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In this paper, the characteristic variability in gate-all-around (GAA) silicon nanowire MOSFETs (SNWTs) is experimentally studied. Variation sources in SNWTs are extracted for the first time, taking into account the strongly-confined geometry induced quantum effect, quasi-ballistic effects, as well as the parasitic quantum resistance at the interface of 1D channel and 3D wide S/D regions. The measured results show that with suppressed random dopant fluctuations (RDF) in the intrinsic channel, variations in radius (R) and metal-gate work function (WF) of SNWTs dominate both the threshold voltage and on-current fluctuations, and line-edge-roughness (LER) shows minor impact. The influence of the SNWT variation sources on SRAM performance is estimated and compared with planar devices. In addition to process variation, variation induced by random telegraph signal (RTS) noise in SNWTs is also investigated for the evaluation of SRAM cell operating window. Design optimization guidelines are given based on the SRAM variation analyzed results.
Electron Devices Meeting (IEDM), 2009 IEEE International
Date of Conference: 7-9 Dec. 2009