Process dependence of the thermal conductivity of image reversal photoresist layers

Abstract

Thermal transport in polymer layers is an important consideration in various lithography techniques, including immersion lithography and thermolithography. The in-plane thermal conductivity of commercially available photoresist AZ 5214E is determined at each stage of lithography processes using ultrathin (<100nm) freestanding membrane devices. The authors find that UV exposure does not lead to any appreciable change in thermal conductivity whereas cross-linking induced by postexposure bake results in a slight increase (∼5%). The thermal boundary resistance across interfaces between the resist layers and metal films/substrates is also found to be significant. The experimental techniques and data presented here will facilitate a systematic evaluation of thermal phenomena during lithography processes.