# US 2008/0188028 A1 · Photodiode and phototransistor

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- Number: US 2008/0188028 A1
- Document ID: US20080188028A1
- Status: Published application
- Kind: A1
- Application number: 12/060,968
- Filed: 2008-04-02
- Published: 2008-08-07
- Earliest claimed: 2005-08-09
- Assignees: Rohm Co., Ltd.
- Inventors: Yushi SEKIGUCHI
- Web page: https://patentgrep.com/patent/US20080188028A1

## CPC

- H10F 30/222: the potential barrier being a PN heterojunction
- H10F 77/147: {Shapes of bodies}
- Y02E 10/50: Photovoltaic [PV] energy
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A phototransistor includes a first-conduction-type lower region, a second-conduction-type upper region disposed on the first region, a second-conduction-type electrode contact region of a high concentration disposed at a surface inside of the upper region and is connected to an electrode so as to transmit a signal, a first-conduction-type first shield region of a high concentration disposed at the surface of the upper region and spaced at an interval from the electrode contact region and connected to a ground potential, and a first-conduction-type second shield region of a low concentration disposed between the electrode contact region and the first shield region at the surface of the upper region so as to surround the electrode contact region, and further, is connected to the ground potential.

## Claims

### Claim 1

A method for making a photodiode comprising the steps of:
providing a first-conduction-type lower region;
forming a second-conduction-type upper region on the lower region;
implanting first-conduction-type impurities in a surface of the upper region except for a region corresponding to a second-conduction-type electrode contact region;
implanting a high concentration of second-conduction-type impurities in the electrode contact region; and
further implanting first-conduction-type impurities in the surface of the upper region except for a region corresponding to the electrode contact region and a region surrounding the electrode contact region thereby creating a first shield region of a high concentration of the first-conduction-type impurities; wherein
the region surrounding the electrode contact region is a second shield region of a low concentration of the first-conduction-type impurities.

### Claim 2 (depends on 1)

A method for making a phototransistor comprising the steps of:
forming a device separation region around a photodiode region;
providing the photodiode made by the method of claim 1 within the photodiode region;
arranging an output transistor outside of the photodiode region and separated from the photodiode region by the device separation region; and
amplifying a signal output from the photodiode via the output transistor.

### Claim 3 (depends on 2)

The method for making a phototransistor according to claim 2, wherein the electrode contact region is arranged at a peripheral edge of the photodiode region and adjacent to the device separation region.

### Claim 4 (depends on 3)

The method for making a phototransistor according to claim 3, further comprising:
etching a trench in the device separation region from the surface of the upper region in a direction towards the lower region; and
electrically connecting the second shield region and the lower region to each other along the trench.

### Claim 5 (depends on 4)

The method for making a phototransistor according to claim 4, wherein the step of electrically connecting the second shield region and the lower region includes:
providing an electrical connection region on an entire circumference of an interface between the trench and the upper region, and the first shield region is connected to the lower region via the electrical connection region.