Inserted reflective shield to improve quantum efficiency of image sensors

An image sensor device using backside illumination with an inserted reflective shield to increase quantum efficiency, comprising:

• a photodiode disposed near a front surface of a substrate;
• and
• a reflective shield disposed directly above the photodiode, wherein
• the reflective shield is embedded within a dielectric layer deposited directly over the photodiode,
• the reflective shield has a concave surface facing the photodiode,
• the photodiode is adapted to receive light from a back surface of the substrate,
• the back surface and the reflective shield are on opposite sides of the photodiode, and
• the reflective shield is adapted to reflect a photon coming from the back surface of the substrate that passes through the photodiode to re-enters the photodiode.

A method of creating a reflective shield for an image sensor device, comprising:

• providing a substrate with photodiode on the substrate;
• depositing a first dielectric layer on the substrate, wherein the first dielectric layer is in contact with the photodiode;
• removing surface topography of the substrate by performing chemical mechanical polishing (CMP) on the first dielectric layer;
• patterning the substrate to define an area on a surface of the first dielectric layer after CMP for the reflective shield, wherein the area defined for the reflective shield is directly above the photodiode;
• depositing a layer of a material with high reflectivity on the substrate after patterning the substrate, wherein the material with high reflectivity fills the area on the surface of the first dielectric layer;
• removing excess material with high reflectivity after the layer of the material with high reflectivity is deposited, wherein the reflective shield is formed and is embedded in the first dielectric layer;
• and
• depositing a second dielectric material on the substrate, wherein the second dielectric material covers the reflective shield.