AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA9
Mixed Silicon Dioxide / Tantalum Oxide Layers for High k MOS Gate Dielectrics Formed by Plasma Oxidation of Si and Ta Using a rf Remote N@sub 2@O Plasma Source

Thursday, November 5, 1998, 4:40 pm, Room 314/315

Session: Dielectrics
Presenter: J.J. Chambers, North Carolina State University
Authors: J.J. Chambers, North Carolina State University
G. Lucovsky, North Carolina State University
G.N. Parsons, North Carolina State University
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High dielectric constant gate insulators will be needed to minimize gate tunneling in sub-100 nm integrated circuit devices. High k will allow the gate capacitance to scale with gate length without a significant reduction in gate dielectric thickness. Mixing SiO@sub 2@ with high k metal oxides (including Ti or Ta oxides) is expected to increase the dielectric constant without losing the beneficial properties of the Si/SiO@sub 2@ system. We have developed a rf plasma source capable of concurrent remote plasma CVD and separately controlled d.c. sputtering of metals. The motivation of this work is to establish an in-situ process for controlled silicon/high-k interface formation that will be stable during subsequent high-k dielectric deposition. Using an Ar plasma, Ta was sputtered for 1 to 10 minutes leading to controlled coverage onto a cleaned silicon surface. The Ta target was removed from the plasma zone, and the surface was exposed to a remote N@sub 2@O plasma for 10 minutes. After oxidation, XPS and AES were used to characterize Ta, Si and O bonding on the surface. XPS of the oxidized surface shows Ta 4f peaks at 28.4 and 30.3 eV indicative of Ta-O bonds. Si 2p peaks at 101.1 and 104.7 eV are also observed, indicating Si and Si-O bonding. As the surface coverage of tantalum increases, XPS of the oxidized surface shows the O 1s peak at 533.9 eV developing a shoulder at lower binding energy characteristic of O-Ta bonding. This data indicates, for the studied range of small tantalum surface coverage, that the tantalum is completely oxidized forming tantalum oxide and silicon oxide layers. Ellipsometry results indicate the oxide thickness is less than 20 Å. We will discuss the effect of initial Ta layer thickness on oxide formation, and experiments of co-deposition of metal and SiO@sub 2@ to form thin mixed metal oxide / silicon dioxide high dielectric constant films.