Void Formation in Hydrogen Implanted and Subsequently Plasma Hydrogenated and Annealed Czochralski Silicon

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Void Formation in Hydrogen Implanted and Subsequently Plasma Hydrogenated and Annealed Czochralski Silicon R. Job 1), W. Düngen 1), Y. Ma 1), Y. L. Huang 1), J. T. Horstmann 2) 1) University of Hagen, Department of Electrical Engineering and Information Technology, D-58084 Hagen, Germany 2) University of Dortmund, Faculty of Electrical Engineering and Information Technology, D-44227 Dortmund, Germany ABSTRACT By µ-Raman spectroscopy the formation of hydrogen related defects (vacancy-hydrogen complexes, hydrogen saturated silicon dangling bonds, H 2 molecules in multi-vacancies and voids/ platelets) has been investigated in H-implanted and subsequently H-plasma exposed and annealed Czochralski (Cz) silicon wafers. Annealing was done either in air or in an ambient containing hydrogen (forming gas). The investigations were applied under conditions, which are relevant for ion-cut processes and layer exfoliation in Cz Si for SOI-wafer fabrication at reduced implantation doses (as compared to standard procedures like the smart-cut process). INTRODUCTION To follow the predictions of the International Technology Roadmap for Semiconductors (ITRS), recently, the so-called smart-cut process for the production SOI-wafers (silicon on insulator) became well known [1]. For the transfer of thin Si-layers onto an isolating substrate, splitting of wafers parallel to the bonding SiO2-Si interface along buried defect layers is required. In the smart-cut approach such a buried defect layer is formed by H-implantation (H+) with doses of ~ 3⋅1016 cm-2 and higher. During post-implantation annealing at ∼ 550 °C microcavities filled with H 2 molecules are formed, which can grow due to the high H 2 gas pressure. If the H-implanted wafer surface was bonded onto an oxidized wafer, during annealing the microcavities grow parallel to the wafer surface and coalesce so that a thin Si-layer is completely separated along the buried defect layer and transferred to the oxidized wafer. It was recently demonstrated that by a combined H-implantation and subsequent H-plasma exposure the required implantation doses can be significantly reduced below 1016 cm-2 [2], and for this case even thinner exfoliated Si-layers should be transferable as compared to the conventional smartcut procedure [2]. In the current article a brief investigation by µ-Raman spectroscopy (µRS) is presented, which was conducted in view of such H-plasma supported ion-cut processes and based on recent studies concerning H-plasma caused damage in Czochralski silicon (Cz Si) wafers [3-9]. EXPERIMENTAL Hydrogen was implanted into p-type (100) Cz Si wafers (15 – 25 Ωcm) with an energy of 40 keV, a dose of 1⋅1016 cm-2 and an ion current of 30 – 40 µA. H-plasma treatments were applied for 1 hour at 110 MHz and 50 W (H 2 flux: 200 sccm, pressure: 400 mTorr) in a PECVD (Plasma Enhanced Chemical Vapor Deposition) chamber. The wafers were fixed face down onto the

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