Sequential Infiltration Synthesis of Silicon Dioxide for Nanopatterning-Based Technological Advancements*

Emerging strategies for synthesizing nanometer-scale silicon dioxide (SiO2) patterns have garnered attention due to their potential applications in microelectronics, optoelectronic device manufacturing, and bio-sensors, among others. As dimensions continue to shrink below 10 nm, the use of conventional optical lithography for nanopatterning dielectrics like SiO2 has become increasingly challenging. In response to this challenge, Sequential Infiltration Synthesis (SIS) has emerged as an appealing alternative. SIS is a two-step gas-phase molecular assembly process that leverages self-assembled block copolymers (BCPs) as templates to enable localized inorganic material growth in specific reactive domains of polymers with interactive functional groups. In this study, we investigate the SIS of SiO2 to facilitate nanomaterial growth and nanopattern fabrication on substrates. Our approach involves in situ Fourier Transform Infrared Spectroscopy (FTIR) measurements during SiO2 SIS to delve into the hybrid molecular assembly, focusing on the reaction mechanism between trimethylaluminum (TMA) and tri(tert-pentoxy) silanol (TPS) precursors and polymers with ester functional groups, including polymethyl methacrylate (PMMA), Poly(ethyl methacrylate) (PEMA), Polycaprolactone (PCL), and Poly(t-butyl methacrylate) (PBMA). FTIR provides insights into the extent of interactions between polymers and precursors, shedding light on SiO2/SiOx growth after each SIS cycle. Notably, PMMA and PEMA exhibited a lower participation of functional groups in reactions, leading to the formation of weak and unstable complexes. In contrast, PCL and PBMA demonstrated nearly complete involvement of functional groups in reactions, resulting in stable and irreversible interactions with TMA. It's worth highlighting that the quantity of SiO2 formed does not linearly correlate with the number of interacting functional groups. These findings elucidate the SiO2 SIS mechanism using in situ FTIR and pave the way for effective templated nanopatterning of SiO2 for applications requiring low-dimensional dielectric materials. This research contributes to cutting-edge technology in the fields of microelectronics, optoelectronics, and beyond.