title: Ellipsometry and XPS comparative studies of thermal and plasma enhanced atomic layer deposited Al2O3-films.
abstract: We report on results on the preparation of thin (<100 nm) aluminum oxide (Al2O3) films on silicon substrates using thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) in the SENTECH SI ALD LL system. The T-ALD Al2O3 layers were deposited at 200 °C, for the PE-ALD films we varied the substrate temperature range between room temperature (rt) and 200 °C. We show data from spectroscopic ellipsometry (thickness, refractive index, growth rate) over 4" wafers and correlate them to X-ray photoelectron spectroscopy (XPS) results. The 200 °C T-ALD and PE-ALD processes yield films with similar refractive indices and with oxygen to aluminum elemental ratios very close to the stoichiometric value of 1.5. However, in both also fragments of the precursor are integrated into the film. The PE-ALD films show an increased growth rate and lower carbon contaminations. Reducing the deposition temperature down to rt leads to a higher content of carbon and CH-species. We also find a decrease of the refractive index and of the oxygen to aluminum elemental ratio as well as an increase of the growth rate whereas the homogeneity of the film growth is not influenced significantly. Initial state energy shifts in all PE-ALD samples are observed which we attribute to a net negative charge within the films.
authors.affiliation: Brandenburg Technical University, Applied Physics and Sensors, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Haeberle
authors.affiliation: Brandenburg Technical University, Applied Physics and Sensors, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Henkel
authors.affiliation: Sentech Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany.
authors.forename: Hassan
authors.initials: H
authors.lastname: Gargouri
authors.affiliation: Sentech Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Naumann
authors.affiliation: Sentech Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Gruska
authors.affiliation: Sentech Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Arens
authors.affiliation: Brandenburg Technical University, Applied Physics and Sensors, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany.
authors.forename: Massimo
authors.initials: M
authors.lastname: Tallarida
authors.affiliation: Brandenburg Technical University, Applied Physics and Sensors, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Schmeißer
keywords: ALD; Al2O3; PE-ALD; XPS; ellipsometry