Image Sensor Multilayer Refractive Index Structure
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Solution Overview
Problem
Current image sensors face limitations in quantum efficiency due to light loss and absorption issues, which affect their electrical sensitivity to light.
Innovation Solution
A multilayer structure with specific refractive index and extinction coefficient properties is implemented, including a surface repairing layer, a first light transmitting layer with a higher refractive index than the substrate, and a second light transmitting layer with a lower refractive index, to minimize light loss and absorption, thereby enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional single-layer structure is used, then the device complexity is low, but light loss and absorption increase, reducing quantum efficiency
Solution Approach 1:
The patent divides the light transmitting structure into multiple layers with different refractive indices (first light transmitting layer with higher refractive index, second light transmitting layer with lower refractive index). This segmentation allows each layer to perform specific optical functions, reducing overall light loss and absorption while maintaining manageable complexity through modular design
Solution Approach 2:
The patent employs composite material structure combining different dielectric materials with specific refractive indices and extinction coefficients. The first light transmitting layer uses materials with higher refractive index (e.g., TiO2, SiO2) while the second layer uses materials with lower refractive index (e.g., Si3N4, SiOx), creating a composite structure that optimizes light transmission and minimizes absorption losses
2Loss of energy
If the refractive index of the light transmitting layer is matched to the substrate, then light transmission is maximized, but light absorption increases, reducing quantum efficiency
Solution Approach 1:
The patent applies different refractive index characteristics to different layers: the first light transmitting layer has higher refractive index than the substrate to reduce reflection and enhance light entry, while the second light transmitting layer has lower refractive index to minimize absorption and maximize transmission. This local differentiation of optical properties optimizes overall light transmission while minimizing absorption
Solution Approach 2:
The patent systematically varies key optical parameters (refractive index and extinction coefficient) across different layers. By selecting materials with specific parameter combinations - first layer with higher refractive index and appropriate extinction coefficient, second layer with lower refractive index and low extinction coefficient - the patent achieves optimal balance between light transmission and absorption reduction
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 described multilayer structure improves the quantum efficiency of image sensors by reducing light loss and absorption, leading to enhanced electrical sensitivity to light across various wavelengths.
Implementation Method 1
a first light transmitting layer (321) formed over the back side (211) of the thinned substrate (110). The first light transmitting layer (321) has a refractive index that is from 60% to 90% of a refractive index of the substrate (110)
Implementation Method 2
a second light transmitting layer (322) formed over and in direct contact with the first light transmitting layer (321). The second light transmitting layer (322) has a refractive index that is lower than the refractive index of the first light transmitting layer (321) and is from 40% to 70% of the refractive index of the substrate (110)
Data Source
AI summary
An image sensor includes a substrate having opposite first and second sides, a multilayer structure on the first side of the substrate, and a photo-sensitive element on the second side of the substrate. The photo-sensitive element is configured to receive light that is incident upon the first side and transmitted through the multilayer structure and the substrate. The multilayer structure includes first and second light transmitting layers. The first light transmitting layer is sandwiched between the substrate and the second light transmitting layer. The first light transmitting layer has a refractive index that is from 60% to 90% of a refractive index of the substrate. The second light transmitting layer has a refractive index that is lower than the refractive index of the first light transmitting layer and is from 40% to 70% of the refractive index of the substrate.