Thanks a lot for your kindly support.
I use periodic boundary conditions for x and y axis. For z axis, PML with steep angle is selected. My source is a plane wave, in x polarization.
Pillar has a refractive index of 3.5. Substrate is SiO2.
Grating S parameters analysis group is used in 0th order. This setup gives correct answers until a defined value, n=1.64. When I change it as n=1.65, system cannot calculate S parameters.
Below you can see my setup:

Thanks again. Greetings.