Imaging Superjunctions in CoolMOS Devices Using Electron Beam Induced Current

Electron beam induced current (EBIC) measurements were used to produce cross sectional images of superjunctions in CoolMOS™ power transistors. The positions of the pn -junctions were determined by EBIC measurements. Knowing the exact locations of the pn -junctions is important for CoolMOS™ since it relies on the principle of charge compensation. For charge compensation, the donors in the n -doped regions must be compensated by an equal amount of acceptors in the p -doped regions. We show that EBIC can provide valuable input for process tuning and process simulations. This will enable the use of smaller dimensions and higher doping levels resulting in a lower on-state resistance.