Extended Gate Sensor pH Sensing Surface Area
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Solution Overview
Problem
Conventional pH sensors with floating gate structures have limited sensing surface area due to layout restrictions, leading to decreased pH sensitivity in applications like DNA sequencing and biochemical reactions.
Innovation Solution
The development of an extended gate field effect transistor (FET) sensor with a conductive metal gate that forms the pH sensing surface, increasing the sensing area by using the entire surface of the well as the pH sensing surface, eliminating the need for a floating gate and dielectric metal oxide sensing surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a floating gate FET sensor with dielectric metal oxide sensing surface is used, then the sensor can detect pH changes, but the sensing surface area is limited by layout area restrictions
Solution Approach 1:
The gate extension extends the sensing structure from a two-dimensional planar configuration to a three-dimensional configuration by forming conductive material that covers the well surfaces (bottom and side walls). This vertical extension into the third dimension significantly increases the sensing surface area without increasing the layout footprint, thereby improving pH sensitivity while maintaining compact device dimensions.
Solution Approach 2:
The gate extension is nested within the well structure, with conductive material forming the gate extension that is positioned inside and around the well. The gate extension utilizes the existing well volume and surfaces, effectively nesting the sensing function within the geometric constraints of the device architecture to maximize sensing area within available space.
2Measurement precision
If a floating gate design is used with dielectric metal oxide sensing layer, then pH sensing is achieved, but alignment issues and structural complexity increase
Solution Approach 1:
The invention extracts and eliminates the floating gate structure and dielectric metal oxide sensing layer from the device architecture. Instead of using a complex floating gate configuration requiring precise alignment, the patent employs a simplified metal gate extension that directly forms the pH sensing surface, removing unnecessary structural elements while maintaining pH detection functionality.
Solution Approach 2:
The gate extension serves multiple functions simultaneously: it acts as the gate electrode for transistor control, forms the pH sensing surface through its conductive material, and eliminates the need for separate dielectric sensing layers. This multi-functionality reduces structural complexity by combining what were previously separate components into a single integrated structure.
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 enhances pH sensitivity by increasing the sensing surface area and simplifies the sensor structure, reducing alignment issues and improving the detection of pH changes in solutions.
Implementation Method 1
The gate extension includes a conductive material exposed on at least one surface of the well and forming a gate conductor of the sensing device
Data Source
AI summary
A sensing device includes a substrate having a source region and a drain region formed therein. A gate structure is formed over the substrate and includes a gate dielectric and a gate conductor. The gate conductor is formed on the gate dielectric and disposed between the source region and the drain region. A dielectric layer is formed over the substrate and has a depth configured to form a well over the gate conductor. A gate extension is formed in contact with or as part of the gate conductor and including a conductive material covering one or more surfaces of the well.