Stability studies on a sensitive EUV photoresist based on zinc metal oxoclusters

Background: Hybrid inorganic-organic materials have emerged as promising candidates for EUV resists.
However, knowledge on their stability when deposited as thin films is essential for their performance in EUV
lithography.
Aim: We investigate whether the molecular structure of Zn-based metal oxoclusters is preserved upon thin film
deposition and study aging processes of the thin film under different atmospheres, since these chemical
changes affect the solubility properties of the material.
Approach: A hybrid cluster that combines the high EUV photon absorption cross-sections of zinc and fluorine
with the reactivity of methacrylate organic ligands was synthesized. The structural modifications upon thin film
formation and after aging in air, nitrogen, and vacuum were studied using a combination of spectroscopic techniques.
Preliminary studies on the lithographic performance of this material were performed by EUV interference
lithography.
Results: The Zn-based compound undergoes structural rearrangements upon thin film deposition as compared
to the bulk material. The thin films degrade in air over 24 h, yet they are found to be stable for the duration and
conditions of the lithography process and show high sensitivity.
Conclusions: The easy dissociation of the ligands might facilitate hydrolysis and rearrangements after spincoating,
which could affect the reproducibility of EUV lithography.