ISFET Sensor Gate Resistance for pH Sensitivity
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Solution Overview
Problem
Existing pH sensors, such as ISFETs, face limitations in sensitivity and size scalability, which hinders their ability to detect pH changes effectively without increasing sensor size.
Innovation Solution
Incorporating a resistance region in the gate structure of semiconductor sensors to enhance the effective length of the channel region, thereby increasing sensitivity and reducing saturation drain current, while maintaining a constant current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the dimensions of the sensor are scaled up to improve sensitivity, then the sensitivity increases, but the sensor size increases
Solution Approach 1:
The patent changes the electrical parameters of the sensor by introducing a resistance region in the gate structure, which modifies the effective channel length and electrical characteristics without changing the physical dimensions of the sensor. This allows sensitivity improvement through parameter modification rather than geometric scaling.
Solution Approach 2:
The patent introduces a resistance region specifically in the gate structure area, creating a localized modification that affects the overall sensor performance. This localized change in the gate region's electrical properties enhances sensitivity without requiring the entire sensor to be scaled up.
2Loss of energy
If the channel length is increased to reduce saturation drain current, then the saturation drain current decreases, but the sensor area increases
Solution Approach 1:
The patent modifies the electrical parameters by introducing a resistance region that effectively increases the channel length electrically while maintaining the same physical dimensions. This parameter change reduces saturation drain current without requiring additional sensor area.
Solution Approach 2:
The resistance region acts as an intermediary element in the gate structure that mediates between the physical channel length and the effective electrical channel length. This intermediary allows the sensor to achieve the electrical characteristics of a longer channel without the physical space requirements.
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 the sensitivity of pH detection without increasing sensor size and reduces manufacturing costs, achieving a higher sensitivity gain and improved pH change measurement.
Implementation Method 1
Prior art sensors for detecting pH changes in a solution include ion-sensitive field-effect transistors (ISFETs) which may include an open-gate structure having a sensitivity up to the Nernst limit (60 mV/pH) or a floating-gate structure. In some ISFETs, the pH changes in the solution are monitored by a sensing member (including, for example, silicon oxide (SiO2), silicon nitride (Si3N4) or aluminium oxide (Al2O3)) and are converted to electrical signals.
Implementation Method 2
an open-gate structure having a sensitivity up to the Nernst limit (60 mV/pH)
Implementation Method 3
The resistance region may be configured to provide a resistance to a second current flow through the second channel region.
Data Source
AI summary
A sensor device includes a substrate, first and second source regions, first and second drain regions, first and second channel regions, and first and second gate structures disposed over the first and second channel regions respectively. The source regions and drain regions are at least partially disposed within the substrate. The second gate structure includes first and second gate elements, and a resistance region configured to provide a resistance to a second current flow through the second channel region. In use, the first gate structure may receive a solution, and a change in pH in the solution changes a first current flow through the first channel region. In turn, the second current flow through the second channel region changes to compensate for the change in the first current flow to maintain a constant current flow through the sensor device.