A multilayer Al/HfN/Si system, prepared by the reactive sputtering method, was subsequently annealed at various temperatures in order to find out whether the HfN intermediate layer could serve as a diffusion barrier between metal (aluminum) and semiconductor (silicon). The structure of the system before and after annealing was investigated using thin film X-ray diffraction (grazing incidence XRD) and Auger electron spectroscopy (AES). Further, observations of the outer surface of Al/HfN/Si specimens, both in deposited and annealed states, were performed by means of optical and scanning electron microscopy (SEM). The results reveal that HfN constitutes a suitable material as a diffusion/reaction barrier for the metallization scheme in electronics.