Atomic layer deposition of wet-etch resistant silicon nitride using di(sec-butylamino) silane and N2 plasma on planar and 3D substrate topographies

The advent of three-dimensional (3D) finFET transistors and emergence of novel memory technologies place stringent requirements on the processing of silicon nitride (SiNx) films used for a variety of applications in device manufacturing. In many cases, a low temperature (<400 °C) deposition process is desired that yields high quality SiNx films that are etch resistant and also conformal when grown on 3D substrate topographies. In this work, we developed a novel plasma-enhanced atomic layer deposition (PEALD) process for SiNx using a mono-aminosilane precursor, Di(Sec-ButylAmino)Silane (DSBAS, SiH3N(sBu)2), and N2 plasma. Material properties have been analysed over a wide stage temperature range (100 – 500 °C) and compared with those obtained in our previous work for SiNx deposited using a bis-aminosilane precursor, Bis(Tert-ButylAmino)Silane (BTBAS, SiH2(NHtBu)2), and N2 plasma. Dense films (∼3.1 g/cm3) with low C, O and H contents at low substrate temperatures (<400 °C) were obtained on planar substrates for this process when compared to other processes reported in the literature. The developed process was also used for depositing SiNx films on high aspect ratio (4.5 : 1) 3D trench nanostructures to investigate film conformality and wet-etch resistance (in dilute hydrofluoric acid, HF : H2O = 1 : 100) relevant for state-of-the-art device architectures. Film conformality was below the desired levels of >95% and is attributed to the combined role played by nitrogen plasma soft saturation, radical species recombination and/or ion directionality during SiNx deposition on 3D substrates. Yet, very low wet-etch rates (WER ≤2 nm/min) were observed at the top, sidewall and bottom trench regions of the most conformal film deposited at low substrate temperature (<400 °C), confirming that the process is applicable for depositing high quality SiNx films on both planar and 3D substrate topographies.