Thin Pt layer insertion into the Ru bottom electrode: effects on the surface morphology of a (Ba, Sr)TiO3 dielectric film and on the performance of the TiN barrier in the pt/Ru/TiN/p-Si/Si heterostructure

Abstract

We have investigated the effects of inserting a thin Pt layer into the bottom electrode heterostructure and of post-treatment by rapid thermal oxidation (RTO) on the surface morphology of Ba1−xSrxTiO3 (BST) films and on the thermal stability of the TiN barrier under oxygen exposure in a Pt/Ru/TiN/Si structure. In the case of the Ru/TiN/p-Si/Si structure without a Pt thin layer, the surface morphology of the Ru layer was rough due to heterogeneous grain growth formation, which resulted in the degradation of the BST/Ru interface. When a thin Pt layer was inserted on top of the Ru layer, the number of faceted protrusions observed for the Ru layer was either largely decreased for the Pt/Ru/TiN/p-Si/Si structure or unobserved for the BST/Pt/Ru/TiN/p-Si/Si structure. For the BST/Pt/Ru/TiN/p-Si/Si structure, the oxygen in-diffusion can be reduced by the BST/Pt layers during RTO in the two-step annealing process, resulting in the observed smooth surface morphology of the BST/Pt layer. The thermal stability of the TiN barrier for the Pt/Ru/TiN/poly-Si/Si layer structure was found to be up to 650 °C. This was attributed to the role of the thin oxidized RuOx layer formed at the surface of the Ru film and the thin Pt layer. Consequently, the surface morphology of the BST film and the performance of the TiN barrier can be simultaneously improved by the introduction of a thin Pt layer and by post-treatment for a Ru/TiN/p-Si/Si structure.