High wet-etch resistance SiO₂ films deposited by plasma-enhanced atomic layer deposition with 1,1,1-tris(dimethylamino)disilane

A novel precursor, 1,1,1-tris(dimethylamino)disilane {TADS, [(H₃C)₂N]₃Si₂H₃}, is used to deposit silicon dioxide (SiO₂) films in a temperature range of 115–480 °C by thermal atomic layer deposition (tALD) and plasma-enhanced atomic layer deposition (PEALD) techniques. Compared to tris(dimethylamino)silane (TDMAS), the additional Si-Si bond in TADS is expected to enhance the reactivity of the molecule due to the polarization of the bond. In the tALD process, TADS gives a growth rate of 0.06 nm/cycle, which is approximately 20% higher than that of TDMAS, and an excellent conformality (>95% step coverage) in high aspect ratio nanotrenches (6:1). In the case of the PEALD process, TADS leads to not only a higher or at least comparable growth rates (0.11 nm/cycle), but also a higher bulk film density (∼2.38 g/cm³). As a result, the PEALD SiO₂ films of TADS show a wet-etch rate down to 1.6 nm/min in 200:1 HF, which is comparable to that of the thermal oxide. Analyzed with Fourier-Transform Infrared (FTIR), the SiO₂ films contain predominant Si−O bonds and a low level of Si−H and O−H bonds, consistent with the observed high wet-etch resistance. Furthermore, the PEALD SiO₂ films deposited at 310 °C have at least 75% step coverage in high aspect ratio nanotrenches, suggesting that TADS is applicable for forming high-quality SiO₂ films on both planar and patterned surfaces.