| 摘要 |
PURPOSE:To accurately align the position of grating on a wafer and generated interference fringe by reflecting or transmitting the light flux having passed two diffraction gratings on a reticle with the diffraction grating on the wafer. CONSTITUTION:The light fluxes 12, 13 in the same phase are vertically directed to the gratings 14, 15 on a reticle, an interference fringe F is formed by crossing the diffracted lights 16, 17 on a wafer W at a crossing angle 2theta and it is aligned to the grating G provided on the wafer. Rotations PHI, PSI of grating G and fringe F in the afer surface and incident surface are adjusted by reducing a wafer surface and incident surface are adjusted by reducing a number of moire-image interference fringes through fine adjustment of wafer. The diffracted lights 16, 17 sent from the grating G having almost the same pitch as the pitch A of interference fringe determined by the wavelength of light and incident angle theta are collected and interfered again. Light intensity to be observed depends on the angle of detector D and has a peak value. Therefore, a detector is fixed at the peak intensity position and relative position (x) of fringe F and grating G is changed. Since light intensity periodically changes for each pitch of grating G, relative position can be obtained from measurement of light intensity and highly accurate position aligning can be realized. |
