Metal-Free Color Filter Grid for High-QE Image Sensors
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Solution Overview
Problem
Current image sensors face challenges in achieving high quantum efficiency (QE) and are prone to stain defects due to the use of metal layers in grid patterns, which absorb light and reduce image quality.
Innovation Solution
The implementation of a metal-free grid pattern with a low refractive index, combined with an anti-reflective layer containing a TiO2 layer, which acts as a charge path to prevent stain defects and enhance QE by eliminating light absorption from metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal layer is used in the grid pattern, then electrical conductivity is improved, but light absorption increases and quantum efficiency deteriorates
Solution Approach 1:
The patent removes the metal layer from the grid pattern structure, extracting the harmful light-absorbing component while retaining the grid's functional role through alternative materials (silicon oxide or silicon nitride) that do not absorb light in the visible spectrum
Solution Approach 2:
The patent changes the material parameter of the grid pattern from metal (high light absorption) to dielectric materials like silicon oxide or silicon nitride (low light absorption), fundamentally altering the optical properties while maintaining structural integrity
2Strength
If a metal layer is used in the grid pattern, then structural strength is improved, but stain defects increase due to light reflection and absorption
Solution Approach 1:
The patent converts the harmful effect of metal layers (light reflection and absorption causing stain defects) into a benefit by using dielectric materials that eliminate these optical interference effects, thereby preventing stain defects while maintaining grid functionality
Solution Approach 2:
The patent uses thin film dielectric layers (silicon oxide or silicon nitride) that are deposited as thin films and can be selectively removed or patterned, providing a replaceable and manufacturable solution without the complications of metal layers
3Device complexity
If the anti-reflective layer is made thinner to reduce complexity, then manufacturing simplicity is improved, but light reflection increases and quantum efficiency deteriorates
Solution Approach 1:
The patent employs a composite anti-reflective layer structure combining multiple materials (silicon oxide and silicon nitride) with different refractive indices, creating a multi-layer configuration that optimizes anti-reflection performance while managing overall layer thickness
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 solution improves quantum efficiency by preventing light absorption and reducing stain defects, resulting in enhanced image sensor performance without the need for metal layers in the grid pattern.
Implementation Method 1
an anti-reflective layer with a TiO2 layer to enhance light absorption and minimize reflection
Implementation Method 2
a grid pattern made of a low-refractive-index material, such as tetraethyl orthosilicate (TEOS) or porous low-k material
Data Source
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AI summary
Provided is an image sensor including a first substrate including a pixel area and a peripheral area adjacent to the pixel area, the pixel area including a plurality of pixels in a 2-dimensional array, a first wiring layer on a lower surface of the first substrate, an anti-reflective layer having a first refractive index, the anti-reflective layer being on an upper surface of the first substrate, and color filters on the anti-reflective layer corresponding to the pixel area and spaced apart from each other by a metal-free grid pattern.