Planar deprocessing is a vital failure analysis technique for semiconductor devices. The basic concept is to expose an area of interest (AOI) by removing unnecessary material while maintaining planarity and surface evenness. Finger deprocessing is a widely used material removal technique, particularly for fin field-effect transistors (FinFETs). Here, success depends on certain factors, one of which is the location of the AOI. If the AOI is near the edge of the chip, finger deprocessing can be very difficult because material removal rates are much higher there than at the center of the chip. Plasma focused ion beam (PFIB) planar deprocessing is the preferred solution in such cases, but many labs cannot afford a PFIB system. To address this challenge, a sample preparation method has been developed that uses dummy chips to effectively eliminate edges. With dummy chips placed edge-to-edge with test chips, planar deprocessing can be achieved using conventional finger deprocessing techniques. This paper describes the newly developed method, step by step, and presents two examples demonstrating its use.

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