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Communication Dans Un Congrès Année : 2021

Atomic layer etching of Gallium Nitride (GaN) using SF6 and Ar plasmas

Résumé

The excellent electrical properties of Gallium Nitride (GaN) make it a promising semiconductor for the next generation of high-power devices, in particular the normally-off High Electron Mobility Transistors (HEMTs). Among the different etching processes, Atomic Layer Etching (ALE) of GaN is the most advantageous. It enables accurate control of the etched depth and provides less damage compared to monocyclic plasma etching process for the fabrication of GaN electronic components. Up to now and due to the high volatility of the etch by-products, notably GaCl3 1,2, the majority of the research activity carried out on GaN ALE has been performed using chlorine based chemistry for the modification step. Furthermore, fluorinated chemistries have been unequally studied. For example, Nakazawa et al used a CF4/O2/Ar plasma mixture to etch GaN 3 and Johnson et al studied XeF2 molecules in the modification step of a thermal ALE process 4. In this work, the GaN ALE process consists of cyclic SF6 plasma chemisorption step and Ar plasma removal step. The fluorine-based plasma, enables to form a GaF3 layer at the surface. This non-volatile etch by-product has a boiling point as high as 1000 °C at atmospheric pressure 5. The GaF3 modified layer is then removed during the removal step which consists of Ar plasma with a low ion bombardment to prevent any sputtering of the substrate. Self-Limiting Etching (SLE) can be achieved under such conditions. Experiments were performed in an Inductively Coupled Plasma (ICP) reactor. This study investigates the influence of plasma parameters such as gas flow rates and the self-bias voltage. The exposure duration of ALE steps has been also investigated. AFM was used to measure the etch depth and the surface roughness. Our first analyses show that GaN Etched depth Per Cycle (EPC) increases slowly with the SF6 exposure time. After 100 cycles, a low etch per cycle of 0.1 nm/cycle was obtained, corresponding to a less than a monolayer of GaN. Thanks/Acknowledgement The authors are grateful to the European Union (IPCEI) Nano2022 project and Région Centre for their financial supporting. Most equipment is provided by CERTeM 2020 platform. References 1. Ohba, T et al, Jpn. J. Appl. Phys. 56, 06HB06, 2017 2. Le Roux, F et al, Microelectron. Eng. 8, 2020 3. Nakazawa, K et al, DPS, 2019 4. Johnson, N. R et al, Appl. Phys. Lett. 114, 243103, 2019 5. Pearton, S. J et al, J. Appl. Phys. 86, 1–78, 1999
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hal-03539383 , version 1 (21-01-2022)

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  • HAL Id : hal-03539383 , version 1

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Lamiae Hamraoui, Thomas Tillocher, Philippe Lefaucheux, Remi Dussart, Mohamed Boufnichel. Atomic layer etching of Gallium Nitride (GaN) using SF6 and Ar plasmas. PLATHINIUM (Plasma Thin film International Union Meeting) 2021, Sep 2021, Antibes, France. ⟨hal-03539383⟩
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