Characterization of spin-on titanium-nitride

The properties of spin-on titanium-nitride (SO-TiN) thin films were optimized for integrated-circuit application. The two steps of the spin-on process were characterized: one, the initial step in which a thin-film titanium oxide is formed, and two, the conversion of the thin film to titanium-nitride (TiN) by rapid thermal processing in ammonia. The spin-on TiN showed a uniform coating on a flat wafer surface for all the precursors. However, on non-planar topography some solutions produced cracked films while others did not. The precursor's effect was investigated, and it is proposed that the optimized precursor should include more carbon in the initial annealing stage so the film does not crack. The chosen precursor, titanium-tertiary-butoxide, was investigated and characterized versus processing temperature, heating rate, and gas flow. The experiment was designed at the 700°C-1000°C temperature range, with 0.1-200°C/sec. heating rate, and hold time of 30-300 sec. at the upper temperature before rapid cool down. The optimal processing conditions at NH3 are heating at 100-120°C/sec. ramp from room temperature up to 900°C-1000°C where the wafer is annealed for 30-100 seconds before rapid cool down to room temperature.