Thermal stability and nitrogen redistribution in the <Si)/Ti/W-N/ AI metallization scheme

Backscattering spectrometry, Auger electron spectroscopy, and x-ray diffraction have been used to monitor the thin-film reactions and nitrogen redistribution in the (Si)/Ti!W-N/Al metallization system. It is found that nitrogen in the W-N layer redistributes into Ti after annealing at temperatures above 500 oc. As a consequence of this redistribution of nitrogen, a significant amount ofinterdiffusion between AI and the underlayers is observed after annealing at 550 oc. This result contrasts markedly with that for the (Si)/W-N/ AI system, where no interdiffusion can be detected after the same thermal treatment. We attribute this redistribution of nitrogen to the stronger affinity ofTi for nitrogen than W. If the Ti layer is replaced by a sputtered TiSi2 3 film, no redistribution of nitrogen or reactions can be detected after annealing at 550 oc for 30min.