Optical integrated circuit structure including edge coupling protective features and methods of forming same

An optical integrated circuit (IC) structure comprising:

• a substrate comprising a fiber slot formed in an upper surface of the substrate and extending from an edge of the substrate, and an undercut formed in the upper surface and extending from the fiber slot, wherein the undercut comprises an undercut top surface, an undercut bottom surface, and an undercut side surface, and the fiber slot comprises a fiber slot bottom surface and a fiber slot sidewall surface;
• a semiconductor layer disposed on the substrate;
• a dielectric structure disposed on the semiconductor layer;
• an interconnect structure disposed in the dielectric structure;
• a plurality of vents that extend through a coupling region of the dielectric structure, wherein the plurality of vents each expose the undercut and comprise vent sidewall surfaces;
• a fiber cavity that extends through the coupling region of the dielectric structure and exposes the fiber slot, wherein the fiber cavity comprises a fiber cavity sidewall surface;
• and
• a barrier layer disposed on the vent sidewall surfaces of the plurality of vents, the undercut top surface, the undercut bottom surface, the undercut side surface, the fiber cavity sidewall surface, the fiber slot bottom surface and the fiber slot sidewall surface.

A method of forming an optical integrated circuit (IC) structure, comprising:

• forming a dielectric structure comprising an interconnect structure and a barrier ring, on a semiconductor layer disposed on a substrate;
• performing a first etching process to form a plurality of vents and a fiber cavity in a coupling region of the dielectric structure, so as to expose portions of the substrate;
• performing a second etching process to etch the substrate and form an undercut below the plurality of vents and the fiber cavity;
• and
• performing a third etching process to etch the substrate and form a fiber slot below the fiber cavity,
• wherein the barrier ring surrounds the interconnect structure and is disposed between the coupling region and the interconnect structure.