Nonlinear electrical phenomena in the GEC reference cell and in industrial reactors

Abstract

The initial interlaboratory comparison of Reference-Cell plasmas emphasized rf voltage and current measurements. Plasma properties were found to be dependent on rf circuit impedances at harmonics of the 13.56-MHz excitation frequency as well as on power, pressure, etc. The dependence was due to the nonlinear interaction of the plasma with the rf generator, cables, and matching network. This finding led to studies of performance problems common to industrial etching reactors. Electrical diagnostics and methodologies that had been developed with the Reference Cell were applied to the production problems. The authors developed understanding of and control over subharmonic generation and they developed cures for chamber-to-chamber variability in etch rate and dc bias.