Ion Beam Assisted Deposition of Metal Films
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ION BEAM ASSISTED DEPOSITION OF METAL FILMS Kenji Gamo and Susumu Namba Faculty of Engineering Science, and Research Center for Extreme Materials, Osaka University, Toyonaka, Osaka 560, Japan ABSTRACT The characteristics of ion beam assisted deposition are discussed and compared with those of photon beam assisted deposition. Effects of various deposition parameters including ion species, beam energy and substrate temperature are discussed. Deposited films usually include impurities such as C and 0. Inclusion of oxygen takes place by enhanced oxidation by background oxygen and may be reduced by depositing in a clean vacuum. Promising applications of maskless ion beam assisted deposition are also discussed. INTRODUCTION Maskless processing using directed beams is increasingly important for electronic device processing. With the increasing scale of integration, complexity of device processing increases. Maskless processing is important to reduce the complexity by direct fabrication of device patterns without using lithography steps. Focused ion beam technology is a new fabrication technology for future device fabrication processing. It has many promising capabilities; First, it has very high resolution. Delineation of 30nm patterns has been demonstrated[I]. Second, it has a very high current density of >IA/cm with a submicron beam spot size. The current density is 103-106 times larger than for conventional ion beam systems. Third, it has a capability of maskless fabrication for doping, etching and deposition. The current intensity of the present focused ion beam (FIB) systems is only a few nA at the most, though an increase may be possible by improving the beam optics using various techniques including variable shaped beam techniques[2]. The low current intensity limits the practical applications of focused ion beams. Nevertheless, high current density and high resolution of FIB provides unique applications as, for example, mask repair and circuit diagnosis tools[3-5]. X-ray masks, for example, are fabricated using very fragile thin(several micronmeter thick) membrane. For such membrane mask, it is not easy to repair transparent or opaque defects using conventional techniques. For FIB, transparent defects are repaired by depositing heavy metals such as W, Ta or Au using the ion beam assisted deposition technique and opaque defects can be repaired by sputter etching without using lithography process. Circuit trimming can be done similarly, by cutting metal lines by sputter etching or connecting lines by metal deposition. In the present paper, characteristics of metal film deposition using focused ion beams and some applications are discussed. EXPERIMENTAL PROCEDURES Mat. Res. Soc. Symp. Proc. Vol. 131. t1989 Materials Research Society
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Energetic ion beam irradiation induces various kinds of chemical effects in target materials. Adsorbed molecules and substrate atoms may be excited or decomposed by electronic and nuclear collisions. This phenomena has useful applications to maskless ion beam assisted etching techn
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