Mechanisms of photodecomposition of metal-containing EUV photoresists: isotopic labelling studies

We have investigated the mechanism of photodecomposition of antimony carboxylate complexes of the type Ph3Sb(O2CR′)2 by means of EUV outgassing in combination with isotopic labelling. A series of photoresists were examined to determine the mechanistic pathways by which volatile photoproducts are generated during EUV exposure. A primary volatile photoproduct from triphenylantimony complexes is benzene. However, the source of hydrogen needed to convert the phenyl groups to benzene (Ph-H) is not obvious. We concluded that the primary source of hydrogen to create benzene is external to the film. Additionally, we have prepared isotopically-labelled versions of Ph3Sb(O2CCH(CH3)2)2 in which the hydrogens in the isobutyrate ligand were replaced with 0, 1, 6 and 7 deuteriums, to provide information about the relative reactivity of these protons during EUV exposure as analyzed by mass spectrometry. High reaction selectivity was identified within the carboxylate dictated by hydrogen location relative to the carbonyl for both benzene and phenol generation. Lastly, the results of these studies were used to propose a series of reaction pathways to generate the aforementioned reaction byproducts.