Role of low-energy electrons in Ar emission from low-pressure radio frequency discharge plasma

Abstract

Optical emission spectra from a low-pressure Ar plasma were studied with high spatial resolution. It has been shown that the intensity ratios of Ar lines excited through metastable levels to those excited directly from the ground state are sensitive to the shape of electron energy distribution function. From these measurements, important information on the spatial variation of plasma parameters can be obtained.

Mode transitions and hysteresis in inductively coupled plasmas

“…Note that the 811.5 nm emission can be affected by radiation trapping. 20 However, similar results were obtained using a weaker 800.6 nm line ͑not shown͒, which is known to be much less influenced by trapping.…”

“…Thus, the faster rise of the ratio just before the transition can be attributed to the growth of a low-energy fraction of plasma electrons, which can efficiently excite Ar metastables as the threshold is as low as 1.5 eV. 20 These electrons contribute to the increase of the Ar 811.5 nm line intensity but do not influence the Ar 750.4 nm line. In other words, this result indicates that the change of the EEDF shape from Druyvesteyn-like ͑flatter in the low-energy region͒ to Maxwellian-like starts before the mode transition, likely due to increasing ionization of metastables by low and medium energy electrons.…”

“…19 On the other hand, the 811.5 nm Ar emission is strongly influenced by the 1s 5 metastable state. 19,20 This line was used here for the diagnostic of metastables. As shown by Czerwiec and Graves 6 the metastable concentration can be calculated measuring the intensities I of the 750.4 and 811.5 nm Ar lines,…”

Silicon nitride etching in high- and low-density plasmas using SF6/O2/N2 mixtures

“…For actinometry, a 750 nm Ar line emission is widely used. 21 Actinometry is also routinely employed for characterization of atomic fluorine, and with less accuracy, of atomic oxygen and some other molecular and atomic species. The basic condition for actinometry is that both species are excited in the same way, i.e., by a single-step electron impact.…”

Observations of bi-Maxwellian and single Maxwellian electron energy distribution functions in a capacitively coupled radio-frequency plasmas by laser Thomson scattering

“…Similar results and conclusions have been obtained by other groups. [4][5][6][7][8] The bi-Maxwellian eedf also has been obtained during computer simulation and modeling studies of capacitively coupled rf discharges in argon and other gases. [9][10][11][12] Godyak and co-workers have stated that the limitations of the energy resolution and range of Langmuir probes make determination of low-energy electrons and detection of relatively high-energy electron tails difficult for some discharge conditions.…”