Hydrogenated amorphous carbon nitride films on Si(100) deposited by direct current saddle-field plasma-enhanced chemical vapor deposition

Hydrogenated amorphous carbon nitride [a-C:H(N)] films were deposited on p-type Si(100) at room temperature with a substrate bias voltage of 200 V by direct current saddle-field plasma-enhanced chemical vapor deposition using methane and nitrogen as source gases. The structural and compositional changes of the a-C:H(N) films induced by the differential ratio of N2 to CH4(nN2/nCH4) were investigated using Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy. Initially, as nitrogen is added to the pure methane, the deposition rate decreases quite rapidly then less so as nN2/nCH4 rises above 0.5. The deposition rate continues to gradually decrease with the increase of the nN2/nCH4. The ratio of N to C of the films saturated at 0.25 at the maximum of nN2/nCH4. The number of N–H and C≡H bonds in the films increased with nN2/nCH4 but the number of C–H bonds decreased. The optical band gap energy of the films, as determined by the Tauc relation was lowered from 2.53 to 2.3 eV as the nN2/n...