The reactivity of the Al/Si3N4/Si(100) system has been studied using x‐ray photoelectron spectroscopy (XPS). The Si3N4overlayer was prepared on Si(100) by N ion implantation and subsequent annealing. The deposition at 673 K of Al on a 18 A˚ Si3N4overlayer leads to the total reduction of the Si3N4overlayer and the aluminum nitridation. The reaction also takes place at room temperature (RT) but to a lesser degree. The stability of a RT formed Al/Si3N4/Si structure was examined by increasing the sample temperature up to 673 K. In this way, the near complete reduction of a 24 A˚ Si3N4overlayer was obtained. These results show the instability of the Al/Si3N4interface at moderate annealing temperatures. ©1995 American Institute of Physics.