
[0082]
On the other hand, in the high-angle region RH, neither the contamination mark 14 of the local contamination sample 16 nor the contamination layer 22 of the entire contamination sample 24 absorbs X-rays reflected by the first semiconductor substrate 10 and the second semiconductor substrate 18, respectively. , Local sample strength I _DROP And overall sample strength I _IAP It is thought that the ratio is constant.
[0083]
Local sample strength I _DROP And overall sample strength I _IAP Since the ratio is determined by the ratio between the contamination density of the contamination mark 14 and the contamination density of the contamination layer 22, the ratio of the contamination density of the contamination mark 14 and the contamination density of the contamination layer 22 is set to 1, for example, local Sample strength I _DROP Values and overall sample strength I _IAP So that the value of the local sample intensity I is the same in the high-angle region RH. _DROP And overall sample strength I _IAP Is normalized, the relative relationship between the locally contaminated sample 16 and the entire contaminated sample 24 can be obtained. The curve obtained by this normalization shows the local sample characteristic α shown in the figure. _DROP And overall sample characteristics α _IAP It is.
[0084]
In the relative relationship calculating step S20, as shown in the figure, the local sample characteristic α at a predetermined incident angle, that is, the incident angle of the X-ray 32 irradiated to the locally contaminated sample 16 in the calibration curve creating step S12. _DROP And overall sample characteristics α _IAP Is calculated to obtain the relative relationship α.
[0085]
FIG. 11 shows the wafer strength I executed by the wafer strength detection step S22 shown in FIG. _WAFER It is operation | movement explanatory drawing which shows this detection operation | movement. Hereinafter, the configuration of the wafer strength detection step S22 shown in FIG. 1 will be described with reference to FIG.
[0086]
In the wafer intensity detection step S22, the semiconductor wafer 26 whose contamination amount is to be measured is irradiated with X-rays 32, the fluorescent X-rays 30 obtained from the semiconductor wafer 26 are received by the semiconductor detector 28, and the received fluorescence is detected. The intensity of X-ray 30 (hereinafter referred to as “wafer intensity I _WAFER "). Here, it is assumed that the incident angle of the X-ray 32 irradiated to the semiconductor wafer 26 is the same as the incident angle as a reference for calculating the relative relationship α. Therefore, the X-ray incident angle irradiated by the calibration curve creating step S12, the X-ray incident angle used by the relative relationship calculating step S20, and the X-ray incident angle irradiated by the wafer intensity detecting step S22 are the same. It becomes an angle. This angle is, for example, 0.05 ° which is generally used in total reflection fluorescent X-ray analysis.
[0087]
The wafer contamination amount determination step S24 shown in FIG. 1 includes the calibration curve obtained as described above, the relative relationship α, and the wafer strength I. _WAFER The amount of contamination of the semiconductor wafer 26 (hereinafter referred to as “wafer contamination amount A”) _WAFER ")". Wafer contamination A _WAFER Is determined by correcting the calibration curve using the relative relationship α or by changing the wafer intensity I. _WAFER This is done by correcting
[0088]
When correcting the calibration curve using the relative relationship α, the relative relationship calculating step S20 includes:
(Formula 1)

α: Relative relationship, α _IAP : Whole surface sample characteristics, α _DROP : Local sample characteristics
The above formula is executed to calculate the relative relationship α.
[0089]
The wafer contamination amount determination step S24 includes:
(Formula 2)

I: correction intensity, α: relative relationship, I _DROP : Local sample strength
By executing the above equation, the local sample intensity I, which is the vertical axis of the calibration curve shown in FIG. _DROP Is converted into corrected intensity I, and wafer intensity I _WAFER Is applied to the correction intensity I, and the wafer contamination amount A _WAFER To decide.
[0090]
Wafer strength I using relative relationship α _WAFER When correcting the relative relationship calculation step S20,
(Formula 3)

α: Relative relationship, α _DROP : Local sample characteristics, α _IAP : Whole surface sample characteristics
The above formula is executed to calculate the relative relationship α.
[0091]
The wafer contamination amount determination step S24 includes:
(Formula 4)

