Imaging Pixel Charge Holding Structure for Saturation Control
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Solution Overview
Problem
Solid-state imaging devices face image degradation due to signal charge saturation in photoelectric converters, leading to decreased accuracy in phase-difference detection and image quality.
Innovation Solution
Incorporating a charge holding section and element isolation regions in the semiconductor substrate to manage signal charge, allowing it to flow from saturated photoelectric converters and preventing discharge into power supply lines, thus maintaining image linearity and phase-difference detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photoelectric converters are used for image capture, then image data can be obtained, but signal charge saturation causes image degradation and reduced detection accuracy
Solution Approach 1:
The pixel structure is segmented into multiple photoelectric converters (first and second photoelectric converters) within each pixel unit region. This segmentation allows independent charge generation and storage in each converter, preventing saturation-induced image degradation while maintaining detection accuracy through comparative phase measurement.
Solution Approach 2:
A transfer transistor is introduced as an intermediary component between the photoelectric converters and the floating diffusion region. This transfer transistor controls the timing and path of signal charge transfer, enabling precise management of charge flow to prevent saturation effects and maintain linear response characteristics.
2Adaptability or versatility
If signal charge is accumulated in photoelectric converters, then phase-difference detection is enabled, but saturation of signal charge degrades image linearity
Solution Approach 1:
The first and second photoelectric converters preliminarily accumulate signal charge separately before transfer to the floating diffusion region. This preliminary accumulation in isolated converters prevents saturation from affecting the overall pixel response, maintaining image linearity while enabling phase-difference detection through subsequent charge comparison.
Solution Approach 2:
The patent changes the operational parameters by introducing dual photoelectric converters with independent charge accumulation. This parameter change (from single to dual converters) increases the dynamic range and prevents saturation, thereby maintaining image linearity across varying light conditions while preserving phase-difference detection capability.
3Area of stationary object
If all pixels are used for phase-difference detection, then detection coverage is maximized, but signal charge management becomes complex
Solution Approach 1:
Adjacent pixels share common floating diffusion regions and transfer transistors, merging charge management resources. This merging approach allows all pixels to function as phase-difference detection pixels with full detection coverage while reducing overall device complexity through resource sharing and simplified charge management architecture.
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 solution effectively suppresses image degradation and maintains high resolution in phase-difference detection by managing signal charge saturation, ensuring all pixels can function as phase-difference detection pixels and improving manufacturing ease.
Implementation Method 1
a photodiode PD that performs photoelectric conversion on incident light
Data Source
AI summary
A solid-state imaging device includes a first semiconductor substrate, an isolation region, a charge holding section, and a charge accumulation section. The first semiconductor substrate is a substrate in which a photoelectric converter is provided for each of unit regions. The isolation region is provided to run through the first semiconductor substrate in a thickness direction and electrically isolates the unit regions from each other. The charge holding section is electrically coupled to the photoelectric converter and configured to receive signal charge from the photoelectric converter. The charge accumulation section is shared by two or more of the unit regions and is a section to which the signal charge is transferred from the photoelectric converter and the charge holding section of each of the unit regions sharing the charge accumulation section.