Characterization studies of the structure of Al, Zr, and W coatings deposited by closed-field unbalanced magnetron sputtering

Abstract

Abstract Closed-field unbalanced magnetron sputtering (CFUBMS) is now established as a versatile technique for the high-rate deposition of high-quality metal, alloy and ceramic coatings. BNFL have identified CFUBMS as having the potential to be used on an industrial scale for the production of coated components with properties relevant to their needs. As such, they have initiated a major research project with the aim of fully characterizing the CFUBMS system. The work reported here forms a part of this project. A key factor in the CFUBMS system is the ability to transport high ion currents to the substrate. This can enhance the formation of fully dense coatings at relatively low values of homologous temperature. To study this system in more detail, an investigation has been carried out to determine the influence of a number of deposition parameters on the structure of Al, Zr, and W coatings. The deposition parameters investigated were substrate temperature (over the range 100 to 600 °C), target current (7–27 mA cm −2 ), substrate bias (−30 to −300 V), coating pressure (0.5–3 mtorr) and target-to-substrate separation (80–150 mm). The Taguchi method was used to develop experimental arrays for each metal. The coating structures were examined using the SEM. In all cases, dense structures with good coating-to-substrate adhesion were obtained. In addition, the factors influencing deposition rate, ion current density and ion:atom ratio were examined. A number of trends in these data have been identified using Taguchi analysis techniques. This information has been used to develop a preliminary structure zone model relating to the CFUBMS technique.