Bandgap Chemical Corporation

Bandgap Technology Corporation

Robert E Doane

Bruce J Sabacky

Barry J Streusand

Don A Almond

Semiconductor grade tungsten hexafluoride (WF.sub.6) is produced by reacting tungsten metal with a recirculating flow of gaseous WF.sub.6 containing a small concentration of fluorine in a heated reactor. The high purity WF.sub.6 produced is useful for deposition of tungsten metallization in fabricating VLSI integrated circuitry.

Synthesis of semiconductor grade tungsten hexafluoride

A process is provided for purifying liquid tungsten hexafluoride containing volatile and non-volatile impurities. The process comprises the steps of evaporating tungsten hexafluoride from non-volatile impurities dissolved in liquid tungsten hexafluoride and condensing the evaporated tungsten hexafluoride. The condensed tungsten hexafluoride is subjected to freezing to solidify the tungsten hexafluoride. Volatile impurities are then evacuated from the solid tungsten hexafluoride. Thereafter, the solid tungsten hexafluoride is thawed to liquid tungsten hexafluoride to release trapped volatile impurities and then heated to a temperature above the boiling point of tungsten hexafluoride under pressure in a closed container. The volatile impurities dissolved in the thawed tungsten hexafluoride are removed and collected above the thawed tungsten hexafluoride and vented into an evacuated space.

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Idaho Springs, CO, United States of America

Robert E Doane