Thin-film (Al)BCN materials synthesized by sequential precursor pulses to mimic atomic layer deposition

This work brings novel insights into the existing knowledge on the deposition of films containing boron (B), carbon (C), nitrogen (N), and aluminum (Al). The (Al)BCN films are obtained at low substrate temperatures (TS) of 250-400 °C from triethylborane, ammonia (NH3), and trimethylaluminum. For BCN films, a nearly similar elemental composition of B0.42C0.41N0.15O0.02, with 1-2 at. % variations, is observed for substantial ranges of TS and NH3-exposure time. This can indicate a similar growth mechanism and/or formation of a single-phase material. While excluding precursor underdosing, a remarkable dependence of growth rate per cycle (GPC) on total gas pressure (Ptot) is observed. The GPC approaches near saturation regime for Ptot between 1 and 10 mbar, for TS = 330-375 °C, which might support the occurrence of a surface-adduct assisted pathway. The level of GPC saturation is influenced by TS. For a wide range of process conditions, N-share in the films slightly varies between 12 and 16 at. %. C-share only changes between 40 and 42 at. %. The attempt to increase N-share by dissociating NH3 into NH2 radicals by hot wire assistance remarkably shows the opposite effect, i.e., a decrease in the N-share from 15 to 6 at. %. This is accompanied by a corresponding increase in the B- and, in particular, C-shares, suggesting that the removal of carbon can occur via the incorporation of nitrogen. For AlBCN films, changing Ptot has a strong effect on their elemental composition. At Ptot = 10 mbar, Al-deficient films grow, whereas a Ptot of 0.2 mbar leads to mainly AlN-containing films with some inclusions of BN.