I: correction intensity, α: relative relationship, I _WAFER : Wafer strength
Execute the above formula to obtain wafer strength I _WAFER Is converted into a correction intensity I, and the correction intensity I is converted into the local sample intensity I of the calibration curve shown in FIG. _DROP Applied to the wafer contamination amount A _WAFER To decide.
[0092]
According to the first embodiment of the present invention described above, since the fluorescent X-ray intensity in the entire contamination state and the fluorescent X-ray intensity in the local contamination state are associated with each other, the reliability obtained with the locally contaminated sample 16 is high. A calibration curve can be used. As a result, absolute calibration of total reflection fluorescent X-ray analysis becomes possible.
[0093]
(Second form)
The second aspect of the present invention is an invention relating to correction of the sensitivity distribution of the semiconductor detector.
[0094]
When the local contamination sample 16 and the entire contamination sample 24 having the same contamination density are subjected to total reflection X-ray fluorescence analysis, the local sample intensity I obtained from the local contamination sample 16 is obtained. _DROP And the whole surface sample strength I obtained from the whole surface contamination sample 24 _IAP Are different values.
[0095]
This is because the semiconductor detector of the total reflection fluorescent X-ray device has a characteristic sensitivity distribution for each device. In other words, the opening diameter of the semiconductor detector is about 2 cm in diameter, and the detection sensitivity of fluorescent X-rays changes within the opening having a diameter of 2 cm. For example, in a typical semiconductor detector, the sensitivity is highest at the center of the aperture, and the sensitivity decreases as the distance from the center of the aperture increases.
[0096]
Due to the sensitivity distribution as described above, the local sample intensity I detected from the contamination mark 14 located at the center of the opening of the semiconductor detector. _DROP Is the intensity of the entire surface sample I detected from the contamination layer 22 uniformly distributed in the opening of the semiconductor detector. _IAP Bigger than.
[0097]
Therefore, even if the calibration curve created from the locally contaminated sample 16 is accurate, an accurate contamination density cannot be obtained if the sensitivity variation of the semiconductor detector is large. In addition, as described above, since the detection sensitivity of semiconductor detection differs depending on each device, the contamination density measured for each semiconductor detector may be different.
[0098]
Therefore, in the second embodiment of the present invention, the sensitivity distribution of the semiconductor detector is obtained to accurately measure the contamination density. Here, it should be further noted that the sensitivity distribution of the semiconductor detector is affected by the X-ray irradiation direction.
[0099]
The present inventors have repeated experiments for obtaining the sensitivity distribution of the semiconductor detector, and have found that the sensitivity distribution of the semiconductor detector has a two-dimensional distribution. Therefore, in order to accurately measure the contamination density of the semiconductor wafer, sensitivity calibration based on the two-dimensional distribution of the semiconductor detector is necessary.
[0100]
The second aspect of the present invention is an invention configured from the above viewpoint, and provides a technique for accurately obtaining a sensitivity distribution of a semiconductor detector and realizing absolute calibration of total reflection X-ray fluorescence analysis.
[0101]
FIG. 12 is a process diagram showing the configuration of the method for measuring the contamination density of a semiconductor wafer according to the second embodiment of the present invention. The configuration of the second embodiment of the present invention will be described below with reference to FIG.
[0102]
FIG. 13 is an operation explanatory diagram showing the measurement operation of the X-axis intensity distribution I (X) executed in the X-axis intensity distribution measurement step S26 shown in FIG. Hereinafter, the configuration of the X-axis intensity distribution measurement step S26 shown in FIG. 12 will be described with reference to FIG.
[0103]
In the X-axis intensity distribution measuring step S26, the local contamination sample 16 and the semiconductor detector 28 are relatively moved along the X-axis shown in FIG. The fluorescent X-rays 30 obtained from the locally contaminated sample 16 are received by the semiconductor detector 28, and the intensity distribution of the received fluorescent X-rays 30 (hereinafter referred to as “X-axis intensity distribution I (X)”) is measured. .
[0104]
FIG. 14 is a graph showing an example of the X-axis intensity distribution I (X) measured in the X-axis intensity distribution measuring step S26 shown in FIG. As shown in the figure, the X-axis intensity distribution I (X) has an intensity peak near the opening center of the semiconductor detector 28.
[0105]
FIG. 15 is an operation explanatory diagram showing a measurement operation of the Y-axis intensity distribution I (Y) executed by the Y-axis intensity distribution measurement step S28 shown in FIG. Hereinafter, the configuration of the Y-axis intensity distribution measurement step S28 shown in FIG. 12 will be described with reference to FIG.
[0106]
The Y-axis intensity distribution measurement step S28 irradiates X-rays 32 in parallel with the X-axis while moving the locally contaminated sample 16 and the semiconductor detector 28 along the Y-axis shown in FIG. The fluorescent X-rays 30 obtained from the locally contaminated sample 16 are received by the semiconductor detector 28, and the intensity distribution of the received fluorescent X-rays 30 (hereinafter referred to as “Y-axis intensity distribution I (Y)”) is measured. .
[0107]
FIG. 16 is a graph showing an example of the Y-axis intensity distribution I (Y) measured in the Y-axis intensity distribution measuring step S28 shown in FIG. As shown in the figure, the Y-axis intensity distribution I (Y) has an intensity peak in the vicinity of the center of the opening of the semiconductor detector 28, like the X-axis intensity distribution I (X), but the X-axis intensity distribution I ( X) is different from the shape of the distribution curve.
[0108]
FIG. 17 is a graph showing a state in which the effective opening area calculation step S30 shown in FIG. 12 has normalized the X-axis intensity distribution I (X) and the Y-axis intensity distribution I (Y). Hereinafter, the configuration of the effective opening area calculating step S30 shown in FIG. 12 will be described with reference to FIG.
[0109]
In the effective opening area calculation step S30, the peaks of the X-axis intensity distribution I (X) and the Y-axis intensity distribution I (Y) are obtained by optimization, and then each obtained peak value is set to 1, The distribution I (X) and the Y-axis intensity distribution I (Y) are normalized to obtain a distribution curve as shown in FIG.
[0110]
FIG. 18 is a graph showing the configuration of the three-dimensional profile 34 created by the effective opening area calculating step S30 shown in FIG. As shown in the figure, the effective opening area calculation step S30 creates a three-dimensional profile 34 with the intensity directions of the normalized X-axis intensity distribution I (X) and Y-axis intensity distribution I (Y) as the Z-axis. . This three-dimensional profile 34 shows the two-dimensional sensitivity distribution of the semiconductor detector 28, and the volume of the three-dimensional profile 34 becomes a substantial effective area of the semiconductor detector 28 (hereinafter referred to as “effective opening area W”).
[0111]
The volume of the three-dimensional profile can be generally obtained by two-dimensional integration. However, to perform two-dimensional integration, mesh-like two-dimensional multipoint measurement is required, so that the calculation time is enormous.
[0112]
Therefore, it is preferable to execute an ellipse approximation process in which the contour lines of the three-dimensional profile 34 are approximated by an ellipse and the area of the ellipse is integrated in the Z-axis direction.
[0113]
FIG. 19 is a conceptual diagram showing a configuration of contour lines of the three-dimensional profile 34 shown in FIG. As shown in the figure, the contour line F (Z) of the three-dimensional profile 34 has a length F. _X (Z) horizontal axis and length F _Y It can be represented as an ellipse consisting of the vertical axis of (Z).
[0114]
Therefore, the volume calculation by elliptic approximation is
(Formula 7)

V: Volume of the three-dimensional profile 34, π: Circumference ratio, F _X (Z): Length of horizontal axis of contour line, F _Y (Z): Length of contour line vertical axis
This can be done by executing the above formula.
[0115]
In the effective opening area calculation step S30, the volume of the three-dimensional profile 34 calculated as described above is set as the effective opening area W of the semiconductor detector 28.
[0116]
The wafer contamination density determination step S32 shown in FIG. 1 includes the calibration curve created by the calibration curve creation step S12, the effective aperture area W calculated by the effective aperture area calculation step S30, and the wafer intensity I detected by the wafer strength detection step S22. _WAFER And the contamination density of the semiconductor wafer 26 (hereinafter referred to as “wafer contamination density D”). _WAFER "). Wafer contamination density D _WAFER Is determined by correcting the calibration curve using the effective aperture area W or by changing the wafer intensity I. _WAFER This is done by correcting
[0117]
When correcting the calibration curve using the effective opening area W, the wafer contamination density determination step S32 includes:
(Formula 5)

