Specific site cross-sectional sample preparation using focused ion beam for transmission electron microscopy

Abstract

Sample preparation using focused ion beam (FIB) for transmission Electron Microscopy (TEM) analysis was reviewed. Improving the quality of FIB prepared TEM sample has been an issue in the past. A specific site cross-sectional sample preparation method has been developed using FIB milling for TEM characterization of integrated circuits (ICs). Approach of front side and back side milling has been applied to thin the semiconductor samples for electron transparency. Back side milling has been applied for the first time in our TEM sample preparation using FIB milling. Proper tilting of the stage and use of low beam current are found to be critical for TEM samples quality. Samples prepared during present work are thinner, artifact-free, and of excellent quality for TEM analysis. It is possible to prepare specific site cross-sectional TEM samples of ICs within 2–3 hours using FIB milling. Some examples of specific site cross-sectional TEM analysis of Si based device structures are presented. Final achievable thicknesses of the samples are exemplified from the fact that atomic resolution imaging was possible and microstructure was seen in the tungsten plugs.