CN-121793475-B - Image sensor and method of forming the same

CN121793475BCN 121793475 BCN121793475 BCN 121793475BCN-121793475-B

Abstract

The technical scheme of the application discloses an image sensor and a forming method thereof, wherein the image sensor comprises a substrate, a grid structure positioned on the isolation region, and a composite structure positioned on the top of the grid structure, wherein the image sensor comprises a plurality of photosensitive regions and isolation regions positioned between the photosensitive regions, the composite structure comprises at least two light absorption layers and a spacing layer positioned between adjacent light absorption layers, the at least two light absorption layers are laminated along the direction vertical to the surface of the substrate, and the dimension of the composite structure in the direction vertical to the surface of the substrate is reduced from the center to the edge of the composite structure. The light reflection at the top of the grid structure can be weakened through the convergence and absorption of the composite structure to light, so that the noise problem of the image sensor is solved, and the imaging effect is improved.

Inventors

WANG ZHIWEI
DU ZHI
MA ZHONGXIANG
XIE RONGYUAN

Assignees

合肥晶合集成电路股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260306

Claims (14)

1. An image sensor is provided, which is capable of detecting a light source, characterized by comprising the following steps: A substrate including a plurality of photosensitive regions and an isolation region between the plurality of photosensitive regions; a grid structure located on the isolation region; the composite structure comprises a first light absorption layer, a second light absorption layer and a spacing layer which are stacked along a first direction perpendicular to the surface of the substrate, wherein the spacing layer is positioned between the first light absorption layer and the second light absorption layer, the thickness of the composite structure in the first direction is reduced from the center to the edge of the composite structure, the thickness of the second light absorption layer in the first direction is reduced from the center to the edge of the composite structure, and the distance from the first light absorption layer to the grid structure is smaller than the distance from the second light absorption layer to the grid structure.
2. The image sensor of claim 1, wherein the second light absorbing layer includes a first face and a second face that is closer to the grid structure than the first face, and wherein the first face protrudes arcuately relative to the second face in a direction away from the substrate surface.
3. The image sensor of claim 2, wherein the first face has a radius of curvature in the range of 2 microns to 5 microns.
4. The image sensor of claim 1, wherein the thickness of the first light absorbing layer decreases in the first direction from the center to the edge of the composite structure.
5. The image sensor of claim 4, wherein the first light absorbing layer includes a third face and a fourth face farther from the grid structure than the third face, and the third face protrudes arcuately with respect to the fourth face in a direction toward the substrate surface.
6. The image sensor of claim 5, wherein the third face has a radius of curvature in the range of 2 microns to 5 microns.
7. The image sensor of claim 3, wherein the composite structure further comprises at least one third light absorbing layer positioned between the first light absorbing layer and the second light absorbing layer, the at least one third light absorbing layer, the first light absorbing layer, and the second light absorbing layer being stacked along the first direction.
8. The image sensor of claim 1, wherein the grid structure comprises a first region and a second region, the grid structure of the first region having a first width, the grid structure of the second region having a second width, and the first width being greater than the second width, the composite structure being located on a side of the grid structure of the first region facing away from the substrate.
9. The image sensor of claim 8, wherein the first width is in the range of 1 micron to 2 microns.
10. The image sensor of claim 1, wherein the material of the first light absorbing layer comprises titanium, tungsten, or silicon oxynitride, the material of the second light absorbing layer comprises titanium, tungsten, or silicon oxynitride, and the material of the spacer layer comprises an oxide.
11. The image sensor of claim 1, wherein the substrate comprises a first functional surface and a second functional surface opposite to each other, the grid structure is located on a surface of the first functional surface, the image sensor further comprises a device layer located on the second functional surface, the device layer comprises a logic device, the photoelectric doping region is located in the photosensitive region, the filter layer is located on the first functional surface of the photosensitive region, and the lens structure is located on a side of the filter layer away from the substrate.
12. A method of forming an image sensor as claimed in any one of claims 1 to 11, comprising: providing a substrate, wherein the substrate comprises a plurality of photosensitive areas and isolation areas positioned among the plurality of photosensitive areas; Forming a grid structure on the isolation region; And forming a composite structure on one side of the grid structure, which is far away from the substrate, wherein the composite structure comprises a first light absorption layer, a second light absorption layer and a spacing layer which are laminated along a first direction perpendicular to the surface of the substrate, the spacing layer is positioned between the first light absorption layer and the second light absorption layer, and the thickness of the composite structure in the first direction is reduced from the center to the edge of the composite structure.
13. The method of forming an image sensor of claim 12, wherein the forming a grid structure on the isolation region comprises forming an initial grid structure on the isolation region, forming a first patterned layer on the photosensitive region, the first patterned layer exposing the initial grid structure, etching a top surface of the initial grid structure with the first patterned layer as a mask to form the grid structure, the grid structure comprising opposing first and second end surfaces, the first end surface being spaced from the substrate by a distance less than the second end surface, and the second end surface being arcuately recessed in a direction of the first end surface.
14. The method of forming an image sensor of claim 12, wherein the method of forming the composite structure includes forming a first light absorbing layer on a top surface of the grid structure, forming an initial spacer layer on the first light absorbing layer, patterning the initial spacer layer to form a spacer layer on the first light absorbing layer, forming a second light absorbing material layer on a surface of the spacer layer, patterning the second light absorbing material layer on the spacer layer, the second light absorbing layer having a thickness in the first direction that decreases from a center to an edge of the composite structure, the second light absorbing layer including opposing first faces and a second face that is closer to the grid structure than the first faces, and the first faces protruding arcuately in a direction away from the substrate surface than the second faces.

