# US 8,541,825 B2 · Image sensor with improved charge transfer efficiency and method for fabricating the same

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- Number: US 8,541,825 B2
- Document ID: US8541825B2
- Status: Granted
- Kind: B2
- Application number: 12/011,433
- Filed: 2008-01-25
- Published: 2008-08-21
- Granted: 2013-09-24
- Earliest claimed: 2004-07-29
- Assignees: Intellectual Ventures II LLC
- Applicants: Jae-Young Park; Youn-Sub Lim
- Inventors: Jae-Young Park; Youn-Sub Lim
- Web page: https://patentgrep.com/patent/US8541825B2

## CPC

- H10F 39/026: {Wafer-level processing}
- H10F 39/014: {of CMOS image sensors}
- H10F 39/1825: {Multicolour image sensors having stacked structure, e.g. NPN, NPNPN or multiple quantum well [MQW] structures}
- H10F 39/807: {Pixel isolation structures}
- H10F 77/146: {Superlattices; Multiple quantum well structures}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An image sensor includes: a first impurity region of the first conductive type aligned with one side of the gate structure and extending to a first depth from a surface portion of the semiconductor layer; a first spacer formed on each sidewall of the gate structure; a second impurity region of the first conductive type, aligned with the first spacer and extending to a second depth that is larger than the first depth from the surface portion of the semiconductor layer; a second spacer formed on each sidewall of the first spacer; a third impurity region of the first conductive type aligned with the second spacer and extending to a third depth that is larger than the second depth from the surface portion of the semiconductor layer; and a fourth impurity region of a second conductive type beneath the third impurity region.

## Claims

### Claim 1

An image sensor, comprising:
a gate structure formed on a semiconductor layer of a first conductive type;
a first impurity region of the first conductive type aligned with one side of the gate structure and extending from a surface portion of the semiconductor layer to a first depth;
a second impurity region of the first conductive type, extending from the surface portion of the semiconductor layer to a second depth that is deeper than the first depth;
a third impurity region of the first conductive type extending from the surface portion of the semiconductor layer to a third depth that is deeper than the second depth;
a fourth impurity region of a second conductive type beneath the third impurity region; and
a floating diffusion region of the second conductive type aligned with the other side of the gate structure and extending to a predetermined depth from another surface portion of the semiconductor layer;
wherein the second conductive type is different than the first conductive type;
wherein the first impurity region, the second impurity region, the third impurity region, and the fourth impurity region form a photodiode of the image sensor; and
wherein the gate is configured to transfer charge collected by the photodiode to the floating diffusion region in response to a control signal.

### Claim 2 (depends on 1)

The image sensor of claim 1, further comprising a first spacer formed on each sidewall of the gate structure.

### Claim 3 (depends on 2)

The image sensor of claim 2, further comprising a screening insulation later formed over the first spacer and the semiconductor layer.

### Claim 4 (depends on 3)

The image sensor of claim 3, wherein the screening insulation layer is formed over an entire surface of the semiconductor layer.

### Claim 5 (depends on 2)

The image sensor of claim 2, further comprising a second spacer formed on each sidewall of the first spacer.

### Claim 6 (depends on 1)

The image sensor of claim 1, wherein the first, second and third impurity regions are each p-type impurity regions, and wherein the fourth impurity region is an n-type impurity region.

### Claim 7 (depends on 1)

The image sensor of claim 1, wherein the entirety of the fourth impurity region is deeper than the third impurity region.

### Claim 8

An image sensor, comprising:
a gate structure formed on a semiconductor layer, wherein the semiconductor layer includes a substrate and an epitaxial layer of a first conductive type formed on the substrate;
a first impurity region of the first conductive type aligned with one side of the gate structure and extending from a surface portion of the epitaxial layer to a first depth in the epitaxial layer;
a first spacer formed on each sidewall of the gate structure;
a second impurity region of the first conductive type, aligned with the first spacer and extending from the surface portion of the epitaxial layer to a second depth in the epitaxial layer that is deeper than the first depth;
a second spacer formed on each sidewall of the first spacer;
a third impurity region of the first conductive type aligned with the second spacer and extending from the surface portion of the epitaxial layer to a third depth in the epitaxial layer that is deeper than the second depth; and
a fourth impurity region of a second conductive type in the epitaxial layer and beneath the third impurity region;
wherein:
the entirety of the fourth impurity region is deeper in the epitaxial layer than the third impurity region;
the second conductive type is different than the first conductive type; and
the first impurity region, the second impurity region, the third impurity region, and the fourth impurity region form a photodiode of the image sensor.

### Claim 9 (depends on 8)

The image sensor of claim 8, wherein the second spacer has a thickness ranging from approximately 500 Å to approximately 1,000 Å.

### Claim 10 (depends on 8)

The image sensor of claim 8, wherein the first spacer and the second spacer comprise an oxide-based material or a nitride-based material.

### Claim 11 (depends on 8)

The image sensor of claim 8, further comprising a floating diffusion region of the second conductive type aligned with the other side of the gate structure and extending to a predetermined depth from another surface portion of the epitaxial layer.

### Claim 12 (depends on 8)

The image sensor of claim 8, wherein the substrate comprises a highly-doped first conductive type substrate.

### Claim 13 (depends on 8)

The image sensor of claim 8, wherein the first, second and third impurity regions are each p-type impurity regions, and wherein the fourth impurity region is an n-type impurity region.

### Claim 14

An image sensor, comprising:
a gate structure formed on a semiconductor layer, wherein the semiconductor layer includes a substrate and an epitaxial layer of a first conductive type formed on the substrate;
a first impurity region of the first conductive type aligned with one side of the gate structure and extending from a surface portion of the epitaxial layer to a first depth in the epitaxial layer;
a first spacer formed on each sidewall of the gate structure;
a second impurity region of the first conductive type, aligned with the first spacer and extending from the surface portion of the epitaxial layer to a second depth in the epitaxial layer that is deeper than the first depth;
a second spacer formed on each sidewall of the first spacer;
a third impurity region of the first conductive type aligned with the second spacer and extending from the surface portion of the epitaxial layer to a third depth in the epitaxial layer that is deeper than the second depth;
a fourth impurity region of a second conductive type in the epitaxial layer and beneath the third impurity region; and
a floating diffusion region of the second conductive type aligned with the other side of the gate structure and extending to a predetermined depth from another surface portion of the epitaxial layer;
wherein:
the entirety of the fourth impurity region is deeper in the epitaxial layer than the third impurity region;
the second conductive type is different than the first conductive type;
the first impurity region, the second impurity region, the third impurity region, and the fourth impurity region form a photodiode of the image sensor; and
the gate is configured to transfer charge collected by the photodiode to the floating diffusion region in response to a control signal.

### Claim 15 (depends on 14)

The image sensor of claim 14, wherein the substrate comprises a highly-doped first conductive type substrate.

### Claim 16 (depends on 14)

The image sensor of claim 14, wherein the first, second and third impurity regions are each p-type impurity regions, and wherein the fourth impurity region is an n-type impurity region.

### Claim 17 (depends on 14)

The image sensor of claim 14, wherein the second spacer has a thickness ranging from approximately 500 Å to approximately 1,000 Å.

### Claim 18 (depends on 14)

The image sensor of claim 14, wherein the first spacer and the second spacer comprise an oxide-based material or a nitride-based material.