Solid-State Image Sensor Pixel Segmentation With Surface Isolation
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Solution Overview
Problem
In solid state imaging devices, increasing pixel size to enhance sensitivity leads to longer transfer lengths, resulting in deteriorated transfer efficiency, and methods to shorten transfer lengths, such as dividing pixels and forming element isolation units, reduce photodiode opening areas and sensitivity.
Innovation Solution
A solid state imaging device and manufacturing method that includes a substrate with a photoelectric conversion unit, an accumulation unit, a first element isolation unit at the boundary of the photoelectric conversion unit, and a second element isolation unit at the boundary of the accumulation unit, where the element isolation units are formed only on the surface side to maintain photodiode opening area and prevent sensitivity decrease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is increased to enhance sensitivity, then sensitivity is improved, but transfer length becomes long and transfer efficiency deteriorates
Solution Approach 1:
The pixel is divided into multiple divided pixels, and a transfer transistor is arranged with respect to each divided pixel. This segmentation shortens the transfer length from the photodiode to the floating diffusion, improving transfer efficiency while maintaining the overall pixel size for high sensitivity
2Productivity
If element isolation unit is formed to isolate divided pixels, then transfer efficiency is improved, but opening area of photodiode is reduced and sensitivity decreases
Solution Approach 1:
The element isolation unit is formed selectively only in specific regions: at boundaries of photoelectric conversion units and at boundaries of accumulation units of divided units, but not throughout the entire pixel structure. This localized isolation prevents charge leakage while preserving maximum photodiode opening area for high sensitivity
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 approach prevents transfer deterioration while maintaining sensitivity by optimizing the placement of element isolation units, increasing the saturation signal amount, and improving the dynamic range.
Implementation Method 1
a photoelectric conversion unit that generates a charge according to a light amount of incident light
Data Source
AI summary
A solid state imaging device includes a substrate, in which the substrate includes a photoelectric conversion unit that generates a charge according to a light amount of incident light by a pixel unit, an accumulation unit that divides the charge of the pixel unit which is generated in the photoelectric conversion unit and accumulates the charge, a first element isolation unit that is formed at a boundary of the photoelectric conversion unit of the pixel unit, and a second element isolation unit that is formed at a boundary of the accumulation unit of a divided unit of the pixel.