Increasing threshold voltage variation due to random telegraph noise in FETs as gate lengths scale to 20 nm

The statistical distribution of random telegraph noise (RTN) has been measured and characterized in scaled PDSOI FETs down to 20 nm gate length. Statistical analysis of RTN in >15 thousand nFETs shows temperature-independent long-tailed non-Gaussian distributions of noise amplitudes. Treated as equivalent threshold voltage variation (DeltaV_th), the RTN distributions appear log-normal, with the DeltaV_th reaching >70 mV for the smalles devices. Because of the log-normal distribution, it appears that RTN V_th variations may exceed random dopant fluctuation (RDF) V_th variations at the ~3 sigma level in the 22 nm generation, making RTN a very serious threat to SRAM stability at 22 nm and beyond.