Hot-Carrier- and Constant-Voltage-Stress-Induced Low-Frequency Noise in Nitrided High- $k$ Dielectric MOSFETs

Understanding and minimization of low-frequency noise (LFN) originating from high- k (HK) gate dielectrics in new generation MOSFETs are of critical importance to applications in RF, analog, and digital circuits. To understand the effect of stress conditions on noise, nMOSFETs were subjected to accelerated hot-carrier stress (HCS) and positive constant-voltage stress (CVS). The additional LFN introduced through stressing was evaluated on nMOSFETs with TiN metal gate and HfSiON gate dielectric. Nitridation of HfSiO gate-dielectric MOSFETs was achieved by either a high-temperature NH₃ anneal or a lower temperature plasma anneal. Influence of different dielectric nitridation procedures on the stress-induced degradation of transconductance, threshold properties, and LFN was studied. Worst degradation conditions, i.e., V_g = V_d, were used for HCS, whereas for CVS, the vertical field was fixed at 10 MV/cm for all transistors to achieve comparable stressing conditions. Plasma-nitrided devices showed less increase in their noise in the linear operation region than the thermally nitrided devices. This difference in noise behavior is attributed to the nitrogen profile across the HK/Si interface and in the bulk of the HK oxide caused by different nitridation techniques. The dielectric defect profile resultant from different annealing techniques was consistent with the spectral form of the observed drain-voltage LFN.