# Reference-Free Quantitative Mass Spectrometry Enables Sequencing of Resist Copolymers and Reveals Sequence-Dependent Deprotection Sensitivity

## TL;DR

A new mass spectrometry method can sequence resist copolymers and shows that polymer sequence affects deprotection sensitivity, which could impact semiconductor lithography.

## Contribution

A reference-free pyrolysis-MS sequencing method is introduced for resist polymers, revealing sequence-dependent deprotection behavior.

## Key findings

- Pyrolysis mass spectrometry can quantify short-sequence frequencies in resist polymers.
- Sequence-dependent decomposition temperature profiles encode sequence information.
- Sequence influences deprotection sensitivity, potentially affecting lithography performance.

## Abstract

The influence of monomer sequence in resist polymers
on line-edge
roughness (LER) has long remained elusive in semiconductor lithography.
Although the arrangement of degradable and nondegradable monomers
should affect polymer solubility in developer solutions, the lack
of sequencing methods has prevented analysis of sequence–LER
correlations. Here, we present a sequencing approach for resist polymers
using pyrolysis mass spectrometry (pyrolysis-MS), which quantifies
short-sequence frequencies from pyrolyzed oligomer fragments. Methacrylate-based
resist polymers, however, undergo depolymerization and side chain
cleavage, generating fragments too small to retain sequence information.
Nevertheless, we found these instabilities themselves are sequence-dependent,
as shown by computational modeling, encoding sequence information
in decomposition temperature profiles. By exploiting both mass- and
temperature-domains, our strategy enables sequencing of resist copolymers
previously considered inaccessible. Moreover, sequence-dependent side
chain instabilities imply that resist responsiveness in deprotection
processes may also depend on sequence. The proposed sequencer offers
a path to unravel the long-standing sequence–LER relationship.