JP4560898B2 - Inspection apparatus and inspection method - Google Patents

Description

【０１０４】
そして、式４及び式５からそれぞれ式３を除算すると、以下の式６及び式７となる。
【０１０５】
【数２】

【０１０６】
これら式６及び式７を変形すると、以下の式８及び式９となる。
【０１０７】
【数３】

【０１０８】
ここで、以下のように定義をする。
【０１０９】
【数４】

【０１１０】
このように定義して一次変換行列Ａについて解くと、以下の式１０となる。このように一次変換行列Ａは、３点の座標から求めることができる。
【０１１１】
【数５】

【０１１２】
また、上述した式７の代わりに、以下の式１１を用いるとする。
【０１１３】
【数６】

【０１１４】
この場合には、以下のように定義を行い、一次変換行列Ａについて解くと、式１０と同じ結果を得ることができる。
【０１１５】
【数７】

【０１１６】
〔カメラ座標系の原点座標Ｏ_A〕
つぎに、上述した式１におけるカメラ座標系の原点座標Ｏ_Aを求める場合の、検査装置の動作について説明する。原点座標Ｏ_Aの求め方としては、２つの方法がある。
【０１１７】
第１の方法は、メカニカル座標系における検査用ステージ２の中心座標Ｏ_Sが、この検査用ステージ２に備えられた冶具により識別できる場合に適用することができる。この場合には、先ず、この検査用ステージ２の中心座標Ｏ_Sが可視光用対物レンズ３４の視野に収まるように、Ｘステージ２０及びＹステージ２１を移動させる。そして、検査用ステージ２の中心座標を、カメラ座標系で取得し、この座標をＰ_Aとする。すると、上述した式１を用いて、以下の式１２と表すことができる。
【０１１８】
【数８】

【０１１９】
そして、画像処理用コンピュータ６０により、式１２を解くことによって、メカニカル座標系におけるカメラ座標系の原点座標Ｏ_Aを求めることができる。
【０１２０】
第２の方法は、検査用ステージ２に、メカニカル座標系における中心座標を示す冶具が備えられていない場合に適用することができる。この場合には、θステージ２２により、点Ｐを、可視光用対物レンズ３４の視野内で回転移動させる。このとき、画像処理用コンピュータ６０は、回転移動の前後における点Ｐの座標を、それぞれメカニカル座標系及びカメラ座標系で、Ｐ_M1，Ｐ_M2及びＰ_A1，Ｐ_A2として取得する。また、図９に示すように、メカニカル座標系における検査用ステージ２の原点座標Ｏ_Sからの点Ｐの位置ベクトルＰ_Sを、回転移動の前後において、それぞれＰ_S1，Ｐ_S2とする。このとき、これらＰ_S1とＰ_S2とには、以下の式１３のような関係が成立する。
【０１２１】
【数９】

【０１２２】
そこで、Ｐ_M1とＰ_M2とは、上述した式１と式１３とを用いて、以下の式１４及び式１５のように表すことができる。
【０１２３】
【数１０】

【０１２４】
次に、式１４及び式１５からＰ_S1を消去して、Ｏ_Aについて解くと、以下の式１６のようになる。
【０１２５】
【数１１】

【０１２６】
このように、メカニカル座標系におけるカメラ座標系の原点座標Ｏ_Aを半導体ウェハ１０１上の点を２点取得することにより求めることができる。すなわち、画像処理用コンピュータ６０により、式１６を解くことによって、原点座標Ｏ_Aを求めることができる。
【０１２７】
ところで、上述したようにして原点座標Ｏ_Aを求める場合には、点Ｐを画像内で回転移動させることから、回転角度θを大きくすることが困難である。しかしながら、原点座標Ｏ_Aの精度は、回転角度θに大きく依存する。このため、原点座標Ｏ_Aを高精度に求めるためには、点Ｐの位置を画像の範囲外まで大きく回転移動させることが有効となる。このように、点Ｐの位置を画像の範囲外まで回転移動させた場合には、以下で説明する方法により、原点座標Ｏ_Aを求めることができる。
【０１２８】
この場合には、θステージ２２により、点Ｐを、可視光用対物レンズ３４の視野の範囲外まで回転移動させた後に、画像の範囲外に移動した点Ｐが再び画像の範囲内に収まるように、Ｘステージ２０及びＹステージ２１を平行移動させる。
【０１２９】
このとき、画像処理用コンピュータ６０は、移動の前後における点Ｐの座標を、それぞれメカニカル座標系及びカメラ座標系で、Ｐ_M1，Ｐ_M2及びＰ_A1，Ｐ_A2として取得する。また、図１０に示すように、メカニカル座標系における検査用ステージ２の原点座標Ｏ_Sからの点Ｐの位置ベクトルＰ_Sを、移動の前後において、それぞれＰ_S1，Ｐ_S2とする。さらに、移動後のメカニカル座標系における検査用ステージ２の回転中心の座標をＯ_S2として取得する。すると、上述した式１５は、以下の式１７のように表すことができる。
【０１３０】
【数１２】

【０１３１】
そこで、上述した式１４及び式１７からＰ_S1を消去して、Ｏ_Aについて解くと、以下の式１８のようになる。
【０１３２】
【数１３】

【０１３３】
そして、画像処理用コンピュータ６０により、この式１８を解くことによって、原点座標Ｏ_Aを求めることができる。したがって、点Ｐの位置を画像の範囲外まで大きく回転移動させて、高精度に原点座標Ｏ_Aを求めることができる。
【０１３４】
以上で説明したようにして、メカニカル座標系からカメラ座標系への点Ｐの移動量の一次変換行列Ａを求め、上述した式１を用いてメカニカル座標系とカメラ座標系とを対応させることにより、装置の機械的・光学的な位置精度に依らず、メカニカル座標系とカメラ座標系とを高精度に且つ簡便に対応させることができる。
【０１３５】
〔レンズ間における補正〕
さらに、検査装置において、複数のレンズ間でキャリブレーションを行う方法について説明する。
【０１３６】
検査装置は、可視光用対物レンズ３４と、紫外光用対物レンズ３８とを備えている。また、各レンズ３４，３８には、それぞれ倍率の異なる対物レンズが交換可能に配設自在とされていてもよい。検査装置においてキャリブレーションを行う場合には、一次変換行列Ａ及びカメラ座標系の原点座標Ｏ_Aが、光学ユニット２６における各レンズ３４，３８毎に固有な行列であることから、複数設けられた各レンズに対して、それぞれ、一次変換行列Ａと原点座標Ｏ_Aとを求めることが必要となる。
【０１３７】
このとき、上述した操作を各レンズ３４，３８毎に対して行うことにより、一次変換行列Ａと原点座標Ｏ_Aを求めてもよいが、以下で説明する方法により、すでに求めた所定のレンズ（以下、第１のレンズという。）における一次変換行列をＡ₁、原点座標をＯ_A1として、これら一次変換行列Ａ₁及び原点座標Ｏ_A1に基づいて、他のレンズ（以下、第２のレンズという。）の一次変換行列Ａ₂及び原点座標Ｏ_A2を求めるとしてもよい。これにより、キャリブレーションに必要となる時間の短縮や、キャリブレーション精度の向上を図ることができる。
【０１３８】
〔レンズ間における一次変換行列の補正〕
例えば、同一の撮像カメラを用いて使用する対物レンズだけを切り換えるとする場合には、レンズの倍率精度が５％程度と比較的低いが、各レンズ間における倍率以外の成分、すなわち、回転方向成分や直交性などは全て等しい。したがって、上述した一次変換行列Ａ₁，Ａ₂には、以下の式１９に表すような関係が成立する。
【０１３９】
【数１４】

【０１４０】
ただし、この式１９において、ｋは、定数である。
【０１４１】
そこで、先ず、光学ユニット２６において、第１のレンズを用いて点Ｐを識別することにより、この第１のレンズにおける一次変換行列Ａ₁を、上述したような方法により求める。
【０１４２】
次に、光学ユニット２６で用いるレンズを第２のレンズに交換する。そして、この第２のレンズを用いて撮像する画像の範囲内で点Ｐの座標を平行移動させることにより、この点Ｐの座標を２点、画像処理用コンピュータ６０により、それぞれメカニカル座標系とカメラ座標系とで取得する。このとき、メカニカル座標系における２点の座標をＰ_M1，Ｐ_M2、カメラ座標系における２点の座標をＰ_A1，Ｐ_A2とし、以下のように定義する。
【０１４３】
【数１５】

【０１４４】
すると、上述した式８から、一次変換行列Ａ₁を以下の式２０のように表すことができる。
【０１４５】
【数１６】

【０１４６】
したがって、この式２０を解いて定数ｋを求め、上述した式１９を用いることにより、一次変換行列Ａ₁に基づいて、一次変換行列Ａ₂を求めることができる。
【０１４７】
検査装置は、画像処理用コンピュータ６０によって、以上で説明した方法により一次変換行列Ａ₂を求めることにより、所定のレンズにおける一次変換行列Ａ₁に基づいて、他のレンズにおける一次変換行列Ａ₂を点Ｐの座標を２点取得するだけで、求めることができ、キャリブレーションに必要となる時間の短縮や、キャリブレーション精度の向上を図ることができる。
【０１４８】
〔レンズ間における原点座標の補正〕
つぎに、複数のレンズ間において、すでに求めた第１のレンズにおける原点座標をＯ_A1として、この原点座標Ｏ_A1に基づいて、第２のレンズにおける原点座標Ｏ_A2を求める場合について説明する。
【０１４９】
この検査装置においては、各レンズにおける原点座標Ｏ_Aの精度があまり高くない場合に、この原点座標Ｏ_Aを各レンズ毎に求めると、レンズを切り換えた際に、撮像した画像における半導体ウェハ１０１上での位置が著しくずれてしまう虞れが生じる。したがって、すでに求めた第１のレンズにおける原点座標Ｏ_A1を基準として、第２のレンズにおける原点座標Ｏ_A2を求めることが望ましい。これにより、各レンズ間での原点座標の相対位置精度が、各レンズにおける原点座標の絶対位置精度に依存しなくなる。また、検査装置においては、検査用ステージ２上に載置される半導体ウェハの位置には、必ず誤差が含まれることから、各レンズ毎における原点座標の絶対位置精度よりも、レンズ間での原点座標の相対位置精度の方が重要となる。
【０１５０】
そこで、先ず、光学ユニット２６において、第１のレンズを用いて点Ｐを識別することにより、この第１のレンズにおける原点座標Ｏ_A1を、上述したような方法により求める。このとき、この第１のレンズで撮像した画像においては、図１１に示すように、一次変換行列がＡ₁であり、原点座標がＯ_A1であるとする。また、第１のレンズにおけるカメラ座標系における点Ｐの座標がＰ_A1であるとする。
【０１５１】
次に、光学ユニット２６で用いるレンズを第２のレンズに交換する。このとき、図１１に示すように、この第２のレンズで撮像した画像において、一次変換行列がＡ₂であり、この第２のレンズにおけるカメラ座標系における点Ｐの座標がＰ_A2であるとして、この点Ｐのメカニカル座標系における座標がＰ_Mであるとすると、上述した式１から、以下の式２１、式２２のように表すことができる。
【０１５２】
【数１７】

【０１５３】
そこで、式２１及び式２２によりＰ_Mを消去すると、以下の式２３のように、Ｏ_A1に基づいて、Ｏ_A2を求めることができる。
【０１５４】
【数１８】

【０１５５】
ところで、光学ユニット２６で用いるレンズを第２のレンズに交換した際に、この第２のレンズで撮像した画像内に点Ｐが存在しない場合が考えられる。この場合には、図１２に示すように、第２のレンズに交換後に、点Ｐが画像内に収まるように、検査用ステージ２を平行移動させる。このとき、移動前における点Ｐのメカニカル座標系での座標をＰ_M1とし、移動後における点Ｐのメカニカル座標系での座標をＰ_M2とすると、以下の式２４のように、Ｏ_A1に基づいて、Ｏ_A2を求めることができる。
【０１５６】
【数１９】

