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

Abstract

Solid phase reaction behavior of polycrystalline and amorphous alloys of MoNi_x (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).