We present detailed calculations for the Casimir force between a plane and a
nanostructured surface at finite temperature in the framework of the scattering
theory. We then study numerically the effect of finite temperature as a
function of the grating parameters and the separation distance. We also infer
non-trivial geometrical effects on the Casimir interaction via a comparison
with the proximity force approximation. Finally, we compare our calculations
with data from experiments performed with nanostructured surfaces