Remote plasma-enhanced metalorganic chemical vapor deposition of aluminum oxide thin films

Aluminum oxide films were deposited using remote plasma-enhanced metalorganic chemical vapor deposition from oxygen/trimethylaluminum mixtures. Initial studies by in situ spectroscopic ellipsometry demonstrated that the aluminum oxide films deposited at temperatures < 150 degrees C were porous. The low refractive index of 1.38 was found to increase to 1.52 under ambient conditions, due to ageing. In order to improve the film properties, two routes were explored. First, by increasing the substrate temperature films with a refractive index of 1.48 were obtained at 400 degrees C, accompanied by a strong decrease in OH concentration, as shown by infrared spectroscopy. Second, by applying an additional rf bias to the substrate the in situ refractive index increased up to 1.60 and the OH groups were quantitatively removed.