WATER-ABSORPTION PROPERTIES OF FLUORINE-DOPED SIO2-FILMS USING PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

The water absorption properties of a PE-CVD (plasma-enhanced chemical vapor deposition) fluorine-doped SiO2 film with a low dielectric const ant were studied. It was concluded that highly stable F-doped SiO2 fil m was obtained at F contents from 2.0% to 4.2% (3.2 less than or equal to k less than or equal to 3.6) using high-density plasma CVD. Howeve r, at F contents higher than 4.2% (k <3.2); the amount of water absorp tion was markedly increased due to the presence of Si-F bonds, such as Si(-F)(2) bonds, which are highly reactive with water. On the other h and, water absorption was observed at every F content for conventional plasma CVD films. Through gas phase component analysis and investigat ion of the incident ion energy distribution using a quadrupole mass sp ectrometer, it was confirmed that a high efficiency of gas dissociatio n and high-energy ion bombardment are the keys to obtaining high-quali ty films with a high resistance to water absorption.