Investigation of Surface Damage in Si Exposed to Ar Plasma by Spectroscopic Ellipsometry and Grazing X-Ray Diffraction

Abstract

Listen

Translate article

Low-damage processes in plasma-surface interactions, particularly lattice deformation and the degree of damage in a single-crystal Si surface exposed to Ar plasma, are investigated by spectroscopic ellipsometry (SE) and grazing X-ray diffraction. The dielectric function spectrum of the damaged Si layer in nano-depth is obtained by use of damage depth estimated by a method based on SE model analysis and confirmed by step etching combined with SE measurement. The third-derivative lineshape of the imaginary part ε2 of the complex-dielectric function provides the damage dependences of interband transition energy and broadening parameter for the E1 (Λ3→Λ1) optical interband transition. The result shows that the surface damage proceeds through lattice expansion and relaxation. The lattice deformation in the damaged surface is also investigated by grazing X-ray diffraction. The X-ray rocking curve around (422)Si is asymmetric and involves small subsidiary curves corresponding to the lattice expansion and relaxation. These observations are in good agreement with the lattice deformation process obtained from the SE analysis.