Anomalous Evolution of Bubbles in Krypton-Implanted SiO 2
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0994-F06-04
Anomalous Evolution of Bubbles in Krypton-Implanted SiO2 Hannan Assaf1, Esidor Ntsoenzok1, Marie-France Barthe1, Elisa Leoni1, Marie-Odile Ruault2, and S. Ashok3 1 CERI-CNRS, 3A, rue de la FÈrollerie, OrlÈans, 45071, France 2 CSNSM, CNRS-IN2P3, Batiment 108 - UniversitÈ Paris Sud XI, Orsay, 91405, France 3 Department of Engineering Science and Mechanics, The Pennsylvania State University, 212 Earth and Engineering Science Building, University Park, PA, 16802 ABSTRACT Thermally grown SiO2 was implanted at room temperature with 220keV Kr in order to generate bubbles/cavities in the sample. The formation and thermal stability of these bubbles/cavities is studied in this work. Transmission Electron Microscopy (TEM), Rutherford Backscattering Spectrometry (RBS) and Positron Annihilation Spectroscopy (PAS) were used to obtain a comprehensive characterization of defects (vacancies, interstitital, bubbles, and other types of defects) created by Kr implantation in SiO2 layer. These measurements suggest that the bubbles observed with TEM are a consequence of the interaction between Kr and vacancies (V), with VnKrm complexes created in the entire of implanted zone. After annealing, bubbles/cavities disappear from SiO2 due to the strong desorption of Kr and the decrease in vacancy concentration. INTRODUCTION Bubbles and cavities induced by rare gas implantation have been intensively studied in both metals and semiconductors [1-4]. The study of bubbles in metals is of interest due to their use in nuclear power reactors where they are subjected to high dose helium implantation [5]. In the case of semiconductors such as silicon, bubbles as well as cavities are induced by helium and the cavities find many applications in the area of semiconductor technology including gettering of metallic impurities and wafer delamination techniques [6-8]. In contrast to noble gas implant studies in metals and semiconductors, the formation of bubbles and cavities in amorphous silicon oxide has not received much attention in the literature. In a recent report [9], we demonstrated the formation and the thermal evolution of bubbles/cavities induced by high doses Xe implantation in amorphous SiO2. These results clearly demonstrated that bubbles/cavities induced by Xe are thermally very stable in SiO2. They remain in the material even after exo-diffusion of Xe which occurs at 1100∞C [9]. In parallel, we reported a strong decrease in the dielectric constant of the material, thus providing a new way to engineer low-k dielectric layers, comprising Xe-implanted SiO2 [10]. The big advantage of this technique is retention of thermal SiO2 with all its attractive properties, as the base dielectric. However many questions still need to be addressed, in particular the mechanism of bubble formation and the possibility of using alternate noble gases. We have already demonstrated [9] that neither He nor Ne can generate bubbles/cavities in amorphous SiO2. In continuation of the study, here we report on high dose krypton ion implantation in amorphous SiO2
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