In situ and ex situ measurements of stress evolution in the cobalt-silicon system

Abstract

The biaxial stress in Co thin-films has been investigated in situ by measuring changes in substrate curvature that occurred during deposition and annealing. Films of Co, 35 to 500 nm in thickness, were deposited by UHV magnetron sputtering at room temperature on Si (100) and poly-Si substrates. Results show that during Co deposition the bending force increased linearly with film thickness; a signature of constant stress. In addition, the stress evolution during silicide formation was measured under constant heating rate conditions from room temperature up to 700 °C. The stress-temperature curve was correlated with Co2Si, CoSi, and CoSi2 phase formation using in situ synchrotron X-ray diffraction measurements. The room temperature stress for the CoSi2 phase was found to be ∼0.8 GPa (tensile) in the films deposited on Si (100) and ∼1 GPa (tensile) on the films deposited on poly-Si. The higher tensile stress in the poly-Si sample could be a result of Si grain growth during annealing.