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Unformatted text preview: Formation of modified Si/SiO 2 interfaces with intrinsic low defect concentrations L. G. Gosset, a) J. J. Ganem, H. J. von Bardeleben, S. Rigo, I. Trimaille, J. L. Cantin, T. Åkermark, and I. C. Vickridge Groupe de Physique des Solides, Universite ´s Paris 6 et 7, UMR-CNRS 75-88, 2 place Jussieu, 75251 Paris Cedex 5, France ~ Received 14 September 1998; accepted for publication 17 December 1998 ! The modification by postoxidation NO treatments of the Si/SiO 2 interface in thermally grown Si ~ 100 ! /SiO 2 layers has been studied by nuclear reaction analysis and electron paramagnetic resonance spectroscopy. Our results demonstrate a selective incorporation of NO molecules at the Si/SiO 2 interface and a drastic reduction in the interface defect density. In this new configura- tion, the Pb center density, which is typically 2 3 10 12 cm 2 2 in the as oxidized samples, is reduced to below 10 11 cm 2 2 without any hydrogen passivation. The thermal treatment in NO atmos- pheres opens the perspective for the formation of hydrogen free low defect Si ~ 100 ! /SiO x N y interfaces conserving the qualities of the SiO 2 dielectric. © 1999 American Institute of Physics. @ S0021-8979 ~ 99 ! 05906-X # I. INTRODUCTION The interface structure of thermally grown Si ~ 100 ! /SiO 2 has been extensively studied for over three decades and a large amount of information has been accumulated by a va- riety of techniques such as electron microscopy, photoelec- tron microscopy, electrical measurements ranging from C – V studies to charge pumping techniques and electron paramag- netic resonance spectroscopy ~ EPR ! . 1 Nevertheless, the mo- lecular reactions taking place during the high temperature oxydation and the resulting structure of the oxide within the first few monolayers from the interface were and are still actively debated. 2–4 The ~ 100 ! Si/SiO 2 structure is particu- larly well suited for studies of the interface formation since due to its technological importance, the experimental condi- tions are extremely well controlled. As for all interfaces connecting two different crystal structures, the Si/SiO 2 interface has to accommodate the structural mismatch between the Si lattice and the SiO 2 layer. This is achieved by the formation of a thin ~ two or three atomic layers ! transition region between the crystalline sili- con and the amorphous SiO 2 containing a high fraction of Si atoms in intermediate ~ 1 1 ,2 1 ,3 1 ! oxidation states 4–6 and of electrically active point defects at the interface, the so called P b and P b 1 centers. 7–9 The interface defect concentration varies only weakly with the oxidation conditions ~ tempera- ture, pressure, oxide thickness ! and is of the order of 2 3 10 12 cm 2 2 with nearly equal amounts of P b and P b 1 centers....
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