Novel Channel-First Fishbone FETs With Symmetrical Threshold Voltages and Balanced Driving Currents Using Single Work Function Metal Process

In this article, one feasible fabrication approach for novel fishbone FETs using the channel-first and single work function metal (sWFM) processes is proposed and investigated by 3-D technical computer-aided design (TCAD) simulations. Through a small modification on the fabrication process of general gate-all-around (GAA) nanosheet FETs (NSFETs), the special fishbone-like channel composed of vertically stacked Si NSs and sandwiched SiGe nano-fins is experimentally demonstrated by the channel-first process. The simulated electrical characteristics show that the width of the nano-fins should be within 5 nm for a better gate control. Unlike traditional NSFETs, symmetrical threshold voltages (
${V}_{\text {th}}\text{s}$
) for n-type and p-type fishbone FETs can be achieved by using a sWFM, and
$\Delta {V}_{\text {th}}$
is optimized by 99.26% compared with that of NSFETs. Meanwhile, it is also found that the SiGe nano-fins contribute more driving current for p-type devices. Therefore, the proposed fishbone FETs with sWFM not only exhibit significantly enhanced driving current but also provide good balance between the performances of n-type and p-type fishbone FETs with a little extra process cost.