Electrical studies on H-implanted silicon

Abstract

Electrical properties of high-dose (1.6\ifmmode\times\else\texttimes\fi{}${10}^{16}$ at./${\mathrm{cm}}^{2}$) ${\mathrm{H}}^{+}$-implanted B-doped silicon have been investigated using transient capacitance spectroscopy, capacitance-voltage, and spreading resistance profiling. The role of hydrogen is twofold: to interact with the defects created by ion implantation, modifying their electrical properties, and to neutralize the shallow-acceptor dopants. The evolution of the defects responsible for the deep levels and the depth of the neutralized region have been investigated after iso- chronal annealing at various temperatures up to 800 \ifmmode^\circ\else\textdegree\fi{}C. Deep-level transient spectroscopy spectra show three hole traps; two of them, H(0.67), H(0.33), have been tentatively identified as vacancy-hydrogen complexes (${\mathrm{VH}}_{2}$, ${\mathrm{VH}}_{3}$) while the attribution of the third, H(0.23), detected in the samples annealed at 400--450 \ifmmode^\circ\else\textdegree\fi{}C, is uncertain. As a function of the heat treatment, the total number of defects is strongly reduced at 300 \ifmmode^\circ\else\textdegree\fi{}C, it increases for T>300 \ifmmode^\circ\else\textdegree\fi{}C and at the highest temperatures, namely 800 \ifmmode^\circ\else\textdegree\fi{}C, the defects disappear. The first decrease is attributed to the formation of neutral ${\mathrm{VH}}_{4}$ complexes and the disappearance to complete decoration of point defects or their agglomeration. The thickness of the passivated region has a minimum at 300 \ifmmode^\circ\else\textdegree\fi{}C, which corresponds to the formation of the stable ${\mathrm{VH}}_{4}$. At lower temperatures, the hydrogen necessary for the passivation is the unbonded one and presumably comes from the implantation process itself. At higher temperature, H comes from the breaking of the ${\mathrm{VH}}_{4}$ or ${\mathrm{H}}_{\mathit{n}}$ complexes. These results are in good agreement with our previous studies concerning the role played by hydrogen in affecting the crystal properties of silicon.