Dual Conversion Gain Pixel Capacitor for Wider Dynamic Range
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Solution Overview
Problem
Existing image sensors face challenges in providing sufficient capacitance to the floating diffusion region, which limits the conversion gain and dynamic range of pixel signals.
Innovation Solution
The implementation of a first dual conversion gain (DCG) transistor and capacitor, along with a higher permittivity insulating layer, enhances the capacitance of the floating diffusion region, thereby increasing the conversion gain and dynamic range of pixel signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitor structure is used to provide capacitance to the floating diffusion region, then the device complexity is low, but the conversion gain and dynamic range are limited due to insufficient capacitance
Solution Approach 1:
The patent changes the permittivity parameter of the insulating layer by introducing a high-permittivity dielectric material between the first and second electrodes of the DCG capacitor. This parameter change increases the capacitance value without requiring additional capacitor structures, thereby improving conversion gain while maintaining device complexity at an acceptable level.
Solution Approach 2:
The patent employs a composite insulating layer structure combining a first insulating layer and a second insulating layer with different permittivities. The second insulating layer has higher permittivity than the first, creating a composite dielectric structure that achieves enhanced capacitance through material composition rather than structural complexity.
2Reliability
If the capacitance of the DCG capacitor is increased to expand dynamic range, then the signal-to-noise ratio improves, but the manufacturing complexity increases
Solution Approach 1:
The patent achieves increased DCG capacitor capacitance by changing the permittivity parameter of the insulating layer material. This approach increases the signal-to-noise ratio through enhanced capacitance while avoiding complex manufacturing processes, as the high-permittivity layer can be integrated into the existing capacitor structure using standard semiconductor fabrication techniques.
3Adaptability or versatility
If additional capacitance is provided to the floating diffusion region, then the dynamic range is expanded, but the pixel area increases
Solution Approach 1:
The patent expands the dynamic range by changing the permittivity parameter of the insulating layer in the DCG capacitor, which increases capacitance without requiring additional pixel area. This parameter-based solution allows the same physical space to provide enhanced capacitance, avoiding pixel area expansion while achieving greater adaptability in terms of dynamic range.
Solution Approach 2:
The patent introduces a vertical dimension solution by stacking the high-permittivity insulating layer between the first and second electrodes of the DCG capacitor. This vertical integration approach increases capacitance in the third dimension rather than expanding the pixel area in the planar dimension, thereby expanding dynamic range without increasing pixel footprint.
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 improves the signal-to-noise ratio and expands the dynamic range of the imaging device by providing additional capacitance to the floating diffusion region, enhancing the performance of image sensors in various applications.
Implementation Method 1
a photoelectric conversion device for generating pixel signals each having a size corresponding to illuminance and generating photo charges corresponding to the illuminance
Implementation Method 2
a second insulating layer between the first electrode and the second electrode, wherein a permittivity of the second insulating layer is higher than a permittivity of the first insulating layer
Data Source
AI summary
An imaging device comprises a pixel including a photoelectric conversion device for generating pixel signals, a floating diffusion region, a first dual conversion gain (DCG) transistor for providing additional capacitance to the floating diffusion region, and a first DCG capacitor connected to the floating diffusion region through the first DCG transistor; and an analog-digital converter (ADC) for converting the pixel signals into image data, wherein the pixel includes a first metal layer including a first DCG gate electrode of the first DCG transistor and a first electrode of the first DCG capacitor, a second metal layer including a dual conversion line that supplies a first DCG gate signal to the first DCG gate electrode, and a second electrode overlapping the first electrode, a first insulating layer between the first DCG gate electrode and the dual conversion line, and a second insulating layer between the first electrode and the second electrode.