Reduction of thermal damage in ultrathin gate oxides after intrinsic dielectric breakdown

We have compared the thermal damage in ultrathin gate SiO2 layers of 5.6 an d 3 nm thickness after intrinsic dielectric breakdown due to constant volta ge Fowler-Nordheim stress. The power dissipated through the metal-oxide-sem iconductor capacitor during the breakdown transient, measured with high tim e resolution, strongly decreases with oxide thickness. This is reflected in a noticeable reduction of the thermal damage found in the structure after breakdown. The effect can be explained as the consequence of the lower amou nt of defects present in the oxide at the breakdown instant and of the occu rrence of a softer breakdown in the initial spot. The present data allow us to estimate the power threshold at the boundary between soft and hard brea kdown, and they are compared to numerical simulations of heat flow. (C) 200 1 American Institute of Physics.