Effects of long-time DC bias on D2O- and D2/N2-annealed BST thin films

Abstract

Effects of long time dc bias on both D2O- and D2-annealed BST thin films were investigated by secondary ion mass spectrometry (SIMS) analysis and electrical measurements before and after bias stressing. Bias conditions were sufficient to cause the degradation of (1) subsequently-measured current density-voltage characteristics and (2) a significant positive shift of the capacitance-voltage curve along the voltage axis. This latter effect may be attributed to the asymmetric space charge distribution in the BST thin film after bias stressing or, possibly, to changes in the interface state density. No significant deuterium motion was observed in D2O-annealed capacitors biased at an elevated temperature or in D2/N2-annealed capacitors biased at room temperature in high electric fields (∼3.5 × 107 V/m) for more than 8 hours. The small values of the Di• mobility which were inferred from the SIMS results are consistent with recent data on the kinetics of deuterium incorporation in and removal from similar BST thin films.