Abstract

This work presents a simple design of surface wave plasma (SWP) source based on cylindrical cavity excited by ∼ 850 MHz ultra high frequency (UHF) wave. The cavity equipped with four rectangular slots demonstrates the usefulness of a large aperture coupling for plasma generation using top-wall excitation. The UHF power is coupled to the plasma through an upper dielectric wall placed at the open end of a coaxial transmission line that is short-circuited at the other end to construct a coaxial transmission line resonator. Using high-frequency microwave simulation the structure of the cylindrical cavity and the slots are designed and fabricated. Numerous plasma diagnostic methods are used to study the plasma characteristics and the mechanism of surface wave (SW) plasma generation. The plasma generation capability of the source is investigated at various operating pressures and UHF powers. It is seen that reasonably radial uniform plasmas with a very high plasma density ∼ 1011 cm-3 can be produced by a wide variation of pressures from 10 mTorr to 180 mTorr. Further, the usefulness of this UHF plasma source for large area plasma application is realized.

Highlights

  • During the past decades, the necessity for the ultra-large scale integration and fabrication of planar display panel makes the demand of novel plasma sources

  • Surface-wave plasmas (SWPs) produced by microwaves at 2.45 GHz or lower microwave frequency ∼ 915 MHz in the absence of a magnetic field have several advantages.[23,24,25,26,27,28]. They may be listed as (i) simpler design structure and lower cost compared to other sources, (ii) no inner electrode in the discharge, so the plasma will not be polluted by the electrode as in capacitively coupled plasma (CCP) discharges, (iii) it is easier to get a high-density plasma above the cutoff density, (iv) generation of more active radicals in surface wave plasma (SWP) than in CCPs with similar densities that are crucial in application on aCorresponding authors’ emails: bibhutisahu@gmail.com, hanjg@skku.edu

  • The present study presents a unique and simple prototype SWP source consisting of a cylindrical dielectric cavity driven by ∼ 850 MHz ultra high frequency (UHF) wave, which is powered by a coaxial line resonator

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Summary

INTRODUCTION

The necessity for the ultra-large scale integration and fabrication of planar display panel makes the demand of novel plasma sources. Several works on the design and development of the novel large area plasmas for plasma applications utilizing 915 MHz UHF waves are reported by various groups.[27,28,29,30,31,32,33,34] In most these sources, the plasma uniformity below the dielectric slab is one of the most crucial factors; in these designs, a lot of trials or empirical methods have repeatedly been used to achieve preferable uniformity. Nie et al.[37] and Wu et al.[38] have reported SWP sources using a cylindrical Teflon rod as a dielectric waveguide and studied the standing wave mode of the surface wave Along with these works, there are other interesting studies, which suggest that a possible way of efficient surface wave (SW) discharge control is to use the plasma-dielectric resonator that is to apply slot antennas on it.[39,40].

Design of the cavity resonator plasma source
UHF power source
CST microwave studio high-frequency simulation
Plasma diagnostics
Low-power test experiment
High-power experiments
CONCLUSION

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