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

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.