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 20nm 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 (ΔV
th
), the RTN distributions appear log-normal, with the ΔV
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.