Ion Sources for Ion Beam Assisted Thin Film Deposmon
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THIN FILM DEPOSITION IGOR V. SVADKOVSKI and ANATOLY P. DOSTANKO Belarusian State University of Informatics and Radioelectronics, Modem Electronics Technologies Department, Minsk 220027, Belarus ABSTRACT Two types of the ion sources for ion beam assisted deposition using inert gases, oxygen or nitrogen are reported. Their design and operational features are presented. Each of them has the properties of two existing main types of the gridless Hall sources: an end-Hall source and the anode-layer version a closed-drift ion source. Basic distinction of the developed sources is the extended range of ion energies in high-current beam for optimization of deposition, cleaning and etching processes. INTRODUCTION Of the many gridless acceleration concepts investigated, the Hall current ion sources are the most promising for high-current, low-energy ion beam assisted deposition (IBAD) application. Therefore, ease of maintenance and generally higher ruggedness in comparison with gridded ion sources make the Hall current ion sources more suitable for industrial application. There are several types of the Hall current ion sources. One of them is an end-Hall type [1,2], in which the ion-acceleration channel is circular. This ion source type emits high ion currents in a broad beam, but with limited energy in the range of 100 eV. It should be applicable for low energy IBAD. However, when a surface layer is to be removed to achieve a clean condition, higher ion energies of several hundred eV are generally needed to increase adhesion of the film [3]. Also there are other cases when an extended range of ion energies is needed, for example for optimization of etching, dual ion beam deposition
and others [4,51. Drawbacks of this ion source, besides the restriction in ion energy, is the circular, rather than annular, configuration of the ion-acceleration channel. So its ion beam
profile is inflexible, which makes it difficult to use in some processes IBAD. There is also a closed-drift ion source, in which the ion-acceleration channel is annular. The
present technology of this source is due in large part to work done in the Soviet Union [6-8]. The anode-layer version of a closed-drift ion source is the most promising for the thin film
deposition application. But although there is a lack of any space-charge-flow limitation on ion current density, there are some difficulties for the creation of the anode-layer source, which has the acceptable range of ion energies (from tens to hundreds eV). There is considerable interest in developing of the ion sources to larger area substrates and the extention of range of ion energies in high-current beams. PRINCIPLES OF ION ACCELERATION MECHANISMS Analytical investigation of the mechanisms of ion acceleration for the main types of the Hall current ion sources has been done by Kaufman in the papers [1,9]. There are two major mechanisms by which a potential difference to accelerate the ions is generated in a magnetic field. The first of these mechanisms is the reduced plasma conductivity across magnet
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