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
norbornene-type polymer is used as a sacrificial material to occupy a
closed interior volume in a semiconductor structure. The sacrificial
material is caused to decompose into one or more gaseous decomposition
products which are removed, preferably 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
norbornene-type polymer. The air gaps may be disposed between electrical
leads to minimize capacitive coupling therebetween.