Image Sensor Active Region Geometry for Small-Pixel Image Quality
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Solution Overview
Problem
As image sensors become more densely integrated, the size of pixels decreases, leading to challenges in maintaining high-definition image quality while ensuring reliable operational performance and compactness.
Innovation Solution
The design incorporates a substrate with a plurality of pixels, each featuring a separate photoelectric conversion region, a pixel isolation structure, and transfer gates that extend vertically through an interlayer insulating layer, with specific angles between the transfer gates and pixel isolation structures optimized to enhance the overlap area, thereby improving image quality and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of pixels is decreased to increase integration density, then the compactness and integration density are improved, but the image quality and operational performance deteriorate
Solution Approach 1:
The patent introduces a vertical gate structure that extends in the depth direction (third dimension) rather than only in the horizontal plane. The isolation layer defines active regions with vertical extension, and transfer gates pass through interlayer insulating layers vertically, utilizing the Z-axis dimension to increase functional area without expanding pixel footprint, thereby maintaining high integration density while preserving image quality
Solution Approach 2:
The patent implements nested structures where transfer gates are positioned within and pass through interlayer insulating layers that are themselves within the pixel structure. The isolation layer with vertical active regions is nested within the substrate, creating multiple hierarchical levels of structure that maximize space utilization and functional density within each pixel
2Volume of moving object
If the size of pixels is decreased for miniaturization, then the compactness is improved, but the reliability of operational performance deteriorates
Solution Approach 1:
By extending the isolation layer vertically to define active regions with depth, and by implementing transfer gates that pass through multiple interlayer insulating layers in the vertical direction, the patent increases the functional volume and overlap area within each miniaturized pixel, thereby maintaining reliable operational performance despite reduced pixel size
Solution Approach 2:
The patent changes the geometric parameters of the pixel structure by introducing vertical extension of the isolation layer and transfer gates, transforming the structure from primarily two-dimensional to three-dimensional, which increases the effective functional area and overlap without increasing the horizontal pixel footprint
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 the reliability and image quality of image sensors while enabling increased miniaturization, improving the operational performance and compactness of the image sensor.
Implementation Method 1
Each pixel includes a photodiode region, which receives and converts incident light into an electrical signal
Data Source
AI summary
An image sensor includes a substrate including a plurality of pixels and a photoelectric conversion region in an inside thereof, a pixel isolation structure isolating the plurality of pixels, and an isolation layer defining a plurality of active regions in the substrate, wherein the plurality of active regions include a center part having a plurality of branching sections extending from a center toward the plurality of pixels, the center being adjacent to each of the plurality of pixels, and an extension part in the plurality of pixels and extending in a horizontal direction from the center part. In a plan view, a first angle between a side wall of the extension part and the pixel isolation structure extending in a first direction exceeds about 45 degrees, or a second angle between two adjacent branching sections among the plurality of branching sections is less than about 90 degrees.