Floating Gate FET Biosensor Without a Reference Electrode
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Solution Overview
Problem
Conventional biosensors with field effect transistors (FETs) on silicon devices face challenges in fabricating reference electrodes, leading to increased costs and size, which is not suitable for wearable applications, especially when reference electrodes are stored in solutions.
Innovation Solution
A silicon biosensor device with a field effect transistor (FET) is designed without a reference electrode, incorporating a metal-insulator-metal (MIM) structure and a floating gate with an extension for sensing, and an additional layer covering the sensing surface, which reduces the footprint and complexity, enabling portable biosensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference electrode is included in the conventional biosensor design, then the sensing accuracy is improved, but the device size and complexity increase
Solution Approach 1:
The patent removes the reference electrode from the biosensor system entirely. Instead of including both working and reference electrodes, the invention uses only a working electrode with a floating gate that can sense analyte concentration changes without requiring a separate reference electrode, thus reducing device size while maintaining sensing capability
Solution Approach 2:
The floating gate structure serves multiple functions: it acts as both the sensing element and the reference potential stabilizer. The gate dielectric layer functions as both the insulator and the analyte interaction interface, eliminating the need for separate reference electrode components
2Measurement precision
If a reference electrode is included in the conventional biosensor design, then the sensing accuracy is improved, but the manufacturing cost increases
Solution Approach 1:
By extracting the reference electrode from the design, the patent reduces the number of fabrication steps, materials required, and assembly operations. The floating gate can be formed using standard semiconductor processing techniques, simplifying manufacturing and reducing costs
Solution Approach 2:
The invention changes the operational parameters of the FET device to enable sensing without a reference electrode. By operating the FET in a specific mode where the floating gate potential naturally stabilizes, the system achieves accurate sensing with fewer components, reducing manufacturing complexity and cost
3Weight of moving object
If the biosensor is designed for wearable applications, then the portability is improved, but the device size constraint becomes more stringent
Solution Approach 1:
Removing the reference electrode significantly reduces the device footprint, making the biosensor suitable for wearable applications where space and weight are critical constraints. The compact floating gate structure enables integration into small form factor devices
Solution Approach 2:
The floating gate is nested within the gate dielectric layer of the FET structure, creating a compact integrated design. The extension of the floating gate into the sensing region is efficiently positioned, maximizing sensing capability while minimizing overall device size for wearable integration
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 design reduces the cost and size of biosensors, making them suitable for wearable applications by eliminating the need for a reference electrode and enhancing sensing capabilities without increasing the footprint.
Implementation Method 1
Biosensors can be electrical devices that sense specific conditions based on the concentration, or presence, of analytes in a medium
Data Source
AI summary
Embodiments are disclosed for a field effect transistor (FET) device. The FET device includes a semiconductor channel. Additionally, the FET device includes a first gate dielectric in contact with the semiconductor channel. Further, the FET device includes a metal-insulator-metal (MIM) structure. The MIM structure includes a liner comprising a first metal, an insulator, and a second metal. The first metal is in contact with the first gate dielectric. Additionally, the insulator is in contact with the first metal and the second metal. Further, the FET device includes a floating gate. The floating gate includes the first metal and an extension. Additionally, the extension is disposed to one side of the MIM structure, and includes a surface for sensing a sample in contact with the surface.