Plasma FIB Delayering and Nanoprobing with EBIRCH for Localizing Metal Shorts in DRAM

Abstract

This paper demonstrates how to localize metal-to-metal short failures in DRAM, where defects can occur over a large area including the aluminum layer, by using the means of mechanical grinding, plasma FIB delayering, and EBIRCH (Electron Beam Induced Resistance Change). Our experiments show that a uniform mechanical grinding of an aluminum layer, and DX PFIB delayering, results in a high quality planer surface in the target layer and site, as the slope created during the grinding is compensated by PFIB delayering. This approach has advantages that are conducive to EBIRCH analysis. First, the target layer can be prepared at any given location (site-free). Second, the defective layer can be delayered to a desired depth without damage (layer-free). Last, after delayering, the surface of the device becomes evenly flat enough to allow the electron beam to evenly penetrate the device for EBIRCH analysis (higher-flatness).With the use of more advanced device preparation methods, EBIRCH analysis has a higher chance of successfully localizing metal line/via shorts even in a large region, which includes the aluminum layer.