Solid-State Imaging Device Pixel Architecture for CDS and Global Shutter
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Solution Overview
Problem
Current solid-state imaging devices, such as CMOS-APS sensors, face challenges in achieving both correlated double sampling (CDS) and global electronic shutter functions simultaneously due to noise component correlation issues and high power consumption, leading to degraded image quality.
Innovation Solution
A solid-state imaging device with a configuration that includes a storage well, a transfer control element with a transfer gate and an electric charge-retaining region, and a diffusion layer as a transfer path, allowing for simultaneous CDS and global electronic shutter functions with low power consumption and easy manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CMOS-APS sensor uses sequential resetting to achieve CDS function, then noise components can be removed, but the global electronic shutter function cannot be achieved and image quality is degraded for rapidly moving objects
Solution Approach 1:
The patent divides the pixel structure into separate components: a photoelectric transducer for charge generation, a transfer control element with transfer gate for charge transfer control, and a floating diffusion region for signal readout. This segmentation allows independent optimization of CDS function (through transfer gate control) and global electronic shutter function (through simultaneous charge transfer capability), resolving the contradiction between noise removal and shutter functionality.
Solution Approach 2:
The transfer control element acts as an intermediary between the photoelectric transducer and the floating diffusion region. It enables precise control of charge transfer timing, allowing simultaneous achievement of CDS function (by controlling transfer timing for noise correlation) and global electronic shutter function (by enabling simultaneous transfer from all pixels), thus resolving the functional conflict.
2Adaptability or versatility
If the transfer transistor is occupied for global electronic shutter function in CMOS-APS sensor, then global electronic shutter can be achieved, but CDS function becomes incapable and image quality is degraded
Solution Approach 1:
The patent segments the charge transfer control functionality from the signal readout functionality. The transfer control element with transfer gate handles charge transfer (enabling global electronic shutter), while the floating diffusion region handles signal readout (enabling CDS function through sequential resetting). This segmentation allows both functions to operate independently without conflict.
Solution Approach 2:
The transfer gate voltage can be dynamically controlled to enable different operational modes. By adjusting the transfer gate voltage timing, the system can achieve simultaneous charge transfer from all pixels (global electronic shutter) while maintaining the ability to perform sequential resetting for CDS function, thus resolving the functional trade-off.
3Adaptability or versatility
If a modulation-on-substrate type sensor reads out signal components first followed by noise components, then global electronic shutter function can be achieved, but noise components cannot be removed precisely due to noncorrelation between signal and noise
Solution Approach 1:
The patent implements preliminary resetting of the floating diffusion region before charge transfer. This preliminary action ensures that the floating diffusion is in a known state, allowing precise correlation between signal and noise components during subsequent readout operations. The transfer control element then enables precise timing control to maintain noise correlation, resolving the precision issue.
Solution Approach 2:
The patent uses feedback mechanisms in the amplifier circuit to maintain correlation between signal and noise components. The amplifier reads out both signal and noise components with controlled timing, and the feedback ensures that noise components are properly correlated and removed, even when global electronic shutter function is active, thus resolving the precision problem.
4Adaptability or versatility
If a CCD sensor uses high driving voltage to achieve global electronic shutter function, then excellent image quality is obtained, but power consumption becomes high
Solution Approach 1:
The patent changes the voltage parameter from high voltage (CCD operation) to low voltage (CMOS operation). The transfer control element with transfer gate can achieve global electronic shutter function using low voltage CMOS transistors, maintaining the shutter capability while dramatically reducing power consumption compared to high voltage CCD operation.
Solution Approach 2:
The patent replaces the high voltage charge transfer mechanism of CCD with a low voltage CMOS transistor-based transfer control system. The transfer gate uses standard CMOS transistor switching to control charge transfer, substituting the high voltage mechanism with a low voltage electronic control mechanism, thus achieving global electronic shutter function with low power consumption.
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
Enables high-quality image capture with both CDS and global electronic shutter functions while maintaining low power consumption and simplifying the manufacturing process.
Implementation Method 1
a storage well for storing electric charge generated by a photoelectric transducer using incident light
Data Source
AI summary
A solid-state imaging device including a plurality of unit pixels, each of which includes: a storage well for storing electric charge generated by a photoelectric transducer using incident light; a transferring unit, which is formed on a top surface of a substrate, for transferring the electric charge to a floating diffusion region; and an amplifier for outputting a pixel signal that is amplified based on the electric charge transferred to the floating diffusion region, wherein: the transferring unit is a transfer control element having: a transfer gate that is provided on the substrate surface through an insulation film so that part of the transfer gate overlaps the storage well when the substrate is viewed from a direction orthogonal to the substrate surface; and an electric charge-retaining region for retaining the electric charge that is provided within the substrate and under the transfer gate; and further a diffusion layer that serves as a transfer path between the floating diffusion region and the electric charge-retaining region is provided under another diffusion layer of the substrate.