The impact of exposure induced refractive index changes of photoresists on the photolithographic process
In many commercial and non-commercial photoresists the real and the imaginary parts of the refractive index are changed during exposure. Using a finite-difference beam-propagation algorithm, we analyze the impact of these nonlinear optical effects on the photolithographic process. Changes of the real part of the refractive index have a considerable impact on dose latitudes, side-walls, swing-curves, iso-dense bias and other process parameters. These effects become more dominant as the thickness of the resist layer increases.