Image Sensor Grid Structure for Crosstalk Reduction
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Solution Overview
Problem
The challenge in image sensors is to maintain superior performance with shrinking pixel sizes, where light rays tend to interfere between adjacent color filter units, leading to reduced quantum efficiency and increased cross talk, compromising the overall performance.
Innovation Solution
The design of a grid structure with a first partition wall, a second partition wall having an inclined side surface, and a third partition wall, where the top width of the second partition wall is smaller than its bottom width, effectively concentrating light rays within each color filter unit and reducing cross talk by forming a funnel shape, thereby enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pixel size is reduced to meet industrial demand, then pixel density increases, but light ray interference between adjacent color filter units increases
Solution Approach 1:
The grid structure is divided into multiple partition walls (first, second, and third partition walls) that segment the space between adjacent color filter units. This segmentation creates physical barriers that prevent light ray interference while maintaining high pixel density, directly resolving the contradiction between increased pixel quantity and reduced light interference.
Solution Approach 2:
The partition walls have varying widths at different heights (narrower at the top, wider at the bottom), creating local quality variations in the grid structure. This local quality design allows the grid to provide stronger light blocking at critical interfaces while maintaining overall compactness, enabling high pixel density without compromising light isolation performance.
2Quantity of substance
If pixel size is reduced, then more pixels can be packed, but quantum efficiency decreases due to light ray interference
Solution Approach 1:
The multi-partition wall grid structure segments the optical path between adjacent pixels, preventing stray light from reaching neighboring photodetectors. This segmentation maintains high quantum efficiency by ensuring that detected light originates from the intended color filter unit, even as pixel density increases.
Solution Approach 2:
The grid structure converts the potentially harmful effect of light ray interference into a beneficial light-guiding effect. The partition walls are designed to refract and guide light rays toward the correct photodetector, transforming what would be interfering light into useful signal light, thereby maintaining quantum efficiency at high pixel densities.
3Quantity of substance
If pixel size is reduced, then pixel density increases, but cross talk between adjacent pixels increases
Solution Approach 1:
The grid structure with multiple partition walls creates complete segmentation between adjacent pixel regions. This segmentation physically isolates the optical paths, preventing signal leakage and cross talk between pixels, thereby maintaining information integrity even at high pixel densities.
Solution Approach 2:
The varying width design of partition walls (narrower at top, wider at bottom) creates local quality optimization for cross talk suppression. The wider base provides stronger isolation at the pixel interface, while the narrower top maintains compactness, effectively blocking cross talk without increasing overall pixel size.
4Ease of manufacture
If conventional grid structure is used, then manufacturing is simple, but light ray concentration within color filter units is insufficient
Solution Approach 1:
The partition walls feature local quality variations with different widths at different heights. This design concentrates light rays more effectively within each color filter unit by creating refraction patterns that guide light toward the center, while still being manufacturable using standard semiconductor fabrication processes.
Solution Approach 2:
The grid structure parameters (partition wall widths at different heights) are optimized to achieve superior light concentration. By carefully controlling these geometric parameters, the design achieves enhanced optical performance without requiring complex manufacturing processes, maintaining ease of fabrication while improving light ray concentration precision.
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 innovative grid structure enhances quantum efficiency and minimizes cross talk, leading to improved performance of image sensors by effectively guiding light rays to the sensing units and maintaining sufficient dimensions for color filter units.
Implementation Method 1
Each color filter unit is compartmentalized by a grid structure, which has a lower refractive index than that of the color filter units. Since light rays tend to be directed toward mediums with higher refractive index, the grid structure can repel potential light rays from interfering adjacent color filter units.
Implementation Method 2
The design of a grid structure with a first partition wall, a second partition wall having an inclined side surface, and a third partition wall, where the top width of the second partition wall is smaller than its bottom width, effectively concentrating light rays within each color filter unit and reducing cross talk by forming a funnel shape
Data Source
AI summary
An image sensor includes: a substrate; color filter units disposed on the substrate; and a grid structure disposed on the substrate and surrounding each of the color filter units. The grid structure includes: a first partition wall, disposed on the substrate, located between the color filter units; and a second partition wall, disposed directly on the first partition wall, located between the color filter units. A top width of the second partition wall is smaller than a bottom width of the second partition wall.