Asarco LLC

Bradley D Bunn

Margaret W Staub

Jeffrey Burton

A method and apparatus are provided for making high purity and preferably oxygen free substantially void free and inclusion free copper castings such as billets from high purity copper. The castings are particularly useful to make sputtering targets used in sputtering deposition processes in the fabrication of electronic components. The method comprises melting high purity copper in a covered crucible using a non-contaminating heating source such as a coil induction furnace. The melted copper in the crucible is solidified using a specially controlled cooling procedure wherein the bottom of the crucible is cooled so that molten copper is maintained on top of solidified and solidifying copper until the copper is solidified. In a preferred apparatus and method, the furnace and crucible, which is disposed between the coil of the furnace and contains molten copper, are positioned above a cooling jacket and the crucible passed continuously downwardly through the opening in the cooling jacket cooling the lower portion of the crucible. A reduced heat is maintained in the furnace to heat the upper portion of the crucible within the coil and maintain a layer of molten copper over the copper solidifying in the lower portion of the crucible passing through the water jacket. A reducing gas is supplied to the covered crucible and the crucible is insulated during the method.

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Arvada, CO, United States of America

Bradley D Bunn