A Source of Ultra-Low-Energy High Intensity Gaseous Ions Based on Discharge with Electron Injection

Abstract

Summary form only given. Biased target deposition is a promising sputtering technique for the fabrication of thin films and nano-structures requiring control of interfaces in multi-layer devices at the atomic level. One of the main requirements for this technique is an ion source that can produce several amperes of directed ion flux at kinetic energies of about ~20 eV or less. The maximum energy is given by the sputter threshold of materials present in the processing chamber. Closed-drift, anode-layer and end-Hall sources appeared to be adequate for some applications. However, recent experiments showed that they produce either too low ion current at low ion energy, or the ion energy became too high when large enough ion currents were achieved. Here we describe a novel version of an ultra-low-energy high-intensity ion source (which we dubbed "ULEHIIS") that can serve as possible alternative to Hall current ion sources. The ULEHIIS is based on a two-stage, low-pressure, high-current gaseous discharge. The first stage serves as an electron emitter to the second stage. The second stage, a non-self-sustained main discharge, provides acceleration of emitted electrons and ionization of the operating gas. With a discharge current of 35 A in argon, the maximum argon ion beam current on a target of 500 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was as high as 4.5 A, with the ion energy spread less than 10 eV