Comparison of Methods Characterizing Time Dependent Dielectric Breakdown in Thin Oxide and Oxide-Nitride-Oxide Layers

The results of constant voltage stress and constant injection current techniques are discussed concerning dielectric lifetimes and failure modes of a thermal oxide layer and a ONO-layer. The constant voltage stress shows that the ONO-layer has a prolonged lifetime and a lower amount of early failures compared to a single oxide layer, even though the charge to breakdown of the ONO-layer is smaller than that of the thermal oxide. From constant current stress experiments lifetimes for different dielectrics e.g. in a DRAM application can only be inferred in the case of similar electric fields.