Ion implantation into semiconductors: studying a new manufacturing technique

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This project will use atom probe tomography (APT) to study ion implantation into semiconductors with a new manufacturing and characterisation technique based on ionic liquid beams.Ionic liquids are mixtures of cations and anions without an intervening solvent. An Ionic Liquid Ion Source (ILIS) is a device in which the liquid covers a sharpened needle. The needle is subjected to electric fields to produce an ion beam. The resulting beam can be used to treat materials.ILIS provide a large variety of ion chemistries, including organic molecules, simple atomic halogens, and heavily fluorinated species. Fast etching of silicon has been demonstrated after ILIS irradiation, thanks to the reactivity of fluorinated species in the beam [1]. ILIS can be used for manufacturing (e.g. microelectronics fabrication) and in advanced characterisation of materials. The ILIS beam could be focused and used to mill materials at the nanoscale, enabling tomography or the preparation of samples for transmission electron microscopy. ILIS could also be used to perform secondary ion mass spectrometry.This project will study the implantation of ILIS ions into semiconductors, which should be understood if ILIS is used in manufacturing or characterisation. APT allows analysis of materials in three dimensions with sub-nanometer resolution, and has been used previously to study ion implantation [2]. APT will be used to profile the sub-surface chemical composition of ILIS-irradiated samples. Commercially available silicon pillars will be treated with a variety of ILIS beams. The pillars will then be shaped into atom probes using focused ion beam, and APT will be used to determine the implantation depths of chemical species contained in the ion beam. This work should further develop APT as an implantation characterisation technique.[1] C Perez-Martinez et al., J. Vac. Sci. Technol. B 28 (2010) L25[2] K Eder et al., Ultramicroscopy 228 (2021) 113334