High power pulsed magnetron sputtering (HPPMS): Promise progress, challanges and outlook

The high power pulsed magnetron sputtering (HPPMS) approach to thin film deposition has significant promise for deposition of a new generation of coatings important both scientifically and commercially. HPPMS allows for a high fraction of ionized target material at the workpiece and thus for growth conditons similar to pulsed laser deposition and filtered deposition. A pulsed supply with arc handling capability has been developed and used for experimental thin film depositions. Arc handling is required for HPPMS deposition of materials prone to arcing, such as corbon, and also for transition mode reactive deposition of insulating materials such as TiOx. Reported HPPMS rates are typically only 25% to 35% of the DC rates at the same average power when the process parameters are equal. So far, the reported ionized fraction of target material arriving at the workpiece ranges from 5% to 70%. Optical emission spectroscopy suggests highly metallic plasma, but even so, the fraction of ionized target material arriving at the workpiece can be low. A simple pathways model has been developed to explain these experimental results. In addition, parametric evaluation of the model suggests target material characteristics which are desirable in order to achieve higher deposition rates and a greater ionized fraction of target materials reaching the substrate. Model predictions have been correlated to experimentals results for HPPMS silver depositon for a range of peak powers. Development of commercially viable HPPMS processes will likely require development from a multi-disciplinary approach by experts in thin films, analysis of thin films, plasma and plasma analysis, measurement, and modeling techniques, and thin film deposition technology. The motivation for HPPMS and key results to date will be reviewed and challenges and outlook for development of commercial HPPMS processes will be discussed