【０１５７】
以上で説明したように、検査装置においては、複数のレンズを備える場
合であっても、すでに求めた所定のレンズにおける一次変換行列Ａ₁、原点座標Ｏ_A1に基づいて、他のレンズの一次変換行列Ａ₂及び原点座標Ｏ_A2を求めることにより、キャリブレーションに必要となる時間の短縮や、キャリブレーション精度の向上を図ることができる。
【０１５８】
〔ステージ座標系とウェハ座標系との関連付け〕
次に、ステージ座標系からウェハ座標系への点Ｐの移動量の一次変換行列を行列Ｒとする。すると、
Ｐ_S＝ＲＰ_W＋Ｏ_W ・・・・式２５
により、ウェハ座標系とステージ座標系との対応付けを行うことができる。ここで、行列Ｒは、半導体ウェハ１０１の検査用ステージ２に対する回転方向のずれを表す。そして、
Ｐ_M＝Ａ^-1Ｐ_A＋Ｏ_A＝Ｏ_S＋Ｐ_S ・・・・式２６
であることから、
Ｏ_S＝Ａ^-1Ｐ_A＋Ｏ_A−Ｐ_S ・・・・式２７
Ｏ_S＝Ａ^-1Ｐ_A＋Ｏ_A−（ＲＰ_W＋Ｏ_W） ・・・・式２８
となり、カメラ座標系とウェハ座標系との対応付けが行われる。すなわち、半導体ウェハ１０１上の任意の点Ｐについて、ウェハ座標系における座標Ｐ_Wが与えられれば、これを上式に代入して、得られる結果の座標にＣＣＤカメラ４を移動させ、点ＰをＣＣＤカメラ４によって撮像することができる。ただし、これは、搬送機構が半導体ウェハ１０１を回動させずに検査用ステージ２に載置させた場合、すなわち、半導体ウェハ１０１が「標準の方向」となされて検査用ステージ２に支持されている場合である。
【０１５９】
〔「ＴＩＳ」測定に対応した座標変換〕
そして、この検査装置においては、「ＴＩＳ」の測定のため、図１３に示すように、「標準の方向」から、図１４に示すように、回転させて半導体ウェハを検査用ステージ２上に搬入したときに、その任意の角度に対しウェハ座標系からステージ座標系への変換をも実現するものである。
【０１６０】
すなわち、搬送機構による半導体ウェハ１０１の回動に相当する一次変換行列を行列Ｒ_Tとして、
Ｐ_R＝Ｒ_TＰ_W ・・・・式２９
とする。ここで、行列Ｒ_Tは、以下の式３０に示すものとなる。
【０１６１】
【数２０】

【０１６２】
あるいは、より一般的に、「標準の方向」を基準とした回転角度θ（rad）を用いると、行列Ｒ_Tは、以下の式３１に示すものとなる。
【０１６３】
【数２１】

【０１６４】
最終的な半導体ウェハ１０１の方向は、プリアライナ２７に対して指定する角度で決定されるが、この値は、オリエンテーションフラットの標準の方向（オリエンテーションマークロケーション）をどのように決めるかで変わる。ここでは、「（ＤＯＷＮ）」をオリエンテーションフラットの標準の方向と定めており、このときのプリアライメント角度は１８０°である。「（ＲＩＧＨＴ）」では、プリアライメント角度は９０°である。これを一般化すると、上記式３１における回転角度θに対して、プリアライナ２７に対する指定角度θ_A（rad）は、以下の式３２で表される。
【０１６５】
θ_A＝π−θ ・・・・式３２
そして、この行列Ｒ_Tを上述のファインアライメントの結果に導入すると、上述の式２５及び式２８より、以下の式３３及び式３４に示すように、搬送用ロボット６及びプリアライナ２７の動作も含めて、ウェハ座標系とステージ座標系との対応付けができる。
【０１６６】
Ｐ_S＝ＲＰ_R＋Ｏ_W＝ＲＲ_TＰ_W＋Ｏ_W ・・・・式３３
Ｏ_S＝Ａ^-1Ｐ_A＋Ｏ_A−（ＲＲ_TＰ_W＋Ｏ_W） ・・・・式３４
このように、カメラ座標系とウェハ座標系との対応付けを行うことにより、ウェハ座標系における半導体ウェハ１０１上の任意の点ＰをＣＣＤカメラ４によって撮像することができる。
【０１６７】
〔ダイピッチ移動〕
また、この検査装置においては、ＣＣＤカメラ４による半導体ウェハ１０１の表面の撮像において、検査用ステージの実際の移動と、ウェハ座標系、あるいは、ダイ座標系上での移動との対応付けも行うことができる。すなわち、半導体ウェハ１０１上における所定の方向及び距離の移動ベクトルを、ウェハ座標系においてＤ_Wと定義し、
Ｐ_D＝Ｒ_T（Ｐ_W＋Ｄ_W） ・・・・式３５
とすれば、上述の場合と同様に、
Ｐ_S＝ＲＰ_D＋Ｏ_W＝ＲＲ_T（Ｐ_W＋Ｄ_W）＋Ｏ_W ・・・式３６
により、搬送機構の動作及び半導体ウェハ１０１上における所定の方向及び距離の移動ベクトルも含めてウェハ座標系とステージ座標系との対応付けができ、
Ｏ_S＝Ａ^-1Ｐ_A＋Ｏ_A−（ＲＲ_T（Ｐ_W＋Ｄ_W）＋Ｏ_W）・・式３７
により、カメラ座標系とウェハ座標系との対応付けを行うことにより、ウェハ座標系において点Ｐから所定の方向及び距離にある点（Ｐ_W＋Ｄ_W）をＣＣＤカメラ４によって撮像することができる。
【０１６８】
ここで、Ｄ_Wを、半導体ウェハ１０１上におけるダイ（Ｄｉｅ）の間隔（ダイピッチ）に相当するベクトルとしておけば、いわゆる「ダイピッチ移動」を容易に行うことができる。例えば、図１５に示すように、オリエンテーションフラットの標準の方向が「（ＤＯＷＮ）」で、「ＴＩＳ」測定のために、をオリエンテーションフラットの方向が「（ＲＩＧＨＴ）」であるときににおいて、ダイピッチを（Ｄｘ，Ｄｙ）とすると、これに行列Ｒ_T（ＲＩＧＨＴ）をかけると、以下の式３７が得られる。
【０１６９】
【数２２】

【０１７０】
これは、ステージ座標系におけるダイピッチである。ここで、入力装置５３において、図１６に示すように、上下左右を示す移動キーがあった場合において、通常は、これらキーの上下左右が、そのまま検査用ステージ２を上から見たときの上下左右（すなわち、奥側、手前側、左側、右側）に対応して検査用ステージ２が駆動されるのであるが、この検査装置では、検査用ステージ２の動きは、行列Ｒ_Tを含み、さらに、ファインアライメントもなされた方向となる。
【０１７１】
例えば、この場合においては、入力値（ｘ，ｙ）＝（０，１）においては、検査用ステージ２の移動は、（０，−Ｄｘ）となり、入力値（ｘ，ｙ）＝（１，０）においては、検査用ステージ２の移動は、（Ｄｙ，０）となり、入力値（ｘ，ｙ）＝（０，−１）においては、検査用ステージ２の移動は、（０，Ｄｘ）となり、入力値（ｘ，ｙ）＝（−１，０）においては、検査用ステージ２の移動は、（−Ｄｙ，０）となる。
【０１７２】
また、この場合の検査用ステージ２上におけるダイ座標の移動分は、行列Ｒ_T（ＲＩＧＨＴ）^-1をかけることにより、例えば、入力値（ｘ，ｙ）＝（０，１）において、以下の式３８に示すように、（１，０）となる。
【０１７３】
【数２３】

