Flat Wave-Cutoff Sensor for Real-Time Industrial Plasma Process Monitoring

In this conference, a flat wave-cutoff sensor [1] - [3] , which measures the absolute electron density even in processing gas plasmas, is presented. First, we evaluated the performance of various types of flat wave-cutoff sensors and it was found that the bar-type flat wave-cutoff sensor showed best performance with clear wave-cutoff characteristics and mitigation of noise signals among the various sensor types. It was revealed that the flat wave-cutoff sensor measures the plasma density near the plasma-sheath boundary layer, which is adjacent to the chamber wall or wafer. It was also demonstrated for the first time that the real-time plasma density is measured, even though the processing wafer is placed on the sensor. The developed array-type flat wave-cutoff sensor can measure the spatial distribution of the plasma density and the measured density distribution showed the similar characteristics with the etch-rate uniformity. These results indicate that the chuck-embed or wall-type flat wave-cutoff sensor can be used in industrial plasma processing to monitor plasma and process result.