Computer codes for synthesizing random and channeling backscattering spectra have been elaborated to characterize the surface and interface structures formed or modified by ion implantation. Both effects of isotopes and energy fluctuation are taken into account in the spectrum simulation. This backscattering measurement combined with the simulation method is applied to characterization of the N+‐implanted Al films and to quantitative analysis of chemical reaction and interdiffusion induced by ion‐beam mixing. An ion‐beam‐induced damage profile and its epitaxial recovery of crystallinity are analyzed by the simulation of channeling spectra from ion‐implanted Al2O3substrates.