# US 12,218,166 B2 · CSI with controllable isolation structure and methods of manufacturing and using the same

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- Number: US 12,218,166 B2
- Document ID: US12218166B2
- Status: Granted
- Kind: B2
- Application number: 17/372,888
- Filed: 2021-07-12
- Published: 2022-10-20
- Granted: 2025-02-04
- Earliest claimed: 2021-04-19
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Min-Feng Kao; Dun-Nian Yaung; Jen-Cheng Liu; Wen-Chang Kuo; Shih-Han Huang
- Web page: https://patentgrep.com/patent/US12218166B2

## CPC

- H10F 39/807: {Pixel isolation structures}
- H10F 39/024: {of coatings or optical elements}
- H10F 39/199: {Back-illuminated image sensors}
- H10F 39/8053: {Colour filters}
- H10F 39/8057: {Optical shielding}
- H10F 39/8063: {Microlenses}
- H10F 39/811: {Interconnections}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

A metal grid within a trench isolation structure on the back side of an image sensor is coupled to a contact pad so that a voltage on the metal grid is continuously variable with a voltage on the contact pad. One or more conductive structures directly couple the metal grid to a contact pad. The conductive structures may bypass a front side of the image sensor. A bias voltage on the metal grid may be varied through the contact pad whereby a trade-off between reducing cross-talk and increasing quantum efficiency may be adjusted dynamically in accordance with the application of the image sensor, its environment of use, or its mode of operation.

## Claims

### Claim 1

A method, comprising:
providing a semiconductor substrate including a front side, a back side, a pixel region, a peripheral region, and photodetector pixels in an array within the pixel region;
forming a back side isolation structure including a metal grid with segments extending into the semiconductor substrate between the photodetector pixels;
forming a dielectric layer, wherein the dielectric layer is over the metal grid;
forming an opening in the dielectric layer, wherein the metal grid is exposed through the opening; and
depositing a metal layer, wherein depositing the metal layer fills the opening and simultaneously creates a contact pad on the back side, a via intersecting the metal grid, and a conductive bridge extending from the via to the contact pad on the back side;
wherein the metal grid is electrically isolated from the semiconductor substrate and electrically coupled to the contact pad.

### Claim 2 (depends on 1)

The method of claim 1, wherein depositing the metal layer creates a back side metal grid over the metal grid.

### Claim 3 (depends on 2)

The method of claim 2, wherein the back side metal grid has an elevation over the back side greater than or equal to the contact pad.

### Claim 4 (depends on 2)

The method of claim 2, further comprising, forming a second opening, wherein the second opening extend through the dielectric layer, the semiconductor substrate is exposed through the second opening, depositing the metal layer fills the second opening to create a ground bar, and the back side metal grid is electrically connected to the semiconductor substrate through the ground bar.

### Claim 5 (depends on 4)

The method of claim 4, wherein the second opening extends into the semiconductor substrate.

### Claim 6 (depends on 1)

The method of claim 1, wherein forming the back side isolation structure comprises etching trenches in the semiconductor substrate from the back side and filling the trenches.

### Claim 7 (depends on 1)

The method of claim 1, wherein the metal grid comprises aluminum or tungsten.

### Claim 8 (depends on 1)

The method of claim 1, wherein the metal layer comprises aluminum, tungsten or copper.

### Claim 9 (depends on 1)

The method of claim 1, wherein the contact pad is formed opposite an unused contact pad proximate the front side.

### Claim 10

A method of manufacturing an image sensing integrated circuit device, the method comprising:
providing a semiconductor substrate including a first side, a second side, a pixel region, and a peripheral region;
forming photodiodes in an array in the pixel region;
thinning the semiconductor substrate from the second side;
forming a grid of trenches in the second side, wherein the grid comprises segments that extend between adjacent photodiodes in the array;
filling the trenches, wherein filling the trenches comprises depositing a conductive material in the trenches so that the conductive material forms an in-substrate metal grid;
forming a dielectric layer over the in-substrate metal grid; and
forming an opening in the dielectric layer, wherein the in-substrate metal grid is exposed through the opening; and
depositing a metal layer, wherein depositing the metal layer fills the opening and simultaneously creates a via intersecting the in-substrate metal grid, a contact pad on the second side, a conductive bridge extending from the via to the contact pad on the second side, and a back side metal grid over the dielectric layer in the pixel region, wherein the back side metal grid is formed above the in-substrate metal grid.

### Claim 11 (depends on 10)

The method of claim 10, wherein:
the in-substrate metal grid extends over the second side; and
the conductive bridge is above the in-substrate metal grid on the second side.

### Claim 12 (depends on 10)

The method of claim 10, wherein the in-substrate metal grid extends into the peripheral region.

### Claim 13 (depends on 12)

The method of claim 12, via is in the peripheral region.

### Claim 14 (depends on 12)

The method of claim 12, further comprising:
depositing a second dielectric layer over the metal layer; and
patterning the second dielectric layer together with the metal layer, wherein patterning defines the back side metal grid from the metal layer.

### Claim 15 (depends on 10)

The method of claim 10, wherein the conductive bridge and the contact pad are a continuous structure having a homogeneous composition.

### Claim 16 (depends on 10)

The method of claim 10, wherein in-substrate metal grid is electrically isolated from the semiconductor substrate.

### Claim 17 (depends on 10)

The method of claim 10, wherein the contact pad is formed opposite an unused contact pad proximate the first side.

### Claim 18

A method of manufacturing an image sensing integrated circuit device, the method comprising:
providing a semiconductor substrate including a first side, a second side, a pixel region, and a peripheral region;
forming photodetector pixels in an array in the pixel region;
thinning the semiconductor substrate from the second side;
forming an isolation structure that extends between adjacent pairs of the photodetector pixels and comprises an in-substrate metal grid; and
forming a dielectric layer over the isolation structure;
forming a first opening in the dielectric layer, wherein the in-substrate metal grid is exposed through the opening; and
depositing a metal layer, wherein depositing the metal layer fills the first opening and simultaneously creates, a contact pad in the peripheral region on the second side, a via intersecting the in-substrate metal grid, and a conductive bridge extending from the via to the contact pad,
wherein the in-substrate metal grid is coupled to the contact pad so that a voltage on the in-substrate metal grid is continuously variable with a voltage on the contact pad; and
the in-substrate metal grid is electrically isolated from a ground voltage of the semiconductor substrate.

### Claim 19 (depends on 18)

The method of claim 18, wherein the coupling between the in-substrate metal grid and the contact pad bypasses the first side.

### Claim 20 (depends on 18)

The method of claim 18, further comprising:
forming a second opening extending through the dielectric layer, wherein the semiconductor substrate is exposed in the second hole opening; and
depositing the metal layer fills the second opening and creates ground bars in the second opening.