D _DROP : Droplet contamination density, A _DROP : Amount of droplet contamination, W: Effective opening area
Executing the above formula, the amount of droplet contamination A in the calibration curve _DROP The contamination density of the contaminated droplet 12 (hereinafter referred to as “droplet contamination density D”). _DROP Wafer strength I _WAFER Is the local sample strength I of the calibration curve _DROP And the corresponding droplet contamination density D _DROP And the obtained droplet contamination density D _DROP Wafer contamination density D _WAFER And
[0118]
Wafer strength I using effective opening area W _WAFER When correcting the wafer contamination density determination step S32,
(Formula 6)

I: correction intensity, I _WAFER : Wafer strength, W: Effective opening area
Execute the above formula to obtain wafer strength I _WAFER Is converted into a correction intensity I, and the correction intensity I is converted into the local sample intensity I of the calibration curve shown in FIG. _DROP The corresponding droplet contamination amount A _DROP And the obtained droplet contamination amount A _DROP Wafer contamination density D _WAFER And
[0119]
Other configurations are the same as those of the first embodiment described above.
[0120]
According to the second embodiment of the present invention described above, based on the two-dimensional sensitivity distribution of the semiconductor detector 28, a calibration curve or wafer intensity I _WAFER Corrects the wafer contamination density D _WAFER Can be obtained. As a result, absolute calibration of total reflection fluorescent X-ray analysis becomes possible.
[0121]
(Third form)
The third aspect of the present invention is an invention for measuring the contamination density of a semiconductor wafer in consideration of both the incident angle dependency of X-rays and the sensitivity distribution of the semiconductor detector.
[0122]
As described above, the X-ray incident angle dependency and the sensitivity distribution of the semiconductor detector are different between the locally contaminated sample and the entire surface contaminated sample.
[0123]
Therefore, in order to obtain a truly accurate contamination density, it is desirable to apply a calibration curve in consideration of both the difference in the incident angle dependency of X-rays and the difference in sensitivity distribution of the semiconductor detector.
[0124]
The third aspect of the present invention is an invention configured from the above viewpoint, and provides a technique that suitably realizes absolute calibration of total reflection X-ray fluorescence analysis.
[0125]
FIG. 20 is a process diagram showing a first process of the contamination concentration measuring method according to the third embodiment of the present invention. As shown in the figure, in the third embodiment of the present invention, the relative relationship α is calculated using the configuration of the first embodiment.
[0126]
FIG. 21 is a process diagram showing a second process of the contamination concentration measuring method according to the third embodiment of the present invention. As shown in the figure, in the third embodiment of the present invention, the effective opening area W is calculated using the configuration of the second embodiment.
[0127]
Hereinafter, based on FIG. 20, the structure of the 3rd form of this invention is demonstrated.
[0128]
In the wafer contamination density determination step S32, the calibration curve created by the calibration curve creation step S12, the relative relationship α calculated by the relative relationship calculation step S20, and the wafer strength I detected by the wafer strength detection step S22. _WAFER And the effective opening area W calculated in the effective opening area calculation step S30, the wafer contamination density D _WAFER To decide. Wafer contamination density D _WAFER Is determined by correcting the calibration curve using the relative relationship α and the effective opening area W or by changing the wafer intensity I. _WAFER This is done by correcting
[0129]
When the calibration curve is corrected using the relative relationship α effective opening area W, the relative relationship calculation step S20 includes:
(Formula 1)

α: Relative relationship, α _IAP : Whole surface sample characteristics, α _DROP : Local sample characteristics
The above formula is executed to calculate the relative relationship α.
[0130]
Wafer contamination density determination step S32
(Formula 2)

I: correction intensity, α: relative relationship, I _DROP : Local sample strength
By executing the above equation, the local sample intensity I, which is the vertical axis of the calibration curve shown in FIG. _DROP Is converted to correction intensity I,
(Formula 5)

D _DROP : Droplet contamination density, A _DROP : Amount of droplet contamination, W: Effective opening area
Executing the above formula, the amount of droplet contamination A in the calibration curve _DROP Droplet contamination density D _DROP Wafer strength I _WAFER Is the local sample strength I of the calibration curve _DROP And the corresponding droplet contamination density D _DROP And the obtained droplet contamination density D _DROP Wafer contamination density D _WAFER And
[0131]
Wafer strength I using relative relationship α and effective aperture area W _WAFER When correcting the relative relationship calculation step S20,
(Formula 3)

α: Relative relationship, α _DROP : Local sample characteristics, α _IAP : Whole surface sample characteristics
The above formula is executed to calculate the relative relationship α.
[0132]
Wafer contamination density determination step S32
(Formula 8)

