Modeling of Boron Implantation Into Si With Decaborane Ions
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Modeling Of Boron Implantation Into Si With Decaborane Ions Zinetulla Insepov1), Marek Sosnowski2), and Isao Yamada1) 1 ) Himeji Institute of Technology, 3-1-2 Koto, Kamigori, Ako, Hyogo 678-1205, Japan 2 ) New Jersey Institute of Technology, USA ABSTRACT A molecular Dynamics (MD) model of B implantation into Si and of sputtering the Si surface with energetic B10 clusters has been developed. The goal was to simulate the implantation of ions of decaborane (B10H14), which may become an important process for the formation of ultra shallow junctions in future MOS devices. The simulations, carried out for the cluster ion impact energy from 3.5 keV to 15 keV, have revealed the formation of a large amorphized region in a subsurface region. At low cluster impact energies in this range some of the B atoms were recoiled back from the surface, but at the energy of 12 keV and above almost all of the Boron atoms were successfully implanted into Si. The sputtering yield of Si has been also computed and found to increase with energy, reaching the value of 6 Si atoms per B10 cluster at 15 KeV. The number of displaced surface atoms correlates well with the sputtering yield, and between 3.5 and 10 keV it has a non-linear dependence on energy. At higher energies the number of displaced atoms increases linearly with energy, in agreement with the Khinchin-Pease formula [9]. The sputtering yield at 12 keV was also measured by the amount of Si removed by a decaborane beam from a thin Si film deposited on a carbon substrate. The predicted sputtering yield agrees well with this experiment. INTRODUCTION Implantation of decaborane (B10H14) cluster ions has recently attracted much attention because this new method of introducing B into Si has important advantages over the conventional technique of implanting single atomic ions to obtain very shallow doping. This method has been first successfully realized by a group at Kyoto University in collaboration with Fujitsu Corporation [1]. In these studies, low-energy decaborane ions have been implanted into Si and thermally annealed at a temperature of about 800 - 1000 °C by RTA. It has been shown that very shallow junctions have been obtained nd that this method could be a promising new technique for future small-scale PMOS devices. After the first experiments with decaborane have been published, it has been realized that the TED effect, the anomalously high boron diffusion rate that has been inherent in conventional implantation, still may persist [2]. One of the feasible explanations of the TED is based of the fact that every implanted B+ ion creates at least one Si-interstitial (the so called +1 model), and that the highly mobile B interstitials are created by the kickout mechanism caused by the Si self-interstitials [3]. Ion implantation and dopant diffusion in Si is a well-studied area of semiconductor physics (see e.g. [4]). In contrast, there have been very little published papers to date on modeling of low energy decaborane implantation [5]. Unfortunately, MD modeling of cluster impacts can
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