Optical function of atomic layer deposited alumina (0.5–41.0 nm) from 191 to 1688 nm by spectroscopic ellipsometry with brief literature review

Abstract

Atomic layer deposition (ALD) is widely used in the semiconductor industry to provide atomic level control over film thicknesses and layer conformality. Here, the authors report the thermal (332 °C) ALD of thin amorphous alumina films (0.5–41.0 nm) deposited using water and trimethylaluminum precursors. Alumina deposition was optimized by varying the dose and purge times for both precursors with an eye toward obtaining uniform film thicknesses and constant growth per cycle. Films were characterized by x-ray photoelectron spectroscopy and spectroscopic ellipsometry (from 191 to 1688 nm). The subsequent workup of the SE data was based on a multisample analysis. It considered Cauchy and Sellmeier functions and accounted for surface roughness. This modeling yielded an optical function for ALD alumina over the measured wavelength range. The authors recommend the optical function determined from the Sellmeier model.

Flow-Through Atmospheric Pressure-Atomic Layer Deposition Reactor for Thin-Film Deposition in Capillary Columns

“…Accordingly, the D TMA and D water valves were opened for 0.020 and 0.015 s, respectively, for dosing these precursors. However, we purged the system longer than in traditional ALD: the purge time was 45 s in each half cycle (3 times longer than in our previous ALD procedure) . Thus, our initial ALD process can be depicted as TMA/N 2 /H 2 O/N 2 : 0.020:45:0.015:45 s. After 100 of these cycles, ca.…”

“…The parameters for this process were based on those in a previous report in which we determined the optical function of Al 2 O 3 deposited by ALD. 11 Accordingly, the D TMA and D water valves were opened for 0.020 and 0.015 s, respectively, for dosing these precursors. However, we purged the system longer than in traditional ALD: the purge time was 45 s in each half cycle (3 times longer than in our previous ALD procedure).…”

“…We validated our AP-ALD system with the well-known TMA–water ALD reaction, which produces Al 2 O 3 . ,,, This process was first conducted on silicon shards in the witness chambers without a capillary between them. The parameters for this process were based on those in a previous report in which we determined the optical function of Al 2 O 3 deposited by ALD . Accordingly, the D TMA and D water valves were opened for 0.020 and 0.015 s, respectively, for dosing these precursors.…”

“…ALD often provides conformality, nondirectionality, and pinhole-free, uniform coatings, ,, where most ALD precursors have relatively high vapor pressures, which allow them to be easily transported into the reaction chamber. ALD is used to deposit a wide range of materials, including metal oxides, − metal nitrides, metal sulfides, reduced metals, and other nontraditional materials. ,, Applications of ALD include thin-film coatings in semiconductor devices, energy storage devices, solar panels, and photocatalyst synthesis. ,, In some cases, ALD processes are advantageous because they allow materials to be deposited at lower temperatures, including for the passivation of various electronic devices, thermally sensitive polymer coatings, coatings on biomaterials, and thin films for medicines and medical devices. − To date, ALD has not been extensively explored for chromatography; there are a few reports of the use of ALD to prepare/modify thin-layer chromatography plates − and semipacked microfabricated columns , and also to coat LC and GC components…”

A new holder/container with a porous cover for atomic layer deposition on particles, with transport analysis and detailed characterization of the resulting materials

“…Some of us recently published a detailed description of this procedure 42 . The alumina and zinc oxide films were smooth, that is, the roughness predicted by SE was less than 0.1 nm; the addition of a roughness layer in our models did not substantially improve the mean squared error (MSE) of the fits, so it was omitted 55 . Indeed, the MSE values for this modeling of the alumina and zinc oxide films were less than 1.0, which suggests high‐quality fits.…”