Reconfiguration and dissociation of bonded hydrogen in silicon by energetic ions

We report in situ infrared measurements of ion-induced reconfiguration and dissociation of bonded hydrogen associated with various defects in silicon at low temperatures. Defect-associated Si-H complexes were prepared by low-temperature proton implantation in silicon followed by room-temperature annealing. As a result of subsequent low-temperature ${}^3\mathrm{He}$ ion irradiation, we observed (1) ion-induced dissociation of Si-H complexes, (2) a notable difference in the dissociation rate of interstitial- and vacancy-type defects, and, unexpectedly, (3) the growth of bond-centered hydrogen, which is generally observed in association with low-temperature proton implantation. These findings provide insight into the mechanisms responsible for the dissociation of hydrogen bonds in silicon and thus have important implications for bond-selective nanoscale engineering and the long-term reliability of state-of-the-art silicon semiconductor and photovoltaic devices.

Figure 1

Infrared spectra measured at 7 K in the region of Si-H stretch mode vibrations immediately after low-temperature implantation of H into Si and after a thermal annealing at 280 K.

Figure 2

Infrared spectra, measured at 7 K, of (a) a preirradiated, defect, and H-containing Si sample, showing the existence of various defect-associated Si-H complexes. (b) After ${}^3\mathrm{He}$ irradiation (at 80 K), showing the reconfiguration of Si-H complexes. (c) After room-temperature annealing of the above sample and (d) after irradiating by ${}^3\mathrm{He}$ ions from the rare side of the sample.

Figure 3

Dose-dependence data of the ${}^3\mathrm{He}$-induced dissociation of various Si-H complexes and the corresponding growth of BCH $[{\mathrm{H}}_{\mathrm{BC}}^{+}(\mathrm{G})]$. Also shown is the ${}^3\mathrm{He}$-induced decay of BCH $[{\mathrm{H}}_{\mathrm{BC}}^{+}(\mathrm{D})]$ from Ref. [14]. Dashed lines show exponential decay and the solid lines shown the second-order decay. The decay of vacancy-type defects ($V$H${}_2$ and $V$H${}_4$) is found to be slower as compared to that of interstitial-type defects [${\mathrm{H}}_2^{*}$, $I$H${}_2$, and BCH:${\mathrm{H}}_{\mathrm{BC}}^{+}(\mathrm{D})$]. [$y$ axis (left): $I$/$I$${}_0$, where $I$${}_0$ is the initial infrared intensity of a particular defect and $I$ is the intensity of that particular defect as a function of dose.]

Figure 4

Dose-dependence data ($I/I_0$) of ${}^3\mathrm{He}$-induced dissociation of ${\mathrm{H}}_2^{*}$ defect as a function of irradiation temperature (80 and 300 K) showing that the decay is slower at room temperature.

Figure 5

Dose-dependence data of one interstitial defect ($I$H${}_2$) and one vacancy-type defect ($V$H${}_2$) whose initial infrared intensity and the thermal annealing temperature are almost the same. This clearly shows that the $I$H${}_2$ decays much faster than the $V$H${}_2$ even though they have same thermal annealing temperature.