Effect of electronic corrections on the thickness dependence of thin oxide reliability

The thickness dependence of constant voltage lifetime tests for thin oxides in the range of 50-125 Å show an apparent factor of 100 enhancement in the lifetime of 50 Å oxides relative to the 125 Å oxides at a fixed electric field. However, when corrections are made for the distribution of electrons at the silicon interface, including depletion in the silicon and quantum-mechanical screening effects, then this apparent enhancement is reduced and all oxides have similar lifetimes at a fixed field. This rescaling of oxide reliability demonstrates the importance of accurate determination of the electric field and oxide voltage in thin oxides, and that oxide reliability is not significantly affected by thickness down to 50 Å, depending only on field. We compare different techniques for determining the effective thickness using current-voltage or capacitance-voltage curves. We show that accurate estimates of the electric field can be obtained from integration of the capacitance-voltage relation of the capacitor. When electric fields are calculated using C-V curves, a consistent set of extrapolation parameters can be obtained for all thicknesses