Power-aware 65 nm node CMOS technology using variable VDD and back-bias control with reliability consideration for back-bias mode

We have developed a power-aware CMOS technology featuring variable V_DD and back-bias control. Three typical operation modes are defined: high-speed mode (V_DD = 1.2V, V_B = 0V), nominal mode (V_DD = 0.9V, V_B = -0.5V) and power-save mode (V_DD = 0.6V, V_B = -2.0V). Compared with nominal mode, one and a half order of magnitude reduction of standby leakage current is achieved with power-save mode, while 75% higher drivability is achieved with high-speed mode. Device reliability for back-bias condition was also investigated. With higher back-bias, NBT (Negative Bias Temperature) degradation for pFET is enhanced especially in the case of thinner gate oxide. From activation energy, we believe the dominant mechanism is SHH (Substrate Hot-Hole) injection. Reduced V_DD at standby mode drastically alleviates this degradation caused by NBT stress and SHH injection. With appropriate V_DD and V_B combination, power-aware 65nm CMOS with sufficient reliability can be achieved.