Growth and chemical characterisation studies of Mn silicate barrier layers on SiO2 and CDO
Bogan, Justin (2012) Growth and chemical characterisation studies of Mn silicate barrier layers on SiO2 and CDO. PhD thesis, Dublin City University.
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This thesis investigates the suitability of manganese silicate (MnSiO3) as a possible copper interconnect diffusion barrier layer on both a 5.4 nm thick thermally grown SiO2 and a low dielectric constant carbon doped oxide (CDO), with the focus of understanding the barrier formation process. The self forming nature of this diffusion barrier layer resulting from the chemical interaction of deposited Mn with the insulating substrate has potential application in future generations of copper interconnect technologies as they are significantly thinner than the conventional deposited barrier layers. The principle technique used to study the interface chemistry resulting from the interaction of deposited manganese with the insulating substrates to form a MnSiO3 layer was x-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) measurements provided information on the structure of the barrier layers which could be correlated with the XPS results. Significant differences in the extent of the interface interaction which resulted in the formation of the MnSiO3 barrier layer were found to depend on whether the deposited Mn was partially oxidised. The studies performed on the 5.4 nm thermally grown SiO2 confirmed that the growth of the MnSiO3 resulted in a corresponding reduction in the SiO2 layer thickness. Interactions between residual metallic Mn and subsequently deposited copper layers were also investigated and showed that in order to reduce the width of the barrier layer, it was preferable that all the deposited Mn was fully incorporated into the silicate. TEM measurements were also used to investigate thicker thermally deposited Mn/Cu heterostructures on SiO2 which were subsequently annealed in order to study the diffusion interactions between copper and manganese. The formation of Mn silicate layers on low dielectric constant carbon doped oxide (CDO) was also investigated and compared with the formation characteristics on the thermally grown SiO2.
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