Effect of Reverse Body Bias on Current Testing of 0.18 μm Gates

Systematic investigations on defect-free IDDQ in deep submicron CMOS with reversebody bias were performed by SPICE simulation towards an attempt to improveresolution of IDDQ measurement. Effects of reverse body bias on off-state leakage ofscaled CMOS devices and IDDQ of typical CMOS circuit cells were investigated. It wasfound that reverse body bias can effectively reduce defect-free IDDQ of typical 0.18 μmtechnology devices and logic gates while the faulty current is not as much reduced. Thereduction in defect-free IDDQ was enhanced as the device temperature went up anddiminishes as the temperature went down. Further investigation showed that reversebody bias also makes the defect-free IDDQ less sensitive to the input state; therefore, asingle IDDQ current threshold might still be used for IDDQ testing of 0.18 μm CMOS circuits. It was found that there might exist an optimal reverse body bias that minimizedthe defect-free IDDQ current. The optimal reverse bias value decreases as the temperaturewent down and might vary from circuit to circuit, process to process, andtechnology generation to generation