ALIGNER

摘要

PURPOSE:To obtain an aligner mounted with a highly accurate and highly stable positioning device by substantially passing two coherent light rays having different vibration frequencies through the same optical path in a precision alignment system which has relatively high detection accuracy for measuring the absolute position of a first or second object. CONSTITUTION:Two beat signals are respectively obtained from two precision alignment systems 3 and 5. A phase comparator 6 measures the phase difference between the two beat signals and calculates the relative positional deviation between a wafer 9 and reticle 1. A control system 7 positions the wafer 9 by moving a stage 8 so that the positional deviation can become zero or a prescribed value. Thus two kinds of light rays having frequencies f+F1 and f+F2 are made incident to a diffraction grating 10 at different angles theta1 and theta2 against the wafer 9. In addition, the light rays are also made incident to another diffraction grating 2 at different angles theta1' and theta2' against the reticle 1. Therefore, the reflected and diffracted light rays of the light rays can be made to pass through the same optical path.