Selective Pulsed Chemical Vapor Deposition of Water-Free TiO₂/Al₂O₃ and HfO₂/Al₂O₃ Nanolaminates on Si and SiO₂ in Preference to SiCOH

Abstract

Highly selective and smooth TiO₂/Al₂O₃ and HfO₂/Al₂O₃ nanolaminates were deposited by water-free pulsed chemical vapor deposition (CVD) at 300 °C using titanium isopropoxide (Ti(OⁱPr)₄) and hafnium tertbutoxide (Hf(O^tBu)₄) with trimethylaluminum (TMA). TMA was found to be the key factor for enhancing nucleation selectivity on SiO₂ or Si versus SiCOH (hydrophobic, nonporous low <i>k</i> dielectric). With precise dosing of TMA, selective nucleation of TiO₂/Al₂O₃ and HfO₂/Al₂O₃ nanolaminates was achieved and smoother films were formed with higher selectivity compared to single precursor TiO₂ and HfO₂ CVD. The selectivity of TiO₂/Al₂O₃ nanolaminate deposition increased from 34 to 44 (deposition on Si vs SiCOH), while RMS roughness of the film of Si decreased from 2.8 to 0.38 nm. The selectivity of HfO₂/Al₂O₃ deposition increased from 14 to 73, while the RMS roughness of HfO₂/Al₂O₃ on Si was maintained at a similar value of 0.78 nm. Deposition of water-free pulsed CVD TiO₂/Al₂O₃ and HfO₂/Al₂O₃ nanolaminates was conducted on a Cu/SiCOH patterned sample to study their nanoselectivity. Transmission electron microscopy images of the Cu/SiCOH patterned sample demonstrated that highly selective and smooth TiO₂/Al₂O₃ and HfO₂/Al₂O₃ nanolaminates can be formed on a nanoscale pattern.