Selective ALD of SiN using SiI4 and NH3: The effect of temperature, plasma treatment, and oxide underlayer

Abstract

The initial growth of silicon nitride (SiN) thin films was studied during thermal atomic layer deposition (ALD) using silicon tetraiodide (SiI4) and ammonia (NH3) onto various oxide underlayers (native SiO2, sapphire, ALD Al2O3, and ALD ZrO2) at two deposition temperatures (200 and 350 °C). We found that the SiI4/NH3 process shows earlier nucleation on high-k oxide underlayers (sapphire, ALD Al2O3, and ALD ZrO2) compared with SiO2 at 200 °C. Interestingly, an NH3-plasma treatment reverses the selectivity between high-k oxides and SiO2: SiN growth has no nucleation delay on NH3-plasma-treated SiO2 but is severely delayed on NH3-plasma-treated high-k oxides at both temperatures (an incubation period of at least 300 cycles at 200 °C and 50 cycles at 350 °C).