Pixel Isolation Structure for Full Well Capacity in Imaging Sensors
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Solution Overview
Problem
Current imaging devices face challenges in improving imaging performance, particularly in acquiring both imaging and parallax information while maintaining high integration of unit pixels to enhance imaging quality, which is hindered by issues such as electron mixing and reduced dynamic range due to finer pixel sizes and isolation structures.
Innovation Solution
The imaging device incorporates a semiconductor substrate with a matrix of pixels and photoelectric converters, featuring an electrode layer on the light incident surface, inter-pixel isolation, and in-pixel isolation sections, which form an inversion region to manage electron overflow and control potential, thereby improving full well capacity and phase-difference detection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is reduced to increase integration of unit pixels, then productivity and imaging quality are improved, but electron mixing occurs and dynamic range is reduced
Solution Approach 1:
The pixel is divided into multiple photoelectric converters (first and second photoelectric converters) within a single pixel unit. This segmentation allows each converter to independently collect photons, preventing electron mixing while maintaining high integration. The isolation sections further segment the pixel structure to electrically isolate adjacent photoelectric converters, solving the electron mixing problem that arises from reduced pixel sizes.
Solution Approach 2:
The patent extends the isolation structure in the depth dimension by forming isolation sections that protrude from the light-receiving surface toward the interior of the pixel. This three-dimensional isolation approach effectively separates adjacent photoelectric converters without reducing the two-dimensional pixel area, thereby maintaining full well capacity while preventing electron mixing.
2Reliability
If isolation structures are added to prevent electron mixing, then reliability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The isolation section serves multiple functions simultaneously: it electrically isolates adjacent photoelectric converters, optically isolates them to prevent crosstalk, and defines the pixel boundary. By merging these isolation functions into a single integrated structure, the patent reduces device complexity compared to using separate structures for each function.
Solution Approach 2:
The isolation section is designed as a multi-functional element that performs electrical isolation, optical isolation, and structural definition roles. This universal structure eliminates the need for additional dedicated isolation components, thereby simplifying the overall device architecture while maintaining reliable electron separation.
3Reliability
If pixel area is increased to improve full well capacity, then imaging performance is improved, but integration density and productivity decrease
Solution Approach 1:
Multiple photoelectric converters are nested within a single pixel unit, with each converter capable of independently collecting photons. This nesting arrangement effectively increases the total light-collecting area (full well capacity) within the same pixel footprint, thereby improving imaging performance without reducing integration density.
Solution Approach 2:
The patent utilizes the depth dimension by forming isolation sections that protrude into the pixel interior, creating a three-dimensional structure. This allows multiple photoelectric converters to be arranged in a compact configuration without increasing the two-dimensional pixel area, thereby maintaining high integration density while increasing full well capacity.
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 imaging performance by increasing full well capacity without increasing pixel area, stabilizing phase-difference detection, and reducing noise, even under high illuminance conditions, thus improving autofocus and imaging quality.
Implementation Method 1
a plurality of photoelectric converters that generates, through photoelectric conversion, an electric charge corresponding to an amount of received light for each of the pixels
Data Source
AI summary
An imaging device according to an embodiment of the present disclosure includes: a semiconductor substrate having a first surface and a second surface that are opposed to each other, and including a plurality of pixels and a plurality of photoelectric converters, the plurality of pixels disposed in a matrix, and the plurality of photoelectric converters that generates, through photoelectric conversion, an electric charge corresponding to an amount of received light for each of the pixels; a first isolation section that is provided between adjacent pixels of the pixels and electrically and optically isolates the adjacent pixels from each other, a second isolation section that is provided between adjacent photoelectric converters in the pixel of the photoelectric converters and electrically isolates the adjacent photoelectric converters from each other; and an electrode layer provided on side of the first surface of the semiconductor substrate to extend over adjacent photoelectric converters of the photoelectric converters.