A low-power integrated humidity CMOS sensor by printing-on-chip technology

Area of Science:

• Materials Science and Engineering
• Electrical Engineering
• Sensor Technology

Background:

• Integrated humidity sensors are crucial for various applications, but often face challenges with miniaturization, power consumption, and manufacturing complexity.
• Existing humidity sensing technologies may not be compatible with standard semiconductor fabrication processes, limiting monolithic integration.

Purpose of the Study:

• To develop a low-power, wide-dynamic-range integrated humidity sensing chip.
• To demonstrate a novel printing-on-chip fabrication method for humidity sensors.
• To achieve a heterogeneous three-dimensional sensor system-on-chip architecture.

Main Methods:

• Utilized inkjet printing to deposit a printable polymer sensing material, poly(3,4-ethylene-dioxythiophene)/polystyrene sulfonate, onto a 0.35 μm CMOS integrated circuit (IC).
• Integrated an on-chip pulse-width-modulation (PWM) interface circuit for signal readout.
• Experimentally tested the humidity sensing performance of the fabricated printing-on-chip sensor system.

Main Results:

• Achieved a humidity sensor sensitivity of 0.98% to atmospheric humidity.
• The readout circuit demonstrated a maximum dynamic range of 9.8 MΩ, tunable via input signal frequency.
• The integrated sensor exhibited low power consumption of only 154 μW.

Conclusions:

• The developed printing-on-chip humidity sensor successfully integrates a polymer sensing material with CMOS circuitry.
• This approach offers a practical and efficient solution for creating ultra-small, low-power integrated sensors.
• The technology is well-suited for applications requiring miniaturized sensing systems.