CHARACTERIZATION STUDIES OF THE STRUCTURE OF AL, ZR, AND W COATINGS DEPOSITED BY CLOSED-FIELD UNBALANCED MAGNETRON SPUTTERING

Closed-field unbalanced magnetron sputtering (CFUBMS) is now establish ed as a versatile technique for the high-rate deposition of high-quali ty metal, alloy and ceramic coatings. BNFL have identified CFUBMS as h aving the potential to be used on an industrial scale for the producti on of coated components with properties relevant to their needs. As su ch, 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 for mation 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 10 0 to 600 degrees 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 experi mental arrays for each metal. The coating structures were examined usi ng the SEM. In all cases, dense structures with good coating-to-substr ate adhesion were obtained. In addition, the factors influencing depos ition rate, ion current density and ion:atom ratio were examined. A nu mber of trends in these data have been identified using Taguchi analys is techniques. This information has been used to develop a preliminary structure zone model relating to the CFUBMS technique. (C) 1997 Elsev ier Science S.A.