# US 10,373,999 B2 · Image sensor and associated fabricating method

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- Number: US 10,373,999 B2
- Document ID: US10373999B2
- Status: Granted
- Kind: B2
- Application number: 15/903,548
- Filed: 2018-02-23
- Published: 2019-04-04
- Granted: 2019-08-06
- Earliest claimed: 2017-09-29
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Company Ltd.
- Inventors: Yuichiro Yamashita
- Web page: https://patentgrep.com/patent/US10373999B2

## CPC

- H10F 39/811: {Interconnections}
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 39/1825: {Multicolour image sensors having stacked structure, e.g. NPN, NPNPN or multiple quantum well [MQW] structures}
- H10F 39/8067: {Reflectors}
- H10F 39/807: {Pixel isolation structures}
- H10F 39/809: {of hybrid image sensors}
- H10F 39/199: {Back-illuminated image sensors}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An image sensor is disclosed. The image sensor includes: a common node heavily doped with dopants of a first conductivity type, the common node being within the substrate and abutting the front surface of the substrate; and a sensing node heavily doped with dopants of a second conductivity type opposite to the first conductivity type, the sensing node being within the substrate and abutting the front surface of the substrate; an interconnect structure, wherein the front surface of the substrate faces the interconnect structure; a distributed Bragg reflector (DBR) between the front surface of the substrate and the interconnect structure; a first contact plug passing through the DBR and coupling the common node to the interconnect structure; and a second contact plug passing through the DBR and coupling the sensing node to the interconnect structure.

## Claims

### Claim 1

An image sensor, comprising:
a substrate having a front surface and a back surface, wherein the substrate includes:
a common node heavily doped with dopants of a first conductivity type, the common node being within the substrate and abutting the front surface of the substrate; and
a sensing node heavily doped with dopants of a second conductivity type opposite to the first conductivity type, the sensing node being within the substrate and abutting the front surface of the substrate;
an interconnect structure, wherein the front surface of the substrate faces the interconnect structure;
a distributed Bragg reflector (DBR) between the front surface of the substrate and the interconnect structure;
a first contact plug passing through the DBR and coupling the common node to the interconnect structure; and
a second contact plug passing through the DBR and coupling the sensing node to the interconnect structure.

### Claim 2 (depends on 1)

The image sensor of claim 1, wherein the DBR includes alternating insulating layers.

### Claim 3 (depends on 2)

The image sensor of claim 2, wherein the DBR includes at least one pair of layers including a first layer and a second layer selected from two of silicon dioxide (SiO2), undoped polysilicon (poly) and silicon nitride (Si3N4).

### Claim 4 (depends on 3)

The image sensor of claim 3, wherein the first layer includes SiO2, the second layer includes undoped poly, and the first layer is facing the front surface of the substrate.

### Claim 5 (depends on 1)

The image sensor of claim 1, wherein the DBR is distanced from the first contact plug and the second contact plug by a distance greater than 0.

### Claim 6 (depends on 1)

The image sensor of claim 1, wherein the DBR is distanced from the second contact plug by a distance greater than 0, and the DBR is in physical contact with the first contact plug.

### Claim 7 (depends on 1)

The image sensor of claim 1, further comprising a contact etch-stop layer (CESL) between the DBR and the front surface of the substrate.

### Claim 8 (depends on 1)

The image sensor of claim 1, further comprising a contact etch-stop layer (CESL) between the DBR and the interconnect structure.

### Claim 9 (depends on 7)

The image sensor of claim 7, further comprising a lens at the back surface of the substrate.

### Claim 10

An image sensor, comprising:
a substrate having a front surface and a back surface, wherein the substrate includes:
a common node heavily doped with dopants of a first conductivity type, the common node being within the substrate and abutting the front surface of the substrate; and
a sensing node heavily doped with dopants of a second conductivity type opposite to the first conductivity type, the sensing node being within the substrate and abutting the front surface of the substrate;
a lens at the back surface of the substrate;
a distributed Bragg reflector (DBR) at the front surface of the substrate.

### Claim 11 (depends on 10)

The image sensor of claim 10, wherein the DBR includes alternating insulating layers.

### Claim 12 (depends on 11)

The image sensor of claim 11, wherein the DBR includes at least one pair of layers including a first layer and a second layer selected from two of silicon dioxide (SiO2), undoped polysilicon (poly) and silicon nitride (Si3N4).

### Claim 13 (depends on 12)

The image sensor of claim 12, wherein the first layer includes SiO2, the second layer includes undoped poly, and the first layer is facing the front surface of the substrate.

### Claim 14 (depends on 10)

The image sensor of claim 10, further comprising a contact etch-stop layer (CESL) between the DBR and the front surface of the substrate.

### Claim 15

An image sensor, comprising:
a substrate having a front side and a back side, wherein the substrate includes a first pixel and a second pixel each having:
a first common node and a second common node heavily doped with dopants of a first conductivity type, the first and second common nodes being within the substrate and abutting the front side of the substrate; and
a sensing node heavily doped with dopants of a second conductivity type opposite to the first conductivity type, the sensing node being within the substrate and abutting the front side of the substrate, and the sensing node being between the first and second common nodes;
an interconnect structure, wherein the front side of the substrate faces the interconnect structure;
a distributed Bragg reflector (DBR) between the front side of the substrate and the interconnect structure, at least a portion of the DBR extending into the substrate between the first and second pixels.

### Claim 16 (depends on 15)

The image sensor of of claim 15, wherein at least a portion of the DBR extending into the substrate between the first and second pixels.

### Claim 17 (depends on 15)

The image sensor of of claim 15, wherein the DBR includes alternating insulating layers.

### Claim 18 (depends on 17)

The image sensor of of claim 17, wherein the DBR includes at least two pairs of layers, and each pair of layers includes a first layer and a second layer selected from two of silicon dioxide (SiO2), undoped polysilicon (poly) and silicon nitride (Si3N4).

### Claim 19 (depends on 18)

The image sensor of claim 18, wherein the first layer includes SiO2, the second layer includes undoped poly, and the first layer is facing the front side of the substrate.

### Claim 20 (depends on 18)

The image sensor of of claim 18, wherein the DBR includes a first pair and a second pair of SiO2/undoped poly, and the first pair and the SiO2 of the second pair extend into the substrate between the first and second pixels, and the undoped poly of the second pair is free from extending into the substrate.