Improvement in radiation stability of SiN X-ray mask membranes

The synchrotron radiation (SR) stability of silicon nitride (SiN) X-ray mask membranes was successfully improved by low-pressure chemical vapor deposition at a growth temperature of 1000degC. The transmission of the SiN membrane formed at 1000degC exceeded 90% at about 633 nm even after SR absorption with a dose of about 100 MJ/cm3, although those of membranes formed at 800 and 900degC decreased to below 85% after the same SR absorption. In addition, SR-induced pattern displacements for the SiN membrane formed at 1000degC were suppressed to σx = 11 nm and σy = 10 nm with a dose of 20 MJ/cm3. The N/Si atomic ratio increased, and the H and O concentrations in the SiN decreased with the increase of the growth temperature. The increase ratio of the spin density before and after the SR absorption decreased with the increase of the growth temperature. (author)