In this contribution, results will be presented based on recently developed direct-write ALD approaches for two relevant metal oxides: In2O3:H, and ZnO. The method exploits the difference in nucleation delay on OH- and H-terminated Si surfaces. As shown in Figure 1, direct-write ALD can be achieved by locally activating an H-terminated Si starting surface using an O2-fed µ-plasma printer or by electron beam induced deposition (EBID) of a SiO2 seed layer. This allows to define OH-rich regions with dimensions ranging from a few microns (µ-plasma) down to tens of nanometers (EBID). Therefore, high-quality materials provided by ALD can be combined with the patterning capabilities of direct-write techniques to obtain patterns in a bottom-up approach.
The area-selective characteristics for these two different processes was probed by X-ray photoelectron spectroscopy and electron dispersive X-ray spectroscopy for micro- and nanoscale patterns, respectively. As shown in Figure 2, in-situ spectroscopic ellipsometry was used to investigate the nucleation behaviours of the ALD processes on the growth and non-growth surfaces. Finally, the key reasons for the selectivity have been unveiled using density functional theory (DFT) simulations.
1. Mameli, A. et al. Area-Selective Atomic Layer Deposition of In2O3:H Using a µ-Plasma Printer for Local Area Activation. Chem. Mater. 29, 921–925 (2017)
2. Longo, R. C. et al. Toward Atomic-Scale Patterned Atomic Layer Deposition: Reactions of Al2O3 Precursors on a Si(001) Surface with Mixed Functionalizations. J. Phys. Chem. C 120, 2628–2641 (2016)