Crystalline 1D Coordination Polymer Inhibitor Layer Leads to Vertical Sidewalls in Selectively Deposited ZnO on Nanoscale Patterns

Area-selective atomic layer deposition (AS-ALD) is a promising technique for the fabrication of next generation nanoelectronics. There are two main challenges in AS-ALD: (1) achieving high selectivity of deposition on the growth regions and (2) preventing mushrooming of the growth material onto the nongrowth regions and achieving well-defined interfaces. In this work, we use benzenethiol (BT) as an inhibitor in the selective deposition of ZnO on SiO2 in the presence of copper with and without a native oxide (Cu/CuOx). We observe that BT forms a monolayer on the Cu surface and a Cu-thiolate multilayer structure on CuOx. Using grazing incidence x-ray diffraction combined with simulations, we find that the multilayer structure is crystalline and composed of 1D coordination polymers of Cu-thiolate. Using ellipsometry and x-ray photoelectron spectroscopy, we show that the BT consumes the entirety of the CuOx present in forming the multilayer, and thus the thickness of the multilayer can be tuned by the thickness of the original oxide. Both the monolayer BT and the multilayer BT prove to be effective inhibitors of ZnO ALD, blocking nearly 500 ALD cycles, which is more than twice that achieved with other thiol inhibitors. Finally, we demonstrate that the multilayer structure can prevent mushrooming of the ALD material onto the nongrowth surface of nanoscale patterns, creating vertical sidewalls with welldefined material interfaces and providing excellent pattern transfer even for a relatively thick deposited film. As such, these results demonstrate not only that BT is an effective inhibitor, but also that its ability to form tunable multilayers lends itself towards highly precise nanopatterning applications.