I: correction intensity, α: relative relationship, I _WAFER : Wafer strength, effective opening area
Execute the above formula to obtain wafer strength I _WAFER Is converted into a correction intensity I, and the correction intensity I is converted into the local sample intensity I of the calibration curve shown in FIG. _DROP The corresponding droplet contamination amount A _DROP And the obtained droplet contamination amount A _DROP Wafer contamination density D _WAFER And
[0133]
According to the third embodiment of the present invention described above, both the difference in X-ray incident angle dependency between the locally contaminated sample 16 and the entire surface contaminated sample 24 and the difference in sensitivity distribution of the semiconductor detector 28 are taken into account. , Wafer contamination density D _WAFER Can be obtained more accurately.
【Example】
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0134]
(Summary of Examples)
The relative X is obtained by normalizing the fluorescent X-ray intensity at the high angle of the whole surface contamination sample and the local contamination sample (see FIG. 10), and the X-axis distribution and Y-axis distribution of the semiconductor detector are measured to An effective opening area W is obtained (see FIG. 17), and these values are used to appropriately correct the calibration curve or the semiconductor detector count.
[0135]
(Preferred embodiment)
First, a locally contaminated sample as shown in FIG. 2 is prepared by the following procedure.
[0136]
(1) A semiconductor wafer serving as a base for a locally contaminated sample is loaded into a carrier.
[0137]
(2) The carrier is housed in a sealed container together with a beaker containing hydrofluoric acid and left for about 1 to 3 hours. As a result, the natural oxide film present on the surface of the semiconductor wafer is decomposed, and a hydrophobic surface is formed on the semiconductor wafer.
[0138]
(3) A standard solution for atomic absorption is diluted to prepare about 100 (1 to 1000 PPb) contamination solution, and about 10 (1 to 100) microliters is dropped on the hydrophobic surface using a micropipette.
[0139]
(4) Step 3 is repeated while changing the concentration of the contaminated liquid, and a plurality of contaminated liquids are dropped on the hydrophobic surface of the semiconductor wafer.
[0140]
(5) A semiconductor wafer on which a plurality of contaminated liquids are dropped is accommodated in a clean draft (clean booth) and naturally dried. Thereby, the contaminated liquid is dried, and a contamination mark having a diameter of 0.1 to 10 mm is formed on the surface of the semiconductor wafer.
[0141]
Next, a calibration curve is created using the locally contaminated sample produced by the above procedure. The calibration curve is created according to the following procedure.
[0142]
(1) The X-ray intensity obtained from each contamination mark is detected by irradiating each contamination mark formed on the surface of the locally contaminated sample with X-rays at an incident angle of 0.05 °.
[0143]
(2) The fluorescent X-ray intensity detected in the above step is plotted on the vertical axis and the contamination amount of each contamination mark is plotted on the horizontal axis, and a calibration curve as shown in FIG. 4 is created.
[0144]
Next, the X-ray incident angle dependence of the locally contaminated sample is measured. The incident angle dependency of the locally contaminated sample is measured in the following steps.
[0145]
(1) Intensity of fluorescent X-rays generated while placing a semiconductor detector directly above a contamination mark formed on a locally contaminated sample and irradiating X-rays in the range of 0 ° to 0.3 ° by angle scanning. Is detected.
[0146]
(2) Using the values detected in the above steps, create a graph as shown in FIG. _DROP Ask for.
[0147]
Next, a whole surface contaminated sample as shown in FIG. 7 is prepared by the following procedure.
[0148]
(1) A contaminated solution having the same concentration as the contaminated trace of the locally contaminated sample whose X-ray incident angle dependency is measured is prepared.
[0149]
(2) Immerse the semiconductor wafer that will be the substrate of the entire contaminated sample in the contaminated solution prepared in the above step.
[0150]
Next, the X-ray incident angle dependence of the whole surface contamination sample produced as described above is measured. The incident angle dependency of the whole surface contamination sample is measured in the following steps.
[0151]
(1) A semiconductor detector is disposed immediately above the entire surface contaminated sample, and the intensity of the generated fluorescent X-ray is detected while irradiating the X-ray in the range of 0 ° to 0.3 ° by angle scanning.
[0152]
(2) Using the values detected in the above steps, create a graph as shown in FIG. _IAP Ask for.
[0153]
Next, the relative relationship α between the locally contaminated sample and the entire surface contaminated sample is derived. The derivation of the relative relationship α is executed according to the following procedure.
[0154]
(1) Local sample characteristics α _DROP And overall sample characteristics α _IAP Is normalized at an arbitrary ratio and matched in the high angle region to create a graph as shown in FIG.
[0155]
(2) Local sample characteristic α when the incident angle of the graph created in the above step is 0.05 ° _DROP And overall sample characteristics α _IAP The ratio is obtained, and this is set as the relative relationship α.
[0156]
Next, the effective opening area W of the semiconductor detector is obtained by the following procedure.
[0157]
(1) A semiconductor detector is disposed immediately above a contamination mark formed on a locally contaminated sample, and X-rays are irradiated to the contamination mark at an incident angle of 0.05 ° to obtain fluorescence obtained from each contamination mark. X-ray intensity is detected.
[0158]
(2) While moving the semiconductor detector or the locally contaminated sample in the direction parallel to the X irradiation direction (X-axis direction), the above steps are repeated to create a graph as shown in FIG. The moving range at this time is a range including the opening diameter (for example, 2 cm) of the semiconductor detector.
[0159]
(3) While moving the semiconductor detector or the locally contaminated sample in the X irradiation direction and the orthogonal direction (Y-axis direction), the above step 1 is repeated to create a graph as shown in FIG. The moving range at this time is also a range including the opening diameter (for example, 2 cm) of the semiconductor detector.
[0160]
(4) Normalize the graph created in step 2 and the peak of the graph created in step 3 as 1, and create a graph as shown in FIG.
[0161]
(5) The graph after normalization created in step 4 is developed in a three-dimensional manner to create a three-dimensional profile as shown in FIG.
[0162]
(6) The volume of the three-dimensional profile created in step 1 is calculated by elliptic approximation (Formula 7), and the result is defined as the effective opening area W of the semiconductor detector.
[0163]
Next, the contamination density of the semiconductor wafer to be inspected is determined by the following procedure.
[0164]
(1) The vertical axis of the calibration curve is corrected using the relative relationship α obtained by executing the above-described procedure.
[0165]
(2) The horizontal axis of the calibration curve is corrected using the effective opening area W obtained by executing the above-described procedure.
