Abstract

Double telecentric configuration of an optical projection lens with alignment through lens wafer-to-reticle and uniform illumination pinciple of optical system for micro­lithography are discribed in the paper. To meet requirement of optical transfer function (OTF) for i-line lithography, the relation between photolithographic resolution (R) and numerical aperture (NA) is discussed. As an example, we have designed a new double telecentric projection lens with NA=0.42, magnification M=-l/5, image field size 15mmx15mm (21.2mm diametre) and conjugate distance 602mm.

Optical design program ZEMAX-XE is used to calculate image qualities of the i-line lens. The calculating results indicate wavefront aberrations < λ/4 and MTF >0.55 across the entire field when spatial frequency is 715 c/mn and wavelength is 365+/-3mn. This means the photolithographic resolution of 0.7um could be realized. The illumination uniformizer called the integrator consists of an array of 81 small square lens elements. The illumination non-uniformity of+/-2% could be realized by using our simulation program OPTENG to calculate light intensity distribution on tire illuminated image plane.

© 1994 Optical Society of America