INFLUENCE OF WATER WAFER PRECLEAN BEFORE SELECTIVE TUNGSTEN CVD ON SURFACE-PROPERTIES INTERCONNECT AND INTERMETAL DIELECTRIC MATERIALS

Results of selective tungsten CVD on titanium nitride (TiN) are summar ized. The investigations are focused on the influence of precleaning a nd tungsten nucleation on the TiN and SiO2 surface, the CVD-W/TiN inte rface and the electrical properties of the contacts (via resistance). After a combination of HF dip and NF3 plasma a remarkable amount of fl uorine was detected at the TiN surface which was not bound to Ti. This process showed the best effect on the reproducible nucleation of tung sten. No interfacial layer could be found by cross section TEM after t he tungsten nucleation. But in the case of nucleations starting with S iH4 gas inlet tungsten growth begins with the formation of a mixture o f alpha- and beta-phase tungsten. More far away from the interface reg ion only alpha-W was detected. The lowest via resistances in filled vi as were measured for nucleations starting with WF6 gas inlet. For intr oducing SiH4 first the via resistance could be decreased using a H2 pl asma conditioning of the wafer in the deposition chamber after dry pre treatments. For this case no remarkable change of the deposition surfa ce was found by XPS. At wafers pretreated with BCl3/N2 plasmas on both surfaces (TiN and SiO2) boron nitride was found.