Interface passivation mechanisms in metal gated oxide capacitors

We use the conductance technique to measure the density of interface states, D_it, in MOS capacitors with metal gate electrodes. D_it as a function of the band gap is extracted for a series of capacitors. ALD TiN electrodes show poor passivation while PVD TaN electrodes do not. There is no evidence that the poor passivation in the TiN electrodes is because of low hydrogen diffusion through the metal oxide stack. Possibly, the strain induced by the ALD metal layer or contamination from the metal precursors are responsible for the poor passivation.