ON THE EFFECT OF AN OXYGEN BEAM IN SPUTTER DEPTH PROFILING

Experiments of depth resolution measurements on silicon with secondary ion mass spectrometry reveal that oxygen primary particles provide always a smaller decay length (better depth resolution) compared with other primary particles for the same penetration depth of the particle. This deviation from the classical collisional mixing model can be explained by a model which does take the incorporation of the primary particle during sputtering into account. For oxygen particles the incorporation is so high that it leads to a different matrix composition at the surface compared with the bulk of the Si sample and it results in a target swelling at the surface. It is now important to realize that the displacements of the atoms are only important relative to the position of the Si atoms in the expanded lattice and that movements with respect to the incorporated oxygen atoms does not matter. The model presented quantifies this effect and gives an accurate estimate of the reduction of the decay lengths. The model predicts a similar behavior for all primary particles with low matrix sputter yield and high incorporation of the primary particle.