Unfolding an Elusive Area-Selective Deposition Process: Atomic Layer Deposition of TiO₂ and TiON on SiN vs SiO₂

Abstract

Area-selective atomic layer deposition (AS-ALD) processes for TiO₂ and TiON on SiN as the growth area vs SiO₂ as the nongrowth area are demonstrated on patterns created by state-of-the-art 300 mm semiconductor wafer fabrication. The processes consist of an in situ CF₄/N₂ plasma etching step that has the dual role of removing the SiN native oxide and passivating the SiO₂ surface with fluorinated species, thus rendering the latter surface less reactive toward titanium tetrachloride (TiCl₄) precursor. Additionally, (dimethylamino)trimethylsilane was employed as a small molecule inhibitor (SMI) to further enhance the selectivity. Virtually perfect selectivity was obtained when combining the deposition process with intermittent CF₄/N₂ plasma-based back-etching steps, as demonstrated by scanning and transmission electron microscopy inspections. Application-compatible thicknesses of ∼8 and ∼5 nm were obtained for thermal ALD of TiO₂ and plasma ALD of TiON.