Section Days abstract book 2010.indd - RUB Research School ...

NSE_26
LOW TEMPERATURE H2O-ASSISTED ALD OF
CRYSTALLINE Gd2O3 THIN FILMS
Ke Xu, Andrian P. Milanov, Harish Parala, Apurba Laha, Ranjith Ramadurai,
Eberhard Bugiel, H. Jörg Osten, Roland A. Fischer and Anjana Devi
Inorganic Materials Chemistry Group
Ruhr-University Bochum, 44780, Bochum, Germany
email: cocoxuke@hotmail.de
In this work, the water-assisted ALD growth of Gd2O3 thin films using the homoleptic
gadolinium guanidinate precursor [Gd{( i PrN)2CNMe2}3] 1 , referred to as [Gd(DPDMG)3] is
investigated. With this precursor, surface controlled, self-limiting ALD-type growth with a
growth rate of ~ 1.1 Å/cycle was observed within a broad temperature window of 175 –
275°C on Si(100) substrates (Fig.1a). The self-limiting character of the film growth was also
verified (Figure 1b). The as-deposited Gd2O3 films were polycrystalline as revealed by
HRTEM and XRD analysis.
Figure 1. Gd2O3 growth rate as a function of (a) the deposition temperature and (b) the [Gd(DPDMG) 3] pulse
time. Inset: dependence of the Gd2O3 film thickness on the number of deposition cycles at 225 °C for the
[Gd(DPDMG)3]/H2O process. Right: HRTEM cross sectional images of Gd2O3/Si grown at 225°C.
In summary, Gd2O3 thin films of superior structural quality with very low leakage current
were deposited with growth rates of 1.1 Å/cycle in a surface controlled, self-limiting ALD
process. The superior performance of [Gd(DPDMG)3] is attributed to the increased basicity of
the guanidinato ligand relative to thd, which facilitates a fast and selective reaction with the
OH surface functionalities and the adsorbed water. On the basis of the electrical
characterization, it appears that the Gd2O3 films could be potential candidates for the
replacement of SiO2-based gate dielectrics in future CMOS devices. The key to success was
the use of a tailored all-nitrogen coordinated tris-guanidinato-Gd precursor that combines
several advantageous properties, including high and selective reactivity towards water at low
temperatures.