Image Sensor Sub-Isolation Structure for Pixel Segmentation
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Solution Overview
Problem
Existing image sensor technologies face challenges in increasing resolution without degrading signal-noise ratio (SNR) and quantum efficiency (QE), particularly in back-side illuminated (BSI) image sensors, where reducing pixel size to enhance resolution leads to unfavorable decreases in received light and QE due to limitations in isolation structure size.
Innovation Solution
The implementation of a sub-isolation structure that divides each pixel into sub-pixels, allowing for a narrower width than the main isolation structure, which reduces optical and electrical cross-talk, thereby maintaining or improving SNR and QE while increasing resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to increase resolution, then resolution is improved, but quantum efficiency and signal-noise ratio deteriorate due to insufficient light reception area
Solution Approach 1:
The pixel is divided into multiple sub-pixels (e.g., four sub-pixels) through sub-isolation structures. This segmentation allows each sub-pixel to be isolated optically while collectively maintaining the light reception area of the original pixel, thereby preventing quantum efficiency degradation despite the reduced pixel size needed for higher resolution.
Solution Approach 2:
Different regions within the pixel are assigned different functions: sub-pixels are optimized for light detection while isolation structures are optimized for optical separation. The sub-isolation structures are strategically positioned to provide local optical isolation where needed while preserving the overall light collection capability of the pixel region.
2Measurement precision
If isolation structure width is reduced to increase pixel density, then resolution is improved, but optical and electrical cross-talk between adjacent pixels increases
Solution Approach 1:
The isolation structure is segmented into a hierarchical system with main isolation structures separating adjacent pixels and sub-isolation structures separating sub-pixels within a pixel. This multi-level segmentation provides comprehensive optical and electrical isolation, preventing cross-talk even when the overall pixel pitch is reduced for higher resolution.
Solution Approach 2:
The sub-isolation structures act as intermediary elements between sub-pixels, providing optical and electrical isolation. These intermediary structures prevent harmful cross-talk effects while allowing the pixel density to be increased for higher resolution imaging.
3Measurement precision
If pixel size is reduced to increase resolution, then resolution is improved, but signal-noise ratio deteriorates due to reduced light reception
Solution Approach 1:
By segmenting the pixel into sub-pixels with sub-isolation structures, the patent maintains the effective light reception area while improving resolution. The sub-pixels collectively capture the same amount of light as the original pixel, preserving the signal strength and signal-noise ratio even as the pixel pitch is reduced.
Solution Approach 2:
The patent introduces a vertical dimension to the isolation structure by implementing sub-isolation structures that extend into the substrate. This vertical isolation provides optical and electrical separation without reducing the horizontal light reception area, thereby maintaining signal-noise ratio while enabling higher resolution through reduced pixel pitch.
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 allows for increased image sensor resolution without degrading SNR and QE, as the sub-pixels detect light in the same color, minimizing optical cross-talk and enabling a narrower sub-isolation structure, thus enhancing overall image sensor performance.
Implementation Method 1
The CMOS image sensor generally utilizes light-sensitive CMOS circuitry to convert photons into electrons. The light-sensitive CMOS circuitry typically includes a photo-diode formed in a substrate. As the photo-diode is exposed to light, an electrical charge is induced in the photo-diode.
Data Source
AI summary
An image sensor device includes a substrate, a color filter layer, at least a pixel, a main isolation structure and a sub-isolation structure. The color filter layer is disposed over the substrate. The color filter layer includes a first color filter having a single one of primary colors. The pixel is disposed in the substrate and aligned with the first color filter. The main isolation structure surrounds the pixel in the substrate. The sub-isolation structure is disposed to divide the pixel into a plurality of sub-first pixels. The sub-pixels correspond to the first color filter having the single one of primary colors, and each of the sub-first pixels includes a radiation sensor.