Izumi Oya

Development of a Photoresist Removal Method Using Ozone Gas with Water Vapor for LCD Manufacturing

A photoresist removal method for liquid crystal display manufacturing, using highly concentrated ozone gas and water vapor, has been developed. This method overcomes limitations of conventional ozone processing for resist removal, and obtains a resist removal rate over 1 μm/min at substrate temperatures lower than 100°C. In our experiment, ozone gas was bubbled into water, and water vapor concentration in the gas phase was controlled by the water temperature (T w ). The influence of treatment parameters, such as substrate temperature (T s ), water vapor concentration, and residence time (τ), on the removal rate has been experimentally examined. The treatments were performed at T, = 25-83°C, T w = 27-92.5°C, T = 0.5-2 min, ozone concentration [O 3 ] 0 = 4.2-10.7 vol % (90-230 g/m 3 ), gas flow rate 1-12.5 slm, and total pressure 100 kPa. The observed removal rate was 1.4 μm/min for a sample with a dry etching treatment at T s = 83°C, T w = 90°C, and [O 3 ] = 10.7 vol %. It was also shown that the difference between the water and the substrate temperatures, T w - T s , was a critical parameter for determining the removal rate. The removal rate in this process is more than ten times greater than that of the conventional ozone processing, such as ozone gas ashing and ozonized water treatment. A higher removal rate was realized by optimizing the amount of condensed water with respect to a resist oxidation rate and the diffusion rate of ozone into the resist in the water.