Back to the Future: Digital Circuit Design in the FinFET Era
It has been almost a decade since FinFET devices were introduced to full production; they allowed scaling below 20nm, thus helping to extend Moore’s law by a precious decade with another decade likely in the future when scaling to 5nm and below. Due to superior electrical parameters and unique structure, these 3-D transistors offer significant performance improvements and power reduction compared to planar CMOS devices. As we are entering into the sub-10nm era, FinFETs have become dominant in most of the high-end products; as the transition from planar to FinFET technologies is still ongoing, it is important for digital circuit designers to understand the challenges and opportunities brought in by the new technology characteristics. In this paper, we study these aspects from the device to the circuit level, and we make detailed comparisons across multiple technology nodes ranging from conventional bulk to advanced planar technology nodes such as Fully Depleted Silicon-on-Insulator (FDSOI), to FinFETs. In the simulations we used both state-of-art industry-standard models for current nodes, and also predictive models for future nodes. Our study shows that besides the performance and power benefits, FinFET devices show significant reduction of short-channel effects and extremely low leakage, and many of the electrical characteristics are close to ideal as in old long channel technology nodes; FinFETs seem to have put scaling back on track! However, the combination of the new device structures, double/multi-patterning, many more complex rules, and unique thermal/reliability behaviors are creating new technical challenges. Moving forward, FinFETs still offer a bright future and are an indispensable technology for a wide range of applications from high-end performance-critical computing to energy-constraint mobile applications and smart Internet-of-Things (IoT) devices.