Dopant redistribution during the solid-phase growth of CrSi2 on Si(100)

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Abstract
The results of an investigation into the redistribution of dopants—As, B, and P—during the solid‐phase reaction of Cr with Si substrates to form CrSi2 are presented. Cr layers, 47 nm thick, were evaporated onto B‐doped Si substrates which had previously been implanted with one of the three dopants. Two implant doses were investigated for each dopant. Following heat treatment at 500 °C, doping profiles were determined by secondary‐ion mass spectrometery (SIMS) and, for arsenic‐doped samples, by Rutherford backscattering spectroscopy (RBS). Both SIMS and RBS were also used to measure the extent of silicide formation. The results demonstrate that B and P are transported from the Si substrate to the surface of the growing CrSi2 layer while As accumulates at the CrSi2/Si interface. The silicide formation reaction is shown to be inhibited by large As concentrations. No other dopant‐concentration‐related effects were observed. A model, based on dopant segregation driven by the relative free energies of CrSi2 and Cr‐dopant compounds, is proposed to explain the results.