On-chip graded index of refraction optical waveguide and damascene method of fabricating the same

This invention relates to optical waveguides formed in integrated circuit (IC)-like structures and positioned in interconnect layers of the IC-like structure. More particularly, this invention relates to a new and improved optical waveguide formed with a graded index of refraction in an IC-like structure. In addition, the present invention relates to a new and improved method of fabricating a graded index of refraction waveguide in an IC-like structure using damascene fabrication process steps that are typically employed in the fabrication of electrical integrated circuits. A graded index of refraction optical waveguide is formed in interlayer dielectric material located above a substrate an integrated circuit-like structure. The waveguide includes a refractive layer of optically transmissive material surrounding a core of optically transmissive material within a trench in the dielectric material. The material of the core has a higher index of refraction than the refractive layer and the material of the refractive layer has a higher index of refraction than the dielectric material. More than one refractive layer may also be formed in the trench, with the inner refractive layer having an index of refraction higher than the outer refractive layer and less than the core.