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.