Stochastic simulation of thin photoresist film dissolution: a dynamic and a quasi-static dissolution algorithm for the simulation of surface and line-edge roughness formation

Abstract

Stochastic simulation techniques gain increased importance in the field of microelectronic processes especially since the sub-100 nm device dimensions have been reached. In this work, stochastic Monte Carlo techniques are incorporated to simulate photoresist polymer chains in a lattice, while all the phenomena taking place during film dissolution are considered in terms of occurrence probabilities in order to describe the dynamics of dissolution. Chain removal is based on the critical ionization fraction criterion. The exponential decrease of dissolution rate with increasing polymerization length is proven and its relation to critical ionization is investigated both in two and three dimensions (2D/3D), resulting in an efficient method for the determination of the dissolution rate in terms of polymerization length and critical ionization fraction. While the dynamic dissolution algorithm is appropriate for obtaining information about dissolution rate and surface roughness evolution, the increased computational time in high values of critical ionization fraction and lattice sizes, especially in 3D, make it inappropriate for line-edge roughness studies. A quasi-static 2D/3D resist dissolution algorithm, which is free of the dissolution blocking problems and orders of magnitude faster than the dynamic one, based again on the critical ionization criterion, is constructed in order to reliably quantify line-edge roughness.