Photoresist
Beginner
A light-sensitive coating. Where light hits it, it changes so it can be washed away, leaving a stencil on the wafer.
Novice
A polymer film spun onto the wafer before each lithography step. After exposure through a mask and development, the remaining resist protects what’s under it from the following etch or implant, then is stripped.
Expert
Deep-UV and EUV resists are chemically amplified: exposure turns a photo-acid generator into acid, which during the post-exposure bake catalyzes many deprotection reactions. Acid diffusion and photon counts set a floor on line-edge roughness.