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Abstract

A process for etching a tungsten layer formed on a semiconductor substrate is described. The etch is carried out in a parallel plate plasma reactor. The etchant gases include nitrogen trifluoride (NF.sub.3) and argon (Ar). The use of NF.sub.3 in a tungsten etching process reduces the build-up of polymers or sulfur residues on the electrode as occurs with processes utilizing sulfur or carbon fluorides as etchant gases. The process has a sufficiently high etch rate for volume production. The NF.sub.3 -Ar etch process can be used to etchback a blanket layer of deposited tungsten to form tungsten via plugs in contact areas of the device. In the via plug process, reduced micro-loading effect, that is, the tendency of some plugs to be etched away before the complete etching of the blanket layer, has been achieved. The etching of tunsten with NF.sub.3 -Ar process can be preformed in one or more steps in process utilizing several etching steps. Additionally, a tungsten etch incorporating one or more NF.sub.3 -Ar steps and one or more steps utilizing etchants such as SF.sub.6, Cl.sub.2, O.sub.2, CF.sub.4, CBrF.sub.3, CF.sub.3 Cl, CF.sub.2 Cl.sub.2 or similar etchants can be used to optimize etch rate and uniformity while obtaining the benefit of reduced residue build-up.

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