Image sensor including a double-sided spherical lens

1. An image sensor, comprising:

a substrate which has a first surface and a second surface opposite to the first surface and pixels arranged in a two-dimensional array, wherein each of the pixels comprises a photodiode (PD);

a multi-wiring layer arranged on the first surface of the substrate;

a color filter layer arranged on the second surface of the substrate and comprising color filters that respectively correspond to the pixels; and

a lens layer arranged on the color filter layer and comprising a double-sided spherical lens,

wherein the double-sided spherical lens comprises at least two material layers having different refractive indexes,

wherein the double-sided spherical lens comprises a lower spherical lens, an upper spherical lens, and an intermediate lens having a flat plate shape and arranged between the lower spherical lens and the upper spherical lens,

a refractive index of the lower spherical lens is greater than a refractive index of the upper spherical lens, and

the intermediate lens has a uniform thickness and has a refractive index between the refractive index of the lower spherical lens and the refractive index of the upper spherical lens,

wherein the lens layer further comprises a planarization lens layer adjacent to the lower spherical lens, and

the double-sided spherical lens further comprises a cover lens having a uniform thickness and covering the upper spherical lens,

wherein a refractive index of the cover lens is less than a refractive index of the planarization lens layer, and the refractive index of the upper spherical lens is greater than that of the planarization lens layer.

2. The image sensor of claim 1 , wherein the planarization lens layer is between the double-sided spherical lens and the color filter layer, and

a top surface of the planarization lens layer has recesses, each of which is recessed to correspond to a surface of the double-sided spherical lens.

3. The image sensor of claim 1 , wherein the planarization lens layer is between the double-sided spherical lens and the color filter layer.

4. The image sensor of claim 1 , wherein a diameter of a bottom surface of the upper spherical lens is less than a diameter of a top surface of the lower spherical lens, and

an outer diameter of a bottom surface of the cover lens is substantially equal to the diameter of the top surface of the lower spherical lens.

5. The image sensor of claim 1 , wherein

a curvature of the lower spherical lens is different from a curvature of the upper spherical lens.

6. The image sensor of claim 1 , wherein the color filters are separated from each other by metal grids, and

the pixels are separated from each other by pixel separation structures.

7. The image sensor of claim 1 , wherein the double-sided spherical lens includes at least two of polyimide, Al 2 O 3 , SiN, SiON, SiO, SiO 2 , HfOx, and TiO 2 .

8. The image sensor of claim 7 , wherein the planarization lens layer is below the double-sided spherical lens, and

the lower spherical lens, the intermediate lens, the upper spherical lens, and the cover lens are arranged in this order on the planarization lens layer,

wherein the planarization lens layer includes polyimide or SiO 2 , the lower spherical lens includes one of polyimide, SiN, SiO, SiON, HfOx, and TiO 2 , the upper spherical lens includes one of polyimide, SiO 2 , and Al 2 O 3 , and the cover lens includes polyimide.

9. An image sensor, comprising:

a substrate which has a first surface and a second surface opposite to the first surface and pixels arranged in a two-dimensional array, wherein each of the pixels includes a photodiode;

a multi-wiring layer arranged on the first surface of the substrate;

a color filter layer arranged on the second surface of the substrate and comprising color filters that respectively correspond to the pixels;

a planarization lens layer arranged on the color filter layer; and

a double-sided spherical lens arranged on the planarization lens layer and protruding upward and downward,

wherein the double-sided spherical lens comprises a lower spherical lens and an upper spherical lens, and

a refractive index of the planarization lens layer is less than a refractive index of the upper spherical lens, and the refractive index of the upper spherical lens is less than a refractive index of the lower spherical lens,

wherein the double-sided spherical lens further comprises: a cover lens having a uniform thickness and covering the upper spherical lens; and an intermediate lens having a uniform thickness and, disposed between the upper spherical lens and the lower spherical lens and between the cover lens and the lower spherical lens,

wherein a refractive index of the cover lens is less than the refractive index of the planarization lens layer.

10. The image sensor of claim 9 , wherein a diameter of a bottom surface of the upper spherical lens is less than a diameter of a top surface of the lower spherical lens, and

an outer diameter of a bottom surface of the cover lens is substantially equal to the diameter of the top surface of the lower spherical lens.

11. The image sensor of claim 9 , wherein a curvature of the lower spherical lens is different from a curvature of the upper spherical lens.

12. The image sensor of claim 9 , wherein the planarization lens layer and the double-sided spherical lens include at least three of polyimide, Al 2 O 3 , SiN, SiON, SiO, SiO 2 , HfOx, and TiO 2 .

13. An image sensor, comprising:

a substrate which has a first surface and a second surface opposite to the first surface and pixels arranged in a two-dimensional array, wherein each of the pixels comprises a photodiode;

a wiring layer arranged on the first surface of the substrate;

a color filter layer arranged on the second surface of the substrate and comprising color filters that respectively correspond to the pixels; and

a double-sided spherical lens arranged on the color filter layer, wherein a refractive index of a first lens of the double-sided spherical lens is less than a refractive index of a second lens of the double-sided lens,

wherein the double-sided spherical lens includes at least two of polyimide, Al 2 O 3 , SiN, SiON, SiO, SiO 2 , HfOx and TiO 2 ,

wherein the lens layer further comprises a planarization lens layer between the double-sided lens and the color filter layer, an intermediate lens between the first lens and the second lens and a cover lens on the first lens,

wherein the planarization lens layer includes polymide or SiO 2 , the second lens includes one of polyimide, SIN, SiO, SiON, HfOx, and TiO 2 , the first lens includes one of polymide, SiO 2 , and Al 2 O 3 , and the cover lens includes polyimide, and

the intermediate lens includes a material having a refractive index between a refractive index of the first lens and a refractive index of the second lens.

14. The image sensor of claim 13 , wherein a refractive index of the planarization layer is less than the refractive index of the second lens of the double-sided lens.

15. The image sensor of claim 14 , wherein the planarization layer comprises a recess in which the first lens of the double-sided lens is disposed.

16. The image sensor of claim 14 , wherein the second lens protrudes away from the planarization layer and the first lens protrudes toward the planarization layer.