Preparation and Characteristic Analysis of Ultra-Low Dielectric Constant Nano-Porous Silicon Oxide Films

Abstract

In order to reduce the dielectric constant of nano-silicon oxide films, the effects of preparation and post-treatment methods on the structure of nano-porous silicon oxide materials are investigated. Herein, using plasma enhanced chemical vapor deposition (PECVD) method, hexamethyldisiloxane (HMDSO) is as monomer and dimethoxyethane (DME) as porogen. The silicon oxide film is deposited on the glass substrate surface, and then it is heat-treated at a high temperature, so organic components such as carbon-hydrogen bonds are removed and the pores are formed to reduce the dielectric constant. At the same time, the skeleton of the nano-porous silicon oxide film is cured by ultraviolet irradiation. The surface morphology of the film is observed by scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) is used to investigate the effects of ultraviolet irradiation with different wave numbers on the composition of it. Also, using ellipsometer, the refractive index of it is tested, and its dielectric constant is calculated. The effect of porogen on the microstructure and properties of it is investigated by adjusting the dosage of porogen and post-treatment methods. The results show that the method is effective. When the ratio of porogen and monomer is 1:5, the dielectric constant of the prepared nano-porous silicon oxide film is the lowest. The short wavelength ( λ = 185 nm) cures modified the chemical structure and obtained higher Young’s moduli. While the higher wavelength (λ > 300 nm) cures resulted in less modification of it and more elimination of the porogen.