CONCENTRIC SPREAD PLASMA SOURCE

A new microwave plasma source termed ''concentric spread plasma (CSP)' ' is presented. By mounting an inner conductor of the coaxial waveguid e perpendicular to and directly on a quartz plate, the CSP source can generate a disk-shaped plasma (electron density >3.8 x 10(17) m(-3)) w ith high stability below the quartz plate that faces the wafers, regar dless of the process conditions. One of the notable features of the CS P source is the concentric expansion of the plasma with increasing mic rowave power. The CSP is generated by the following mechanism (process ): (1) the plasma itself becomes a part of the waveguide for microwave , (2) the microwaves are transmitted concentrically in the quartz plat e from its center toward its outer circumference, and (3) the CSP is g enerated by Joule heating caused by the surface current of the microwa ve flowing in the plasma. In short, the plasma is self-guided.