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 and generating events that affect yield occur frequently and that particle levels are considerably higher when product wafers are run than when monitor wafers are run. This implies that a strategy of combined in-situ, real-time monitoring and test wafer monitoring can lead to improved particle control. The advantages of this method are that it can be applied while product wafers are run through the process tool and this it measures on a continuous rather than sampling basis. Such a method could be combined with test wafer monitoring to provide two process control measurement and hence achieve tighter control of free-particle levels. With this particle control strategy, the test wafer monitoring is used to provide best-case baselines of equipment performance which can be used to qualify equipment for production, and the in-situ sensor provides ongoing real-time particle monitoring during production