Precursor-surface interactions revealed during plasma-enhanced atomic layer deposition of metal oxide thin films by in-situ spectroscopic ellipsometry

摘要

Schematic presentation of a dual precursor ALD process with surface roughness formation. ( ) The first precursor is exposed to the surface which may already contain defects due to previous incomplete surface reactions. ( ) Fast adsorption may lead to additional defect formation in the near surface region reducing the TMO layer thickness. ( ) The second precursor reacts with the first precursor forming the desired metal oxide as well as converting the surface again to be susceptible for the first precursor. ( ) A slow reaction kinetics for the second precursor can promote near surface defect reduction, leading to the positive net growth of the TMO layer. Non-reacted precursor materials are removed during periods with presence of inert purge gases ( , ). Two characteristic parameters, the TMO layer thickness ( ) and the void fraction ( ) of a virtual surface layer with assumed thickness ( ), can be determined from analysis of spectroscopic ellipsometry (SE) data. The value of is determined from the native surface roughness of the substrate prior to deposition. See also Fig.  .