A Comparison of the Spatial Statistics of Random and Defined-Sequence Photoresist Films

TL;DR

This study compares the internal structures and imaging characteristics of defined sequence versus random copolymer photoresist films, revealing that while their spatial distributions are similar, defined sequences can produce distinctive developable images under certain conditions, offering potential for improved nanoscale control.

Contribution

The paper introduces a modeling approach to compare defined sequence and random copolymer photoresist films, highlighting their structural similarities and unique imaging behaviors, which could inform future improvements in lithography.

Findings

Spatial distribution of chemical moieties is similar in both polymer types.

Defined sequence polymers can produce distinctive developable images.

No automatic improvement in imaging from using defined sequence polymers.

Abstract

The resolution-line edge roughness-sensitivity tradeoff has motivated exploration of potential improvements using defined sequence polymers and polymer-bound photoacid generators and quenchers. In this study we characterize the internal structures of positive tone photoresist polymer films formed from defined sequence polymers and compare them to random copolymers of the same composition. We model their imaging to connect initial to developable film structures. We use a polymer packing algorithm to simulate films of diverse compositions and locations of photoacid generators and quenchers, using the composition of an ESCAP photoresist. We use a simple EUV exposure-deprotection algorithm to model developable image formation within them. In all cases, the spatial distribution of chemical moieties in the film for defined sequence polymers is nearly indistinguishable from random copolymers. We evaluate several exposure-deprotection scenarios, and find that a defined sequence copolymer has a distinctive developable image under certain circumstances. The use of defined sequence polymers within a photoresist layer does not automatically result in improved imaging, however they do have some characteristics different from random polymers of the same composition. Further study of these characteristics may provide a route to improved control over the nanoscale imaging process.