Sensor fault detection in etch based on broadband rf signal observation

To minimize machine downtime in semiconductor plasma etching processes, a sensor, fault detection system was developed, employing a broadband rf sensor. The work presented here focuses on detecting errors in the transformer coupled power (TCP) measurement and pressure sensor, though the method has potential for several other sensors. To improve the detection sensitivity, we used real-time machine input estimation, and compared it against actual recipe settings instead of employing - the raw rf signals directly. For a main etch process on a Lam TCP 9400SE, +/- 10% relative deviations in TCP measurement, or +/- 25% in pressure, can be detected with high accuracy: Detection probability P-D approximate to 1 and false alarm rate P-F approximate to 0 for both. (C) 2003 American Vacuum Society.