Estimation of the Activation Energy of Resist Removal Using Wet Ozone

Using environmentally friendly wet ozone instead of conventional chemicals, we removed positive-tone novolak resists. In the wet ozone process, resists are decomposed and removed through ozonolysis of the resists and the hydrolysis of the ozonolysis products. It was revealed that the temperature difference (= "wet ozone temperature" - "substrate temperature"), to control water requirements for the hydrolysis strongly influences the resist removal rate. The activation energy of the removal reaction of this process was estimated to be 28.0 kJ/mol. The activation energy is 10 similar to 20 kJ/mol lower than that of the commonly-used ashing process, therefore the resist can be removed at a higher rate and at a lower temperature.