Two Competing Limiters in MOSFETs Scaling: Neutral Defects and S/D Plasmons

Abstract

On the industrial HKMG silicon MOSFETs with different channel lengths L down to 14 nm, we present high-resolution TEM cross-section images to highlight interstitial defects in the channel near the source and drain. To examine such neutral defects, we devise a new 2D microscopic scattering model and use it to extract the apparent neutral defects density from the measured inversion-layer effective mobility. We find that for L > 25 nm, the extracted defect densities are independent of temperature, as expected. However, for L < 25 nm, the plasmons in the highly doped source and drain regions prevail over neutral defects. Further measured degradation in the virtual source velocity at saturation matches that of full Coulomb Monte Carlo simulation, for the first time experimentally confirming S/D plasmons as the dominant mechanism for L < 25 nm.