Abstract: A substrate processing system to remove residual halogen species from a substrate includes a processing chamber and a substrate support arranged in the processing chamber to support a substrate. The substrate includes residual halogen species. A heater heats the substrate to a temperature in a predetermined temperature range from 100° C. to 700° C. during a processing period. A chamber pressure controller controls pressure inside the processing chamber in a predetermined pressure range greater than 10 Torr and less than 800 Torr during the processing period. A vapor generator supplies water vapor at least one of in the processing chamber or to the processing chamber during the processing period.