Arsenic diffusion in Si and Si 0.9 Ge 0.1 alloys: Effect of defect injection
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B9.3.1/C9.3.1
Arsenic diffusion in Si and Si0.9Ge0.1 alloys: Effect of defect injection Suresh Uppala , J. M. Bonarb , Jing Zhangc , and A. F. W. Willoughbya a Material Research Group, School of Engineering Sciences, b School of Electronics and Computer Science, University of Southampton, Southampton, SO17 1BJ, United Kingdom c EXSS, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW, United Kingdom
ABSTRACT Results of intrinsic As diffusion in Si as well as in strained and relaxed Si0.9 Ge0.1 layers are presented. Using Molecular Beam Epitaxy in-situ As doped epitaxial Si and compressively strained and relaxed Si-Ge layers were grown on Si substrates. The samples were annealed using Rapid Thermal Annealing (RTA) at 1000 ◦ C. Arsenic diffusion is seen to be enhanced in SiGe than in Si. The enhancement factor is calculated to be 2.3 and 1.3 for relaxed and strained Si0.9 Ge0.1 , respectively. Also, using RTA in oxygen atmosphere, interstitial and vacancies were selectively injected in to the sample structures. Diffusion enhancement is also recorded in Si and Si-Ge structures with interstitial as well as vacancy injections over inert anneal. The results suggest that both interstitial and vacancy defects contribute to As diffusion in Si and Si0.9 Ge0.1 . INTRODUCTION Due to an increased interest in SiGe alloys for Heterojunction Bipolar Transistors and strained Si based Metal Oxide Semiconductor Field Effect Transistor (MOSFET) devices, dopant diffusion in these alloys has been studied by various researchers [1, 2, 3]. While B diffusion is retarded in SiGe [4], Sb, P and As diffusion has been shown to be enhanced in SiGe as compared to Si [5, 6]. In the past, As diffusion in SiGe has been investigated by implantation in SiGe layers [3, 7, 8, 9]. Eguchi et al. [3] reported enhanced extrinsic diffusion of As in relaxed SiGe alloys over Si and suggested a stronger vacancy component for As diffusion in SiGe than in Si. Laitinen et al. [10] have used very low dose radiotracer implantation to study intrinsic As diffusion in Si1−x Gex over the full range of alloy compositions. By comparing their results with the diffusion of other impurity atoms and self-diffusion in Si-Ge alloys, they have argued the participation of interstitial as well vacancies and the dominance of vacancies for As diffusion in alloy range 0 ≤ x ≤ 0.35 and 0.35 ≤ x ≤ 1, respectively. Pakfar [11] has also studied intrinsic As diffusion in Si and strained SiGe alloys and found increased As diffusion in strained SiGe alloys as compared to in Si. In this report, we present the results of intrinsic As diffusion in Si and strained as well as relaxed Si0.9 Ge0.1 epitaxial layers at 1000 ◦ C. Additionally, we report on the effect of selective point defect injection on As diffusion in these layers.
B9.3.2/C9.3.2
EXPERIMENTAL PROCEDURE Epitaxial Si and strained/relaxed Si0.9 Ge0.1 layers with in-situ doped As marker layers were grown using Gas Source Molecular Beam Epitaxy (GSMBE). Epitaxial Si layers were grown at 700 ◦ C. The A
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