Plasma Absorption Probe for Measuring Electron Density in an Environment Soiled with Processing Plasmas

Abstract

In this paper, we describe a novel and simple technique for measuring electron density using a plasma absorption probe (PAP). PAP enables us to measure the local absolute electron density even when the probe surface is soiled with processing plasmas. The technique relies on the resonant absorption of surface waves (SWs) excited in a “cavity” at the probe head. The PAP consists of a small antenna connected with a coaxial cable and is enclosed in a tube (dielectric constant ε) inserted in a plasma (electron plasma frequency ωp). A network analyzer feeds a rf signal to the antenna and displays the frequency dependence of the power absorption. A series of resonant absorptions are observed at frequencies slightly above the SW resonance frequency, ωSW = ωp/(1+ε)1/2, which allows us to determine the electron density. The measured electron densities are in good agreement with the data obtained by the plasma oscillation method.

Measurement of secondary electron emission coefficient of plane target in plasma immersion ion implantation

“…Figure 3 shows the time variation of (a) the full target current I t and (b) the secondary electron current I se at the silicon target. In this experiment, an argon plasma was produced at a discharge power of 600 W, and the electron density measured with the plasma absorption probe [11] was 1.8 × 10 11 cm -3…”

Discharge power dependence of Hα intensity and electron density of Ar+H2 discharges in H-assisted plasma CVD reactor

“…Electron density, n e , was measured at 17 mm above the center of the substrate electrode with a frequency shift probe [9] and a plasma absorption probe [10]. We employed these two probes; because our frequency shift probe worked well for n e ≤ 2 × 10 10 cm − 3 , while our plasma absorption probe worked well for n e ≥ 2 × 10 10 cm − 3 .…”

Study for plasma etching of dielectric film in semiconductor device manufacturing. Review of ASET research project

“…To evaluate the gas-phase physical parameters, probes [7], microwave interferometer [8], optical emission spectroscopy (OES) [9], and plasma absorption probe (PAP) [10] [11,12], laser-induced fluorescence spectroscopy (LIF) [13], OES, quadruple mass spectroscopy (QMS) [14,15], and actinometry [16,17] were utilized. Furthermore, incident flux was analyzed by QMS equipped with an ion flux energy analyzer (IFEA) [18].…”