Effects of Sensor Platform Scaling on Signal-to-Noise Ratio in the Resistor- and Horizontal Floating-Gate FET-Type Gas Sensors

We investigate the effects of sensor platform scaling on signal-to-noise-ratio (SNR) in the resistor- and field-effect-transistor (FET)-type gas sensors with horizontal floating gate (FG). Indium–gallium–zinc oxide (IGZO) is used as a sensing material and deposited by the RF sputtering method. The low-frequency noise (LFN) characteristics of the resistor- and FET-type gas sensors are determined by the sensing material and FET transducer, respectively. In both resistor- and FET-type gas sensors, the SNR decreases with the scaling of the sensing area. However, the reason for a decrease in the SNR differs depending on the sensor platform. The decrease in SNR in a resistor-type gas sensor is due to an increase in intrinsic device noise and gas-to-air-noise ratio (GANR), whereas a decrease in SNR in an FET-type gas sensor is due to a decrease in response. The results provide important design guidelines in designing and fabricating the resistor- and FET-type gas sensors.