AVS 65th International Symposium & Exhibition
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThA

Paper PS-ThA1
In-situ Measurement of Electron Emission and Electron Reflection Yields

Thursday, October 25, 2018, 2:20 pm, Room 104A

Session: Plasma Diagnostics, Sensors and Controls
Presenter: Mark Sobolewski, National Institute of Standards and Technology (NIST)
Correspondent: Click to Email
Bombardment of plasma-exposed surfaces by energetic particles causes electrons to be emitted, which in turn influence the plasma. Accurate plasma simulations require knowledge of the flux or yield of emitted electrons. Yields can be measured directly in beam studies, but it is impractical to produce a beam of each possible energetic particle produced by typical plasmas. In contrast, in-situ measurements, performed during plasma exposure, provide useful values for effective or total electron emission yields, summed over all the energetic particles present for given plasma conditions. Here, measurements were performed at 5-10 mTorr in a radio-frequency (rf) biased, inductively coupled plasma (icp) system. The rf voltage and current across the sheath adjacent to the rf-biased electrode are measured, along with Langmuir probe measurements of ion current density and electron temperature. The measurements are analyzed by a numerical sheath model, which allows the current of electrons emitted from the surface to be distinguished from other mechanisms of current flow. An insulating cap placed on the rf-biased electrode exposes a small, off-center portion of its area. The cap, combined with the azimuthal electric field generated by the icp source, allows outgoing, emitted electrons to be distinguished from electrons reflected at the counterelectrode surface. Thus we obtain values for the total yield or flux of electrons emitted at the rf-biased surface and the reflection coefficient at the counterelectrode. The technique is validated by comparing measurements made in argon discharges with literature results and then is applied to characterize yields at practical surfaces in inert gas plasmas and fluorocarbon etching plasmas.