Method for fabricating an air gap metallization scheme that reduces inter-metal capacitance of interconnect structures

Abstract

A method of manufacturing a metallization scheme with an air gap formed by vaporizing a filler polymer material. The filler material is covered by a critical permeable dielectric layer. The method begins by forming spaced conductive lines over a semiconductor structure. The spaced conductive lines have top surfaces. A filler material is formed over the spaced conductive lines and the semiconductor structure. The filler material is preferably comprised of a material selected from the group consisting of polypropylene glycol (PPG), polybutadine (PB) polyethylene glycol (PEG), fluorinated amorphous carbon and polycaprolactone diol (PCL) and is formed by a spin on process or a CVD process. We etch back the filler material to expose the top surfaces of the spaced conductive lines. Next, the semiconductor structure is loaded into a HDPCVD chamber. In a critical step, a permeable dielectric layer is formed over the filler material. The permeable dielectric layer has a property of allowing decomposed gas phase filler material to diffuse through. In another critical step, we vaporize the filler material changing the filler material into a vapor phase filler material. The vapor phase filler material diffuses through the permeable dielectric layer to form a gap between the spaced conductive lines. An insulating layer is formed over the permeable dielectric layer.