| 摘要 |
PURPOSE:To reduce the unnecessary exposure to a laser beam as much as possible without lowering the accuracy in positioning and the percentage of success by a method wherein the quantity of light which is made to irradiate a wafer is reduced excepting the time when the relative position of the position detecting mark, provided on the wafer and a mask or a reticle, is measured by a light-deflecting means. CONSTITUTION:A means, with which sufficient quantity of laser beam is made to irradiate only in the minimum period of time required and the quantity of the laser beam is reduced during the period other than the above-mentioned irradiation, is provided. A light deflecting element 8 is provided as the above-mentioned means between a polygonal mirror 7 and a laser beam source 10 on consideration of the indispensability of a high-speed response. The light deflecting means 8 utilizes the acoustic and optical effects that light is diffracted by compression waves of refractive index by generating ultrasonic waves in a transparent medium, and is subjected to the refraction, reflection and dispersion of light. Tellurium dioxide is used, for example, as the acoustic and optical material, and a piezoelectric element is utilized for generation of supersonic waves. When high frequency power is applied to the piezoelectric element, the laser beam is refracted. When the input light emitted from the laser beam source 10 is outputted to a light path 16 using the light-deflecting element 8, the laser beam is made to irradiate, and the laser beam is lowered when power is outputted to a light path 15.
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