[en] Annealing a silicon surface covered with a submonolayer of a - Si at 600 degree C gives a surface with voids that undergo a ripening process. If the uncovered surface has steps, the deposition of the growing and diffusing voids at this high temperature on the step creates a coarsening of the step. The coalescence of the voids with the step creates a denuded zone (in which the density of voids is below the average) both at the upper and the lower terraces. It is shown here, that both the exact morphology and the scaling of the step width on one hand, and the density of voids near the step on the other hand, can be analyzed quantitatively. The scaling relations of the step width, the dynamic scaling of the voids, the denuded zones and the scaling of the diffusion constant with size, are shown to be interconnected. Using all these relations, it is possible to get a complete picture of all the characteristics of this anomalous diffusive coarsening phenomenon. So we prove that the void coarsening process is dominated by voids diffusion and coalescence and that void diffusion is dominated by boundary vacancy diffusion. Thus the diffusive models of coarsening are non - relevant in this case