Integrated deposition and etchback of tungsten in a multi-chamber, single-wafer system

An integrated deposition and etchback process to form tungsten plugs in submicron contacts and vias was developed using experimental design and response-surface methodology to characterize both the low-pressure chemical vapor deposition (LPCVD) chamber and the magnetron-enhanced etchback chamber for 150-mm-diameter wafer processing. Tungsten was deposited at 80 torr and 475°C by the H₂ reduction of WF₆. Etchback was then carried out in two steps: bulk tungsten was etched with an Ar/SF₆ mixture until excited N₂ molecules from the underlying TiN adhesion layer were detected in the plasma, and residual TiN was then etched for a fixed time with an Ar/Cl₂ plasma. Both etching steps employ a rotating magnetic field. Although the use of the magnetic field has no pronounced effect on the etch rate of ether 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