Stacked Imaging Element Charge Storage Layout for Lower kTC Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In conventional stacked-type imaging elements, the first photoelectric conversion unit struggles to be completely depleted, leading to increased kTC noise, worsened random noise, and degraded image quality due to direct charge storage in the floating diffusion layer.
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 degraded 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 mediator enables complete charge depletion in the photoelectric conversion unit while preventing direct charge storage in the floating diffusion layer, thereby resolving the contradiction between structural simplicity and image quality.
Solution Approach 2:
The patent segments the charge storage function by creating a dedicated charge storage electrode separate from the floating diffusion layer. This segmentation allows the first photoelectric conversion unit to be completely depleted while providing a specific region for charge storage, improving image quality without significantly complicating the overall structure.
2Reliability
If a charge storage electrode is added to enable complete charge depletion, then image quality improves, but device complexity increases
Solution Approach 1:
The charge storage electrode serves multiple functions: it enables complete charge depletion in the photoelectric conversion unit, provides a dedicated charge storage region, and controls charge transfer timing. This multi-functionality justifies the added structural complexity by delivering significant improvements in image quality and noise reduction.
3Device complexity
If charges are stored directly in the floating diffusion layer, then the number of components is reduced, but kTC noise increases due to incomplete charge depletion
Solution Approach 1:
The charge storage electrode acts as a mediator that separates the charge depletion function from the charge storage function. This allows complete depletion of the first photoelectric conversion unit (reducing kTC noise) while maintaining a manageable component count through the strategic placement and design of the intermediary electrode.
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 charge storage portion, reducing kTC noise, improving image quality, and maintaining sensitivity by preventing a decrease in saturated charges.
Implementation Method 1
a photoelectric conversion unit formed by stacking a first electrode 21, a photoelectric conversion layer 23, and a second electrode 22 in this order from the light incident side, wherein light is incident from the second electrode side
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.