【０１７４】
他の方向への移動についても、図１７に示すように、
入力値（ｘ，ｙ）＝（１，０）においては、ダイ座標の移動分は、（０，−１）となり、入力値（ｘ，ｙ）＝（０，−１）においては、ダイ座標の移動分は、（−１，０）となり、入力値（ｘ，ｙ）＝（−１，０）においては、ダイ座標の移動分は、（０，１）となる。
【０１７５】
〔この検査装置による効果〕
上述のように、本発明に係る検査装置においては、ＣＣＤカメラ４による撮像で得られた画像を用いて検査を行うにあたって、半導体ウェハ１０１が検査装置内に搬入される方向に対し、一律的な座標変換処理が可能になる。したがって、「ＴＩＳ」測定時においても、ファインアライメントによる変換処理と、ＣＣＤカメラ４及び検査用ステージ２についての座標変換処理を、通常の検査の場合と同様に行うことができる。また、搬入される方向の種類に応じた個別の処理を行う必要もなく、その種類の数にも依存することはない。
【０１７６】
このため、従来の検査装置において見られるような、半導体ウェハ１０１の回転に対して個別の座標変換処理を行う場合に比べて、変換処理回路におけるばらつきや個体差といったものによる影響を皆無とすることができる。
【０１７７】
さらに、ウェハ座標系から、メカニカル座標系やステージ座標系への変換以外にも、なんらかの変換処理を行う必要が生じた場合でも、半導体ウェハ１０１の回転方向ごとに追加の変換処理を行う必要がなく、良好な拡張性及び信頼性を確保することができる。
【０１７８】
【発明の効果】
上述のように、本発明に係る検査装置及び検査方法においては、撮像手段による撮像で得られた画像を用いて検査を行うにあたって、被検査物が検査装置内に搬入される方向に対し、一律的な座標変換処理が可能になる。したがって、「ＴＩＳ」測定時においても、ファインアライメントによる変換処理と、撮像手段及び被検査物支持機構についての座標変換処理を、通常の検査の場合と同様に行うことができる。また、搬入される方向の種類に応じた個別の処理を行う必要もなく、その種類の数にも依存することはない。
【０１７９】
このため、従来の検査装置において見られるような、被検査物の回転に対して個別の座標変換処理を行う場合に比べて、変換処理回路におけるばらつきや個体差といったものによる影響を皆無とすることができる。
【０１８０】
さらに、被検査物座標系から、メカニカル座標系や支持機構座標系への変換以外にも、なんらかの変換処理を行う必要が生じた場合でも、被検査物の回転方向ごとに追加の変換処理を行う必要がなく、良好な拡張性及び信頼性を確保することができる。
【０１８１】
すなわち、本発明は、検査装置が固有に持っている誤差の測定などのために、被検査物が複数の異なる方向となされて搬入される場合においても、この検査装置上の複数の座標系間の座標変換処理が容易であり、正確な誤差の測定が行えるようになされた検査装置及び検査方法を提供することができるものである。
【図面の簡単な説明】
【図１】本発明に係る検査装置の構成を概略的に示すブロック図である。
【図２】上記検査装置の構成を示す斜視図である。
【図３】上記検査装置の構成を示す縦断面図である。
【図４】上記検査装置の構成を示す平面図である。
【図５】上記検査装置の構成を示すブロック図である。
【図６】上記検査装置の光学ユニットの構成を示す側面図である。
【図７】上記検査装置における座標系の関係を示す平面図である。
【図８】上記検査装置において観察されたアライメントマークの例を示す平面図である。
【図９】上記検査装置において観察用ステージを回転させたときの座標の変化を示す平面図である。
【図１０】上記検査装置において観察用ステージを回転させ、さらに、平行移動したときの座標の変化を示す平面図である。
【図１１】上記検査装置において、撮像レンズの交換によりＣＣＤカメラの視野が変化したときの座標の変化を示す平面図である。
【図１２】上記検査装置において、撮像レンズの交換によりＣＣＤカメラの視野が変化し、さらに、観察用ステージを平行移動したときの座標の変化を示す平面図である。
【図１３】上記検査装置において、半導体ウェハのオリエンテーションフラットの方向が標準の方向であるときの状態を示す平面図である。
【図１４】上記検査装置において、「ＴＩＳ」の測定のため、半導体ウェハのオリエンテーションフラットの方向が右側方向となされた状態を示す平面図である。
【図１５】上記検査装置において、「ＴＩＳ」の測定のために、オリエンテーションフラットの方向が右側方向となされた半導体ウェハ上における座標を示す平面図である。
【図１６】入力装置における移動キーと、検査用ステージ２の移動方向のとの対応を示す平面図である。
【図１７】入力装置における移動キーと、検査用ステージ２上の半導体ウェハにおけるダイ座標の移動方向のとの対応を示す平面図である。
【符号の説明】
１ 基台、２ 検査用ステージ、３ 搬送機構、４ ＣＣＤカメラ、５ 制御回路、６ 搬送機構、７ カセット、８ 顕微鏡、９ カメラ移動機構、１０１
半導体ウェハ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inspection apparatus and an inspection method for inspecting the shape and size of a fine pattern such as a semiconductor wafer.
[0002]
[Prior art]
Conventionally, when fabricating a semiconductor integrated circuit, it has been a practice to form a number of identical device patterns (circuit patterns) on a semiconductor substrate called a semiconductor wafer, and then divide these into one device pattern portion. It has been broken. In recent years, semiconductor integrated circuits have been increasingly integrated, and device patterns constituting the semiconductor integrated circuits are very fine, for example, linear patterns with a width of 0.18 μm or 0.13 μm. It has become. This device pattern is optically inspected in the state of a semiconductor wafer, and conventionally, an inspection apparatus and an inspection method for performing such an inspection have been proposed.
[0003]
Such an inspection apparatus includes a base, an inspection object support mechanism provided on the base, and an imaging unit provided on the base so as to be movable. The inspection object support mechanism is a so-called “inspection stage” that supports an inspection object such as a semiconductor wafer and can move the inspection object within a predetermined moving plane. Yes. The imaging means is a so-called “CCD camera”, and images the inspection object from outside the moving plane of the inspection object.
[0004]
The imaging means enlarges and images the surface portion of the inspection object at a high magnification, and provides an image of a fine pattern such as a device pattern on the inspection object. Based on this image, it is possible to search for defects on the inspection object or measure the size (width) of the fine pattern.
[0005]
Here, if the coordinate system for moving the inspection object, the coordinate system for moving the imaging means, and the coordinate system defined on the inspection object are shifted from each other, Even if the location to be imaged is indicated by the coordinate system on the inspection object, it is very difficult to introduce the location into the imaging range (field of view) of the imaging device. It is difficult to make these coordinate systems coincide with each other according to machine accuracy. Therefore, the applicant of the present invention associates each of these coordinate systems in such an inspection apparatus, and performs a coordinate conversion process based on this association, so that the location to be imaged is within the imaging range of the image sensor. Japanese Patent Application No. 11-348079 has already proposed an inspection method that enables rapid introduction.
[0006]
By the way, when a precise inspection is performed on an object to be inspected, an error inherent in the inspection apparatus, for example, distortion of an image in an imaging unit may be a problem. This error is called “TIS” (Tool Induced Shift). As a method of quantitatively measuring this “TIS”, it is proposed to carry out the same inspection after inspecting the inspection object in different directions (orientations) and examine the distribution of the results. Has been.
[0007]
When measuring “TIS” in this way, the direction in which the inspection object is carried into the inspection apparatus is usually two directions, at most four directions. Therefore, conventionally, it has been dealt with by performing independent coordinate conversion processing for each direction of these inspection objects.
[0008]
[Problems to be solved by the invention]
By the way, in the measurement of “TIS” in the inspection apparatus as described above, the direction of the inspection object when the inspection object is carried into the inspection apparatus is, for example, more than four directions or until then. In the case of different directions, the coordinate conversion process becomes complicated, and a new error may be caused by performing the coordinate conversion process independently for each direction of the inspection object. Measurement was not possible.
[0009]
Therefore, the present invention has been proposed in view of the above-described circumstances, and an object to be inspected is carried in a plurality of different directions for measuring an error inherent in the inspection apparatus. Even in such a case, an object of the present invention is to provide an inspection apparatus and an inspection method in which coordinate conversion processing between a plurality of coordinate systems on the inspection apparatus is easy and accurate error measurement can be performed.
[0010]
[Means for Solving the Problems]
  In order to solve the above-described problems, an inspection apparatus according to the present invention includes a base and,On the base, Semiconductor waferAs well as supporting, Semiconductor waferWithin a given plane of movementAnd in a direction perpendicular to the plane of movementAn object support mechanism for moving the object;Semiconductor waferThe,By the object support mechanismSemiconductor waferRotate around the line perpendicular to the moving plane,A transport mechanism that is supported by the inspection object support mechanism, and is provided on the base so as to be movable with respect to the base, and is supported by the inspection object support mechanism from outside the moving plane.Semiconductor waferImaging means for visible light that captures images with visible lightSemiconductor waferAn optical unit having both an imaging means for ultraviolet light and imaging with UV light,An imaging means moving mechanism for moving the imaging means for visible light and ultraviolet light, and a control means for controlling the operations of the inspection object support mechanism, the transport mechanism, and the imaging means moving mechanism are provided.
[0011]
  The control means includes a mechanical coordinate system based on the base, a stage coordinate system whose origin is the reference point on the moving part of the inspection object support mechanism, and imaging in the visible light and ultraviolet light imaging means. A camera coordinate system based on the range;Semiconductor waferDefine the inspection object coordinate system with the center of the origin as the origin, and set the origin of the mechanical coordinate system to O_M(0, 0), and the coordinates of the reference point on the moving part of the object support mechanism in this mechanical coordinate system are O_SAnd the coordinates of the reference point of the imaging range by the imaging means for visible light and ultraviolet light in the mechanical coordinate system are O_AAnd in the stage coordinate systemSemiconductor waferThe coordinates of the center of_WAnd
[0012]
  And the control meansSemiconductor waferFor any point P above, the coordinates in the mechanical coordinate system are P_MAnd the coordinate in the camera coordinate system is P_AAnd the coordinate in the stage coordinate system is P_SAnd the coordinate in the inspection object coordinate system is P_Wage,The primary transformation matrix of the movement amount of the point P from the mechanical coordinate system to the camera coordinate system is A, the primary transformation matrix of the movement amount of the point P from the stage coordinate system to the inspection object coordinate system is R, and the transfer mechanismSemiconductor waferThe primary transformation matrix corresponding to the rotation of_TAs described below, the coordinate systems are associated with each other as follows. That is,
  P_M= A^-1P_A+ O_A
By associating the camera coordinate system with the mechanical coordinate system,
  P_S= A^-1P_A+ O_A-O_S
By associating the camera coordinate system with the stage coordinate system,
  P_S= RP_W+ O_W
By associating the inspection object coordinate system with the stage coordinate system,
  P_S= RR_TP_W+ O_W
By associating the inspection object coordinate system with the stage coordinate system, including the operation of the transport mechanism,
  O_S= A^-1P_A+ O_A-(RR_TP_W+ O_W)
Thus, the camera coordinate system and the inspection object coordinate system are associated with each other.
[0013]
  This inspection apparatus performs the association between the coordinate systems as described above, thereby allowing the imaging means for visible light and ultraviolet light to be in the inspection object coordinate system.Semiconductor waferMove to the position to pick up an arbitrary point P on the top, in the object coordinate systemSemiconductor waferAn arbitrary point P above is imaged by imaging means for visible light and ultraviolet light, and low resolution using visible light is obtained.Semiconductor waferInspection and high resolution using ultraviolet lightSemiconductor waferBoth the inspection and the lineThe imaging means for visible light and ultraviolet light each have a CCD camera that captures an image of the semiconductor wafer magnified by the objective lens, and an autofocus control unit that performs focus alignment of the objective lens, The autofocus control unit detects whether or not the distance between the objective lens and the semiconductor wafer matches the focal length of the objective lens, and moves the inspection object support mechanism in a direction perpendicular to a predetermined movement plane. Align the focus of the objective lensIt is characterized by this.
[0014]
  The inspection method according to the present invention is provided on a base.Semiconductor waferIn favor of thisSemiconductor waferWithin a given plane of movementAnd in a direction perpendicular to the plane of movementFor the object support mechanism to be moved, using the transport mechanism,Semiconductor waferIs supported so that it can be rotated relative to the base with a line perpendicular to the moving plane as an axis.Semiconductor waferImaging means for visible light that captures images with visible lightSemiconductor waferFrom the outside of the moving plane using the visible light imaging means and the ultraviolet light imaging means of the optical unit having both the ultraviolet light imaging means and the ultraviolet light imaging means.Semiconductor waferWhen shooting,A mechanical coordinate system based on the base, a stage coordinate system based on the reference point on the moving part of the inspection object support mechanism, and a camera based on the imaging range in the imaging means for visible light and ultraviolet light Coordinate system,Semiconductor waferDefine the inspection object coordinate system with the center of,The origin of the mechanical coordinate system is O_M(0, 0), and the coordinates of the reference point on the moving part of the object support mechanism in this mechanical coordinate system are O_SAnd the coordinates of the reference point of the imaging range by the imaging means for visible light and ultraviolet light in the mechanical coordinate system are O_AAnd in the stage coordinate systemSemiconductor waferThe coordinates of the center of_WAnd
[0015]
  AndSemiconductor waferFor any point P above, the coordinates in the mechanical coordinate system are P_MAnd the coordinate in the camera coordinate system is P_AAnd the coordinate in the stage coordinate system is P_SAnd the coordinate in the inspection object coordinate system is P_WWhenAndThe primary transformation matrix of the movement amount of the point P from the mechanical coordinate system to the camera coordinate system is A, the primary transformation matrix of the movement amount of the point P from the stage coordinate system to the inspection object coordinate system is R, and the transfer mechanismSemiconductor waferThe primary transformation matrix corresponding to the rotation of_TAs described below, the coordinate systems are associated with each other as follows. That is,
  P_M= A^-1P_A+ O_A
By associating the camera coordinate system with the mechanical coordinate system,
  P_S= A⁻1P_A+ O_A-O_S
By associating the camera coordinate system with the stage coordinate system,
  P_S= RP_W+ O_W
By associating the inspection object coordinate system with the stage coordinate system,
  P_S= RR_TP_W+ O_W
By associating the inspection object coordinate system with the stage coordinate system, including the operation of the transport mechanism,
  O_S= A^-1P_A+ O_A-(RR_TP_W+ O_W)
Thus, the camera coordinate system and the inspection object coordinate system are associated with each other.
[0016]
  In this inspection method, associating between the coordinate systems as described above, the imaging means for visible light and ultraviolet light are placed in the inspection object coordinate system.Semiconductor waferMove to the position to pick up an arbitrary point P on the top, in the object coordinate systemSemiconductor waferAn arbitrary point P above is imaged by imaging means for visible light and ultraviolet light, and low resolution using visible light is obtained.Semiconductor waferInspection and high resolution using ultraviolet lightSemiconductor waferBoth the inspection and the lineThe imaging means for visible light and ultraviolet light each have a CCD camera that captures an image of the semiconductor wafer magnified by the objective lens, and an autofocus control unit that performs focus alignment of the objective lens, The autofocus control unit detects whether or not the distance between the objective lens and the semiconductor wafer matches the focal length of the objective lens, and moves the inspection object support mechanism in a direction perpendicular to a predetermined movement plane. Align the focus of the objective lensIt is characterized by this.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
In this embodiment, the inspection apparatus according to the present invention is configured as an inspection apparatus for inspecting the line width of a device pattern in a semiconductor wafer on which a plurality of predetermined device patterns are formed. The inspection method according to the present invention is performed in this inspection apparatus. In this embodiment, the line width of a device pattern is inspected on a semiconductor wafer on which a plurality of predetermined device patterns are formed. This will be described as an inspection method.
[0019]
[Configuration of inspection equipment]
As shown in FIG. 1, this inspection apparatus is provided with a base 1 and a semiconductor wafer 101 which is provided on the base 1 and serves as an object to be inspected. An inspection stage (XYθ stage) 2 serving as an inspection object support mechanism for moving the wafer 101 in a predetermined movement plane (horizontal plane) is provided. The inspection stage 2 is controlled and driven by a control circuit 5 serving as a control unit, and the supporting semiconductor wafer 101 is translated in the X-axis direction and the Y-axis direction in the moving plane, and the inspection stage 2 A rotation operation is performed about an axis perpendicular to a moving plane passing through the reference point of the stage 2.
[0020]
In addition, this inspection apparatus rotates the semiconductor wafer 101 about a line perpendicular to the plane of movement of the semiconductor wafer 101 by the inspection stage 2 as an axis, and serves as a transfer robot 6 serving as a transfer mechanism that supports the inspection stage 2. It has. That is, the transfer robot 6 takes out one semiconductor wafer 101 from a plurality of semiconductor wafers stacked and accommodated in the cassette 7b, puts it in a predetermined direction, and places it on the inspection stage 2. Let The transfer robot 6 is also driven according to control by the control circuit 5.
[0021]
The inspection apparatus includes a CCD camera 4 serving as an imaging unit provided on the base 1 so as to be movable with respect to the base 1. The CCD camera 4 images the semiconductor wafer 101 supported by the inspection stage 2 from outside the moving plane of the semiconductor wafer 101 via the microscope 8. The CCD camera 4 is moved and operated in accordance with control by the control circuit 5 by a camera moving mechanism 9 serving as an imaging means moving mechanism.
[0022]
This inspection apparatus will be described in more detail including the appearance. As shown in FIG. 2, the inspection apparatus includes a clean unit 10 for keeping the environment for inspecting a semiconductor wafer clean. The clean unit 10 includes a clean box 11 formed by bending a stainless steel plate or the like and formed in a hollow box shape, and a clean air unit 12 integrally provided on the upper portion of the clean box 11. is doing.
[0023]
The clean box 11 is provided with a window portion 11a at a predetermined location, and an inspection worker can visually recognize the inside of the clean box 11 from the window portion 11a.
[0024]
The clean air unit 12 is for supplying clean air into the clean box 11. The clean air unit 12 includes two blowers 13 a and 13 b disposed at different positions on the upper portion of the clean box 11, and these blowers 13 a and 13 b. And an air filter (not shown) disposed between the clean box 11 and the clean box 11. The air filter is, for example, a high-performance air filter such as a HEPA filter (High Efficiency Particulate Air Filter) or a ULPA filter (Ultra Low Penetration Air Filter). The clean air unit 12 is configured to remove dust and the like in the air blown by the blowers 13a and 13b with a high-performance air filter and supply the clean box 11 as clean air.
[0025]
The clean box 11 is supported on the floor board by the support legs 14 and has a structure in which the lower end thereof is opened. The air supplied from the clean air unit 12 into the clean box 11 is mainly discharged from the lower end of the clean box 11 to the outside of the clean box 11. In addition, an opening area is provided at a predetermined position on the side surface of the clean box 11, and air supplied from the clean air unit 12 into the clean box 11 is provided on the side surface of the clean box 11. It is made to discharge | emit outside from an opening area | region.
