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An acetone microsensor with a ring oscillator circuit fabricated using the commercial 0.18 μm CMOS process
Ming-Zhi Yang1, Ching-Liang Dai2, Po-Jen Shih3
1Department of Mechanical Engineering, National Chung Hsing University, Taichung 402, Taiwan. d099061005@mail.nchu.edu.tw.
This study presents a novel acetone microsensor fabricated using a commercial 0.18 μm complementary metal oxide semiconductor (CMOS) process. The sensor detects acetone vapor by measuring changes in capacitance, converting them into frequency output, showing a decrease from 128 to 100 MHz with increasing concentration.
Area of Science:
- Materials Science
- Electrical Engineering
- Chemical Sensing
Background:
- Acetone detection is crucial for medical diagnostics and environmental monitoring.
- Existing acetone sensors often face challenges in sensitivity, selectivity, or integration with electronic circuits.
- Development of miniaturized, low-power acetone microsensors is essential for portable sensing applications.
Purpose of the Study:
- To fabricate and characterize an acetone microsensor integrated with a ring oscillator circuit.
- To utilize alpha-iron oxide (α-Fe2O3) as the sensitive material for acetone detection.
- To demonstrate the sensor's performance using a commercial 0.18 μm complementary metal oxide semiconductor (CMOS) process.
Main Methods:
- Fabrication of an acetone microsensor with α-Fe2O3 sensitive material, interdigitated electrodes, and a polysilicon heater using CMOS technology.
- Post-processing steps including sacrificial oxide removal and α-Fe2O3 coating.
- Integration of the microsensor with a ring oscillator circuit to convert capacitance changes to frequency output.
Main Results:
- The acetone microsensor exhibited a change in capacitance upon adsorption of acetone vapor.
- The integrated ring oscillator circuit successfully converted capacitance variations into oscillation frequency.
- The sensor's output frequency decreased from 128 MHz to 100 MHz as acetone concentration increased from 1 ppm to 70 ppm.
Conclusions:
- A functional acetone microsensor with a ring oscillator circuit was successfully fabricated using a standard CMOS process.
- The α-Fe2O3 based sensor demonstrated a concentration-dependent frequency response to acetone vapor.
- This integrated microsensor shows potential for sensitive and efficient acetone detection in various applications.
