Investigation of N[sub 2] plasma effects on the depth profile of hydrogen silsesquioxane thin films using high resolution specular X-ray reflectivity

Abstract

Non-destructive, specular X-ray reflectivity (SXR) measurements were used to investigate N2 plasma effects on the density depth profile of hydrogen silsesquioxane (HSQ) thin films. The SXR data indicate that the density profile of an HSQ film without plasma treatment is not uniform with at least four layers with different electron densities. When the HSQ film is treated with increasing plasma power or time exposed to the plasma, oscillations present in the SXR profile of the as-cured HSQ film decrease in amplitude and the absolute value of the reflectivity rapidly decreases. These changes in the reflectivity data are due to increases in the film roughness. Additionally, a layer denser than the rest of the film was observed at the film/air interface of each HSQ film. The thickness of the densified layer increased with plasma power and plasma exposure time. An HSQ film treated with N2 plasma at 200 W for 60 s had an HSQ layer almost fully densified to SiO2 and was approximately 14 nm thick. When the plasma ...