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.半导体光刻领域中，光刻胶聚合物（resist polymers）的单体序列对线边粗糙度（line-edge roughness，简称LER）的影响长期以来始终未被明确阐释。尽管可降解与不可降解单体的排布理应会影响聚合物在显影液中的溶解度，但由于缺乏序列表征方法，学界始终无法开展序列与LER的相关性分析。本研究提出一种基于热解质谱（pyrolysis mass spectrometry，以下简称pyrolysis-MS）的光刻胶聚合物序列表征方法，可通过热解得到的低聚物片段量化短序列频率。然而，以甲基丙烯酸酯为基础的光刻胶聚合物会发生解聚与侧链断裂，生成的片段尺寸过小，无法保留序列信息。不过本研究通过计算建模发现，这些降解不稳定性本身就具有序列依赖性，可将序列信息编码于分解温度曲线之中。通过同时利用质谱与温度域信息，本研究策略可实现此前被认为无法表征的光刻胶共聚物的序列分析。此外，序列依赖性侧链不稳定性表明，光刻胶在脱保护过程中的响应性同样可能取决于单体序列。本研究提出的序列表征方法为解开长期以来的序列-LER相关性难题提供了可行途径。