Remote Plasma Enhanced Chemical Vapor Deposition of TiO x Films from Titanium Tetraisopropoxide
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Remote Plasma Enhanced Chemical Vapor Deposition of TiOx Films from Titanium Tetraisopropoxide Masatoshi Nakamura1, Shinichi Kato2, Toru Aoki2 and Yoshinori Hatanaka1, 2 1 Graduate School of Electronic Science and Technology, Shizuoka University 2 Research Institute of Electronics, Shizuoka University 3-5-1 Johoku, Hamamatsu, 432-8011, Japan ABSTRACT
TiOx thin films were prepared from titanium tetraisopropoxide (Ti-(O-i-C3H7)4, TTIP) in a remote plasma enhanced chemical vapor deposition (RPE-CVD) using a mixture of hydrogen/oxygen plasma gas. Emission spectra suggested that H-radicals dissociated TTIP molecules in gas phase. By mixing with oxygen, H-radical density was increased with the correlation effect to result in enhancement of deposition rate. Deposition rate was also influenced by OH-radicals. OH-radicals caused deactivation of precursors and hence suppressed Ti-O-Ti bond formation in 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 achieved in the case of mixture gas ratio of 20% oxygen and 80% hydrogen. Surface reaction due to the heated substrate did not affect the deposition rate though the film structure was remarkably changed. It was demonstrated that for RPE-CVD process, oxygen/hydrogen mixture gas plasma was effective for obtaining high deposition rate, and also H-to-OH radical density ratio was an important factor to control the deposition rate.
INTRODUCTION Plasma enhanced chemical vapor deposition (PE-CVD) method is effective for the film formation in low temperature process due to the high reactivity of energetic species. PE-CVD process has been applied for the various film formations such as poly-Si [1], SiNx [2], ZnO [3]. Furthermore, remote plasma enhanced chemical vapor deposition (RPE-CVD), in which only long life neutral radicals are concerned in the film formation process, has been developed for preparing high quality films free from ions and electrons bombardment. RPE-CVD process is also suitable for the investigation of the film formation mechanism. Using RPE-CVD process, Xu et al. studied the deposition process of SiC film from organosilicon and showed that the introduction of some hydrogen into plasma gas enhanced the deposition rate [4]. TiO2 thin film, which is indispensable for optical field because of its high refractive index and stability, has often been fabricated by sol-gel [5], sputtering [6] and PE-CVD [7,8]. However, in these methods the substrate damage caused from the high temperature, and ions and electrons bombardment is high. We believe that in the RPE-CVD it is possible to obtain the films free from substrate damage in low temperature process. In this study, TiOx thin films were prepared from titanium tetraisopropoxide (Ti(O-i-C3H7)4, TTIP) by RPE-CVD process. We attempted the use of a mixture of hydrogen and oxygen plasma gas, because it is well known that TTIP sensitively reacts with water in sol-gel process. Effect of plasma gas mixture on the deposition rate was investigated. A pos
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