[0166]
(3) The semiconductor wafer to be inspected is irradiated with X-rays at an incident angle of 0.05 °, and the fluorescent X-ray intensity obtained from the semiconductor wafer is detected.
[0167]
(4) The fluorescent X-ray intensity detected in step 3 is applied to the calibration curve corrected in steps 2 and 3 to determine the contamination density of the semiconductor wafer.
[0168]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a semiconductor wafer contamination amount measuring method, a contamination density measuring method, and a local contamination sample preparation method that are effective for simple and accurate measurement of the wafer contamination amount.
[0169]
In addition, according to the first aspect of the present invention, since the fluorescent X-ray intensity in the entire contamination state is correlated with the fluorescent X-ray intensity in the local contamination state, a highly reliable calibration created with the local contamination sample 16 A line can be used. As a result, absolute calibration of total reflection fluorescent X-ray analysis becomes possible.
[0170]
Further, according to the second embodiment of the present invention, based on the two-dimensional sensitivity distribution of the semiconductor detector 28, a calibration curve or a wafer intensity I _WAFER Corrects the wafer contamination density D _WAFER Can be obtained. As a result, absolute calibration of total reflection fluorescent X-ray analysis becomes possible.
[0171]
In addition, according to the third embodiment of the present invention, both the difference in X-ray incident angle dependency between the locally contaminated sample 16 and the entire surface contaminated sample 24 and the difference in sensitivity distribution of the semiconductor detector 28 are considered. Wafer contamination density D _WAFER Can be obtained more accurately.
[Brief description of the drawings]
FIG. 1 is a process diagram showing a configuration of a semiconductor wafer contamination amount measuring method according to a first embodiment of the present invention;
FIG. 2 is an operation explanatory view showing a production operation of a locally contaminated sample 16 executed in the locally contaminated sample producing step S10 shown in FIG.
FIG. 3 is an operation explanatory diagram showing a fluorescent X-ray intensity detection operation executed by a calibration curve creation step S12 shown in FIG.
FIG. 4 is a graph showing an example of a calibration curve created by the calibration curve creation step S12 shown in FIG.
5 is a local sample intensity distribution I executed by the local sample intensity distribution measuring step S14 shown in FIG. _DROP It is operation | movement explanatory drawing which shows the measurement operation | movement of ((theta)).
6 is a local sample strength distribution I measured in the local sample strength distribution measuring step S14 shown in FIG. _DROP It is a graph which shows an example of ((theta)).
7 is an operation explanatory view showing a manufacturing operation of the whole surface contamination sample 24 executed in the whole surface contamination sample preparation step S16 shown in FIG. 1. FIG.
8 is a whole surface sample intensity distribution I executed by the whole surface sample intensity distribution measuring step S18 shown in FIG. _IAP It is operation | movement explanatory drawing which shows the measurement operation | movement of ((theta)).
9 is an overall sample intensity distribution I measured in the overall sample intensity distribution measuring step S18 shown in FIG. _IAP It is a graph which shows an example of ((theta)).
10 shows local sample characteristics α derived by the normalization step S19 shown in FIG. _DROP And overall sample characteristics α _IAP And a graph showing an example of the relative relationship α calculated by the relative relationship calculation step S20 shown in FIG.
11 is a wafer strength I executed by the wafer strength detection step S22 shown in FIG. _WAFER It is operation | movement explanatory drawing which shows this detection operation | movement.
FIG. 12 is a process diagram showing a configuration of a semiconductor wafer contamination density measuring method according to a second embodiment of the present invention.
13 is an operation explanatory diagram showing a measurement operation of an X-axis intensity distribution I (X) executed in the X-axis intensity distribution measurement step S26 shown in FIG.
14 is a graph showing an example of an X-axis intensity distribution I (X) measured in the X-axis intensity distribution measuring step S26 shown in FIG.
FIG. 15 is an operation explanatory diagram showing a measurement operation of the Y-axis intensity distribution I (Y) executed by the Y-axis intensity distribution measurement step S28 shown in FIG.
16 is a graph showing an example of a Y-axis intensity distribution I (Y) measured in the Y-axis intensity distribution measuring step S28 shown in FIG.
17 is a graph showing a state in which the effective opening area calculating step S30 shown in FIG. 12 has normalized the X-axis intensity distribution I (X) and the Y-axis intensity distribution I (Y).
18 is a graph showing the configuration of a three-dimensional profile 34 created by the effective opening area calculating step S30 shown in FIG.
FIG. 19 is a conceptual diagram showing a configuration of contour lines of the three-dimensional profile shown in FIG.
FIG. 20 is a process diagram showing a first process of a contamination concentration measuring method according to the third embodiment of the present invention.
FIG. 21 is a process diagram showing a second process of the contamination concentration measuring method according to the third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... 1st semiconductor substrate, 12 ... Contamination droplet, 14 ... Contamination trace, 16 ... Local contamination sample, 18 ... 2nd semiconductor substrate, 20 ... Contamination solution, 22 ... Contamination layer, 24 ... Whole contamination sample, 26 ... Semiconductor wafer, 28 ... Semiconductor detector, 30 ... X-ray fluorescence, 32 ... X-ray, 34 ... Three-dimensional profile, S10 ... Local contamination sample preparation process, S12 ... Calibration curve preparation process, S14 ... Local sample intensity distribution measurement process , S16 ... Whole surface contamination sample preparation step, S18 ... Whole surface sample intensity distribution measurement step, S19 ... Normalization step, S20 ... Relative relationship calculation step, S22 ... Wafer strength detection step, S24 ... Wafer contamination amount determination step, S26 ... X-axis Intensity distribution measuring step, S28 ... Y-axis intensity distribution measuring step, S30 ... Effective opening area calculating step, S32 ... Wafer contamination density determining step, A _DROP ... Amount of droplet contamination, A _WAFER ... wafer contamination, D _DROP ... Drop contamination density, D _WAFER ... wafer contamination density, I ... correction intensity, I _DROP ... Local sample strength, I _DROP (Θ) ... Local sample strength distribution, I _IAP ... Total specimen strength, I _IAP (Θ) ... Whole surface sample strength distribution, I _WAFER ... wafer strength, I (X) ... X-axis intensity distribution, I (Y) ... Y-axis intensity distribution, RH ... high angle region, RL ... low angle region, W ... effective aperture area, α ... relative relationship, α _DROP ... Local sample characteristics, α _IAP ... Characteristics of the entire surface, θ ... incident angle

