Langmuir Probe Diagnostics of Inductively Coupled Plasma Generated Using Flat Spiral Antenna

Abstract

Langmuir probe (LP) diagnostics is performed on an inductively coupled plasma (ICP) generated using a flat spiral antenna. The current–voltage ( $I - V$ ) characteristics are measured using a radio frequency (RF) compensated LP to mitigate the effect of RF distortion in $I - V$ measurements. All-important plasma parameters such as electron density ( $n_{\mathrm {e}}$ ), electron temperature ( $T_{\mathrm {e}}$ ), plasma potential ( $V_{\mathrm {p}}$ ), and electron energy distribution function (EEDF) are measured in a cylindrical-shaped ICP. The plasma is generated by feeding RF (13.56 MHz) current in the planer multiple spiral antennas. It is seen that the plasma is uniform over an area with 200 mm diameter, with an electron number density in the range from $\sim 10^{11}$ to 1012 cm−3. Typically for plasma processing of materials, the required density fall in that region. Variation of plasma parameters is investigated as a function of applied RF power and operating pressure and the observed results are discussed.