Patent ID: 6897944

Claim:
An illumination optical system for illuminating a mask that arranges a contact-hole pattern and an auxiliary pattern smaller than the contact-hole pattern using light from a light source, said illumination optical system comprising: an illumination-light generating mechanism for dividing the light and for forming a quadrupole light intensity distribution around an optical axis on a surface that has substantially a Fourier conversion relationship with the mask, so as to resolve the contact-hole pattern and restrain the auxiliary pattern from resolving, wherein at least one of a size of each pole in the quadrupole light intensity distribution and a distance between the optical axis and each pole in the quadrupole light intensity distribution are variable, and wherein the contact-hole pattern aligns with the auxiliary pattern on the mask in longitudinal and transverse directions, and each pole in the quadrupole light intensity distribution separates from the optical axis in the longitudinal and transverse directions.