Embodiments of the invention generally provide methods for end point detection at predetermined dopant concentrations during plasma doping processes. In one embodiment, a method includes positioning a substrate within a process chamber, generating a plasma above the substrate and transmitting a light generated by the plasma through the substrate, wherein the light enters the topside and exits the backside of the substrate, and receiving the light by a sensor positioned below the substrate. The method further provides generating a signal proportional to the light received by the sensor, implanting the substrate with a dopant during a doping process, generating multiple light signals proportional to a decreasing amount of the light received by the sensor during the doping process, generating an end point signal proportional to the light received by the sensor once the substrate has a final dopant concentration, and ceasing the doping process.