Image Sensor Pixels With Potential Barriers
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Solution Overview
Problem
Image sensor pixels suffer from parasitic light and charge leakage, leading to degraded image quality due to inefficiencies in global shutter efficiency and dark current, necessitating improved charge storage structures and configurations.
Innovation Solution
The implementation of image sensor pixels with potential barriers and capacitors that efficiently manage charge storage and transfer, utilizing transfer transistors and storage diodes to optimize charge handling and reduce leakage, enabling improved global shutter efficiency and dark current management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If charge storage regions are added to image sensor pixels to provide wide range functionalities, then pixel functionality is improved, but parasitic light and charge leakage increase leading to degraded image quality
Solution Approach 1:
The pixel is divided into multiple independent charge storage regions (first charge storage region and second charge storage region) with separate control mechanisms. Each storage region can be independently managed through dedicated transfer transistors and potential barriers, allowing selective charge transfer and storage while minimizing parasitic light and charge leakage effects on overall image quality
Solution Approach 2:
Potential barriers are introduced as intermediary structures between charge storage regions and other pixel components. These potential barriers act as mediators that control charge flow and prevent unwanted charge leakage while maintaining the functionality of global shutter operation, thereby reducing parasitic light effects without compromising pixel versatility
2Reliability
If global shutter efficiency is improved through charge storage regions, then image quality should improve, but dark current from storage regions degrades image quality
Solution Approach 1:
Multiple charge storage regions are segmented with independent transfer transistors and potential barriers, allowing separate control of charge transfer timing and pathways. This segmentation enables optimization of global shutter efficiency for each region while independently managing dark current through selective charge transfer operations
Solution Approach 2:
The potential barriers are configured with specific voltage levels that can be dynamically adjusted to control charge transfer timing. By changing the electrical parameters of the potential barriers and transfer transistors, the system optimizes global shutter efficiency while minimizing dark current accumulation in storage regions
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 enhances image quality by reducing parasitic light and charge leakage, improving global shutter efficiency, and providing scalable pixel structures for various functionalities like HDR and light flickering mitigation.
Implementation Method 1
The image pixels each contain a photodiode for generating charge in response to image light
Data Source
AI summary
An image sensor pixel may include a photodiode, one or more storage diodes, one or more potential barrier structures, one or more capacitors, and a floating diffusion region. The photodiode may be coupled to a storage diode and a first capacitor, and a first potential barrier structure may be interposed between the storage diode and the first capacitor. The photodiode may also be coupled to additional storage diodes and additional capacitors in a similar manner. Additionally, the photodiode may be directly separated from a given capacitor via a corresponding potential barrier structure. Each capacitor may store overflow charge from one or more storage diodes and/or the photodiode and may be connected to the floating diffusion via respective transistors.