Oxford Instruments Plasma Technology Ltd.

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.

The research on superconducting circuits for quantum information technologies progressively extends from the academic world towards the industry.Material sciences therefore become an essential lever for the development of technologies based on such circuits as they allow finding industry-compatible routes of improvements.In this context, we propose a study on the behavior of the niobium nitride (NbN), one of the most commonly used material for these devices, when exposed to strong magnetic fields.To this aim, the properties of NbN layers with the same composition but different microstructures, tuned by changing the deposition method, are compared.This study aims to establish interdependencies between the microstructure of the material and its behavior once exposed to a magnetic field.X-ray diffraction and Hall-effect characterizations are used to assess that the microstructure is significantly modified by the choice of the deposition technique.Pushing further these investigations also allowed to quantify and compare the level of disorder in both cases by extracting the Ioffe-regel and the Ginzburg-Landau parameters from characterizations of the superconducting transition temperature for several magnetic field amplitudes.This was used to conclude that in highly disordered NbN layers, the microstructure heterogeneities are responsible for a strong electron localization allowing to significantly enhance the resilience of their superconducting state under strong magnetic fields.

This work provides evidence that plasma-assisted atomic layer deposition (ALD) of SiO2, a widely applied process and a cornerstone in self-aligned multiple patterning, is strongly influenced by ions even under mild plasma conditions with low-energy ions. In two complementary experimental approaches, the plasma ALD of SiO2 is investigated with and without the contribution of ions. The first set of experiments is based on microscopic cavity structures, where part of the growth surface is shielded from ions by a suspended membrane. It is observed that a lower growth per cycle (GPC) and a better material quality are obtained when an ion contribution is present. Without any ion contribution, a GPC of 1.45 ± 0.15 Å/cycle and a wet etch rate of 4 ± 1 nm/s (in 30:1 buffered HF) are obtained for a deposition temperature of 200 °C. With an ion contribution, these values decrease, where the magnitude of the decrease appears to be determined by the supplied ion energy dose. For extended ion doses, the GPC decreases to 0.85 ± 0.05 Å/cycle and the wet etch rate to 0.44 ± 0.09 nm/s, approaching the value for a thermal oxide. The important role of ions is confirmed by the second experimental approach, which is based on ion-selective quartz crystal microbalance measurements. By these results, it is demonstrated that ions have a stronger impact on the plasma ALD of SiO2 than usually considered, providing essential insights for tailoring the film growth.