Modeling studies of the chemical vapor deposition of boron films from B₂H₆

The effect of growth conditions on the chemical vapor deposition of boron thin films from diborane (B₂H₆) was investigated using a combination of experimental studies and computational fluid dynamics-based reactor modeling. A multi-physics computational model was developed to simulate the thermal-fluid environment in the reactor. The proposed chemistry model incorporated into the simulations includes gas-phase decomposition and formation of B₂H₆ and surface adsorption and reaction of borane (BH₃). The model accurately predicts the experimentally measured temperature and partial pressure dependence of the boron growth rate using the sticking coefficient of BH₃ on the growth surface as the only adjustable parameter in the calculations. The results indicate that at lower growth temperatures (<500 °C) the boron growth rate is limited by gas-phase kinetics while at higher temperatures (>500 °C) the growth rate is limited by mass transfer of BH₃ to the substrate surface. The studies of boron thin film growth are relevant to the deposition of superconducting MgB₂ thin films, in which B₂H₆ is used as the boron precursor.