Image Sensor Floating Node Layout for Crosstalk and Dark Current
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Solution Overview
Problem
As semiconductor devices scale down, they face increased complexity and defects such as electron crosstalk, dark current, and white pixels due to shrinking pixel sizes and spacing, which existing manufacturing processes inadequately address.
Innovation Solution
The implementation of an image sensor structure with a blocking layer that constrains the size of the floating node, expanding the distance between light sensing regions and the source/drain structure, thereby mitigating crosstalk, dark current, and white pixel defects, and improving quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel sizes and spacing are shrunk to increase device density, then productivity and production efficiency are improved, but electron crosstalk, dark current, and white pixel defects increase
Solution Approach 1:
A blocking layer is introduced as an intermediary structure between adjacent pixels and floating nodes. This blocking layer physically obstructs electron migration paths that cause crosstalk and reduces electron leakage that causes dark current and white pixels, thereby maintaining light-sensing reliability while allowing continued pixel scaling for improved productivity
Solution Approach 2:
The harmful electron migration and leakage paths are extracted and blocked by the blocking layer structure. By removing the electron flow pathways that cause crosstalk and dark current through the blocking layer, the patent eliminates the harmful effects while preserving the scaled-down pixel architecture needed for high productivity
2Productivity
If pixel sizes are shrunk to increase device density, then productivity is improved, but dark current and white pixel defects increase
Solution Approach 1:
The blocking layer serves as an intermediary barrier that intercepts and blocks electron leakage paths before electrons can reach unintended regions. This prevents dark current generation while allowing continued scaling of pixel size for improved productivity
Solution Approach 2:
The blocking layer is positioned in advance to prevent electron leakage before it can cause dark current or white pixel defects. By establishing this protective barrier during manufacturing, the patent proactively eliminates harmful effects while maintaining scaled-down pixel dimensions for high productivity
3Productivity
If pixel sizes are shrunk to increase device density, then productivity is improved, but electron crosstalk increases
Solution Approach 1:
The blocking layer acts as an intermediary structure that physically separates electron flow paths between adjacent pixels. This mediation prevents electrons from one pixel from migrating to neighboring pixels, eliminating crosstalk while allowing continued scaling for improved productivity
4Reliability
If floating node size is reduced to expand distance from light sensing regions, then electron crosstalk and dark current are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The blocking layer is formed in advance during the manufacturing process to pre-defin e the maximum size and position of the floating node. This preliminary action establishes precise boundaries before subsequent processing steps, making it easier to control floating node dimensions and position without requiring extremely high manufacturing precision in later steps
Solution Approach 2:
The blocking layer is formed on the sidewalls of gate spacers, utilizing the vertical dimension to constrain the horizontal size of the floating node. This dimensional approach allows precise control of floating node dimensions through the height and thickness of the blocking layer rather than requiring precise lateral patterning
Data Source
AI summary
A method of manufacturing an image sensor structure includes forming an isolation structure in a substrate to divide the substrate into a first region and a second region, forming a first light sensing region in the first region and a second light sensing region in the second region, forming a first gate structure over the first light sensing region and a second gate structure over the second light sensing region, forming gate spacers on sidewalls of the first and second gate structures, and depositing a blocking layer on sidewalls of the gate spacers. The blocking layer has an opening positioned between the first and second gate structures. A source/drain structure is formed directly under the opening in the blocking layer. The method also includes forming an interlayer dielectric layer over the first and second gate structures and the blocking layer.