Properties of low dielectric constant fluorinated silicon oxide films prepared by plasma enhanced chemical vapor deposition

Abstract

The chemical and electrical properties of fluorinated silicon oxide films prepared by plasma enhanced chemical vapor deposition at 180°C were studied. The deposition of these films was made by incorporating CF4 as the fluorine source into the deposition process of SiO2 films using Si2H6 and N2O. With increasing CF4 flow, the deposition rate of these films decreased; meanwhile, the P-etch rate increased. With post-deposition anneal, the thickness of the films without CF4 slightly decreased; meanwhile, the thickness slightly increased with the incorporation of CF4. The Fourier transform infrared (FTIR) spectroscopy showed that the characteristic peak around 940 cm−1 due to the Si–F stretching bonds increased with increasing CF4 flow, also the Si–O stretching wave number increased but its full width at half maximum decreased with increasing CF4 flow. The dielectric constant evaluated by high frequency capacitance-voltage measurements decreased from 4.13 to 3.52 as the CF4 flow increased. In addition, the effective oxide charge density and interface trap density also decreased with increasing CF4 flow. The ramp current-voltage measurements showed that the leakage current density of the films decreased with increasing CF4 flow. However, high average breakdown field strength with low early failures was observed for medium flow of CF4.