CMOS Image Sensor Cross-Talk Reduction via Dopant Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Complementary metal oxide semiconductor image sensors experience cross-talk between adjacent pixel regions, reducing precision and efficiency due to interference from adjacent components in both front-side and back-side illumination configurations.
Innovation Solution
The implementation of isolation regions with specific dopant concentrations and implantation profiles between pixel regions in a back-side illuminated CMOS image sensor to mitigate cross-talk, involving photolithographic masking and ion implantation processes to form isolation regions and photosensitive diodes, and thinning the substrate to reduce light travel distance and dopant diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If isolation regions are added between pixel regions to reduce cross-talk, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the semiconductor substrate into distinct pixel regions separated by isolation regions. Each pixel region is independently isolated using dopant implantation, creating discrete functional units that prevent cross-talk while maintaining overall sensor functionality.
Solution Approach 2:
The patent applies different dopant concentrations locally - higher dopant concentrations are implanted in isolation regions compared to pixel regions. This local variation in dopant concentration creates electrical isolation where needed while preserving photosensitivity in the pixel regions.
2Productivity
If substrate is thinned to reduce light travel distance, then productivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs dopant implantation and isolation region formation before substrate thinning. This preliminary action establishes the electrical isolation structure while the substrate is still thick enough to tolerate manufacturing variations, then the substrate is thinned to improve light sensitivity and overall sensor efficiency.
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 approach enhances the precision and efficiency of the image sensor by reducing cross-talk between adjacent pixel regions, improving the overall performance and manufacturing complexity of the image sensor.
Implementation Method 1
the isolation region having a first concentration of first dopants adjacent to the second side of the substrate... the first concentration of first dopants being higher than the second concentration of second dopants
Implementation Method 2
involving photolithographic masking and ion implantation processes to form isolation regions and photosensitive diodes
Implementation Method 3
thinning the substrate to reduce light travel distance
Implementation Method 4
Complementary metal oxide semiconductor image sensors generally utilize a series of photodiodes formed within an array of pixel regions of a semiconductor substrate in order to sense when light has impacted the photodiode
Data Source
AI summary
A system and method for reducing cross-talk between photosensitive diodes is provided. In an embodiment an isolation region comprising a first concentration of dopants is located between the photosensitive diodes. The photosensitive diodes have a second concentration of dopants that is less than the first concentration of dopants, which helps to prevent diffusion from the photosensitive diodes to form a potential path for undesired cross-talk between the photosensitive diodes.