Reduction of particle contamination in an actual plasma etching process

To reduce particle contamination in plasma etching equipment, a strategy to control particles' behavior were developed. The methods include the following techniques: a non-plasma particle cleaning (NPPC) with an in situ particle monitor (ISPM), a pre-purge gas sequence, a control of cross over pressure and a chucking voltage application during plasma discharge. Before the application of these methods, 12 particles in average and 52 particles at maximum were detected on a 300 mm wafer during the RF time of 220 hours. The particle level was decreased to less than 1 particle in average and 4 particles at maximum after the application of these measures without any modification of the chamber hardware and process recipe. From a trend of the ISPM counts during NPPC, a spike of ISPM count was observed. This spike suggests that there are some problems in the chamber at this time. After 85 times of NPPC, the spikes of ISPM count were observed repeatedly. These spikes are thought to mean that the chamber becomes dirty. A slightly high particle level is detected just after chamber maintenance. The major part of particles, which are larger than 1 micron, consists of carbon and fluorine. These particles are considered to come from the downstream of the chamber. A novel method to reduce these particles is developed and verified experimentally.