Self-assembled nano-dots of heteroepitaxial SiC on Si
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Self-assembled nano-dots of heteroepitaxial SiC on Si Takashi Matsumoto, Masato Kiuchi, Satoshi Sugimoto 1 and Seiichi Goto 1 Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan 1 Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan ABSTRACT Self-assembled silicon carbide (SiC) nano-dots were fabricated on Si wafers by an organometallic ion beam deposition. The self-assembled SiC nano-dots have the shape of a tile, and were heteroepitaxial SiC on Si.
INTRODUCTION The wide band gap semiconductor SiC is a promising material for high-power and high-temperature device application [1, 2]. Nano-sized heteroepitaxial SiC/Si has potential to be used in resonant tunneling device and quantum light emitting diodes [3, 4]. In this investigation, we fabricated the SiC nano-dots on Si wafers at low growth temperatures by means of an organometallic ion beam. The characteristics of the SiC nano-dots were analyzed by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM).
EXPERIMENTAL DETAILS The fabrication of the SiC nano-dots was performed by a low-energy ion beam deposition system (LEIBD) [5]. The LEIBD system consists of an ion source, a beam transportation unit and a deposition chamber. The single precursor of methylsilicenium ion (SiCH3+) was generated from organosilicon compound: dimethylsilane (SiH2(CH3)2) in a Freeman type ion source. The ion beam was extracted at 25 keV, and only the SiCH3+ ion (mass number: 43) was mass-selected by a sector magnet. The high-energy ion beam collided with residual gases in a drift tube and generated the high-energy neutrals. As the high-energy neutrals couldn’t be controlled by electric and magnetic field, the high-energy neutrals irradiation would cause the damage to the thin film formation. In order to eliminate the high-energy neutrals, the ion beam was deflected by the electro-static field and transported into the deposition chamber, and high-energy neutrals were caught by a stainless steel cup. The SiCH3+ ions were decelerated to
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100±1 eV and deposited on Si(001) wafers (15x15 mm2) at temperatures of 500 - 800 °C [6]. The spot size of the ion beam was 10.0 mm in diameter. The density of the ion beam on the substrate was 0.10-0.20 µA/cm2. The deposition times of the SiC thin film formation were 4 hours. In order to prepare a clean surface, the Si(100) wafers were heated at 1000 °C for 10 minutes in a deposition chamber. By RHEED observation, we confirmed that a Si(001)-(2×1) super structure had appeared. The deposition chamber was held at an ultra high vacuum, with base pressure below 3.9×10-7 Pa and operation pressure below 1.3×10-6 Pa.
RESULTS AND DISCUSSION The crystal structure of the self-assembled SiC nano-dots was analyzed by RHEED in situ. The SiC nano-dots were heteroepitaxial and the (100) lattice planes of 3C-SiC are parallel to the (100)
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