A Consideration of Fluorides Classification and Self Re-Combination Sputtering of Magnesium Fluoride Films

The author had investigated fluoride thin films made by sputtering, which is conducted with introducing a continuous Ar gas flow. The fluoride thin film made in such way, however, had not shown good optical characteristics. The author had hit upon a consideration to classify the fluorides from the viewpoint of their melting point (M.P.) and boiling point (B.P.). The M.P. B.P. classification of fluorides could well explain why sputtering does not make good MgF2 thin film. On the other hand, the author had invented the Self Re-Combination (SRC) sputtering process. This SRC sputtering is able to make the fluoride thin films on the SiO2 substrate and the Si substrate. This time, the author has invented the Multi cathode Re-Combination (MRC) sputtering process, which is improved from the SRC sputtering process for MgF2. The MgF2 thin film made by this MRC sputtering has shown a quite small absorption coefficient, less then 0.001 at 193 nm wavelength. This MRC sputtering is conducted without introducing fluorine gas, which means the MRC gives us a simple and a safety process.