Advancing next generation nanolithography with infiltration synthesis of hybrid nanocomposite resists†
Organic–inorganic hybrid resists are emerging as an effective way of addressing stringent process requirements for aggressive down-scaling of semiconducting devices. However, hybrid resists generally require complex chemical synthesis while being predominantly negative-tone with high dose requirements. For positive-tone processes and high-aspect-ratio pattern transfers, resist choices are limited to costly, non-hybrid alternatives, whose etch resistance is still inferior compared with hybrid resists. Here, we demonstrate a novel hybrid positive-tone resist platform utilizing simple ex situ vapor-phase inorganic infiltration into standard resist materials. A model system based on poly(methyl methacrylate) (PMMA) thin film hybridized with aluminum oxide has been demonstrated for electron-beam lithography patterning, featuring a fully controllable critical exposure dose, contrast, and etch resistance. The hybrid resist not only achieves contrast as high as ∼30, six-fold enhancement over standard PMMA, but also enables Si nanostructures with resolution down to ∼30 nm and an aspect ratio as high as ∼17, owing to enhancement of the Si etch selectivity to ∼70, with an estimated achievable maximum of ∼300, far exceeding known commercial positive-tone resist systems. The easy implementabilility, combined with versatile ex situ control of resist characteristics, makes this hybrid resist synthesis approach uniquely suited for addressing the resist performance and high throughput required for advanced nanolithography techniques, such as extreme ultraviolet lithography, potentially.