A preliminary study on the etching behavior of SiO ₂ aerogel film with CHF ₃ gas

Etching behavior of SiO ₂ aerogel film has been investigated in order to examine the feasibility of its application to an interlevel dielectric material. Low dielectric property of SiO ₂ aerogel film is simply originated from its highly porous structure, but interconnected particles are covered with surface chemical bondings (-OH, -OC ₂H ₅, etc). Etching experiments have been performed with high density inductively coupled CHF ₃ plasma. The effects of porous structure and surface chemical bondings on the etching of SiO ₂ aerogel film have been analyzed. The changes of surface morphology were observed using scanning electron microscopy. X-ray photoelectron spectroscopic analyses revealed compositions and chemical bonding states of reaction layer. From the analyses, 3-dimensional etching was not feasible macroscopically in SiO ₂ aerogel film even with its porous nature because network structure was maintained through the etching process. Internal surface chemicals seemed to act as an etching barrier by reacting with active fluorine and to control the etch rate.