Low frequency noise characteristics of resistor and Si MOSFET type gas sensors fabricated on the same Si wafer with In2O3 sensing layer
Abstract By analyzing the Low Frequency Noise (LFN) characteristics of the resistor type and the Si metal oxide semiconductor Field Effect Transistor (FET) type gas sensors fabricated on the same wafer, the intrinsic device noise and the additional noise generated from the gas reaction are systemically examined. Sensing material, n type Indium Oxide (In2O3) film, is deposited using the radio frequency magnetron sputtering method. Unlike the FET type gas sensor, the LFN characteristics of the resistor type gas sensor are affected by the deposition condition of the sensing material. It is shown that the FET type sensor has at least 10 times less LFN power than the resistor type gas sensor despite its smaller size. Gas to Air Noise Ratio (GANR) is introduced as a new figure of merit to evaluate and compare the LFN characteristics during the gas reaction in both resistor and FET type gas sensors with the sensing layer prepared by different process conditions. The GANRs of the resistor type sensors range from ~2 to 4, which demonstrates that the reaction between the gas molecules and the sensing material generates a fluctuation that exceeds the intrinsic noise of devices. However, the FET type gas sensors have a constant value of GANR ~1) regardless of the operation region, showing that the FET type gas sensors have better performance in terms of noise.