Ion beam induced deposition of tungsten on silicon

An investigation into the growth of tungsten films by ion beam induced deposition is described. This technique involves the use of an ion beam to dissociate organometallic precursor molecules adsorbed at the substrate surface, resulting in the growth of thin metallic films at the beam-adsorbate interface. For this study a dedicated ion beam induced deposition chamber has been attached to the target end of a standard Lintott series I isotope separator. Using a tungsten hexacarbonyl precursor, directed from a nozzle, successful depositions of thin tungsten films on silicon substrates have been conducted using the inert ion species Ne, Ar, Kr and Xe. Precursor temperature has been shown to have a significant bearing on deposition rate and a minimum temperature of 65°C is required to ensure sufficient precursor flux for deposition. The deposited film thickness was found to increase with increasing ion dose. Using RBS analysis the deposited films were shown to consist of over 80% W. The principle impurities were identified as the implanted ion species and residual carbon. It was noted however that film composition varied in relation to the nozzle-substrate geometry. Four point probe measurements indicated resistivity values of the order of that of bulk tungsten