Claims (30)

A semiconductor wafer which detects fluorescent X-rays (30) obtained by irradiating a semiconductor wafer (26) with X-rays (32) using a semiconductor detector (28) and measures the amount of contamination of the semiconductor wafer (26). In the method for measuring the amount of contamination of
A locally contaminated sample preparation step (in which a contaminated droplet (12) containing a contaminant is dropped on the surface of the first semiconductor substrate (10) to produce a locally contaminated sample (16) having a contamination mark (14) on the surface ( S10)
The local sample strength (I _DROP ) obtained by irradiating the local contaminated sample (16) prepared in the local contaminated sample preparation step (S10) with X-rays (32) is detected, and the local sample strength (I _DROP ) and A calibration curve creating step (S12) for creating a calibration curve indicating a correspondence relationship with the droplet contamination amount (A _DROP ) which is the contamination amount of the contaminated droplet (12);
Local sample intensity distribution (I _DROP (θ) obtained by irradiating the locally contaminated sample (16) prepared in the local contaminated sample preparation step (S10) with X-rays (32) while changing the incident angle (θ). ) Local sample strength distribution measuring step (S14) for measuring,
Fully contaminated sample preparation step (S16) of immersing the second semiconductor substrate (18) in the contaminated solution (20) containing the contaminant to prepare a fully contaminated sample (24) having a contaminated layer (22) on the surface. When,
Whole surface sample intensity distribution (I _IAP (θ) obtained by irradiating the whole surface contaminated sample (24) prepared in the whole surface contaminated sample preparation step (S16) with X-rays (32) while changing the incident angle (θ). ) To measure the entire surface sample strength distribution (S18),
The local sample strength distribution (I _DROP (θ)) measured in the local sample strength distribution measurement step (S14) and the entire surface sample strength distribution (I _IAP (θ)) measured in the entire surface sample strength distribution measurement step (S18). In a high angle region (RH) of the incident angle (θ), and normalizing to obtain local sample characteristics (α _DROP ) and full surface sample characteristics (α _IAP );
A relative relationship calculating step (S20) for calculating a relative relationship (α) between the local sample characteristic (α _DROP ) and the entire surface sample characteristic (α _IAP ) obtained in the normalization step (S19); and the semiconductor wafer (26) Wafer intensity detection step (S22) for detecting the wafer intensity (I _WAFER ) obtained by irradiating X-rays (32) on the wafer;
The calibration curve created in the calibration curve creation step (S12), the relative relationship (α) calculated in the relative relationship calculation step (S20), and the wafer strength (I _WAFER ) detected in the wafer strength detection step (S22) And a wafer contamination amount determination step (S24) for determining a wafer contamination amount (A _WAFER ). The wafer contamination amount determination step (S24)
Using the relative relationship (α) calculated in the relative relationship calculation step (S20), the local sample strength (I _DROP ) of the calibration curve created in the calibration curve creation step (S12) is corrected,
2. The semiconductor according to claim 1, wherein the wafer contamination amount (A _WAFER ) is determined by applying the wafer intensity (I _WAFER ) detected in the wafer intensity detection step ( _{S <b> 22} ) to the calibration curve after correction. Method for measuring the amount of wafer contamination. The relative relationship calculating step (S20) includes (Equation 1)

α: Relative relationship, α _IAP : Whole surface sample characteristic, α _DROP : Local sample characteristic The above equation is executed to calculate the relative relationship, and the correction of the local sample strength (I _DROP ) is (Equation 2)

The method for measuring a contamination amount of a semiconductor wafer according to claim 2, wherein I: correction intensity, α: relative relationship, I _DROP : local sample intensity. In the wafer contamination amount determination step (S24), the wafer strength (I _WAFER ) detected in the wafer strength detection step (S22) is corrected using the relative relationship (α) calculated in the relative relationship calculation step (S20). And applying the correction intensity (I) obtained by the correction to the calibration curve created in the calibration curve creating step (S12) to determine the wafer contamination amount (A _WAFER ). 2. A method for measuring a contamination amount of a semiconductor wafer according to 1. The relative relationship calculating step (S20) includes (Equation 3)

α: Relative relationship, α _DROP : Local sample characteristic, α _IAP : Whole surface sample characteristic The above equation is executed to calculate the relative relationship, and the corrected intensity (I) is expressed by (Equation 4)

_{5. The} method for measuring the amount of contamination of a semiconductor wafer according to claim 4, wherein I: correction intensity, α: relative relationship, I _WAFER : wafer intensity. The local contamination sample preparation step (S10) is characterized in that two or more kinds of the contaminated droplets (12) are prepared, and the prepared contaminated droplets (12) are respectively dropped at different positions. The method for measuring a contamination amount of a semiconductor wafer according to claim 5. The contamination droplet (12) is dropped on a hydrophobic surface formed by removing a natural oxide film present on the surface of the first semiconductor substrate (10), and the contamination mark (14) is formed on the hydrophobic surface. The method for measuring a contamination amount of a semiconductor wafer according to any one of claims 1 to 6, wherein the contamination droplet (12) dropped on the surface is dried. In the local contamination sample preparation step (S10), 1 to 100 μl of the contaminated droplet (12) containing 1 pg to 100 ng of the contaminant is dropped to form the contamination mark (14) having a diameter of 0.1 to 10 mm. The method for measuring a contamination amount of a semiconductor wafer according to any one of claims 1 to 7, wherein: 9. The pollutant is a metal, and the contaminated droplet (12) is selected from the group consisting of hydrofluoric acid, ultrapure water, and hydrofluoric acid + hydrogen peroxide water. A method for measuring a contamination amount of a semiconductor wafer according to any one of the above. A semiconductor wafer that detects fluorescent X-rays (30) obtained by irradiating the semiconductor wafer (26) with X-rays (32) using a semiconductor detector (28) and measures the contamination density of the semiconductor wafer (26). In the contamination density measurement method, a contaminated droplet (12) containing a contaminant is dropped on the surface of the first semiconductor substrate (10) to produce a locally contaminated sample (16) having a contamination mark (14) on the surface. And detecting the local sample strength (I _DROP ) obtained by irradiating the locally contaminated sample (16) prepared in the locally contaminated sample preparing step (S10) with X-rays (32). A calibration curve creating step (S12) for creating a calibration curve showing the correspondence between the local sample strength (I _DROP ) and the droplet contamination amount (A _DROP ) which is the contamination amount of the contaminated droplet (12); , Local contamination sample preparation process ( 10) obtained by irradiating the X-ray (32) parallel to the X-axis while moving the locally contaminated sample (16) and the semiconductor detector (28) relatively along the X-axis. X-axis intensity distribution measuring step (S26) for measuring the X-axis intensity distribution (I (X)), the locally contaminated sample (16) prepared by the locally contaminated sample preparing step (S10), and the semiconductor detector (28). ) Are relatively moved along the Y-axis direction and the Y-axis intensity distribution (I (Y)) obtained by irradiating the X-ray (32) in parallel with the X-axis is measured. A measurement step (S28), an X-axis intensity distribution (I (X)) measured by the X-axis intensity distribution measurement step (S26), and a Y-axis intensity distribution (Y) measured by the Y-axis intensity distribution measurement step (S28) I (Y)) and the effective opening area (W) of the semiconductor detector (28) is calculated. Effective opening area calculation step and (S30), and the wafer intensity detecting step of detecting X-rays to the semiconductor wafer (26) (32) wafers intensity obtained by irradiating _{(I WAFER)} (S22), the calibration curve The calibration curve created in the creation step (S12), the effective aperture area (W) calculated in the effective aperture area calculation step (S30), and the wafer strength (I _WAFER ) detected in the wafer strength detection step (S22) And a wafer contamination density determination step (S32) for determining a wafer contamination density (D _WAFER ) using the method. The wafer contamination density determination step (S32) uses the effective opening area (W) calculated by the effective opening area calculation step (S30) to cause droplet contamination of the calibration curve created by the calibration curve creation step (S12). The amount (A _DROP ) is converted into a droplet contamination density (D _DROP ) indicating the contamination density of the contamination droplet (12), and the wafer intensity (I _WAFER ) detected in the wafer intensity detection step (S 22) is converted into the conversion. The method for measuring a contamination density of a semiconductor wafer according to claim 10, wherein the wafer contamination density (D _WAFER ) is determined by applying to a later calibration curve. The droplet contamination density (D _DROP ) is (Equation 5)

