The determination of phases formed in AlSiCu/TiN/Ti contact metallization structure of integrated circuits by x-ray diffraction

X-ray diffraction (XRD) analysis was performed in order to determine the crystallographic phases formed in AlSiCu/TiN/Ti contact metallization multilayers of very large scale integration/ultralarge scale integration devices deposited over SiO2 and Si substrates as a function of the annealing temperatures, the oxidation treatment of the TiN diffusion barrier, the presence of a TiN antireflective coating (ARC) and the barrier thickness. The most striking results of this study are the formation of the Ti7Al5Si12 phase and the recrystallization of Al after a 550 °C annealing for a nonoxidized 50 nm TiN barrier deposited on Si substrate. This Ti7Al5Si12 phase formation and the Al recrystallization tend to be blocked when an oxidized TiN barrier is used. It is also suggested that an air break process tends to lower the junction spiking problems since Ti7Al5Si12 is believed to be detrimental to the contact metallization layers. These effects were very weak for the 95-nm-thick TiN barrier. In addition, a TiN-ARC layer reduces the Al recrystallization on SiO2 substrate. Even after an important Ti7Al5Si12 formation, the transmission electron microscopy results showed that a TiN layer is still present but probably ineffective from an electrical point of view. Although the 550 °C anneal produced important changes, no significant difference was observed between the XRD spectra after a 450 and a 500 °C anneal. The identified phases by the XRD analysis were in agreement with a calculated Al-Ti-O-N quaternary isotherm diagram.