Pixel Circuit Structure for Low-Illuminance Imaging Sensitivity
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Solution Overview
Problem
Existing imaging devices struggle to perform high-resolution imaging under low illuminance conditions due to reduced light-receiving areas of photoelectric conversion elements, leading to decreased sensitivity and increased noise.
Innovation Solution
The proposed imaging device incorporates a pixel circuit structure that includes transistors with oxide semiconductors and silicon-based transistors, along with a photoelectric conversion element. This configuration allows for efficient light detection even under low illuminance by utilizing high withstand voltage oxide semiconductors and silicon transistors optimized for amplification and switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light-receiving area of the photoelectric conversion element is reduced to increase pixel integration, then the resolution and integration density are improved, but the sensitivity to light decreases making imaging under low illuminance difficult
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional silicon-based semiconductors to oxide semiconductors, which have fundamentally different electrical characteristics including extremely low off-state current. This material parameter change enables the transistor to maintain minimal dark current even when the photoelectric conversion element is miniaturized, thereby preserving light sensitivity while achieving high pixel integration density
Solution Approach 2:
The patent employs a hybrid transistor structure combining oxide semiconductor layers with silicon-based semiconductor layers. The oxide semiconductor portion provides ultra-low off-state current characteristics, while the silicon-based portion ensures compatibility with existing CMOS fabrication processes. This composite material approach enables high integration density without sacrificing light sensitivity for low illuminance imaging
2Reliability
If transistors with conventional silicon-based semiconductors are used in pixel circuits, then the manufacturing process is mature and reliable, but the off-state current is relatively high which limits further miniaturization and integration
Solution Approach 1:
The transistor structure is segmented into distinct functional regions: an oxide semiconductor layer forming the channel region for ultra-low off-state current, and silicon-based semiconductor regions for source/drain contacts and interconnection. This segmentation allows each material to perform its optimal function while maintaining compatibility with existing manufacturing processes
Solution Approach 2:
The oxide semiconductor layer is formed and processed beforehand using established sputtering and annealing techniques, creating a pre-prepared low-leakage channel structure. Subsequent silicon-based layer formation and patterning then proceed using conventional CMOS processes, ensuring manufacturing reliability while achieving the low off-state current necessary for high integration
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 imaging device achieves high light detection sensitivity, enabling fast and reliable imaging under low illuminance conditions while maintaining high resolution and low noise levels.
Implementation Method 1
a photoelectric conversion element, wherein one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the first transistor
Data Source
AI summary
A highly sensitive imaging device that can perform imaging even under a low illuminance condition is provided. One electrode of a photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of a first transistor and one of a source electrode and a drain electrode of a third transistor. The other of the source electrode and the drain electrode of the first transistor is electrically connected to a gate electrode of the second transistor. The other electrode of the photoelectric conversion element is electrically connected to a first wiring. A gate electrode of the first transistor is electrically connected to a second wiring. When a potential supplied to the first wiring is HVDD, the highest value of a potential supplied to the second wiring is lower than HVDD.