Effect of supercritical drying on sol-gel deposited silica aerogel thin films at different temperatures

Abstract

Now a days silica aerogel thin films are attracted more attention as an interlayer dielectric (ILD) application in ULSI technology due to the lowest dielectric constant. In present work, we report the successful deposition of silica aerogel thin films on Si wafer by sol-gel technique. Further, in order to introduce porosity the deposited thin films were dried at supercritical condition with different temperatures. Elipsometric study shows that the refractive index (RI) of as deposited film is observed to 1.44 whereas RI of super critically dried thin films is observed to be decreased to 1.29 for the film dried at 40oC. The film thickness observed to be decreased from 200nm to 129nm with increase in supercritical drying temperature. The dielectric constant of the films is observed to be lowered to 2.8 for the film dried at 40oC temperature. The pore volume and porosity of the films increased up to 0.25 and 37% respectively with increase in drying temperature while the density of the films is decreases with increasing temperature.