| 摘要 |
PURPOSE:To adjust the focus to the surface of a wafer simply and automatically by projecting transmitted beams from mutually orthogonal slits at a distance very smaller than the focal distance of a microscope to the surface of the wafer and detecting reflected beams from the surface. CONSTITUTION:A wafer to be observed 10 is placed on a sample base 11. Beams from a light source lamp 2 transmit a slit a3 and a slit b4, and are projected onto the wafer 10 through a half mirror 5 and an objective 1. Reflected beams of beams projected to the wafer 10 are received by a CCD-A8 receiving transmitted beams from the slit a3 and a CCD-B9 receiving transmitted beams from the slit b4 through the objective 1, the half mirror 5, a relay lens 6 and a half mirror 7. When the objective is operated at the intermediate position of positions where outputs A, B from the two CCDs are each maximized, the focus can be adjusted onto the surface of the wafer. |
