US 12,439,719 B2
CMOS image sensor
Liusuo Cheng, Wuxi (CN); Guanglong Chen, Wuxi (CN); Han Wang, Wuxi (CN); Jiliang Zhang, Wuxi (CN); and Jiangyong Qian, Wuxi (CN)
Assigned to Hua Hong Semiconductor (Wuxi) Limited, Wuxi (CN)
Filed by Hua Hong Semiconductor (Wuxi) Limited, Wuxi (CN)
Filed on Mar. 16, 2022, as Appl. No. 17/696,700.
Claims priority of application No. 202110344989.8 (CN), filed on Mar. 31, 2021.
Prior Publication US 2022/0320171 A1, Oct. 6, 2022
Int. Cl. H10F 39/00 (2025.01); H10F 39/18 (2025.01)
CPC H10F 39/8063 (2025.01) [H10F 39/18 (2025.01); H10F 39/8037 (2025.01); H10F 39/807 (2025.01); H10F 39/811 (2025.01)] 12 Claims
OG exemplary drawing
 
1. A CMOS image sensor, wherein:
a pixel region of the CMOS image sensor comprises a plurality of pixel units, each of the pixel units comprises a photodiode, and each of the photodiodes is formed on a semiconductor substrate;
incident light is incident onto the photodiode from a first surface of the semiconductor substrate;
a first dielectric layer is formed on the first surface of the semiconductor substrate, and the first dielectric layer has a first refractive index;
a plurality of lower microlenses are formed in the first dielectric layer, the bottom surface of the lower microlens has an arc concave structure, the material of the lower microlens has a second refractive index, and each of the lower microlenses is located directly above the corresponding photodiode;
a plurality of upper microlenses are formed on the top surface of the first dielectric layer, the top surface of the upper microlens has an arc convex structure, the material of the upper microlens has a third refractive index, and each of the upper microlenses is located directly above the corresponding lower microlens;
the third refractive index is greater than the second refractive index, and the second refractive index is greater than the first refractive index; and
the upper microlens and the lower microlens form a composite microlens on a path of the incident light, and the composite microlens increases an incident angle of the incident light incident onto the photodiode;
the top surface of the lower microlens is flush with the top surface of the first dielectric layer, the bottom surface of the upper microlens is flush with the top surface of the first dielectric layer, and the top surface of the lower microlens is in contact with the bottom surface of the upper microlens;
the top surface of the lower microlens and the bottom surface of the upper microlens are equal in size and completely aligned;
center lines of the composite microlens, the incident channel, and the photodiode are aligned;
the top surface of the upper microlens has a circular arc shape;
the side surface of the top part of the lower microlens is perpendicular to the top surface of the top part of the lower microlens;
the bottom surface of the bottom part of the lower microlens is in the shape of a circular arc;
the radius of the bottom surface of the bottom part of the lower microlens is greater than the radius of the top surface of the upper microlens.