Novel IC designs with 32 nm Independent-Gate FinFET

Abstract

The semiconductor industry is confronted with serious challenges as the push continues toward scaling transistors into the 22-nm technology node and beyond. The most important among these challenges is the diminishing gate control over the channel, which manifests itself in the form of the increased short-channel effects (SCE) and leakage currents. One approach to countering these effects is introducing new materials for improved performance, either into the gate stack, the channel, or the source/drain extension regions. However, even with the introduction of these new materials, leakage will continue to be a serious problem. Hence, alter device architecture are being explored which processes inherently better robustness to SCE. Among this alternatives, multiple-gate FETs, also known as FinFET or gate wrap-around FETs, are emerging as promising candidates. In a FinFET, the gate wraps around a thin slice of silicon, also known as a “fin”, and current flows along the top and side surface of the fin. This wrap-around nature of the gate enhances the gate control over the channel, thus reducing the SCE and leakage currents. Furthermore, fabrication of FinFET is compatible with that of conventional CMOS, thus making possible very rapid deployment to manufacturing. From a circuit-design perspective, FinFET provides IC designer with more options to innovate. For instance, FinFET device can directly substitute the CMOS in the existing applications by using the shorted-gate FinFET in which two FinFET gates are tied together. Additionally, the low-power mode of FinFET device in which the back-gate bias is tied to a reverse-bias voltage is often employed in the low-power design in that it can reduce subthreshold leakage. Last but not least, the independent-gate FinFET emerges as an interesting device so that IC designers have a variety of choices to flexibly use the two gates of FinFET for difference tasks. In this thesis, independent-gate FinFET are our concern with two designs being included. The first work presents a novel methodology for IC speed-up in 32nm FinFET. By taking advantage of independently controlling two gates of IG-FinFET, a boosting structures is developed to improve the signal propagation on interconnect significantly. In the second work, a digital voltage sensor design is illustrated. Based on the operation of a p-type FinFET in low-power mode and independent-gate mode, a new technique for designing a controllable delay element (CDE) with high linearity is presented. Then, we develop a 9-bit digital voltage sensor with a voltage range of 0.7 – 1.1 V and 50 mV resolution. The proposed voltage sensor can operate with ultra-low power, a wide voltage range, and fairly high frequency.