Development of a Method for Resist Removal by Ozone with Acetic Acid Vapor

Abstract

A method of removing the photoresist using ozone gas with acetic acid vapor has been developed. Glass substrates (size mm2) coated with I-line resist were treated under the conditions of substrate temperature, 27-50°C; acetic acid vapor, 2-18 vol %; ozone, 0-9.3 vol % (0-200 g/m3); total gas flow rate, 2 L/min; and gas pressure, 100 kPa. A previous ozone treatment with oversaturated water vapor or sprayed water overcame the limitation of ozone diffusion into the resist by the control of the water film on the resist. In this study, pure acetic acid vapor has been first applied for the resist removal by ozone in order to improve the oxidation rate of the resist, because acetic acid is an inactive solvent in the ozonization, and the solubility of ozone is much higher than water. It was observed that the resist removal rate increased with acetic acid and ozone concentration, and reached at 6 μm/min at which was about six times greater than that of the previous ozone treatment. Metal corrosion of molybdenum and aluminum electrodes was found negligible during the ozone treatment with acetic acid vapor. The mechanism of resist removal without the metal corrosion by ozone with acetic acid vapor is also discussed, based on the solubility of ozone in acetic acid and the corrosion current in ozonized solutions. © 2004 The Electrochemical Society. All rights reserved.