BSI Image Sensor Light Guide and Nanowell Layout for Low Crosstalk
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Solution Overview
Problem
Back-side illuminated (BSI) image sensor structures face challenges with crosstalk and inefficient light collection due to the absence of a device stack, which blocks excitation light and fails to reduce crosstalk between nanowells and unassociated light detectors.
Innovation Solution
The implementation of an image sensor structure with light pipe cavities having specific aspect ratios and sidewall angles, along with optical filter materials, to block excitation light and efficiently collect emissive light without the need for a device stack, thereby reducing crosstalk and enhancing light detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a device stack is used in FSI image sensor structure to block excitation light and reduce crosstalk, then excitation light blocking and crosstalk reduction are improved, but the active area of light detectors is blocked reducing sensitivity
Solution Approach 1:
The patent inverts the conventional FSI architecture by implementing a BSI structure where the nanowell layer is positioned on the back side of the substrate and the device stack is removed from between the nanowell layer and light detectors. This inversion eliminates the blocking of light detector active area while maintaining excitation light blocking and crosstalk reduction through alternative means (substrate thickness optimization and optical coupling layers).
Solution Approach 2:
The patent extracts the device stack from the optical path between the nanowell layer and light detectors. By removing this blocking element entirely and relying on the substrate itself and optical coupling layers for light management, the patent eliminates the trade-off between blocking capability and detector sensitivity.
2Measurement precision
If the device stack is removed in BSI image sensor structure to avoid blocking light detector active area, then light detector sensitivity is improved, but crosstalk reduction capability is lost
Solution Approach 1:
The patent introduces optical coupling layers as intermediary elements between the nanowell layer and light detectors in the BSI structure. These layers serve as mediators that provide excitation light blocking and crosstalk reduction functionality without requiring the device stack to be positioned in the optical path, thus maintaining both sensitivity and harmful factor reduction.
Solution Approach 2:
The patent changes the substrate thickness parameter to optimize the BSI structure. By carefully controlling the substrate thickness, the patent achieves sufficient excitation light blocking and crosstalk reduction without needing the device stack, thereby resolving the contradiction between removing the stack for sensitivity and maintaining blocking capability.
3Device complexity
If the device stack is removed in BSI image sensor structure, then manufacturing complexity is reduced, but light collection efficiency deteriorates
Solution Approach 1:
The patent introduces optical coupling layers as intermediary elements that enhance light collection efficiency in the simplified BSI structure. These layers act as optical mediators that improve the coupling between the nanowell layer and light detectors, compensating for the removal of the device stack's light collection function while maintaining structural simplicity.
Solution Approach 2:
The patent optimizes substrate thickness and optical coupling layer parameters to maximize light collection efficiency in the BSI structure. By carefully tuning these parameters, the patent achieves efficient light collection without requiring the complex device stack configuration, thus resolving the contradiction between simplicity and 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 solution effectively reduces crosstalk and improves light collection efficiency in BSI image sensors by utilizing light pipe cavities with optimized dimensions and materials, ensuring reliable manufacturing and enhanced performance.
Implementation Method 1
light pipe cavities having aspect ratios and sidewall angles that are sized to sufficiently block excitation light and efficiently collect emissive light
Implementation Method 2
optical filter materials, to block excitation light and efficiently collect emissive light
Implementation Method 3
the analytes (such as clusters of DNA segments or the like) may be tagged with a fluorescent label and an excitation light may be directed onto the labeled analytes to cause them to fluoresce an emissive light
Data Source
AI summary
An image sensor structure including an image stack disposed over a device stack. The image stack includes a plurality of light detectors. A first optical filter stack is disposed over the image stack. The first optical filter stack includes a light guide layer. Light pipe cavities are disposed in the light guide layer. Each light pipe cavity is associated with a light detector. Each light pipe cavity has an aspect ratio that is greater than about 2.5 to about 1. A nanowell layer is disposed over the first optical filter stack. Nanowells are disposed in the nanowell layer. Each nanowell is associated with a light detector.