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

Abstract

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 SiO2 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 SiO2 which corresponds to the first absorption peak in the imaginary part of dielectric function is found to be at around 9eV. We observed that in the case of dense low-k material, there appears a finite density of states (DOS) inside the band gap of SiO2, whereas the inclusion of porosity into dense low-k network diminishes the in-gap DOS and widens the band gap to around 10eV.