Effect of fluorine flow and deposition temperature on physical characteristics and stability of fluorine-doped siloxane-based low-dielectric-constant material

Abstract

The effects of SiF(4) flow rate and deposition temperature on the physical properties and stability of fluorine-doped organo-silica-glass (OFSG) films were investigated. The porosity of the as-deposited OFSG dielectrics declines as the flow rate of SiF(4) gas and the deposition temperature increase, increasing the dielectric constant. However, newly formed Si-F bonds have less electronic polarizability, reducing the dielectric constant. These traded-off properties yield a minimum dielectric constant of the OFSG film deposited at 250 degrees C with a SiF(4) flow rate of 100 SCCM (SCCM denotes cubic centimeter per minute at STP). The stability of Si-F bonds in the OFSG films is related to the deposition conditions. OFSG films deposited a higher SiF(4) flow rate (>400 SCCM) or a lower deposition temperature (< 300 degrees C) have lower thermal stability and are less well protected against moisture because of the instability of Si-F bonds. Therefore, more attention should be paid to the conditions for depositing fluorine-doped OFSG dielectrics.