Growth characteristics of Mn silicate barrier layers on SiO2

Abstract

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.