Image Sensor Fence Pattern for Pixel Crosstalk Reduction
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Solution Overview
Problem
CMOS image sensors face challenges in achieving high image quality and additional functions due to their small size, leading to issues with light sensing and noise from increased integration, which affects the proper detection of incident light and introduces interference between elements.
Innovation Solution
The image sensor design includes a substrate with photodiodes, an element isolation film, an anti-reflection layer, color filters, and micro lenses, with a fence pattern composed of different materials to reduce crosstalk and enhance light efficiency by extending between color filters and the anti-reflection layer, preventing light from entering adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to achieve high resolution, then image resolution is improved, but light sensing capability deteriorates and noise increases due to increased integration density
Solution Approach 1:
The patent applies local quality by creating a fence pattern with different material compositions at different locations. The first layer uses a first material while the second layer uses a second material, allowing each region to optimize its properties for light blocking and crosstalk reduction while maintaining overall pixel functionality despite reduced pixel size
Solution Approach 2:
The fence pattern is constructed using composite materials with different optical properties. The first layer and second layer use different materials that work together to enhance light blocking effectiveness, enabling the structure to reduce crosstalk between adjacent pixels while maintaining the reduced pixel dimensions needed for high resolution
2Area of stationary object
If element integration is increased to reduce device size, then device compactness is improved, but interference between elements increases causing noise
Solution Approach 1:
The fence pattern structure extracts and isolates the harmful optical interference between adjacent pixels by introducing a dedicated light-blocking structure. This fence pattern is positioned between color filters and the anti-reflection layer to specifically address and remove the crosstalk issue that arises from increased integration density
Solution Approach 2:
The fence pattern acts as an intermediary element between adjacent photodiodes and color filters. By placing this light-blocking structure in the intermediate region, it mediates the optical interaction between neighboring pixels, preventing direct optical coupling and reducing interference while allowing the device to maintain compact dimensions
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 design improves image quality by reducing crosstalk between pixels, enhancing light efficiency, and maintaining high image resolution, even in small pixel sizes, by effectively managing light distribution and interference.
Implementation Method 1
a photoelectric conversion element such as a photodiode for each pixel. The photoelectric conversion element may generate an electrical signal that varies based on an amount of light incident thereto
Implementation Method 2
an anti-reflection layer disposed on the plurality of photodiodes and the element isolation film
Implementation Method 3
micro lenses disposed on the plurality of color filters
Implementation Method 4
a plurality of color filters disposed on the anti-reflection layer
Data Source
AI summary
An image sensor includes: a substrate; a plurality of photodiodes disposed in the substrate; an element isolation film disposed between the plurality of photodiodes; an anti-reflection layer disposed on the plurality of photodiodes and the element isolation film; a plurality of color filters disposed on the anti-reflection layer; a fence pattern disposed between the plurality of color filters and in the anti-reflection layer; and micro lenses disposed on the plurality of color filters, wherein the fence pattern includes a first layer and a second layer that is disposed on the first layer and that includes a material different from that of the first layer, the first layer is disposed in the anti-reflection layer, and the second layer includes a first part and a second part, wherein the first part is disposed in the plurality of color filters, and wherein the second part is disposed in the anti-reflection layer.