Dissociative photoionization of EUV lithography photoresist models

TL;DR

This study investigates how EUV photons cause dissociation and ionization in a resist monomer, providing insights into resist behavior and guiding the development of improved lithography materials.

Contribution

It offers detailed experimental data on EUV-induced dissociation and ionization mechanisms in a key resist monomer, aiding resist design and understanding of photoinduced processes.

Findings

EUV photons predominantly cause dissociation of the resist monomer.

Ionization can directly deprotect ester groups, affecting solubility.

Results help interpret ultrafast experiments and improve resist materials.

Abstract

The dissociative photoionization of \textit{tert}-butyl methyl methacrylate, a monomer unit found in many ESCAP resists, was investigated in a gas phase photoelectron photoion coincidence experiment employing extreme ultraviolet (EUV) synchrotron radiation at 13.5 nm. It was found that the interaction of EUV photons with the molecules leads almost exclusively to dissociation. However, the ionization can also directly deprotect the ester function, thus inducing the solubility switch wanted in a resist film. These results serve as a building block to reconstruct the full picture of the mechanism in widely used chemically amplified resist thin films, provide a knob to tailor more performant resist materials, and will aid interpreting advanced ultrafast time-resolved experiments.