VₜTuning of Split-Gate GeSi Nanosheet CFETs With Dual Work Function Metals

A novel device integration scheme for dual-work-function-metal split-gate complementary FETs (CFETs) is demonstrated. Multiple p/n junctions are used to electrically isolate the vertically stacked transistors. The effective work function (EWF) of WNxCy is modulated by the N2/H2 flow ratio during the plasma-enhanced atomic layer deposition (PEALD) process. A ~10-nm-thick WNxCy layer enables ${V}_{\text {TP}}$ (threshold voltage of pFETs) tunability up to 500 mV, while TiN is used as work function metal (WFM) for nFETs. The dual-WFM split-gate architecture achieves well-balanced threshold voltages, with a $\vert {V}_{\text {TP}}\vert $ / $\vert {V}_{\text {TN}}\vert $ ratio of 0.93. Furthermore, the CFET inverter with dual WFMs and split gate reaches a record-high voltage gain of 61 V/V among reported monolithic nanosheet CFETs.