Image Sensor Double Air Grid Optical Crosstalk
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Solution Overview
Problem
Current image sensors face challenges in minimizing optical interference between pixels, which affects image quality due to the lack of effective isolation structures between color filters.
Innovation Solution
The implementation of a double air grid structure with inner and outer air grids, each composed of low refractive index layers and capped with oxide films, is introduced between adjacent color filters to minimize optical crosstalk by reflecting incident light back into the pixel, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If color filters are disposed adjacent to each other without isolation structures, then device complexity is reduced and manufacturing is simplified, but optical crosstalk between pixels increases and image quality deteriorates
Solution Approach 1:
The patent introduces an air grid structure as an intermediary element between adjacent color filters. This air grid, having a refractive index lower than both the color filter and surrounding materials, acts as an optical mediator that reflects stray light back into the pixel while maintaining physical separation. The air grid includes an inner air grid and an outer air grid with different refractive indices, creating a staged optical isolation system that effectively blocks crosstalk without requiring direct contact between color filters.
Solution Approach 2:
The patent utilizes refractive index parameter differences to solve the optical crosstalk problem. By designing the air grid with a refractive index (air, n≈1.0) lower than both the color filter material (n≈1.5-1.7) and the surrounding embedding material (n≈1.4-1.6), the structure creates optimal optical conditions for reflecting stray light. This parameter-based approach allows the air grid to function as an effective optical barrier without adding physical complexity to the manufacturing process.
2Object-affected harmful factors
If isolation structures are added between color filters to reduce optical crosstalk, then image quality improves, but device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent merges the air grid structure with the existing color filter array architecture. The inner air grid is positioned within the embedding material that already surrounds the color filters, while the outer air grid integrates with the microlens structure. This merging approach allows the isolation function to be added without creating entirely separate complex structures, as the air grids utilize and enhance existing structural elements.
Solution Approach 2:
The patent implements a nested air grid configuration where the inner air grid is positioned inside the outer air grid. This nested structure creates a multi-layered optical isolation system where the inner air grid handles primary crosstalk prevention and the outer air grid provides additional isolation and light guidance. The nested design maximizes optical isolation effectiveness while minimizing the overall space required, as the structures are concentric and share the same vertical profile.
3Object-affected harmful factors
If air grid structures are introduced between color filters, then optical crosstalk is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs preliminary patterning actions where the air grid structures are formed using the same photolithography and etching processes as the color filters themselves. The air grid patterns are defined during the color filter fabrication sequence, allowing precise alignment to be established beforehand. The inner and outer air grids are patterned using the same mask layers and alignment references, ensuring that their relative positions are predetermined and consistent across the array.
Solution Approach 2:
The air grid structure serves multiple functions simultaneously: it provides optical isolation, acts as a structural support framework, and defines the embedding material regions. The same air grid formation process creates all these features, eliminating the need for separate precision alignment steps. The air grid walls themselves serve as alignment references for subsequent color filter and microlens formation, making the structure self-aligning.
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 image quality by minimizing optical crosstalk and maintaining light receiving efficiency, allowing for improved photon detection and image resolution.
Implementation Method 1
a first grid structure including a first material having refractive index lower than a refractive index of the color filters and disposed between color filters adjacent to each other, and a second grid structure including a second material having refractive index lower than the refractive index of the color filters
Implementation Method 2
to minimize optical crosstalk by reflecting incident light back into the pixel
Data Source
AI summary
Image sensor devices including photo detectors located relative to one another to form an array, color filters located above the photo detectors, respectively, to filter incident light that are received by the photo detectors, respectively, a first grid structure including a first material having refractive index lower than a refractive index of the color filters and disposed between color filters adjacent to each other, and a second grid structure including a second material having refractive index lower than the refractive index of the color filters and disposed inside the first grid structure.