A method of manufacturing a semiconductor device including calibrating an ion implant process. The calibration includes forming a dielectric layer over a calibration substrate. A dopant is implanted into the dielectric layer. Charge is deposited on a surface of the dielectric layer, and voltage on the surface is measured. An electrical characteristic of the dielectric layer is determined, and a doping level of the dielectric layer is determined from the electrical characteristic. The electrical characteristic is associated with an operating set-point of the ion implant process. The calibrated ion implant process is used to implant the dopant into a semiconductor substrate.