Deposition of carbon nitride films using an electron cyclotron wave resonance plasma source

摘要

Hydrogenated amorphous carbon nitride (a-C:N:H) has been synthesised using a high plasma density electron cyclotron wave resonance (ECWR) technique using N{sub}2 and C{sub}2H{sub}2 as source gases, at different ratios and a fixed ion energy (80eV). The composition, structure and bonding state of the films were investigated and related to their optical and electrical properties. The nitrogen content in the film rises rapidly until the N{sub}2/C{sub}2H{sub}2 gas ratio reaches 2 and then increases more gradually, while the deposition rate decreases steeply, placing an upper limit for the nitrogen incorporation at 30 at%. For nitrogen contents above 20 at%, the band gap and sp3-bonded carbon fraction decrease from 1.7 to 1.1 eV and ～65 to 40%, respectively. The transition is due to the formation of polymeric >C=N, -C≡N and >NH groups, not an increase in CH bonds. Films with higher nitrogen content are less dense than the original hydrogenated tetrahedral amorphous carbon (ta-C:H) film but, because they have a relatively high band gap (1.1 eV). high resistivity (l0{sup}9 Ω cm) and moderate sp{sup}3-bonded carbon fraction (40%), they should be classed as polymeric in nature.