_{12. The} method of measuring contamination density of a semiconductor wafer according to claim 11, wherein the calculation is performed by executing the following formula: D _DROP : Droplet contamination density, A _DROP : Droplet contamination amount, W: Effective aperture area In the wafer contamination density determination step (S32), the wafer intensity (I _WAFER ) detected by the wafer intensity detection step (S22) using the effective opening area (W) calculated by the effective opening area calculation step (S30). And the correction intensity (I) obtained by the correction is applied to the calibration curve created by the calibration curve creation step (S12) to determine the wafer contamination density (D _WAFER ). The method for measuring a contamination density of a semiconductor wafer according to claim 10. The corrected intensity (I) is expressed by (Equation 6)

_{14. The} method for measuring a contamination density of a semiconductor wafer according to claim 13, wherein I: correction intensity, I _WAFER : wafer intensity, W: effective opening area are calculated by executing the above equation. The effective opening area calculating step (S30) includes the X-axis intensity distribution (I (X)) measured by the X-axis intensity distribution measuring step (S26) or the Y-axis measured by the Y-axis intensity distribution measuring step (S28). With the peak value of the intensity distribution (I (Y)) as 1, the X-axis intensity distribution (I (X)) and the Y-axis intensity distribution (I (Y)) are normalized, and the normalized X-axis intensity distribution A three-dimensional profile (34) is created with the intensity direction of (I (X)) and Y-axis intensity distribution (I (Y)) as the Z-axis, and the volume of the generated three-dimensional profile (34) is calculated, The volume obtained by calculation is defined as the effective opening area (W). The contamination density measuring method for a semiconductor wafer according to any one of claims 10 to 14, wherein: 16. The contamination density of a semiconductor wafer according to claim 15, wherein the volume is calculated by approximating contour lines of the three-dimensional profile (34) with an ellipse and integrating the area of the ellipse in the Z-axis direction. Measuring method. The calculation of the volume is (Equation 7)

