Defect spatial distributions in annealed ion-implanted silicon measured by a transient capacitance technique

Abstract

Defect spatial distributions of extremely low concentration were measured, for the first time, by a transient capacitance technique in ion‐implanted MOSFET’s. Aluminum gate FET’s were ion implanted through the gate oxide with 1×10¹² of ²⁸Si⁺ ions/cm² at 310 keV. The devices were annealed at 650 °C before Al was put down. Energy levels for the residual defects after annealing were obtained at E_c−0.29, E_c−0.45, E_c−0.54, and E_v+0.52 eV, respectively. Then the in‐depth distribution for each level was measured to a concentration of 10¹²/cm³ by varying the gate voltage. The profile of defect distribution shows that the annealing after low‐dose implantation differs from the regrowth of the amorphous layer caused by heavy implantation and that most of the residual defects remain in the bulk rather than at the interface.