Advanced OES characterization

A plasma processing system comprising:

• a plasma processing chamber configured to hold a substrate to be processed;
• an RF power source configured to generate a first plasma in the plasma processing chamber;
• a first vacuum pump;
• an exhaust gas line connecting the plasma processing chamber and the first vacuum pump;
• a plasma power supply configured to generate a second plasma from a portion of an exhaust gas downstream from the plasma processing chamber;
• and
• an optical emission spectroscopy (OES) measurement assembly comprising:
• an OES detector configured to measure first OES signals from the first plasma and second OES signals from the second plasma;
• a microprocessor;
• and
• a non-transitory memory storing a program to be executed in the microprocessor, the program comprising instructions to:
• perform a plasma process on the substrate;
• control the plasma power supply to apply a base source power to sustain the second plasma and to apply a series of power spikes to the second plasma, the series of power spikes synchronized with detection of the second OES signals by the OES detector;
• during the plasma process, record the first OES signals or the second OES signals associated with a chemical composition of the first plasma or the second plasma;
• and
• based on the first OES signals or the second OES signals, estimate a temporal change of the chemical composition to evaluate a progress of the plasma process.

A processing system comprising:

• a plasma processing chamber configured to hold a substrate to be processed;
• an RF power source;
• a first vacuum pump;
• an exhaust gas line connecting the plasma processing chamber and the first vacuum pump;
• an exhaust OES chamber connected to the exhaust gas line;
• a plasma power supply coupled to the exhaust OES chamber;
• an optical emission spectroscopy (OES) detector;
• a microprocessor;
• and
• a non-transitory memory storing a program to be executed in the microprocessor, the program comprising instructions to:
• control the plasma power supply to:
• apply a base source power to an electrode or coil connected to the exhaust OES chamber to generate an exhaust plasma in the exhaust OES chamber;
• and
• after generating the exhaust plasma, apply a series of power spikes to the electrode or coil;
• measure exhaust OES signals from the exhaust plasma, wherein a timing of detecting the exhaust OES signals is correlated with the series of power spikes;
• measure electrical parameters of the exhaust plasma;
• and
• perform an endpoint detection (EPD) process based on the measured electrical parameters and the exhaust OES signals.