Effective Carbon Contaminant Cleaning Condition Using Ozone Dissolved Water and Megasonic for Ru-Capped Extreme Ultraviolet Lithography Mask

Abstract

A possible candidate for carbon contaminant removal in Ru-capped extreme ultraviolet lithography (EUVL) mask is ozone dissolved water (DIO3). However, the use of DIO3 leaves reflectivity loss and serious surface damages on Ru capping layer caused by its high oxidation potential. In this study, an optimum DIO3 cleaning condition for effective carbon cleaning without surface damage was investigated both theoretically and experimentally. The effect of feed gases such as O-2, CO2, and N-2 of various concentrations were tried during DIO3 generation for oxidation stability on Ru capping layer and N-2 added 15 ppm DIO3 was found to be the best condition. However carbon contaminant was ineffectively removed at this condition. Thus megasonic is irradiated during DIO3 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. (C) 2012 The Japan Society of Applied Physics