Properties of carbon nitride films produced by an inductively coupled plasma chemical vapor deposition

Carbon nitride films were deposited on (100) silicon substrates by inductively coupled plasma (ICP)–CVD using a gas mixture of Ar, C2H2, and N2. During deposition, an rf bias was applied to the substrate to increase the ion bombardment energy. The results of the microhardness test and Raman spectroscopy revealed that the films showed abrupt changes in their hardness and bonding characteristics when the rf bias voltage was >−40 V. The ion energy at −40 V was estimated to be 50 eV from the IEA measurement. Such changes were attributed to the structural and compositional modifications of the growing film as a result of the bombarding ions. The bombardment of high-energy ions removed hydrogen atoms from the adsorbed CxHy radicals on the growing surface. At >50 eV, the X-ray photoelectron spectroscopy (XPS) data show the chemical bonding changes from sp2CN to sp3C–C and sp3C–N bondings. The abrupt increase in hardness was caused by the increased number of sp3 bonds in the carbon nitride coating.