Segmented Photoelectric Conversion Structure for Low-Noise Imaging Pixels
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Solution Overview
Problem
In solid-state imaging devices, the first photoelectric conversion unit's charges are difficult to completely deplete, leading to increased kTC noise and deteriorated image quality, and there is a need for easier and more reliable charge transfer and miniaturization of pixel region configurations.
Innovation Solution
The implementation of a photoelectric conversion unit with a charge accumulation electrode separated from the first electrode by an insulating layer, featuring N segments each, where the thickness and materials of the insulating and charge accumulation electrodes vary, allowing for a charge transfer gradient and efficient charge accumulation and transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If charges are accumulated directly in the first floating diffusion layer without complete depletion, then charge transfer is simplified, but kTC noise increases and image quality deteriorates
Solution Approach 1:
The first photoelectric conversion unit is divided into multiple segments (N≥2) with different insulating layer thicknesses, creating a gradient structure that enables complete charge depletion while maintaining manageable device complexity
Solution Approach 2:
Different regions of the photoelectric conversion unit are assigned different insulating layer thicknesses to create local variations in charge transfer characteristics, enabling complete depletion in charge accumulation regions while maintaining overall system functionality
2Ease of manufacture
If a uniform insulating layer is used in the photoelectric conversion unit, then manufacturing is simplified, but charge transfer efficiency is reduced
Solution Approach 1:
The insulating layer is designed with locally varying thicknesses (different for each segment), optimizing charge transfer efficiency in different regions while using standard fabrication techniques to maintain manufacturing feasibility
Solution Approach 2:
The insulating layer thickness is dynamically varied across different segments to create optimal charge transfer conditions for each region, transitioning from uniform to non-uniform structure based on functional requirements
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, reduces noise, and improves image quality by facilitating reliable charge transfer and simplifying the pixel region structure, preventing afterimages and transfer residuals.
Implementation Method 1
an imaging element using an organic semiconductor material for a photoelectric conversion layer can photoelectrically convert a specific color (wavelength band)
Implementation Method 2
the thickness and materials of the insulating and charge accumulation electrodes vary, allowing for a charge transfer gradient
Data Source
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AI summary
A solid-state imaging element includes a pixel including a first imaging element, a second imaging element, a third imaging element, and an on-chip micro lens 90. The first imaging element includes a first electrode 11, a third electrode 12, and a second electrode 16. The pixel further includes a third electrode control line VOA connected to the third electrode 12 and a plurality of control lines 62B connected to various transistors included in the second and third imaging elements and different from the third electrode control line VOA. In the pixel, a distance between the center of the on-chip micro lens 90 included in the pixel and any one of the plurality of control lines 62B included in the pixel is shorter than a distance between the center of the on-chip micro lens 90 included in the pixel and the third electrode control line VOA included in the pixel.