In response to your query I would like to present my view. I believe you have raised this query with reference to the annealing of as grown thin films. Usually pre-annealing treatment refers to the minor chemical treatments which is performed on the thin films using mild acids. It's usually done to get rid of the undesirable secondary phases which might have formed on the surface or native oxides.
Sometimes you can heat the films to the temperature which is sufficient enough to sublime the surface impurities. I believe this can be considered as the pre annealing heat treatment and the temperature as pre annealing temperature.