A low-frequency capacitively coupled radio-frequency (rf) discharge in Ar excited at 1.76 MHz is studied both experimentally and theoretically. Experimental measurements of electron concentration, discharge voltage and current are presented for a wide range of rf input powers. The rf current shape is nonsinusoidal, close to the triangle one. The evolution of Ar(2p1) emission excitation function in the interelectrode gap during an rf cycle is measured using the phase-resolved optical emission spectroscopy technique. Theoretical study is based on the particle-in-cell Monte Carlo collision numerical simulation. Specific dynamic features of the low-frequency discharge are discussed. The important role of secondary electrons in discharge maintenance and power balance is shown. This study is crucial for understanding dual-frequency discharges with a corresponding value of low frequency.

This work is devoted to the study of the possibility of obtaining the highest O2(a 1Δg) yield in ED SOG at the high absolute O2(a 1Δg) concentration needed for developing a powerful oxygen–iodine laser pumped by electric discharge. A singlet oxygen was produced in a transversal rf discharge in the pressure range 10–30 Torr of pure oxygen in the small-diameter (7 mm) quartz tube with HgO coating of the inner walls for removing atomic oxygen to eliminate fast O2(a 1Δg) quenching. It is shown that pd scaling (p—pressure, d—tube diameter) of the rf discharge actually allows an increase of the absolute O2(a 1Δg) density. The increase in the rf frequency from 13.56 to 81 MHz results in the essential increase of the O2(a 1Δg) yield (beyond 15% at such a high oxygen pressure as 15 Torr), but the subsequent transfer to the higher rf frequency of 160 MHz only slightly influences the maximally obtained O2(a 1Δg) yield. The effect of the NO admixture on the O2(a 1Δg) production has been also studied. The rate constant of O2(a 1Δg) quenching by was directly measured. The NO admixture (up to 20%) resulted in the noticeable increase in the O2(a 1Δg) yield mainly at low energy inputs. But this gain in the O2(a 1Δg) concentration drops with increasing energy input. Nevertheless it is shown that by combining the O2 + NO mixture with the HgO coating of the discharge tube walls one can provide the O2(a 1Δg) yield on the level of ∼21% at 10 Torr, ∼17% at 20 Torr and ∼13% at 30 Torr of O2 with the efficiency of ∼4–6%. The analysis of the NO admixture influence on the discharge structure and O2(a 1Δg) production has been carried out by using the 2D model. It was found that at the low energy input the NO admixture acts as an easily ionized species that enlarges the region occupied by plasma. Thus, in the O2 + NO discharge the normal current density is lower than in the pure oxygen discharge. As a result a higher energetic efficiency of O2(a 1Δg) production is also observed in the case of the O2 + NO mixture and the low energy input. In order to provide the optimal conditions for O2(a 1Δg) production (with regard to the yield and efficiency) in the continuous wave transversal VHF discharge at such high oxygen pressures as of 10–30 Torr it is necessary to find out the range of energy inputs where the VHF discharge operates in the regime of normal current density on the boundary with the abnormal regime and to remove atomic oxygen produced in the discharge by some volume or surface processes.

Degradation of chemical composition of porous low-k films under extreme and various vacuum ultraviolet emissions is studied using specially developed sources. It is shown that the most significant damage is induced by Xe line emission (147 nm) in comparison with Ar (106 nm), He (58 nm), and Sn (13.5 nm) emissions. No direct damage was detected for 193 nm emission. Photoabsorption cross-sections and photodissociation quantum yields were derived for four films under study. 147 nm photons penetrate deeply into low-k films due to smaller photoabsorption cross-section and still have sufficient energy to excite Si-O-Si matrix and break Si-CH3 bonds.

No abstract