Probing Long-Range Coulomb Interactions in Nanoscale MOSFETs

Abstract

We have recently experimentally probed long-range Coulomb interactions due to plasmons in polysilicon gate of long-channel (1 mu m) MOSFETs. In this letter, we further probe those due to plasmons in the highly doped source and drain. Test vehicles include four more samples from the same manufacturing process but with small channel lengths (down to 33 nm). I-V's of devices are measured at two drain voltages of 0.05 and 1 V, in a temperature range of 292-380 K. Inverse modeling technique is applied to furnish calibrated doping profiles. The inversion layer electron effective mobility is thereby extracted, showing a decreasing trend with decreasing channel length. Such differences reflect more additional scatterers in the shorter devices. Mobility components limited by these additional scatterers are assessed using Matthiessen's rule. From the extracted temperature dependencies, we infer that the strength of source/drain plasmons increases with decreasing channel length. The errors of Matthiessen's rule are adequately dealt with. Corroborative evidence is given as well.