Properties of a differential pressure pseudospark device

A differential pressure pseudospark device is developed to produce a discharge at a pressure of 10-4mbar near the anode. This pressure range is two orders in magnitude lower than conventional pseudospark devices. In this device a pressure gradient is maintained between the cathode and the anode by providing a gas flow through the discharge column. The pressure gradient helps in shifting the Paschen curve more towards the left in comparison to the conventional case. The empirical relationship V∞ (p2dD)-2, valid without a gas flow, is not applicable when the pressure difference between the cathode and the anode is over two orders in magnitude. Self-biasing collector technique reveals the presence of energetic electrons (0.4-1.2 keV) present in the plasma downstream of the anode. The nature of this plasma at two distinct pressure ranges of operation of the device shows marked difference in properties. A qualitative discussion is presented that explains the possible discharge mechanism in this device

Application of Resonance Microwave Probes as Electron Density Sensors

A concept of measuring local electron density in weakly magnetized plasma based on quarter wave resonator was introduced by Stenzel in 1976. In the recent years, the technique has attracted noticeable interest for diagnosing industrial plasmas. The resonance probes, also popularly known as hairpin probe (HP) because of its characteristic shape, have been successfully applied in many industrial plasma systems including deposition plasmas and dual radio-frequency operated confined CCP discharge. The principle is based on supporting a standing wave that corresponds to the plasma permittivity in the near field region around the resonator. The above probing technique has the advantage over microwave interferometer because they are capable of providing local measurement of electron density. One important application of resonance microwave probe is its capability of providing spontaneous response to the change in dielectric medium around the probe head. This unique property can therefore be employed as a sensor for monitoring the plasma during long-pulse operation in industrial plasma tools. In this paper we describe the underlying principle behind the resonance hairpin prove and finally introduce the concept of split-ring-resonator as a possible substitute for plasma surface diagnostics. The split-ring-resonator (SRR) is unique in the sense that it can be mounted on the wall of the plasma chamber therefore it is less perturbing to the plasma. Additionally the diagnostics can provide useful information about the state of plasma adjacent to the substrate during dielectric etching and plasma deposition treatments. A comparative study of SEE with the conventional hairpin probe applied in a magnetized linear plasma device is presented and its prospective role as a diagnostic sensor is discussed

Application of Resonance Microwave Probes as Electron Density Sensors

A concept of measuring local electron density in weakly magnetized plasma based on quarter wave resonator was introduced by Stenzel in 1976. In the recent years, the technique has attracted noticeable interest for diagnosing industrial plasmas. The resonance probes, also popularly known as hairpin probe (HP) because of its characteristic shape, have been successfully applied in many industrial plasma systems including deposition plasmas and dual radio-frequency operated confined CCP discharge. The principle is based on supporting a standing wave that corresponds to the plasma permittivity in the near field region around the resonator. The above probing technique has the advantage over microwave interferometer because they are capable of providing local measurement of electron density. One important application of resonance microwave probe is its capability of providing spontaneous response to the change in dielectric medium around the probe head. This unique property can therefore be employed as a sensor for monitoring the plasma during long-pulse operation in industrial plasma tools. In this paper we describe the underlying principle behind the resonance hairpin prove and finally introduce the concept of split-ring-resonator as a possible substitute for plasma surface diagnostics. The split-ring-resonator (SRR) is unique in the sense that it can be mounted on the wall of the plasma chamber therefore it is less perturbing to the plasma. Additionally the diagnostics can provide useful information about the state of plasma adjacent to the substrate during dielectric etching and plasma deposition treatments. A comparative study of SEE with the conventional hairpin probe applied in a magnetized linear plasma device is presented and its prospective role as a diagnostic sensor is discussed

Influence of substrate conditions on the temporal behaviour of plasma parameters in a pulsed dc magnetron discharge

Using time-resolved optical emission spectroscopy and Langmuir probing, the effect of substrate bias (and the absence of the substrate) on the energetics and concentrations of the plasma species at different phases of the pulse have been investigated in a bi-polar unbalanced pulsed dc magnetron. The discharge was operated in a range of frequencies, 25–100 kHz, and duty cycles, 60–90%, at a constant Ar pressure of 0.66 Pa. In the presence of an electrically grounded substrate at the transition from discharge on to off (when the plasma potential is raised to values over +150 V relative to ground), we have detected a short-lived burst in optical emissions from transitions in Ar and Ti (of duration 200 ns) in the plasma bulk. We also detect an associated elevation in the effective electron temperature measured with the Langmuir probe (Teff> twice that during the rest of the cycle). This phenomenon, we believe, is due to the liberation and increased confinement of electrons emanating from the substrate due to local ion bombardment. With an electrically floating substrate there is a much weaker associated optical flash, and none in the absence of the substrate. The Langmuir probe results also show that in the on phases of the pulse, a general increase in effective electron temperature and density is observed with decreasing frequency and duty cycle, i.e. increased reverse times. The implications of the observed transient bulk heating of electrons on the pulsed sputter deposition process are briefly discussed