EFFECT OF MICROSTRUCTURE ON DEGRADATION OF ALN FILMS PREPARED BY ION BEAM ASSISTED DEPOSITION

Abstract

Two kinds of aluminum nitride (AlN) films were prepared by ion beam assisted deposition (IBAD) by changing the nitrogen ion beam energy; one was deposited with a 0.2 keV ion beam, showing a columnar structure, and the other was deposited with a 1.5 keV ion beam, showing a granular structure. The effect of microstructure on degradation of AlN films was studied by immersing them in aqueous HNO3, HCl, and NaOH solutions at room temperature. Degradation was examined mainly in terms of changes in optical transmittance and surface morphology. After immersion in HNO3 and HCl solutions, the average transmittance of the columnar film decreased gradually from the beginning of immersion, while that of the granular film maintained the initial level of transmittance for about 60 h immersion in HNO3 solution and about 80 h immersion in HCl solution. In NaOH solution, both films were detached readily from the substrate and no remarkable difference in the degradation behavior was observed between the two films. It is concluded that the IBAD AlN films with the granular structure show higher durability against aqueous acid solutions than the films with the columnar structure.