Hot-mesh Chemical Vapor Deposition for 3C-SiC Growth on Si and SiO 2
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A8.11.1
Hot-mesh Chemical Vapor Deposition for 3C-SiC Growth on Si and SiO2 Kanji Yasui, Jyunpei Eto, Yuzuru Narita, Masasuke Takata, Tadashi Akahane Department of Electrical, Electronics and Information Engineering Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188, Japan ABSTRACT The crystal growth of SiC films on (100) Si and thermally oxidized Si (SiO2/Si) substrates by hot-mesh chemical vapor deposition (HMCVD) using monomethylsilane as a source gas was investigated. A mesh structure of hot tungsten (W) wire was used as a catalyzer. At substrate temperatures above 750˚C and at a mesh temperature of 1600˚C, 3C-SiC crystal was epitaxially grown on (100) Si substrates. From the X-ray rocking curve spectra of the (311) peak, SiC was also epitaxially grown in the substrate plane. On the basis of the X-ray diffraction (XRD) measurements, on the other hand, the growth of (100)-oriented 3C-SiC films on SiO2/Si substrates was determined to be achieved at substrate temperatures of 750-800˚C, while polycrystalline SiC films, at substrate temperatures above 850˚C. From the dependence of growth rate on substrate temperature and W-mesh temperature, the growth mechanism of SiC crystal by HMCVD was discussed. INTRODUCTION Silicon carbide (SiC) is an important wide-gap semiconductor for application in high-temperature and high-power devices, because of its chemical and thermal stability and high electrical breakdown strength [1, 2]. Its high stiffness, high mechanical strength and extreme chemical inertness also make it suitable for use in micro-electromechanical system (MEMS) applications in chemically and physically harsh environments at high temperatures [3, 4]. In the conventional atmospheric-pressure chemical vapor deposition (CVD) method, 3C-SiC can be grown on Si substrates at higher than 1000˚C after the formation of a carbonization layer [5]. Because of the high vapor pressure of Si at such a high temperature [6], structural damage and the formation of voids are liable to occur at the interface between SiC and Si. These degrade the morphology of the carbonization layer and the epitaxial layer. Therefore, lowering the epitaxial growth temperature of SiC is of crucial importance in fabricating devices such as hetero-bipolar transistors using a SiC/Si structure. In addition, heteroepitaxial growth on a new buffer layer that is unstable at high temperatures becomes possible by low-temperature crystal growth, instead of on a carbonization layer. In our previous study of the experiments by triode plasma CVD [7], H radicals generated in the RF plasma were considered to enhance the crystal growth at low temperatures through the extraction of H atoms and excessive methyl groups from source molecules on the growing film surface. By catalytic reaction on the hot tungsten (W) wire surface, H2 gas can be effectively decomposed and high-density hydrogen radicals can be generated [8]. Using the catalytic reaction on the hot W wire, heteroepitaxial growth of 3C-SiC may be realized at low temperatures. In addition,
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