Characterization of low dielectric SiOC films deposited via hydrogen plasma atomic layer deposition

Abstract

Low-dielectric constant SiOC thin films were deposited by remote plasma atomic layer deposition. Octamethylcyclotetrasiloxane (OMCTS) was used as precursor, and H2 plasma was used as reactant. To investigate the thermal stability of the deposited thin film, samples deposited at various temperatures were annealed at 800 ℃ in a N2 atmosphere. The lowest measured dielectric constant of the deposited samples was about 3.2, which was lower than thermal-grown SiO2. Leakage current densities were 10-8 to 10-7 A / cm2. The refractive index (RI) of deposited thin films ranged from 1.4 to 1.46, lower than that of bulk SiO2. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were utilized to investigate the chemical bonding structure of the thin films. XPS C 1s and Si 2p spectra indicated that oxygen and carbon were bonded to silicon. Si-O-(C)-Si bonds were examined by analyzing the absorption energy spectra of FTIR in the 1000 cm-1 -1200 cm-1 region. Absorption peaks appeared in the open structure region at 1115 cm-1 and the cage structure region at 1150 cm-1. Structural changes from open structure to cage structure were observed after annealing. The Si-CH3 peak at 1340 cm-1 and the Si-H peak at 900 cm-1 were observed, which means that the thin film was an MSQ (methyl silsesquioxane) and HSQ (hydrogen silsesquioxane) - like structure.