Influence of mixed reductants on the growth rate of WF6-based W-CVD

The influence of adding dichlorosilane (SiH2Cl2) or germane (GeH4) to the SiH4-based reduction reaction of tungsten-hexafluoride (WF6) has been investigated in order to enhance the properties of the silane W-CVD process: e.g. selectivity and step-coverage. It is shown that the kinetics of the silane-dichlorosilane process can be characterised by a surface reaction limitation, thus improving the control of the process. For the mixed SiH4GeH4 reduction reaction of WF6 it is shown that the GeH4 process dominates the reaction kinetics. Also addition of SiH2Cl2 to the GeH4-based reduction of WF6 has been examined. It is found that in this case the formation of W is only slightly influenced. The reaction kinetics are similar to that of the unmodified deposition process.