Effect of lens aberration on resist pattern profiles in edge-line phase-shift method

In edge-line phase-shift lithography, asymmetrical resist patterns formed by both sides of shifter edges have been observed in the case of a narrow shifter. The effect of phase error, shifter width and shifter edge angle on resist pattern profiles has been investigated by simulations and experiments. It has been confirmed that the asymmetry of resist patterns is mainly due to the coma aberration of the stepper projection lens and is enhanced as the shifter width becomes narrower. The effect of decreasing the shifter edge angle has proved to be equivalent to the effect of narrowing the effective shifter width.