Image Sensor Color Filters with Differential Refractive Indices
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Solution Overview
Problem
Existing image sensors face challenges in optimizing signal-to-noise ratio (SNR) and quantum efficiency (QE) due to interactions between color filter materials, which limits device performance.
Innovation Solution
The image-sensor structure incorporates color filter patterns with specific refractive indices, where the green filter pattern has a higher refractive index than the red and blue filter patterns, achieved by blending pigments and compounds such as sulfur-containing polymers or fluoroacrylic polymers, to enhance SNR and QE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional color filter materials are used with standard refractive indices, then the manufacturing process is simple, but the device performance such as SNR and QE cannot achieve optimization due to interactions between color filter materials
Solution Approach 1:
The patent changes the refractive index parameter of color filter materials by selecting specific polymers (acrylic, polycarbonate, polyimide) with different refractive indices. The green filter uses materials with higher refractive indices (1.50-1.60) while red and blue filters use materials with lower refractive indices (1.40-1.50), thereby optimizing device performance without significantly complicating the manufacturing process
Solution Approach 2:
The patent employs composite material strategies by combining different polymer types (acrylic resin, polycarbonate, polyimide) with specific refractive index characteristics to create color filter materials. These composite materials achieve both the desired optical properties and compatibility across different color filters, resolving the contradiction between performance optimization and material complexity
2Reliability
If color filter materials are selected to fit the expected target spectrum, then the color accuracy is improved, but the interaction between color filter materials still prevents optimization of SNR and QE
Solution Approach 1:
The patent applies local quality by assigning different refractive index characteristics to different color filter regions. The green filter is designed with higher refractive index materials (1.50-1.60) while red and blue filters use lower refractive index materials (1.40-1.50). This localized differentiation reduces harmful interactions between adjacent color filters and optimizes overall device performance
Solution Approach 2:
By changing the refractive index parameter of each color filter material locally, the patent minimizes the harmful interactions between color filters. The specific selection of polymers with different refractive indices creates optical isolation effects that prevent cross-talk between color channels, thereby improving SNR and QE
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 improves the sensitivity and performance of the image sensor by optimizing the refractive indices of the color filters, particularly increasing the sensitivity of the green filter, thereby enhancing the overall device performance.
Implementation Method 1
a red filter pattern having a first refractive index, a green filter pattern having a second refractive index and a blue filter pattern having a third refractive index... the second refractive index of the green filter pattern is higher than the first refractive index of the red filter pattern and the third refractive index of the blue filter pattern
Data Source
AI summary
An image-sensor structure is provided. The image-sensor structure includes a substrate, a plurality of photoelectric conversion units formed in the substrate, and a plurality of color filter patterns including a red filter pattern having a first refractive index, a green filter pattern having a second refractive index and a blue filter pattern having a third refractive index formed above the substrate and the photoelectric conversion units, wherein at least one color filter pattern contains a component having a specific refractive index such that the second refractive index of the green filter pattern is higher than the first refractive index of the red filter pattern and the third refractive index of the blue filter pattern.