ELECTROSTATIC SCATTERING OF IONIC SPECIES IN LOW-PRESSURE SPUTTERING OF TI AND TIN

A technique of sputtering with low pressures and large substrate to ta rget distances (long throw) has been studied with a view of applying t he technique to the deposition of titanium and titanium nitride on hig h aspect ratio topographies. The angular distributions of the sputtere d species produced by most sputtering systems are broad and therefore unsuitable for application to via filling in ultralarge scale integrat ion or even to lift-off patterning in very-large scale integration. In our work, progressive reduction in the pressure to 0.013 Pa (0.1 m To rr) while reducing the size of the planar magnetron (to 50 mm diam), w as made possible by injecting electrons and ionized Ar by means of a s econdary hollow cathode source. These reductions in pressure and magne tron size have greatly narrowed the incident angular distribution of t he sputtered species at the substrate. However, we believe that a comp onent of the sputtered species is electrostatically scattered near the substrate. This is important because many of the applications of sput tering at low pressures will involve insulating substrate structures t hat are expected to be particularly susceptible to this effect (for in stance lift-off deposition on, or via filling in, insulators). In addi tion, we believe that our findings will be applicable to several relat ed deposition techniques of current interest in the literature such as electron cyclotron resonance, ionized sputtering (i.e., ionizing the sputtered flux and directing it towards the substrate) and conventiona l magnetron sputtering. (C) 1996 American Vacuum Society.