| 摘要 |
PURPOSE: To obtain sufficient resolution of a detection result also to minute dislocation of height or an inclination of a plane for detection. CONSTITUTION: After being converted into a spherical wave by an irradiation optical system 4, a light pencil from a light source 3 is divided into the first and second light pencils LB1 and LB2 by a first beam splitter 5 so as to make two light pencils LB1 , LB2 to travel on the almost same optical paths besides in the opposite directions. The first and second light pencils LB1 and LB2 to be reflected from a wafer face 2a are synthesized together by a beam splitter 5 so as to divide its coherent light into the first and second coherent lights IB1 and IB2 by a second beam splitter 8. The first coherent light IB1 is received by a first photoelectric sensor 9 and the second coherent light IB2 is converted into a plane wave by a collimeter optical system 10 and received by a second photoelectric sensor 11. A displacement of a height and an angle of tilt of a wafer surface 2a is calculated from a pitch of the fringes detected by two photoelectric sensors 9, 11. |
