| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect elements of diffracted light in two measuring directions by one detetcor by forming a plurality of diffracted pictures which hardly overlap substantially with each other on the surface of front focal point of an objective lens and at its conjugate position. SOLUTION: Two linear beams are formed so that they may form a specified angle on the surface of front focal point of an objective lens 9 and hardly overlap with each other substantially. Then an alignment beam formed of two linear beams crossing on the light axis can be formed on an object to be inspected like a wafer 10 which is arranged on the surface of the rear focal point of the lens 9. In this case, a diffracted light generating from an alignment mark formed on the wafer 10 by the alignment beam forms a plurality of diffracted pictures which hardly overlap with each other substantially on the surface of front focal point of the lens 9 and at its conjugate position. Further a space filter 12 is arranged at a position to reform a diffracted picture, thereby detecting elements of diffracted light in two measuring directions by one detector 13 without reducing the detection efficiency substantially.</p> |
