Image Sensor Pixel Isolation Structure for Cross-Talk Reduction
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Solution Overview
Problem
Highly integrated image sensors experience cross-talk between pixels due to reduced pixel size, leading to performance degradation.
Innovation Solution
An image sensor design incorporating a substrate with pixel isolation regions that include a deep device isolation layer and a channel stop region, where the deep device isolation layer contacts the first surface and the channel stop region contacts the second surface, along with a shallow device isolation layer and an air gap region, to effectively separate adjacent pixel regions and prevent cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is reduced to increase integration, then productivity increases, but cross-talk between pixels worsens
Solution Approach 1:
The pixel isolation region is divided into multiple segments: a first isolation layer extending from the first surface to a first depth, a second isolation layer extending from the first surface to a second depth (shallower than the first depth), and a channel stop region between them. This segmented approach creates multiple barriers to prevent cross-talk while maintaining high integration density.
Solution Approach 2:
Different regions of the pixel isolation structure have different properties: the first isolation layer provides deep isolation, the second isolation layer provides shallow isolation, and the channel stop region provides impurity-doped isolation. Each layer is optimized for its specific function, creating a composite isolation system that effectively blocks cross-talk.
2Object-generated harmful factors
If deep isolation layers are added to prevent cross-talk, then cross-talk reduction improves, but device complexity increases
Solution Approach 1:
The first isolation layer and second isolation layer are integrally formed as one body, reducing manufacturing steps and complexity. The channel stop region is doped into the substrate to directly form the isolation structure, combining multiple functions into unified structures that simplify the overall device fabrication.
3Object-generated harmful factors
If channel stop region is doped to improve isolation, then cross-talk prevention improves, but manufacturing precision requirements increase
Solution Approach 1:
The channel stop region is formed by doping the substrate before forming the isolation layers. This preliminary doping action establishes the isolation structure early in the fabrication process, providing a foundation for subsequent layer formation and reducing the precision requirements for later steps.
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 solution improves surface uniformity, reduces defects, and enhances the dark current characteristic, resulting in a high-definition image sensor with improved pixel isolation and reduced cross-talk.
Implementation Method 1
the channel stop region is an impurity-doped region
Implementation Method 2
Each pixel has a photodiode (PD) that converts incident light into an electrical signal
Data Source
AI summary
An image sensor includes a substrate having a first surface opposing a second surface and a plurality of pixel regions. A photoelectric converter is included in each of the pixel regions, and a gate electrode is formed on the photoelectric converter. Also, a pixel isolation region isolates adjacent pixel regions. The pixel isolation region includes a first isolation layer coupled to a channel stop region. The channel stop region may include an impurity-doped region.