Photo-CVD of Al2O3 Thin Films

Al2O3 thin films have been prepared by photo-CVD under oxygen atmosphere for the first time using aluminum-tri-isopropoxide as a source material. The light source was a low-pressure Hg lamp. Without UV irradiation the deposition rate had a maximum at a particular oxygen-flow rate, which suggests the Langmuir-Hinshelwood surface-reaction mechanism. With UV irradiation, the deposition rate increased largely at a substrate temperature of less than 300°C. The activation energy of deposition reaction was as small as 1.5 kcal/mol. It was confirmed that the 185-nm light played an important role in the photodeposition. The dielectric dissipation factor ( tan δ) decreased in the samples prepared by photo-CVD, especially at a low substrate temperature of less than 300°C; that is, the film quality was improved by photo-CVD.