TCAD based Modeling of Sub-surface Leakage in Short Channel Bulk MOSFETs

Aggressive scaling of the channel length of Bulk MOSFETs manifests in higher sub-surface leakage current, which becomes an increasingly significant component of the OFF-State leakage current. By firstly identifying the sub-surface leakage region as one that manifests in a region away from the electrostatic control of the gate, but, within the source/drain junction depth, while being impacted by the drain voltage, we model the sub-surface leakage current using a non-charge-sheet based approach, which is further simplified as a physics-based semi-analytical model similar to the Shockley equation of an ideal ‘forward-biased’ p-n junction diode. In addition to validating the proposed model, we also show the impact of various structural and electrical parameters, thus demonstrating that the model provides key insights on device behaviour.