| abstract |
A semiconductor structure includes a conductive metal layer having provided thereover in succession a silicon nitride layer, a dielectric layer, and another silicon nitride layer. An aluminum layer is deposited over the silicon nitride layer. The aluminum layer is selectively anodized so that a top portion of porous aluminum oxide is formed over the remaining aluminum. A reactive ion etch is undertaken through the pores of the aluminum oxide to render the remaining aluminum and silicon nitride layer therebelow porous. The aluminum oxide and aluminum are removed, and the remaining porous silicon nitride layer is used as a template or mask for further reactive ion etching therethrough to the dielectric layer, so that the dielectric layer is rendered porous, thereby lowering its dielectric constant. As an alternative, reactive ion etching of the dielectric can be undertaken with the porous aluminum oxide layer and porous aluminum layer in place. The etching characteristics of the reactive ion etch step for rendering the dielectric layer porous may be varied so that air gaps rather than pores are formed in the dielectric. |