A NOVEL OPTICAL LITHOGRAPHY TECHNIQUE USING THE PHASE-SHIFTER FRINGE

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-mu-m thickness) and has a high gamma-value (4.5). Results show that 0.13-mu-m-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-mu-m patterns. In OPTIMA, linewidth control is also possible by adding notch patterns at the shifter edge.