Floating Gate Nanostructure Biosensor for Stable High-Surface Detection
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Solution Overview
Problem
Conventional semiconductor nanostructure biosensors face limitations in reproducibility and stability due to a small sensing surface area, low biomolecule combination probability, and sensitivity to environmental conditions, which hinders their commercialization.
Innovation Solution
A floating gate semiconductor nanostructure biosensor is developed, featuring an extended gate structure with a metal or polysilicon pattern that increases the sensing surface area, allowing for higher biomolecule interaction and improved stability by maintaining the nanostructure's inherent sensitivity while preventing direct exposure to sample solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the sensing surface area is increased by integrating multiple silicon nanostructures with high density, then the sensing area increases, but the processing time increases due to the need to pattern the nanostructure using electron beam lithography
Solution Approach 1:
The gate structure is segmented into a floating gate portion and an extending gate portion. The extending gate portion is further divided into multiple finger-like structures that can be independently formed, allowing the sensing surface area to be increased without requiring complex electron beam lithography patterning of the entire nanostructure array.
Solution Approach 2:
The gate structure extends in a lateral dimension beyond the nanostructure channel, creating an extended gate portion that protrudes toward the source and drain electrodes. This dimensional extension provides additional sensing surface area without increasing the channel length or requiring complex patterning of the nanostructure itself.
2Area of stationary object
If the number of nanostructures is increased to increase the sensing surface, then the sensing area increases, but the width of the effective channel increases and thus the sensitivity decreases
Solution Approach 1:
The extending gate is divided into multiple discrete finger structures spaced apart from each other. This segmentation maintains a narrow effective channel width between source and drain electrodes while providing a large total sensing surface area through the combined surface of all finger structures, thereby preserving sensitivity despite increased sensing area.
Solution Approach 2:
The sensing surface is extended laterally beyond the channel region rather than increasing the channel width. The extending gate portion projects into the space above the source-drain region, providing additional sensing area without affecting the critical channel dimensions that determine sensitivity.
3Area of stationary object
If a vertical nanostructure is used to enlarge the sensing surface, then the sensing surface area increases, but the structure is hard to be insulated when used inside liquid
Solution Approach 1:
An insulating layer is introduced as an intermediary between the extending gate structure and the liquid environment. This insulating layer, formed on the gate electrode and extending gate portion, provides electrical insulation when the device is used in liquid, preventing short circuits while maintaining the enlarged sensing surface area of the vertical gate structure.
4Ease of manufacture
If the probe molecule is directly coated and fixed on the nanostructure, then the sensing process is simplified, but the combination probability of the biomolecule is relatively low and the reproducibility is very low
Solution Approach 1:
The probe molecules are pre-coated and fixed on the extending gate portion before the final device assembly. This preliminary action allows the extending gate to serve as a pre-prepared sensing platform with optimized biomolecule combination probability, improving reproducibility while maintaining manufacturing simplicity through a sequential process rather than requiring post-assembly modification.
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 floating gate biosensor enhances sensitivity, reproducibility, and stability, enabling effective biomolecule detection with improved reaction time characteristics and reduced interference from sample solutions.
Implementation Method 1
when the fixed biological detection material is combined with the target material, electrical properties of the nanostructure is changed like field effect transistor (FET) effect, and thus a change of conductivity or a change of threshold voltage may be detected
Implementation Method 2
In the nanostructure, a surface area with respect to a volume is very large such that a reaction with an electrically charged bio molecule highly affects conduction characteristics of the entire nanostructure, and thus, the semiconductor nanostructure has high sensitivity
Data Source
AI summary
In a floating gate semiconductor nanostructure biosensor and a method for manufacturing the biosensor, the nanostructure biosensor includes a substrate, an insulating layer, a nanostructure, a source electrode and a drain electrode, a floating gate and a biological sensing material. The insulating layer is formed on the substrate. The nanostructure is protruded from the insulating layer. The source electrode and the drain electrode are formed on the insulating layer and dispose the nanostructure therebetween. The floating gate has a metal pattern or a polysilicon pattern, and extends with contacting the nanostructure. The biological sensing material has a first end combined with an immobile molecule on the floating gate, and a second end combined with a bio molecule.