Image Sensor Storage Gate Shielding Layer Signal Mixing
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Solution Overview
Problem
Current image sensors with global shutters face challenges in capturing fast-moving objects due to the mixing of signals during exposure, as existing technologies do not effectively isolate and store image charges efficiently.
Innovation Solution
The image sensor design incorporates a photosensitive device, a storage device, and a driving circuit, where the storage device includes a P-N junction, a storage gate electrode, an etch stop layer, a shielding layer, and a protection layer to isolate and store image charges, preventing signal mixing and allowing for accurate readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a memory element is added to each pixel to enable global shutter function, then the ability to capture fast-moving objects is improved, but the device complexity and signal mixing issues worsen
Solution Approach 1:
The pixel is segmented into distinct functional regions: a photosensitive region for charge generation and a storage region for charge storage. This segmentation allows the global shutter function to be implemented without requiring complex memory elements within each pixel, as charges are stored in a separate region adjacent to the photosensitive region.
Solution Approach 2:
A transfer gate is introduced as an intermediary element between the photosensitive region and the storage region. This transfer gate controls the movement of photo-generated charges from the photosensitive region to the storage region, enabling the global shutter function while maintaining simpler pixel structures.
2Duration of action of moving object
If existing memory elements are used for charge storage, then global shutter function is achieved, but signal mixing during exposure occurs
Solution Approach 1:
The pixel structure is divided into spatially separated photosensitive region and storage region. This physical separation ensures that charges generated during exposure are stored in a distinct location, preventing signal mixing and improving signal isolation accuracy while maintaining charge storage duration.
Solution Approach 2:
The storage function is extracted from the photosensitive region and placed in a separate storage region. This extraction eliminates the interference between charge generation and charge storage processes, preventing signal mixing while achieving the required charge storage duration for global shutter operation.
3Adaptability or versatility
If photodiode and memory element are integrated in each pixel, then global shutter capability is improved, but manufacturing precision requirements worsen
Solution Approach 1:
The pixel is segmented into photosensitive region and storage region that can be formed using standard semiconductor fabrication processes. This segmentation approach allows for precise formation of each region independently, reducing the overall manufacturing precision requirements compared to integrating complex memory elements within each pixel.
Solution Approach 2:
The storage region serves multiple functions: it stores photo-generated charges during exposure and acts as an isolation region to prevent signal mixing. This multi-functionality reduces the need for additional specialized components, simplifying the overall pixel structure and reducing manufacturing precision requirements.
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 design enables efficient storage and readout of image charges, preventing signal mixing and ensuring accurate capture of fast-moving objects, thereby improving the image sensor's performance in capturing dynamic scenes.
Implementation Method 1
the storage device includes a P-N junction, a storage gate electrode, an etch stop layer, a shielding layer, and a protection layer to isolate and store image charges
Implementation Method 2
a photosensitive device, a storage device, and a driving circuit, where the storage device includes a P-N junction
Data Source
AI summary
A method of manufacturing an image sensor includes at least the following steps. A storage node is formed in a substrate. A gate dielectric layer, a storage gate electrode, and a first dielectric layer are sequentially formed over the substrate. A portion of the first dielectric layer is removed to form an opening. A protection layer and a shielding layer are sequentially filled into the opening. The protection layer laterally surrounds the shielding layer and at least a portion of the protection layer is located between the storage gate electrode and the shielding layer. A second dielectric layer is formed over the shielding layer.