A Single-Component Molecular Glass Resist Based on Tetraphenylsilane Derivatives for Electron Beam Lithography

A novel molecular glass (TPSiS) with photoacid generator (sulfonium salt group) binding to tetraphenylsilane derivatives was synthesized and characterized. The physical properties such as solubility, film-forming ability, and thermal stability of TPSiS were examined to assess the suitability for application as a candidate for photoresist materials. The sulfonium salt unit underwent photolysis to effectively generate photoacid on UV irradiation, which catalyzed the deprotection of the t-butyloxycarbonyl groups. It demonstrates that the TPSiS can be used as a 'single-component' molecular resist without any additives. The lithographic performance of the TPSiS resist was evaluated by electron beam lithography. The TPSiS resist can resolve 25 nm dense line/space patterns and 16 nm L/4S semidense line/space patterns at a dose of 45 and 85 μC/cm² for negative-tone development (NTD). The etching selectivity of the TPSiS resist to Si substrate is 8.6 under SF₆/O₂ plasma, indicating a potential application. Contrast analysis suggests that the significant solubility switch within a narrow exposure dose range (18-47 μC/cm²) by NTD is favorable for high-resolution patterns. This study supplies useful guidelines for the optimization and development of single-component molecular glass resists with high lithographic performance.