[0026]
As described above, the clean unit 10 constantly supplies clean air from the clean air unit 12 into the clean box 11 and discharges air circulated in the clean box 11 as an air current to the outside of the clean box 11. . As a result, dust or the like generated in the clean box 11 is discharged to the outside of the clean box 11 together with this air, and the internal environment of the clean box 11 is kept at a very high cleanness of, for example, about class 1. . In the clean box 11, the internal atmospheric pressure is always kept at a positive pressure in order to prevent air including dust from entering the inside from the outside.
[0027]
As shown in FIG. 3, the inspection apparatus includes an apparatus main body 15 accommodated in a clean box 11, and a semiconductor wafer on which a predetermined device pattern is formed by the apparatus main body 15 in the clean box 11. 101 is inspected. Here, the semiconductor wafer 101 as an object to be inspected is transported in a predetermined hermetically sealed container 7 and transferred to the clean box 11 through the container 7. FIG. 3 shows a state where the inside of the clean box 11 is viewed from the direction of the arrow A1 in FIG.
[0028]
The container 7 includes a bottom portion 7a, a cassette 7b fixed to the bottom portion 7a, and a cover 7c that is detachably engaged with the bottom portion 7a and covers the cassette 7b. The semiconductor wafer 101 to be inspected is mounted on the cassette 7b so that a plurality of the semiconductor wafers 101 are overlapped with each other at a predetermined interval, and is sealed with the bottom 7a and the cover 7c.
[0029]
When the semiconductor wafer 101 is inspected, first, the container 7 containing the semiconductor wafer 101 is installed in a container installation space 16 provided at a predetermined position of the clean box 11. In the container installation space 16, the upper surface of the elevator 17 a of the elevator 17 is arranged so as to face the outside of the clean box 11, and the container 7 has a bottom portion 7 a located on the elevator 17 of the elevator 17. The container is installed in the container installation space 16.
[0030]
When the container 7 is installed in the container installation space 16, the engagement between the bottom 7a of the container 7 and the cover 7c is released. Then, the elevator platform 17a of the elevator 17 is moved downwardly as indicated by the arrow B in FIG. 3, whereby the bottom 7a and the cassette 7b of the container 7 are separated from the cover 7c and moved into the clean box 11. . As a result, the semiconductor wafer 101 is transferred into the clean box 11 without being exposed to the outside air.
[0031]
When the semiconductor wafer 101 is transferred into the clean box 11, the inspection target semiconductor wafer 101 is taken out from the cassette 7 b by the transfer robot 6 and inspected.
[0032]
In addition, as shown in FIG. 2, the inspection apparatus includes an external unit 50 in which a control circuit (computer) 5 for operating the apparatus main body 15 is accommodated. The external unit 50 is installed outside the clean box 11. In the external unit 50, a display device 51 for displaying an image taken of the semiconductor wafer 101, a display device 52 for displaying various conditions at the time of inspection, an instruction input to the device main body 15, and the like are performed. An input device 53 and the like are also provided. Then, an inspector who inspects the semiconductor wafer 101 inputs necessary instructions from the input device 53 disposed in the external unit 50 while looking at the display devices 51 and 52 disposed in the external unit 50. Perform an inspection.
[0033]
Next, the apparatus main body 15 disposed inside the clean box 11 will be described in more detail. As shown in FIG. 3, the apparatus main body 15 includes a base 1. The base 1 is a base for supporting each mechanism of the apparatus main body 15. A support leg 18 is attached to the bottom of the base 1, and each mechanism provided on the base 1 and the base 1 is supported on the floor plate independently of the clean box 11 by the support leg 18. It has a structure.
[0034]
On the base 1, an inspection stage 2 on which the semiconductor wafer 101 is placed is provided via a vibration isolation table 19. The vibration isolation table 19 is for suppressing vibration from the floor, vibration generated when the inspection stage 2 is moved, and the stone surface plate 19a on which the inspection stage 2 is installed. And a plurality of movable legs 19b that support the surface plate 19a. When the vibration is generated, the vibration isolation table 19 detects the vibration and drives the movable leg 19b, and the vibration of the stone surface plate 19a and the inspection stage 14 installed on the stone surface plate 19a. Will be canceled promptly.
[0035]
In order to stably install the inspection stage 2 on the vibration isolation table 19, it is desirable that the center of gravity of the vibration isolation table 19 is at a position that is somewhat low. Therefore, in this inspection apparatus, a notch 19c is provided at the lower end of the stone surface plate 19a, and the movable leg portion 19b supports the stone surface plate 19a at the notch 19c so that the vibration isolator 19 The center of gravity is lowered.
[0036]
Vibrations and the like generated when the inspection stage 2 is moved can be predicted to some extent in advance. If such vibration is predicted in advance and the vibration isolation table 19 is operated, it is possible to prevent the vibration generated in the inspection stage 2 from occurring. Therefore, it is desirable that the inspection apparatus is configured to operate the vibration isolation table 19 by predicting in advance vibrations or the like generated when the inspection stage 2 is moved.
[0037]
The inspection stage 2 is a stage for supporting the semiconductor wafer 101.
The inspection stage 2 has a function of supporting the semiconductor wafer 101 and moving the semiconductor wafer 101 to a predetermined inspection target position.
[0038]
That is, the inspection stage 2 includes an X stage 20 installed on the vibration isolation table 19, a Y stage 21 installed on the X stage 20, a θ stage 22 installed on the Y stage 21, and a θ stage. Z stage 23 installed on 22 and suction plate 24 installed on Z stage 23 are provided.
[0039]
The X stage 20 and the Y stage 21 are stages that move in the horizontal direction. The X stage 20 and the Y stage 21 move the semiconductor wafer 101 in directions orthogonal to each other, and the device pattern to be inspected is set at a predetermined inspection position. To lead to.
[0040]
The θ stage 22 is a so-called rotation stage and is for rotating the semiconductor wafer 101. When inspecting the semiconductor wafer, the semiconductor wafer 101 is rotated by the θ stage 22 so that, for example, the device pattern on the semiconductor wafer 101 is horizontal or vertical with respect to the screen.
[0041]
The Z stage 23 is a stage that moves in the vertical direction, and is for adjusting the height of the stage. During the inspection of the semiconductor wafer 101, the stage height is adjusted by the Z stage 23 so that the inspection surface of the semiconductor wafer has an appropriate height.
[0042]
The suction plate 24 is for sucking and fixing a semiconductor wafer to be inspected. During the inspection of the semiconductor wafer, the semiconductor wafer to be inspected is placed on the suction plate 24 and sucked by the suction plate 24, and unnecessary movement is suppressed.
[0043]
An optical unit 26 supported by a support member 25 is disposed on the vibration isolation table 19 so as to be positioned on the inspection stage 2. The optical unit 26 has a CCD camera and is used to capture an image of the semiconductor wafer 101 when the semiconductor wafer 101 is inspected. That is, the optical unit 26 has a function of capturing an image of the semiconductor wafer 101 with a low resolution using visible light and a function of capturing an image of the semiconductor wafer 101 with a high resolution using ultraviolet light. Have both.
[0044]
Moreover, as shown in FIGS. 3 and 4, the elevator 17 described above is provided on the base 1. Further, on the base 1, as shown in FIG. 4, a transfer robot 6 for transferring the semiconductor wafer 101, and its centering and phase before the semiconductor wafer 101 is placed on the inspection stage 2. A pre-aligner 27 is provided for carrying out. The elevator 17 moves the cassette 7b into the clean box 11 as described above.
[0045]
The transfer robot 6 has an operation arm 6b having a suction mechanism 6a provided at the tip, and the operation arm 6b is moved and sucked by the suction mechanism 6a provided at the tip. However, the semiconductor wafer is transported in the clean box 11.
[0046]
The pre-aligner 27 performs phase alignment and center alignment of the semiconductor wafer with reference to an orientation flat and a notch formed in advance on the semiconductor wafer 101. The inspection apparatus improves the inspection efficiency by performing phase alignment and the like by the pre-aligner 27 before placing the semiconductor wafer on the inspection stage 2.
[0047]
When the semiconductor wafer is placed on the inspection stage 2, first, the bottom portion 7 a and the cassette 7 b of the container 7 are moved into the clean box 11 by the elevator 17. Then, the semiconductor wafer 101 to be inspected is selected from the plurality of semiconductor wafers 101 stored in the cassette 7b, and the selected semiconductor wafer 101 is taken out from the cassette 7b by the transfer robot 6.
[0048]
The semiconductor wafer 101 taken out from the cassette 7 b is transferred to the pre-aligner 27 by the transfer robot 6. The semiconductor wafer 101 transferred to the pre-aligner 27 is phased and centered by the pre-aligner 27. Then, the semiconductor wafer 101 that has been phased out and centered is transported to the inspection stage 2 by the transport robot 6 and placed on the suction plate 24 for inspection.
[0049]
When the semiconductor wafer 101 to be inspected is transferred to the inspection stage 2, the semiconductor wafer 101 to be inspected next is taken out from the cassette 7 b by the transfer robot 23 and transferred to the pre-aligner 27. Then, while the semiconductor wafer 101 previously transported to the inspection stage 2 is being inspected, the semiconductor wafer to be inspected next is phased out and centered out. When the inspection of the semiconductor wafer 101 previously transferred to the inspection stage 2 is completed, the semiconductor wafer 101 to be inspected next is quickly transferred to the inspection stage 2.
[0050]
As described above, the inspection apparatus performs phase alignment and center alignment by the pre-aligner 27 in advance before the semiconductor wafer 101 to be inspected is transferred to the inspection stage 2, so that the semiconductor wafer by the inspection stage 2 is obtained. The time required for positioning 101 can be shortened. Further, this inspection apparatus takes out the semiconductor wafer 101 to be inspected next from the cassette 7b by using the time during which the semiconductor wafer 101 previously transported to the inspection stage 2 is inspected, and uses the prealigner 27. By performing phase alignment and center alignment, the overall time can be reduced, and inspection can be performed efficiently.
[0051]
By the way, in this inspection apparatus, as shown in FIG. 4, the elevator 17, the transfer robot 6, and the pre-aligner 27 are installed on the base 1 so as to be aligned on a straight line. The respective installation positions are determined such that the distance L1 between the elevator 17 and the transport robot 6 and the distance L2 between the transport robot 6 and the pre-aligner 27 are substantially equal. Further, the inspection stage 2 is positioned in a direction substantially orthogonal to the direction in which the elevator 17 and the pre-aligner 27 are arranged as viewed from the transfer robot 6.
[0052]
In this inspection apparatus, since each mechanism is arranged as described above, the semiconductor wafer 101 can be transported quickly and accurately. That is, in this inspection apparatus, the distance L1 between the elevator 17 and the transfer robot 6 and the distance L2 between the transfer robot 6 and the pre-aligner 27 are substantially equal to each other. The semiconductor wafer 101 taken out from the cassette 7b can be transferred to the pre-aligner 27 without changing the length of the arm 6b. Therefore, in this inspection apparatus, an error or the like that occurs when the length of the arm 6b of the transfer robot 6 is changed does not cause a problem, so that the operation of transferring the semiconductor wafer 101 to the pre-aligner 27 can be performed accurately. Further, since the elevator 17, the transfer robot 6 and the pre-aligner 27 are arranged in a straight line, the transfer robot 6 can transfer the semiconductor wafer taken out from the cassette 7b to the pre-aligner 27 only by a linear movement. . Therefore, in this inspection apparatus, the operation of transporting the semiconductor wafer 101 to the pre-aligner 27 can be performed very accurately and quickly.
[0053]
Further, in this inspection apparatus, since the inspection stage 2 is positioned in a direction substantially orthogonal to the direction in which the elevator 17 and the pre-aligner 27 are arranged as viewed from the transfer robot 6, the transfer robot 6 Moves linearly, the semiconductor wafer 101 can be transported to the inspection stage 2. Therefore, in this inspection apparatus, the operation of transporting the semiconductor wafer 101 to the inspection stage 2 can be performed very accurately and quickly. In particular, in this inspection apparatus, since the semiconductor wafer 101 on which a fine device pattern is formed is inspected, it is necessary to carry and position the semiconductor wafer 101 very accurately. Therefore, the above arrangement is very effective. It is.
[0054]
Next, the inspection apparatus will be described in more detail with reference to the block diagram of FIG. As shown in FIG. 5, the external unit 50 of the inspection apparatus has an image processing computer 60 to which a display device 51 and an input device 53a are connected, and a control circuit (a control circuit to which a display device 52 and an input device 53b are connected). Computer) 5. In FIG. 2 described above, the input device 53 a connected to the image processing computer 60 and the input device 53 b connected to the control circuit 5 are collectively shown as the input device 53.
[0055]
The image processing computer 60 is a computer that captures and processes an image captured of the semiconductor wafer 101 by a CCD (charge-coupled device) camera 4 installed in the optical unit 26 when the semiconductor wafer 101 is inspected. . That is, the inspection apparatus inspects the semiconductor wafer 101 by processing and analyzing the image of the semiconductor wafer 101 captured by the CCD camera 4 installed in the optical unit 26 by the image processing computer 60. .
[0056]
The input device 53a connected to the image processing computer 60 is used to input an instruction necessary for analyzing the image captured from the CCD camera 4 to the image processing computer 60. For example, It consists of a pointing device such as a mouse and a keyboard. The display device 51 connected to the image processing computer 60 is for displaying the analysis result of the image captured from the CCD camera 4, and is composed of, for example, a CRT display or a liquid crystal display.
[0057]
The control circuit 5 is a computer for controlling the inspection stage 2, the elevator 17, the transfer robot 6 and the pre-aligner 27, each device inside the optical unit 26 and the like when inspecting the semiconductor wafer 101. That is, when inspecting the semiconductor wafer 101, this inspection apparatus is controlled by the control circuit 5 so that an image of the semiconductor wafer 101 to be inspected is captured by the CCD camera 4 installed inside the optical unit 26. The inspection stage 2, the elevator 17, the transfer robot 6 and the pre-aligner 27, and the devices inside the optical unit 26 are controlled.
[0058]
The control circuit 5 has a function of controlling the blowers 13a and 13b of the clean air unit 12. That is, in this inspection apparatus, the control circuit 5 controls the blowers 13a and 13b of the clean air unit 12, so that clean air is always supplied into the clean box 11 when the semiconductor wafer 101 is inspected. Further, the air flow in the clean box 11 is controlled.
[0059]
The input device 53b connected to the control circuit 5 includes the inspection stage 2, the elevator 17, the transfer robot 6 and the pre-aligner 27, each device inside the optical unit 26, the blowers 13a and 13b of the clean air unit 12, and the like. Are input to the control circuit 5 and include, for example, a pointing device such as a mouse, a keyboard, and the like. The display device 52 connected to the control circuit 5 is for displaying various conditions at the time of inspection of the semiconductor wafer 101, and includes, for example, a CRT display, a liquid crystal display, or the like.
[0060]
The image processing computer 60 and the control circuit 5 can exchange data with each other by a memory link mechanism. In other words, the image processing computer 60 and the control circuit 5 are connected to each other via the memory link interfaces 60a and 5a provided respectively, and the image processing computer 60 and the control circuit 5 exchange data with each other. Communication is possible.
[0061]
On the other hand, in the inside of the clean box 11 of the inspection apparatus, as a mechanism for taking out the semiconductor wafer 101 that has been carried in a sealed container 7 from the cassette 7b of the container 7 and placing it on the inspection stage 2, As described above, the elevator 17, the transfer robot 6, and the pre-aligner 27 are arranged. These are connected to the control circuit 5 arranged in the external unit 50 via the robot control interface 5b. Then, a control signal is sent from the control circuit 5 to the elevator 17, the transfer robot 6 and the pre-aligner 27 via the robot control interface 5b.
[0062]
That is, when the semiconductor wafer 101 that has been carried in the sealed container 7 is taken out from the cassette 7b of the container 7 and placed on the inspection stage 2, the control circuit 5 through the robot control interface 5b. Control signals are sent to the elevator 17, the transport robot 6, and the pre-aligner 27. The elevator 17, the transfer robot 6 and the pre-aligner 27 operate based on this control signal, and as described above, the semiconductor wafer 101 transferred in the sealed container 7 is transferred to the cassette of the container 7. 7b, phase alignment and center alignment are performed by the pre-aligner 27, and placed on the inspection stage 2.
[0063]
The X stage 20, Y stage 21, θ stage 22, Z stage 23, and suction plate 24 are connected to the control circuit 5 disposed in the external unit 50 via a stage control interface 5c. Control signals are sent from the control circuit 5 to the X stage 20, Y stage 21, θ stage 22, Z stage 23, and suction plate 24 via the stage control interface 5c.
That is, when a semiconductor wafer is inspected, control signals are sent from the control circuit 5 to the X stage 20, Y stage 21, θ stage 22, Z stage 23, and suction plate 24 via the stage control interface 5c. The X stage 20, the Y stage 21, the θ stage 22, the Z stage 23, and the suction plate 24 operate based on this control signal. The X stage 20, Y stage 21, θ stage 22, and Z stage 23 move the semiconductor wafer 101 to a predetermined position, angle, and height.
