EUV metal oxide resists: impact of the environment composition on CD during post-exposure delay

Abstract

Airborne molecular contaminants (AMCs) in the cleanroom have been known to impact the performance of photoresist materials. Here, we investigate the effect of the environment composition during post-exposure delay (PED) on metal oxide resists (MOR). We applied specific environments during a fixed PED time and measured the impact of each condition on the printed L/S patterns by measuring the change in the final critical dimension (CD) in each case compared to a reference control. We performed chemical analysis to elucidate which chemical changes take place in the resist under the conditions that induced the largest CD changes. Our results suggest that the magnitude of the CD change after a fixed PED time depends on two main variables: the concentration of contaminants and the humidity of the environment. The chemical analysis after a PED in the presence of contaminants and humidity revealed that extra ligand cleavage takes place under these conditions compared to the reference non-delayed conditions. The results show that deviations from the target CD in MOR can be prevented by having control over humidity, contaminant levels, and PED time during processing. Furthermore, new optimized formulations designed to hinder extra chemical reactions during PED show a stable CD even when the PED was applied in environments with humidity and contaminants.