Michael S. Ameen

Electrical properties of Ti/TiN films prepared by chemical vapor deposition and their applications in submicron structures as contact and barrier materials

Titanium nitride films were prepared by low pressure chemical vapor deposition from TiCl4 and NH3 at 630°C. Metallic Ti films were deposited from TiCl4 and H2 using plasma-enhanced chemical vapor deposition at 570 and 590°C. A layer of TiSi2 was formed on the silicon surface. TiSi2 thickness depends on deposition temperature and deposition time. All the films have chlorine concentrations lower than 2 at.% and bulk resistivities less than 150 μΩ-cm. The step coverage of TiN films is close to 100% and that of Ti/TiSi2 is better than 50% in high aspect ratio submicron vias. The contact resistances of CVD TiN and Ti films to both p+ and n+ silicon are lower than those of PVD TiN/Ti films when contact hole size is smaller than 0.5 μm. The contact resistances of chain patterns on poly silicon and on WSix from CVD TiN/Ti are also lower than those from sputtered TiN/Ti. Higher Ti deposition temperature and thicker TiSi2 films on the silicon surface result in slightly lower contact resistance. When contact size is smaller than 0.4 μm, the device yield using chemical vapor deposition is higher than that using the corresponding sputtering process.