Photo mask including pre-alignment keys and photolithography apparatus performing a pre-alignment process for the photo mask

摘要

A photo mask includes a pre-alignment key used in a pre-alignment process performed in a photolithography apparatus. The pre-alignment key includes a pre-alignment pattern including a light transmitting area and a light blocking area surrounding the pre-alignment pattern. The light blocking area includes a plurality of light blocking patterns and a diffraction grating pattern separating the plurality of light blocking patterns from each other.