# US 6,720,595 B2 · Three-dimensional island pixel photo-sensor

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- Number: US 6,720,595 B2
- Document ID: US6720595B2
- Status: Granted
- Kind: B2
- Application number: 09/922,077
- Filed: 2001-08-06
- Published: 2003-02-06
- Granted: 2004-04-13
- Earliest claimed: 2001-08-06
- Assignees: International Business Machines Corporation
- Inventors: Lawrence A. Clevenger; Louis L. Hsu; Carl J. Radens; Li-Kong Wang; Kwong Hon Wong
- Web page: https://patentgrep.com/patent/US6720595B2

## CPC

- H10F 39/809: {of hybrid image sensors}
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 39/807: {Pixel isolation structures}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

A method and structure for a photodiode array comprising a plurality of photodiode cores, light sensing sidewalls along an exterior of the cores, logic circuitry above the cores, trenches separating the cores, and a transparent material in the trenches is disclosed. With the invention, the sidewalls are perpendicular to the surface of the photodiode that receives incident light. The light sensing sidewalls comprise a junction region that causes electron transfer when struck with light. The sidewalls comprise four vertical sidewalls around each island core. The logic circuitry blocks light from the core so light is primarily only sensed by the sidewalls.

## Claims

### Claim 1

An island photodiode comprising:
a core having a cube shape;
light sensing sidewalls along an exterior of said core, wherein said sidewalls are perpendicular to a surface of said photodiode that receives incident light; and
logic circuitry above said core.

### Claim 2 (depends on 1)

The island photodiode in claim 1, wherein said light sensing sidewalls comprise a junction region that causes electron transfer when struck with light.

### Claim 3 (depends on 1)

The island photodiode in claim 1, wherein said logic circuitry blocks light from reaching the top of said core.

### Claim 4 (depends on 1)

The island photodiode in claim 1, wherein said sidewalls comprise four vertical sidewalls.

### Claim 5 (depends on 1)

The island photodiode in claim 1, wherein said core comprises a n+ core and said sidewalls comprise p+ sidewalls.

### Claim 6

A photodiode array comprising:
a plurality of photodiode cores, each of said cores having a cube shape;
light sensing sidewalls along an exterior of said cores, wherein said sidewalls are perpendicular to a surface of said photodiode that receives incident light;
logic circuitry above said cores;
trenches separating said cores; and
a transparent material in said trenches.

### Claim 7 (depends on 6)

The photodiode array in claim 6, wherein said light sensing sidewalls comprise a junction region that causes electron transfer when struck with light.

### Claim 8 (depends on 6)

The photodiode array in claim 6, wherein said logic circuitry blocks light from reaching the top of said core.

### Claim 9 (depends on 6)

The photodiode array in claim 6, wherein said sidewalls comprise four vertical sidewalls.

### Claim 10 (depends on 6)

The photodiode array in claim 6, wherein said core comprises a n+ core and said sidewalls comprise p+ sidewalls.

### Claim 11

A p-i-n island photodiode comprising:
a n+ core having a cube shape;
an intrinsic layer surrounding sides of said n+ core;
a p+ layer surrounding sides of said intrinsic layer;
at least one transistor above said n+ core; and
light sensing sidewalls along an exterior of said p+ layer, wherein said sidewalls are perpendicular to a surface of said photodiode that receives incident light.

### Claim 12 (depends on 11)

The p-i-n island photodiode in claim 11, further comprising an n-well between and connecting said n+ core and said transistor.

### Claim 13 (depends on 11)

The p-i-n island photodiode in claim 11, wherein said p+ layer comprises a p-type doped layer having a doping concentration in the range from 1e15 to 1e 18 cm3.

### Claim 14 (depends on 11)

The p-i-n island photodiode in claim 11, wherein n+ core comprises an n-type doped layer having a doping concentration in the range from 10e 1 to 10e17 cm3.

### Claim 15 (depends on 11)

The p-i-n photo diode in claim 11, further comprising an anti-reflective coating surrounding sides of said p+ layer.

### Claim 16 (depends on 15)

The p-i-n photo diode in claim 15, further comprising a transparent material adjacent said anti-reflective coating.

### Claim 17 (depends on 16)

The p-i-n photo diode in claim 16, further comprising wiring levels above said transistor, wherein said wiring levels include transparent regions above said transparent material.

### Claim 18

An island photodiode comprising:
a core;
vertical light sensing sidewalls along am exterior of said core; and
transparent regions adjacent said sidewalls and exterior to said sidewalls.

### Claim 19

A photodiode array comprising:
a plurality of photodiode cores;
vertical light sensing sidewalk along exteriors of said cores;
trenches separating said cores; and
a transparent material in said trenches.