Deuterium and fluorine radical reaction kinetics on photoresist

Abstract

The etching of two photoresists (PR) was investigated using beams of Ar+ ions and neutral fluorine and deuterium atoms. Large increases in the PR etch yields were observed as the flux ratio of the fluorine atom to the Ar+ ion beam was increased. However, there was no observed effect of deuterium on the PR etch yield despite the detectable formation of DF during the etching process. To explain this observation, the following abstraction and recombination probabilities from the PR surface were measured using modulated beam mass spectrometry: F atoms abstracting adsorbed D atoms (γFD=0.19), D atoms abstracting adsorbed F atoms (γDF<0.05), and D atoms recombining with adsorbed D atoms (γDD=0.06). These measurements were insufficient by themselves to make any conclusive statements about the observed independence of the etch yield on D atom flux, so a phenomenological model of the PR etching process was developed to explain the observed phenomena. When these measured quantities were used as parameters in this model, it was possible to predict the observed lack of effect of D atoms on the PR etch yield. During the course of these experiments, the etching probability of a D atom was also measured (1.5×10−4) and found to be in good agreement with previously published values.