BORON IMPLANTATION IN SILICON - ISOTOPE EFFECTS STUDIED BY SECONDARY ION MASS-SPECTROMETRY

The range distributions of 10B+ and 11B+ ions implanted into silicon have been studied by secondary ion mass spectrometry. Implantation energies in the range of 50 to 250 keV were used. An isotope effect on the boron profiles is clearly resolved for the energies above ∼100 keV. Projected range and parallel straggling values extracted from the measured profiles are compared with calculated values obtained from Monte Carlo simulations and from numerical computations applying Boltzmann's transport equation. A good agreement is found, and also the computed values reveal a clear isotope dependence. This effect is attributed to a larger electronic stopping cross section Se for the 10B + ions than for the 11B+ ions at a given energy in the range where Se is roughly proportional to the ion velocity. 5.