Abstract:

Microelectronics underpin virtually every aspect of modern technology, and continued advances in their performance and miniaturization depend critically on the ability to fabricate increasingly smaller features on semiconductor devices. The continued scaling of these devices has placed increasing demands on photoresist materials, exposing fundamental limitations in the chemically amplified resists (CARs) that have long underpinned semiconductor lithography. These issues primarily stem from chemical heterogeneity imparted by conventional polymer synthesis and formulation which, along with insufficient absorption of extreme ultraviolet (EUV) radiation, contributes to degraded patterning resolution and process reliability at the nanoscale. Sequence-defined polymers are an emerging class of materials that offers a possible solution to these problems. By precisely controlling chain length, monomer sequence, and sidechain identity, these materials are uniquely suited to isolate and interrogate the molecular-level factors governing resist performance that are otherwise obscured by the heterogeneity of conventional materials. However, much remains unknown about how these structural properties influence patterning.

This work utilizes sequence-defined polypeptoids as a model platform for understanding the roles of sequence and chemistry on patterning performance. First, systematic studies of sequence and chain length effects revealed that monomer arrangement significantly influences patterning resolution, establishing sequence as an actionable design variable in resist development. Second, iodine-bearing sidechains were incorporated into polypeptoid photoresists to understand the impacts of strongly EUV-absorbing elements on electron generation and sensitivity. Finally, the monodisperse nature of polypeptoids was leveraged to investigate the critical ionization (CI) model for resist dissolution and gain insight into the mechanisms governing development. Collectively, these results demonstrate that synthetic precision is a powerful and underutilized lever in photoresist design, and that sequence-defined polymers offer a compelling platform for both advancing next-generation lithographic materials and deepening fundamental understanding of the polymer physics that governs them.