A method, including using an implant recipe to perform an implant by scanning an ion beam along a first axis over a substrate, coated with a photoresist layer, while the substrate is scanned along a perpendicular axis; measuring an implant current (I) during the implant, using a first detector, positioned to a side of a substrate position; determining a value of a difference ratio (I−B)/(B), based upon the implant current, where B is current measured by the first detector, during a calibration at base pressure; determining a plurality of values of a current ratio (CR) for the plurality of instances, based upon the difference ratio, the current ratio being a ratio of the implant current to a current measured by a second detector, positioned over the substrate position, during the calibration; and adjusting scanning the ion beam, scanning of the substrate, or a combination thereof, based upon the current ratio.