Formation mechanism for TiOx thin film obtained by remote plasma enhanced chemical vapor deposition in H2-O2 mixture gas plasma

TiO2 thin film formation mechanism from titanium tetraisopropoxide [Ti-(O-i-C3H7)(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, 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. (C) 2001 Elsevier Science B.V All rights reserved.