[0064]
As the CCD camera 4 provided in the optical unit 26, a visible light CCD camera 4a and an ultraviolet light CCD camera 4b are installed. As a mechanism for capturing an image of the semiconductor wafer 101 with visible light, a visible light CCD camera 4a, a halogen lamp 32, a visible light optical system 33, a visible light objective lens 34, and a visible light auto lens. A focus control unit 35 is arranged. The visible light optical system 33 and the visible light objective lens 34 constitute the microscope 8.
[0065]
Then, when taking an image of the semiconductor wafer 101 with visible light, the halogen lamp 32 is turned on. Here, the drive source of the halogen lamp 32 is connected to the control circuit 5 disposed in the external unit 50 via the light source control interface 5d. A control signal is sent from the control circuit 5 to the drive source of the halogen lamp 32 via the light source control interface 5d. The halogen lamp 32 is turned on / off based on this control signal. The visible light from the halogen lamp 32 is applied to the semiconductor wafer 101 via the visible light optical system 33 and the visible light objective lens 34 to illuminate the semiconductor wafer 101. Then, the image of the semiconductor wafer 101 illuminated with visible light is magnified by the visible light objective lens 34, and the magnified image is captured by the visible light CCD camera 4a.
[0066]
Here, the visible light CCD camera 4a is connected to an image processing computer 60 disposed in the external unit 50 via an image capture interface 60b. The image of the semiconductor wafer 101 captured by the visible light CCD camera 4a is captured by the image processing computer 60 via the image capture interface 60b.
[0067]
Further, when an image of the semiconductor wafer 101 is picked up with visible light as described above, automatic focus position alignment is performed by the visible light autofocus control unit 35. That is, the visible light autofocus control unit 35 detects whether or not the distance between the visible light objective lens 34 and the semiconductor wafer 101 matches the focal length of the visible light objective lens 34. For this, the visible light objective lens 34 or the Z stage 23 is moved so that the inspection target surface of the semiconductor wafer 101 coincides with the focal plane of the visible light objective lens 34.
[0068]
Here, the visible light autofocus control section 35 is connected to the control circuit 5 disposed in the external unit 50 via an autofocus control interface 5e. A control signal is sent from the control circuit 5 to the visible light autofocus control section 35 via the autofocus control interface 5e. The automatic focus position adjustment of the visible light objective lens 34 by the visible light autofocus control unit 35 is performed based on this control signal.
[0069]
Further, inside the optical unit 26, as a mechanism for taking an image of a semiconductor wafer with ultraviolet light, an ultraviolet light CCD camera 4b, an ultraviolet light laser light source 36, an ultraviolet light optical system 37, and an ultraviolet light An optical objective lens 38 and an ultraviolet autofocus control unit 39 are provided. The ultraviolet light optical system 37 and the ultraviolet light objective lens 38 constitute the microscope 8.
[0070]
Then, when an image of the semiconductor wafer is taken with ultraviolet light, the ultraviolet light source 36 is turned on. Here, the drive source of the ultraviolet laser light source 36 is connected to the control circuit 5 disposed in the external unit 50 via the light source control interface 5d. Then, a control signal is sent from the control circuit 5 to the drive source of the ultraviolet laser light source 36 via the light source control interface 5d. The ultraviolet laser light source 36 is turned on / off based on this control signal.
[0071]
In addition, it is preferable to use the ultraviolet laser light source 36 that emits an ultraviolet laser having a wavelength of about 266 nm. An ultraviolet laser having a wavelength of about 266 nm is obtained as the fourth harmonic of a YAG laser. Further, laser light sources having an oscillation wavelength of about 166 nm have been developed, and such laser light sources may be used as the ultraviolet laser light source 36.
[0072]
When an image of the semiconductor wafer 101 is taken with ultraviolet light, the ultraviolet laser light source 36 is turned on, and the ultraviolet light from the ultraviolet laser light source 36 is passed through the ultraviolet light optical system 37 and the ultraviolet light objective lens 38. The semiconductor wafer 101 is illuminated through the semiconductor wafer 101. Then, the image of the semiconductor wafer 101 illuminated by the ultraviolet light is magnified by the ultraviolet light objective lens 38, and the magnified image is captured by the ultraviolet light CCD camera 4b.
[0073]
Here, the ultraviolet CCD camera 4b is connected to an image processing computer 60 disposed in the external unit 50 via an image capture interface 60c. The semiconductor wafer image captured by the ultraviolet CCD camera 4b is captured by the image processing computer 60 via the image capture interface 60c.
[0074]
Further, as described above, when an image of the semiconductor wafer 101 is picked up with ultraviolet light, the automatic focus position adjustment is performed by the ultraviolet light autofocus control unit 39. That is, the ultraviolet light autofocus control unit 39 detects whether or not the distance between the ultraviolet light objective lens 38 and the semiconductor wafer 101 matches the focal length of the ultraviolet light objective lens 38. In this case, the ultraviolet objective lens 38 or the Z stage 23 is moved so that the inspection target surface of the semiconductor wafer 101 coincides with the focal plane of the ultraviolet objective lens 38.
[0075]
Here, the ultraviolet autofocus control unit 39 is connected to the control circuit 5 disposed in the external unit 50 via an autofocus control interface 5e. Then, a control signal is sent from the control circuit 5 to the ultraviolet light autofocus control unit 39 via the autofocus control interface 5e. The automatic focusing position adjustment of the ultraviolet light objective lens 38 by the ultraviolet light autofocus control unit 39 is performed based on this control signal.
[0076]
Further, the clean air unit 12 is provided with two blowers 13a and 13b as described above. These blowers 13a and 13b are connected to the control circuit 5 disposed in the external unit 50 through an air volume control interface 5f. A control signal is sent from the control circuit 5 to the blowers 13a and 13b of the clean air unit 12 via the air volume control interface 5f. Control of the rotational speed of the blowers 13a and 13b, switching between on / off, and the like are performed based on this control signal.
[0077]
Next, the optical system of the optical unit 26 of this inspection apparatus will be described in more detail with reference to FIG. Here, description of the autofocus control units 35 and 39 is omitted, and an optical system for illuminating the semiconductor wafer 101 to be inspected and an optical system for imaging the semiconductor wafer 101 to be inspected will be described.
[0078]
As shown in FIG. 6, the optical unit 26 includes a halogen lamp 32, a visible light optical system 33, and a visible light objective lens 34 as an optical system for capturing an image of a semiconductor wafer with visible light. I have. Visible light from the halogen lamp 32 is guided to the visible light optical system 33 by the optical fiber 40. Visible light guided to the visible light optical system 33 first passes through the two lenses 41 and 42 and enters the half mirror 43. The visible light incident on the half mirror 43 is reflected by the half mirror 43 toward the visible light objective lens 34 and enters the semiconductor wafer 101 via the visible light objective lens 34. Thereby, the semiconductor wafer 101 is illuminated with visible light.
[0079]
The image of the semiconductor wafer 101 illuminated with visible light is enlarged by the visible light objective lens 34, passes through the half mirror 43 and the imaging lens 44, and is imaged by the visible light CCD camera 4 a. That is, the reflected light from the semiconductor wafer 101 illuminated by visible light is incident on the visible light CCD camera 4a via the visible light objective lens 34, the half mirror 43, and the imaging lens 44. An enlarged image 101 is captured by the visible light CCD camera 4a. Then, an image of the semiconductor wafer 101 (hereinafter referred to as a visible image) captured by the visible light CCD camera 4 a is sent to the image processing computer 60.
[0080]
The optical unit 26 includes an ultraviolet laser light source 36, an ultraviolet light optical system 37, and an ultraviolet light objective lens 38 as an optical system for capturing an image of a semiconductor wafer with ultraviolet light. . Ultraviolet light from the ultraviolet laser light source 36 is guided to the ultraviolet light optical system 37 by the optical fiber 45. The ultraviolet light guided to the ultraviolet light optical system 37 first passes through the two lenses 46 and 47 and enters the half mirror 48. The visible light incident on the half mirror 48 is reflected by the half mirror 48 toward the ultraviolet objective lens 38 and enters the semiconductor wafer 101 via the ultraviolet objective lens 38. Thereby, the semiconductor wafer 101 is illuminated with ultraviolet light.
[0081]
The image of the semiconductor wafer 101 illuminated with ultraviolet light is magnified by the ultraviolet light objective lens 38, transmitted through the half mirror 48 and the imaging lens 49, and imaged by the ultraviolet light CCD camera 4b. That is, the reflected light from the semiconductor wafer 101 illuminated by the ultraviolet light enters the ultraviolet CCD camera 4b through the ultraviolet objective lens 38, the half mirror 48, and the imaging lens 49, and thereby the semiconductor wafer. An enlarged image 101 is picked up by the CCD camera 4b for ultraviolet light. Then, an image of the semiconductor wafer 101 (hereinafter referred to as an ultraviolet image) picked up by the ultraviolet light CCD camera 4 b is sent to the image processing computer 60.
[0082]
In the inspection apparatus as described above, the image of the semiconductor wafer 101 can be captured and inspected with ultraviolet light, which is light having a shorter wavelength than visible light. Compared to the case of detection, more accurate line width measurement and finer defect detection can be performed.
[0083]
In addition, this inspection apparatus has both an optical system for visible light and an optical system for ultraviolet light, and the semiconductor wafer 101 is inspected at low resolution using visible light, and high in intensity using ultraviolet light. Both the inspection of the semiconductor wafer 101 with resolution can be performed. Therefore, in this inspection apparatus, a wide line width is measured and a large defect is detected by inspecting the semiconductor wafer 101 with low resolution using visible light, and a semiconductor with high resolution using ultraviolet light is used. By inspecting the wafer 101, it is possible to measure a narrow line width or detect a small defect.
[0084]
In this inspection apparatus, the numerical aperture (NA) of the ultraviolet light objective lens 38 is preferably large, for example, 0.9 or more. Thus, by using a lens having a large numerical aperture (NA) as the ultraviolet objective lens 38, it becomes possible to measure a narrower line width and detect a finer defect.
[0085]
〔Calibration〕
Incidentally, in the inspection apparatus, the line width of the device pattern of the semiconductor wafer 101 to be inspected is extremely fine, for example, about 0.13 μm to 0.18 μm. In this inspection apparatus, the width of the line of the device pattern is measured based on an image obtained by imaging with the CCD camera 4, and the accuracy is required to be very high at 3σ within 3 nm.
[0086]
In order to realize such accuracy, it is important to correspond the position of the predetermined pattern identified in the image captured by the optical unit 26 with the position of the actual pattern on the semiconductor wafer 101 with high accuracy. Furthermore, for example, it is important to measure errors inherent in the inspection apparatus such as image distortion in the CCD camera 4, that is, “TIS” (Tool Induced Shift).
[0087]
In this inspection apparatus, as a method of quantitatively measuring “TIS”, the same inspection on the same location on the semiconductor wafer 101 is carried out after the inspection object is carried into the inspection apparatus in different directions (orientations). And examine the distribution of the results. The direction of the semiconductor wafer 101 is the direction in which the “orientation flat” and the “notch” formed in advance on the semiconductor wafer 101 are directed when the semiconductor wafer 101 is placed on the inspection stage 2. This is identified and designated for each cassette.
[0088]
Therefore, first, in this inspection apparatus, prior to actual measurement and inspection, calibration is performed as described below, so that the coordinate system of the base 1 provided with the inspection stage 2 and the optical unit 26 ( Hereinafter, the mechanical coordinate system is associated with a coordinate system in an image captured by the optical unit 26 (hereinafter referred to as a camera coordinate system).
[0089]
That is, in this inspection apparatus, the control circuit 5 defines a coordinate system based on the base 1 as a mechanical coordinate system, and defines a coordinate system with the reference point of the inspection stage 2 as the origin as a stage coordinate system. A coordinate system based on the imaging range (field of view) of the CCD camera 4 is defined as a camera coordinate system. The mechanical coordinate system and the stage coordinate system have parallel X-axis and Y-axis, and the same scale.
[0090]
In this inspection apparatus, the origin of the mechanical coordinate system is set to O, as shown in FIG._MWhen (0, 0), the coordinates of the reference point of the inspection stage 2 in the mechanical coordinate system, that is, the vector O_M→ O_SO_SAnd the coordinates of the reference point of the imaging range by the CCD camera 2 in the mechanical coordinate system, that is, the vector O_M→ O_AO_AAnd
[0091]
In the calibration algorithm described below, the reference point O_SDoes not necessarily coincide with the rotation center of the θ stage 22, and may be any fixed point where the position from the rotation center of the θ stage 22 is clear.
[0092]
The line width is measured at a predetermined location on the semiconductor wafer 101. The device pattern formed on the semiconductor wafer 101 is a pattern in which square regions called dies are arranged in parallel, that is, a repetitive pattern. For this reason, the position on the semiconductor wafer 101 can be specified using two coordinate systems of the die coordinates and the in-die coordinates. In all the dies, the device patterns formed at the points having the same in-die coordinates are the same.
[0093]
By combining these two coordinate systems, the wafer coordinate system is defined as the inspection object coordinate system having the center of the semiconductor wafer 101 as the origin. Then, the coordinates of the center of the semiconductor wafer 101 in the stage coordinate system, that is, the vector O_S→ O_WO_WAnd
[0094]
In order to inspect an arbitrary point P on the wafer coordinate system defined as described above, it is necessary to first convert from the wafer coordinate system to the stage coordinate system. As described above, the stage coordinate system is a coordinate system on the inspection stage 2 that supports the semiconductor wafer 101 and moves the semiconductor wafer 101 in parallel. When the semiconductor wafer 101 is ideally placed on the inspection stage 2 with its “orientation flat” or “notch” set as a standard direction, the stage coordinate system and the wafer coordinate system completely coincide. . However, since the semiconductor wafer 101 is actually placed on the inspection stage 2 with an error within 100 μm from the ideal position due to the operation accuracy of the transport mechanism, the stage coordinate system and the wafer coordinate system coincide with each other. do not do. The conversion from the wafer coordinate system to the stage coordinate system performed for the purpose of correcting such inconsistency is called fine alignment.
[0095]
That is, in this inspection apparatus, for an arbitrary point P on the semiconductor wafer 101, the coordinates in the mechanical coordinate system, that is, the vector O_M→ P to P_MAnd the coordinates in the camera coordinate system, that is, the vector O_A→ P to P_AAnd the coordinates in the stage coordinate system, that is, the vector O_S→ P to P_SAnd coordinates in the wafer coordinate system, ie, vector O_W→ P to P_WAnd
[0096]
Here, a primary transformation matrix of the amount of movement of the point P from the mechanical coordinate system to the camera coordinate system is defined as a matrix A. Then
P_M= A^-1P_A+ O_A  ・ ・ ・ ・ ・ ・ ・ Formula 1
Allows the camera coordinate system to be associated with the mechanical coordinate system,
P_S= A^-1P_A+ O_A-O_S  .... Formula 2
Thus, it is possible to associate the camera coordinate system with the stage coordinate system.
[0097]
The primary transformation matrix A includes transformation of inclination and orthogonality between the mechanical coordinate system and the camera coordinate system. The primary transformation matrix A and the origin coordinate O of the camera coordinate system_AIs a matrix unique to each light receiving lens in the optical unit 26, that is, each of the visible light objective lens 34 and the ultraviolet light objective lens 38. Therefore, in the calibration described below, the primary transformation matrix A and the origin coordinate O of the camera coordinate system._AMeans seeking.
[0098]
In the following, first, a case where calibration is performed on an image captured using the visible light objective lens 34 in the inspection apparatus will be described.
[0099]
[Primary transformation matrix A]
In the following, first, the operation of the image conversion apparatus 1 when obtaining the primary conversion matrix A in the above-described expression 1 will be described.
[0100]
First, an arbitrary point P is selected on the semiconductor wafer 101 fixedly supported on the inspection stage 2, and the X stage 20 and the Y stage 21 are moved so that the point P falls within the visual field of the visible light objective lens 34. Let As the point P, for example, as shown in FIG. 8, the alignment mark formed on the semiconductor wafer 101 may be identified by the image processing computer 60, and one point on the alignment mark may be set as the point P. . FIG. 8 shows a case where the alignment mark is formed as the letter “K”.
[0101]
Next, the position of the point P is translated by the X stage 20 and the Y stage 21 within the visual field of the visible light objective lens 34. Then, the coordinates of the point P are acquired by the image processing computer 60 using the mechanical coordinate system and the camera coordinate system, respectively. At this time, the coordinates of the three points in the mechanical coordinate system are P_M1, P_M2, P_M3, The coordinates of the three points in the camera coordinate system are P_A1, P_A2, P_A3And
[0102]
Then, it can represent like the following formula | equation 3 thru | or Formula 5 using Formula 1 mentioned above.
[0103]
[Expression 1]

