RBS and SIMS characterization of tungsten silicide deposited by using dichlorosilane and tungsten hexafluoride

Rutherford back‐scattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) were used to characterize tungsten silicide (WSi x ) which had been chemical vapor deposited using higher‐than‐normal temperatures and a new reactant. Silicon wafers were subjected to a flowing mixture of dichlorosilane (SiH 2 Cl 2 ) and tungsten hexafluoride (WF 6 ) with temperatures ranging from 450°C to 650°C. The conventional process uses SiH 4 and WF 6 with temperatures from 250°C to 400°C. RBS analysis was performed on a matrix of samples produced to show silicon‐to‐tungsten ratios as functions of various deposition temperatures and reactant gas flow ratios. The Si/W ratios obtained ranged from 2.0 to 2.8 over the 450–650°C temperature range. SIMS analysis provided the chlorine and fluorine distributions in the WSi x films, again as functions of various deposition temperatures and flow ratios. This data showed fluorine concentrations on the order of 1 × 10 16 − 4 × 10 18 cm −3 , which are far lower than those concentrations observed for the conventional WF 6 /SiH 4 chemistry (about 1 × 10 20 cm −3 ).