Chemical Bonding, Permittivity and Elastic Properties in Locally Modified Organosilicate Glass
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0914-F11-03
Chemical Bonding, Permittivity and Elastic Properties in Locally Modified Organosilicate Glass Ehrenfried Zschech1, Heiko Stegmann2, Patrick Hoffmann3, Dieter Schmeisser3, Pavel Potapov1, Hans-Juergen Engelmann1, Dmytro Chumakov1, and Holm Geisler1 1 AMD Saxony LLC & Co. KG, Wilschdorfer Landstrasse 101, Dresden, Saxony, D-01109, Germany 2 Carl Zeiss NTS GmbH, Carl-Zeiss-Strasse 56, Oberkochen, Bayern, D-73447, Germany 3 Angewandte Physik - Sensorik, BTU Cottbus, Konrad-Wachsmann-Allee 17, Cottbus, Brandenburg, D-03046, Germany ABSTRACT Changing local electronic polarizability and chemical bonding in OSG in such a way that the effective permittivity - and consequently the electrical performance of the Cu/low-k structure - deteriorates only slightly and that adhesion and stiffness are improved significantly is an extremely challenging task [1], [2]. As the interconnect line spacings continue to shrink, optimization of the electrical and mechanical properties of the ILD material becomes increasingly important for Cu/low-k integration since the effect of thin regions that have been modified by special treatments on the effective material properties, e. g. keff, increases. Composition and chemical bonding, changed by plasma or beam treatments, effect the materials properties significantly. Plasma processes for resist stripping, trench etching and post-etch cleaning remove C and H containing molecular groups from the near-surface layer of OSG. Electron-beam interaction with OSG changes the chemical bonding in the low-k material. In this paper, the effect of chemical bonding on permittivity and elastic modulus is studied. Compositional analysis and chemical bonding characterization of structured ILD films with nanometer resolution is done with electron energy loss spectroscopy (EELS). The fine structure near the C-K electron energy loss edge, allows to differentiate between C-H, CC, and C-O bonds, and consequently, between individual low-k materials and their modifications. Dielectric permittivity changes are studied based on VEELS (valence EELS) measurements and subsequent Kramers-Kronig analysis. The elastic modulus is determined with atomic force microscopy (AFM) in force modulation (FM) mode. Nanoindentation was applied as a complementary technique to obtain reference data. INTRODUCTION Insulating low-k dielectric materials are needed to diminish power consumption and to minimize cross-talk between on-chip metal interconnects in leading-edge microelectronic products [3], [4]. Organosilicate glass (OSG) is one of the current approaches to reduce the k value of interlayer dielectric (ILD) materials. In OSG, the substitution of oxygen in SiO2 by methyl groups (-CH3) reduces the permittivity significantly, since the electronic polarizability is lower for Si-C bonds than for Si-O bonds. Plasma and beam treatments (particularly oxygen plasma and electron beam treatments) modify the OSG material at least locally. It is an extremely challenging task to understand the changes in the local polarizability and the ch
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