A method of forming an air gap or gaps within solid structures and specifically
semiconductor structures to reduce capacitive coupling between electrical elements
such as metal lines, wherein a sacrificial material is used to occupy a closed
interior volume in a semiconductor structure is disclosed. The sacrificial material
is caused to decompose into one or more gaseous decomposition products which are
removed, in one embodiment by diffusion, through an overcoat layer. The decomposition
of the sacrificial material leaves an air gap or gaps at the closed interior volume
previously occupied by the sacrificial material. The air gaps may be disposed between
electrical leads to minimize capacitive coupling therebetween. Also disclosed are
methods of forming multi-level air gaps and methods or forming over-coated conductive
lines or leads wherein a portion of the overcoating is in contact with at least
one air gap.
