Image Sensor Divider for Crosstalk Reduction
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Solution Overview
Problem
Back side illuminated (BSI) CMOS image sensors face interference issues due to increased pixel density, which current grid systems cannot fully eliminate, affecting quantum efficiency and well capacity.
Innovation Solution
Incorporating a divider between sensor pixels with a refractive index lower than the substrate, positioned between the optical and sensing regions, to reflect filtered incident lights and prevent crosstalk, while maintaining optimal pixel density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel density is increased to improve resolution, then more light-sensing pixels can be packed in the substrate, but interference and crosstalk between adjacent pixels increases
Solution Approach 1:
The patent divides the substrate into isolated pixel regions by introducing divider structures between adjacent photodiodes. These dividers segment the continuous substrate into discrete sensing zones, preventing light from spilling into adjacent pixels and eliminating crosstalk while maintaining high pixel density.
Solution Approach 2:
The patent introduces an intermediary material (divider) with different refractive index properties than the substrate. This intermediary structure acts as a barrier that redirects light paths, preventing direct interference between adjacent pixels while allowing each pixel to function independently at high density.
2Object-affected harmful factors
If grids are added to reduce crosstalk between pixels, then interference between adjacent pixels decreases, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality modification by creating dividers only at specific locations between adjacent pixels where crosstalk occurs, rather than implementing a comprehensive grid structure across the entire substrate. This localized approach reduces complexity while effectively addressing the crosstalk problem.
Solution Approach 2:
The patent uses composite material structures combining the substrate material with divider materials having different refractive indices. This composite approach provides effective light isolation without requiring complex grid patterns, simplifying the overall device structure while maintaining performance.
3Reliability
If a divider with lower refractive index than substrate is introduced to reflect light and prevent crosstalk, then quantum efficiency and well capacity improve, but device complexity increases
Solution Approach 1:
The patent optimizes the refractive index parameter of the divider material to be lower than the substrate, creating optimal light reflection conditions. By carefully selecting and controlling this physical parameter, the patent achieves improved quantum efficiency and well capacity with a relatively simple divider structure rather than complex multi-layer designs.
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
The divider effectively reduces unwanted electrical signal generation from adjacent pixels, enhancing quantum efficiency and well capacity by retaining filtered lights within their designated sensing regions.
Implementation Method 1
The divider is disposed on an interface between a sensor pixel and an adjacent sensor pixel to reduce and/or eliminate interference from the adjacent sensor pixel. The divider acts to separate at least a portion of the sensing region of adjacent sensor pixels. With the divider, filtered incident lights in a sensing region of a sensor pixel are restricted to travel in the sensing region without interfering a sensing region of an adjacent sensor pixel.
Implementation Method 2
a divider between sensor pixels with a refractive index lower than the substrate, positioned between the optical and sensing regions, to reflect filtered incident lights
Data Source
AI summary
An image sensor comprises an image sensing substrate that in turns includes an image sensing device, a first sensor pixel, a second sensor pixel, and a divider. The divider is between the first sensor pixel and the second sensor pixel.