Incubation Time Free CVD-TiO 2 Film Preparation Using Novel Precursor of Ti-DOT
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Incubation Time Free CVD-TiO2 Film Preparation Using Novel Precursor of Ti-DOT Hirokazu Chiba1, Ken-ichi Tada2, Toshiki Yamamoto1, 2, Kohei Iwanaga1, 2, Atsushi Maniwa1, Tadahiro Yotsuya1, 2, Noriaki Oshima1, 2, and Hiroshi Funakubo3 1 TOSOH Corporation, Hayakawa 2743-1, Ayase, Kanagawa, 252-1123, Japan 2 Sagami Chemical Research Institute, Hayakawa 2743-1, Ayase, Kanagawa, 252-1193, Japan 3 Department of Innovative and Engineered Materials, Tokyo Institute of Technology, J2-43, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8502, Japan ABSTRACT Titanium oxide thin films were deposited at 250 – 400 oC on amorphous SiO2 prepared on n-type Si substrates by chemical vapor deposition (CVD) using a novel precursor, ethene-1,2diylbis(tert-butylaminido)diisopropoxotitanium [Ti[N(tBu)C=CN(tBu)](OiPr)2 , Ti-DOT], with oxygen gas as an oxidant. Deposition characteristics of thin films were compared with those using titanium tetraisopropoxide [Ti(OiPr)4, TTIP]. As a result, the deposition amount of TiO2 thin films using Ti-DOT was larger than that of TTIP because of the shorter incubation time in the case of Ti-DOT. Smaller surface roughness was observed for the films using Ti-DOT. In addition, a good conformability was obtained on amorphous SiO2 hole prepared on n-type Si substrate substrate with aspect ratio of 5. INTRODUCTION TiO2 thin films have attracted much attention for a wide range of applications, for instance, antireflection films [1], photocatalysts [2], and biocompatible materials [3], owing to its specific functional properties. Among various deposition techniques, atomic layer deposition (ALD) and chemical vapor deposition (CVD) have a great advantage in providing excellent film uniformity and flatness over a large surface area of the substrate. Titanium tetraisopropoxide (TTIP) has been extensively studied as a liquid precursor to prepare TiO2 thin films by ALD and CVD because of its high vapor pressure, noncorrosive by-products, and the high cost efficiency compared to other metal organic precursors [4-6]. However, TiO2 film preparation has not been widely investigated [7,8]. In this study, we synthesized a novel precursor, ethene-1,2-diylbis(tertbutylaminido)diisopropoxotitanium [Ti[N(tBu)C=CN(tBu)](OiPr)2 , Ti-DOT], and evaluated its deposition characteristics to prepare TiO2 thin films by CVD with oxygen gas as an oxidant. We also examined its incubation time and film surface flatness as well as the step coverage. EXPERIMENT TTIP was supplied from Aldrich. The synthesis of Ti-DOT is by the following method. N,N'-di-tert-butyl-1,4-diazabuta-1,3-diene (2.22 g, 13.2 mmol) [9] was dissolved in 20 mL of tetrahydrofuran and then sodium (606 mg, 26.4 mmol) was added. The reaction mixture was stirred at room temperature for 12 h. The resulting deep-red solution was added dropwise at −70 o C to a solution of Ti(OiPr)4 (3.56 g, 12.5 mmol) in 10 mL of hexane. The resulting mixture was allowed to warm to room temperature and stirred for 14 h. The solvent was removed under
vacuum and the residue was extracted
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