V: Volume of the three-dimensional profile (34), π: Circumferential ratio, FX (Z): Length of the horizontal axis of the contour line, FY (Z): Length of the vertical axis of the contour line The contamination density measuring method for a semiconductor wafer according to claim 16. The said locally contaminated sample preparation process (S10) prepares two or more types of the said contaminated droplets (12), and each of the prepared contaminated droplets (12) is dripped at a different position, respectively. The method for measuring a contamination density of a semiconductor wafer according to claim 17. The contamination droplet (12) is dropped on a hydrophobic surface formed by removing a natural oxide film present on the surface of the first semiconductor substrate (10), and the contamination mark (14) is formed on the hydrophobic surface. The method for measuring a contamination density of a semiconductor wafer according to any one of claims 10 to 18, wherein the contamination droplets (12) dropped on the surface are dried. In the local contamination sample preparation step (S10), 1 to 100 μl of the contaminated droplet (12) containing 1 pg to 100 ng of the contaminant is dropped to form the contamination mark (14) having a diameter of 0.1 to 10 mm. The method for measuring a contamination density of a semiconductor wafer according to any one of claims 10 to 19, wherein: 21. The pollutant is a metal, and the contaminated droplet (12) is selected from the group of hydrofluoric acid, ultrapure water and hydrofluoric acid + hydrogen peroxide water. 10. A method for measuring a contamination density of a semiconductor wafer according to any one of the above. A semiconductor wafer that detects fluorescent X-rays (30) obtained by irradiating the semiconductor wafer (26) with X-rays (32) using a semiconductor detector (28) and measures the contamination density of the semiconductor wafer (26). In the contamination density measurement method, a contaminated droplet (12) containing a contaminant is dropped on the surface of the first semiconductor substrate (10) to produce a locally contaminated sample (16) having a contamination mark (14) on the surface. And detecting the local sample strength (I _DROP ) obtained by irradiating the locally contaminated sample (16) prepared in the locally contaminated sample preparing step (S10) with X-rays (32). A calibration curve creating step (S12) for creating a calibration curve showing the correspondence between the local sample strength (I _DROP ) and the droplet contamination amount (A _DROP ) which is the contamination amount of the contaminated droplet (12); , Local contamination sample preparation process ( (16), the local sample intensity distribution obtained by irradiating while changing the incident angle (theta) X-ray (32) (I _{DROP (theta)} 10) was prepared local contamination Sample local sample intensity to measure) In the distribution measuring step (S14), the second semiconductor substrate (18) is immersed in the contaminated solution (20) containing the contaminant, and the entire contaminated sample (24) having the contaminated layer (22) on the surface is prepared. Obtained by irradiating the entire contaminated sample (24) prepared in the entire contaminated sample preparation step (S16) and the entire contaminated sample preparation step (S16) with X-rays (32) while changing the incident angle (θ). A whole surface sample strength distribution measuring step (S18) for measuring a whole surface sample strength distribution (I _IAP (θ)), a local sample strength distribution (I _DROP (θ)) measured by the local sample strength distribution measuring step (S14), and , Surface intensity measurement of the entire surface Step (S18) to match the entire surface sample intensity distribution was measured _{(I IAP (θ))} and the high angle region of the incident angle (θ) (RH) was normalized, local sample properties (alpha _DROP) and entire sample characteristics (alpha _IAP) and the normalized step (S19) for obtaining the calculated relative relationship (alpha) of the local sample properties the normalized step (S19) is determined (alpha _DROP) and entire sample properties (alpha _IAP) Relative relationship calculation step (S20), wafer strength detection step (S22) for detecting wafer strength (I _WAFER ) obtained by irradiating the semiconductor wafer (26) with X-rays (32), and preparation of the locally contaminated sample While moving the locally contaminated sample (16) prepared in the step (S10) and the semiconductor detector (28) relatively along the X-axis direction, X-rays (32) are irradiated in parallel to the X-axis. X-axis intensity distribution ( X-axis intensity distribution measurement step (S26) for measuring I (X)), the local contamination sample (16) prepared in the local contamination sample preparation step (S10), and the semiconductor detector (28) in the Y-axis direction. A Y-axis intensity distribution measuring step (S28) for measuring a Y-axis intensity distribution (I (Y)) obtained by irradiating X-rays (32) in parallel with the X-axis while being moved relatively along The X-axis intensity distribution (I (X)) measured in the X-axis intensity distribution measuring step (S26), and the Y-axis intensity distribution (I (Y)) measured in the Y-axis intensity distribution measuring step (S28). The effective aperture area calculation step (S30) for calculating the effective aperture area (W) of the semiconductor detector (28), the calibration curve created by the calibration curve creation step (S12), and the relative relationship calculation The relative relationship (α) calculated in the step (S20) and the wafer strength detection process And (S22) is detected wafer intensity _{(I WAFER),} the effective opening area calculation step (S30) by using the effective opening area calculated (W) is a wafer contamination density to determine the wafer contamination density _{(D WAFER)} And a determination step (S32). A method for measuring a contamination density of a semiconductor wafer. The wafer contamination density determination step (S32) uses the relative sample strength (I) of the calibration curve created by the calibration curve creation step (S12) using the relative relationship (α) calculated by the relative relationship calculation step (S20). _DROP ) and the effective opening area (W) calculated in the effective opening area calculating step (S30) are used to calculate the droplet contamination amount (A _DROP ) of the calibration curve of the contaminated droplet (12). The wafer contamination density (D _DROP ) indicating the contamination density is converted, and the wafer intensity (I _WAFER ) detected in the wafer intensity detection step (S 22) is applied to the converted calibration curve to obtain the wafer contamination density (D _{23. The} method for measuring a contamination density of a semiconductor wafer according to claim 22, wherein _WAFER ) is determined. The relative relationship calculating step (S20) includes (Equation 1)

α: Relative relationship, α _IAP : Whole surface sample characteristic, α _DROP : Local sample characteristic The above equation is executed to calculate the relative relationship, and the correction of the local sample strength (I _DROP ) is (Equation 2)

I: Correction intensity, α: Relative relationship, I _DROP : Local sample intensity The above equation is executed and the droplet contamination density (D _DROP ) is expressed by (Equation 5)

_{24. The} method of measuring contamination density of a semiconductor wafer according to claim 23, wherein D _DROP : droplet contamination density, A _DROP : droplet contamination amount, W: effective opening area are calculated by executing the above equation. The wafer contamination density determination step (S32) uses the relative relationship (α) calculated by the relative relationship calculation step (S20) and the effective opening area (W) calculated by the effective opening area calculation step (S30). The wafer intensity (I _WAFER ) detected in the wafer intensity detection step (S22) is corrected, and the corrected intensity (I) obtained by the correction is added to the calibration curve created in the calibration curve creation step (S12). _{23. The} method for measuring a contamination density of a semiconductor wafer according to claim 22, wherein the wafer contamination density ( _DWAFER ) is determined by applying. The corrected intensity (I) is (Equation 8)

_{26. The} method for measuring a contamination density of a semiconductor wafer according to claim 25, wherein I: correction intensity, α: relative relationship, I _WAFER : wafer intensity, effective aperture area. 23. The local contamination sample preparation step (S10) is characterized in that two or more types of the contaminated droplets (12) are prepared, and the prepared contaminated droplets (12) are dropped at different positions. 27. A method for measuring contamination density of a semiconductor wafer according to claim 26. The contamination droplet (12) is dropped on a hydrophobic surface formed by removing a natural oxide film present on the surface of the first semiconductor substrate (10), and the contamination mark (14) is formed on the hydrophobic surface. The method for measuring a contamination density of a semiconductor wafer according to any one of claims 22 to 27, wherein the contamination droplets (12) dropped on the surface are dried. In the local contamination sample preparation step (S10), 1 to 100 μl of the contaminated droplet (12) containing 1 pg to 100 ng of the contaminant is dropped to form the contamination mark (14) having a diameter of 0.1 to 10 mm. The method for measuring a contamination density of a semiconductor wafer according to any one of claims 22 to 28, wherein: 30. The pollutant is a metal, and the contaminated droplet (12) is selected from the group of hydrofluoric acid, ultrapure water and hydrofluoric acid + hydrogen peroxide water. 10. A method for measuring a contamination density of a semiconductor wafer according to any one of the above.

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