Electrical Conduction and Dielectric Breakdown in Silicon Dioxide Films on Silicon

Abstract

Conduction through films, thermally grown on Si substrates, was found to take place via a Fowler‐Nordheim (F‐N) tunneling mechanism, after an initial transient current associated with trapping of charge, mobile ions, and space charge redistribution has died away. The temperature dependence of the steady‐state F‐N current decreases with increasing applied field and was found to be smaller in magnitude than previously reported. Typical post‐metalization annealing treatments (e.g., 5 min at 500°C in dry N₂) lowers the conductivity of the MOS capacitor structures by two to three orders of magnitude, an effect that can be attributed to the elimination of either traps or fixed charge distributed throughout the oxide. For applied fields larger than 8 MV/cm, a current instability arises which can lead to dielectric breakdown. For a wide range of different electrode materials, the onset of this instability appears to correlate well with the temperature and oxide thickness dependences of breakdown, as observed earlier (10). These findings are discussed in terms of a model which suggests that carriers can be generated and redistributed by collision ionization processes within the oxide.