A profile-aware resist model with variable threshold

Abstract

The pursuit of ever smaller transistors has pushed technological innovations in the field of lithography. In order to continue following the path of Moore’s law, several solutions have been proposed: EUV, e-beam and double patterning lithography. As EUV and e-beam lithography are still not ready for mass production for 20 nm and 14 nm nodes, double patterning lithography play an important role for these nodes. In this work, we focus on a Self-Aligned Double-Patterning process (SADP) which consists of depositing a spacer material on each side of a mandrel exposed during a first lithography step, dividing the pitch into two, after being transferred into the substrate, and then cutting the unwanted patterns through a second lithography exposure. In the specific case where spacers are deposited directly on the flanks of the resist, it is crucial to control its profile as it could induce final CD errors or even spacer collapse. One possibility to prevent these defects from occurring is to predict the profile of the resist at the OPc verification stage. For that, we need an empirical resist model that is able to predict such behaviour. This work is a study of a profile-aware resist model that is calibrated using both atomic force microscopy (AFM) and scanning electron microscopy (SEM) data, both taken using a focus and exposure matrix (FEM).