Comment by itishappy

Photoresist too. XRays are really good at passing through matter, which is a bit of a problem when the whole goal is for them to be absorbed by a 100 nanometer thick film. They tend to ionize stuff, which is actually a mechanism for resist development, but XRay energies are high enough that the reactions become less predictable. They can knock electrons into neighboring resist regions or even knock them out of the material altogether.