Fabrication, Characterization, and Modeling of an Aluminum Oxide-Gate Ion-Sensitive Field-Effect Transistor-Based pH...

Area of Science:

• Materials Science
• Chemical Engineering
• Electrical Engineering

Background:

• Ion-sensitive field-effect transistors (ISFETs) are widely used for pH sensing.
• Aluminum oxide (Al2O3) offers potential as a sensing material in ISFETs.
• Optimizing Al2O3-gate ISFET fabrication and characterization is crucial for improved performance.

Purpose of the Study:

• To fabricate and characterize an Al2O3-gate ISFET pH sensor.
• To develop an electrochemical model for the Al2O3-gate ISFET.
• To evaluate the sensor's sensitivity, drift, and hysteresis.

Main Methods:

• Fabrication using metal-oxide-semiconductor (MOS) processes and pulsed-DC magnetron sputtering for Al2O3 deposition.
• Material characterization via X-ray diffraction, SEM, EDS, and XPS.
• Packaging using thick-film technology and dam-and-fill encapsulation.
• Performance testing in various pH buffer solutions and SPICE macromodeling.

Main Results:

• Achieved a sensitivity of approximately 42.1 mV/pH.
• Obtained low drift rates (e.g., 0.136 μA/min at pH 4) and hysteresis (5.806 μA).
• Empirically derived SPICE macromodel from experimental data.

Conclusions:

• The developed Al2O3-gate ISFET pH sensor exhibits high sensitivity and excellent stability (low drift and hysteresis).
• The fabrication and characterization process provides a viable pathway for advanced pH sensing devices.
• The validated electrochemical model aids in predicting and optimizing ISFET sensor performance.