Molecular Layer Deposition of Aluminum Alkoxide Polymer Films Using Trimethylaluminum and Glycidol

Abstract

Molecular layer deposition (MLD) of aluminum alkoxide polymer films was examined using trimethlyaluminum (TMA) and glycidol (GLY) as the reactants. Glycidol is a high vapor pressure heterobifunctional reactant with both hydroxyl and epoxy chemical functionalites. These two different functionalities help avoid "double reactions" that are common with homobifuctional reactants. A variety of techniques, including in situ Fourier transform infrared (FTIR) spectroscopy and quartz crystal microbalance (QCM) measurements, were employed to study the film growth. FTIR measurements at 100 and 125 °C observed the selective reaction of the GLY hydroxyl group with the AlCH(3) surface species during GLY exposure. Epoxy ring-opening and methyl transfer from TMA to the surface epoxy species were then monitored during TMA exposure. This epoxy ring-opening reaction is dependent on strong Lewis acid-base interactions between aluminum and oxygen. The QCM experiments observed linear growth with self-limiting surface reactions at 100-175 °C under certain growth conditions. With a sufficient purge time of 20 s after TMA and GLY exposures at 125 °C, the mass gain per cycle (MGPC) was 19.8 ng/cm(2)-cycle. The individual mass gains after the TMA and GLY exposures were also consistent with a TMA/GLY stoichiometry of 4:3 in the MLD film. This TMA/GLY stoichiometry suggests the presence of Al(2)O(2) dimeric core species. The MLD films resulting from these TMA and GLY exposures also evolved with annealing temperature to form thinner conformal porous films with increased density. Non-self-limiting growth was a problem at shorter purge times and lower temperatures. With shorter purge times of 10 s at 125 °C, the MPGC increased dramatically to 134 ng/cm(2)-cycle. The individual mass gains after the TMA and GLY exposures in the CVD regime were consistent with a TMA/GLY stoichiometry of 1:1. The MGPC decreased progressively versus purge time. This behavior was attributed to the removal of reactants that could lead to CVD and the instability of the surface species after the reactant exposures. These results reveal that the TMA and GLY reaction displays much complexity and must be carefully controlled to be a useful MLD process.

Atomic Layer Deposition of LiF and Lithium Ion Conducting (AlF3)(LiF)x Alloys Using Trimethylaluminum, Lithium Hexamethyldisilazide and Hydrogen Fluoride

“…This ratio can be used to determine the surface chemistry from the calculation using molar mass of each species. 33 This ratio of 5.6 will be discussed later. FSi(CH3)3 between HMDS, (CH3)3SiNHSi(CH3)3, and F -in the gas phase was previously studied in the tube reactor with He flow by mass spectrometry.…”

“…The ALD reactions were performed in the viscous flow reactor equipped with an in situ quartz crystal microbalance (QCM) and a quadrupole mass spectrometer (QMS) at temperatures between 125°C and 250°C 32,33 Quadrupole mass spectrometry (QMS) was performed on the vapor phase species in the ALD reactor. Measurements were performed with a residual gas analyzer (RGA 200, Stanford…”

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

“…The various difficulties encountered when using organic precursors are discussed in detail in a review by George et al [24]. Several strategies have been employed to improve the controllability of the growth process, such as using organic precursors with stiff backbones [13–14 32–37] or with two different functional groups [36–39], using reactions requiring surface activation [10,39–46], using precursors in which ring-opening reactions occur [47], or using three different precursors instead of two [48–49]. …”

“…When metal precursors are combined with alcohols or phenols, the resultant material is often called “metalcone” [27]. Most of the research has been focused on the aluminum-based alucones [12–13 15–16 38–39 81–97], but also zincones [13,33,38–39 46,51–52 56,94–95 98–103], titanicones [53,55,95,104–105], and zircones [54,87] have been studied. The schematic structure of ideally growing TMA+ethane-1,2-diol, DEZ+benzene-1,4-diol and TMA+oxiran-2-ylmethanol hybrid films are shown in Fig.…”

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

“…A heterobifunctional allyl alcohol, glycidol, was also used as the organic component in such a reaction 73 . Again the GPC was highly dependent on both the temperature and the purge times with a rather stable value of 1.3 Å/cycle at 125°C.…”