Global Shutter Image Sensor Pixel With Aslant Diode Arrangement
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Solution Overview
Problem
Global shutter mode in image sensors has limitations such as low integration degree, leading to image distortion due to varying integration times across pixel rows, necessitating improvements for better performance.
Innovation Solution
A unit pixel design for image sensors operating in global shutter mode, featuring a photo diode area for light accumulation, a storage diode area for charge storage, and specific gate structures to manage charge transfer, along with a light shielding film and deep trench isolation to prevent light leakage and enhance integration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If global shutter mode is implemented, then image distortion is eliminated, but integration degree remains low
Solution Approach 1:
The pixel structure is segmented into distinct functional regions: photo diode area for light accumulation, storage diode area for charge storage, and dedicated gate structures (overflow gate, storage gate, transfer gate) for charge management. This segmentation enables global shutter operation while maintaining proper charge separation and control.
Solution Approach 2:
The photo diode area and storage diode area are arranged aslant (at an angle) with respect to row and column directions, rather than in conventional orthogonal arrangements. This angular arrangement optimizes space utilization and enables global shutter functionality within the available pixel area, improving integration density.
2Reliability
If photo diode and storage diode areas are separated, then charge storage is improved, but light absorptance may be reduced
Solution Approach 1:
The photo diode area and storage diode area are merged within a single unit pixel structure, sharing common elements such as the micro lens for light focusing and the floating diffusion for signal output. This integration ensures that light collected by the micro lens is efficiently directed to the photo diode while maintaining compact charge storage capability.
Solution Approach 2:
The aslant arrangement of photo diode and storage diode areas optimizes the spatial configuration within the pixel, allowing both areas to be efficiently illuminated by the micro lens while maintaining proper charge separation and storage functionality.
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
The design ensures uniform integration time across all pixel rows, reducing image distortion and improving light absorptance, thereby enhancing the overall performance and sensitivity of the image sensor.
Implementation Method 1
a photo diode configured to accumulate photocharges generated from incident light during a first period
Implementation Method 2
The photo diode may correspond to a micro lens that focuses the incident light
Data Source
AI summary
A unit pixel of an image sensor which operates in global shutter mode is provided. The unit pixel includes a photo diode area including a photo diode configured to accumulate photocharges generated from incident light during a first period and a storage diode area including a storage diode configured to receive and store the photocharges from the photo diode. The photo diode corresponds to a micro lens that focuses the incident light.