Characterization of boron carbon nitride film for humidity sensor

Boron carbon nitride films are synthesized in a horizontal quartz reactor by plasma-assisted chemical vapor deposition. Boron trichloride (BCl3), nitrogen (N-2) and methane (CH4) are used as source gases. Plasma of N-2 and CH4 is produced by supplying RF power to the turn coil. BCl3 is transported near the substrate by H-2 gas. The substrate temperature is kept at 730 degrees C. The BCN film with B, C, N and O composition ratios of 43%, 30%, 24% and 3% is characterized. Thermal desorption spectroscopy (TDS) measurement is carried out for the BCN film treated with D2O. Desorption of D2O from the BCN film occurs at 230 degrees C, 420 degrees C and 730 degrees C. Desorption of D-2 also occurs at 750 degrees C. The impedance of the as-deposited and water-treated BCN films is investigated by ac measurement. The impedance of the as-deposited BCN film depends on the -0.9 power law of the frequency. On the other hand, the impedance of the water-treated BCN film decreases in the frequency range lower than 10(4) Hz. This is because another electrical conduction other than the quantum-mechanical tunneling hopping conduction becomes dominant due to water incorporation into the BCN film. (c) 2007 Elsevier B.V All rights reserved.