Description

Image sensor and method of forming the same Technical Field The present disclosure relates to semiconductor devices and manufacturing techniques, and more particularly, to an image sensor and a method for forming the same. Background An image sensor is a semiconductor device that converts an optical signal into an electrical signal. Image sensors are classified into CMOS (Complementary Metal-Oxide-Semiconductor) image sensors and CCD (Charge-Coupled Device) image sensors. The CMOS image sensor (CMOS Image Sensor, CIS for short) has the advantages of simple process, easy integration of other devices, small volume, light weight, low power consumption, low cost and the like. Therefore, with the development of image sensing technology, CMOS image sensors are increasingly being used in various electronic products instead of CCD image sensors. CMOS image sensors include Front-lit (FSI for short) image sensors and Back-lit (BSI for short) image sensors. In a back-illuminated image sensor, light is incident on a photodiode in the image sensor from the back side of the image sensor, thereby converting an optical signal into an electrical signal. However, with the increase of the integration level of devices, the influence of optical crosstalk in the image sensor is increasingly severe, which is one of the problems to be solved in the industry. Disclosure of Invention The technical scheme of the application provides an image sensor and a forming method thereof, which improves the absorptivity of light rays with specific incidence angles among pixel units so as to at least partially weaken the problem of optical crosstalk. In order to achieve the above object, according to the technical scheme of the application, the image sensor comprises a substrate, a grid structure located on the isolation region, and a composite structure located on one side of the grid structure away from the substrate, wherein the composite structure comprises a first light absorption layer, a second light absorption layer and a spacing layer which are stacked along a first direction perpendicular to the surface of the substrate, the spacing layer is located between the first light absorption layer and the second light absorption layer, and the thickness of the composite structure in the first direction is reduced from the center to the edge of the composite structure. In some embodiments, the first light absorbing layer is less distant from the grid structure than the second light absorbing layer, and the second light absorbing layer has a thickness in the first direction that decreases from the center to the edge of the composite structure. In some embodiments, the second light absorbing layer includes a first face and a second face that is closer to the grid structure than the first face, and the first face protrudes arcuately relative to the second face in a direction away from the substrate surface. In some embodiments, the first face has a radius of curvature in the range of 2 microns to 5 microns. In some embodiments, the thickness of the first light absorbing layer decreases in the first direction from the center to the edge of the composite structure. In some embodiments, the first light absorbing layer includes a third face and a fourth face farther from the grid structure than the third face, and the third face protrudes arcuately with respect to the fourth face in a direction toward the substrate surface. In some embodiments, the third face has a radius of curvature in the range of 2 microns to 5 microns. In some embodiments, the composite structure further comprises at least one third light absorbing layer positioned between the first light absorbing layer and the second light absorbing layer, the at least one third light absorbing layer, the first light absorbing layer, and the second light absorbing layer being laminated along the first direction. In some embodiments, the grating structure comprises a first region and a second region, the grating structure of the first region having a first width, the grating structure of the second region having a second width, and the first width being greater than the second width, the composite structure being located on a side of the grating structure of the first region facing away from the substrate. In some embodiments, the first width ranges from 1 micron to 2 microns. In some embodiments, the material of the first light absorbing layer comprises titanium, tungsten, or silicon oxynitride, the material of the second light absorbing layer comprises titanium, tungsten, or silicon oxynitride, and the material of the spacer layer comprises an oxide. In some embodiments, the substrate comprises a first functional surface and a second functional surface which are opposite, the grid structure is positioned on the surface of the first functional surface, the image sensor further comprises a device layer positioned on the second functional surface, the device layer comprises a logic device, a phot