Quantitative Analysis of Tunneling Current through Ultrathin Gate Oxides

Abstract

The tunneling current through ultrathin (3.0-6.0 nm) gate oxides has been measured as a function of the voltage across SiO 2 , V OX , and compared with results of existing theories utilizing the WKB approximation. The electron effective mass in the Fowler-Nordheim tunneling region ( V OX ≥3.25 V) is obtained to be (0.34±0.04) m 0 and that in the direct tunneling region ( V OX <3.25 V) is (0.29±0.02) m 0 . It is also shown that the charge-to-breakdown for electron injection from n + poly-Si gates is not significantly degraded by decreasing the oxide thickness and is even dramatically improved for the case of a 3.0 nm-thick gate oxide.