Characterization and reliability measurement issues in devices with novel gate stack devices

Since high-k materials are very different from SiO2, both structurally and electrically, conventional characterization and reliability methods that have been developed for SiO2 devices may not be applicable to high-k dielectric devices.Fast transient charging effects degrade the drive current of high-k devices due to electron trapping in the gate dielectric. Because of this phenomenon, conventional DC drain current–gate voltage (Id–Vg) measurements may underestimate the drain current, which translates to lower extracted mobility values, which has been confirmed by ultra short pulse measurements.The fast spontaneous post-stress relaxation phenomenon could complicate the assessment and interpretation of the threshold voltage (VTH) instability in high-k devices. The results obtained with a novel inversion pulse measurement method demonstrate that the VTH relaxes after a post-stress period of a couple of hundred microseconds. Consequently, the magnitude of VTH instability is underestimated when a relatively slow switching matrix is used for the stress/sense measurements.