Chemical vapor deposition of titanium nitride thin films: kinetics and experiments

Titanium nitride (TiN) films were grown by CVD (chemical vapor deposition) from titanium chlorides generated in situ by direct chlorination of titanium metal, ammonia (NH3) and hydrogen (H2) as carrier gas on single crystal c-plane sapphire, WC–Co, stainless steel and amorphous graphite substrates. Kinetic pathways involving four surface reactions have been proposed to simulate the growth rate. The proposed model has been validated by experiments performed at different temperatures (650–1400 °C) and pressures (300–1000 Pa), with different amounts of precursors (N/Ti ratio in gas phase) and on different substrates. The study shows that on polycrystalline materials, the crystal orientation depends on supersaturation while the (111) preferred orientation is forced by underlying c-plane sapphire whatever the supersaturation. The low N/Ti ratio in the gas phase leads to a low growth rate and a dense TiN film which is the key to obtaining golden TiN. The high growth rate corresponds to brown TiN. Globally, the study shows that the golden color is independent of texture and is just the natural aspect of a dense stoichiometric TiN layer.