Optimization of DIO 3with megasonic cleaning of Ru capped EUVL mask for effective carbon contaminant removal

Abstract

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. ©The Electrochemical Society.