Image Sensor Reset Channel Gradient for Dual Conversion Gain
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Solution Overview
Problem
Current image sensors face challenges in achieving high optical and electric performance, particularly in varying light conditions, due to limitations in conversion gain and noise reduction during reset operations, which affect signal-to-noise ratio and integration density.
Innovation Solution
The implementation of a dual conversion gain transistor and a specific reset operation method that adjusts conversion gain and utilizes a potential gradient in the channel region of the reset transistor to minimize noise, allowing for efficient switching between high and low light modes without the need for additional memory elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single conversion gain mode is used, then the device complexity is reduced, but the adaptability to different light conditions deteriorates
Solution Approach 1:
The patent implements dual conversion gain modes that can be dynamically switched based on light conditions. The first conversion gain mode is used for bright light conditions, while the second conversion gain mode is used for dark light conditions, allowing the device to adapt dynamically to varying illumination environments without requiring multiple separate devices
Solution Approach 2:
The patent changes the conversion gain parameter between two distinct modes. By adjusting the conversion gain from a first value to a second value based on light intensity detection, the system achieves adaptability to different light conditions while maintaining a relatively simple device structure that can operate in both modes
2Object-affected harmful factors
If reset operation is performed without potential gradient, then the ease of operation is improved, but the noise level increases
Solution Approach 1:
The patent applies a potential gradient to the channel region of the reset transistor before and during the reset operation. This preliminary application of the potential gradient ensures that noise is minimized during the reset process, and the gradient is maintained throughout the reset operation to continuously suppress noise generation
Solution Approach 2:
The patent converts the potential gradient, which would normally create additional electrical activity, into a beneficial noise suppression mechanism. By carefully controlling the potential gradient in the channel region, the system transforms what could be a source of noise into a tool for reducing noise during reset operations
3Adaptability or versatility
If additional memory elements are added for mode switching, then the adaptability is improved, but the integration density decreases
Solution Approach 1:
The patent makes the existing transistors and nodes multi-functional. The first and second charge detection nodes serve both as photocharge storage regions and as elements involved in dual conversion gain operation. The reset transistor and dual conversion gain transistor work together to enable mode switching without requiring dedicated memory elements, achieving universality in component usage
Solution Approach 2:
The patent merges the functions of photocharge storage, conversion gain adjustment, and mode switching into a unified circuit architecture. By combining these functions into existing structural elements rather than adding separate components, the system achieves adaptability while maintaining high integration density
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 approach enhances the image sensor's optical and electric characteristics by reducing noise and maintaining a stable signal-to-noise ratio across different conversion gain modes, increasing integration density and efficiency.
Implementation Method 1
An image sensor is a device that converts optical signals into electrical signals
Data Source
AI summary
An image sensor and a method of operating the same are provided. The image sensor includes a semiconductor substrate of a first conductivity type; a photoelectric conversion region provided in the semiconductor substrate and doped to have a second conductivity type; a first floating diffusion region provided to receive photocharges accumulated in the photoelectric conversion region; a transfer gate electrode disposed between and connected to the first floating diffusion region and the photoelectric conversion region; a dual conversion gain transistor disposed between and connected to the first floating diffusion region and a second floating diffusion region; and a reset transistor disposed between and connected to the second floating diffusion region and a pixel power voltage region, wherein a channel region of the reset transistor has a potential gradient increasing in a direction from the second floating diffusion region toward the pixel power voltage region.