Stacked Pixel Photodetection Layout for Charge Storage and Noise
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Solution Overview
Problem
In stacked solid-state imaging devices, the increased number of pixel transistors required for multi-color photoelectric conversion regions leads to a reduction in charge storage area and noise characteristics, deteriorating image quality.
Innovation Solution
A photodetection device with a matrix arrangement of pixels, where each pixel includes a semiconductor substrate with a photoelectric conversion portion on one surface and pixel transistors on the opposing surface, separated by an insulating layer, allowing for a larger charge storage region and reduced transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple photoelectric conversion regions are stacked in one pixel region to increase color information acquisition, then the number of pixel transistors increases, but the charge storage area decreases and saturated charge amount characteristic deteriorates
Solution Approach 1:
The patent applies dimensionality change by moving pixel transistors from the two-dimensional plane of the semiconductor substrate to the third dimension (vertical direction) on the opposite surface. This allows multiple photoelectric conversion regions to be stacked in the vertical direction without increasing the number of transistors on the substrate plane, thereby preserving charge storage area while enabling multi-color information acquisition through stacked photodetection regions
2Quantity of substance
If the number of pixel transistors increases to handle multiple photoelectric conversion regions, then color information processing capability increases, but noise characteristics deteriorate
Solution Approach 1:
By relocating transistors to the vertical dimension on the opposite surface, the patent reduces the number of transistors on the substrate plane, which maintains larger transistor sizes and thus preserves noise characteristics while still enabling processing of multiple color channels through the stacked photoelectric conversion regions
3Quantity of substance
If pixel transistor size is reduced to accommodate more transistors in one pixel region, then the number of photoelectric conversion regions increases, but amplification transistor size decreases and noise characteristics deteriorate
Solution Approach 1:
The patent resolves this contradiction by moving transistors to the vertical dimension on the opposite surface, which allows multiple photoelectric conversion regions to be implemented without reducing transistor size on the substrate plane. This maintains adequate amplification transistor dimensions for acceptable noise characteristics while enabling multi-color photoelectric conversion
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 enhances image quality by maintaining noise characteristics and charge storage area, preventing deterioration in image quality due to increased pixel transistors.
Implementation Method 1
photoelectric conversion regions for photoelectrically converting light of respective wavelengths
Data Source
AI summary
A photodetection device according to an embodiment includes a plurality of pixels arranged in a matrix, in which each of the pixels includes a semiconductor substrate having a first surface and a second surface opposed to each other, a first photoelectric conversion portion disposed on the second surface side of the semiconductor substrate, an insulating layer covering the first surface of the semiconductor substrate, and at least one pixel transistor located on the first surface side of the semiconductor substrate with the insulating layer interposed therebetween.