Optimization of DIO_3 with Megasonic Cleaning of Ru Capped EUVL Mask for Effective Carbon Contaminant Removal

摘要

A possible candidate for carbon contaminant removal in Ru capped EUVL mask is ozone dissolved water (DIO_3). However, the use of DIO_3 leaves reflectivity loss and serious surface damages on Ru capping layer caused by its high oxidation potential. In this study, an optimum DIO_3 cleaning condition for effective carbon cleaning without surface damage was investigated both theoretically and experimentally. The effect of additive gases such as O_2, CO_2 and N_2 of various concentrations were tried during DIO_3 generation for oxidation stability on Ru capping layer and N_2 added 15 ppm DIO_3 was found to be the best condition. However carbon contaminant was ineffectively removed at this condition. Thus megasonic is irradiated during DIO_3 process and the results show that carbon is not only completely removed in a shorter time but also lower reflectivity loss was accomplished with minimal increase in the surface roughness.