A comparison of FinFET based FPGA LUT designs

Abstract

The FinFET device has gained much traction in recent VLSI designs. In the FinFET device, the conduction channel is vertical, unlike a traditional bulk MOSFET, in which the conduction channel is planar. This yields several benefits, and as a consequence, it is expected that most VLSI designs will utilize FinFETs from the 20nm node and beyond. Despite the fact that several research papers have reported FinFET based circuit and layout realizations for popular circuit blocks, there has been no reported work on the use of FinFETs for Field Programmable Gate Array (FPGA) designs. The key circuit in the FPGA that enables programmability is the n-input Look-up Table (LUT). An n-input LUT can implement any logic function of up to n inputs. In this paper, we present an evaluation of several FPGA LUT designs. We compare these designs from a performance (delay, power, energy) as well as an area perspective. Comparisons are conducted with respect to a bulk based LUT as well. Our results demonstrate that all the FinFET based LUTs exhibit better delays and energy than the bulk based LUT. Based on our comparisons, we have two winning candidate LUTs, one for high performance designs (3X faster than a bulk based LUT) and another for low energy, area constrained designs (83% energy and 58% area compared to a bulk based LUT).