The Groove Profile Formation of Holographic Gratings

Models for predicting the groove profile of metal coated holographic gratings, fabricated in positive photoresist, are studied. Development is assumed to be an etching process, where the etching is directed perpendicularly to the resist-developer interface. Two methods for metal coating are considered; vacuum evaporation and sputtering, and models that describe the profile formation for these cases are presented. It is noted that even a thin coating has a considerable effect on the profile. The theoretical groove profiles are found to be in good agreement with experimental profiles, obtained from SEM photographs of fabricated gratings.