The industrial application of pulsed DC bias power supplies in closed field unbalanced magnetron sputter ion plating

The advantages of using pulsed DC power supplies in the reactive magnetron deposition of dielectric coatings from conductive or partially conductive sputtering targets are well recognised, particularly in terms of the elimination of arcing and enhanced process stability. Less attention has been paid, however, to the application of pulsed DC power to the biasing of substrates in ion plating processes. This paper draws on our seven years of practical experience of using a range of pulsed DC bias supplies in a wide variety of industrial coating equipment exploiting closed field unbalanced magnetron sputtering technology. The selection of pulsed plasma characteristics for surface cleaning, interface formation and the coating of components is investigated, including parameters such as voltage, frequency, pulse width and pressure. The effectiveness of such pre-cleaning is evaluated, for example, by the subsequent scratch adhesion testing of the coatings. The synergistic interaction of the bias with DC and pulsed DC closed field magnetron sources is explored. The additional process flexibility provided by the pulsed bias technique can facilitate the processing of thermally sensitive materials and the preservation of critical surface characteristics.