# US 2019/0355778 A1 · Vertical overflow drain combined with vertical transistor

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- Number: US 2019/0355778 A1
- Document ID: US20190355778A1
- Status: Published application
- Kind: A1
- Application number: 15/984,136
- Filed: 2018-05-18
- Published: 2019-11-21
- Earliest claimed: 2018-05-18
- Assignees: OmniVision Technologies, Inc.
- Applicants: OmniVision Technologies, Inc.
- Inventors: Yuanwei Zheng; Gang Chen; Duli Mao; Dyson Tai; Lindsay Grant
- Web page: https://patentgrep.com/patent/US20190355778A1

## CPC

- H10F 39/1865: {Overflow drain structures}
- H04N 25/621: for the control of blooming
- 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 39/8033: {Photosensitive area}
- H10F 39/80373: {characterised by the gate of the transistor}
- H10F 39/807: {Pixel isolation structures}
- H10F 39/813: {Electronic components shared by multiple pixels, e.g. one amplifier shared by two pixels}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An image sensor pixel includes a photodiode disposed in a semiconductor material to generate image charge in response to light incident on a backside of the semiconductor material, and a pinning layer disposed in the semiconducting material and coupled to the photodiode. The pixel also includes a vertical overflow drain disposed in the semiconductor material and coupled to the pinning layer such that the pinning layer is disposed between the vertical overflow drain and the photodiode. A floating diffusion disposed in the semiconductor material proximate to the photodiode, and a vertical transfer transistor is disposed in part in the semiconductor material and coupled to the photodiode to transfer the image charge from the photodiode to the floating diffusion in response to a transfer signal applied to the gate terminal of the vertical transfer transistor.

## Claims

### Claim 1

An image sensor pixel, comprising:
a photodiode disposed in a semiconductor material to generate image charge in response to light incident on a backside of the semiconductor material;
a pinning layer disposed in the semiconducting material and coupled to the photodiode;
a vertical overflow drain disposed in the semiconductor material, the vertical overflow drain in contact with the pinning layer and coupled to the pinning layer such that the pinning layer is disposed between the vertical overflow drain and the photodiode;
a floating diffusion disposed in the semiconductor material proximate to the photodiode; and
a vertical transfer transistor disposed in part in the semiconductor material and coupled to the photodiode to transfer the image charge from the photodiode to the floating diffusion in response to a transfer signal applied to a gate terminal of the vertical transfer transistor.

### Claim 2 (depends on 1)

The image sensor pixel of claim 1, further comprising a gate oxide disposed on a frontside, opposite the backside, of the semiconductor material, and extending into the semiconductor material so that the gate oxide is disposed between the semiconductor material and a portion of the vertical transfer transistor that extends into the semiconductor material.

### Claim 3 (depends on 2)

The image sensor pixel of claim 2, wherein the vertical transfer transistor extends into the frontside of the semiconductor material.

### Claim 4 (depends on 3)

The image sensor pixel of claim 3, further comprising a shallow trench isolation structure extending into the frontside of the semiconductor material and surrounding the photodiode at least in part.

### Claim 5 (depends on 4)

The image sensor pixel of claim 4, wherein the shallow trench isolation structure includes a trench in the semiconductor material at least partially filled with an oxide.

### Claim 6 (depends on 4)

The image sensor pixel of claim 4, further comprising a deep isolation well extending from the shallow trench isolation structure to the backside of the semiconductor material.

### Claim 7 (depends on 6)

The image sensor pixel of claim 6, wherein the deep isolation well includes a doped region of the semiconductor material.

### Claim 8 (depends on 1)

The image sensor pixel of claim 1, wherein the gate terminal of the vertical transfer transistor is substantially “T”-shaped.

### Claim 9 (depends on 1)

The image sensor pixel of claim 1, wherein the photodiode includes a first majority charge carrier type, the pinning layer includes a second majority charge carrier type, and the vertical overflow drain includes the first majority charge carrier type.

### Claim 10 (depends on 9)

The image sensor pixel of claim 9, wherein the first majority charge carrier type is n-type, and wherein the second majority charge carrier type is p-type, and wherein the photodiode is disposed between the backside and the vertical overflow drain.

### Claim 11

An image sensor system, comprising:
a plurality of pixels disposed in a semiconductor material positioned to receive light through a backside of the image sensor and generate image charge, wherein each pixel in the plurality of pixels includes:
a photodiode disposed in a semiconductor material;
a pinning layer disposed in the semiconducting material and coupled to the photodiode;
a vertical overflow drain disposed in the semiconductor material, the vertical overflow drain in contact with the pinning layer and coupled to the pinning layer such that the pinning layer is disposed between the vertical overflow drain and the photodiode;
a floating diffusion disposed in the semiconductor material proximate to the photodiode; and
a vertical transfer transistor disposed in part in the semiconductor material and coupled to the photodiode to transfer the image charge from the photodiode to the floating diffusion in response to a transfer signal applied to a gate terminal of the vertical transfer transistor; and
readout circuitry coupled to the plurality of pixels to readout the image charge from the plurality of pixels; and
control circuitry coupled to the plurality of pixels to control operation of the plurality of pixels.

### Claim 12 (depends on 11)

The image sensor system of claim 11, further comprising:
a reset transistor coupled to the floating diffusion to reset the image charge in the floating diffusion; and
a source follower transistor coupled to the floating diffusion to amplify the image charge on the floating diffusion for readout with the readout circuitry.

### Claim 13 (depends on 12)

The image sensor system of claim 12, further comprising function logic coupled to receive image data readout from the readout circuitry, and wherein the function logic is coupled to alter the image data.

### Claim 14 (depends on 11)

The image sensor system of claim 11, further comprising a gate oxide disposed on a frontside, opposite the backside, of the semiconductor material, and extending into the semiconductor material so that the gate oxide is disposed between the semiconductor material and a portion of the vertical transfer transistor that extends into the semiconductor material.

### Claim 15 (depends on 14)

The image sensor system of claim 14, wherein the vertical transfer transistor extends into the frontside of the semiconductor material.

### Claim 16 (depends on 15)

The image sensor system of claim 15, further comprising a shallow trench isolation structure extending into the frontside of the semiconductor material and surrounding the photodiode at least in part.

### Claim 17 (depends on 16)

The image sensor system of claim 16, wherein the shallow trench isolation structure includes a trench in the semiconductor material filled with an oxide.

### Claim 18 (depends on 16)

The image sensor system of claim 16, further comprising a deep isolation well extending from the shallow trench isolation structure to the backside of the semiconductor material.

### Claim 19 (depends on 18)

The image sensor system of claim 18, wherein the deep isolation well includes a doped region of the semiconductor material.

### Claim 20 (depends on 11)

The image sensor system of claim 11, wherein the gate terminal of the vertical transfer transistor is substantially “T”-shaped.