Study of FSG/SiO/sub 2/ double interlayer conditions to prevent Al wiring delamination for sub-0.18-/spl mu/m device integration

A double interlayer of high-density plasma fluorinated silica glass (FSG) and SiO/sub 2/ has been developed to control fluorine instability for sub-0.18-/spl mu/m devices. However, the interlayer conditions need further study for robust integration. The authors investigate the optimum conditions to prevent Al wiring delamination. The correlation between the incidence of delamination and F concentration at Ti-SiO/sub 2/ was demonstrated by the three-dimensional mapping of interfacial F concentrations with various thicknesses of SiO/sub 2/ and F contents in FSG. Detailed analysis of the Ti-SiO/sub 2/ interface reveals that the anomalous growth of the interface layer by absorbing F atoms into the Ti layer causes delamination. The properties of SiO/sub 2/, such as the compressive stress and the density of oxygen deficiency, were adjusted to reduce F diffusion. In addition, the thickness was controlled to above 4500 /spl Aring/ to suppress F accumulation at Ti-SiO/sub 2/ to within the permissible level. These conditions resulted in preventing delamination and obtaining integration reliability without increasing the capacitance between adjacent metal lines.