Growth mechanism study of boron nitride atomic layer deposition by experiment and density functional theory

We investigated the fundamental mechanisms determining the limit of the atomic layer deposition (ALD) temperature window by density functional theory (DFT) simulations. Boron nitride (BN) ALD experiments were performed using BCl3 or tris-dimethylaminoborane (TDMAB) and NH3 on Si(100) substrates to check whether the ALD temperature window exists or not. With increasing the growth temperature, an increase in growth per cycle (GPC) between 700 and 900 °C was relatively small in the BCl3 and NH3 system, while the GPC exponentially increased in the TDMAB and NH3 system. Based on the experimental results, we performed DFT simulations to investigate the reaction mechanisms determining the lower ALD temperature window in the BCl3 and NH3 systems. The two initial reactions and two cyclic reactions were numerically analyzed: (a) BCl3 reactions on OH-terminated Si(100) surface, (b) NH3 reactions on Cl-terminated Si(100) surface, (c) BCl3 reactions on H-terminated BN surface, and (d) NH3 reactions on Cl-terminated BN surface. We found activation energies for reaction (c) is 30.0 kcal/mol, determining the lower limit of the ALD temperature window. The activation temperature of reaction (c) is obtained 789 °C which is just in the ALD temperature window by our experiments.