Hot-electron-induced quasibreakdown of thin gate oxides

An oxide-breakdown mode induced by hot-electron injection into an oxide is reported for n-channel metal-oxide-semiconductor field-effect transistors with 6 nm thick gate oxides. The diameter of the current path formed after breakdown was estimated to be less than 10 nm based on spreading-resistance measurements. The measured charge to breakdown was 10(2)-10(4) C/cm(2) in an oxide field of 5-7 MV/cm. This value is much smaller than that extrapolated from the results of Fowler-Nordheim (FN) tunnelling experiments. The charge to breakdown in the hot-electron injection method decreased as the electric field increased in a silicon substrate. This was quite different from the case with FN tunnelling injection, where the oxide held plays a significant role in oxide breakdown. Good correlation between the calculated electron energy in the oxide and the electric field in the-silicon substrate suggests that the difference between hot-electron injection and FN tunnelling can be explained in terms of the average electron energy in the oxide. (C) 1997 American Institute of Physics.