BSI CMOS Image Sensor Microstructures for Higher Quantum Efficiency
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Solution Overview
Problem
Existing Back Side Illuminated (BSI) CMOS image sensors suffer from reduced quantum efficiency due to high light reflection and low light absorption caused by the planar surface of the semiconductor layer, which affects the image quality.
Innovation Solution
The semiconductor layer between the color filter layer and the device layer is modified with microstructures on its surface to refract and absorb light more effectively, reducing reflection and increasing absorption, thereby enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar surface is used for the semiconductor layer, then the manufacturing process is simple, but light reflection is high and light absorption is low
Solution Approach 1:
The patent applies curvature by forming microstructures (such as microlenses or curved surface features) on the semiconductor layer surface. These curved structures refract incoming light at multiple angles, increasing the optical path length and probability of absorption, thereby reducing reflection and improving quantum efficiency while maintaining manufacturing feasibility through standard photolithography and etching processes.
2Reliability
If microstructures are added to the semiconductor layer surface, then light absorption is improved, but device complexity increases
Solution Approach 1:
The patent segments the semiconductor layer surface into multiple discrete microstructures (such as an array of microlenses or localized curved regions) rather than creating a completely complex three-dimensional structure. This segmentation allows each microstructure to independently contribute to light absorption while keeping the overall device architecture relatively simple and compatible with existing CMOS manufacturing processes.
3Reliability
If microstructures are added to the semiconductor layer surface, then light absorption is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent employs self-service by utilizing the natural refraction and focusing properties of the microstructures themselves to improve light absorption. The microstructures are designed to automatically refract and concentrate light onto the photodiode active regions without requiring additional active control mechanisms or complex alignment systems, thereby improving quantum efficiency while maintaining ease of manufacture through passive optical design.
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 implementation of microstructures on the semiconductor layer significantly enhances light absorption and reduces reflection, leading to improved quantum efficiency and image quality in BSI CMOS image sensors.
Implementation Method 1
The semiconductor layer between the color filter layer and the device layer is modified with microstructures on its surface to refract and absorb light more effectively
Data Source
AI summary
A semiconductor device includes a plurality of photodiodes, a semiconductor structure, a dielectric layer, a color filter layer, and a micro-lens. The semiconductor structure overlaps the photodiodes. The semiconductor structure includes a plurality of microstructures on a backside of the semiconductor structure. The dielectric layer is over the microstructures of the semiconductor structure. A thickness of the dielectric layer is less than a vertical distance from one of the photodiodes to one of the microstructures. The color filter layer is over the dielectric layer. The micro-lens is over the color filter layer.