Study of flicker noise and RTN for characterization of gate dielectrics in MOS systems

Low frequency noise is getting increasing attention as dimensions scale down. Ths study of LFN is important because of its appearance as a fundamental limit for scaling, its impact on RF and analog applications but most importantly it can serve as a diagnostic tool for quality and reliability of MOSFETs. The interface between the dielectric and channel is not ideal. Further as newer materials are introduced to propel scaling further, the interface goes far from ideal and it become necessary to characterize them. LFN comprises of 1/f noise and RTN. RTN is seen in devices with low dimensions where the probability of having a single dominant trap is high and is characterized by Lorentzian spectrum in the frequency domain and two level current fluctuations. 1/f is seen in devices when the trap density is high and is understood as the summed up response of several traps. This report deals with exploring LFN as a diagnostic tool for characterizing MOSFETs and tries to explain the theory behind them as well as the experimental results obtained. Measuring RTN is challenging because of line frequency interface (50 Hz and its harmonics). Details of the troubleshooting done and how the setup was fixed are explained. Using the modified setup, RTN measurements were done on RENESAS wafers and analysis was done to correlate it with frequency domain spectrum. A comparison of noise between capped and non-capped wafers were also done. Study of flicker noise in SiGe pMOSFETS are also included in this report which includes flicker comparison between control, Si capped SiGe pMOSFET and non-capped SiGe pMOSFET. Also NBTI correlation of flicker degradation for non-capped SiGe pMOSFET is done.