Gate currents in thin oxide MOSFETs

In nchannel MOSFETs with gate oxides below 20 nm the gate current, as a function of the gate voltage, shows unusual structures which are not observed for thicker oxides. Besides the known negative peak at VG ≈ VD, a negative shoulder at VG ≈ VD/2 and a positive peak at VG < VD/2 appear. It is shown here that the additional structures can be attributed partly to hot electrons injected against the electric field in the pinchoff region and partly to hot holes. Using 2- dimensional MOSFET simulation results as a starting point, all the features of the gate current against VG curves can be described using one single model. Using the gate current calculation, the currents injected into the gate oxide, which are very important to describe the degradation and are not equal to the gate currents, are estimated correctly.