Abstract

Mo/Si multilayers (ML's) are attractive for x-ray optics due to the relatively high associated reflectivity. However, the reflectivity is known to decrease with the formation of diffuse interlayer regions resulting from interdiffusion at the Mo-Si interfaces [1-2]. Most of the previous studies have reported interdiffusion coefficients [1-5] and effective activation energies [2-4] over a range of temperature assuming that the interdiffusion coefficient is invariant with annealing time. At temperatures of 560-580 °C, hexagonal molybdenum-disilicide (h-MoSi₂) grows with a square-root time dependence at the Mo-Si interface [6]. This suggests diffusion-limited growth with a time-invariant interdiffusion coefficient. However, at temperatures of 300-400 °C, the interlayer structure is known to change with annealing time from amorphous to crystalline [1-3], suggesting the possibility that the rate-controlling mechanism(s) for interdiffusion may also change with annealing time and/or temperature. Therefore, it is the objective of this study to perform a series of annealing treatments of Mo/Si ML's at temperatures lower than those previously reported to determine the Mo-Si interdiffusion kinetics as a function of time.

© 1992 Optical Society of America