AlN film growth under N2+ ion bombardment onto Al surface

Incident energy dependence of crystallization of AlN prepared by low energy ion implantation was investigated. The experiment was performed at room temperature as follows: First, the Al film of thickness of ~3000 Å was deposited onto Si(100) surface. Then, the Al surface was bombarded with N₂⁺ ions at normal incidence with a current density of ~4×10¹³ ions/cm² sec. Primary energy was changed from 500 eV to 15 keV. The base pressure of the experimental apparatus was 3×10^-7 Pa in the main chamber and ion beam irradiation deteriorated the vacuum to ~4×10^-6 Pa. The surface structure was observed by reflection high-energy electron diffraction (RHEED) during ion bombardment. For primary energies beyond ~3 keV, the fiber texture of AlN wurtzite structure was observed by RHEED whilst a polycrystalline AlN was observed for primary energies below ~3 keV. The RHEED-observation has revealed that direction of the fiber axis is normal to the surface, along with the direction of the incident ion beam. The result indicates that the higher the primary energy the better the crystallinity of AlN film