Dielectric properties of fluorinated silicon dioxide films

Abstract

Amorphous fluorinated Si dioxide (a-SiO 2:F) films were deposited at 300°C by plasma-enhanced chemical vapor deposition (PECVD) using SiH 4–O 2–CF 4 mixtures with different RF power and deposition temperatures T d. Their bonding and dielectric properties were investigated. The F content, deposition rate and dielectric constant, ε s, decreased and water resistance improved as either RF power or T d increased. However, for obtaining a film with both small ε s and high water resistance, the value of ε s was limited to ε s ≈ 3. It is proposed that increased water absorption could be caused by occurrence of high tensile stress in the films, and that high-decomposition rates of CF 4, high-energy ion bombardment and/or easier surface migration of adsorbates during film growth, caused by increasing RF power or T d, act to remove weak Si–O and Si–F bonds, resulting in films with low ε s and high water resistivity.