Method for etching tungsten

The  invention relates to an improved process for the forming and etching of tungsten containing film on a semiconductor wafer.Refractory metals such as chemical vapor deposited tungsten have been identified as suitable interconnect material for VLSI/ULSI applications. Chemical vapor deposited tungsten is finding applications in the area of gate and interconnect technology due to its electromigration resistance, excellent step coverage, and because its thermal expansion is similar to that of silicon. Chemical vapor deposited tungsten also withstands higher process temperatures and does not form hillock as will aluminum.

This invention  described an useful embodiment of a process for etching of a tungsten film which comprises the steps of: removing tungsten from unmasked areas of a workpiece using a first etchant that removes tungsten at a greater rate than it removes photoresist; and removing tungsten from unmasked areas of the workpiece using a second etchant that removes tungsten at a greater rate than it removes silicon dioxide.

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