Resolution enhancement by oblique illumination optical lithography using a pupil filter

A novel technique to enhance patterning resolution is investigated. A pupil filter with a transmittance distribution corresponding to the shape of the secondary light source is used in the projection lens in addition to annular oblique illumination. As an experimental result, superior conventional lithography and annular oblique resolution about 20% higher than that of the conventional method is obtained, and 0.28-/spl mu/m projection lens with and without the pupil filter. Periodical patterns are replicated using an i-line stepper with an NA of 0.52. Subjects for further study are also discussed.<>