Investigation of the Impact of Random Dopant Fluctuation on Static Noise Margin of 22nm SRAM

In this paper, the impact of RDF on the static noise margin (SNM) and read current margin (SINM) of a prototype 22nm 6T SRAM was investigated using TCAD modeling. Individual device statistics of threshold voltages (Vt) and transport related parameters were first extracted for NFETs and PFETs. SNM and SINM characteristics of the corresponding SRAM cells were then analyzed. Two methods to emulate the impact of RDF were simulated - modulating gate work function, and uniform scaling of the continuum dopant distribution. Compared to RDF devices, both methods underestimated Vt and SNM variations.