Growth characteristics of Mn silicate barrier layers on SiO2

Synchrotron radiation photoelectron spectroscopy (SRPES) is used to investigate the in-situ formation of ultra thin Mn silicate copper diffusion barrier layers on SiO₂. It was shown that high temperature annealing results in the growth of Mn silicate, the stoichiometry of which was calculated to be MnSiO₃. SRPES results also show that the interaction of metallic Mn with SiO₂ is self limiting at high temperature. In a separate experiment the role of oxygen in determining the extent of the interaction between the deposited Mn and the SiO₂ substrate was investigated. Using X-ray photoelectron spectroscopy (XPS) it has been shown that a metallic Mn film (~1 nm) cannot be fully converted to Mn silicate following vacuum annealing to 500°C. Transmission electron microscopy (TEM) analysis suggests the maximum MnSiO₃ layer thickness obtainable using metallic Mn is ~1.7 nm. In contrast, a ~1 nm partially oxidized Mn film can be fully converted to Mn silicate following thermal annealing to 400°C, forming a MnSiO₃ layer with a measured thickness of 2.6 nm. TEM analysis also clearly shows that MnSiO₃ growth results in a corresponding reduction in SiO₂ layer thickness. Based on these results it is suggested that the presence of Mn oxide species at the Mn/SiO₂ interface facilitates the conversion of SiO₂ to MnSiO₃.