QE approach by double-side, multi absorption structure

An integrated chip, comprising:

• a semiconductor substrate comprising a first side and a second side;
• a plurality of pixel regions arranged in an array within the substrate, wherein each pixel region comprises:
• a light sensing element disposed between the first side of the substrate and the second side of the substrate;
• an absorption enhancement structure arranged over the light sensing element and along the first side of the substrate, the absorption enhancement structure comprising a plurality of protrusions extending outwardly from the first side of the substrate;
• a reflection structure along the second side of the substrate under the light sensing element, wherein the reflection structure comprises a plurality of semiconductor pillars configured to reflect incident light that has passed through the absorption enhancement structure and through the light sensing element back towards the light sensing element.

An integrated chip, comprising:

• a semiconductor substrate comprising a front-side and a back-side;
• a light sensing element arranged within the substrate between the front-side and the back-side;
• an absorption enhancement structure comprising a plurality of protrusions along the back-side of the substrate;
• a color filter element disposed over the absorption enhancement structure;
• a microlens disposed over the color filter element;
• an interconnect structure disposed along the front-side of the substrate, the interconnect structure separated from the absorption enhancement structure by the light sensing element;
• and
• a reflection structure along the front-side of the substrate and spaced between the light sensing element and the interconnect structure, the reflection structure comprising a plurality of semiconductor pillars which extend from the front-side of the substrate and which matingly engage corresponding depressions in a dielectric structure along the front-side of the substrate, the plurality of semiconductor pillars collectively configured to reflect incident light that has passed through the absorption enhancement structure and through the light sensing element back towards the light sensing element.