[0104]
Then, when Equation 3 is divided from Equation 4 and Equation 5, respectively, Equation 6 and Equation 7 below are obtained.
[0105]
[Expression 2]

[0106]
When these equations 6 and 7 are modified, the following equations 8 and 9 are obtained.
[0107]
[Equation 3]

[0108]
Here, the definition is as follows.
[0109]
[Expression 4]

[0110]
If it defines in this way and it solves about the primary transformation matrix A, it will become the following formulas 10. Thus, the primary transformation matrix A can be obtained from the coordinates of three points.
[0111]
[Equation 5]

[0112]
Further, it is assumed that the following expression 11 is used instead of the expression 7 described above.
[0113]
[Formula 6]

[0114]
In this case, if the definition is made as follows and the primary transformation matrix A is solved, the same result as Expression 10 can be obtained.
[0115]
[Expression 7]

[0116]
[Origin coordinates O of camera coordinate system_A]
Next, the origin coordinate O of the camera coordinate system in Equation 1 described above is used._AThe operation of the inspection apparatus when obtaining the above will be described. Origin coordinate O_AThere are two methods for obtaining this.
[0117]
In the first method, the center coordinates O of the inspection stage 2 in the mechanical coordinate system are used._SHowever, it can be applied when it can be identified by a jig provided in the inspection stage 2. In this case, first, the center coordinates O of the inspection stage 2 are used._SThe X stage 20 and the Y stage 21 are moved so that is within the visual field of the visible light objective lens 34. Then, the center coordinates of the inspection stage 2 are acquired in the camera coordinate system, and these coordinates are set to P_AAnd Then, it can represent with the following formula | equation 12 using the formula 1 mentioned above.
[0118]
[Equation 8]

[0119]
Then, the origin coordinate O of the camera coordinate system in the mechanical coordinate system is solved by solving the equation 12 by the image processing computer 60._ACan be requested.
[0120]
The second method can be applied when the inspection stage 2 is not provided with a jig that indicates the center coordinates in the mechanical coordinate system. In this case, the point P is rotated and moved within the field of view of the visible light objective lens 34 by the θ stage 22. At this time, the image processing computer 60 sets the coordinates of the point P before and after the rotational movement in the mechanical coordinate system and the camera coordinate system, respectively._M1, P_M2And P_A1, P_A2Get as. Further, as shown in FIG. 9, the origin coordinates O of the inspection stage 2 in the mechanical coordinate system._SPosition vector P of point P from_SRespectively before and after the rotational movement._S1, P_S2And At this time, these P_S1And P_S2And the following relationship is established.
[0121]
[Equation 9]

[0122]
So P_M1And P_M2Can be expressed as the following Expression 14 and Expression 15 using Expression 1 and Expression 13 described above.
[0123]
[Expression 10]

[0124]
Next, from Equation 14 and Equation 15 to P_S1Is deleted and O_AIs solved as shown in Equation 16 below.
[0125]
## EQU11 ##

[0126]
Thus, the origin coordinate O of the camera coordinate system in the mechanical coordinate system_ACan be obtained by acquiring two points on the semiconductor wafer 101. That is, the origin coordinate O is obtained by solving the equation 16 by the image processing computer 60._ACan be requested.
[0127]
By the way, as described above, the origin coordinate O_AIs obtained, the point P is rotated in the image, so it is difficult to increase the rotation angle θ. However, the origin coordinate O_AThe accuracy of is largely dependent on the rotation angle θ. For this reason, the origin coordinate O_AIs obtained with high accuracy, it is effective to greatly rotate the position of the point P outside the range of the image. Thus, when the position of the point P is rotationally moved out of the range of the image, the origin coordinate O is obtained by the method described below._ACan be requested.
[0128]
In this case, after the point P is rotated and moved outside the field of view of the visible light objective lens 34 by the θ stage 22, the point P moved outside the image range is again within the image range. Then, the X stage 20 and the Y stage 21 are moved in parallel.
[0129]
At this time, the image processing computer 60 sets the coordinates of the point P before and after the movement in the mechanical coordinate system and the camera coordinate system, respectively._M1, P_M2And P_A1, P_A2Get as. Further, as shown in FIG. 10, the origin coordinates O of the inspection stage 2 in the mechanical coordinate system._SPosition vector P of point P from_SBefore and after the movement_S1, P_S2And Furthermore, the coordinates of the rotation center of the inspection stage 2 in the mechanical coordinate system after the movement are expressed as O._S2Get as. Then, Expression 15 described above can be expressed as Expression 17 below.
[0130]
[Expression 12]

