Backside illuminated image sensor and manufacturing method thereof

A backside illuminated image sensor comprising:

• a substrate having a front surface and a back surface;
• a photoelectric conversion structure in the substrate, in a unit pixel of the backside illuminated image sensor;
• a wiring region comprising an interlayer insulation film on the front surface of the substrate and a metal wiring layer in the interlayer insulation film;
• an insulation film on the back surface of the substrate;
• a color filter on the insulation film;
• a planarization layer on the color filter;
• a lens on the planarization layer;
• and
• a light scattering portion having an upper surface at the back surface of the substrate, wherein the light scattering portion comprises:
• a center section having a first depth at a center of the unit pixel,
• wherein the center section does not contact the photoelectric conversion structure;
• and
• a plurality of side sections spaced apart from the center section along a lateral direction in the unit pixel, each of the plurality of side sections having a second depth greater than the first depth and a lowermost surface that contacts the photoelectric conversion structure.