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

Abstract

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