High Refractive Index Micro-Lenses for Image Sensor Sensitivity
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Solution Overview
Problem
Small-sized image sensor pixels have lower sensitivity and are prone to cross-talk due to their size being comparable to the wavelength of light, leading to reduced performance in capturing high-resolution images.
Innovation Solution
The use of micro-lenses with a refractive index greater than 1.8 to 2.5 and color filter fences with a refractive index less than 1.3 is implemented to enhance light gathering and reduce cross-talk, respectively, by forming micro-lenses from materials like metal-added resin, silicon nitride, and titanium oxide, and using porous silica or air layers for color filter fences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to achieve high-resolution images, then image resolution is improved, but sensitivity deteriorates
Solution Approach 1:
The patent changes the refractive index parameter of the micro-lens material from conventional values (1.4-1.7) to high refractive index values (1.8-2.5). This parameter change enables better light focusing capability in smaller pixels, thereby improving sensitivity while maintaining the small pixel size required for high resolution
Solution Approach 2:
The patent employs composite material structures including metal-added resin, silicon nitride, and other high refractive index materials for micro-lenses. These composite materials achieve the required high refractive index while maintaining manufacturability and optical performance in small-sized pixels
2Measurement precision
If pixel size is reduced to achieve high-resolution images, then image resolution is improved, but cross-talk between pixels increases
Solution Approach 1:
The patent applies different refractive index characteristics to different regions: high refractive index (1.8-2.5) micro-lenses for light gathering in pixel centers, and low refractive index (less than 1.3) color filter fences for cross-talk suppression between adjacent pixels. This local differentiation of optical properties simultaneously achieves high resolution and reduced cross-talk
Solution Approach 2:
The color filter fence acts as an intermediary structure between adjacent pixels. By using low refractive index material (less than 1.3) for the color filter fence, the patent creates an optical barrier that prevents light from one pixel from interfering with adjacent pixels, thereby reducing cross-talk while maintaining high resolution
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 light-receiving efficiency of small-sized pixels while minimizing cross-talk between pixels, resulting in better image quality and reduced diffraction issues.
Implementation Method 1
the micro-lens has a refractive index equal to or greater than a threshold which is greater than a refractive index of the color filter
Implementation Method 2
Each of the plurality of pixels includes a photoelectric conversion module configured to convert incident light into electric signals
Data Source
AI summary
Provided are an image sensor with micro-lenses having a high refractive index and an image processing system including the same. The image sensor includes: a semiconductor substrate in which a photoelectric conversion device is formed; at least one color filter formed on the semiconductor substrate; at least one color filter fence formed on the semiconductor substrate and between two neighboring color filters among the at least one color filter; and at least one micro-lens formed on the color filter, respectively. The micro-lens has a first refractive index equal to or greater than a first threshold. The filter fence has a second refractive index less than or equal to a second threshold. The second threshold is less than the first threshold.