Cross-sectional transmission electron microscopy investigation of Ti/Si reaction on phosphorus-doped polycrystalline silicon gate

Titanium interaction with phosphorus-doped polycrystalline silicon gate electrodes was investigated by cross-sectional transmission electron microscopy and correlated with sheet resistance measurements. Phosphorus concentration above 1×1016 ion/cm2 in the polycrystalline silicon leads to decreased TiSi2 formation, discontinuous metal silicide layer, and increased sheet resistance. A possible cause could be the formation of titanium phosphide at high phosphorus concentration in the polycrystalline silicon, competing with the total titanium available for silicide formation.