Alkaline Hydroxide Induced High Level of Alkali Metal Concentration Effect on the Characteristics of LTO Layer

The control and evaluations of alkali metal such as Na have been important issues in device process. LTO layer was deposited on backside of wafer as backseal of epitaxial substrate. The backseal wafer with LTO was evaluated to study effect of Na contamination which was observed after NaOH mixture dip. We found Na out diffusion from LTO layer inducing surface oxidation rate increase in oxidation process. These phenomena considered to Na property of low boiling temperature point. However, Na from LTO layer did not affect epitaxial process because of hydrogen pre-baking in epitaxy process.