Process performance for Virtual Slot Disk/Triple Surface Disk Faraday on a multi-wafer high current ion implantation system

The process performance of a reduced area disk with a variable strike plate faraday to control cross contamination and auto-doping in multi-wafer high current ion implanters is reported. The Virtual Slot Disk (VSD)/Triple Surface Disk Faraday (TSDF) hardware combination is designed to significantly reduce surface cross contamination, while maintaining real-time dose control. The VSD reduces the surface area of the disk from which to sputter contaminants, and the TSDF dedicates strike surfaces for specific implant species to eliminate potential surface cross contamination from the faraday. Using this configuration, cross contamination of phosphorus in arsenic implants was reduced by over a factor of three compared to a solid disk assembly. A description of the basic system configuration along with the results of the process qualification is presented here. The process qualification focused on surface cross contamination, transition metals and aluminum contamination, and dosimetry performance, as measured by R_s. In addition, other items were checked (functionality, wafer cooling, charging) to ensure compliance with product specifications. A specific study of surface cross contamination during heavy phosphorus operation was done to investigate the need for dedicated tools sensitive to this type of contamination.