Image sensor and method for manufacturing the same

An apparatus comprising:

• a photodiode arranged over a semiconductor substrate;
• a core layer for an optical waveguide, to guide incident light toward the photodiode, the core layer arranged over the photodiode;
• and
• a dielectric layer serving as a clad layer for the optical waveguide, having a refractive index lower than a refractive index of the core layer, to reflect the incident light to the photodiode, the clad layer being arranged over a side of the core layer.

A method comprising:

• forming a photodiode over a semiconductor substrate;
• forming a dielectric layer over the semiconductor substrate including the photodiode;
• forming a photosensitive film mask over the dielectric layer to expose an optical waveguide region;
• etching the dielectric layer using the photosensitive film mask as an etching mask to form an opening to expose the photodiode;
• forming a clad layer of the optical waveguide, having a first refractive index, such that the clad layer exposes the top of the photodiode and covers an inner wall of the opening;
• and
• forming a core layer for the optical waveguide, having a second refractive index higher than the first refractive index, over the top of the photodiode and the clad layer.

A method comprising:

• forming a photodiode over a semiconductor substrate;
• forming a dielectric layer having a first refractive index as a clad layer over the semiconductor substrate including the photodiode;
• forming a photosensitive film mask over the dielectric layer to expose an optical waveguide region;
• etching the dielectric layer using the photosensitive film mask as an etching mask to form an opening to expose the photodiode;
• and
• filling the opening with a core layer for the optical waveguide, the core layer having a second refractive index higher than the first refractive index.