AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS1-TuM

Paper PS1-TuM1
Non-ambipolar Electron Plasma and its Physical Properties

Tuesday, October 29, 2013, 8:00 am, Room 102 B

Session: Plasma Sources
Presenter: L. Chen, Tokyo Electron America, Inc.
Authors: L. Chen, Tokyo Electron America, Inc.
Z.Y. Chen, Tokyo Electron America, Inc.
M. Funk, Tokyo Electron America, Inc.
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This report discloses a new type of plasma source: the Non-ambipolar Electron Plasma (NEP). Although, it is basically heated by electron beam, its power coupling and plasma physical property differentiate itself from the generic e––beam plasmas. Such differences open up potential applications that could have been difficult with the generic plasmas. The NEP system consists of two plasmas separated by a dielectric charged-species injector. Plasma-1 is the ground-referenced electron-source plasma (e.g., Ar) and it is an inductively coupled source (ICP) in this study for convenience reason. Plasma-2 is the NEP itself whose majority plasma-boundary is the DC-conductive accelerator with the remaining minority plasma-boundary being dielectric. NEP is typically molecular (e.g., N2) in the pressure range of 1-3 mtorr and its accelerator voltage varied from VA=+80 to VA=+600V. The NEP plasma potential (VP) is boundary-driven. Therefore, NEP VP tracks the accelerator voltage with its value just very slightly above VA. The current across the dielectric charged-species injector is non-ambipolar: only electrons are transported from ICP to NEP and only positive-ions are transported from NEP to ICP. The non-ambipolar electron-current injected into NEP is in the range of 10s Acm–2 with beam-energy ~ eVA and it heats NEP through beam-plasma instabilities. Its EEDf has a Maxwellian bulk followed by a broad energy-continuum connecting to the most energetic group with energies above the beam-energy. The remnant of the injected electron-beam power terminates at the NEP end-boundary floating-surface setting up sheath potentials from VS=80 to VS=580V in response to the applied values of VA. The floating-surface is bombarded by a space-charge neutral plasma-beam whose IEDf is near mono-energetic. When the injected electron-beam power is adequately damped by NEP, its end-boundary floating-surface VS can be linearly controlled at almost 1:1 ratio by VA. NEP does not have an electron-free sheath; its “sheath” is a widen presheath that consists of a thermal presheath followed by an “anisotropic” presheath, leading up to the end-boundary floating-surface. Its ion-current of the plasma-beam is much higher than what a conventional thermal presheath can supply. If the NEP parameters cannot damp the electron beam power sufficiently, VS will collapse and becomes irresponsive to VA.