Effect of grain size and pores on the dielectric constant of nanocrystalline diamond films
Wang ZL., Li JJ., Sun ZH., Li YL., Luo Q., Gu CZ., Cui Z.
The nanocrystalline diamond films with different morphologies and roughness were synthesized by a bias-assisted hot filament chemical vapor deposition method. It was found that the nanocrystalline diamond film exhibited low-k dielectric properties with the increase of CH4 concentration during diamond deposition. The low-k nanocrystalline diamond film with grain size of around 40 nm and dielectric constant of 2.4 was obtained at the CH4 concentration of 16% and the bias of -140 V. The low dielectric constant can be mainly attributed to the decrease of diamond grain sizes and the formation of more nanopores in as-grown nanocrystalline diamond film, both of which were discussed in details based on the grain size determined band gap expansion effect and the two-phase dielectric mixing model, respectively. © 2007 American Institute of Physics.