Stress‐free and amorphous Ta4B or Ta8SiB absorbers for x‐ray masks

We have succeeded in obtaining practical x‐ray absorber films, Ta4B and Ta8SiB, using an rf magnetron sputtering method. The internal stress of these films can be controlled precisely within ±1.0×107 N/m2. The stress has thermal stability at 350 °C. The stress is also quite insensitive to the film thickness and substrates used. These excellent stress properties are attributed to the amorphous structure of the film. The amorphous structure also ensures quarter‐micron pattern fabrication. Densities of 15.3 g/cm3 for Ta4B and 15.6 g/cm3 for Ta8SiB are high enough to yield sufficient contrast for x‐ray exposures.