KAGATSUME Akiko Hitachi Co. Ltd. Mechanical Engineering Research Laboratory, Researcher, 機械研究所, 第7部副参事研究員
KITAJIMA Masahiro National Research Institute for Metals, Second Research Group, First Sub-Group Leader, 第2研究グループ, 第1サブグループリーダー
|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1994 : ¥2,000,000 (Direct Cost : ¥2,000,000)
Although there are many merits in the glow discharge cleaning method to have ultra-high vacuum within a short time, such as use of simple equipment and without usage of the magnetic field, because of large cathode fall (typically 300 volt), it has some problems, such as the sputtering of the vacuum wall by the bombardment of the plasma ions, trapping of the discharge gas in the vacuum chamber, and slow pumping speed of the pumping system due to the high gas pressure during cleaning discharge. To solve those problems and to improve the glow discharge cleaning method, we introduced an auxiliary plasma source of glow mode plasma source (GMPS) by use of hot cathode, and we demonstrated the solution of those problems.
As results of the experimental investigation, the working pressure of the discharge gas could be reduced to 0.2 Pa, which is about two order of magnitudes smaller. The cathode fall and the difference of the potential between the plasma and the vacuum chamber are reduced to several 10 volts.
We have also investigated the mechanism of the desorption of the impurity gases during the discharge cleaning. The argon, hydrogen, deuterium gases are used as the discharge gases, and temporal variation of the partial pressure of those gases have been measured. As the results from this study, the dominant desorption mechanism of the impurity gases within a short time is due to the physical process, which is bombardment of the ions. On the other hand, in a longer time of the operation, the chemical process is the dominant desorption mechanism.
From those results mentioned above, we concluded that the discharge cleaning method with use of GMPS is quite effective method by improving the demerit of the normal glow discharge cleaning methods.
It can be said that this discharge cleaning method with use of GMPS is quite effective to obtain ultra-high vacuum within a short time.