AVS 50th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM4
Improvement of Reproducibility in Deposition Rate of MgF@sub 2@ Film Prepared by an rf Sputtering Technique named Keep Molecular Sputtering Method

Wednesday, November 5, 2003, 9:20 am, Room 329

Session: Optical Thin Films and Photovoltaics I
Presenter: T. Deguchi, Olympus Optical Co., Ltd., Japan
Authors: K. Kawamata, Olympus Optical Co., Ltd., Japan
T. Deguchi, Olympus Optical Co., Ltd., Japan
E. Kusano, Kanazawa Institute of Technology, Japan
A. Kinbara, Kanazawa Institute of Technology, Japan
Correspondent: Click to Email
MgF@sub 2@ film is generally formed by electron-beam evaporation rather than sputtering, because sputtered MgF@sub 2@ film shows poor transparency, resulting from F deficiency. To solve this problem, we have proposed a Keep-Molecular-Sputtering (K-M-S) method. It involves keeping magnesium fluoride target at a high temperature, and providing the sputtering species as a form of molecules. However, deposition rate of the K-M-S method has a large dispersion. In this study, reproducibility of deposition rate of MgF@sub 2@ film in the K-M-S method has been improved by monitoring optical emission intensity ratio of MgF@super *@/O@super *@. A sputtering-up-type rf magnetron sputtering machine was used in the experiment. Sputter source is 1-2 mm granular MgF@sub 2@ put on a 100 mm diam. quartz plate backed with a Cu plate. The source-to-substrate distance was 75 mm. Discharge gas was O@sub 2@ with a flow rate of 80 sccm. MgF@sub 2@ films are deposited on glass substrate (BSL7) set to an aluminum holder rotating during film deposition. Pre-sputtering of the target started when H@sub 2@O partial pressure became constant. Rf power was controlled to a certain value in the range between 480 and 520 W to remain the optical emission intensity ratio of MgF@super *@/O@super *@ at a constant value. The reproducibility of the deposition rates has been improved to ±17%(115±24 nm/min.) by controlling rf power, compared with ±28%(111±31 nm/min.) obtained for a constant power of 550W. For all MgF@sub 2@ films, optical absorptance at a wavelength of 400 nm was less than 5%. We have also discussed mechanisms of the K-M-S process based on analysis using a quadrupole mass spectrometer.