FOCUSING DEVICE, FOCUSING METHOD AND PATTERN INSPECTION METHOD

PROBLEM TO BE SOLVED: To provide a focusing device that enables highly accurate focusing regardless of a pattern to be formed on an inspected substrate surface onto which a reticle image is projected.SOLUTION: A focusing device comprises: a reticle 182 that is arranged on a near side in an optical axis direction with respect to a conjugate position of a TDI sensor 105, and has an end part parallel with a time integration direction of the TDI sensor 105; a reticle 184 that is arranged on a rear side in the optical axis direction so that patterns are mutually inverted; a gain/offset adjustment circuit 140 that uses a gradation value of a pattern image of a substrate illuminated with reflection illumination light not passing through the reticles 182 and 184 to uniformize the gradation value thereof; a movement-amount computation unit that computes an amount of movement, using a primary differential value of a gradation value output by the TDI sensor 105 receiving the pattern image of the substrate which is created by reflection illumination light passing through the reticles 182 and 184 in a state where the uniformization is carried out; and a drive mechanism 186 that causes a relative distance between a mask substrate 101 and the conjugate position of the TDI sensor 105 to move.SELECTED DRAWING: Figure 1 【課題】レチクル像が投影される被検査基板面に形成されるパターンに関わらず、高精度に合焦可能な合焦装置を提供する。【解決手段】合焦装置は、ＴＤＩセンサ１０５の共役位置に対して光軸方向手前側に配置され、ＴＤＩセンサ１０５の時間積分方向に平行な端部を有するレチクル１８２と、光軸方向後側にパターンが互いに逆向きになるように配置されたレチクル１８４と、レチクル１８２、１８４を通過せずに照明された基板のパターン像の階調値を用いて、階調値の均一化を行うゲイン・オフセット調整回路１４０と、均一化が行われた状態で、レチクル１８２、１８４を通過した反射照明光によって生成された基板のパターン像を受光したＴＤＩセンサ１０５により出力された階調値の一次微分値を用いて、移動量を演算する移動量演算部と、マスク基板１０１とＴＤＩセンサ１０５の共役位置との相対距離を移動させる駆動機構１８６とを備える。【選択図】図１