Certain Failure Mechanisms in Two-Level Poly-Si Gate Structures - A Transmission Electron Microscopy Study

In order to reveal lower-than-normal voltage oxide breakdown mechanisms in two-level overlapping poly-Si gate structures, we have examined high resolution cross-sections in the transmission electron microscope. It is shown that the gate oxide undercut of polyI prior to the reoxidation step can lead to a significant localized thinning and/or trapped voids in the regrown oxide.