| 摘要 |
PURPOSE:To detect a mark efficiently with high precision by irradiating the mark with a slit-shaped scanning beam which conforms to the inclination of the mark, and switching the scanning beam during a single scan so that it conforms to the inclination direction of the positioning mark. CONSTITUTION:A laser beam L projected from a light source 10 is directed by an optical deflector 11 to an optical path determined previously by a control circuit 29, shaped into a thin and slit beam by the 1st cylindrical lens 12, and then made incident to the oscillation origin B of a rotary polygon mirror 15 by a prism 14 to make a deflection scan. The beam is incident to an end surface 19a of a prism 18 to be deflected to right and further deflected by a half-mirror 19a at right angles to form images on a mask 1 and a wafer 2, obtaining slit light lparallel to alignment marks M1, W1, and M2. The laser beam L is projected on the 2nd cylindrical lens 13 by optical-path switching and converted to an inclination direction l' parallel to alignment marks M3, W2, and M4. |
