Identification of MOS Gate Dielectric Breakdown Spot Using High Selectivity Cl Radical Etching Technique

Abstract

We have developed a simple method for identifying dielectric breakdown spots in gate oxides by using high selectivity Cl radical etching. This method is based on the phenomenon that Cl radicals do not penetrate . They can etch the Si substrate through the breakdown spot which acts as the etching path, namely, the current leakage path. During over‐etching of the poly‐Si gate electrode, a cavelike etched region in the Si substrate appeared under the breakdown spot of the gate oxide. This breakdown spot could be found by focusing the optics on the gate oxide located at a center on the etched region. We confirmed the local structure of the gate oxide which converted to crystallized Si due to intrinsic dielectric breakdown using transmission electron microscopy and energy dispersive x‐ray spectroscopy. Cl radicals can etch the breakdown spot such as part of the crystallized Si in the gate oxide produced by intrinsic dielectric breakdown, and then etch a Si substrate under the breakdown spot.