Sample Preparation Delayering and Cross-sectioning for FA
Sample preparation is a key activity in material and failure analysis. In order to image small structures or defects it is often necessary to remove excess material or layers hiding the feature of interest. Integrated circuits are fabricated by superimposing several layers of alternating conductor and dielectric thin films. Removing selected layers to isolate a structure is called delayering. It can be accomplished by chemical etching using liquid or plasma chemistry, or by mechanical means, by polishing off each unwanted layer. In the preparation of cross-section samples, the entire module is encapsulated in rigid epoxy. It is then lapped and polished from the direction that will render the most beneficial direct view of an internal slice of the sample. Slices are vertical (cross-sections) at any location and orientation. The exposed surface is then inspected and significant features are imaged. They can then, if required, be further studied using other methods of physical analysis.