Scientists from Tokyo Tech and TOK have reported that a newly developed block copolymer could significantly enhance integration and miniaturization in semiconductor manufacturing. This innovative compound is chemically engineered for precise directed self-assembly and can form perpendicular lamellar structures with a half-pitch width of under 10 nanometers, surpassing traditional block copolymers.
Miniaturization plays a crucial role in modern electronic devices and has been key to the remarkable performance improvements seen over recent decades. To continue this trend, it’s essential to create even finer circuit patterns on semiconductor chips, which are vital components in all electronics. Experts predict that by 2037, the minimum distance between features in semiconductor devices—referred to as ‘half-pitch’—will need to shrink to around 8 nanometers, highlighting the importance of enhancing lithographic techniques (the process of crafting intricate circuit patterns on semiconductor materials).
As expected, generating such detailed structures across any material is a significant challenge. One promising approach to this challenge is directed self-assembly (DSA) using block copolymers (BCPs). In simple terms, BCPs consist of long, chain-like molecules formed from two or more different polymer sections, known as blocks. The DSA process takes advantage of the interactions among the various blocks in BCPs to enable them to spontaneously and systematically arrange into organized structures. Despite the efficacy of this method, creating features smaller than 10 nanometers (sub-10 nm) via DSA remains difficult.
A recent study published on July 6, 2024, in Nature Communications, from the Tokyo Institute of Technology (Tokyo Tech) and Tokyo Ohka Kogyo (TOK), has extended the horizons of what is achievable in this area. The research team, led by Professor Teruaki Hayakawa, developed a new BCP meticulously designed to create extremely small line patterns on a substrate in the form of lamellar domains (which consist of finely layered structures). These minuscule patterns could lay the groundwork for novel semiconductor technologies.
The new BCP was formulated from polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA), a well-known and extensively researched BCP suitable for DSA. Initially, the researchers infused the PS-b-PMMA with an adequate proportion of poly(glycidyl methacrylate) (PGMA), resulting in PS-b-(PGMA-r-PMMA). They then further refined the PGMA segment using various thiols to enhance the repulsive interactions among the different polymer blocks, creating PS-b-PGFM. The PS and PMMA segments also influence how the molecule interacts with air, a key factor in its self-alignment during DSA.
The specially designed BCP consistently self-formed extremely small nanometric lamellar structures when applied as a thin film, as verified by atomic force microscopy. Additionally, this new compound exhibited strong performance on a substrate with parallel polystyrene chemical guides.
“Thin-film aligned lamellar domains oriented vertically were reliably and reproducibly obtained through directed self-assembly, achieving parallel line patterns with a half-pitch size of 7.6 nm,” states Hayakawa. Notably, this measurement is among the smallest half-pitch sizes reported globally for thin-film lamellar structures without a top layer.
Overall, these remarkable developments could significantly propel advanced technologies in semiconductor fabrication. “PS-b-PGFM BCPs present promising templates for lithography applications since they can create fine patterns in DSA methods similar to conventional PS-b-PMMA, with the potential to excel beyond them,” concludes Hayakawa, while also expressing intentions for future research aimed at refining pattern-transfer techniques using line patterns in PS-b-PGFM thin films as templates.
These breakthroughs may bring us closer to entering a new phase in electronics and artificial intelligence systems.
