Fabrication of sub-10 nm Si nanowires via self-assembly and carbon-based etching transfer for future applications in Si nanowire biosensors

Abstract Silicon nanowire (SiNW) biosensors, based on the field-effect transistor mechanism, demonstrate high sensitivity, specificity, and label-free operation. Although our previous work demonstrated enhanced sensing performance using ultrathin 10.8 nm SiNWs fabricated by electron beam lithography, scaling below the 10 nm threshold remains challenging. In this study, block copolymer (BCP) self-assembly was employed to fabricate sub-10 nm nanowires. Using low-molecular-weight polystyrene-block polydimethylsiloxane (PDMS), PDMS nanowires with widths of approximately 10 nm were formed. However, these nanowires exhibited insufficient etch resistance for pattern transfer into silicon by reactive ion etching. To overcome this issue, two approaches were investigated. Thermal annealing at 300 °C–400 °C with various durations was performed; however, no improvement in etch resistance was observed. In contrast, a selective carbon-layer transfer process, exploiting high Si:C etch selectivity, successfully preserved nanowire morphology with widths as narrow as 9.3 nm. This method provides a practical route for integrating BCP-based sub-10 nm SiNW fabrication.