Structural relaxation of ${\mathit{P}}_{\mathit{b}}$ defects at the (111)Si/${\mathrm{SiO}}_2$ interface as a function of oxidation temperature: The ${\mathit{P}}_{\mathit{b}}$-generation–stress relationship

Electron-spin-resonance (ESR) studies of intrinsic ${\mathit{P}}_{\mathit{b}}$ defects at the (111)Si/${\mathrm{SiO}}_2$ interface have been carried out as a function of oxidation temperature ${\mathit{T}}_{\mathrm{ox}}$ for the range 22<${\mathit{T}}_{\mathrm{ox}}$<1140 °C. The properties of both as-oxidized structures and structures obtained after exhaustive dehydrogenation have been compared, thus separating the H passivation factor. The data reveal drastic differences in the interfacial nature of low-${\mathit{T}}_{\mathrm{ox}}$ and high-${\mathit{T}}_{\mathrm{ox}}$ Si/${\mathrm{SiO}}_2$ structures, the demarcation range being ≊750–850 °C; while a fairly constant density (${\mathit{P}}_{\mathit{b}}$)∼${10}^{13}$ ${\mathrm{cm}}^{\mathrm{-}2}$ is found all over the range 300<${\mathit{T}}_{\mathrm{ox}}$<800 °C, it gradually decreases with increasing ${\mathit{T}}_{\mathrm{ox}}$ above ∼800 °C. Comparison with mechanical-stress data for the Si/${\mathrm{SiO}}_2$ structure reveals close linear correlation with the average stress ${\mathrm{\sigma }}_{\mathrm{av}}$ in the superficial ${\mathrm{SiO}}_2$ film, so that [${\mathit{P}}_{\mathit{b}}$] is seen to decrease to <${10}^{10}$ ${\mathrm{cm}}^{\mathrm{-}2}$—a ${\mathit{P}}_{\mathit{b}}$-defect ‘‘free’’ interface—along with ${\mathrm{\sigma }}_{\mathrm{av}}$ for ${\mathit{T}}_{\mathrm{ox}}$→1150 °C. The underlying physical mechanism is global structure relaxation of the ${\mathrm{SiO}}_2$ layer initiating at ∼800 °C, gradually reducing the need for intrinsic ${\mathit{P}}_{\mathit{b}}$ generation to account for lattice mismatch.