CFET RMG Dual Work Function Metal Patterning with Sacrificial Layer for Nanosheets Pinch-Off

We reported the process flow and challenges of dual work function metal patterning between different work function metal thicknesses and gate lengths to monolithic Complementary FET. To resolve the dilemma of spin-on-carbon hard mask fill and nanosheet pinch-off, we propose integrating sacrificial gap-closure layers and isotropic etches to dual work function metal patterning. We prove that the sacrificial layers can be removed with high selectivity to work function metal in wet etch chemistry. We report the controllable wet etch rate of the sacrificial layers by concentrations and temperatures. Finally, we first demonstrate dual work function metal patterning with a sacrificial layer and isotropic etch step by step on a monolithic Complementary FET test vehicle.