Two-dimensional ion velocity distribution functions in inductively coupled argon plasma

Abstract

Two-dimensional ion velocity distribution functions (IVDFs) of argon plasmas have been measured with optical tomography via laser-induced fluorescence (LIF). An inductive radio-frequency (RF) coil created the plasmas, and IVDFs were measured versus RF frequency, gas pressure and location (bulk plasma or presheath of a plate). Typical gas pressure was 0.3-0.4 mTorr, RF power 25 W and magnetic field 130 G. Effective perpendicular ion temperature decreased with increasing RF frequency, and changed little with pressure. Optical tomography reveals features of the presheath IVDF that cannot be deduced from LIF scans parallel and perpendicular to the plate alone. Progress also has been made toward performing optical tomography on a commercial ion beam source (Veeco/Ion Tech 3 cm RF Ion Source, Model #201). In particular, it has been discovered that the beam energy fluctuates in a range of about 20 eV over the timescale of a few minutes.

Laser-induced fluorescence ion diagnostics in light of plasma processing

“…For the conditions of Fig. 2d in [7] we see in Fig. 4 the velocity spread of the ion distribution function in the sheath.…”

“…The ion temperature inside an RF source is anisotropic due to the polarization of the rf fields, see Fig. 3a of [7]. The directional dependence of ion temperature in an rf source ranges from 0.1 eV parallel to the acceleration direction to 0.4 eV in the perpendicular.…”

Determination of Plasma Flow Velocity by Mach Probe and Triple Probe with Correction by Laser-Induced Fluorescence in Unmagnetized Plasmas

“…With background plasmas, from the measurement of the current densities with the MP, the velocity of plasmas with the ion beams is determined using eq. (12), in which we have used two calibration factors of k: k ¼ 1:32 as an average of kinetic and PIC models, and 1.66 as the calibrated one by LIF method when there is no ion beam. These calculated ones (or indirectly measured using LIF) and deduced ones (or measured using the MP) with two values of k are shown in Fig.…”

2-dimensional ion velocity distributions measured by laser-induced fluorescence above a radio-frequency biased silicon wafer

“…Several studies have investigated IVDs in the presheath. These have been done over unbiased surfaces, [28][29][30][31] dc biased surfaces, 32,33 and in rf sheaths. 34 measured both longitudinal and transverse IVDs in both the presheath and sheath above a floating plate in a multipolar dc discharge.…”