Tween-80 based ultra low-k (ULK) mesoporous films

The non-ionic surfactant polysorbate 80 (Tween-80) based single step HF assisted mesoporous low-k films were synthesized by using sol-gel spin coating technique. The obtained films were annealed at 150 A degrees C for 1 h to remove the added porogen and the pore solvents. Film thickness and refractive index were measured by spectral ellipsometry and changes in chemical compositions were investigated by using FTIR spectroscopy. The formation of SiO2 in film matrix and incorporation of low polar bonds like F and C were confirmed from obtained FTIR spectra. The porous nature of deposited film was confirmed from FE-SEM micrograph and the measured average pore diameter of mesopores was found to be 16.54 nm. The highest porosity percentage of 60.74% was obtained for the annealed sample deposited with 1 ml of Tween-80 in coating solution. The measured RMS roughness of the samples before and after annealing was observed to be increased from 0.029 to 0.079 nm. The lowest dielectric constant extracted from C-V curve measurement is of 1.06. These obtained mesoporous films with lower k value of 1.06 may be a suitable candidate as interlayer dielectric (ILD) for back end of line (BEOL) in CMOS technology.