US-12622075-B2 - Backside-illuminated image sensor and method of manufacturing same

US12622075B2US 12622075 B2US12622075 B2US 12622075B2US-12622075-B2

Abstract

A backside-illuminated image sensor and a method of manufacturing the same are disclosed. The backside-illuminated image sensor is capable of improving sensitivity by including a scattering layer in a substrate that may result in incident light having a path greater than the thickness of the substrate and, simultaneously, of additionally enhancing light sensitivity with respect to a specific wavelength or wavelength band of light passing through one of a plurality of different color filters by a varying depth or thickness of the scattering layer for each unit pixel in the image sensor.

Inventors

Woo Sung Choi
Man Lyun HA

Assignees

DB HITEK CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20221216
Priority Date: 20220119

Claims (13)

1 . A backside-illuminated image sensor comprising: a substrate comprising a front surface and a rear surface and a plurality of unit pixels, the plurality of unit pixels comprising first pixels configured to receive blue light, second pixels configured to receive green light, and third pixels configured to receive red light; a light receiving element at or on the front surface of the substrate in each of the plurality of unit pixels; a deep trench isolation (DTI) region in the substrate and at a boundary between adjacent ones of the plurality of unit pixels; a scattering layer in the substrate comprising a first scattering structure in each of the first pixels, a second scattering structure in the substrate and in each of the second pixels, and a third scattering structure in the substrate and in each of the third pixels, wherein each of the first, second and third scattering structures scatter and reflect incident light and have side walls perpendicular to the front surface and the rear surface of the substrate; a blue color filter on the rear surface of the substrate in each of the first pixels, a green color filter on the rear surface of the substrate in each of the second pixels, and a red color filter on the rear surface of the substrate in each of the third pixels; and a lens on each of the blue, green and red color filters, wherein the first scattering structure has a first thickness, the second scattering structure has a second thickness greater than the first thickness, the third scattering structure has a third thickness greater than the second thickness, and the DTI region reflects the incident light scattered by and the incident light reflected by an adjacent one of the first, second and third scattering structures into one of the unit pixels containing the adjacent one of the first, second and third scattering structures and toward the light receiving element.
2 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures extends from the rear surface of the substrate, or a depth adjacent to the rear surface, toward the front surface of the substrate.
3 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures is in a center of the unit pixel.
4 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures has a width smaller than a gap or distance between adjacent DTI regions.
5 . The backside-illuminated image sensor of claim 1 , further comprising: one or more wiring levels on the front surface of the substrate, wherein each wiring level comprises: a metal wiring layer; and an insulation layer covering the metal wiring layer.
6 . The backside-illuminated image sensor of claim 1 , wherein the first scattering structure, the second scattering structure, and the third scattering structure are formed by etching the rear surface of the substrate using separate etching processes.
7 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures comprises a silicon oxide film, a metal film, or a polysilicon film.
8 . The backside-illuminated image sensor of claim 1 , wherein the DTI region comprises one or more films comprising a borophosphosilicate glass (BPSG), a phosphosilicate glass (PSG), a borosilicate glass (BSG), an undoped silicate glass (USG), a silicon dioxide derived from tetraethyl orthosilicate (TEOS), and/or a high-density plasma (HDP)-deposited film derived from silane.
9 . The backside-illuminated image sensor of claim 8 , wherein each of the first, second and third scattering structures includes a same material as the DTI region.
10 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures includes a same material as the DTI region.
11 . The backside-illuminated image sensor of claim 1 , wherein the third thickness is more than half of a thickness of the substrate.
12 . The backside-illuminated image sensor of claim 1 , wherein each of the first thickness, the second thickness, and the third thickness is sufficient for each of the first scattering structure, the second scattering structure and the third scattering structure to scatter incident light and to reflect incident light reflected by the DTI region at least once.
13 . The backside-illuminated image sensor of claim 12 , wherein each of the second thickness and the third thickness is sufficient for each of the second scattering structure and the third scattering structure to reflect incident light reflected by the DTI region at least twice.

Description

CROSS REFERENCE TO RELATED APPLICATION The present application claims priority to Korean Patent Application No. 10-2022-0007669, filed Jan. 19, 2022, the entire contents of which are incorporated herein for all purposes by this reference. BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates generally to a backside-illuminated image sensor and a method of manufacturing the same. More particularly, the present disclosure relates to a backside-illuminated image sensor and a method of manufacturing the same, the backside-illuminated image sensor being capable of improving sensitivity by including a scattering layer in a substrate that may result in incident light having a path length greater than the thickness of the substrate and, simultaneously, of enhancing light sensitivity with respect to a specific wavelength or wavelength band of light passing through one of a plurality of different color filters by varying a depth or thickness of the scattering layer for each unit pixel in the image sensor. Description of the Related Art An image sensor is a part of an image capturing device that generates an image from a mobile phone camera, etc. According to the manufacturing process and application method, image sensors may be classified into charge coupled device (CCD) image sensors and a complementary metal oxide semiconductor (CMOS) image sensors. Among the sensors, the CMOS image sensor is widely used in the general semiconductor chip manufacturing process due to its excellent integrability, economic feasibility, and ease of connection with peripheral chips. Conventionally, the CMOS image sensor includes wiring, a color filter, and a lens in sequence on a surface of a silicon wafer. However, in the image sensor having the above described structure, the amount of incident light received by a light receiving element in the image sensor may be reduced by individual metal wires in the wiring. Accordingly, a backside-illuminated CMOS image sensor (BIS), having a structure in which the wiring is on the front surface of the substrate and the color filter and lenses are on the rear surface of the substrate, is being developed. The backside-illuminated CMOS image sensor is applied in various devices such as an iris scanner, a time-of-flight (Tof) sensor, etc., and the importance of enhancing light sensitivity in such image sensors in the near-infrared range is emerging. However, there is a problem in that light sensitivity in the near-infrared range of existing image sensors is not sufficient for certain applications. Accordingly, the present inventors have conceived a new backside-illuminated image sensor having an improved structure capable of enhancing light sensitivity in the near-infrared range. The detailed description of the new backside-illuminated image sensor is described below. DOCUMENT OF RELATED ART Korean Patent No. 10-0660549, entitled “Image sensor and method of manufacturing the same.” SUMMARY OF THE INVENTION Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and the present disclosure is intended to provide a backside-illuminated image sensor and a method of manufacturing the same, the backside-illuminated image sensor being configured to enhance light sensitivity in the near-infrared range by including a scattering layer in a substrate and in or at each unit pixel that may result in incident light having a path length greater than a thickness of the substrate. Furthermore, the present disclosure is intended to provide a backside-illuminated image sensor and a method of manufacturing the same, wherein first to third structures of unit pixels receiving red light, blue light, and green light extend to different depths to enhance light sensitivity with respect to a specific wavelength or wavelength band of the light passing through a corresponding color filter. In order to achieve the above-described objectives, the present disclosure may be implemented by embodiments having one or more of the following configurations. According to one or more embodiments of the present disclosure, a backside-illuminated image sensor may include a substrate comprising a front surface and a rear surface; a light receiving element at the front surface of the substrate; a deep trench isolation (DTI) region in the substrate and at a boundary of a unit pixel; a scattering layer in the substrate and in the unit pixel; a color filter on the rear surface of the substrate; and a lens on the color filter, wherein the scattering layer may be configured to have a different thickness in different unit pixels. Thus, the substrate may further comprise a plurality of unit pixels, including a first unit pixel, a second unit pixel, and a third unit pixel; the color filter may comprise a plurality of color filters, including a first color filter on or over the first unit pixel, a second color filter on or over the second unit pixel, and a third color