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We directly measured that anisotropic dopant diffusion into the shallow trench isolation (STI) sink was the predominant factor to cause dependence of the threshold voltage (Vth) on the active width along the channel direction (LOD) for the nMOSFETs. We evaluated by Raman spectroscopy and 3-D stress simulation effects of the STI-induced stress variation on the Vth. Moreover, we directly measured that dopant diffusions coupled with point defect, as transient enhanced diffusion, resulted in the carrier profile depending on the LOD. In particular, it was found that the excess point defect in the deep source/drain enhanced the random extension edge roughness and increased intrinsic Vth fluctuation in the narrow-LOD nMOSFET.
Electron Devices Meeting (IEDM), 2009 IEEE International
Date of Conference: 7-9 Dec. 2009