Development and plasma characterization of an 850 MHz surface-wave plasma source

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.