Stochastic Simulation of Pattern Formation for Negative-Type Chemically Amplified Resists in Extreme Ultraviolet Lithography

A stochastic simulation of the pattern formation process for negative-type chemically amplified resists in extreme ultraviolet (EUV) lithography has been performed. The initial structures of the resist polymers are formed by randomly bonding monomers. The deposited energy distribution in the resist by EUV light exposure is calculated by Monte Carlo simulation of the photoelectron scattering. The activation of acid generators is introduced according to the deposited energy distribution. Acid diffusion and the polymer crosslinking reactions during the post-exposure bake (PEB) are then simulated. Development of the resist is modeled by removing the polymers with a polymerization degree below the threshold value from the resist. The effects of EUV light exposure and PEB conditions on the pattern shapes are investigated by the simulation.