# US 12,191,327 B2 · CMOS image sensor having indented photodiode structure

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- Number: US 12,191,327 B2
- Document ID: US12191327B2
- Status: Granted
- Kind: B2
- Application number: 18/500,357
- Filed: 2023-11-02
- Published: 2024-02-22
- Granted: 2025-01-07
- Earliest claimed: 2017-09-29
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Company, Ltd.
- Inventors: Chia-Yu Wei; Hsin-Chi Chen; Kuo-Cheng Lee; Ping-Hao Lin; Hsun-Ying Huang; Yen-Liang Lin; Yu Ting Kao
- Web page: https://patentgrep.com/patent/US12191327B2

## CPC

- H10F 39/8027: {Geometry of the photosensitive area}
- H10F 39/014: {of CMOS image sensors}
- H10F 39/12: Image sensors
- H10F 39/8033: {Photosensitive area}
- H10F 39/8037: {the integrated elements comprising a transistor}
- H10F 39/8053: {Colour filters}
- H10F 39/807: {Pixel isolation structures}
- H10F 39/811: {Interconnections}
- H10F 39/813: {Electronic components shared by multiple pixels, e.g. one amplifier shared by two pixels}
- H10D 30/63: Vertical IGFETs (H10D30/66 {, H10D30/6728, H10D30/689, H10D30/693} take precedence)
- H10F 39/026: {Wafer-level processing}
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 39/182: {Colour image sensors}
- H10F 39/1825: {Multicolour image sensors having stacked structure, e.g. NPN, NPNPN or multiple quantum well [MQW] structures}
- H10F 39/199: {Back-illuminated image sensors}
- H10F 39/802: {Geometry or disposition of elements in pixels, e.g. address-lines or gate electrodes}
- H10F 39/8063: {Microlenses}
- H10F 39/812: {Arrangements for transferring the charges in the image sensor perpendicular to the imaging plane, e.g. buried regions used to transfer generated charges to circuitry under the photosensitive region}
- H10W 10/014: {using trench refilling with dielectric materials, e.g. shallow trench isolations}
- H10W 10/17: formed using trench refilling with dielectric materials, e.g. shallow trench isolations
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

The present disclosure relates to a CMOS image sensor, and an associated method of formation. In some embodiments, the CMOS image sensor comprises a substrate and a transfer gate disposed from a front-side surface of the substrate. The CMOS image sensor further comprises a photo detecting column disposed at one side of the transfer gate within the substrate. The photo detecting column comprises a doped sensing layer comprising one or more recessed portions along a circumference of the doped sensing layer in parallel to the front-side surface of the substrate. By forming the photo detecting column with recessed portions, a junction interface is enlarged compared to a previous p-n junction interface without recessed portions, and thus a full well capacity of the photodiode structure is improved.

## Claims

### Claim 1

A method of forming an image sensor, comprising:
forming a transfer gate over a substrate, wherein the substrate is doped with a first doping type;
forming a floating diffusion region within the substrate;
forming a masking layer over the substrate, the masking layer having a circumference including a first recessed portion spaced apart from a second recessed portion from a top-down view, the first recessed portion and the second recessed portion are symmetrically distributed across a line that extends through centers of both the transfer gate and the floating diffusion region; and
with the masking layer in place, performing a plurality of implantation processes to form a photo detecting column within the substrate at one side of the transfer gate opposing to the floating diffusion region;
wherein the photo detecting column and the substrate are in contact with each other at a junction interface and configured as a photodiode structure to convert radiation that enters the substrate into an electrical signal.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
forming a back-end-of-the-line (BEOL) metallization stack on a front-side of the substrate, wherein the BEOL metallization stack comprises a plurality of metal interconnect layers within one or more inter-level dielectric layers.

### Claim 3 (depends on 1)

The method of claim 1, wherein the photo detecting column is formed with one or more recessed portions extending upwardly to a front-side surface of the substrate.

