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.
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