Process window extension of TiN diffusion barrier using preoxidation of Ru and RuOx film for (Ba,Sr)TiO3 dielectric film

Abstract

The effect of a thin RuOx layer formed at the surface of the bottom electrodes by various preoxidation temperatures on the electrical properties of TiN barrier layer during two step annealing was investigated. The Ru(100 nm)/TiN/p-Si/Si contact system showed the ohmic behavior at the forward bias up to 550 °C, whereas the RuOx(100 nm)/TiN/p-Si/Si contact system exhibited the double Schottky characteristics at 400 °C, attributing to no formation of thin RuOx layer at the RuOx surface and porous amorphous microstructure. In particular, when the preoxidation time is decreased from 3 to 1 min, the electrical properties for the Ru(30 nm)/TiN/p-Si/Si contact system are improved, as compared to that for the Ru(100 nm)/TiN/p-Si/Si contact system. An oxygen incorporated at the surface of the Ru film by preoxidation plays a role in the formation of a thin RuOx layer and chemically strong Ru–O bonds, and is strongly stuffed along the grain boundaries as well as grains. It leads to the retardation for oxygen diffusion due to complex diffusion paths. In particular nonstoichiometric state, RuOx layer formed at the Ru surface is changed to the stoichiometric state, RuO2 crystalline phase after two step annealing, which can act as an oxygen sink layer. Correspondingly, we can conclude that electrical properties for the Ru/TiN/p-Si/Si contact system are better than that for the RuOx/TiN/p-Si/Si contact system.