ABSTRACT: The hexagonal phase of La <sub>2</sub> O <sub>3</sub> is obtained upon vacuum annealing of hydroxilated La <sub>2</sub> O <sub>3</sub> films grown with atomic layer deposition at 200 ° C using La (<sup> i </sup> P rCp )<sub>3</sub> and O <sub>3</sub> . A dielectric constant value of 24±2 and 22±1 is obtained on Si-based and Ge-based metal-oxide-semiconductor capacitors, respectively. However, the relatively good La <sub>2</sub> O <sub>3</sub> dielectric properties are associated with significant interface reactivity on both semiconductor substrates. This leads to the identification of a minimum critical thickness that limits the scaling down of the equivalent oxide thickness of the stack. These findings are explained by the spontaneous formation of lanthanum silicate and germanate species which takes place during the growth and also upon annealing. Although the ultimate film thickness scalability remains an unsolved concern, the use of an O <sub>3</sub> -based process is demonstrated to be a suitable solution to fabricate La <sub>2</sub> O <sub>3</sub> films that can be successfully converted into the high- k hexagonal phase.
Journal of Applied Physics 11/2010; · 2.17 Impact Factor
ABSTRACT: X-ray diffraction and infrared spectroscopy measurements are conducted in order to assess the crystallographic structure and chemical purity of lanthanum oxide ( La <sub>2</sub> O <sub>3</sub>) films grown by atomic layer deposition (ALD) on Si substrates. In situ capping with thin aluminum oxide ( Al <sub>2</sub> O <sub>3</sub>) layer is proved to be beneficial in preventing the formation of lanthanum hydroxide phases. The effect of two process parameters, namely, La <sub>2</sub> O <sub>3</sub> film growth temperature ( 260–500 ° C range) and postdeposition annealing temperature ( 600–1100 ° C range), on the chemical and structural evolutions of Al <sub>2</sub> O <sub>3</sub>/ La <sub>2</sub> O <sub>3</sub>/ Si stacks is discussed. This study enables the identification of the optimum ALD growth recipe yielding the highest hexagonal La <sub>2</sub> O <sub>3</sub> phase content, which might be suitable for integration into innovative metal oxide semiconductor devices.
Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 04/2009; · 1.25 Impact Factor
ABSTRACT: Atomic layer deposition (ALD) has received increasing attention in relation to the growth of high-permittivity
rare-earth oxides for advanced gate stack applications. Transistor reliability strongly depends on the oxide/semiconductor
interface properties. In this study, we perform transmission electron microscopy measurements in the high-resolution mode
coupled with electron energy loss spectroscopy experiments to probe at the nanometric scale interface layer (IL) issues for
stacks. Complementary results from electrical and X-ray diffraction measurements on selected samples are also discussed.
We demonstrate that the
film reactivity with the Si surface can be controlled up to a certain extent by appropriately choosing the ALD precursor
combination. In particular, we prove that the
scheme is more attractive than the
one for depositing
films because it gives rise to a lower IL thickness and interface trap density and to a smaller critical sample thickness
for the stabilization of the high-κ hexagonal
Journal of The Electrochemical Society. 12/2008; 156(1):H1-H6.
ABSTRACT: La2O3 films are obtained by annealing in vacuum La(OH)3 layers produced upon air exposure of La2O3 layers grown using atomic layer deposition. Sample thickness determines whether hexagonal or cubic La2O3 form. The observed infrared active phonon mode with minimum frequency for hexagonal La2O3 films is located at 198 cm−1, in good agreement with the first principles calculations, and at a lower frequency than the corresponding mode for cubic La2O3 is at 235 cm−1. Accordingly, electrical measurements reveal a dielectric constant around 27 for hexagonal La2O3 films, significantly higher than the one around 17 derived for cubic La2O3 layers.
Applied Physics Letters 09/2007; 91(10):102901-102901-3. · 3.84 Impact Factor