Synthesis of Novel Soft-Hard Block Copolymers and Their Applications to Next Generation Nano Lithography

Abstract

Self-assembled nanoscale patterns from block copolymers are highly promising for future nanofabrication due to their extremely high resolution and cost-effectiveness. However, conventional block copolymers have shown at least one of the limitations such as insufficient ordering, low etch selectivity, or the requirement of additional neutral surface treatment for orientation control. Here, we report the controlled self-assembly of a novel poly(dodecylphenylacrylamide-b-methyl methacrylate) (PDOPAM-PMMA) BCP, which is composed of a new crystalline and hard PDOPAM block and an amorphous and soft PMMA block. The proposed BCP offers diverse advantages for nanolithography compared to conventional BCP materials. First, PDOPAM-PMMA showed exceptional long-range ordering with minimal defect density over a 10 μm scale without relying on guiding templates. Second, perpendicular alignment of lamellar and cylindrical microdomains on a substrate was realized without any neutral brush coating. The formation of patterns with a high-aspect ratio consequently was significantly faster than with previously reported methods. Third, the etch selectivity between the two constituent blocks under plasma exposure was high enough for lithography applications. Fourth, the PDOPAM block was selectively decorated using various metallic salts, enabling extensive and uniform generation of metallic lines, dots, and mesh nanostructures. Fifth, bulk PDOPAM-PMMA BCP with a cylindrical morphology exhibited microdomains with an unusual square-symmetry. To sum, the key advancement of this study is that critical desirable aspects in self-assembled pattern formation was realized by using only the novel PDOPAM-PMMA BCP designed, synthesized, and processed in this work for sub-20 nm lithography application. Therefore, our novel hybrid block copolymer with universal characteristics may pave a new pathway to create, tailor, and transform nanoscale patterns with high fidelity.