Layered Image Sensor Circuit for Global Shutter Data Retention
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Solution Overview
Problem
Current imaging devices face challenges in achieving high-speed operation, low power consumption, and high reliability, particularly in capturing moving objects with minimal distortion and data retention issues.
Innovation Solution
The imaging device incorporates a layered structure with a photoelectric conversion device and circuits, including transistors with metal oxide channels, enabling efficient data generation, storage, and reading, and utilizing OS transistors for low off-state current and long-term data retention, allowing for global shutter mode operation without additional memory circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional transistors are used in pixel circuits, then imaging speed can be improved, but data retention capability deteriorates
Solution Approach 1:
The invention divides the transistor channel into two distinct regions: a light-receiving region that contacts the photodiode for fast signal generation, and a light-shielding region that isolates the channel from incident light for stable threshold voltage and data retention. This segmentation allows each region to perform its specialized function optimally without interference
Solution Approach 2:
Different regions of the channel are given different properties: the light-receiving region has characteristics optimized for charge generation and transfer speed, while the light-shielding region has characteristics optimized for electrical stability and threshold voltage control. This local differentiation resolves the contradiction between speed and retention
2Reliability
If additional memory circuits are added for global shutter mode, then data retention capability is improved, but device complexity increases
Solution Approach 1:
The pixel circuit is designed so that the transistor with the light-shielding region serves dual functions: it acts as the pixel's transfer transistor for normal operation, and simultaneously provides global shutter functionality by maintaining stable charge storage capability during the light-shielding period. This eliminates the need for separate memory circuits
Solution Approach 2:
The invention merges the global shutter memory function into the existing pixel transistor structure by adding the light-shielding region, rather than implementing it as a separate component. This integration achieves data retention while minimizing circuit complexity
3Reliability
If more circuit components are added for data storage, then data retention capability is improved, but power consumption increases
Solution Approach 1:
The invention extracts the essential function needed for data retention (stable threshold voltage during light exposure) and implements it directly within the transistor structure itself through the light-shielding region, rather than adding separate storage components that would consume additional power
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 enables high-speed imaging, low power consumption, and reliable data retention, allowing for undistorted images of moving objects with reduced power usage and simplified circuitry.
Implementation Method 1
the first layer includes a photoelectric conversion device
Data Source
AI summary
An imaging device having a memory function is provided. Alternatively, an imaging device suitable for taking images of a moving object is provided. The imaging device includes a first to third layers; the second layer is provided between the first and the third layer; the first layer includes a photoelectric conversion device; the second layer includes a first and a second circuit; the third layer includes a third and a fourth circuit; the first circuit and the photoelectric conversion device have a function of generating imaging data; the third circuit has a function of reading the imaging data; the second circuit has a function of storing the imaging data read by the third circuit; the fourth circuit has a function of reading the imaging data stored in the second circuit; and the first circuit and the second circuit include a transistor including a metal oxide in a channel formation region.