Mode transition in magnetic pole enhanced inductively coupled argon plasmas
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The electrical probe (Langmuir probe) diagnostics of different plasma parameters and operation regimes (E/H modes) of magnetic pole enhanced, inductively coupled (MaPE-ICP) argon plasmas are investigated. It is shown that uniform, high density (n e ∼ 1012 cm-3) and low electron temperature (T e ∼ 1.5 eV) plasma can be produced in low pressure argon discharges at a low power (100 W). It is found that an MaPE-ICP reactor operates in two different modes; capacitive (E mode) and inductive (H mode). No density jump or hysteresis are reported between these modes. The effect of pressure on transition power, where the mode changes from E to H mode at 20 sccm gas flow rate are studied and it is found that for all pressures tested (∼7.5 mTorr to 75 mTorr) the transition power remains same. In the inductive mode, the above plasma parameters show a smooth variation with increasing filling gas pressure at fixed power. The intensity of the emission line at 750.4 nm due to 2p 1 → 1s 2 (Paschen’s notation) transition, closely follows the variation of n e with RF power and filling gas pressure. Measured electron energy probability function (EEPF) shows that electron occupation mostly changes in the high-energy tail, which enlightens close similarity of the 750.4 nm argon line to electron number density (n e ). The behaviour of the electron energy probability function (EEPF) with regard to pressure and RF power in two operational modes is presented.
- 6.S.V. Singh, Ph.D. dissertation, Ruhr University Bochum, 2005, www.ub.rub.de
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