| 摘要 |
PURPOSE:To perform an alignment in a highly precise manner by a method wherein a lattice is arranged on the position of split rays of a wafer in parallel to the interference fringe obtained by projecting a coherent light from two directions through the slit of a mask, thereby enabling to recognize the relative position of the interference fringe and a lattice from a reflected light. CONSTITUTION:A laser beam 10 is divided BS into a reflection light 11 and a transmis sion light, they are reflected by mirrors M1 and M2 and made incidence on a wafer W at the equiangle theta, and an interference fringe is formed by superposing them on the wafer W through the intermediaries of the slits S1 and S1' of a mask 20. A lattice G is provided in parallel to the interference fringe on the position which proportionates to the split rays of the wafer, and the interference fringe is placed on the lattice. The reflection light 13 of the interference fringe and the lattice G is detected D1. The pitch of the interference fringe is Pf=l/2sintheta when wavelength is lambda, and the information of light intensity showing the relation of relative position of the interfer ence fringe and the lattice is obtained from the lattice G of the pitch PG=nPf. When the wafer W is shifted to the pitch direction of the interference fringe, the light intensi ty I changes periodically for every pitch Pf, thereby enabling to accurately align the interference fringe and the lattice in several hundred Angstrom or thereabout and to perform an exposing process. |
