Formation of photosensitive alumina-based gel films and their application to fine patterning

Photosensitivity of Al2O3 and Al2O3-SiO2 gel films, which were derived from Al(O-sec-Bu)3 modified with a variety of (beta) -diketones was studied. These gel films exhibited optical absorption bands in a UV-range, associated with the (pi) -(pi) * transition in the chelate rings of the (beta) -diketonato ligand. The irradiation of the gel films with UV-light corresponding to this transition decreased the solubility of these gel films in organic solvents or acidic aqueous solutions, accompanied with the dissociation of the chelate rings. Based on the change in solubility by the UV-irradiation, fine-patterns of Al2O3 and Al2O3-SiO2 thin films, containing over 30 mol% Al2O3, were formed on various substrates. The incorporation of benzophenone in Al2O3 gel films was also found to improve their photosensitivity. Moreover, it was demonstrated that the present photosensitive gel films were applicable to the fabrication of diffraction gratings using excimer laser and a phase mask.

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