Atomic scale characterization of HfO2∕Al2O3 thin films grown on nitrided and oxidized Si substrates

One and three bilayers of HfO2(9Å)∕Al2O3(3Å) thin films were grown by atomic layer chemical-vapor deposition on Si(001) substrates whose surfaces were nitrided or oxidized. The films as-grown and postannealed in an ultrahigh vacuum were analyzed by atomic force microscopy, photoelectron spectroscopy...

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Veröffentlicht in:Journal of applied physics 2004-12, Vol.96 (11), p.6113-6119
Hauptverfasser: Nishimura, T., Okazawa, T., Hoshino, Y., Kido, Y., Iwamoto, K., Tominaga, K., Nabatame, T., Yasuda, T., Toriumi, A.
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Sprache:eng
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Zusammenfassung:One and three bilayers of HfO2(9Å)∕Al2O3(3Å) thin films were grown by atomic layer chemical-vapor deposition on Si(001) substrates whose surfaces were nitrided or oxidized. The films as-grown and postannealed in an ultrahigh vacuum were analyzed by atomic force microscopy, photoelectron spectroscopy, and medium energy ion scattering. For the one- and three-bilayer films grown on the nitrided Si substrates, the HfO2 and Al2O3 layers are mixed to form Hf aluminates at temperatures above 600°C. The mixed Hf aluminate layer is partly decomposed into HfO2 and Al2O3 grains and Al2O3 segregates to the surface by postannealing at 900°C. Complete decomposition takes place at 1000°C and the surface is covered with Al2O3. The surfaces are uniform and almost flat up to 900°C but are considerably roughened at 1000°C due to the complete decomposition of the Hf aluminate layer. In contrast, for one- bilayer films stacked on the oxidized Si substrates, Hf silicate layers, including Hf aluminate, are formed by annealing at 600–800°C. At temperatures above 900°C, HfSi2 grows and Al oxide escapes from the surface.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1808245