[0131]
Therefore, from the above-mentioned formulas 14 and 17 to P_S1Is deleted and O_AIs solved as shown in Equation 18 below.
[0132]
[Formula 13]

[0133]
Then, by solving the equation 18 by the image processing computer 60, the origin coordinate O_ACan be requested. Therefore, the position of the point P is greatly rotated outside the range of the image, and the origin coordinates O are accurately detected._ACan be requested.
[0134]
As described above, the primary transformation matrix A of the amount of movement of the point P from the mechanical coordinate system to the camera coordinate system is obtained, and the mechanical coordinate system and the camera coordinate system are associated with each other using the above-described equation 1. The mechanical coordinate system and the camera coordinate system can be easily and accurately associated with each other regardless of the mechanical / optical positional accuracy of the apparatus.
[0135]
[Correction between lenses]
Further, a method for performing calibration between a plurality of lenses in the inspection apparatus will be described.
[0136]
The inspection apparatus includes a visible light objective lens 34 and an ultraviolet light objective lens 38. In addition, objective lenses having different magnifications may be interchangeably disposed on the lenses 34 and 38, respectively. When calibration is performed in the inspection apparatus, the primary transformation matrix A and the origin coordinate O of the camera coordinate system are used._AIs a matrix unique to each of the lenses 34 and 38 in the optical unit 26, so that a primary transformation matrix A and an origin coordinate O are respectively obtained for a plurality of lenses._AIt is necessary to ask.
[0137]
At this time, by performing the above-described operation for each of the lenses 34 and 38, the primary transformation matrix A and the origin coordinate O_AHowever, according to the method described below, the first-order transformation matrix of the predetermined lens (hereinafter referred to as the first lens) that has already been obtained is represented by A₁, The origin coordinate is O_A1These primary transformation matrices A₁And origin coordinate O_A1Based on the first transformation matrix A of the other lens (hereinafter referred to as the second lens)₂And origin coordinate O_A2You may ask for. Thereby, the time required for calibration can be shortened and the calibration accuracy can be improved.
[0138]
[Correction of linear transformation matrix between lenses]
For example, when only the objective lens to be used is switched using the same imaging camera, the magnification accuracy of the lens is relatively low, about 5%, but the components other than the magnification between the lenses, that is, the rotation direction component And orthogonality are all equal. Therefore, the above-described primary transformation matrix A₁, A₂In this case, the relationship represented by the following Expression 19 is established.
[0139]
[Expression 14]

[0140]
However, in Equation 19, k is a constant.
[0141]
Therefore, first, in the optical unit 26, by identifying the point P using the first lens, the primary conversion matrix A in the first lens is identified.₁Is obtained by the method as described above.
[0142]
Next, the lens used in the optical unit 26 is replaced with a second lens. Then, by translating the coordinates of the point P within the range of the image to be imaged using the second lens, the coordinates of the point P are converted into two points by the image processing computer 60 and the mechanical coordinate system and the camera, respectively. Acquired with the coordinate system. At this time, the coordinates of the two points in the mechanical coordinate system are P_M1, P_M2, The coordinates of two points in the camera coordinate system are P_A1, P_A2And defined as follows.
[0143]
[Expression 15]

[0144]
Then, from the above equation 8, the primary transformation matrix A₁Can be expressed as in Equation 20 below.
[0145]
[Expression 16]

[0146]
Therefore, by solving the equation 20 to obtain the constant k and using the equation 19 described above, the primary transformation matrix A₁Based on the linear transformation matrix A₂Can be requested.
[0147]
The inspection apparatus uses the image processing computer 60 to perform the primary transformation matrix A by the method described above.₂To obtain a linear transformation matrix A for a given lens.₁Based on the first order transformation matrix A in the other lens₂Can be obtained simply by acquiring two coordinates of the point P, and the time required for calibration can be shortened and the calibration accuracy can be improved.
[0148]
[Correction of origin coordinates between lenses]
Next, between the plurality of lenses, the origin coordinates in the first lens already obtained are expressed as O._A1This origin coordinate O_A1Based on the origin coordinate O in the second lens_A2A case of obtaining the above will be described.
[0149]
In this inspection apparatus, the origin coordinates O of each lens_AIf the accuracy of is not so high, this origin coordinate O_AFor each lens, there is a risk that the position of the captured image on the semiconductor wafer 101 will be significantly shifted when the lens is switched. Accordingly, the origin coordinate O in the first lens already obtained is obtained._A1With reference to the origin coordinate O in the second lens_A2Is desirable. Thereby, the relative position accuracy of the origin coordinates between the lenses does not depend on the absolute position accuracy of the origin coordinates in each lens. Further, in the inspection apparatus, since the position of the semiconductor wafer placed on the inspection stage 2 always includes an error, the origin between the lenses is more than the absolute position accuracy of the origin coordinates for each lens. The relative position accuracy of coordinates is more important.
[0150]
Therefore, first, the optical unit 26 identifies the point P using the first lens, whereby the origin coordinate O in the first lens is determined._A1Is obtained by the method as described above. At this time, in the image captured by the first lens, as shown in FIG.₁And the origin coordinate is O_A1Suppose that Further, the coordinate of the point P in the camera coordinate system of the first lens is P_A1Suppose that
[0151]
Next, the lens used in the optical unit 26 is replaced with a second lens. At this time, as shown in FIG. 11, in the image captured by the second lens, the primary transformation matrix is A₂The coordinates of the point P in the camera coordinate system of this second lens are P_A2, The coordinate of this point P in the mechanical coordinate system is P_MIf it is, it can represent like the following formula | equation 21 and formula 22 from the formula 1 mentioned above.
[0152]
[Expression 17]

[0153]
Therefore, P 21 is obtained by Equation 21 and Equation 22._MIs deleted, as shown in Equation 23 below, O_A1Based on O_A2Can be requested.
[0154]
[Expression 18]

[0155]
By the way, when the lens used in the optical unit 26 is replaced with the second lens, there may be a case where the point P does not exist in the image captured by the second lens. In this case, as shown in FIG. 12, after the replacement with the second lens, the inspection stage 2 is translated so that the point P is within the image. At this time, the coordinates of the point P before the movement in the mechanical coordinate system are P_M1And the coordinate of the point P after movement in the mechanical coordinate system is P_M2Then, as in Equation 24 below, O_A1Based on O_A2Can be requested.
[0156]
[Equation 19]

[0157]
As described above, in the inspection apparatus, when a plurality of lenses are provided,
Even if the primary transformation matrix A in the predetermined lens already obtained₁, Origin coordinate O_A1Based on the first-order transformation matrix A of other lenses₂And origin coordinate O_A2Therefore, the time required for calibration can be shortened and the calibration accuracy can be improved.
[0158]
[Association of stage coordinate system and wafer coordinate system]
Next, a primary conversion matrix of the amount of movement of the point P from the stage coordinate system to the wafer coordinate system is defined as a matrix R. Then
P_S= RP_W+ O_W                      .... Formula 25
Thus, it is possible to associate the wafer coordinate system with the stage coordinate system. Here, the matrix R represents a shift in the rotation direction of the semiconductor wafer 101 with respect to the inspection stage 2. And
P_M= A^-1P_A+ O_A= O_S+ P_S          .... Formula 26
Because
O_S= A^-1P_A+ O_A-P_S              .... Formula 27
O_S= A^-1P_A+ O_A-(RP_W+ O_W・ ・ ・ ・ Formula 28
Thus, the camera coordinate system and the wafer coordinate system are associated with each other. That is, for an arbitrary point P on the semiconductor wafer 101, the coordinates P in the wafer coordinate system_WIs substituted into the above equation, the CCD camera 4 is moved to the resulting coordinates, and the point P can be imaged by the CCD camera 4. However, this is because the transfer mechanism places the semiconductor wafer 101 on the inspection stage 2 without rotating it, that is, the semiconductor wafer 101 is set in the “standard direction” and supported by the inspection stage 2. This is the case.
[0159]
[Coordinate conversion corresponding to “TIS” measurement]
In this inspection apparatus, for the measurement of “TIS”, as shown in FIG. 13, the “standard direction” is rotated as shown in FIG. 14 to carry the semiconductor wafer onto the inspection stage 2. Then, the conversion from the wafer coordinate system to the stage coordinate system is also realized for the arbitrary angle.
[0160]
That is, a primary transformation matrix corresponding to the rotation of the semiconductor wafer 101 by the transport mechanism is expressed as a matrix R._TAs
P_R= R_TP_W                         .... Formula 29
And Where the matrix R_TIs as shown in Equation 30 below.
[0161]
[Expression 20]

[0162]
Or, more generally, if the rotation angle θ (rad) with reference to the “standard direction” is used, the matrix R_TIs shown in the following Expression 31.
[0163]
[Expression 21]

[0164]
The final direction of the semiconductor wafer 101 is determined by an angle designated with respect to the pre-aligner 27, but this value varies depending on how the standard direction (orientation mark location) of the orientation flat is determined. Here, “(DOWN)” is defined as the orientation flat standard direction, and the pre-alignment angle at this time is 180 °. In “(RIGHT)”, the pre-alignment angle is 90 °. When this is generalized, the specified angle θ with respect to the pre-aligner 27 with respect to the rotation angle θ in the above equation 31._A(Rad) is expressed by Equation 32 below.
[0165]
θ_A= Π-θ ··· Equation 32
And this matrix R_TIs introduced into the result of the fine alignment described above, the wafer coordinate system and the stage including the operations of the transfer robot 6 and the pre-aligner 27 as shown in the following Expression 33 and Expression 34 from the above Expression 25 and Expression 28. Can be associated with a coordinate system.
[0166]
P_S= RP_R+ O_W= RR_TP_W+ O_W        .... Formula 33
O_S= A^-1P_A+ O_A-(RR_TP_W+ O_W・ ・ ・ ・ Formula 34
Thus, by associating the camera coordinate system with the wafer coordinate system, an arbitrary point P on the semiconductor wafer 101 in the wafer coordinate system can be imaged by the CCD camera 4.
[0167]
[Die pitch movement]
Further, in this inspection apparatus, in the imaging of the surface of the semiconductor wafer 101 by the CCD camera 4, the actual movement of the inspection stage is also associated with the movement on the wafer coordinate system or the die coordinate system. Can do. That is, a movement vector of a predetermined direction and distance on the semiconductor wafer 101 is expressed as D in the wafer coordinate system._WAnd define
P_D= R_T(P_W+ D_W・ ・ ・ ・ Formula 35
As in the above case,
P_S= RP_D+ O_W= RR_T(P_W+ D_W) + O_W    ... Formula 36
By this, it is possible to associate the wafer coordinate system with the stage coordinate system including the operation of the transfer mechanism and the movement vector of the predetermined direction and distance on the semiconductor wafer 101,
O_S= A^-1P_A+ O_A-(RR_T(P_W+ D_W) + O_W) ・ ・ Formula 37
By associating the camera coordinate system with the wafer coordinate system, a point (P) in a predetermined direction and distance from the point P in the wafer coordinate system_W+ D_W) Can be imaged by the CCD camera 4.
[0168]
Where D_WIs a vector corresponding to the interval (die pitch) of dies on the semiconductor wafer 101, so-called “die pitch movement” can be easily performed. For example, as shown in FIG. 15, when the orientation flat standard direction is “(DOWN)” and “TIS” is measured, the orientation flat direction is “(RIGHT)”. If (Dx, Dy), then this is the matrix R_TWhen (RIGHT) is applied, the following Expression 37 is obtained.
[0169]
[Expression 22]

[0170]
This is the die pitch in the stage coordinate system. Here, in the input device 53, as shown in FIG. 16, when there are moving keys indicating up, down, left, and right, normally, the up, down, left, and right of these keys are up and down when the inspection stage 2 is viewed from above. The inspection stage 2 is driven corresponding to the left and right (that is, the back side, the near side, the left side, and the right side). In this inspection apparatus, the movement of the inspection stage 2 is a matrix R._TIn addition, the fine alignment is also performed.
[0171]
For example, in this case, when the input value (x, y) = (0, 1), the movement of the inspection stage 2 is (0, −Dx), and the input value (x, y) = (1, 0), the movement of the inspection stage 2 is (Dy, 0), and when the input value (x, y) = (0, −1), the movement of the inspection stage 2 is (0, Dx). Thus, for the input value (x, y) = (− 1, 0), the movement of the inspection stage 2 is (−Dy, 0).
[0172]
In this case, the movement of the die coordinate on the inspection stage 2 is expressed as a matrix R._T(RIGHT)^-1For example, in the input value (x, y) = (0, 1), as shown in the following equation 38, (1, 0) is obtained.
[0173]
[Expression 23]

