LaAlO 3 films sputter-deposited on Si were submitted to rapid thermal annealing at 800 and 1000°C. Atomic transport and chemical changes were investigated using ion beam analysis and X-ray photoelectron spectroscopy. Annealing induced La and Al losses or their migration into a newly formed interfacial layer and Si migration into the film. The mechanism of Si incorporation into the film is influenced by the annealing atmosphere. These instabilities were hampered by a thermal nitridation in NH 3 at 700°C performed prior to rapid thermal annealing, indicating a possible route for producing a thermally stable La-based highgate dielectric.Several different materials holding dielectric constants substantially higher than that of SiO x N y ͑3.8 Ͻ Ͻ 7.8͒ were proposed as alternatives for gate dielectric in next generations of metal-oxidesemiconductor field effect transistors ͑MOSFET͒. 1-3 These materials, usually called high-dielectrics, must withstand all manufacturing steps of MOSFET technology, including those performed at temperatures much higher than that used during the high-film deposition. One critical thermal step is dopant activation, usually accomplished by rapid thermal annealing ͑RTA͒ at 1050°C. 1-3 This step may modify structurally and chemically the films, having deleterious consequences in the electrical characteristics of the formed MOS capacitors. Lanthanum aluminate is a potential candidate for gate dielectric due to its wide band gap ͑5.6 eV͒ and high dielectric constant ͑ = 20-25͒ as compared to SiO x N y . 3-5 Besides, it is predicted to be thermodynamically stable on Si. 6 However, some unexpected physical instabilities, such as metal migration into the substrate, substrate-Si migration into the high-film, as well as chemical reaction leading to the formation of a lanthanum ͑alumi-no͒silicate interfacial layer were recently observed. 7,8 In this paper, we systematically investigate atomic transport and chemical reactions that take place in lanthanum aluminate films on Si following RTA in controlled atmospheres. ExperimentalLaAlO films were sputter-deposited on HF last p-type Si͑100͒, using a LaAlO 3 ceramic target in a 5 ϫ 10 −2 mbar Ar plasma excited by a 13.56 MHz radio frequency with a power density of 1 W/cm 2 . Ex situ post-deposition RTA was performed in vacuum ͑ϳ10 −7 mbar͒ or in 10 mbar of O 2 . Annealing times varied with respect to the temperature of treatments: 60 s for 800°C and 20 s for 1000°C. The quantities of La and O in the films were determined by Rutherford backscattering spectroscopy ͑RBS͒, 9,10 while Al quantification by nuclear reaction analysis ͑NRA͒. 11,12 The results are expressed in areal densities units ͓͑at. cm −2 ͔͒, which correspond to the integral of the atomic densities ͓͑at. cm −3 ͔͒ over the film thickness. The sensitivities of RBS and NRA for these elements are better than 5 ϫ 10 14 cm −2 . 9,11 A selected sample was thermally nitrided at 700°C during 30 min in 20 mbar of NH 3 enriched to 10% in the 15 N isotope. Following nitridation, the sample was submitted to ...

High resolution medium energy ion scattering analysis for the quantitative depth profiling of ultrathin high-k layers J.

The effects on metal transport and loss in Hf and La aluminate films deposited on Si induced by rapid thermal annealing at 1000°C were investigated. Decomposition of HfAlO films on Si during rapid thermal annealing was reveled by the decrease of the Hf and Al contents. Metal loss from LaAlO/Si structures was also observed following annealing in vacuum, while strong metal transport and interfacial reaction were induced by annealing in a O2 containing atmosphere. These instabilities were hampered by means of post deposition thermal nitridation in NH3 at temperatures lower than 1000°C performed before the rapid thermal annealing step. The role of nitridation is discussed in terms of the N profiles in the nitrided structures.

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