### Claim 4 (depends on 1)

The method of claim 1, wherein the plurality of implantation processes further comprises:
forming a deep doped layer with a second doping type different than the first doping type;
forming a doped sensing layer with the second doping type over the deep doped layer; and
forming a pinning layer with the first doping type over the doped sensing layer.

### Claim 5 (depends on 4)

The method of claim 4, wherein the pinning layer is formed with a first sidewall surface and a second sidewall surface both vertically aligned with that of the doped sensing layer.

### Claim 6 (depends on 4)

The method of claim 4, wherein the deep doped layer has a doping concentration smaller than that of the doped sensing layer.

### Claim 7 (depends on 1)

The method of claim 1, wherein a top surface of the photo detecting column has a concave polygon shape.

### Claim 8

A method for forming an image sensor, the method comprising:
forming a transfer gate over a substrate, wherein the substrate is doped with a first doping type;
forming a floating diffusion region within the substrate on one side of the transfer gate; and
forming a photo detecting column within the substrate on another side of the transfer gate opposite to the floating diffusion region;
wherein the photo detecting column has a circumference with recessed portions extending vertically from top to bottom that are symmetrically distributed along a line that extends through centers of both the transfer gate and the floating diffusion region, and wherein the recessed portions have a height that is equal to a height of the photo detecting column.

### Claim 9 (depends on 8)

The method of claim 8, wherein the forming of the photo detecting column further comprises:
forming a deep doped layer with a second doping type different than the first doping type;
forming a doped sensing layer with the second doping type over the deep doped layer; and
forming a pinning layer with the first doping type over the doped sensing layer.

### Claim 10 (depends on 9)

The method of claim 9, wherein the deep doped layer is formed with a thickness about two times greater than that of the doped sensing layer.

### Claim 11 (depends on 9)

The method of claim 9, wherein the deep doped layer is formed with a first sidewall surface and a second sidewall surface both vertically aligned with that of the doped sensing layer.

### Claim 12 (depends on 8)

The method of claim 8, further comprising:
forming a back-end-of-line (BEOL) metallization stack on a front-side of the substrate and comprising a plurality of metal interconnect layers within one or more inter-level dielectric layers.

### Claim 13 (depends on 8)

The method of claim 8, further comprising:
forming a color filter on a back-side of the substrate opposite to a front-side of the substrate and in a grid structure, wherein the color filter overlies the photo detecting column.

### Claim 14

A method for forming a complementary metal-oxide-semiconductor (CMOS) image sensor, the method comprising:
forming a transfer gate over a substrate;
forming a floating diffusion region within the substrate; and
forming a photo detecting column within the substrate on another side of the transfer gate opposite to the floating diffusion region;
wherein the photo detecting column has a first recessed portion and a second recessed portion, the first recessed portion extends from a first side into the photo detecting column along a first direction, and the second recessed portion extends from a second side into the photo detecting column along a second direction, the first direction being perpendicular to the second direction.

### Claim 15 (depends on 14)

The method of claim 14, wherein the transfer gate has a triangular shape.

### Claim 16 (depends on 14)

The method of claim 14, wherein a top surface of the photo detecting column has a concave polygon shape.

### Claim 17 (depends on 14)

The method of claim 14, wherein the first recessed portion and the second recessed portion are symmetrically mirrored across a plane that extends through both the transfer gate and the floating diffusion region.

### Claim 18 (depends on 14)

The method of claim 14, further comprising:
forming a back-end-of-the-line (BEOL) metallization stack on a front-side of the substrate, wherein the BEOL metallization stack comprises a plurality of metal interconnect layers within one or more inter-level dielectric layers.

### Claim 19 (depends on 14)

The method of claim 14, wherein the forming of the photo detecting column further comprises:
forming a deep doped layer with a second doping type different than a first doping type;
forming a doped sensing layer with the second doping type over the deep doped layer; and
forming a pinning layer with the first doping type over the doped sensing layer.

### Claim 20 (depends on 19)

The method of claim 19, wherein the deep doped layer has a thickness about two times greater than that of the doped sensing layer.