THERMAL-STABILITY OF METAL-ELECTRODES (PT, RU, AND IR) ON POLYCRYSTALLINE SILICON IN FERROELECTRIC CAPACITORS

Electrode materials such as Pt, Ru, and Ir on polycrystalline silicon were annealed and the thermal stability was investigated to check the feasibility of the structure. Sputtered Pt reacted with silicon to for m PtSi at a low temperature of 400 degrees C and the top layer of sili cide was oxidized in oxygen ambient. Ru and Ir films by sputtering wer e also silicidized above 550 degrees C and it made voids beneath silic ide layers. All of the films are found to allow oxygen to diffuse thro ugh them and to get the underlying layers oxidized. However, Ir deposi ted by e-beam evaporation did not form silicide up to 700 degrees C an d did not get oxidized up to 550 degrees C. Ir also allowed oxygen dif fusion when annealed at 550 degrees C or lower temperature, but it was prevented when annealed at 700 degrees C.