# US 5,705,836 A · Efficient charge transfer structure in large pitch charge coupled device

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- Number: US 5,705,836 A
- Document ID: US5705836A
- Status: Granted
- Kind: A
- Application number: 08/445,994
- Filed: 1995-05-22
- Granted: 1998-01-06
- Earliest claimed: 1995-05-22
- Assignees: Dalsa, Inc.
- Inventors: Suhail Agwani; Stacy Royce Kamasz; Michael George Farrier
- Web page: https://patentgrep.com/patent/US5705836A

## CPC

- H10F 39/153: {Two-dimensional or three-dimensional array CCD image sensors}
- H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
- H04N 25/771: comprising storage means other than floating diffusion
- H04N 25/772: comprising A/D, V/T, V/F, I/T or I/F converters
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

In a charge coupled device having a plurality of output structures, the plurality of output structures including first and second output structures, a channel structure is defined in a channel region beneath a gate electrode and coupled to each of the plurality of output structures. The channel structure includes a plurality of area structures, each area structure being characterized by a uniform potential which is different from the potential characterizing each of the other area structures. The plurality of area structures are arranged within the channel region to define a first increasing stepped potential gradient from any point within the channel region to the first output structure and define a second increasing stepped potential gradient from any point within the channel region to the second output structure. A length of each area structure traversing the area structure in a first gradient direction is less than or equal to a first critical length, the first critical length being defined by a first desired transfer time for transferring charge to the first output structure. A length of each area structure traversing the area structure in a second gradient direction is less than or equal to a second critical length, the second critical length being defined by a second desired transfer time for transferring charge to the second output structure.

## Claims

### Claim 1

In a charge coupled device having a plurality of output structures, the plurality of output structures including first and second output structures, a channel structure defined in a channel region beneath a gate electrode and coupled to each of the plurality of output structures, the channel structure being formed with:
a first dopant species distributed non-uniformly therein; and
a second dopant species distributed non-uniformly therein,
wherein the channel structure is characterized by a two-dimensional potential gradient, the two-dimensional potential gradient defining a first increasing potential gradient from a point within the channel region to the first output structure and a second increasing potential gradient from the point within the channel region to the second output structure,
wherein the channel structure comprises a plurality of area structures, each area structure being characterized by a uniform potential which is different from the potential characterizing each of the other area structures,
wherein the plurality of area structures are arranged within the channel region to define the first increasing potential gradient as a first increasing stepped potential gradient and define the second increasing potential gradient as a second increasing stepped potential gradient, and
wherein the plurality of area structures consists of first, second and third area structures, each area structure containing a unique combination of at least one of the first dopant species and the second dopant species.

### Claim 2 (depends on 1)

The structure of claim 1, wherein:
the first area structure contains the first dopant species uniformly distributed therein;
the second area structure contains both the first and second dopant species uniformly distributed therein; and
the third area structure contains the second dopant species uniformly distributed therein.

### Claim 3 (depends on 1)

The structure of claim 1, wherein the channel structure and the gate electrode comprise a photo-sensitive structure.

### Claim 4

In a charge coupled device having a plurality of output structures, the plurality of output structures including first, second and third output structures, a channel structure defined in a channel region beneath a gate electrode and coupled to each of the plurality of output structures, the channel structure comprising:
a plurality of area structures, each area structure being characterized by a uniform potential which is different from the potential characterizing each of the other area structures, the plurality of area structures being arranged within the channel region to define a first increasing stepped potential gradient in a first gradient direction from a point within the channel region to the first output structure and to define a second increasing stepped potential gradient in a second gradient direction from the point within the channel region to the second output structure and to define a third increasing stepped potential gradient in a third gradient direction from the point within the channel region to the third output structure, the first gradient direction being non-parallel to the second gradient direction, the third gradient direction being non-parallel to both the first and second gradient directions.

### Claim 5 (depends on 4)

The structure of claim 4, wherein:
a length of each area structure traversing the area structure in the first gradient direction is less than or equal to a first critical length, the first critical length being defined so that at least one of self-induced drift and fringing field drift is the dominant charge transfer mechanism during a first desired transfer time for transferring charge to the first output structure;
a length of each area structure traversing the area structure in the second gradient direction is less than or equal to a second critical length, the second critical length being defined so that at least one of self-induced drift and fringing field drift is the dominant charge transfer mechanism during a second desired transfer time for transferring charge to the second output structure; and
a length of each area structure traversing the area structure in the third gradient direction is less than or equal to a third critical length, the third critical length being defined so that at least one of self-induced drift and fringing field drift is the dominant charge transfer mechanism during a third desired transfer time for transferring charge to the third output structure.

### Claim 6 (depends on 4)

The structure of claim 4, wherein the channel structure and the gate electrode comprise a photo-sensitive structure.

### Claim 7

In a charge coupled device having a plurality of output structures, the plurality of output structures including first and second output structures, the first output structure including first and second reset diodes, a channel structure defined in a channel region beneath a gate electrode and coupled to each of the plurality of output structures, the channel structure being formed with a first dopant species distributed non-uniformly therein so that the channel structure is characterized by a two-dimensional potential gradient, the two-dimensional potential gradient defining a first increasing potential gradient in a first gradient direction from a point within the channel region to the first output structure and a second increasing potential gradient in a second gradient direction from the point within the channel region to the second output structure, the first gradient direction being non-parallel to the second gradient direction, the first increasing potential gradient defines a path in a direction of increasing potential from the point within the channel region to a nearest one of the first reset diode and the second reset diode.

### Claim 8 (depends on 7)

The structure of claim 7, wherein:
the second output structure comprises a vertical charge coupled device shift register; and
the second increasing potential gradient defines a second path in a direction of increasing potential from the point within the channel region to the vertical charge coupled device shift register.

### Claim 9 (depends on 7)

The structure of claim 7, wherein the channel structure and the gate electrode comprise a photo-sensitive structure.