Atomic layer deposition of B2O3/SiO2 thin films and their application in an efficient diffusion doping process

Abstract

We investigated atomic layer deposition (ALD) of B₂O₃ and SiO₂ thin films using trimethylborate (TMB) and bis-(diethylamino)silane (SAM-24) precursors, focusing on growth characteristics and film properties. For both cases, ALD processes using O₃ and O₂ plasma as reactants exhibited well-defined growth saturation and linear growth behavior without any incubation cycles, and produced highly pure, stoichiometric films. In the case of B₂O₃ films, however, SiO₂ layer passivation is required onto the B₂O₃ due to a spontaneous decomposition caused by moisture in air. On the basis of electrical characterization, the detailed dielectric properties of SiO₂ and B₂O₃/passivation SiO₂ films were extensively discussed including the k-value, flat band voltage, and leakage currents. Then, boron-doped SiO₂ films with different B/(B + Si) compositions were prepared by controlling B₂O₃ and SiO₂ growth cycles, followed by drive-in annealing and a subsequent wet removal process. Based on both theoretical estimation and SIMS depth profile results, we demonstrated that the surface doping concentration is effectively modulated with controllable B doping contents in the B-doped SiO₂ films.