Plasma-Enhanced Atomic-Layer Deposition of Nanometer-Thick SiN_x Films Using Trichlorodisilane for Etch-Resistant Coatings

In recent times, the requirements have become extremely stringent for employing silicon nitride (SiNx) films in various types of applications. For instance, high etch resistance coating is required for a film to act as an etch stop layer and gate spacer for nanoscale patterning for next-generation semiconductor devices. In this study, a chlorodisilane precursor, 1,1,1-trichlorodisilane (3CDS, Si2H3Cl3), was used to deposit SiNx films using a hollow cathode plasma-enhanced atomic layer deposition system and compared with the SiNx films deposited using hexachlorodisilane (HCDS, Si2Cl6) as well as pentachlorodisilane (PCDS, Si2HCl5). In the process temperature range of 310–435 °C, a self-limiting surface reaction behavior with 4 × 103 L of 3CDS exposure and 2 × 106 L of NH3 plasma exposure was observed. 3CDS particularly gives ∼45 and ∼20% higher growth per cycle than HCDS and PCDS, respectively. In addition, the SiNx films deposited using 3CDS at 480 °C have improved the wet etch rate (0.4 nm/min in 200:1 HF) and density (2.88 g/cm3). Analyzed with time-of-flight secondary ion mass spectrometry, the 3CDS-derived SiNx films contain less hydrogen than the SiNx films formed using HCDS under identical process conditions. These superior film properties can be attributed to the unique structural characteristics of 3CDS, where the three chlorine and three hydrogen atoms are localized on each of the two silicon atoms. The SiNx films deposited on nanotrenches with a high aspect ratio (6:1) at 390 and 480 °C showed >85% and >65% conformality, respectively, and high etch resistance (1.9 and 0.8 nm/min, respectively, in 200:1 HF), suggesting that high-quality SiNx films can be formed from 3CDS on both planar and patterned surfaces.