BSI Image Sensor Light Pipe Structure for Crosstalk Reduction
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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
1Reliability
If a device stack is used in FSI image sensor structure to block excitation light and reduce crosstalk, then light detection sensitivity is improved, but the active area of light detectors is blocked by device circuitry
Solution Approach 1:
The patent inverts the conventional FSI architecture by implementing BSI (back-side illumination) where the nanowell layer is disposed on the back side of the image sensor structure rather than the front side. This inversion allows the device stack to be positioned between the light detectors and the substrate, eliminating the blocking of light detector active areas while maintaining crosstalk reduction capabilities through alternative structural means.
Solution Approach 2:
The patent introduces a microlens array as an intermediary component between the nanowell layer and the light detectors. The microlens array focuses and directs emitted light from the nanowells onto the light detectors, improving light collection efficiency and enabling effective light detection without requiring the device stack to be positioned in front of the light detectors.
2Object-affected harmful factors
If device circuitry is positioned between nanowell layer and light detectors in FSI structure, then excitation light blocking is improved, but crosstalk reduction capability is lost in BSI structure
Solution Approach 1:
The patent introduces a microlens array as an intermediary component between the nanowell layer and the light detectors. The microlens array focuses and directs emitted light from the nanowells onto the light detectors, improving light collection efficiency and enabling effective light detection without requiring the device stack to be positioned in front of the light detectors.
Solution Approach 2:
The patent implements localized light focusing through the microlens array, where each microlens corresponds to a specific nanowell or group of nanowells. This local quality approach allows precise control of light paths, ensuring that emitted light is directed only to the intended light detectors while preventing crosstalk to adjacent detectors, even in the BSI configuration without traditional device stack positioning.
3Productivity
If light detector size and pitch are reduced to increase density, then device integration is improved, but the portion of active area blocked by device stack increases
Solution Approach 1:
The patent inverts the conventional FSI architecture by implementing BSI (back-side illumination) where the nanowell layer is disposed on the back side of the image sensor structure rather than the front side. This inversion allows the device stack to be positioned between the light detectors and the substrate, eliminating the blocking of light detector active areas while maintaining crosstalk reduction capabilities through alternative structural means.
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 sensor structures by blocking excitation light and directing emissive light to associated detectors, even in the absence of a device stack, while maintaining manufacturability and cost-effectiveness.
Implementation Method 1
light pipe cavities having aspect ratios and sidewall angles that are sized to sufficiently block excitation light
Implementation Method 2
light pipe cavities having aspect ratios and sidewall angles that are sized to efficiently collect and focus the emissive light emitting from the nanowells onto the light detectors
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.