Damage/organic free ozonated DI water cleaning on EUVL Ru capping layer

The adaption of EUVL requires the development of new cleaning method for the removal of new contaminant without surface damage. One of the harsh contaminants is the carbon contamination generated during EUV exposure. This highly dense organic contaminant is hardly removed by conventional SPM solution on Ru capped Mo/Si multilayer. The hopeful candidate for this removal is ozonated water (DIO₃), which is not only well-known strong oxidizer but also environmentally friendly solution. However, this solution might cause some damage to the Ru capping layer mostly depending on its concentration. For these reasons, DIO₃ cleaning solutions, which are generated with various additive gases, were characterized to understand the correlation between DIO₃ concentration and damages on 2.5 nm thick ruthenium (Ru) surface. An optimized DIO₃ generation method and cleaning condition were developed with reduced surface damage. These phenomena were explained by electrochemical reaction.