| 摘要 |
PROBLEM TO BE SOLVED: To eliminate influence of disturbance such as micro vibration so as to measure surface configuration with high accuracy by combining converging lenses so as to make laser beams incident with a small beam diameter narrowed in a beam interval. SOLUTION: Laser beams are converged by converging lenses LE1, LE2, a mirror 25 and a converging lens LE3 so as to be narrowed in beam interval. A beam spot 29 is made incident on the upper part of the stepped pattern on the face of a wafer 14, and a beam spot 30 is made incident on the lower part of the stepped pattern on the face of the wafer 19. The laser beam L3' is reflected by the upper part of the stepped pattern on the face of the wafer 19, and the laser beam L4' is reflected by the lower part of the stepped pattern on the face of the wafer 19. Accordingly, when gap between the upper part and lower part of the stepped pattern on the face of the wafer 19, that is, step difference, is made (l), optical path length difference of (2l) is generated to reflected light from the upper part of the pattern and reflected light from the lower part of the pattern. Step difference on the face of the wafer 19, that is, surface configuration, can therefore be measured by a specific expression in the same way as a conventional method. |
