Growth and properties of radio frequency reactively sputtered titanium nitride thin films

Abstract

Polycrystalline thin films of titanium nitride with a resistivity in the range 20–25 μΩ cm have been consistently produced on water-cooled silicon wafers by using reactive sputtering of a titanium target in Ar/N2 mixture. The variations of resistivity and the deposition rate as the functions of N2 partial pressure and applied substrate bias voltage are investigated. The N2 partial pressure as a function of nitrogen flow rate is plotted for various radio frequency (rf) power levels. The TiN films have been characterized by a wide variety of analytical techniques, such as Rutherford backscattering (RBS), Auger electron spectroscopy (AES), x-ray diffraction (XRD), scanning electron microscopy (SEM), and four-point probe. These films are golden yellow in color. RBS shows these films to be stoichiometric and AES shows them to be free of any measurable oxygen. Two multilayer metallization systems (Si/TiN/Al and Si/Ti/TiN/Al) were built to test the effectiveness of these films as a diffusion barrier. Preliminary results show that TiN films are an effective diffusion barrier between Si and Al up to 600 °C for 10 min. These films have very good step coverage, and show acceptable contact resistance to silicon after 450 °C anneal in the Si/Ti/TiN/Al metallization system.