Improvement of thermal stability and composition changes of atomic layer deposited HfO2 on Si by in situ O3 pretreatment

The influence of thick (1.4nm) and thin (0.6nm) SiO2 interfacial layers grown by an O3 predeposition treatment during atomic layer deposition of high-k HfO2 films on the thermal stability and chemical structure of the film was investigated. It was found that the HfO2/thick SiO2 stack maintained a good thermal stability up to the postdeposition annealing at 1000°C because Hf silicate formation was accompanied by the consumption of the interfacial SiO2 layer. On the other hand, the HfO2/thin SiO2 layer stack showed an inferior stability because Hf silicate was formed by enhanced Si diffusion from the Si substrate during the same postdeposition annealing.