Lithography performance improvement of MOR by underlayers

Abstract

Metal oxide resists (MORs) have become one of the most attractive photoresist platforms that allow for high resolution and etch bias of small features while having a robust lithography performance. In this work, we present our study about improving line fidelity and reducing the dose of MOR for line space EUV lithography by applying spin-on underlayers (ULs). It is known that MOR patterning is induced by the activation during exposure and condensation of the active sites. Herein, we discuss the influence of ULs on MOR performance. A series of ULs with various chemistry, thickness, or process conditions were screened with MOR using NXE3400 EUV exposure system to print 14-nm HP line-space features. The results show that the nanobridges and scum can be alleviated, while the remaining resist thickness after development can be improved by up to 20% along with 5 -10% dose reductions. A comprehensive assessment of the ULs encompassing various chemistries examines coating quality, uniformity, and surface energy. The discussion delves into the correlation between the surface properties including morphology, interaction, etc., and their respective impacts on lithography performance. Lastly, some spin-on ULs produce up to 75% reduction of metal diffusion from the MOR into the underlying layers.