Image Sensor Pinned Diode kTC Noise Reduction

Solution Overview

Problem

Conventional image sensors face challenges in achieving low-noise charge reset and integration due to kTC noise generation, which limits their ability to operate in global shutter mode without time skew and introduces noise in signal processing.

Innovation Solution

The implementation of a charge-integrating pinned diode and charge-storage pinned diode configuration with a fill-and-spill charge input scheme, where charge is transferred over a potential barrier with lower potential, reducing overall noise and enabling global shutter operations with minimal kTC-reset noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a reset transistor is used to drain charge from the floating diffusion node, then the pixel can be reset before a subsequent integration cycle, but kTC-reset noise is generated

Engineering Contradiction:

Improvereset operationVSAvoidkTC-reset noise

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The pixel is divided into two separate nodes: a charge integration node for collecting photo-generated charge and a charge detection node (floating diffusion) for signal readout. This segmentation allows the integration node to be reset independently without affecting the detection node, thereby eliminating kTC-reset noise from the signal path while maintaining the ability to perform reset operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A transfer gate is introduced as an intermediary component between the charge integration node and the charge detection node. This transfer gate enables controlled charge transfer from the integration node to the detection node, allowing the integration node to be reset independently without directly resetting the detection node, thus avoiding kTC noise generation in the signal path.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If charge is transferred from the charge integration node to the charge detection node, then the signal can be read out, but significant kTC noise is introduced into the signal

Engineering Contradiction:

Improvesignal readoutVSAvoidkTC noise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The pixel is divided into two separate nodes: a charge integration node for collecting photo-generated charge and a charge detection node (floating diffusion) for signal readout. This segmentation allows the integration node to be reset independently without affecting the detection node, thereby eliminating kTC-reset noise from the signal path while maintaining the ability to perform reset operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transfer gate between the charge integration node and the charge detection node is dynamically controlled to transfer charge only when needed for readout. This dynamic control ensures that the detection node is reset independently of the integration node, preventing kTC noise from being introduced during the charge transfer process while maintaining efficient signal readout capability.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If the same node is used for both charge integration and charge detection, then the pixel structure is simplified, but reset operations generate noise in the signal

Engineering Contradiction:

Improvepixel structureVSAvoidreset noise

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The pixel is divided into two separate nodes: a charge integration node for collecting photo-generated charge and a charge detection node (floating diffusion) for signal readout. This segmentation allows the integration node to be reset independently without affecting the detection node, thereby eliminating kTC-reset noise from the signal path while maintaining the ability to perform reset operations.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration significantly reduces noise levels during readout and allows for simultaneous reset and charge integration across the pixel array, enhancing sensor sensitivity and dynamic range while enabling global shutter mode operation.

Implementation Method 1

an organic photoelectric conversion layer (sometimes referred to as a charge generating layer)... convert light into charge

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS9601538B2Image sensors with photoelectric films

Publication Date: 2017.03.21 SEMICON COMPONENTS IND LLC

AI summary

An image sensor with an organic photoelectric film for converting light into charge may be provided. The image sensor may include an array of image sensor pixels. Each image sensor pixel may include a charge-integrating pinned diode that collects photo-generated charge from the photoelectric film during an integration period. An anode electrode may be coupled to an n+ doped charge injection region in the charge-integrating pinned diode and may be used to convey the photo-generated charge from the photoelectric film to the charge-integrating pinned diode. Upon completion of a charge integration cycle, a first transfer transistor gate may be pulsed to move the charge from the charge-integrating pinned diode to a charge-storage pinned diode. The charge may be transferred from the charge-storage pinned diode to a floating diffusion node for readout by pulsing a gate of a second charge transfer transistor.