Stacked Imaging Element Charge Storage for Low-Noise Depletion
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Solution Overview
Problem
In stacked-type imaging elements, the first photoelectric conversion unit struggles to be completely depleted, leading to increased kTC noise and deteriorated image quality due to direct charge storage in the floating diffusion layer, whereas the second and third photoelectric conversion units can be depleted but result in random noise worsening.
Innovation Solution
Incorporating a charge storage electrode and a transfer control electrode opposite to the first electrode via an insulating layer, with the photoelectric conversion layer disposed above the charge storage electrode, allowing for complete charge depletion and controlled charge transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If charges are directly stored in the floating diffusion layer from the first photoelectric conversion unit, then the structure is simple, but the photoelectric conversion unit cannot be completely depleted leading to increased kTC noise and deteriorated image quality
Solution Approach 1:
The patent introduces a charge storage electrode as an intermediary component between the first photoelectric conversion unit and the floating diffusion layer. This charge storage electrode temporarily holds charges before transfer, enabling complete depletion of the photoelectric conversion unit while maintaining a manageable structural complexity through the addition of only one extra electrode layer.
2Reliability
If a charge storage electrode is added to enable complete charge depletion, then kTC noise is reduced, but the device structure becomes more complex
Solution Approach 1:
The patent combines the charge storage electrode with the existing electrode structure of the imaging element. The charge storage electrode is integrated into the stack of electrodes (first electrode, second electrode, third electrode) rather than being a completely separate component, thereby reducing the overall structural complexity increase while achieving complete charge depletion.
3Reliability
If the photoelectric conversion layer is disposed above the charge storage electrode via insulating layer, then complete charge depletion is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The insulating layer serves as a mediator that provides both electrical isolation and precise positioning for the photoelectric conversion layer above the charge storage electrode. This insulating layer acts as a spacer and alignment reference, enabling complete charge depletion while managing the manufacturing precision requirements through a standard semiconductor fabrication technique.
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 complete charge depletion in the photoelectric conversion layer, reducing kTC noise and random noise, thereby improving image quality and maintaining sensitivity by preventing a decrease in saturated charges.
Implementation Method 1
An imaging element using an organic semiconductor material for a photoelectric conversion layer can photoelectrically convert a specific color (wavelength band)
Data Source
AI summary
There is provided an imaging element includes a photoelectric conversion unit that includes a first electrode, a photoelectric conversion layer, and a second electrode, in which the photoelectric conversion unit further includes a charge storage electrode that has an opposite region opposite to the first electrode via an insulating layer, and a transfer control electrode that is opposite to the first electrode and the charge storage electrode via the insulating layer, and the photoelectric conversion layer is disposed above at least the charge storage electrode via the insulating layer.