Nanowell Image Sensor Passivation Structure for Crosstalk Blocking
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Solution Overview
Problem
In image sensor structures, crosstalk between nanowells becomes a significant noise contributor as pitch between rows decreases, leading to increased noise levels and reduced analyte capacity in each well, necessitating a reduction in crosstalk transmitted through the passivation stack.
Innovation Solution
Incorporating crosstalk blocking metal structures, such as pillars or parallel metal plates, within the passivation stack to reduce crosstalk before it enters the light guides, thereby minimizing noise and enhancing signal clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pitch between rows of nanowells is reduced to increase the number of nanowells, then productivity is improved, but crosstalk increases leading to reduced measurement precision
Solution Approach 1:
A crosstalk blocking metal structure is introduced as an intermediary element within the passivation stack. This metal structure acts as a mediator that selectively blocks crosstalk photons while allowing analytes to pass through and reach their associated light guides, thereby resolving the contradiction between increased density and reduced crosstalk
Solution Approach 2:
The passivation stack is transformed into a composite structure by incorporating a metal layer within the dielectric passivation layers. This composite material approach allows the structure to simultaneously provide electrical isolation, mechanical support, and optical filtering functions to reduce crosstalk
2Productivity
If nanowell size is reduced to accommodate tighter pitch, then productivity is improved, but the total number of analytes per well decreases leading to reduced signal intensity
Solution Approach 1:
The crosstalk blocking metal structure serves as an intermediary that filters out stray photons before they can contaminate neighboring light guides. This allows smaller nanowells to be used without compromising signal quality, as the metal structure compensates for the reduced signal intensity by blocking external noise
Solution Approach 2:
The metal structure is positioned locally within the passivation stack at specific locations between nanowells. This localized intervention provides targeted crosstalk reduction exactly where needed, allowing each nanowell to maintain optimal size for its analyte capacity while preventing interference from neighbors
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 crosstalk blocking metal structures effectively reduce crosstalk by at least 5-50%, significantly lowering noise levels and maintaining or improving the signal quality, especially in densely packed nanowell arrays.
Implementation Method 1
Crosstalk includes emissive light that is transmitted from a nanowell, through the passivation stack, and into a neighboring unassociated light guide... The crosstalk blocking metal structures significantly reduce crosstalk transmitted within the passivation layer and prior to entering top surfaces of light guides
Data Source
AI summary
An example image sensor structure includes an image layer. The image layer includes an array of light detectors disposed therein. A device stack is disposed over the image layer. An array of light guides is disposed in the device stack. Each light guide is associated with at least one light detector of the array of light detectors. A passivation stack is disposed over the device stack. The passivation stack includes a bottom surface in direct contact with a top surface of the light guides. An array of nanowells is disposed in a top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides. A crosstalk blocking metal structure is disposed in the passivation stack. The crosstalk blocking metal structure reduces crosstalk within the passivation stack.