PULSED MAGNETRON SPUTTER TECHNOLOGY

At present, a new development trend is becoming evident in which the introduction of a pulsed mode for magnetron sputtering seems to be very promising with respect to process stability and layer quality. For instance, the deposition of TiN requires a plasma density that cannot be attained in normal operation. Here the pulsed mode allows a higher plasma density to be obtained without exceeding the thermal rating of the substrate. In this way, for example, it has been possible to attain bias currents up to 10 mA cm-2. By using several pulse-controlled small magnetron sources in an array, the alloy composition or film thickness distribution can be adjusted by electronic means. The ever-growing demand for sandwich structures and gradient layers opens new applications for pulsed sputter technology. The reactive deposition of highly insulating layers, eg. SiO2, TiO2 and Al2O3, has turned out to be rather unsatisfactory up to now. Randomly grown insulating layers on target, anode and plasma-confining electrodes prevent a stable operation. The disturbing effects caused by drifting potential distributions and arcing can be restricted by introducing the pulsed mode in the medium frequency range. With Al2O3, for example, defect densities due to arcing were reduced by three to four orders of magnitude. At rates of 240 nm min-1, the coating operation could be maintained for many hours. A review is given on the present state of activities in the field of pulsed magnetron sputtering. Based on practical examples, the capabilities inherent in this technique are discussed and further development trends derived. In our opinion, pulsed magnetron sputter technology is an innovation of great practical significance.