Development of Silicon-Gradient Block Copolymers as EUV Lithography Inorganic Pattern Masks

The production of finer patterns with enhanced qualities is more emphasized, owing to the elevated demand for device performance. The utilization of extreme-ultraviolet lithography (EUVL) as the next-generation lithographic technique has become increasingly prominent. Nevertheless, failures arising from the reduction of the thickness of photoresists and inherent stochastic defects intensified along with the reduction in the pattern sizes. The defects substantially compromise the productivity and performance of the devices. Directed self-assembly (DSA) of block copolymers became a viable solution to overcome the limitations of EUVL. The DSA process not only improves pattern roughness but also facilitates the production of finer patterns at increased throughputs. Still, integration of DSA into EUVL presents the following challenges including increased complexity of the process related to surface energy neutralization, limited etching selectivity for effective pattern transfer, and undefined polymerization methods constraining its application within production processes.<br/>Here, novel block copolymers with organosilicon gradients, Poly(methyl methacrylate)-block-poly(((bis(trimethylsilyl)methyl)acetamide)-gradient-styrene) (PMMA-b-P(Si₂-g-S)) and Poly(methyl methacrylate)-block-poly((Polyhedral oligomerized silsesquioxanes)acetamide)-gradient-styrene) (PMMA-b-P(POSS-g-S), are presented. These BCPs were engineered to overcome the challenges of DSA based on the three pivotal design principles. First, the incorporation of gradient random copolymer blocks is leveraged to facilitate the generation of vertically aligned patterns, irrespective of substrate surface properties. Next, novel organosilicon polymers are introduced, serving as a robust mask for pattern transfer with high etch resistance. Third, by integrating a reactive polymer, a versatile block copolymer synthesis platform is established. This platform enables the generation of various block copolymers from a single reactive precursor block copolymer. Notably, synthesized PMMA-b-P(Si₂-g-S) and PMMA-b-P(POSS-g-S) block copolymers exhibit highly ordered, vertically aligned lamellar patterns on diverse surfaces. After undergoing directional alignment and selective etching procedures, the gradient organosilicon block demonstrates its effectiveness and robustness as a pattern transfer mask. This novel block copolymer system thus presents a promising platform for efficient pattern transfer, addressing the challenges associated with integrating DSA into EUVL.