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Scaling of ultraviolet photon formation in low pressure plasmas: implications for microelectronics and sterilisation processes

ORAL · Invited

Abstract

Low pressure plasmas are widely used in microelectronics processing and are actively researched for surface sterilisation. To understand and optimise plasma sources for these applications, the fluxes of reactive neutrals and ions to surfaces are often a key focus. However, ultraviolet (UV) photons are known to be important for surface damage in microelectronics processing, and as drivers of microorganism inactivation during sterilisation studies. Nevertheless, they typically receive less attention than ions and neutrals. In this work, UV formation in inductively coupled plasma sources operated in oxygen and nitrogen containing mixtures is studied using both numerical modelling and experimental measurements.

In nitrogen/oxygen plasmas, UV emission is found to mainly originate from excited states of NO. Across the E-H mode transition, UV emission intensity and the NO ground state density, as measured by laser induced fluorescence, are found to be decoupled. This offers opportunities for optimising processes where NO fluxes to surfaces are beneficial, but UV fluxes should be avoided. An experimentally informed collisional radiative model for UV emission from the NO(A) state is developed and used to explain the measured trends. Here, it is found that NO(A) formation is dominated by collisions with excited nitrogen, specifically N2(A).

In argon/oxygen plasmas, vacuum UV (VUV) photon formation from excited O atoms is studied using a newly developed zero-dimensional (0-D) simulation framework, including a collisional radiative model. Simulations demonstrate that the relative flux of VUV photons compared with O atoms and positive ions can be tailored over orders of magnitude by varying pressure and power in the system, offering insights into regimes of operation where photon related surface damage can be minimised for microelectronics processing. Simulations also suggest that control of flux ratios can also be achieved through pulsing of the power input to the plasma, offering further insights into optimum process regimes.

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Publication: L. Schücke et al 2025 Plasma Sources Sci. Technol. 34 045015<br>M. Osca Engelbrecht et al 2024 Plasma Sources Sci. Technol. 33 095008

Presenters

  • Andrew R Gibson

    York Plasma Institute, School of Physics, Engineering and Technology, University of York, United Kingdom, University of York, Ruhr University Bochum, York Plasma Institute, School of Physics, Engineering and Technology, University of York

Authors

  • Andrew R Gibson

    York Plasma Institute, School of Physics, Engineering and Technology, University of York, United Kingdom, University of York, Ruhr University Bochum, York Plasma Institute, School of Physics, Engineering and Technology, University of York

  • Michel Osca Engelbrecht

    York Plasma Institute, School of Physics, Engineering and Technology, University of York

  • Theo Carpenter

    York Plasma Institute, School of Physics, Engineering and Technology, University of York

  • Lars Schücke

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University Bochum, Germany, Ruhr University Bochum

  • Angie Natalia Torres Segura

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University, Bochum, Germany

  • Jonathan Jenderny

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University, Bochum, Germany

  • Henrik Hylla

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University, Bochum, Germany

  • Dominik Filla

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University, Bochum, Germany, ​Chair of Applied Electrodynamics and Plasma Technology, Ruhr University, Bochum, Germany

  • Nikita Bibinov

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University Bochum, Germany, Ruhr University Bochum

  • Ihor Korolov

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University Bochum, Bochum, Germany, Chair of Applied Electrodynamics and Plasma Technology, Ruhr University Bochum, Germany

  • Peter Awakowicz

    Chair of Applied Electrodynamics and Plasma Technology, Ruhr University Bochum, Germany

  • Christopher P Ridgers

    York Plasma Institute, School of Physics, Engineering and Technology, University of York