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Cleaning process for x-ray masks

A cleaning process for x-ray mask fabrication has been developed that virtually eliminates mask defects. To introduce the wet-cleaning process into the x-ray mask fabrication process, a new mask cleaning system is manufactured to prevent the mask membrane from breaking due to liquid pressure. Because Ta is chemically stable to a strong acid, we employ a wet-cleaning process using a strong acid such as H2S04 + H202 in order to eliminate contamination that occurs in the x-ray mask fabrication process, such as back-etching of the substrate. and Ta pattern etching. Most metallic and organic defects were eliminated by the strong acid wet-cleaning. By introducing this cleaning process, occurrence of mask defects was drastically reduced: the defect density was reduced to less than 5 defects/cm2 The patterns with widths below 0.2 μm were not damaged by acid cleaning, and pattern positioning distortion did not occur.