Modeling of ion-bombardment damage on Si surfaces for in-line analysis

Structures and mechanism of ion-bombardment damage on silicon wafers exposed to plasma were investigated comprehensively. By using molecular dynamics simulations high-resolution transmission electron microscopy, and composition analysis by high-resolution Rutherford backscattering spectroscopy, features such as gradual transition from the SiO₂ surface to the Si substrate and interface roughness were addressed. On the basis of these findings, the optical model that addresses the characteristics of plasma-damaged Si surfaces is given for ellipsometric analysis. The proposed model includes an interface layer modeled as a mixture of SiO₂ and Si phases. A part of the interface layer could not be removed by wet-etching, signifying the distinct features of the interface layer that are difficult to remove. The proposed model is anticipated to be practical for in-line monitoring of plasma-induced damage.