CORROSION OF ALUMINUM NITRIDE SUBSTRATES IN ACID, ALKALINE-SOLUTIONS AND WATER

Aluminium nitride substrates were immersed in acid, basic solutions an d deionized water for 1-120 h at room temperature. The corrosion rates are higher in basic solutions (NaOH and KOH) than those in acid solut ions (CH3COOH, HCOOH, HNO3, HCl and H2SO4) and deionized water. The we ight loss of AlN corroded in alkali aqueous reaches 70% and results in an increase in surface rough ness ranging from 10 nm to 7 mu m after 3 days corrosion. However, the weight loss in acid solution is only 1/ 700 of the alkali case. Violent chemical reactions between AlN and bas ic solutions were observed. Na2O, or Na2Al2O4.6H(2)O, is the intermedi ate product, and NaOH is a catalytic agent of the reaction. The surfac e morphology of the AlN etc hed by alkali ne solutions is coral-like i n microscopic view and appears like hills. In contrast, only several a tomic layers of AlN surface are etched off in acid solutions and in de ionized water. The lightly etched surface is mirror-like and flat, and the shapes of the grains are visible under the microscope, as the cor rosion rate of each AlN grain varies with different crystal orientatio ns. Consequently, after etching in acid solutions, the resulting micro scopic surface morphology looks like a map of a jigsaw puzzle.