Dislocations and tungsten concentration profiles in tungsten-silicon contact areas

Dislocation formation and impurity distributions in metal-silicon contact areas were investigated by means of cross-sectional transmission electron microscopy (TEM) images and energy-dispersive X-ray measurement. Dislocations were formed in the (111) plane in the [110] direction by annealing at 700°C when W was used as barrier metal. As the diameter of contact holes decreased, dislocations became more significant. Both W and As concentration profiles in the horizontal direction showed maxima at the edges of contact holes. The diffusion length of W in the edge areas was about twice that in the center according to depth profile. This implied that stress in edge areas increased the W diffusion coefficient by a factor of about four.