Concentration profiles of boron implantations in amorphous and polycrystalline silicon

Abstract

Abstract Boron was implanted in amorphous silicon at energies in the range 30–200 keV and in polycrystalline silicon at energies in the range 70–800 keV. The boron distributions were measured with secondary ion mass spectrometry. By comparing the boron distributions in amorphous silicon and in polycrystalline silicon it was found that the used polycrystalline silicon behaves similarly to amorphous silicon for the boron stopping process. It was found that with the first four moments of the experimental distributions, an analytic description of the experimental distributions can be given by distributions of the Pearson system. The moments are determined by curve fitting of Pearson distributions to experimental distributions. In this way a systematic extrapolation of the low energy distributions outside the surface is automatically obtained. The moments are compared with the moments calculated by Winterbon and others. A satisfactory correspondence between the experimental and theoretical average ranges and standard deviations is obtained using an electronic stopping coefficient that is 1.5 times the value given by standard LSS theory. The correspondence for the skewness is less good, while for the kurtosis a distinct discrepancy is found between the experimental and theoretical values. By comparing experimental and theoretical ranges on a differential basis an electronic stopping cross-section is obtained, the energy dependence of which deviates from velocity proportionality.