Emily Thomson1 Mahmut Sami Kavrik1 Andrew Betts1 Andrew Kummel1

1, UCSD, La Jolla, California, United States

The use of high mobility SiGe channels in CMOS technology has been impeded by the presence of a high interface defect density between the SiGe and oxide layers. Ge-Ox suboxide bonds at the interface are the main source of these defects. By selectively forming Si-Ox bonds or suppressing formation of Ge-Ox bonds, the interface defect density can be minimized. The higher heat of formation of SiOx compared with GeOx can be used to selectively remove GeOx using an oxygen scavenging metal as the MOSCAP gate metal [1,2]. Previously, Al gate metal has been demonstrated as reducing Dit for Al2O3. In the present work, Al gate metal is used to attain an even lower Dit using HfO2 as the oxide and an optimized forming gas anneal. In this work, thermally deposited aluminum was used as an oxygen scavenging gate metal to achieve an ultra-low defect density of 3x1011 eV-1cm-2 on ALD deposited Al2O3 and HfO2 oxides on Si0.3Ge0.7(100). Aluminum gate metal MOSCAPs were also shown to have an order of magnitude lower leakage current than nickel gate MOSCAPS sweeping from -2 to 2 Vg. Ni gated MOSCAP showed a higher maximum capacitance (2.1 μF/cm2) in comparison with Al gated MOSCAPs (1.5 μF/cm2) due to the growth of Al2O3 during oxygen scavenging. STEM-EDS and EELS results confirm the oxygen scavenging mechanism by showing a silicon rich, sub 5Å thick SiGe-oxide interface.

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[2] Liu, C. W., Östling, M. & Hannon, J. B. New materials for post-Si computing. MRS Bull. 39, 658–662 (2014).