Formation mechanism for TiO x thin film obtained by remote plasma enhanced chemical vapor deposition in H 2–O 2 mixture gas plasma

Abstract

TiO x thin film formation mechanism from titanium tetraisopropoxide [Ti-(O- i-C 3H 7) 4, TTIP] by remote plasma enhanced chemical vapor deposition (RPE-CVD) was investigated. Plasma was generated by a microwave discharge in single H 2, O 2, or H 2–O 2 mixture gases. Emission spectra measurements suggested that H radical atoms dissociated TTIP molecules. By addition of O 2 to H 2 gas, the H radical density and film deposition rate drastically increased. Moreover, it was proved that the deposition rate was decreased by OH radical molecules formed in H 2–O 2 mixture gas plasma. OH radical molecules caused deactivation of precursors and hence suppressed TiOTi bond formation in the gas phase. The highest deposition rate of 11 nm/min, which was two orders higher than that for the case of single gas plasma, was obtained in the case of mixture gas ratio of 80% H 2 and 20% O 2. The substrate temperature had not affected the deposition rate, but significantly changed the film structure. It is concluded that the use of H 2–O 2 mixture gas is effective for obtaining a high deposition rate for the RPE-CVD process, and the deposition rate strongly depends on H radical density and ratio of H and OH radical densities.