[20p-C310-1~16] 6.4 Thin films and New materials

△ [20p-C310-9] Dielectric constants of MgF₂ films deposited by rf sputtering

〇Kohei Ogura¹, Makoto Kashiwagi¹, Junjun Jia², Hironobu Machinaga³, Yuzo Shigesato¹ (1.Aoyama Univ., 2.Waseda Univ., 3.Nitto Denko)

Keywords:magnesium fluoride films, rf sputtering, optical films

Magnesium fluoride (MgF₂) films have been widely used in optical coatings such as anti-reflection coatings because of their high transparency, large energy band gap and very low-index material in deep UV region. The main deposition methods for MgF₂ films have been electron beam evaporation based technique. As the problems of the sputter deposition of MgF₂ films, not a few fluorine deficiency can be generated where the absorbance in the visible region increases. In this study, the MgF₂ films were deposited on unheated alkali-free glass by the multi-cathodes rf magnetron sputtering equipment using the two MgF₂ targets. One target is used for sputtering deposition, whereas another one was used for fluorine supply by the rf sputtering with the closed shutter. This is for the additional fluorine supply system at various total gas pressures in order to prevent the formation of the fluorine deficiencies. As the results, the stoichiometric MgF₂ films with high crystallinity were successfully deposited.