@User do not use 'um' in dimensions as these are already scaled down (.option scale=1e-6 is implied in the model file) , minimum length for transistors is L=0.15, also set W=0.42 (the minimum). One more thing, the transistors are implemented as subcircuits, so rename M1 and M2 to XM1 and XM2. Also the nets of M2 are in the wrong order, it's better to have output node connected to drain terminal and source to ground. This is not mandatory for symmetrical devices however it's good practice. --> XM2 out in 0 0 sky130_fd_pr__nfet_01v8 w=0.42 l=0.15 m=1 mult=1

Yeah thanks@stefan it worked.