| 摘要 |
PURPOSE:To accurately align the position of photo mask of fine pattern and wafer in the atmospheric condition by providing the lattice in such a pitch as integer times of fringe pitch in parallel to the interference fringe of coherent two light fluxes and measuring intensity by collecting the reflected or transmitting lights. CONSTITUTION:A laser light 10 in the wavelength l is divided into the reflected light 11 and the transmitting light 12, these are reflected by the mirrors M1, M2, and then these lights are directed to an incident angle of theta to the surface of a wafer W. Thereby, the interference fringes are generated in the pitch A=lambda/2X sintheta. When the lights 13, 15 diffracted by the grating G of the specified pitch formed on the wafer are collected and interfered through a lens L, light intensity information which indicates relation between the interference fringe and grating G can be detected. The light intensity shows a sharp peak when the pitch of grating is integer times of pitch A and it also depends on measuring angle. In case the measuring angle is fixed to the position showing the peak value and the relative position (x) among light fluxes 11, 12, interference fringe and grating G is changed, the light intensity changes periodically for each pitch of grating. Therefore, the relative position between interference fringe and grating G can be read by detecting such intensity and highly accurate position aligning can be realized. |
