A comparison of the characteristics of planar and cylindrical magnetrons operating in pulsed DC and AC modes

The deposition of functional films onto both polymeric web and large area glass substrates has been a major area of growth in recent years. The key to this growth has been the development of the mid-frequency (20–350 kHz) dual bipolar pulsed magnetron sputtering process, which now permits complex, multi-layer structures with specific properties to be routinely deposited in high throughput systems. There are, though, several competing variants of the dual bipolar process currently employed, with each variant imposing its own set of criteria in terms of cost, process stability, throughput and product performance. Commercially available coating systems utilise both planar and cylindrical rotatable magnetrons, driven by AC, or pulsed DC power supplies. Few direct comparisons, though, have been made of these alternative approaches. Consequently, selection of equipment and operating procedures are being made largely on an empirical basis, potentially leading to non-optimal deposition conditions, or reduced film functionality. s study, therefore, titania and silica coatings have been deposited by reactive magnetron sputtering onto glass substrates in both magnetron configurations and power delivery modes. Film structures have been analysed by SEM and the operating characteristics of the competing technologies have also been studied in terms of deposition rates, hysteresis behaviour and thermal flux at the substrate. The results to date of this study are reported here.