Model based investigation of Ar+ ion damage in DC magnetron sputtering

Magnetron discharges in a sputter coater for Ag backside mirrors on LED devices have been simulated via Particle-in-Cell Monte Carlo (PIC-MC). The primary goal was the investigation of experimentally observed device damage apparently due to high energy Ar+ ion bombardment in the subsequent sputtering process. The PIC-MC simulation provided, among others, time integrated ion energy distribution function (IEDF) associated with the surfaces in the simulation domain. A high energy tail in the substrate's IEDF could be related to the measured degree of damage at corresponding process conditions. Further investigation revealed that the IEDFs' high energy tail correlates with the extent of plasma fluctuations seen at certain process conditions. Several experimental studies in recent years have broached the issue of such plasma fluctuations in magnetron discharges. However, PIC-MC simulation data could provide more detailed insights into cause and effect of this inherent discharge anomaly. Thus, it could be instructively revealed how electric field enhancements accompanying these fluctuations affect the IEDF and generation of high energy ions, respectively.