Abstract

Due to its high X-ray reflectance (~60%) for wavelengths longer than the Si-L absorption edge near 125 Å, the Mo/Si X-ray multilayer (XML) system is now used in a diverse range of advanced applications, including soft X-ray projection lithography and X-ray astronomy. Consequently, the stability and the structural and optical properties of this system have been extensively studied [1-7]. High resolution transmission electron microscopy (HRTEM) of sputter-deposited Mo/Si XMLs reveals that the Mo layers are polycrystalline, the Si layers amorphous, and the interface region composed of an amorphous mixture of Mo and Si. Further investigations have indicated that this interlayer material is, in fact, amorphous MoSi₂. Thermal anneal studies have revealed the absence of solid-state amorphization, in spite of the presence of the amorphous alloy interfacial layers. Instead, the amorphous interlayers crystallize, and growth of the crystalline product, MoSi₂ proceeds in the temperature range 275-550°C. At higher temperatures (600°C), the Mo₅Si₃ phase appears as well. However, at lower temperatures (<200°C), no structural or optical changes have thus far been reported.

© 1992 Optical Society of America