Large-area plasma produced by surface waves on a metal wall with periodic grooves

Large-area (> 40 cm in diam) high-density (similar to 10(12)) plasmas are p roduced by 2.45 GHz microwave discharge, usually under a large dielectric p late which is needed to excite surface waves propagating along the plasma-d ielectric interface. However, such a dielectric plate is often unfavorable in practical applications. This article reports a technique for producing s urface wave plasmas, in a metal vessel without using such a dielectric plat e. When the microwave is injected from slot antennas without a dielectric p late, the plasma is locally generated around the slots with relatively low densities even at high incident powers. This problem is solved by introduci ng periodic grooves in a flat metal wall, which dramatically improve the pl asma uniformity and increase the electron density as high as the dielectric plate case. The dispersion relation and surface impedance are compared bet ween the dielectric wall case and the metal wall case, while the periodic g roove effect is treated in an equivalent circuit model and physically expla ined. (C) 2001 American Vacuum Society.