Quantitative evaluation of shape of image on photoresist of squareapertures

Simulation of images of two-dimensional structures in optical lithography is considered to have become quite important with the patterning of near-micrometer geometries in complex structures encountered in VLSI. Here, the results are presented of theoretical computations performed to calculate the aerial image of square apertures in a projection system using a partially coherent light source. The resist has been modeled by its sensitivity curve in order to compute the image profile on the resist after development. A figure of merit (FOM) has been proposed that quantifies the shape of the aerial as well as the resist image. Such an FOM has been proposed that can be used very effectively to optimize a lithographic process