Variation of nitrogen incorporation and bonding configuration of carbon nitride films studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopic ellipsometry

摘要

A detailed study of the bonding structure and chemical composition of carbon nitride (CN_x) thin films prepared on c-Si substrates by RF reactive magnetron sputtering is presented. The nitrogen content in 19 X 10~(-3) and 4 X 10~(-3) Ar/N_2 mixtures was varied between 0 and 100% while the bias voltage (V_b) between +10 and -200 V. The films' elemental composition and chemical bonding were determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopic ellipsometry (FTIRSE). The N/C ratio decreased substantially for films grown with high negative V_b. The N1s spectral region was fitted with multiple peaks corresponding to various carbon-nitrogen bonding configurations sp~3, sp~2 and sp~1) and oxygen-bonded N. At films grown with V_b = + 10 V, the N atoms distribution among the possible bonding structures with C was unaffected by the P_(N_2) changes. These flms exhibit a mixed sp~1/sp~2/sp~3 character with an enhanced contribution of sp~2 C=N and sp~1 -C=N and -N=C bonds, as evidenced by FTIRSE. A substantial increase of the sp~3 C-N bond contribution in films grown with -40 <= V_b <= -200 V was evidenced by both XPS and FTIRSE.