Effects of Nitrogen Addition to Fluorinated Silicon Dioxide Films

Amorphous fluorinated silicon dioxide (a-SiO2:F) films doped with nitrogen were deposited by changing the ammonia flow rate using plasma-enhanced chemical vapor deposition from SiH4–O2–CF4–NH3 mixtures. The effects of nitrogen addition to the films on both the dielectric constant (es) determined from the capacitance vs. voltage characteristics and the bonding properties examined by infrared absorption measurements, were investigated. These results were also discussed in terms of a change in the partial charge on the constituent Si, O, F and N atoms caused by adding F and N atoms to SiO2 films. When a-SiO2 films are doped by 2-3 at.% with both fluorine and nitrogen under high rf power and high deposition temperature (Td) conditions, films with low es(≈3.2) and high water resistivity were obtained. It was suggested that Si–F bonds, which act to decrease es value, are stabilized by forming Si–N bonds near the Si–F bonds and by removing weaker Si–F bonds under high rf power and high Td.