Investigation of 3D photoresist profile effect in self-aligned patterning through virtual fabrication

The effects of photoresist sidewall profile and LER on two representative integration schemes were studied through 3D virtual fabrication: Front-End of Line (FEOL) Fin formation and Back-End of Line (BEOL) Metal line definition. Both of these processes use self-aligned double patterning (SADP) in pattern definition, and affect the circuit performance through MOSFET channel shape and parasitic capacitance respectively. In both cases we imposed LER and sidewall roughness on the photoresist that defines the mandrel at the initial step of the SADP flow using SEMulator3D. The LER followed a Gaussian correlation function for a number of amplitude and correlation length values. The sidewall profile emulated the bulb-shaped pattern that is reported in experimental works. The taper angle and roughness amplitude of this shape were varied to isolate its components. In each of these cases, we have found direct evidence of resist sidewall profile impact on variability degradation in CD and electrical performance. Special care should be placed on controlling resist profile through optimization of exposure and development schemes.