Nano-cmos Scaling Problems and Implications 1.1 Design Methodology in the Nano-cmos Era

As process technology scales beyond 100-nm feature sizes, for functional and high-yielding silicon the traditional design approach needs to be modified to cope with the increased process variation, interconnect processing difficulties, and other newly exacerbated physical effects. The scaling of gate oxide (Figure 1.1) in the nano-CMOS regime results in a significant increase in gate direct tunneling current. Subthreshold leakage and gate direct tunneling current (Figure 1.2) are no longer second-order effects [1,15]. The effect of gate-induced drain leakage (GIDL) will be felt in designs, such as DRAM (Chapter 7) and low-power SRAM (Chapter 9), where the gate voltage is driven negative with respect to the source [15]. If these effects are not taken care of, the result will be a nonfunctional SRAM, DRAM, or any other circuit that uses this technique to reduce subthreshold leakage. In some cases even wide muxes and flip-flops may be affected. Subthreshold leakage and gate current are not the only issues that we have to deal with at a functional level, but also the power management of chips for high-performance circuits such as microprocessors, digital signal processors, and graphics processing units. Power management is also a challenge in mobile applications. Furthermore, optical lithography will be stretched to the limit even when enhanced resolution extension technologies (RETs) are employed. These techniques