New Methods And Investigations For Regenerating Refrigerator Cryopumps

An ever increasing number of cryopumps cooled by refrigerators is used in systems for semiconductor and thin film manufacturing since they meet the high requirements imposed by the manufacturing procedures regarding the vacuum conditions. One property of these entrapment vacuum pumps is that the adsorption capacity for gases is limited. Thus, they must be regenerated from time to time. Such a regeneration cycle (heating the pump to room temperature-removing the condensate-recooling) will take 90-300 min depending on the pump's size which interrupts the manufacturing process for the corresponding time. Two initial steps are presented aiming at reducing the time for regeneration. The first method is aimed at removing only those types of gases from the pump for which only a low capacity is available (this applies in general to gases trapped by cryosorption). Tests show under what conditions such a `partial regeneration' is possible. The second method is aimed at only removing the complete quantity of gases that are condensed or adsorbed on the second stage of the cryopanel through heating, whereas baffle and radiation shield (first stage) remain at their operating temperature. The advantages of this procedure will be discussed on account of the tests done.