| abstract |
A capping layer of an insulator such as silicon oxynitride is formed over horizontally closely spaced apart metal lines on an oxide layer of an integrated circuit structure formed on a semiconductor substrate. Low k silicon oxide dielectric material which exhibits void-free deposition properties in high aspect ratio regions between the closely spaced apart metal lines is then deposited over and between the metal lines and over the silicon oxynitride caps on the metal lines. After the formation of such void-free low k silicon oxide dielectric material between the closely spaced apart metal lines and the silicon oxynitride caps thereon, the structure is planarized to bring the level of the low k silicon oxide dielectric material down to the level of the tops of the silicon oxynitride caps on the metal lines. A further layer of standard k silicon oxide dielectric material is then formed over the planarized void-free low k silicon oxide dielectric layer and the silicon oxynitride caps. Vias are then formed through the standard k silicon oxide dielectric layer and the silicon oxynitride caps down to the metal lines. Since the vias are not formed through the low k silicon oxide dielectric material, formation of the vias does not contribute to poisoning of the vias. However, the presence of the low k silicon oxide dielectric material between the horizontally closely spaced apart metal lines reduces the horizontal capacitance between such metal lines. |