Electron Free Plasma : From Being to Becoming

📗 Electronegative plasmas produced by attaching mobile low energy electrons to create heavy negative ions are very attractive for both fundamental research and plasma processing applications. Electronegative gas plasmas are widely used in microelectronics manufacturing for etching and deposition of thin films. For example, plasmas in gases containing Cl2 or SF6 are used for silicon etching, fluorocarbon plasmas are indispensable for silicon dioxide etching, and oxygen plasmas are used for ashing of photoresist and other polymers. Electronegative plasmas produced in argon and sulfur hexafluoride (SF6) are used to etch silicon, silicon nitride, silicon carbide and titanium carbide with high etch rates and without film residues. Highly electronegative discharges, also called ion-ion plasmas are seen as a promising solution for electric propulsion and neutral beam development. Ion-ion plasmas find application in charge-free semiconductor manufacturing, negative ion sources, and the D-layer of the upper atmosphere. .Here based on CUSP type magntic filter, a source of an almost electron free plasma along with all possible mechanism of negative ion production is discussed.