Global Shutter Pixel Storage Shielding to Prevent Signal Mixing
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Solution Overview
Problem
Current image sensors with global shutters face challenges in capturing fast-moving objects due to limitations in the design and operation of pixel units, particularly in the transfer and storage of image charges, which can lead to signal mixing and loss during the exposure and readout processes.
Innovation Solution
The image sensor design incorporates a shutter gate transistor, a photosensitive device, a transfer gate transistor, a storage device, and a driving circuit, where the storage device is optimized with a light shielding element and specific doping regions to efficiently store and transfer image charges, allowing for simultaneous exposure and readout without signal mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a memory element is added to each pixel for global shutter function, then the ability to capture fast-moving objects is improved, but the device complexity and signal loss increase
Solution Approach 1:
The pixel is divided into distinct functional regions: a photosensitive region for charge generation and a storage region for charge temporary storage. This segmentation allows the global shutter function to be implemented without requiring complex memory elements in every pixel, thereby reducing device complexity while maintaining the ability to capture fast-moving objects.
Solution Approach 2:
The memory function is extracted from individual pixels and consolidated into a shared storage region that serves multiple pixels. This approach eliminates the need for separate memory elements in each pixel, reducing overall device complexity while preserving the global shutter capability for capturing fast-moving objects.
2Productivity
If a memory element is added to each pixel for global shutter function, then the ability to capture fast-moving objects is improved, but signal loss occurs during transfer and storage
Solution Approach 1:
A transfer gate is introduced as an intermediary component between the photosensitive region and the storage region. This transfer gate enables controlled and efficient charge transfer, minimizing signal loss during the transition from charge generation to temporary storage, thereby maintaining high capture performance for fast-moving objects.
3Device complexity
If traditional pixel design is used, then device complexity is reduced, but signal mixing and loss occur during exposure and readout
Solution Approach 1:
The pixel is divided into distinct functional regions: a photosensitive region for charge generation and a storage region for charge temporary storage. This segmentation allows the global shutter function to be implemented without requiring complex memory elements in every pixel, thereby reducing device complexity while maintaining the ability to capture fast-moving objects.
Solution Approach 2:
The memory function is extracted from individual pixels and consolidated into a shared storage region that serves multiple pixels. This approach eliminates the need for separate memory elements in each pixel, reducing overall device complexity while preserving the global shutter capability for capturing fast-moving objects.
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 enables accurate and efficient capture of image charges, preventing signal loss and mixing, thereby improving the ability to capture fast-moving objects with reduced noise and increased image quality.
Implementation Method 1
a photosensitive device, a transfer gate transistor, a storage device
Data Source
AI summary
An image sensor includes a storage device, where the storage device includes a memory element, a first dielectric layer and a light shielding element. The memory element includes a storage node and a storage transistor gate, where the storage transistor gate is located over the storage node. The first dielectric layer is located over a portion of the storage transistor gate. The light shielding element is located on the first dielectric layer and includes a semiconductor layer. The semiconductor layer is electrically isolated from the memory element, where the light shielding element is overlapped with at least a part of a perimeter of the storage transistor gate in a vertical projection on a plane along a stacking direction of the memory element and the light shielding element, and the stacking direction is normal to the plane.