Electrical and recombination properties of copper-silicide precipitates in silicon

Copper-silicide precipitates in silicon obtained after copper diffusion and quench in different liquids were studied by transmission electron microscopy and capacitance spectroscopy techniques. A correlation between the quenching rate, geometric size, and deep level spectra of the copper-silicide precipitates was established. The unusually wide deep level spectra are shown to be due to a defect-related band in the bandgap. The parameters of the band are evaluated using numerical simulations. A positive charge of copper-silicide precipitates in p-type and moderately doped n-type Si is predicted by simulations and confirmed by minority carrier transient spectroscopy measurements. Strong recombination activity of the precipitates due to attraction of minority carriers by the electric field around the precipitates and their recombination via the defect band is predicted and cor;firmed by the experiments. The pairing of copper with boron is shown to be an important factor determining the precipitation kinetics of the interstitial copper at room temperature.