CMOS Image Sensor Surface Structure for Broadband Antireflection
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Solution Overview
Problem
Traditional solid-state imaging devices with antireflective coatings optimized for green wavelengths suffer from inadequate antireflective effects for blue and red wavelengths, leading to degraded image quality due to reflection components in ultraviolet and infrared wavelengths, which affects sensitivity and spatial resolution.
Innovation Solution
The implementation of a solid-state imaging device with distinct concave-convex structures on the light-receiving surfaces of photoelectric conversion regions for blue, green, and red light, accompanied by specific anti-reflective layers and color filters, optimizing the structure and thickness for each wavelength range to minimize reflection and enhance sensitivity and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single antireflective coating optimized for green wavelengths is applied, then green light reflection is reduced, but blue and red wavelength reflection is insufficient
Solution Approach 1:
The patent segments the antireflective coating into multiple layers with different optical properties. The first antireflective layer has a first refractive index and the second antireflective layer has a second refractive index different from the first, allowing each layer to be optimized for different wavelength ranges. This segmentation enables broadband antireflection across UV, visible, and infrared wavelengths.
Solution Approach 2:
The patent uses composite material structure with two different antireflective layers having different refractive indices. This composite approach combines materials with complementary optical characteristics to achieve superior broadband performance that a single material cannot provide, reducing reflection across the entire wavelength spectrum.
2Reliability
If a minute concave-convex structure is applied to the silicon layer border, then overall reflection is reduced, but diffracted light enters neighboring pixels causing degraded spatial resolution
Solution Approach 1:
The patent applies local quality by providing the concave-convex structure only in specific regions (first and second regions) rather than uniformly across the entire light-receiving surface. The third region maintains a planar structure, allowing localized reflection reduction without introducing diffraction that would affect neighboring pixels, thus preserving spatial resolution.
Solution Approach 2:
The light-receiving surface is segmented into multiple regions with different structures. The first and second regions have concave-convex structures for reflection reduction, while the third region has a planar structure to avoid diffraction. This spatial segmentation allows the system to achieve both reflection reduction and maintained spatial resolution.
3Reliability
If the antireflective coating is optimized for green wavelengths, then green sensitivity is maximized, but ultraviolet and infrared reflection components degrade image quality
Solution Approach 1:
The patent changes the optical parameters by using two antireflective layers with different refractive indices and different thicknesses. The first layer has thickness optimized for UV wavelengths while the second layer has thickness optimized for visible and infrared wavelengths. This parameter optimization across multiple layers ensures minimal reflection across the entire spectrum while maintaining green sensitivity.
Solution Approach 2:
The dual-layer antireflective coating system provides universal performance across multiple wavelength bands (UV, visible, and infrared). Each layer contributes to different wavelength ranges, creating a multi-functional system that simultaneously addresses reflection issues in all bands while preserving green light sensitivity for high-quality imaging.
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 sensitivity across a wide wavelength band and enhances spatial resolution by effectively reducing reflection and diffracted light, particularly for blue and red wavelengths, while maintaining green sensitivity.
Implementation Method 1
an antireflective coat is applied between a silicon board and an upper layer, and the antireflective coat is optimized to reduce reflection of green
Implementation Method 2
CMOS image sensors that use crystalline silicon to absorb light have high sensitivity to visible wavelengths to infrared wavelengths
Implementation Method 3
as the color arrangement of RGB sensors, two pixels of 2×2 unit pixel arrangement are green, and the remaining pixels are red and blue
Data Source
AI summary
An imaging device includes a first photoelectric conversion region (170) receiving light within a first range of wavelengths, a second photoelectric conversion region (170) receiving light within a second range of wavelengths, and a third photoelectric conversion region (170) receiving light within a third range of wavelengths. At least a portion of a light-receiving surface of the first photoelectric conversion region has a first concave-convex structure (113), and a light-receiving surface of the second photoelectric conversion region has a different structure (111) than the first concave-convex structure.