Multi-Diffusion Pixel Structure for High Dynamic Range Imaging
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Solution Overview
Problem
Existing imaging devices face challenges in increasing dynamic range while reducing dark current, as previously proposed methods do not effectively achieve both goals simultaneously.
Innovation Solution
The imaging device incorporates a semiconductor substrate with specific diffusion regions and transistors that directly accumulate charges, eliminating the need for a transfer transistor and enhancing capacitive elements to reduce dark current and increase dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional photodiode structures are used to increase dynamic range, then charge accumulation capacity is improved, but dark current increases
Solution Approach 1:
The photodiode is divided into multiple independent diffusion regions (first diffusion region for photoelectric conversion, second diffusion region for charge accumulation) with different functions. This segmentation allows each region to be optimized independently - the first region for maximizing light conversion while the second region for charge storage, thereby increasing overall dynamic range without proportionally increasing dark current from a single large structure
Solution Approach 2:
The charge accumulation function is extracted from the photoelectric conversion region and placed in a separate second diffusion region. By taking out the charge accumulation capacity from the primary photodiode structure, the patent enables independent optimization of photoelectric conversion efficiency and charge storage capacity, allowing dynamic range expansion without the dark current penalties associated with enlarging the photoelectric conversion region itself
2Area of moving object
If pixel size is reduced to increase resolution, then device integration is improved, but dynamic range decreases
Solution Approach 1:
The patent transitions from a single-region planar structure to a multi-region vertical structure with distinct functional zones. By stacking the first diffusion region (photoelectric conversion) and second diffusion region (charge accumulation) in different spatial dimensions within the semiconductor substrate, the patent achieves enhanced charge accumulation capacity and dynamic range without increasing the lateral pixel footprint, thus maintaining high resolution while expanding dynamic range
3Adaptability or versatility
If transfer transistors are used to move charges, then charge transfer flexibility is improved, but device complexity and dark current increase
Solution Approach 1:
The patent removes the transfer transistor component from the pixel structure by directly connecting the first diffusion region to the second diffusion region. This extraction of the active transfer mechanism eliminates the associated dark current and device complexity while maintaining charge transfer capability through the passive diffusion connection, thereby simplifying the overall device architecture
Solution Approach 2:
The patent merges the charge generation and charge accumulation functions into a single integrated structure where the first and second diffusion regions are directly connected. By combining these functions without intermediate transistors, the patent reduces device complexity and eliminates transistor-induced dark current while preserving the essential charge transfer capability needed for operation
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 effectively reduces dark current and increases the dynamic range of the imaging device, allowing for larger photoelectric conversion units and improved charge accumulation efficiency.
Implementation Method 1
a first diffusion region that is in contact with the semiconductor region, that includes an impurity of a second conductivity type different from the first conductivity type, and that converts incident light into charges
Data Source
AI summary
An imaging device having a semiconductor substrate including: a semiconductor region including an impurity of a first conductivity type, a first diffusion region that is in contact with the semiconductor region, that includes an impurity of a second conductivity type different from the first conductivity type, and that converts incident light into charges, and a second diffusion region that includes an impurity of the second conductivity type and that directly accumulates at least a part of the charges generated in the first diffusion region. The imaging device further includes a contact plug in contact with the second diffusion region, and a capacitive element electrically connected to the second diffusion region through the contact plug.