Nanowell Image Sensor Layout With Buried Bond Pads
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Solution Overview
Problem
Existing biosensor systems face limitations in increasing data throughput due to the restricted size of nanowells and the need for surface chemistry compatibility with electronic components, as bond pads are exposed to fluid flow and chemical reactions, leading to potential damage and contamination.
Innovation Solution
The placement of bond pads under a passivation stack allows the flow channel to be enlarged over the bond pads, increasing the number of nanowells without exposing them to fluid flow, thus protecting the bond pads and enabling a larger nanowell array within a fixed footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bond pads are exposed on the surface for electrical connectivity, then electrical connection is enabled, but the flow channel area is restricted and bond pads are vulnerable to damage from fluid flow and chemical reactions
Solution Approach 1:
The bond pads are nested within the passivation stack structure, specifically positioned in the first substrate layer beneath the flow channel. This nesting allows the flow channel to be enlarged over the bond pads without exposing them, as the passivation stack acts as a protective container that accommodates both the bond pads and the flow channel above them.
Solution Approach 2:
The passivation stack serves as an intermediary layer between the bond pads and the flow channel. It provides electrical connectivity through the bond pads while simultaneously protecting them from direct exposure to fluid flow and chemical reactions in the flow channel, thus mediating between the electrical and fluidic functions.
2Productivity
If the number of nanowells is increased to enhance data throughput, then data throughput is improved, but the size of individual nanowells must be reduced making surface chemistry compatibility more critical
Solution Approach 1:
The passivation stack provides different local properties: the top layer contains nanowells with specific surface chemistry for analyte reactions, while lower layers provide structural support and electrical connectivity. This local differentiation allows nanowells to be miniaturized for high density while maintaining surface chemistry functionality, as each nanowell region is optimized independently.
3Reliability
If bond pads are protected by passivation stack, then bond pads are protected from damage, but additional manufacturing steps are required
Solution Approach 1:
The bond pads are positioned and protected within the passivation stack during the manufacturing process itself, before the device is assembled and put into service. The passivation stack is formed with integrated bond pad cavities and electrical pathways, so the protection is built-in during fabrication rather than added as a separate post-processing step, reducing overall manufacturing complexity.
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 configuration enhances data throughput by increasing the number of nanowells and protecting the bond pads from damage, allowing for more efficient chemical reactions and data analysis without compromising the sensor system's electrical connectivity.
Implementation Method 1
the bond pads are protected by the passivation stack, the flow channel area of the sensor system is no longer restricted by the bond pads
Implementation Method 2
analytes (such as clusters of DNA segments, nucleic-acid molecular chains, or the like) that are disposed in a nanowell array of an image sensor structure may be tagged with an identifiable label (such as a fluorescently labeled molecule) that is delivered to the analytes via fluid flow through the flow channel
Implementation Method 3
One or more excitation lights can then be directed onto the labeled analytes within the nanowells. The analytes may then emit photons of an emissive light
Implementation Method 4
The light guides direct the emissive light photons to light detectors disposed within the image sensor structure and associated (e.g., located directly below) with the light guides
Implementation Method 5
The light detectors detect the emissive light photons. Device circuitry within the image sensor structure then processes and transmits data signals using those detected photons
Data Source
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AI summary
A system includes an image sensor structure and a flow cell. The image sensor structure includes an image layer disposed over a base substrate. A device stack is disposed over the image layer. A bond pad is disposed in the device stack. A passivation stack is disposed over the device stack and the bond pad. An array of nanowells is disposed in a top layer of the passivation stack. A through-silicon via (TSV) is in electrical contact with the bond pad. The TSV extends through the base substrate. A redistribution layer (RDL) is disposed on a bottom surface of the base substrate. The RDL is in electrical contact with the TSV. The flow cell is disposed upon the top layer of the passivation stack to form a flow channel therebetween. The flow channel is disposed over the array of nanowells and the bond pad.