Solid phase reaction of molybdenum-nickel alloy thin films with silicon

Abstract

Solid phase reaction behavior of polycrystalline and amorphous alloys of MoNix (x=12, 20, and 88) with silicon in the temperature range 500–700 °C has been studied by glancing angle x-ray diffraction and Auger electron spectroscopy techniques. Two types of reaction mechanisms are observed in these alloy/silicon reactions and both are controlled by the composition of the refractory metal component. In molybdenum-rich polycrystalline alloy (Mo88Ni12) the reaction at 500 °C occurs due to out-diffusion of nickel from the alloy, while at 550 °C the reaction between the alloy and silicon mainly occurs due to in-diffusion of silicon. On the other hand, in nickel-rich alloy (Mo12Ni88), the reaction at 500 °C is dominated by nickel out-diffusion. The amorphous alloy (Mo80Ni20) was found to be stable on silicon up to 500 °C and a reaction at 550 °C occurs due to crystallization followed by out-diffusion of nickel and large amounts of silicon in-diffusion. In all these alloy/silicon reactions, a macroscopic phase separation between MoSi2 and NiSi or NiSi2 is observed and results in a two-layer structure consisting of [MoSi2+NiSi(or NiSi2)]/NiSi (or NiSi2)/Si(100).