Degradation mechanisms of SrBi2Ta2O9 ferroelectric thin film capacitors during forming gas annealing

The effects of annealing in forming gas (5% hydrogen, 95% nitrogen; FGA) ar e studied on spin coated SrBi2Ta2O9 (SBT) thin films. SET films on platinum bottom electrode are characterized with and without platinum top electrode by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), High Temperature X-Ray Diffraction (HT-XRD) and Secondary Ion Mass Spectrom etry (SIMS). High Temperature X-Ray Diffraction (HT-XRD) of blanket Ti/Pt/SBT films in f orming gas revealed that the bismuth layered perovskite structure of the SE T is stable up to approx. 500 degreesC. SIMS analysis of Pt/SBT/Pt samples annealed in deuterated forming gas (5% D-2, 95% N-2) showed that the hydrog en accumulates in the SET layer and at the platinum interfaces next to the SET. After FGA of blanket SET films, tall platinum-bismuth whiskers are see n on the SET surface. Performing the FGA of the whole Pt/SBT/Pt/Ti stack, two different results a re found. For the samples with a high temperature annealing (HTA) step in o xygen after top electrode patterning, top electrode peeling is observed aft er FGA. For the samples without a HTA step after top electrode patterning, no peeling is observed after FGA.