Image Sensor Floating Diffusion Segmentation for Charge Transfer
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Solution Overview
Problem
Image sensors with vertical transfer gate electrodes face inefficiencies in charge transfer from photodiodes to floating diffusions, leading to image lag due to variations in charge transfer paths.
Innovation Solution
The image sensor design includes a floating diffusion with multiple areas disposed on different sides of the transfer gate electrode, connected through conductive lines, to reduce variations in charge transfer paths and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If vertical transfer gate electrodes are used to improve pixel integration, then device integration is improved, but charge transfer efficiency deteriorates leading to image lag
Solution Approach 1:
The floating diffusion is divided into multiple areas (first area and second area) disposed on different sides of the transfer gate electrode. This segmentation creates multiple charge transfer paths from the photodiode to different regions of the floating diffusion, ensuring complete charge transfer and eliminating image lag while maintaining vertical transfer gate structure for high integration.
2Device complexity
If single-area floating diffusion is used, then device structure is simple, but charge transfer completeness deteriorates causing image lag
Solution Approach 1:
The floating diffusion is segmented into multiple areas (first area and second area) positioned on opposite sides of the transfer gate electrode. This segmentation ensures that charges generated in the photodiode can be completely transferred to the floating diffusion through multiple paths, preventing charge retention and image lag.
Solution Approach 2:
Different areas of the floating diffusion are positioned at specific locations relative to the transfer gate electrode to optimize charge collection. The first and second areas are disposed on different sides of the transfer gate electrode, creating localized charge collection zones that ensure complete charge transfer from the photodiode.
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 improves charge transfer efficiency, reducing image lag by ensuring complete charge transfer from one frame to the next, thereby enhancing image quality.
Implementation Method 1
a photodiode configured to generate charges in response to incident light
Data Source
AI summary
Image sensors and image processing devices including the image sensors are provided. The image sensors may include a semiconductor substrate including a plurality of pixel areas, a photodiode provided in the semiconductor substrate in one of the plurality of pixel areas and a transfer transistor having a transfer gate electrode. A portion of the transfer gate electrode may be in the semiconductor substrate and may extend toward the photodiode. The image sensors may also include a floating diffusion configured to accumulate charges transferred from the photodiode by the transfer transistor, and the floating diffusion may include a first area and a second area disposed on different sides of the transfer gate electrode.