Stacked Imaging Element Segmentation for kTC Noise Suppression
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Solution Overview
Problem
In stacked-type imaging elements, charges generated by photoelectric conversion in the first photoelectric conversion unit are difficult to completely deplete, leading to increased kTC noise and deteriorated image quality, and there is a need for improved charge transfer and simplified pixel configuration.
Innovation Solution
The imaging element incorporates a photoelectric conversion unit with a charge storage electrode spaced apart from the first electrode via an insulating layer, featuring multiple segments of photoelectric conversion units, insulating layers, and charge storage electrodes, allowing for a charge transfer gradient and complete depletion of charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photoelectric conversion unit is disposed on or above a semiconductor substrate, then the imaging element can achieve a stacked-type structure with multiple photoelectric conversion units, but complete depletion of the photoelectric conversion unit becomes difficult, leading to increased kTC noise and degraded image quality
Solution Approach 1:
The photoelectric conversion unit is divided into multiple segments stacked in the vertical direction, with each segment having its own charge storage electrode. This segmentation allows independent control and complete depletion of each segment, preventing charge accumulation that would otherwise degrade image quality and increase kTC noise.
Solution Approach 2:
A charge storage electrode is introduced as an intermediary component between the photoelectric conversion layer and the first electrode. This charge storage electrode accumulates and controls charges, enabling complete depletion of the photoelectric conversion unit while maintaining the stacked-type structure, thus resolving the contradiction between structural versatility and image quality reliability.
2Adaptability or versatility
If a photoelectric conversion unit is disposed on or above a semiconductor substrate, then the imaging element can achieve a stacked-type structure, but charge transfer becomes less reliable and more complex
Solution Approach 1:
The photoelectric conversion unit is segmented into multiple sections, with each segment having dedicated charge storage electrodes. This segmentation creates discrete charge transfer pathways, making the transfer process more controllable and reliable while enabling the stacked-type structure.
Solution Approach 2:
Charge storage electrodes serve as intermediary components that facilitate reliable charge transfer between the photoelectric conversion layer and external circuits. These intermediaries ensure complete and controlled charge transfer, preventing charge accumulation and enabling the complex stacked-type structure to function reliably.
3Device complexity
If conventional photoelectric conversion units are used without charge storage electrodes, then the structure is simpler, but complete depletion is difficult and kTC noise increases
Solution Approach 1:
Charge storage electrodes are introduced as intermediary components between the photoelectric conversion layer and the first electrode. These intermediaries enable complete depletion of the photoelectric conversion unit by providing controlled charge accumulation and transfer mechanisms, thereby suppressing kTC noise and improving image quality despite the increased structural complexity.
Solution Approach 2:
The introduction of charge storage electrodes changes the electrical parameters of the photoelectric conversion unit, specifically enabling complete depletion by controlling charge distribution. This parameter change allows the system to achieve better image quality and lower kTC noise, justifying the increased device complexity.
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 effectively suppresses kTC noise, improves image quality by ensuring complete charge depletion, and facilitates reliable charge transfer, while simplifying and miniaturizing the pixel structure.
Implementation Method 1
a photoelectric conversion layer (15) which is formed of N number of photoelectric conversion layer segments (151, 152, 153), and when irradiated with light, photoelectrically converts the light and generates charges
Data Source
AI summary
Provided is an imaging element including a photoelectric conversion unit formed by stacking a first electrode, a photoelectric conversion layer and a second electrode. The photoelectric conversion unit further includes a charge storage electrode which is disposed to be spaced apart from the first electrode and disposed opposite to the photoelectric conversion layer via an insulating layer. The photoelectric conversion unit is formed of N number of photoelectric conversion unit segments, and the same applies to the photoelectric conversion layer, the insulating layer and the charge storage electrode. An nth photoelectric conversion unit segment is formed of an nth charge storage electrode segment, an nth insulating layer segment and an nth photoelectric conversion layer segment. As n increases, the nth photoelectric conversion unit segment is located farther from the first electrode. A thickness of the insulating layer segment gradually changes from a first to Nth photoelectric conversion unit segment.