Platinum Hillocks in Pt/Ti Film Stacks Deposited on Thermally Oxidized Si Substrate

Abstract

The stress dependence of platinum hillock formation during post thermal cycling was investigated in Pt/Ti electrode stacks. Annealing temperatures were varied from room temperature (RT) to 650°C. High compressive stress was generated during electrode annealing by the Ti diffusion into the platinum layer followed by oxidation in the platinum grain boundaries. The compressive stress was the major driving force for the hillock formation on the platinum surface. Thus, the Ti glue layer was oxidized before platinum deposition to reduce the Ti diffusion. The Pt/TiO x electrode stack retained its smooth platinum surface after the electrode annealing of 650°C for 30 min in O 2 . The Pt/TiO x interface remained flat even after the ferroelectric annealing at 800°C, which was performed after SrBi 2 Ta 2 O 9 (SBT) deposition. Moreover, the remanent polarization (2 P r ) of the SBT capacitor was increased to 17 µC/cm 2 on the Pt/TiO x electrode stack, up from 13 µC/cm 2 , which was the value on the Pt/Ti electrode stack.