Measurements of residual defects and 1/f noise in ion-implanted p-channel MOSFET's

This paper describes the measurements of excess noise and residual defects of extremely low concentrations (<1 × 10⁹cm^-2) in ion-implanted p-channel MOSFET's. The activation energy and the density of the residual defects after high-temperature annealing were measured using a transient capacitance technique. The test FET's were ion-implanted with fluences of 5 × 10¹¹to 4 × 10¹²using³¹p⁺,¹¹B⁺, or²⁸Si⁺species. A post-implant anneal was carried out in an N2or an Ar ambient for 20 min at various temperatures. For¹¹B⁺-implanted MOSFET's after annealing above 1000°C, a high residual defect concentration was observed near the conduction band edge; whereas after annealing the defect density as a result of²⁸Si⁺or³¹p⁺implantation was equal to that of control MOSFET's. The density-of-state data agree with the equilibrium measurements of excess (1/f) noise power. The excess noise was measured as a function of the drain current. The distribution of1/fnoise power versus potential minimum of holes in the equilibrium condition is similar to that of interface state density. In nonequilibrium operation, a reduction of excess noise was achieved owing to the presence of buried channel created by ion implant.