Investigation of c-Si surface passivation using thermal ALD deposited HfO2 films

Abstract Thermal Atomic Layer Deposition (ALD) based Hafnium oxide (HfO 2 ) films grown on n-type Float Zone (FZ) c-Si are investigated as passivation layers. In order to reach optimum passivation, one needs an adequate choice of film growth variables, preceded by the proper pre-growth surface conditioning and the post deposition thermal treatment of the film. Provided a set of deposition parameters, annealing of the film grown on OH-terminated Si surfaces in air led to the lowest Surface Recombination Velocity (SRV) value reported in the literature using a single layer of HfO 2 , namely a value of 1.2 cm/s for a 15 nm thick HfO 2 . The SRV is extracted from the measured carrier's effective lifetime. Field effect passivation accounts for this performance as shown by the oxide charges density (Q tot ) values extracted from the C-V measurements. The chemical passivation contribution, although suspected to be as important, cannot be established in a definite manner due to inherent limitations of the experimental method (high frequency C-V) used to extract the reported D it values corresponding to the interface state density of defects at the interface HfO 2 /Si.