# US 10,483,310 B2 · Isolation structure for reducing crosstalk between pixels and fabrication method thereof

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- Number: US 10,483,310 B2
- Document ID: US10483310B2
- Status: Granted
- Kind: B2
- Application number: 15/448,690
- Filed: 2017-03-03
- Published: 2018-09-06
- Granted: 2019-11-19
- Earliest claimed: 2017-03-03
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Yun-Wei Cheng; Yin-Chieh Huang; Chun-Hao Chou; Kuo-Cheng Lee; Hsun-Ying Huang
- Web page: https://patentgrep.com/patent/US10483310B2

## CPC

- H10F 39/807: {Pixel isolation structures}
- H10F 39/024: {of coatings or optical elements}
- H10F 39/199: {Back-illuminated image sensors}
- H10F 39/8067: {Reflectors}
- H10F 39/8053: {Colour filters}
- H10F 39/8063: {Microlenses}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An isolation structure and a method for fabricating the same are provided. The isolation structure includes a reflective layer, a first dielectric layer and a second dielectric layer. A dielectric constant of the first dielectric layer is different from that of the second dielectric layer. In the method for fabricating the isolation structure, at first, a semiconductor substrate is provided. Then, a first reflective layer is formed on the semiconductor substrate. Thereafter, the first dielectric layer is formed on the reflective layer. Thereafter, the second dielectric layer is on the first dielectric layer. Then, the first reflective layer, the first dielectric layer and the second dielectric layer are etched to form a grid structure. Thereafter, a passivation layer is formed to cover the etched first reflective layer, the etched first dielectric layer and the etched second dielectric layer.

## Claims

### Claim 1

An isolation structure, comprising:
a reflective layer;
a first dielectric layer disposed on the reflective layer;
a second dielectric layer disposed on the first dielectric layer; and
a third dielectric layer disposed on the second dielectric layer, wherein the second dielectric layer is located between the first dielectric layer and the third dielectric layer and a dielectric constant of the first dielectric layer is different from that of the second dielectric layer.

### Claim 2 (depends on 1)

The isolation structure of claim 1, wherein the dielectric constant of the first dielectric layer is greater than that of the second dielectric layer, and the dielectric constant of the second dielectric layer is greater than that of the third dielectric layer.

### Claim 3 (depends on 1)

The isolation structure of claim 1, wherein the dielectric constant of the first dielectric layer is smaller than that of the second dielectric layer, and the dielectric constant of the second dielectric layer is smaller than that of the third dielectric layer.

### Claim 4 (depends on 1)

The isolation structure of claim 1, wherein the reflective layer is formed from metal.

### Claim 5 (depends on 1)

The isolation structure of claim 1, wherein the isolation structure has a bottom surface comprising a portion of the reflective layer, the bottom surface has a surface width, the isolation structure has a structure height, and a ratio of the structure height to the surface width is equal to or greater than 4.

### Claim 6 (depends on 1)

The isolation structure of claim 1, wherein the first dielectric layer and the second dielectric layer are formed from silicon oxide, silicon nitride, silicon oxynitride or silicon carbide.

### Claim 7

An image sensor, comprising:
a semiconductor substrate;
a grid isolation structure disposed on the semiconductor substrate to define a plurality of pixel regions, wherein the grid isolation structure comprises:
a reflective layer;
a first dielectric layer disposed on the reflective layer; and
a second dielectric layer disposed on the first dielectric layer, wherein a dielectric constant of the first dielectric layer is different from that of the second dielectric layer; and
a plurality of light-sensitive elements disposed corresponding to the pixel regions.

### Claim 8 (depends on 7)

The image sensor of claim 7, wherein the grid isolation structure has a bottom surface comprising a portion of the reflective layer, the bottom surface has a surface width, each of the pixel regions has a pixel width, and a ratio of the surface width to the pixel width is substantially equal to or smaller than 0.2.

### Claim 9 (depends on 7)

The image sensor of claim 7, wherein the light-sensitive elements are photodiodes.

### Claim 10 (depends on 7)

The image sensor of claim 7, further comprising a micro lens layer disposed on the pixel regions and covering the grid isolation structure.

### Claim 11

An isolation structure, comprising:
a grid isolation structure disposed on the semiconductor substrate to define a plurality of pixel regions, wherein the grid isolation structure comprises:
a reflective layer;
a first dielectric layer disposed on the reflective layer; and
a second dielectric layer disposed on the first dielectric layer, wherein a dielectric constant of the first dielectric layer is different from that of the second dielectric layer; and
a trench isolation structure disposed in the semiconductor substrate and under the grid isolation structure, wherein trench isolation structure comprises:
a trench in the semiconductor substrate;
a trench dielectric layer covering the semiconductor substrate, wherein the trench dielectric layer has a trench portion located in the trench of the semiconductor substrate; and
a trench reflective layer disposed on the trench portion of the trench dielectric layer.

### Claim 12 (depends on 11)

The isolation structure of claim 11, further comprising a third dielectric layer disposed on the second dielectric layer, wherein the second dielectric layer is located between the first dielectric layer and the third dielectric layer.

### Claim 13 (depends on 12)

The isolation structure of claim 12, wherein the dielectric constant of the first dielectric layer is greater than that of the second dielectric layer, and the dielectric constant of the second dielectric layer is greater than that of the third dielectric layer.

### Claim 14 (depends on 12)

The isolation structure of claim 12, wherein the dielectric constant of the first dielectric layer is smaller than that of the second dielectric layer, and the dielectric constant of the second dielectric layer is smaller than that of the third dielectric layer.

### Claim 15 (depends on 11)

The isolation structure of claim 11, wherein the reflective layer is formed from metal.

### Claim 16 (depends on 11)

The isolation structure of claim 11, wherein the isolation structure has a bottom surface comprising a portion of the reflective layer, the bottom surface has a surface width, the isolation structure has a structure height, and a ratio of the structure height to the surface width is equal to or greater than 4.

### Claim 17 (depends on 11)

The isolation structure of claim 11, wherein the first dielectric layer and the second dielectric layer are formed from silicon oxide, silicon nitride, silicon oxynitride or silicon carbide.

### Claim 18 (depends on 11)

The isolation structure of claim 11, wherein the trench dielectric layer is formed from high-k dielectric material.

### Claim 19 (depends on 11)

The isolation structure of claim 11, wherein the trench reflective layer covers the trench dielectric layer.

### Claim 20 (depends on 1)

The isolation structure of claim 1, further comprising a passivation layer covering the third dielectric layer.