Patent ID: 6596550
Filing Date: 2003-07-22
Classification: H01J

Abstract:
A method of processing the substrate with a plasma comprising:positioning a substrate on a supporting surface of a substrate support within a processing chamber; forming the plasma in the processing chamber proximate the substrate; providing first and second electrodes coupled to the substrate support, the electrodes each being positioned proximate the supporting surface and being electrically isolated from one another; biasing the electrodes with an RF power source for creating a DC bias on the substrate; electrically coupling first and second inputs of a first comparator to one of the electrodes to measure the DC bias of the electrode and coupling an isolating device between the first and second inputs for isolating the first input from the DC bias on the one electrode; monitoring an output of the first comparator to determine the voltage difference between the first and second inputs reflective of the electrode bias created on the one electrode by the RF power source; electrically coupling a first input of a second comparator to the first electrode and a second input of the second comparator to the second electrode; monitoring an output of the second comparator to determine a voltage difference between the first and second inputs of the second comparator reflective of the electrode DC bias created on the first and second electrodes by the RF power source; and determining the DC bias of the first and second electrodes based upon the output of the first and second comparators; wherein a relative bias of the first and second electrodes is monitored so that the bias is optimally adjusted.