# US 7,608,192 B2 · Image sensor and method for fabricating the same

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- Number: US 7,608,192 B2
- Document ID: US7608192B2
- Status: Granted
- Kind: B2
- Application number: 11/408,206
- Filed: 2006-04-19
- Published: 2007-02-01
- Granted: 2009-10-27
- Earliest claimed: 2005-07-11
- Inventors: Hee Jeen Kim; Han Seob Cha
- Web page: https://patentgrep.com/patent/US7608192B2

## CPC

- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 39/014: {of CMOS image sensors}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An image sensor and a method for fabricating the same are provided. The image sensor includes a first conductive type substrate including a trench formed in a predetermined portion of the first conductive type substrate, a second conductive type impurity region for use in a photodiode, formed below a bottom surface of the trench in the first conductive type substrate, and a first conductive type epitaxial layer for use in the photodiode, buried in the trench.

## Claims

### Claim 1

A method for fabricating an image sensor comprising:
preparing a first conductive substrate;
forming first trenches in the first conductive substrate to define an active region and device isolation regions;
forming a gate electrode over the active region of the first conductive substrate;
forming a second conductive impurity region in the active region of the first conductive substrate;
forming a floating diffusion region on one side of the gate electrode in the active region of the first conductive substrate;
etching a predetermined portion of the second conductive impurity region and a predetermined portion of the active region of the first conductive substrate to form a second trench between the gate electrode and the first trench, wherein the first trenches are deeper than the second trench; and
burying a first conductive epitaxial layer in the second trench by in-situ doping first conductive impurities while growing the first conductive epitaxial layer, wherein the first conductive epitaxial layer includes one of Si and SiGe.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first conductive type impurities are doped in-situ using a diborane (B2H6) source gas at a doping concentration level ranging from approximately 1×1018 cm−3 to approximately 5×1021 cm−3.

### Claim 3 (depends on 1)

The method of claim 1, wherein the second conductive impurity region is self-aligned with an edge of the other side of the gate electrode where the photodiode is to be formed.

### Claim 4 (depends on 1)

The method of claim 1, wherein the SiGe includes a Si source selected from the group consisting of di-chloro-silane (DCS), silane (SiH4), and disilane (Si2H6) and a Ge source of germane (GeH4).

### Claim 5 (depends on 1)

The method of claim 1, wherein the Si is formed at a temperature ranging from approximately 550° C. to approximately 900° C. using a selective epitaxial growing (SEG) method.

### Claim 6 (depends on 1)

The method of claim 1, wherein the SiGe is formed at a temperature ranging from approximately 500° C. to approximately 900° C. using a SEG method.

### Claim 7 (depends on 1)

The method of claim 1, wherein the forming of the second trench includes forming the second trench in a depth ranging from approximately 1 Å to approximately 100 Å.

### Claim 8

A method for fabricating an image sensor comprising:
preparing a first conductive substrate;
forming first trenches in the first conductive substrate to define an active region and device isolation regions;
forming a gate electrode over the active region of the first conductive substrate;
forming a second conductive impurity region in the active region of the first conductive substrate;
forming spacers on sidewalls of the gate electrode;
forming a floating diffusion region on one side of the gate electrode in the active region of the first conductive substrate;
forming a mask pattern by employing a chemical vapor deposition (CVD) method to expose a predetermined portion of the second conductive impurity region and a predetermined portion of the active region of the first conductive substrate; and
forming a first conductive epitaxial layer over the exposed portion of the second conductive impurity region and the first conductive substrate by in-situ doping first conductive impurities while growing the first conductive epitaxial layer, wherein the first conductive epitaxial layer includes one of Si and SiGe.

### Claim 9 (depends on 8)

The method of claim 8, wherein the second conductive impurity region is self-aligned with an edge of the other side of the gate electrode where the photodiode is to be formed.

### Claim 10 (depends on 8)

The method of claim 8, wherein the first conductive impurities are doped in-situ using a B2H6 source gas at a doping concentration level ranging from approximately 1×1018 cm−3 to approximately 5×1021 cm−3.

### Claim 11 (depends on 8)

The method of claim 8, wherein the first conductive epitaxial layer is formed in a thickness ranging from approximately 50 Å to approximately 500 Å.

### Claim 12 (depends on 8)

The method of claim 8, wherein the SiGe includes a Si source selected from the group consisting of DCS, SiH4, and Si2H6 and a Ge source of GeH4.

### Claim 13 (depends on 8)

The method of claim 8, wherein the first conductive epitaxial layer including Si is formed at a temperature ranging from approximately 550° C. to approximately 900° C. using a SEG method, and the first conductive epitaxial layer including SiGe is formed at a temperature ranging from approximately 500° C. to approximately 900° C. using a SEG method.

### Claim 14 (depends on 8)

The method of claim 8, wherein the forming of the mask pattern includes comprising an oxide layer.

### Claim 15 (depends on 8)

The method of claim 8, wherein the forming of the mask pattern includes forming the mask pattern by performing an etching process using hydrogen chloride (HCl) under a specific recipe of a pressure ranging from approximately 0.1 Torr to approximately 760 Torr.