Effects of dopant concentration on microstructure and strain states of in-situ phosphorus-doped epitaxial silicon films during dry oxidation

The adjustability of the incorporation and distribution of P dopants in Si materials has led to their application in various electronic and photovoltaic devices. In particular, P-doped Si films have been investigated for dopant-induced phenomena such as oxidation enhancement and dopant segregation during thermal oxidation. Despite their technical as well as scientific importance of dopant behaviors in P-doped Si films, these were hardly observed due to low P incorporation. In this study, we prepared and oxidized P-doped epitaxial Si (Si:P) films grown on the Si(100) substrate using in-situ P-doped deposition technique to incorporate high P concentration up to 9.6% (4.8 × 10²¹ cm⁻³) in the films, exceeding solid solubility limits (~3 × 10²⁰ cm⁻³). We found that in oxidized samples with P concentration greater than 6.2%, defects were generated in the near-surface region of Si:P layers and segregated P was observed at the defected areas. The chemical bonding states of P at the oxidized Si:P film increased in the P 2p peak intensity at the interface between the oxide and the Si:P layer, indicating P segregation at this interface. In the strain states of Si:P films, the decrease in the out-of-plane lattice parameter was observed, while maintaining the constant in-plane lattice parameter, implying strain release due to decreased P concentration in the Si:P layer after dry oxidation.