Stacked Imaging Element Structure for Hydrogen-Blocked Charge Transfer
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Solution Overview
Problem
Stacked imaging elements with organic photoelectric conversion layers face challenges in completely depleting electric charge, leading to increased kTC noise and random noise, which deteriorates image quality due to the direct accumulation of charge in the floating diffusion layer.
Innovation Solution
Incorporating a separation groove in the interlayer insulating layer between the semiconductor substrate and the photoelectric converter, with a hydrogen block layer covering the side and bottom surfaces, to prevent hydrogen entry and reduce oxygen defects in the oxide semiconductor material, thereby enhancing the stability and reliability of the imaging element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an organic photoelectric conversion layer is used to directly accumulate electric charge in a floating diffusion layer, then the structure is simplified and manufacturing is easier, but the photoelectric converter cannot be completely depleted leading to increased kTC noise and random noise
Solution Approach 1:
An electric charge accumulation electrode is introduced as an intermediary component between the organic photoelectric conversion layer and the floating diffusion layer. This electrode temporarily stores electric charge during photoelectric conversion, enabling complete depletion of the photoelectric converter while maintaining the simplified organic layer structure. The intermediary electrode resolves the contradiction by providing a charge storage mechanism that prevents direct accumulation in the floating diffusion layer.
2Productivity
If a lower semiconductor layer made of oxide semiconductor material is added to prevent charge recombination and increase transfer efficiency, then charge transfer efficiency is improved, but the oxide semiconductor material is easily reduced by hydrogen causing oxygen defects and decreased operation stability
Solution Approach 1:
A hydrogen block layer is introduced to preemptively prevent hydrogen from reaching the oxide semiconductor material in the lower semiconductor layer. This preliminary protective action counteracts the harmful effect of hydrogen reduction before it can occur, maintaining the oxygen stoichiometry and operational stability of the oxide semiconductor while preserving its high charge transfer efficiency.
3Productivity
If the photoelectric converter structure is enhanced with multiple layers to prevent charge recombination, then charge transfer efficiency increases, but the device complexity increases
Solution Approach 1:
The photoelectric converter is segmented into functionally distinct layers: an organic photoelectric conversion layer for charge generation, a lower semiconductor layer for efficient charge transfer, and an electric charge accumulation electrode for temporary storage. This segmentation allows each layer to be optimized for its specific function, achieving high charge transfer efficiency while managing complexity through clear functional division rather than monolithic structure.
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
The solution effectively suppresses hydrogen entry, reducing oxygen defects and improving the operation stability of the imaging element, leading to increased reliability and improved image quality by minimizing noise and enhancing charge transfer efficiency.
Implementation Method 1
an organic photoelectric conversion layer including an organic semiconductor material is stacked on a semiconductor substrate including a photodiode embedded and formed therein
Implementation Method 2
The first hydrogen block layer covers a top and a side surface of the photoelectric conversion layer and a side surface of the electric charge accumulation layer
Data Source
AI summary
An imaging element according to an embodiment of the present disclosure includes: a semiconductor substrate having an effective pixel region in which a plurality of pixels is disposed and a peripheral region provided around the effective pixel region; a photoelectric converter; a first hydrogen block layer; an interlayer insulating layer; and a separation groove. The photoelectric converter includes a first electrode, a second electrode, and an electric charge accumulation layer and a photoelectric conversion layer. The first electrode is provided on a light receiving surface side of the semiconductor substrate and includes a plurality of electrodes. The second electrode is disposed to be opposed to the first electrode. The electric charge accumulation layer and the photoelectric conversion layer are stacked and provided in order between the first electrode and the second electrode and extend in the effective pixel region. The first hydrogen block layer covers a top and a side surface of the photoelectric conversion layer and a side surface of the electric charge accumulation layer. The interlayer insulating layer is provided between the semiconductor substrate and the photoelectric converter. The separation groove separates the interlayer insulating layer in at least a portion of a region between the effective pixel region and the peripheral region. The separation groove has a side surface and a bottom surface covered with the first hydrogen block layer.