A buried aluminum nitride (AlN) layer was formed by nitrogen ion implantation into pure aluminum with doses of 10, 18 and 28 x 10(17) N+ cm(-2) at 200 keV, In order to analyze the profile of the implanted nitrogen in aluminum, 3.5 MeV He-4(+) backscattering was used, in preference to 2.0 Mev(4)He(+) backscattering. A rectangular-like profile of the implanted nitrogen was obtained from the Rutherford backscattering spectra after the dose of 10 x 10(17) N+ cm(-2). The nitrogen to aluminum ratio at the rectangular like profile is about 0.9-1.0. The results of X-ray diffraction and transmission electron diffraction indicated that aluminum nitride structure is essentially the hexagonal crystal. Aluminum nitride with f.c.c. structure also appeared on nitrogen implantation into aluminum. This is a transient structure. The resistivity of AlN formed by nitrogen implantation into aluminum is about (1.4-2.0) x 10(12) Ohm cm.