Sheet resistance measurement for ultra-high energy ion implantation

Ion implanters require high energy to improve the light sensitivity of advanced image sensors with deep photodiode structures. Although ion enable implantation, conditions near wafer surface may differ from those in shallow implantation. As implantation increases, dopant ions are implanted deeper into wafer. Consequently, conventional four-point probe tools inappropriate for measuring electrical sheet resistance an alternative, a sacrificial oxide layer is applied and then removed after which allows such wafers.