Showing papers by "Stefan E. Schulz published in 1994"

Influence of Wafer Preclean before Selective Tungsten CVD on Surface Properties of Interconnect and Intermetal Dielectric Materials

Abstract: Results of selective tungsten CVD on titanium nitride (TiN) are summarized. The investigations are focused on the influence of precleaning and tungsten nucleation on the TiN and SiO2 surface, the CVD-W/TiN interface and the electrical properties of the contacts (via resistance). After a combination of HF dip and NF3 plasma a remarkable amount of fluorine was detected at the TiN surface which was not bound to Ti. This process showed the best effect on the reproducible nucleation of tungsten. No interfacial layer could be found by cross section TEM after the tungsten nucleation. But in the case of nucleations starting with SiH4 gas inlet tungsten growth begins with the formation of a mixture of α- and β-phase tungsten. More far away from the interface region only α-W was detected. The lowest via resistances in filled vias were measured for nucleations starting with WF6 gas inlet. For introducing SiH4 first the via resistance could be decreased using a H2 plasma conditioning of the wafer in the deposition chamber after dry pretreatments. For this case no remarkable change of the deposition surface was found by XPS. At wafers pretreated with BCl3/N2 plasmas on both surfaces (TiN and SiO2) boron nitride was found.