Simple analytic modeling of photoresist development profiles in evanescent-field optical lithography

In nanolithography using optical near-field sources, a precise control of the process parameters is of utmost importance. We present a simple analytic model, based on 1-dimensional development marching level set method, to predict photoresist profiles with a localized evanescent exposure that decays exponentially in a photoresist of finite contrast. Impacts of relevant lithographic parameters are explored by assessing photoresist topography such as depth, width, sidewall angle, and aspect ratio. The exposure dose and developing time are demonstrated to be crucial parameters to be controlled. Compared with the previously proposed method, our model is found to augment the accuracy of the prediction of near-field lithographic features.