UV impact on the optical properties of thin films of positive tone chemically amplified resist

Chemically amplified photo resist are blend materials whose main compounds are a polymer matrix and an added photo acid generator. Lithography processes that allow imaging patterns in a CAR resist films consist in exposing at first the film to UV light and then to post-bake the film in order to initiate a chemical reaction that induces a local solubility switch of the resist. Sensitivity of the resist is measured by monitoring the UV dose needed to induce the proper solubility switch. For positive tone resist, the efficiency of the photolysis of the PAG to an acid and the deprotection kinetic during the post-exposure bake directly govern the resist sensitivity. This article deals with measurements of the PAG photolysis efficiency by real time spectroscopic ellipsometry. C Dill parameter of 193 nm photoresists is then measured for various film thicknesses and PAG loading.