Area-Selective ALD of TiO2 Nanolines with Electron-Beam Lithography

We demonstrate a bottom-up approach to fabricate nanoline structures using self-assembled monolayer (SAM) modified substrates to selectively prevent nucleation during atomic layer deposition (ALD). Low-energy (≤5 kV) electron-beam lithography (EBL) was used to modify the hydrophobic functional groups (−CH3) of octadecyltrichlorosilane (OTS) SAM to hydrophilic species (e.g., −COOH), which allows chemisorption of the titanium isopropoxide (TTIP) and water to initiate titanium oxide (TiO2) nucleation. TiO2 thin films were selectively deposited on the OTS molecules which were properly functionalized or patterned. We systematically investigate the effects of e-beam dose and accelerating voltage on selective TiO2 deposition with nanoline patterns. The results indicate that the former parameter determines the resolution of individual line width, while the latter one is attributed to the minimum pitch dimension of dense line patterns achievable. Using the optimal e-beam parameters, i.e., accelerating voltages of 1–2 kV and a line dose of 10 nC/cm, TiO2 nanolines with a maximum resolution of 30 nm and a minimum pitch of 50 nm were achieved. This study offers a new approach to fabricate close-packed nanopatterns for IC devices without any challenging etching processes.