Evaluation of dry etching and defect repair of EUVL mask absorber layer

EUVL mask process of absorber layer, buffer layer dry etching and defect repair were evaluated. TaGeN and Cr were selected for absorber layer and buffer layer, respectively. These absorber layer and buffer layer were coated on 6025 Qz substrate. Two dry etching processes were evaluated for absorber layer etching. One is CF4 plasma process and the other is Cl2 plasma process. Etch bias uniformity, selectivity, cross section profile and resist damage were evaluated for each process. Disadvantage of CF4 plasma process is low resist selectivity and Cl2 plasma process is low Cr selectivity. CF4 plasma process caused small absorber layer damage on isolate line and Cl2 plasma process caused Cr buffer layer damage. To minimize these damages overetch time was evaluated. Buffer layer process was also evaluated. Buffer layer process causes capping layer damage. Therefore, etching time was optimized. FIB-GAE and AFM machining were applied for absorber layer repair test. XeF2 gas was used for FIB-GAE. Good selectivity between absorber layer and buffer layer was obtained using XeF2 gas. However, XeF2 gas causes side etching of TaGeN layer. AFM machining repair technique was demonstrated for TaGeN layer repair.