Scalable fabrication of high-performance spin-on carbon hardmask via carbonization

This study presents a novel fabrication scheme for amorphous carbon hard masks that addresses critical limitations of conventional spin-on carbon (SOC) polymer hardmasks and chemical vapor deposition (CVD) amorphous carbon processes. Instead of relying on conventional spin-on carbon hardmasks that contains aliphatic carbons that exhibit low thermal resistance and poor carbonization yields, this approach employs aromatic polymer precursors with superior thermal resistivity and carbonization efficiency. Three aromatic polymers (biphenyl tetracarboxylic dianhydride-based polyimides with 4,4′-diaminoterphenyl and m-tolidine, and poly(para-phenylene)) and conventional hardmask polymer (anthracene-phenol-divinylbenzene terpolymer) are evaluated. Thermal carbonization at 700 °C achieves high carbonization yields up to 82.5 % for poly(para-phenylene), representing a significant improvement over conventional aliphatic-based systems. The aromatic backbone structures demonstrate superior thermal resistivity, preventing volatile compound formation that typically degrades carbonization efficiency in aliphatic systems. The resulting amorphous carbon films exhibit enhanced performance through higher carbon content and reduced heteroatom concentrations. This translates to substantial improvements, with CF₄ and O₂ plasma etch rates decreasing up to by 42 %, while mechanical modulus increases up to 180 %. Our spin-coating and subsequent carbonization scheme enables batch processing with reduced particle defects compared to CVD systems while achieving superior performance over conventional spin-on carbon hardmasks.