Backside illumination image sensor and image-capturing device
A backside illumination image sensor that includes a semiconductor substrate with a plurality of photoelectric conversion elements and a read circuit formed on a front surface side of the semiconductor substrate, and captures an image by outputting, via the read circuit, electrical signals generated as incident light having reached a back surface side of the semiconductor substrate is received at the photoelectric conversion elements includes: a light shielding film formed on a side where incident light enters the photoelectric conversion elements, with an opening formed therein in correspondence to each photoelectric conversion element; and an on-chip lens formed at a position set apart from the light shielding film by a predetermined distance in correspondence to each photoelectric conversion element. The light shielding film and an exit pupil plane of the image forming optical system achieve a conjugate relation to each other with regard to the on-chip lens.
1. A backside illumination image sensor, comprising:
a plurality of pairs of photoelectric conversion elements each including a pair of light receiving areas that receive incident light having entered a back surface of a semiconductor substrate through an image forming optical system, a read circuit being formed on a front surface of the semiconductor substrate;
an on-chip lens formed at a position set apart from the pair of light receiving areas;
a barrier member that is disposed parallel to an optical axis of the on-chip lens, between the on-chip lens and the pair of light receiving areas;
a first separating area that is constituted with a type of semiconductor and that separates unit pixel areas from each other, each of the unit pixel areas including each pair of photoelectric conversion elements; and
a second separating area that is constituted with the type of semiconductor and that forms a boundary between the each pair of photoelectric conversion elements.
2. A backside illumination image sensor according to claim 1 , wherein:
an anti-reflection film is formed at a surface of the barrier member.
3. A backside illumination image sensor according to claim 1 , wherein:
a radius of curvature R of the on-chip lens, a distance D from an apex of the on-chip lens to the pair of light receiving areas and an average refractive index n of a medium present between the on-chip lens and the pair of light receiving areas achieve a relationship expressed as:
D=R·n /( n− 1).
4. A backside illumination image sensor according to claim 3 , wherein:
the plurality of pairs of photoelectric conversion elements are disposed in a two-dimensional grid array; and
a pitch P of the two-dimensional grid array, a smallest F number FO of an exit pupil of the image forming optical system and the distance D achieve a relationship expressed as:
FO·P·n>D>P·n /(2−( n− 1)).
5. A backside illumination image sensor according to claim 4 , wherein:
the radius of curvature over a periphery of the on-chip lens is greater than the radius of curvature at a central area of the on-chip lens.
6. A backside illumination image sensor, comprising:
a plurality of pairs of photoelectric conversion elements each including a pair of light receiving areas that receive incident light having entered a back surface of a semiconductor substrate through an image forming optical system, a read circuit being formed on a front surface of the semiconductor substrate;
an on-chip lens formed at a position set apart from the pair of light receiving areas by a predetermined distance;
a first separating area that is constituted with a type of semiconductor and that separates unit pixel areas from each other, each of the unit pixel areas including each pair of photoelectric conversion elements; and
a second separating area that is constituted with the type of semiconductor and that forms a boundary between the each pair of photoelectric conversion elements, wherein:
a radius of curvature R of the on-chip lens, a distance D from an apex of the on-chip lens to the pair of light receiving areas and an average refractive index n of a medium present between the on-chip lens and the pair of light receiving areas achieve a relationship expressed as:
D=R·n /( n− 1).
7. A backside illumination image sensor according to claim 6 , wherein:
the plurality of pairs of photoelectric conversion elements are disposed in a two-dimensional grid array; and
a pitch P of the two-dimensional grid array, a smallest F number FO of an exit pupil of the image forming optical system and the distance D achieve a relationship expressed as:
FO·P·n>D>P·n /(2·( n− 1)).
8. A backside illumination image sensor according to claim 7 , wherein:
the radius of curvature over a periphery of the on-chip lens is greater than the radius of curvature at a central area of the on-chip lens.
9. A backside illumination image sensor according to claim 6 , further comprising:
a light shielding member that is disposed between the on-chip lens and the pair of light receiving areas and that includes a first color filter disposed near the on-chip lens and a second color filter assuming a color matching the color of the first color filter, which is disposed near the pair of light receiving areas, wherein:
the color of the first color filter is different from a color of the second color filter disposed in conjunction with an adjacent on-chip lens adjacent to the on-chip lens.
10. A backside illumination image sensor according to claim 6 , further comprising:
a light shielding member that is disposed between the on-chip lens and the pair of light receiving areas and that includes a first polarizer disposed near the on-chip lens and a second polarizer assuming a polarizing direction matching the polarizing direction of the first polarizer, which is disposed near the pair of light receiving areas, wherein:
the polarizing direction of the first polarizer is perpendicular to a polarizing direction of the second polarizer disposed in conjunction with an adjacent on-chip lens adjacent to the on-chip lens.