Method for controlling cyclic plasma-assisted process

A method for processing a substrate in a reactor by pulsing RF power, comprising:

• applying RF power in pulses in the reactor to process the substrate;
• monitoring data from the reactor indicative of anomalous pulses of RF power, including data from a photo sensor equipped in the reactor, wherein the data monitored include values of RF forward power, RF reflected power, self-bias voltage (Vdc), and/or peak-to-peak voltage (Vpp) measured at a matching box of a RF generator of the reactor, and plasma luminescence measured by the photo sensor;
• counting the number of anomalous pulses of RF power in the monitored data, wherein the counting of the number of anomalous pulses of RF power includes counting:
• the number of pulses of RF power whose RF forward power is lower than a threshold, the number of pulses of RF power whose RF forward power is higher than a threshold, the number of pulses of RF power whose RF reflected power is higher than a threshold, the number of pulses of RF power whose Vdc is higher than a threshold, and/or the number of pulses of RF power whose Vdc is lower than a threshold, and
• the number of pulses of RF power whose plasma luminescence is lower than a threshold, and the number of pulses of RF power whose plasma luminescence is higher than a threshold;
• determining whether or not the number of anomalous pulses of RF power is acceptable;
• and
• initiating a pre-designated sequence if the number of anomalous pulses of RF power is determined to be unacceptable.