IEDF distortion in high voltage retarding field energy analyzers

There is a need for IEDF measurement at increasingly high voltages in the kV range, particularly (but not limited to) the characterization of industrial systems that rely on high energy ions to achieve desired process conditions for material removal, deposition, or modification. Field variation, surface charge accumulation, and space charge formation within an RFEA diagnostic can limit the energy resolution of the sensor and in some cases provide distorted IEDF's when typical first derivative analysis of the sensor's VI characteristic is employed. Design considerations for an RFEA capable of operation in a capacitive RF system with sheath voltages in the kV range are presented, and show how IEDF energy resolution is impacted through design considerations such as grid geometry, spacing, and between-grid channel design. Space charge induced IEDF distortion when employing VI differentiation techniques will be presented. Specifically, distortion of the low energy portion of an IEDF due to space charge effects as well as pathways for resolving this distortion phenomenon through data analysis will be presented.