A new circuit technique for reduced leakage current in Deep Submicron CMOS technologies

Abstract

Modern CMOS processes in the Deep Submicron regime are restricted to supply voltages below 2 volts and further to account for the transistors' field strength limitations and to reduce the power per logic gate. To maintain the high switching performance, the threshold voltage must be scaled according with the supply voltage. However, this leads to an increased subthreshold current of the transistors in standby mode (VGS=0). Another source of leakage is gate current, which becomes significant for gate oxides of 3nm and below. We propose a Self-Biasing Virtual Rails (SBVR) - CMOS technique which acts like an adaptive local supply voltage in case of standby mode. Most important sources of leakage currents are reduced by this technique. Moreover, SBVR-CMOS is capable of conserving stored information in sleep mode, which is vital for memory circuits. Memories are exposed to radiation causing soft errors. This well-known problem becomes even worse in standby mode of typical SRAMs, that have low driving performance to withstand alpha particle hits. In this paper, a 16-transistor SRAM cell is proposed, which combines the advantage of extremely low leakage currents with a very high soft error stability.