Importance of Trimethylaluminum Diffusion in Three-Step ABC Molecular Layer Deposition Using Trimethylaluminum, Ethanolamine, and Maleic Anhydride

Abstract

Hybrid organic-inorganic films were grown by molecular layer deposition (MLD) with a three-step ABC reaction sequence using (A) trimethylaluminum (TMA), (B) ethanolamine (EA), and (C) maleic anhydride (MA) at 90 °C. Very large steady state mass gains of 1854-4220 ng/(cm(2) cycle) were measured depending on reaction conditions. These mass gains are much larger than typical mass gains for surface reactions. The quartz crystal microbalance (QCM) mass profiles during the TMA reaction were consistent with TMA diffusion into and out of the ABC films. The ABC mass gains per cycle also displayed a strong dependence on the TMA dose and purge times that was consistent with the effects of TMA diffusion. Multiple dose experiments conducted at 130 °C revealed that the ABC reactions were self-limiting for thin ABC films. For thicker ABC films, increased TMA diffusion into the ABC film led to non-self-limiting behavior. Numerical modeling assuming Fickian diffusion for TMA diffusing into and out of the ABC film could fit the QCM mass profiles. The results all indicate that TMA diffusion into the ABC MLD film plays a key role in the thin film growth. In addition, X-ray reflectivity (XRR) measurements revealed that the ABC films were exceptionally smooth.

Organic and inorganic–organic thin film structures by molecular layer deposition: A review

“…In later studies it was deduced that the growth process of the films is governed by the TMA diffusion into and out of the forming film, making the growth process strongly dependent on the TMA dose and purge times used. Also experiments carried out at 130 °C showed that the self-limiting growth could be only observed when the films remained thin [108]. According to nanointendation measurements conducted for the TMA+2-aminoethanol+furan-2,5-dione films deposited at 90 °C, the elastic modulus and Berkovich hardness were about 13 GPa and about 0.27 GPa, respectively [84].…”

Organic–Inorganic Thin Films from TiCl4 and 4‐Aminophenol Precursors: A Model Case of ALD/MLD Hybrid‐Material Growth?

“…Atomic layer deposition (ALD) is an advanced thin-film-deposition technique based on sequential surface-saturated deposition cycles, where each gaseous precursor pulse is separated by a purging pulse of inert gas. So far, hybrid thin films based on various metal alkoxides, [22][23][24][25][26][27][28][29][30][31][32] carboxylic acids, [33][34][35][36] and amines [33,[37][38][39] have been produced. We attribute the steady growth of the Ti-AP hybrid to the following facts: (1) the AP molecule is heterobifunctional and consists of a stiff aromatic backbone; moreover, (2) the -Cl ligands in TiCl 4 are small enough not to cause steric hindrance.…”

Hybrid nanomaterials through molecular and atomic layer deposition: Top down, bottom up, and in-between approaches to new materials

“…A three-step alucone process (ABC) was developed using TMA, ethanolamine (EA), and maleic anhydride (MA) further expanding the possibilities of available organic reactants 50,70 . The GPC was much higher than the two-step process but also highly dependent on the process temperature varying from 24 Å/cycle at 90°C down to 4 Å/cycle at 170°C.…”

“…For films grown at 130°C only a ~5% decrease in thickness after the first few days of growth was observed, a significant improvement over the two step process. 70 Carboxylic acids, such as benzoic, fumaric, and maleic acid, were also used as the organic component in the alucone process 71,72 . The GPC was dependent on the chosen carboxylic acid precursor as well as the temperature of the reaction varying from as high as 11.9 Å/cycle to 2.4 Å/cycle.…”