A Novel Cleaning Approach to Remove the Carbon Contaminant from Ru Surface of EUV Mask

Abstract

The carbon contamination on extreme ultraviolet (EUV) mask surface is known to lose its reflectivity and change the critical dimension. Conventional cleaning methods such as SPM and UV/O3 cleaning are widely used for the removal of organic contaminants but can cause surface damages on EUV mask such as surface oxidation and etching of absorber pattern. In this study, we proposed to remove carbon contaminant using quaternary ammonium hydroxides and an organic solvent mixture solution. This study investigated the effect of the cleaning solution on the hydrocarbon film removal by using four kinds of quaternary ammonium hydroxides as alkaline chemical and Dimethyl Sulfoxide (DMSO) and tetrahydrofuran (THF) organic solvents as polar aprotic solvents. The hydrocarbon film was effectively removed from Ru surface in the mixture of tetrabutylammonium hydroxide (TBAH) and THF. When DMSO was used with TBAH solution, the hydrocarbon film was also completely removed at a longer process time than THF with TBAH solution.