Integrated Chemical Vapor Deposition and Plasma Etchback of Tungsten in a Multichamber, Single‐Wafer System

Abstract

An integrated deposition and etchback process to form tungsten plugs in submicron contacts and vias has been developed with an Applied Materials, Inc., P5000 WCVD system using experimental design and response-surface methodology to characterize both the low-pressure chemical vapor deposition chamber and the magnetron-enhanced etchback chamber for 150 mm diam wafer processing. Tungsten is deposited at 80 torr and 475~ by the H2 reduction of WF6. Etchback is then carried out in two steps: bulk tungsten is etched with an Ar/SF6 mixture until excited N2 molecules from the underlying TiN adhesion layer are detected in the plasma, and residual TiN is then etched for a fixed time with an Ar/C12 plasma. Both etching steps employ a rotating magnetic field which is orthogonal to the applied electric field. Although the use of the magnetic field has no pronounced effect on the etch rate of either film, it provides broad regions of highly uniform etching. In addition, the dc bias voltage, which was measured as part of the TiN study, decreases with increasing magnetic field without reducing the etch rate of the film.