Publication Date

Fall 2025

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical and Materials Engineering

Advisor

Dahyun Oh; Frances Houle; Melanie McNeil

Abstract

The dissolution of the photoresist is a critical step in the lithography process, which can directly impact the production yield of the semiconductor industry due to its influence on the surface roughness and line-edge-roughness (LER) of the pattern. One of the key parameters in understanding the dissolution of the polymer resist is identifying its critical ionization (CI) level, which is the minimum fraction of the acidic polymer chain required to be ionized by OH- ions, to become soluble in the basic developer. However, the exact CI level of a resist polymer has never been identified. This study aims to identify the CI level of a polymer resist and gain fundamental insight into the resist dissolution using the sequence defined and fixed chain length polypeptoids. The polypeptoids were synthesized with varying ionizable monomer contents, different chain ends, and spatial arrangements of the ionizable monomers. The quartz crystal microbalance (QCM) was used to measure the dissolution of the polypeptoids in the tetramethylammonium hydroxide (TMAH) developer, and the film thicknesses were measured by the ellipsometer. The kinetic simulation models were built using a Kinetiscope simulator to understand the dissolution mechanism. It was found that the CI level of the polypeptoids is 20%, and the dissolution rate of the polypeptoids increases linearly with the ionizable monomer content. The simulation models also demonstrate that the CI model is applicable to the dissolution of the polypeptoids in the undiluted developer. The study also found that the spatial arrangement of the ionizable monomer does not influence the dissolution rate.

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Available for download on Sunday, August 15, 2027

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