ELECTRON-BEAM EVAPORATOR CONSTRUCTED FROM ALUMINUM-ALLOY AND THE GETTERING EFFECT OF CHROMIUM FILMS

We developed a new ultrahigh vacuum (UHV) electron beam evaporator. The vacuum chamber was constructed from aluminum alloy to minimize the chamber baking temperature and baking time- A new electron gun was developed to minimize the desorption of gas. Chromium (Cr), titanium (Ti), molybdenum (Mo), and copper (Cu) thin films were deposited by this evaporator. We can hold the pressure under 1 X 10(-8) Torr to evaporate Cr and Cu. After evaporation of Cr, the lowest pressure, 2 X 10(-10) Torr, is achieved. The pressure after the baking of the vacuum chamber is 3 X 10(-9) Torr. The pressure after Cr evaporation is about one-tenth of that after the baking of the chamber. This is due to the gettering effect of the deposited Cr films, which has ten times the pumping ability of the turbomolecular pump. The pumping power of Cr films is stronger than that of Ti films.