Radio frequency sensor calibration by virtual metrology

An apparatus, comprising:

• a controller including a processor that is programmed to:
• providing a first virtual metrology (VM) model that is configured to predict a first thickness change rate (TCR) for executing a plasma recipe in a first chamber, and a second VM model that is configured to predict a second TCR for executing the plasma recipe in a second chamber, wherein the plasma recipe comprises one or more inert gases and no reactive gases;
• providing a control model that describes relationships between voltage, current and recipe parameters;
• calibrating, in reference to a first voltage in the first chamber measured by a first radio frequency (RF) sensor, a second voltage in the second chamber measured by a second RF sensor, using a golden reference sensor;
• and
• calibrating, in reference to a first current in the first chamber measured by the first RF sensor, a second current in the second chamber measured by the second RF sensor, using the first TCR, the second TCR, the first VM model, the second VM model and the control model.