Properties of LPCVD TiN Barrier Layers

Low temperature chemical vapor deposition of titanium nitride thin films from titanium tetrachloride and ammonia is typically performed at a temperature between 600°C and 700°C. This is acceptable for barrier layer deposition at the contact level. Lowering the deposition temperature to 450°C is attractive because the process would then be compatible with multi-level aluminum metallization. It is known that lowering the deposition temperature tends to increase both the chlorine content and the resistivity of the resulting films. Here we demonstrate that by tuning the deposition process and the post deposition treatment of the film it is possible to significantly reduce the resistivity and chlorine content of the low temperature film. Lowering the deposition temperature is shown to increase the nitrogen to titanium ratio of the film while decreasing the grain size, and density. The low temperature process provides similar barrier properties to the high temperature process.