Area-Selective Atomic Layer Deposition through Selective Passivation of SiO₂ with a SF₆/H₂ Plasma

Area-selective atomic layer deposition (ALD) has gained widespread interest in the semiconductor industry to facilitate the continued drive for more powerful and efficient devices. In this work, we chemically passivate SiO₂ with a single SF₆/H₂/Ar plasma pretreatment to selectively deposit TiO₂ on ZnO, HfO₂, or Al₂O₃, using tetrakis-(dimethylamido)-titanium (TDMAT) and H₂O. The SF₆/(H₂ + SF₆) flow ratio was tuned to suppress the etching of SiO₂ while the nucleation delay of TiO₂ ALD was maximized. A plasma with an SF₆/(SF₆ + H₂) ratio of 0.24 etched less than 1 Å and gave the longest nucleation delay at a substrate temperature of 150 °C. After this pretreatment, 2.1, 2.0, and 1.6 nm of TiO₂ can be deposited with a selectivity of 90% with respect to a SiO₂ nongrowth area on HfO₂, Al₂O₃, or ZnO respectively. In-situ reflection absorption infrared spectroscopy (RAIRS) measurements show that during the SF₆/H₂/Ar plasma, Si-OH and Si-H surface groups are replaced by Si-F groups, suggesting that full chemical passivation of SiO₂ is achieved. The reaction of TDMAT with a F-terminated SiO₂ surface is shown to be unfavorable using density functional theory (DFT) calculations. Furthermore, RAIRS measurements and DFT simulations show that after the plasma treatment, precursors do react on fluorinated Al₂O₃. Taken together, the results of this study show that using a plasma pretreatment for chemical passivation of the nongrowth area provides interesting opportunities for future ASD processes.