Pixel Isolation Air Grid for Low-Loss Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In image sensing devices, especially those with small pixels, optical loss occurs due to light being scattered and absorbed in the isolation regions, which contain polysilicon, leading to reduced image quality.
Innovation Solution
The implementation of an air grid in the inner isolation region of the image sensing device, which is free of light absorbing materials, helps to prevent optical loss by allowing incident light to be scattered and absorbed within the isolation regions without absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation regions containing polysilicon are used to separate pixels, then pixel isolation and electrical performance are improved, but optical loss increases due to light absorption
Solution Approach 1:
The patent extracts the light-absorbing polysilicon material from the isolation region and replaces it with a reflective metal layer. This removal of the harmful light-absorbing component eliminates optical loss while maintaining the electrical isolation function through the metal layer and underlying structures.
Solution Approach 2:
The patent changes the material parameter of the isolation region from light-absorbing polysilicon to light-reflecting metal. This parameter change transforms the optical property from absorptive to reflective, thereby reducing optical loss while maintaining the isolation function.
2Productivity
If pixel size is reduced to increase pixel density, then device integration is improved, but optical loss increases due to larger isolation region proportion
Solution Approach 1:
By removing the light-absorbing polysilicon from the isolation region and replacing it with a reflective metal layer, the patent eliminates the source of optical loss. This allows for reduced pixel sizes and higher density without the isolation regions consuming incident light, as the metal layer reflects light back toward the photodiode.
Solution Approach 2:
The patent converts the previously harmful light absorption by polysilicon into a beneficial reflection by using metal layers. The isolation regions that would have caused optical loss now serve to reflect light back to the photodiode, turning a harmful effect into a useful one that enhances light utilization in high-density pixel arrays.
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 effectively reduces optical loss in image sensing devices, enhancing image quality by ensuring that incident light is efficiently converted into electrical signals without being absorbed by the isolation regions.
Implementation Method 1
light being scattered and absorbed in the isolation regions
Data Source
AI summary
Disclosed is an image sensing device including a pixel array including a unit pixel including sub-pixels. A first isolation region is disposed in an edge region of a sub-pixel, a second isolation region extends from the first isolation region to a central portion of the sub-pixel. The second isolation region includes: a first inner isolation region protruding in a first direction from one region of the first isolation region to the central portion of the sub-pixel, and a second inner isolation region formed on a same straight line as the first inner isolation region and protruding in a second direction from another region of the first isolation region to the central portion of the sub-pixel. A first grid is formed in an upper region located above a region between the first inner isolation region and the second inner isolation region, and the first grid includes an air layer.