Beam-generated plasmas for processing applications

Abstract

The use of moderate energy electron beams (e-beams) to generate plasma can provide greater control and larger area than existing techniques for processing applications. Kilovolt energy electrons have the ability to efficiently ionize low pressure neutral gas nearly independent of composition. This results in a low-temperature, high-density plasma of nearly controllable composition generated in the beam channel. By confining the electron beam magnetically the plasma generation region can be designated independent of surrounding structures. Particle fluxes to surfaces can then be controlled by the beam and gas parameters, system geometry, and the externally applied rf bias. The Large Area Plasma Processing System (LAPPS) utilizes a 1–5 kV, 2–10 mA/cm2 sheet beam of electrons to generate a 1011–1012 cm−3 density, 1 eV electron temperature plasma. Plasma sheets of up to 60×60 cm2 area have been generated in a variety of molecular and atomic gases using both pulsed and cw e-beam sources. The theoretical basis for the plasma production and decay is presented along with experiments measuring the plasma density, temperature, and potential. Particle fluxes to nearby surfaces are measured along with the effects of radio frequency biasing. The LAPPS source is found to generate large-area plasmas suitable for materials processing.

Enhancement mechanism of H- production and suitable configurations for materials processing in a magnetized sheet plasma

“…For the case of argon seeding, the proportion of argon to the total gas feed is fixed at 10%, the mixture that was earlier found to generate the optimum H − current. 5 The plasma discharge current (I d ) at the extraction region was varied. The effective electron density (N e ) and effective electron temperature (T eff ) are greatly affected by the increase in discharge current.…”

“…Plasma generation of hydrogen negative ions (H − ) is motivated by their use in accelerators for charge exchange injection, fusion plasma heating and diagnostics, and in semiconductor applications for etching and material surface treatment. Magnetized thin sheet plasmas have been developed to generate large-area plasma processing systems [1][2][3][4][5] and large-area H − source. 6 The magnetized sheet plasma negative ion source (MSPNIS) [7][8][9][10][11] developed in this work dispenses with the physical requirement of a driver region.…”

Surface treatment by the ion flow from electron beam generated plasma in the forevacuum pressure range

“…The ribbon electron beam was produced by a forevacuum plasma electron source [18]. The source was specially designed for ribbon beam generating while transmission without traditionally used [15,19,20] longitudinal magnetic field. The source represented a three-electrode system -hollow cathode 1, flat anode 2 and extractor 3 (Fig.…”

“…Special structure of accelerating space [18] enables to obtain electron beam without traditionally used transmitting magnetic field. As described in [18,19], plasma ion flows can compensate for the negative charge transmitted to the target in the process of electron beam treatment. It is obvious that such compensation is possible in case of plasma ion flow treatment due to higher mobility of plasma electron component.…”

Computer simulation of the sheath and the adjacent plasma in the presence of a plasma source

“…The characteristics of beam excited plasmas were studied experimentally for cylindrical [19,20] and plane [21] geometries. In both cases a rather definite localization of the plasma region was shown, remote from the walls, in spite of the large mean free path of ions relative to the lateral dimension of the plasma chamber.…”