Shinichi Ishibashi

Process development of 6-in EUV mask with TaBN absorber

6-inch EUV masks consisting of Mo/Si multilayers and patterned CrX buffer and TaBN absorber layers have recently been developed and evaluated. Mo/Si multilayers with a relatively high EUV reflectivity of 66 percent and an excellent uniformity were obtained on the polished ULE substrates by an ion beam sputtering method. The multilayers showed high durability to the acid abased cleaning and baking at 150 degrees C used in the conventional mask-making process. The Cr based film was optimized as a repair buffer to obtain a high reflectivity of 52 percent at 257 nm and low stress within 100 MPa. TaBN absorbers with a low reflectivity were obtained by optimizing the film compositions, which resulted in a high image contrast to the multilayer for DUV inspection. An EUV contrast level of 99 percent was achieved for a thinner, 100-nm thick absorber stack. Using the optimized mask process, EUV mask with patterns of 180-nm width were successfully obtained, without a significant drop in EUV reflectivity.