Time-Resolved Electron Density Measurement Characterization of E-H Modes for Inductively Coupled Plasma Instabilities

Inductively Coupled Plasma sources driven by RF power at low pressure regimes are well adopted for high-volume manufacturing of semiconductor devices. The vexing challenge to the utility of these plasma processing reactors is the existence of the E-H mode transition1. Industry notably avoids the process region associated with this transition, where plasma instabilities prohibit reliable RF power delivery. The plasma instability is associated with a hysteresis in coupled RF power (current) varying for the E-Mode, or weakly capacitive coupling to the plasma, in comparison to the stronger current coupling in the H-Mode, where inductive coupling is preferentially dominant. As a result, approximately two orders of magnitude of electron density is relinquished in this transition region from serving industrial manufacturing processes. We characterize the plasma parameter variation through the E to H-mode with a time-resolved measurement of the electron density. Electropositive and electronegative chemistries are incorporated into our experimental setup. The experimental scheme serves to evaluate RF power delivery and ameliorate its coupling through the transition region. The work is further extended to adopt more efficient power coupling to toroidal plasma sources.