Interactions of hydrogen molecules with bond-centered interstitial oxygen and another defect center in silicon

Abstract

Infrared spectra obtained from Czochralski (CZ) silicon heated in the range $1100<~T<~1300\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in ${\mathrm{H}}_{2},$ ${\mathrm{D}}_{2},$ or mixtures of the two gases, show vibrational absorption at $1075{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ due to perturbed bond-centered interstitial oxygen atoms ${\mathrm{O}}_{i}.$ Deconvolutions of these absorption profiles imply that the observed perturbations to the ${\mathrm{O}}_{i}$ atom are due to adjacent defects incorporating two H atoms. This interpretation is confirmed by detection of modes ${\ensuremath{\nu}}_{1}$ $({\mathrm{\ensuremath{\nu}}}_{1\mathrm{H}\mathrm{H}}{,\mathrm{\ensuremath{\nu}}}_{1\mathrm{H}\mathrm{D}}{,\mathrm{\ensuremath{\nu}}}_{1\mathrm{D}\mathrm{D}})$ with ${\ensuremath{\nu}}_{1\mathrm{H}\mathrm{H}}{=3789\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and ${\ensuremath{\nu}}_{2}$ $({\mathrm{\ensuremath{\nu}}}_{2\mathrm{H}\mathrm{H}}{,\mathrm{\ensuremath{\nu}}}_{2\mathrm{H}\mathrm{D}}{,\mathrm{\ensuremath{\nu}}}_{2\mathrm{D}\mathrm{D}})$ with ${\ensuremath{\nu}}_{2\mathrm{H}\mathrm{H}}{=3731\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}1},$ that both correlate in strength with that of the $1075{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ absorption. A third set of modes ${\ensuremath{\nu}}_{3}$ $({\mathrm{\ensuremath{\nu}}}_{3\mathrm{H}\mathrm{H}}{,\mathrm{\ensuremath{\nu}}}_{3\mathrm{H}\mathrm{D}}{,\mathrm{\ensuremath{\nu}}}_{3\mathrm{D}\mathrm{D}}),$ with ${\ensuremath{\nu}}_{3\mathrm{H}\mathrm{H}}{=3618\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ detected in heat-treated CZ and float zone silicon and not related to the absorption at $1075{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1},$ must be due to H-H pair defects trapped at an unknown impurity or lattice defect. The frequencies of the ${\ensuremath{\nu}}_{1\mathrm{H}\mathrm{D}},$ ${\ensuremath{\nu}}_{2\mathrm{H}\mathrm{D}},$ and ${\ensuremath{\nu}}_{3\mathrm{H}\mathrm{D}}$ modes imply that the three defects are ${\mathrm{H}}_{2}$ molecules with weakened bonds and small dipole moments resulting from interactions with either adjacent oxygen atoms $({\ensuremath{\nu}}_{1},{\ensuremath{\nu}}_{2})$ or a second type of trap $({\ensuremath{\nu}}_{3}).$ Annealing treatments imply that isolated ${\mathrm{O}}_{i}\ensuremath{-}{\mathrm{H}}_{2}$ complexes can dissociate for $T>~70\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ allowing interstitial ${\mathrm{H}}_{2}$ molecules to diffuse away but they can be retrapped during a subsequent anneal at $T<~50\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$