FIB-CVD technology for EUV mask repair

In this paper, we will report on the cleaning process durability and light shielding capability of FIB- and EB-CVD (Chemical Vapor Deposition) films which, are applied to repair clear defects on EUV mask. We evaluated tungsten containing, and silicon containing precursors in addition to carbon based precursor. For the conventional photomasks, the carbon based precursor is applied for repairing the clear defects because the reconstructed patterns by the carbon based precursor have excellent printability. However, under the condition of EUV lithography, the optical property of carbon deposited film is quite different. From the stand point of beam, FIB-CVD films showed better cleaning process durability and light shielding capability than EB-CVD film did. These differences are attributed to chemical components of the CVD films, especially with the tungsten based FIB-CVD film that contains 44 atomic % of tungsten and 24 atomic % of gallium. The tungsten based FIB-CVD film showed no loss of film thickness after dry cleaning, and the calculation showed that 56nmt was sufficient for repairing clear defects on EUV mask with 51nmt of absorber layer. On the other hand, carbon based FIB-CVD film suffered considerable loss in the film thickness and needed more than 180nm.