Relationships between residual defects and excess noise in ion-implanted MOSFETs

This paper describes the relationship between excess noise and residual defects of extremely low concentration (<1 × 10⁹cm^-2)in ion-implanted MOSFETS. The excess (1/f) noise was measured as a function of the drain current. The activation energy and the density of the residual defects after high temperature annealing was measured using a transient capacitance technique. Test FETs were ion-implanted with a fluence of 5 × 10¹¹∼ 4 × 10¹²using³¹p⁺,¹¹B⁺, or²⁸Si⁺species. Post implant anneal was carried out in N2ambient for 20 minutes at various temperatures. For¹¹B⁺-implanted MOSFETs a high residual defect concentration after annealing above 920° was observed near the band edges whereas the density of defects as a result of²⁸Si⁺or³¹p⁺implantation after annealing was equal to that of control MOSFETs.