Fabrication of semiconductor device with air gaps for ultra low capacitance interconnections and methods of making same

The invention herein described relates generally to the fabrication of semiconductor devices and more specifically to such devices that use air gaps and/or multi-level air gaps to reduce capacitive coupling between conductors in such devices. Additionally, the invention herein described relates to the fabrication of semiconductor devices which can contain overcoated conductive lines or leads which are at least partially adjacent to one or more air gaps. 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.