Amorphous oxide precipitates in silicon single crystals

Czochralski-grown dislocation-free silicon single crystals1 are used almost exclusively by the semiconductor industry in the manufacture of contemporary VLSI (very large-scale integration) devices. These crystals contain small concentrations of dissolved oxygen, which diffuses on heating to form precipitates of silica. Because VLSI device performance depends on the size and distribution of such precipitates the characterization of these precipitates is of immense current technological interest. The volume fraction of the precipitates is only of the order of 10 parts per million, which makes their characterization extremely difficult. Here we show that the technique of small-angle neutron scattering can be used to fully characterize, in a single experiment, the precipitates (in terms of orientation, size, number density and volume fraction) in sample volumes of ∼10 cm3. This method may be used by the semiconductor industry to characterize the oxide precipitates after device-processing heat treatments in a batch of wafers.