Al2O3 films were deposited by atomic layer deposition (ALD) at temperatures as low as 33 °C in a viscous-flow reactor using alternating exposures of Al(CH3)3 (trimethylaluminum [TMA]) and H2O. Low-temperature Al2O3 ALD films have the potential to coat thermally fragile substrates such as organic, polymeric, or biological materials. The properties of low-temperature Al2O3 ALD films were investigated versus growth temperature by depositing films on Si(100) substrates and quartz crystal microbalance (QCM) sensors. Al2O3 film thicknesses, growth rates, densities, and optical properties were determined using surface profilometry, atomic force microscopy (AFM), QCM, and spectroscopic ellipsometry. Al2O3 film densities were lower at lower deposition temperatures. Al2O3 ALD film densities were 3.0 g/cm3 at 177 °C and 2.5 g/cm3 at 33 °C. AFM images showed that Al2O3 ALD films grown at low temperatures were very smooth with a root-mean-squared (RMS) roughness of only 4 ± 1 Å. Current−voltage and capacitance−voltage measurements showed good electrical properties of the low-temperature Al2O3 ALD films. Elemental analysis of the films using forward recoil spectrometry revealed hydrogen concentrations that increased with decreasing growth temperature. No other elements were observed by Rutherford backscattering spectrometry except the parent aluminum and oxygen concentrations. Low-temperature Al2O3 ALD at 58 °C was demonstrated for the first time on a poly(ethylene terephthalate) (PET) polymeric substrate. Al2O3 ALD coatings on PET bottles resulted in reduced CO2 gas permeabilities.

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Atomic layer deposition and magnetron sputter deposition were used to synthesize thin-film multilayers of W/Al(2)O(3). With individual layers only a few nanometers thick, the high interface density produced a strong impediment to heat transfer, giving rise to a thermal conductivity of approximately 0.6 watts per meter per kelvin. This result suggests that high densities of interfaces between dissimilar materials may provide a route for the production of thermal barriers with ultra-low thermal conductivity.

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Articles you may be interested inNucleation and growth of ZnO on PMMA by low-temperature atomic layer deposition J. Vac. Sci. Technol. A 33, 01A128 (2015); 10.1116/1.4902326 X-ray reflectivity characterization of atomic layer deposition Al2O3/TiO2 nanolaminates with ultrathin bilayers J. Vac. Sci. Technol. A 32, 01A111 (2014); 10.1116/1.4833556Trimethyl-aluminum and ozone interactions with graphite in atomic layer deposition of Al2O3Initial nucleation and growth of atomic layer deposited Hf O 2 gate dielectric layers on Si surfaces with the various surface conditions using in situ medium energy ion scattering analysis Nucleation phenomena are critical for the fabrication of W / Al 2 O 3 nanolaminates using atomic layer deposition ͑ALD͒ techniques. The nucleation and growth of W ALD on hydroxylated Al 2 O 3 ALD surfaces and Al 2 O 3 ALD on fluorinated W ALD surfaces was studied using in situ quartz crystal microbalance ͑QCM͒ and ex situ atomic force microscope ͑AFM͒ techniques. The QCM investigations revealed that Al 2 O 3 ALD readily nucleated on the fluorinated W surface and displayed "substrate-enhanced growth." In contrast, W ALD required 4-10 ALD cycles to nucleate on the hydroxylated Al 2 O 3 surface and displayed "substrate-inhibited growth." The W ALD nucleation period was shorter for higher Si 2 H 6 and WF 6 reactant exposures. The most rapid nucleation of W ALD on the Al 2 O 3 surface occurred with much larger Si 2 H 6 and WF 6 exposures on the initial ALD cycle with the WF 6 exposure prior to the Si 2 H 6 exposure. By analyzing the individual Si 2 H 6 and WF 6 mass gain per cycle ͑MGPC͒, three main regions were identified in the W ALD nucleation and growth: initial deposition on Al 2 O 3 , W island growth and coalescence, and steady state growth. The root mean square ͑rms͒ roughness of the resulting W ALD film was dependent on the Si 2 H 6 exposures and the number of ALD cycles required to nucleate the W ALD. A linear dependence was observed between the rms roughness and the number of ALD cycles required to reach one-half the maximum W MGPC. The W ALD also displayed very periodic oscillations in the W MGPC that were consistent with island nucleation and growth. Four local minima and three local maxima were observed in the W MGPC versus the number of ALD cycles. Comparing the results for W ALD on Al 2 O 3 surfaces with recent simulations of ALD nucleation helps to establish the relationship between the nucleation period and surface roughness with island growth during nucleation.