| AVS 55th International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF+NC-MoM |
| Session: | ALD of Hybrid Materials and ALD on 3D Nanostructures |
| Presenter: | D. Seghete, University of Colorado at Boulder |
| Authors: | D. Seghete, University of Colorado at Boulder B. Yoon, University of Colorado at Boulder A.S. Cavanagh, University of Colorado at Boulder S.M. George, University of Colorado at Boulder |
| Correspondent: | Click to Email |
Molecular layer deposition (MLD) can produce organic or hybrid organic-inorganic films. Current MLD schemes usually employ two homobifunctional monomers as reactants. This approach presents practical difficulties because the homobifunctional monomer can react with two chemical functional groups on the surface. These "double" reactions can remove the active surface species and reduce the MLD growth rate. Homobifunctional reactants can be avoided by using ring-opening and heterobifunctional reactants. The ring-opening reactants prevent double reactions by containing a concealed functionality that only expresses itself upon reaction. The heterobifunctional reactants have two chemical functional groups that are different. These precursors react only monofunctionally with the surface to avert double reactions and growth termination. In this study, we report a three-step MLD process that involves trimethylaluminum (an inorganic trifunctional reactant), ethanolamine (a heterobifunctional reactant), and maleic anhydride (a ring-opening reactant). The extension to three-step ABC MLD processes expands the variety of reactants and compositional diversity that can be achieved for MLD. In this three-step process, trimethylaluminum (TMA) reacts with carboxylic acid species (-COOH) to deposit -AlCH3 species. The -AlCH3 species then react preferentially with the hydroxyl end of ethanolamine (EA) to form a surface terminated with -NH2 species. Maleic anhydride (MA) then reacts with these amine species and undergoes a ring-opening reaction to produce carboxylic acid (-COOH) species. The TMA can then react again with the carboxylic acid species to repeat the ABC cycle. In situ Fourier transform infrared spectroscopy and quartz crystal microbalance measurements were employed to monitor the surface reactions and measure the mass changes at temperatures from 80-150 ºC. Ex situ x-ray reflectivity (XRR) confirmed the linear growth of the MLD films versus number of ABC cycles. The growth rates decreased with increasing temperature from 23 Å per ABC cycle at 90 ºC to 8 Å per ABC cycle at 150 ºC. The XRR scans also established the low surface roughness, uniform composition and low density of the MLD films.