Enhancing Performance of Cross-Linking Negative-Tone Chemically Amplified Photoresists by Controlling Interfacial Interactions via Molecular Hydrophilicity Adjustment

Abstract

Polyphenolic compounds, when cross-linking with polymethoxylated compounds under acidic conditions, exhibit altered solubility, enabling their application as matrix materials in chemically amplified photoresists. Herein, BPA-6-OH, a polyphenolic compound used in negative-tone lithography, is modified with hydrophobic tert-butyldimethylsilyl (TBDMS) groups to form 4-OH-TBDMS. The TBDMS modification enhances the hydrophobicity and thus adhesion of the resist to silicon wafers, increasing resistance to capillary forces during development. The adhesion work between the 4-OH-TBDMS resist and hydrophobically treated silicon wafers is 58.7 mN/m, surpassing that of the BPA-6-OH resist. Fewer residual hydroxyl groups in the exposed area of 4-OH-TBDMS resist, as confirmed by infrared (IR) spectroscopy, reduce its hydrophilicity, resulting in a greater solubility contrast between exposed and unexposed areas in the developer. Consequently, the 4-OH-TBDMS resist achieves higher resolution than BPA-6-OH, producing dense lines with a line width of 20.8 nm and a line edge roughness (LER) of 3.6 nm at 80 μC/cm², and semidense lines with a line width of 19.3 nm and an LER of 3.6 nm at 75 μC/cm² using electron beam lithography. This study introduces strategies for designing cross-linking chemically amplified photoresists and advances the development of materials for advanced lithography.