Abstract

A deep UV projection system has been developed by modifying a commercial step-and-repeat exposure system to operate with a KrF excimer laser at a wavelength of 248 nm.¹ The projection lens consists only of fused silica elements, which imposes a narrowband requirement on the laser source of <0.005 nm. It is a 5× reduction lens with a field size of 14.5 mm and variable numerical aperture up to 0.38. The system is designed and built to achieve a practical resolution of 0.5 over the field of 14.5 mm with the depth of focus of the order of 1.5 µm. We demonstrate the results of extensive resolution studies as well as applications to real submicron devices. The results show the system capability for printing features <0.5 µm in size with reasonable depth of focus. Some of the advantages and limitations of laser-based lithography are discussed.

© 1986 Optical Society of America