QUICK ACQUISITION OF CLEAN ULTRAHIGH-VACUUM BY CHEMICAL PROCESS TECHNOLOGY

Baking of vacuum system for removing adsorbed water is essential and important treatment to shorten pumping time and obtain clean UHV. Removing adsorbed water by chemical treatment, based on the decomposition and dissociation of O-H bond of the adsorbed water, was examined as an alternative method of rapidly attaining UHV conditions. Several experiments have been done using typical water decomposing gases, which are organic silane compounds, dichloro-propane and halogen gases, introduced and exposed to the vacuum chamber made of an aluminum alloy. In these gases, dichloro-propane gas exposed in vacuum chamber at a temperature of 50-100-degrees-C and pressure (0.01-40 Torr) particularly shortens the pumping time to 1/4-1/500 of the time required without dichloro-propane treatment to obtain less than 10(-8) Torr. For the exposure conditions of dichloro-propane gas at 70-degrees-C and 0.1 Torr, a quadrupole mass spectrometer showed no remaining dichloro-propane gas and reaction products within 0.5 h after pumping started. This technology is available to obtain clean UHV in a short time and has a possibility to be used as a UHV technique instead of an ordinary baking.