Benefits of real-time, in situ particle monitoring in production medium current implantation

Real-time free particle measurements in the loadlocks of a production medium current implanter have been conducted. These measurements correlate to both surface scans and electrical test yield. They suggest that episodic particle generating events that impact yield occur frequently and that particle levels are considerably higher when product wafers are run than when monitor wafers are run. The data correlate to monitor wafer surface counts, allowing the real-time monitor to be used in equipment requalification. The data also provide a real-time plot of machine utilization and performance and can be useful in identifying variations in both the implant process and feeder processes. It is concluded that a strategy of in situ, real-time sampling combined with test wafer monitoring can lead to improved particle control