Abstract
Thin titanium nitride (TiN) film is used as a diffusion barrier in VLSI contacts, due to its excellent thermal stability, low resistivity, and good diffusion barrier characteristics. Recently, the CVD method to deposit TiN films has been extensively studied, using either TiCl4+NH3 or organometallic (OM) precursor. However, the TiCl4 is a dangerous substance and the OM precursors generally are very expensive. In this work, we will try to use a single solid precursor, i.e. TiCl4(NH3)2, to deposit TiN films as an alternative in the horizontal tubular reactor. Through the analysis of FT-IR, we found that there are O-H, N-H, C-Cl, and NH4Cl-like bonds in the precursor. Through the thermal analysis, we observe two reactions between 250 and 300℃, with 40℃ the temperature difference between the two reactions. The apparent reaction order and activation energy of the first reaction are 0.3 and 53.73 kJ/mol respectively. The corresponding values for the second reaction are 1.9 and 232.73 kJ/mol. In the horizontal tubular reactor, we can obtain films with uniform colors. The film color is purple/blue near the precursor shows purple and blue. Yet at sites away from the precursor, it changes to golden/brown In general, the purple/blue film has larger grain size, porous structure, and rough surface. In the other hand, golden and brown film shows smaller grain size, and denser structure. As to the oxygen content, the purple/blue film has a higher oxygen content than the golden/brown films. The impurity within the film will enhance the formation of poly-crystalline structure, and defects as well. This is one of the possible reasons for different colors. Adding NH4Cl to the system will help to form crystalline phase, including TiN and TiOx. If the film was annealed at 900℃ for 30 minutes, then we can observe with the diffusion between the TiN film and the Si substrate, and the subsequent formation of the Ti5Si3 crystalline phase.