Y2O3 thin film was deposited by atomic layer deposition (ALD) with a new precursor yttrium tris(N,N‘-diisopropylacetamidinate), Y(iPr2amd)3, and water. The precursor was thermally stable and volatile
and had high reactivity with water. The growth rate of Y2O3 films was 0.8 Å/cycle over a wide temperature
range (150−280 °C). The films were very pure (C, N < 0.5 at. %) and had a refractive index of 1.8. The
films were smooth and had a cubic polycrystalline structure. High quality films were also deposited in
40:1 aspect ratio profiled substrates. Y2O3 films adsorbed water after air exposure because Rutherford
backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) showed an increased
oxygen ratio (O/Y > 1.5) and −OH bonds in air-exposed films. A relatively high permittivity (∼12), a
low leakage current density (<10-7 cm2 at 2 MV/cm) and high electrical breakdown field (∼5 MV/cm)
were measured for capacitors prepared from Al2O3 (10 Å)/Y2O3/n-Si structures. Uncapped Y2O3 films
showed flatband voltage shifts of 1 V and increased leakage current prior to annealing. ALD Y2O3 is a
promising dielectric for advanced electronic applications in nanoscale devices.
Lanthanum aluminum oxide thin films were grown by atomic layer deposition from a lanthanum precursor, tris(N,N′-diisopropylacetamidinato)lanthanum (La(iPrAMD)3), trimethylaluminum and water. Smooth, amorphous films having compositions La0.5Al1.5O3 and La0.9Al1.1O3 were deposited on HF-last silicon and characterized without postdeposition annealing. The films contained less than 1 at. % of carbon according to Rutherford backstattering spectrometry and secondary ion mass spectrometry. A thin (9.8 nm) film showed low leakage current (<5*10−8 A/cm2 at 1 V for an equivalent oxide thickness of 2.9 nm), flatband voltage of −0.1 V and low hysteresis (20 mV). Thicker films had even lower leakage currents (<10−8 A/cm2 at 2 MV/cm) but larger flatband shifts and more hysteresis. The permittivity of the films was 13 and the dielectric strength 4 MV/cm. Cross sectional high-resolution transmission electron microscopy showed a sharp interface between the film and the silicon substrate.
The surface pores of a porous low-k dielectric layer were sealed by a smooth coating of silica just a few nanometers thick. Atomic layer deposition ͑ALD͒ of tungsten nitride ͑WN͒ onto the smooth silica surface provided a very thin ͑1.5 nm͒ barrier to the diffusion of copper. Without the silica sealing layer, ALD WN penetrated through the low-k dielectric. Strong adhesion was demonstrated for the structure Si/porous dielectric/SiO 2 /WN/Co/Cu, in which the top four layers were formed by ALD. This structure is stable to at least 400°C and is suitable for making narrow interconnects for future microelectronics.
Praseodymium aluminum oxide (PAO) thin films were grown by atomic layer deposition (ALD) from a new precursor, tris(N,N′-diisopropylacetamidinato) praseodymium, (Pr(amd) 3 ), trimethylaluminum (TMA), and water. Smooth, amorphous films having varying compositions of the general formula Pr x Al 2-x O 3 were deposited on HF-last silicon and analyzed for physical and electrical characteristics. The films were pure according to Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS). The permittivity of the thin film with the stoichiometry of Pr 1.15 Al 0.85 O 3 was 18, and all annealed films displayed very low leakage currents compared to other high-k oxide films deposited using ALD. A leakage current density of 1.1 × 10 -4 A cm -2 was achieved for a PAO film with an equivalent oxide thickness of 1.46 nm. Annealed films also displayed nearly zero flat-band voltage shifts and low hysteresis (< 10 mV). The optimal growth parameters and electrical properties were achieved with Pr 1.15 Al 0.85 O 3 . Atomic force microscopy (AFM) determined that high temperature annealing (850°C) had no effect on the smoothness of the films (rms of 0.17 nm).
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