A Novel Optical Lithography Technique Using the Phase-Shifter Fringe

Abstract

A new optical lithography technique called outline pattern transfer imaging (OPTIMA) is described. OPTIMA utilizes an optical phase change at a clear phase-shifter pattern edge. Very narrow closed patterns can be delineated along the fringe of the phase-shifter pattern by this method. The resolution limitation of OPTIMA is presented using a newly developed high-resolution i-line negative resist. The resist is transparent (90% at 0.5 µm thickness) and has a high γ value (4.5). Results show that 0.13 µm-wide groove patterns can be delineated with an i-line stepper having 0.42 numerical aperture. Practical focus latitude and exposure latitude are obtained for 0.2 µm patterns. In OPTIMA, linewidth control is also possible by adding notch patterns at the shifter edge.