Implementation of an in-situ particle monitor system on an oxide plasma process system

The implementation of an in-situ particle monitor (ISPM) on a high volume manufacturing oxide plasma etcher is discussed. Plasma process generated particles have been traditionally monitored using the Particle per Wafer Pass (PWP) methodology, using test wafers and a particle inspection system. As equipment throughputs continue to increase, more PWP test wafer runs are needed to maintain a quick response to sudden high particle events. Increasing the number of test wafer runs not only increases test wafer cost, but also reduces equipment availability and increases cost of ownership. The ISPM allows real-time response to high particle events, better understanding of equipment and process particulate status, reduced defectivity, increased tool availability, and reduced cost of ownership. An oxide plasma etching system was used in this investigation to collect a large data base of ISPM data. Strong correlation was established between regular PWP and ISPM data during RF-plasma on events. The ISPM was also demonstrated to provide valuable insights into the particle deposition mechanism. The initial particle counts were found to stay constant over a long duration of the equipment run time. However, when the PWP count started to increase, the ISPM signal increased sharply. Moreover, the frequency of high particle counts was observed to increase as the equipment run time increased. Finally, a process comparison based on the ISPM is discussed. Based on the correlation to PWP methodology, the increased data collection capability and potential reduction in cost of ownership, the ISPM has been implemented in the manufacturing line.