[0174]
As for movement in other directions, as shown in FIG.
When the input value (x, y) = (1, 0), the movement amount of the die coordinate is (0, −1), and when the input value (x, y) = (0, −1), the die coordinate. The amount of movement is (−1, 0), and for the input value (x, y) = (− 1, 0), the amount of movement of the die coordinates is (0, 1).
[0175]
[Effects of this inspection device]
As described above, in the inspection apparatus according to the present invention, when the inspection is performed using the image obtained by the imaging by the CCD camera 4, the semiconductor wafer 101 is uniform with respect to the direction in which the semiconductor wafer 101 is carried into the inspection apparatus. Coordinate conversion processing is possible. Therefore, even during the “TIS” measurement, the conversion processing by fine alignment and the coordinate conversion processing for the CCD camera 4 and the inspection stage 2 can be performed in the same manner as in the case of normal inspection. In addition, it is not necessary to perform individual processing according to the type of the direction of loading, and it does not depend on the number of types.
[0176]
For this reason, as compared with the case where individual coordinate conversion processing is performed for the rotation of the semiconductor wafer 101 as seen in the conventional inspection apparatus, there is no influence due to variations or individual differences in the conversion processing circuit. Can do.
[0177]
Furthermore, in addition to the conversion from the wafer coordinate system to the mechanical coordinate system or the stage coordinate system, even if any conversion processing needs to be performed, there is no need to perform additional conversion processing for each rotation direction of the semiconductor wafer 101. Good expandability and reliability can be ensured.
[0178]
【The invention's effect】
As described above, in the inspection apparatus and the inspection method according to the present invention, when performing an inspection using an image obtained by imaging by the imaging unit, the inspection object is uniformly provided in the direction in which the inspection object is carried into the inspection apparatus. Coordinate conversion processing becomes possible. Therefore, even during the “TIS” measurement, the conversion process by fine alignment and the coordinate conversion process for the imaging means and the object support mechanism can be performed in the same manner as in the case of a normal inspection. In addition, it is not necessary to perform individual processing according to the type of the direction of loading, and it does not depend on the number of types.
[0179]
Therefore, compared to the case where individual coordinate conversion processing is performed for the rotation of the inspection object, as seen in conventional inspection apparatuses, there is no influence due to variations or individual differences in the conversion processing circuit. Can do.
[0180]
Further, in addition to the conversion from the inspection object coordinate system to the mechanical coordinate system or the support mechanism coordinate system, additional conversion processing is performed for each rotation direction of the inspection object even when it is necessary to perform some conversion processing. There is no need, and good expandability and reliability can be ensured.
[0181]
In other words, the present invention can be applied to a plurality of coordinate systems on the inspection apparatus even when the inspection object is carried in a plurality of different directions in order to measure an error inherent in the inspection apparatus. Therefore, it is possible to provide an inspection apparatus and an inspection method which are easy to perform the coordinate conversion process and can accurately measure errors.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing the configuration of an inspection apparatus according to the present invention.
FIG. 2 is a perspective view showing a configuration of the inspection apparatus.
FIG. 3 is a longitudinal sectional view showing a configuration of the inspection apparatus.
FIG. 4 is a plan view showing a configuration of the inspection apparatus.
FIG. 5 is a block diagram showing a configuration of the inspection apparatus.
FIG. 6 is a side view showing a configuration of an optical unit of the inspection apparatus.
FIG. 7 is a plan view showing the relationship of the coordinate system in the inspection apparatus.
FIG. 8 is a plan view showing an example of alignment marks observed in the inspection apparatus.
FIG. 9 is a plan view showing changes in coordinates when the observation stage is rotated in the inspection apparatus.
FIG. 10 is a plan view showing a change in coordinates when the observation stage is rotated and further translated in the inspection apparatus.
FIG. 11 is a plan view showing changes in coordinates when the field of view of the CCD camera is changed by exchanging the imaging lens in the inspection apparatus.
FIG. 12 is a plan view showing changes in coordinates when the field of view of the CCD camera is changed by exchanging the imaging lens and the observation stage is moved in parallel in the inspection apparatus.
FIG. 13 is a plan view showing a state when the orientation flat direction of the semiconductor wafer is a standard direction in the inspection apparatus.
FIG. 14 is a plan view showing a state in which the orientation flat direction of the semiconductor wafer is set to the right side for the measurement of “TIS” in the inspection apparatus.
FIG. 15 is a plan view showing coordinates on a semiconductor wafer in which the orientation flat direction is the right side direction for the measurement of “TIS” in the inspection apparatus.
FIG. 16 is a plan view showing the correspondence between the movement key in the input device and the movement direction of the inspection stage 2;
17 is a plan view showing the correspondence between the movement key in the input device and the movement direction of the die coordinate on the semiconductor wafer on the inspection stage 2. FIG.
[Explanation of symbols]
1 base, 2 inspection stage, 3 transport mechanism, 4 CCD camera, 5 control circuit, 6 transport mechanism, 7 cassette, 8 microscope, 9 camera moving mechanism, 101
Semiconductor wafer

Claims (4)

The base,
Provided on the base, to support the semiconductor wafer, and the inspection object support mechanism for moving operating the semiconductor wafer in a direction perpendicular to the predetermined movement plane and said plane of movement,
The semiconductor wafer, and a transport mechanism for the semiconductor wafer by the inspection object support mechanism rotationally operated as an axis line perpendicular to the movement plane which is movement operation, is supported to said inspection object supporting mechanism,
An imaging means for visible light, which is provided on the base so as to be movable with respect to the base and picks up an image of the semiconductor wafer supported by the inspection object support mechanism with visible light from outside the movement plane; An optical unit having both an imaging means for ultraviolet light for imaging the semiconductor wafer with ultraviolet light;
An imaging means moving mechanism for moving the imaging means for visible light and ultraviolet light;
A control means for controlling operations of the inspection object support mechanism, the transport mechanism, and the imaging means moving mechanism,
The control means includes a mechanical coordinate system with the base as a reference, a stage coordinate system with a reference point on a moving part of the inspection object support mechanism as an origin, and an imaging means for visible light and ultraviolet light. A camera coordinate system based on the imaging range in and an inspection object coordinate system with the center of the semiconductor wafer as the origin,
The origin of the mechanical coordinate system is O _M (0, 0), the coordinate of the reference point on the moving part of the inspection object support mechanism in the mechanical coordinate system is O _S, and the visible light in the mechanical coordinate system is and the coordinates of the reference point of the imaging range of the imaging means for the ultraviolet light and O _a, the center coordinates of the semiconductor wafer in the stage coordinate system as O _W,
For any point P on the semiconductor wafer, the coordinates in the mechanical coordinate system and P _M, the coordinates in the camera coordinate system and P _A, the coordinates in the stage coordinate system and P _S, the inspection object coordinate system Let P _W be the coordinates at
The primary transformation matrix of the amount of movement of the point P from the mechanical coordinate system to the camera coordinate system is A, and the primary transformation matrix of the amount of movement of the point P from the stage coordinate system to the inspection object coordinate system is R. Let _{RT be a} primary transformation matrix corresponding to the rotation of the semiconductor wafer by the transport mechanism.
P _M = A ⁻¹ P _A + O _A
By associating the camera coordinate system with the mechanical coordinate system,
P _S = A ⁻¹ P _A + O _A −O _S
By associating the camera coordinate system with the stage coordinate system,
P _S = RP _W + O _W
To associate the inspection object coordinate system with the stage coordinate system,
P _S = RR _T P _W + O _W
By associating the inspection object coordinate system with the stage coordinate system, including the operation of the transport mechanism,
^{_{O S = A -1 P A +}} O A - (RR T P W + O W)
By associating the camera coordinate system with the inspection object coordinate system, the imaging means for visible light and ultraviolet light can be placed at any point on the semiconductor wafer in the inspection object coordinate system. An arbitrary point P on the semiconductor wafer in the inspection object coordinate system is picked up by the visible light and ultraviolet light imaging means, and the visible light is used with low resolution. inspection and of the semiconductor wafer, have rows both the inspection of the semiconductor wafer with a high resolution using an ultraviolet light,
The imaging means for visible light and the ultraviolet light each have a CCD camera that captures an image of a semiconductor wafer magnified by an objective lens, and an autofocus control unit that performs focal position alignment of the objective lens. The autofocus control unit detects whether or not the distance between the objective lens and the semiconductor wafer matches the focal length of the objective lens, and moves the object support mechanism perpendicular to the predetermined moving plane. Inspection apparatus that performs focal position alignment of the objective lens by moving in a specific direction . A movement vector of a predetermined direction and distance on the inspection object is defined as DW in the inspection object coordinate system,
^{_{O S = A -1 P A +}} O A - (RR T (P W + D W) + O W)
The inspection apparatus according to claim 1, wherein a point located in a predetermined direction and distance from the point P in the inspection object coordinate system is imaged by the imaging means for visible light and ultraviolet light. It supports the semiconductor wafer is provided on the base with respect to the inspection object support mechanism for moving operating the semiconductor wafer in a direction perpendicular to the predetermined movement plane and said plane of movement, using the transfer mechanism, the semiconductor The wafer is supported by being rotated about a line perpendicular to the moving plane as an axis, and provided on the base so as to be movable with respect to the base, and for imaging the semiconductor wafer with visible light. Using the visible light imaging means and the ultraviolet light imaging means of the optical unit having both the imaging means and the ultraviolet light imaging means for imaging the semiconductor wafer with ultraviolet light. In imaging the semiconductor wafer from the outside,
The mechanical coordinate system based on the base, the stage coordinate system based on the reference point on the moving part of the inspection object support mechanism, and the imaging range in the visible light and ultraviolet light imaging means And the inspection object coordinate system with the center of the semiconductor wafer as the origin,
The origin of the mechanical coordinate system is O _M (0, 0), the coordinate of the reference point on the moving part of the inspection object support mechanism in the mechanical coordinate system is O _S, and the visible light in the mechanical coordinate system is and the coordinates of the reference point of the imaging range of the imaging means for the ultraviolet light and O _a, the center coordinates of the semiconductor wafer in the stage coordinate system as O _W,
For any point P on the semiconductor wafer, the coordinates in the mechanical coordinate system and P _M, the coordinates in the camera coordinate system and P _A, the coordinates in the stage coordinate system and P _S, the inspection object coordinate system Let P _W be the coordinates at
The primary transformation matrix of the amount of movement of the point P from the mechanical coordinate system to the camera coordinate system is A, and the primary transformation matrix of the amount of movement of the point P from the stage coordinate system to the inspection object coordinate system is R. Let _{RT be a} primary transformation matrix corresponding to the rotation of the semiconductor wafer by the transport mechanism.
P _M = A ⁻¹ P _A + O _A
By associating the camera coordinate system with the mechanical coordinate system,
P _S = A ⁻¹ P _A + O _A −O _S
By associating the camera coordinate system with the stage coordinate system,
P _S = RP _W + O _W
To associate the inspection object coordinate system with the stage coordinate system,
P _S = RR _T P _W + O _W
By associating the inspection object coordinate system with the stage coordinate system, including the operation of the transport mechanism,
^{_{O S = A -1 P A +}} O A - (RR T P W + O W)
By associating the camera coordinate system with the inspection object coordinate system, the imaging means for visible light and ultraviolet light can be placed at any point on the semiconductor wafer in the inspection object coordinate system. An arbitrary point P on the semiconductor wafer in the inspection object coordinate system is picked up by the visible light and ultraviolet light imaging means, and the visible light is used with low resolution. inspection and of the semiconductor wafer, have rows both the inspection of the semiconductor wafer with a high resolution using an ultraviolet light,
The imaging means for visible light and the ultraviolet light each have a CCD camera that captures an image of a semiconductor wafer magnified by an objective lens, and an autofocus control unit that performs focal position alignment of the objective lens. The autofocus control unit detects whether or not the distance between the objective lens and the semiconductor wafer matches the focal length of the objective lens, and moves the object support mechanism perpendicular to the predetermined moving plane. Inspection method for performing focal position alignment of the objective lens by moving in a specific direction . A movement vector of a predetermined direction and distance on the inspection object is defined as D _W in the inspection object coordinate system,
^{_{O S = A -1 P A +}} O A - (RR T (P W + D W) + O W)
4. The inspection method according to claim 3, wherein the imaging means for visible light and ultraviolet light is moved to a position for imaging a point in a predetermined direction and distance from the point P in the inspection object coordinate system.

Images