Impedance characteristics of carbon nitride films for humidity sensors

Carbon nitride films were deposited on silicon substrate for humidity sensors with meshed electrodes by reactive RF magnetron sputtering system with DC bias. The surface of carbon nitride films had a good uniformity with the grain size of about 30 nm. The EDS analysis revealed that the chemical formula of the carbon nitride film could be expressed between C7N4 and C3N and these results also revealed those quite agree with XPS results. The films have very high resistivity, the characteristic of which can be expected to use for insulating films on the Si fabrication. The impedance of the sample deposited on the Si-wafer decreased from 118 kΩ to 4 kΩ in the relative humidity range of 5-95%. Hysteresis of the film deposited on the Si-wafer was about 4.2% of full scale output.