Investigation of phase shift mask distortion effect

Distortion effects in alternating phase shift masks on wafer level imaging have been investigated using a combined simulation of the photomask patterning process and projection optical lithography. Unlike the previous simulation of the optical proximity effect, which were based on ideal mask designs, the simulation presented in this paper is based on distorted mask features. The mask feature distortion comes from simulation of laser scanning lithography. Proximity effects in laser direct writing has been taken into account for the generation of mask features. The simulations have demonstrated that phase shift masks also suffer from the optical proximity effect. The effect is worsened if mask distortion is taken into account. Compared with no phase shifting masks, phase shifting in mask features can slightly offset the proximity effect. (C) 2002 Published by Elsevier Science B.V.