In-situ EBIC measurements of IGBT during device turn-on

A simple method for the in-situ examination of device turn-on in an Insulated Gate Bipolar Transistor (IGBT) is presented. A Ga
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Focused Ion Beam (FIB) was used to mill away a wedge-shaped section from the material so as to leave the exposed devices operable by the surface gate and emitter contact pads. Through this window, a series of nanoprobing-based measurements were undertaken. Sensitive, Electron Beam Induced Current (EBIC) measurements strongly delineated both of the p/n junctions in the exposed surface, both those between the N+ emitter and the P-well or body, and between this P-body and N-drift region. Next, the gate voltages were varied and a series of EBIC images were taken of the body/drift depletion zone. Quantitative plots of the same gave an indication of when the insulated gate portion of the device turned on. Finally, a follow-up experiment showed the effect of applied bias on Active Voltage Contrast (AVC) of the junction. The results point to a method for examination of junctions and their behavior under gate bias with very little sample preparation. The results also ease some concerns about the use of GaFIB in sample prep for junction examination in failure analysis, given the detailed work that was possible.