| 摘要 |
PURPOSE:To obtain the exact positional relation between a reticle and a wafer quickly, by a method wherein the position of an image for pattern detection projected on a sample surface is changed according to a function, and the amplitude of a component having an angular frequency is obtained by the relation to the output of a photodetector. CONSTITUTION:In the case of performing mark detection, an excimer laser oscillates pulses one by one in accordance with external trigger. A photo scanner 160 is provided with an equipment to read a deflected distance of laser light. By multiplying the read distance by the magnification of a projection lens 120, the position of a pattern 180 for mark detection on a wafer 130 can be obtained. A photo scanner 160 is so driven that the image position of the pattern 180 for mark detection changes according to (dh+h(t)) where dh is a bias. The position where the excimer laser light is projected, is generated from a light projection position generating circuit. When this position and the projection position by the photo scanner 160 coincide with each other, the trigger signal is generated, and the excimer laser oscillates a pulse light.
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