Chem-FET Ion Detection via Single-Gate Threshold Modulation
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Solution Overview
Problem
Current semiconductor devices for detecting chemical characteristics, such as ion-sensitive field-effect transistors (ISFETs), face challenges in accurately measuring ion concentrations and require complex manufacturing processes and dual gates, which increase costs and parasitic capacitance, limiting detection sensitivity and design flexibility.
Innovation Solution
A semiconductor device configuration that includes a Chem-FET with a threshold changing based on chemical states, applying a time-varying signal like a ramp wave to the source, drain, or back gate of the FET, allowing for threshold change reading as a signal, eliminating the need for dual gates and reducing parasitic capacitance, while enabling two-dimensional array arrangement and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual gates are used in ISFET configuration, then chemical detection capability is improved, but parasitic capacitance increases and detection sensitivity deteriorates
Solution Approach 1:
The invention extracts and eliminates one of the dual gates from the traditional ISFET configuration, retaining only the necessary gate structure for chemical detection. This removes the source of parasitic capacitance while preserving the core chemical sensing functionality through the remaining gate and threshold voltage modulation mechanism.
Solution Approach 2:
The invention changes the electrical parameters by applying time-varying signals (ramp waves) to the gate instead of static voltages. This dynamic parameter approach enables chemical detection through threshold shifting caused by ion concentration changes, achieving detection capability without requiring the second gate that would introduce parasitic capacitance.
2Measurement precision
If dual gates are used in ISFET configuration, then chemical detection capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention removes one gate structure from the dual-gate ISFET configuration, simplifying the device architecture. The remaining single gate structure maintains chemical detection functionality through threshold voltage modulation by ions in the sample, eliminating the need for complex dual-gate fabrication processes.
Solution Approach 2:
The single gate in the invention serves multiple functions: it acts as the control gate for the FET operation and simultaneously serves as the ion-sensitive interface for chemical detection. This multi-functionality eliminates the need for separate dual-gate structures, reducing device complexity while maintaining detection capability.
3Measurement precision
If conventional ISFET configuration is used, then chemical detection is enabled, but pixel size and device area are large
Solution Approach 1:
The invention segments the FET structure into compact regions with the ion-sensitive gate interface optimized for small area. By eliminating the second gate and associated structures, the active pixel area is reduced while maintaining the essential chemical detection function through the streamlined single-gate configuration.
Solution Approach 2:
The use of time-varying ramp wave signals enables the detection function to be achieved with smaller device dimensions. The dynamic signal approach allows for compact pixel design compared to static dual-gate configurations, as the threshold modulation effect can be observed with reduced gate areas.
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 measurement accuracy, reduces manufacturing costs, improves detection sensitivity, and increases design freedom by eliminating the need for dual gates and parasitic capacitance, allowing for precise ion concentration measurement and miniaturization of pixels.
Implementation Method 1
FET having a threshold changing according to a chemical state in a gate portion
Data Source
AI summary
According to one embodiment, a semiconductor device includes FET having a threshold changing according to a chemical state in a gate portion, a time-varying signal application section configured to apply a time-varying signal to at least one of a source, a drain and a back gate of the FET, and a signal reading section configured to read a change in the threshold of the FET resulting from the application of the time-varying signal as a signal.