Method of increasing selectivity to mask when etching tungsten or tungsten nitride

摘要

Tungsten is etched with increased selectivity with respect to the etch rate of the mask material. Plasma exposure using a mixture of Cl2 and O2 is used, prior to main etch to establish a passivation layer over the mask. A single Cl2/O2 exposure may be sufficient to provide the desired selectivity through main etch. As an alternative, main etch is performed incrementally by alternating etch chemistry exposures with plural Cl2/O2 exposures to provide a desired main etch selectivity. This method of etching tungsten or tungsten nitride in semiconductor structures is useful, particularly for the etching of gate electrodes that require precise control over the etching process.