Thin film properties of low-pressure chemical vapor deposition TiN barrier for ultra-large-scale integration applications

Abstract

Titanium nitride films deposited by low-pressure chemical vapor deposition (LPCVD) on Si(100) using TiCl4 and NH3 as reactants, were investigated as a function of deposition temperature between 400 and 700 °C. LPCVD TiN depositions were carried out in a rapid thermal chemical vapor deposition system with a total deposition pressure of 155 mTorr. Stoichiometric TiN films were formed regardless of the deposition temperature and composition was uniform across the entire film. Depending on deposition temperature, varying amounts of chlorine (Cl) and oxygen (O) impurities are found in the TiN films. Films deposited at lower temperatures (400 and 550 °C) contained more than 5 at. % Cl, while the films produced at 700 °C contained as little as 1 at. % Cl. For the films deposited at 650 and 700 °C, the bulk of the TiN films is oxygen-free. LPCVD TiN deposition rates of 400 Å/min with no appreciable incubation time were routinely achieved. The LPCVD TiN deposition process is surface reaction controlled with an activation energy of 35 kJ/mol. Excellent TiN film conformality was observed. Electrical resistivity of the TiN films was found to decrease with increasing deposition temperature. Resistivity in the range of 85 μΩ cm was observed. Polycrystalline ∂-TiN phase with a preferred orientation of (200) was observed at all deposition temperatures. These TiN films have columnar grain structure. The TiN/Si interface is smooth, and no voids are observed at the silicon substrate interface, a prerequisite for good adhesion. An increase in the average grain size and lattice parameter was observed with increasing deposition temperature. While increasing the deposition temperature increases the TiN film growth rate, it also produces larger TiN grains and rougher surface morphology. The reliability of the TiN films as a diffusion barrier between aluminum and silicon was evaluated by diode leakage current measurements, which remained low after being thermally stressed up to 550 °C.