Method for monitoring substrate biasing during plasma processing of a substrate

摘要

A processing system for processing a substrate with a plasma comprises a processing chamber configured for containing a plasma and a substrate support. Electrodes are coupled to the substrate support and an RF power source is coupled to each of the electrodes for biasing the electrodes to create a DC bias on a substrate positioned on the supporting surface. A first comparator having first and second inputs is electrically coupled to one of the electrodes with an isolating device being coupled between the first and second inputs to isolate the first input from the bias on the one electrode. The comparator has an output reflective of a voltage difference between the first and second inputs. A second comparator has a first input coupled to the first electrode and a second input coupled to the second electrode, and has an output reflective of a voltage difference between the first and second inputs resulting from the bias difference between the first and second electrodes.