The dielectric response of low-k interlayer dielectric material characterized by electron energy loss spectroscopy

In this study, the dielectric response of low-k dielectric materials has been characterized by electron energy loss spectroscopy. A widely accepted fast Fourier transform based Kramers–Kronig method (Johnson, 1975) [3] has been used to derive the high-frequency response of these materials. We used three different low-k dielectric materials to find out the effect of porosity and carbon content on the dielectric response of materials. Amorphous SiO 2 and SiC:H samples are used for comparison. All samples were deposited by plasma-enhanced chemical vapor deposition technique. A Lorentzian-based oscillator model has been used to determine the eigen-energy of excitations by fitting the measured loss function. The model is specially designed to let all oscillator parameters move freely and find their most probable position by using a least square fitting analysis procedure. The band gap for amorphous SiO 2 which corresponds to the first absorption peak in the imaginary part of dielectric function is found to be at around 9 eV. We observed that in the case of dense low-k material, there appears a finite density of states (DOS) inside the band gap of SiO 2 , whereas the inclusion of porosity into dense low-k network diminishes the in-gap DOS and widens the band gap to around 10 eV.