US Patent 7595554 Interconnect structure with dielectric air gaps

An interconnect structure with improved performance and capacitance by providing air gaps inside the dielectric layer by use of a multi-phase photoresist material. The interconnect features are embedded in a dielectric layer having a columnar air gap structure in a portion of the dielectric layer surrounding the interconnect features. The interconnect features may also be embedded in a dielectric layer having two or more phases with a different dielectric constant created. The interconnect structure is compatible with current back end of line processing.