Extraction and neutralization of positive and negative ions from a pulsed electronegative inductively coupled plasma

Abstract

Almost electron-free (ion-ion) plasmas can be transiently formed during the afterglow phase of pulsed plasmas in electronegative gases. In ion-ion plasmas, both positive and negative ions can be extracted which makes them advantageous for a number of applications. In this paper, we investigate the extraction and acceleration of positive and negative ion beams from a pulsed inductively coupled plasma in SF 6 . The plasma is bounded by two electrodes biased synchronously with the discharge modulation. It is shown that when a DC bias voltage is applied during the afterglow phase, positive/negative ions are accelerated in a positive/ negative space charge sheath formed in front of one of the electrodes. The energy of extracted ions closely follows the amplitude of the applied bias voltage (25-150 V) and the peak beam current density reaches 2 A m −2 . With a view to using the described system as a source of energetic neutral beams for low damage material processing, simultaneous extraction and surface neutralization of positive and negative ions using an extraction electrode with high aspect ratio apertures is investigated.

Alternative solutions to caesium in negative-ion sources: a study of negative-ion surface production on diamond in H2/D2 plasmas

“…Negativeoxygen-ion sources for secondary ion mass spectrometry operate by volume production. While plasma thrusters for space propulsion [14][15][16] and microelectronics etching plasmas [17][18][19][20][21][22] currently rely on volume production, they may also benefit in future from utilising surface production.…”

Negative-ion surface production in hydrogen plasmas: Determination of the negative-ion energy and angle distribution function using mass spectrometry

“…Negative-ion (NI) production in low-pressure plasma has many applications and is studied in various areas, such as microelectronics 1,2,3,4,5,6 , magnetically confined fusion 7,8 , space propulsion 9,10,11 and sources for particle accelerators 12,13,14 . NI in low pressure plasmas are usually created by dissociative attachment of electrons on molecules (volume production) 15,16,17 , but they can also be created on surfaces by the bombardment of positive ions or hyperthermal neutrals 18,19,20,21,22,23,24 .…”

“…NI in low pressure plasmas are usually created by dissociative attachment of electrons on molecules (volume production) 15,16,17 , but they can also be created on surfaces by the bombardment of positive ions or hyperthermal neutrals 18,19,20,21,22,23,24 . Volume-produced NI sources are mainly used in microelectronic 1,2,3,4,5,6 and space propulsion applications 9,10,11 while surface production of NI is employed in magnetically confined fusion devices 7,8 and sources for particle accelerators 12,13,14 . Surface production of negative-ions is also observed in sputtering processes as shown in 25,26,27. In magnetically-confined fusion devices (tokamaks), NI can be used to generate a fast neutral beam through interaction with a stripping gas target; such beam is used to heat the plasma and to implement the current drive.…”

Reconstruction of energy and angle distribution function of surface-emitted negative ions in hydrogen plasmas using mass spectrometry

“…Negative-ions (NI) can be created in low-pressure plasmas either by dissociative attachment of electrons on molecules in the volume [1,2] or by conversion of positive ions or hyperthermal neutrals on the surface immersed into plasma [3,4]. Volume production of NI is widely applied in microelectronics industry [5] and space propulsion engines [6,7], while the surface production mechanism is essential in NI sources for magnetically confined fusion reactors [8,9] and particle accelerators [10,11]. NI can be also formed on the target surface as a byproduct during the reactive magnetron sputtering [12].…”