Initial nucleation and growth of atomic layer deposited HfO2 gate dielectric layers on Si surfaces with the various surface conditions using in situ medium energy ion scattering analysis

Abstract

The initial nucleation and growth of atomic layer deposited HfO2 films under various surface conditions were investigated by in situ medium energy ion scattering analysis. The influences of an O–H terminated surface on the initial growth stage were investigated in detail using the atomic density of Hf that reacted on the surface. The measured growth rate of HfO2 per cycle was applied to a mathematical model based on classical chemical kinetics. A parabolic initial growth with an extremely low rate at the initial stage of growth was observed for the film with a hydrogen-terminated surface. However, linear growth, with a value of 1.41×1014Hfatoms∕cm2cycle, was maintained for films grown on an O–H terminated surface. The ∼1∕6 steric hindrance factor extracted from a phenomenological model was related to the size of the tetrahedral HfCl4 molecule and the possible attachment sites. Moreover, the surface roughness and electrical properties of the atomic layer deposited HfO2 films show a strong dependence on the initial nucleation and growth on the different surface conditions.